JP6464935B2 - Switching power supply - Google Patents

Description

  The present invention relates to a switching power supply device that performs voltage conversion using a switching element.

  Various DC-DC converters have been proposed as an example of a switching power supply and are put into practical use (for example, Patent Documents 1 and 2). This type of DC-DC converter generally includes an inverter circuit including a switching element, a power conversion transformer (transformer element), and a rectifying and smoothing circuit.

US Patent Application Publication No. 2009/0196072 U.S. Pat. No. 8,780,585

  Incidentally, in such a switching power supply device such as a DC-DC converter, it is generally desired to improve power conversion efficiency.

  The present invention has been made in view of such problems, and an object thereof is to provide a switching power supply device capable of easily improving power conversion efficiency.

The switching power supply device according to the present invention includes N (N: 2) terminals each having an input terminal pair to which an input voltage is input, an output terminal pair to which an output voltage is output, a primary winding and a secondary winding. (An integer above), N inverter circuits arranged in parallel with each other between the input terminal pair and the primary winding, each including a switching element, an output terminal pair, and a secondary side A rectifying / smoothing circuit which is arranged between the windings and includes {2 × (N + 1)} rectifying elements, a choke coil, and a capacitive element arranged between the output terminal pairs; And a driving unit that performs switching driving for controlling the operation of the switching elements in the N inverter circuits. In the rectifying / smoothing circuit, (N + 1) arms each having two rectifying elements arranged in series in the same direction are arranged in parallel between the output terminals. The secondary windings of the N transformers are individually H-bridge connected between adjacent arms of the (N + 1) arms. A choke coil is disposed between the (N + 1) arms and the capacitive element. In addition, the drive unit operates with a phase difference between the N inverter circuits, and in each of the N inverter circuits, the length of the on-duty period of the switching element is substantially the maximum value. By performing switching driving, the off-duty period of the switching element is limited to only a dead time period for avoiding an electrical short circuit due to the ON state of the plurality of switching elements between the input terminal pairs.

  According to the switching power supply device of the present invention, it is possible to easily improve the power conversion efficiency.

1 is a circuit diagram illustrating a schematic configuration example of a switching power supply device according to an embodiment of the present invention. FIG. 2 is a timing waveform diagram illustrating an operation example of the switching power supply device illustrated in FIG. 1. FIG. 2 is a circuit diagram illustrating an operation state example of the switching power supply device illustrated in FIG. 1. FIG. 4 is a circuit diagram illustrating an operation state example subsequent to FIG. 3. FIG. 5 is a circuit diagram illustrating an operation state example subsequent to FIG. 4. FIG. 6 is a circuit diagram illustrating an example of an operation state following FIG. 5. FIG. 7 is a circuit diagram illustrating an operation state example subsequent to FIG. 6. FIG. 8 is a circuit diagram illustrating an operation state example subsequent to FIG. 7. FIG. 9 is a circuit diagram illustrating an operation state example subsequent to FIG. 8. FIG. 10 is a circuit diagram illustrating an operation state example subsequent to FIG. 9. FIG. 11 is a circuit diagram illustrating an example of an operation state following FIG. 10. It is a circuit diagram for demonstrating the operation state in the rectification smoothing circuit shown in FIG. 10 is a circuit diagram illustrating a schematic configuration example of a switching power supply device according to Modification 1. FIG. It is a circuit diagram for demonstrating the operation state in the rectification smoothing circuit shown in FIG. 10 is a schematic diagram illustrating a circuit configuration example and an operation example of a switching power supply device according to Modification Example 2. FIG. 10 is a circuit diagram illustrating a schematic configuration example of a switching power supply device according to Modification 3. FIG. FIG. 17 is a timing waveform diagram illustrating an operation example of the switching power supply device illustrated in FIG. 16. 10 is a circuit diagram illustrating a schematic configuration example of a switching power supply device according to Modification 4. FIG. 10 is a circuit diagram illustrating a schematic configuration example of a switching power supply device according to Modification Example 5. FIG. 10 is a circuit diagram illustrating a configuration example of a rectifying / smoothing circuit according to Modification 6. FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The description will be given in the following order.
1. Embodiment (example in which each inverter circuit is a half-bridge circuit)
2. Modified example Modified example 1 (example in which three inverter circuits and three transformers are provided)
Modification 2 (example in which four inverter circuits and four transformers are provided)
Modification 3 (example when each inverter circuit is a full bridge circuit)
Modification 4 (example in which a capacitive element for preventing partial excitation is provided in the inverter circuit)
Modification 5 (example in which a rectifying element for reverse voltage clamping is provided in the inverter circuit)
Modification 6 (Another configuration example of the choke coil in the rectifying and smoothing circuit)
3. Other variations

<1. Embodiment>
[Constitution]
FIG. 1 is a circuit diagram showing a schematic configuration example of a switching power supply device (switching power supply device 1) according to an embodiment of the present invention. This switching power supply device 1 converts a DC input voltage Vin supplied from a battery 10 (first battery) into a DC output voltage Vout, and supplies it to a second battery (not shown) to drive a load 7. -Functions as a DC converter. Here, the mode of voltage conversion in the switching power supply device 1 may be either up-conversion (step-up) or down-conversion (step-down). The DC input voltage Vin corresponds to a specific example of “input voltage” in the present invention, and the DC output voltage Vout corresponds to a specific example of “output voltage” in the present invention.

  The switching power supply 1 includes two input terminals T1 and T2, two output terminals T3 and T4, an input smoothing capacitor Cin, two inverter circuits 21 and 22, two transformers 31 and 32, and a rectifying and smoothing circuit. 4 and a drive circuit 5 are provided. A DC input voltage Vin is input between the input terminals T1 and T2, and a DC output voltage Vout is output from between the output terminals T3 and T4. The input terminals T1 and T2 correspond to a specific example of “input terminal pair” in the present invention, and the output terminals T3 and T4 correspond to a specific example of “output terminal pair” in the present invention.

  The input smoothing capacitor Cin is disposed between the primary high-voltage line L1H connected to the input terminal T1 and the primary low-voltage line L1L connected to the input terminal T2. Specifically, a first end of the input smoothing capacitor Cin is connected to the primary high-voltage line L1H at a position between two inverter circuits 21 and 22 described later and the input terminals T1 and T2, and input smoothing is performed. A second end of the capacitor Cin is connected to the primary side low-voltage line L1L. The input smoothing capacitor Cin is a capacitor for smoothing the DC input voltage Vin input from the input terminals T1 and T2. In the circuit configuration example shown in FIG. 1, since two capacitors C51 and C52 in inverter circuits 21 and 22, which will be described later, also function as input smoothing capacitors, do not provide this input smoothing capacitor Cin. Also good.

(Inverter circuits 21, 22)
The inverter circuits 21 and 22 are arranged in parallel with each other between the input terminals T1 and T2 and primary windings 311 and 321 in transformers 31 and 32 described later. Each of these inverter circuits 21 and 22 is constituted by a half bridge circuit including two switching elements.

  Specifically, the inverter circuit 21 includes two switching elements S1 and S2, capacitors C1 and C2 and diodes D1 and D2 connected in parallel to the switching elements S1 and S2, and two capacitors C51 and C52, respectively. And have. The inverter circuit 22 includes two switching elements S3 and S4, capacitors C3 and C4 and diodes D3 and D4 connected in parallel to the switching elements S3 and S4, two capacitors C51 and C52, and resonance. And an inductor Lr. That is, the capacitors C51 and C52 are elements shared by the inverter circuits 21 and 22, respectively. In addition, as for the diodes D1-D4, the cathode is arrange | positioned at the primary side high voltage line L1H side, and the anode is arrange | positioned at the primary side low voltage line L1L side, and it is a reverse direction connection state.

  In the inverter circuit 21, the first ends of the switching elements S1, S2, the first ends of the capacitors C1, C2, the anode of the diode D1, and the cathode of the diode D2 are connected to each other at the connection point P1. . The first ends of the capacitors C51 and C52 are connected to each other at the connection point P3. The second end of the switching element S1, the second end of the capacitor C1, the cathode of the diode D1, and the second end of the capacitor C51 are connected to each other at a connection point P4 on the primary high-voltage line L1H. The second end of the switching element S2, the second end of the capacitor C2, the anode of the diode D2, and the second end of the capacitor C52 are connected to each other at a connection point P5 on the primary side low-voltage line L1L. Between the connection points P1 and P3, a primary winding 311 of a transformer 31 described later is inserted and arranged. With such a configuration, the inverter circuit 21 is applied between the input terminals T1 and T2 by performing the on / off operation of the switching elements S1 and S2 in accordance with drive signals SG1 and SG2 supplied from the drive circuit 5 described later. The DC input voltage Vin is converted to an AC voltage and output to the transformer 31.

  In the inverter circuit 22, the first ends of the switching elements S3 and S4, the first ends of the capacitors C3 and C4, the anode of the diode D3, and the cathode of the diode D4 are connected to each other at the connection point P2. . The second end of the switching element S3, the second end of the capacitor C3, the cathode of the diode D3, and the second end of the capacitor C51 are connected to each other at the connection point P4. The second end of the switching element S4, the second end of the capacitor C4, the anode of the diode D4, and the second end of the capacitor C52 are connected to each other at the connection point P5. Between the connection points P3 and P2, a primary side winding 321 of a transformer 32 described later and a resonance inductor Lr are inserted and arranged in a state of being connected in series with each other. Specifically, the first end of the primary winding 321 is connected to the connection point P3, and the second end of the primary winding 321 and the first end of the resonance inductor Lr are connected to each other at the connection point P6. The second end of the resonance inductor Lr is connected to the connection point P2. With such a configuration, also in the inverter circuit 22, the switching elements S3 and S4 perform on / off operations in accordance with drive signals SG3 and SG4 supplied from the drive circuit 5 described later, whereby the DC input voltage Vin is changed to an AC voltage. The data is converted and output to the transformer 32.

  As the switching elements S1 to S4, for example, a switching element such as a field effect transistor (MOS-FET) or an insulated gate bipolar transistor (IGBT) is used. When MOS-FETs are used as the switching elements S1 to S4, the capacitors C1 to C4 and the diodes D1 to D4 can be constituted by parasitic capacitances or parasitic diodes of the MOS-FETs, respectively. Also, the capacitors C1 to C4 can be configured with junction capacitances of the diodes D1 to D4, respectively. In such a configuration, it is not necessary to provide the capacitors C1 to C4 and the diodes D1 to D4 separately from the switching elements S1 to S4, and the circuit configuration of the inverter circuits 21 and 22 can be simplified.

(Transformers 31, 32)
The transformer 31 has a primary side winding 311 and a secondary side winding 312. The primary winding 311 has a first end connected to the connection point P1 and a second end connected to the connection point P3. The secondary winding 312 has a first end connected to a connection point P7 in the rectifying / smoothing circuit 4 to be described later, and a second end connected to a connection point P8 in the rectifying / smoothing circuit 4. The transformer 31 converts the AC voltage generated by the inverter circuit 21 (AC voltage input to the transformer 31) and outputs the AC voltage from the end of the secondary winding 312. In this case, the degree of voltage conversion is determined by the turn ratio between the primary winding 311 and the secondary winding 312.

  Similarly, the transformer 32 has a primary winding 321 and a secondary winding 322. The primary winding 321 has a first end connected to the connection point P3 and a second end connected to the connection point P6. The secondary winding 322 has a first end connected to a connection point P8 in the rectifying and smoothing circuit 4 described later, and a second end connected to a connection point P9 in the rectifying and smoothing circuit 4. The transformer 32 converts the AC voltage generated by the inverter circuit 22 (AC voltage input to the transformer 32) and outputs the AC voltage from the end of the secondary winding 322. In this case, the degree of voltage conversion is also determined by the turn ratio between the primary winding 321 and the secondary winding 322.

(Rectifying and smoothing circuit 4)
The rectifying / smoothing circuit 4 is disposed between the secondary windings 312 and 322 of the transformers 31 and 32 and the output terminals T3 and T4. The rectifying / smoothing circuit 4 includes six rectifying diodes 411, 412, 421, 422, 431, and 432, one choke coil Lch, and one output smoothing capacitor Cout. The rectifier diodes 411, 412, 421, 422, 431, and 432 correspond to a specific example of “rectifier element” in the present invention, and the output smoothing capacitor Cout corresponds to a specific example of “capacitor element” in the present invention. Correspond.

  In this rectifying / smoothing circuit 4, three arms are formed by two rectifier diodes arranged in series in the same direction. Specifically, the rectifier diodes 411 and 412 form a first arm, the rectifier diodes 421 and 422 form a second arm, and the rectifier diodes 431 and 432 form a third arm. The first to third arms are arranged in parallel between the output terminals T3 and T4. Specifically, the connection point (connection point Px) between the first ends of the first to third arms is connected to the output terminal T3 via the choke coil Lch and the output line LO, and the first to third arms are connected. A connection point between the second ends of the arms is connected to a ground line LG extending from the output terminal T4.

  In the first arm, the cathodes of the rectifier diodes 411 and 412 are respectively arranged on the first end side of the first arm, and the anodes of the rectifier diodes 411 and 412 are respectively arranged on the first arm. It arrange | positions at the said 2nd end side. Specifically, the cathode of the rectifier diode 411 is connected to the connection point Px, the anode of the rectifier diode 411 and the cathode of the rectifier diode 412 are connected to each other at the connection point P7, and the anode of the rectifier diode 412 is connected to the ground line LG. Has been.

  Similarly, in the second arm, the cathodes of the rectifier diodes 421 and 422 are respectively arranged on the first end side of the second arm, and the anodes of the rectifier diodes 421 and 422 are respectively in the second arm. It is arrange | positioned at the said 2nd end side of this arm. Specifically, the cathode of the rectifier diode 421 is connected to the connection point Px, the anode of the rectifier diode 421 and the cathode of the rectifier diode 422 are connected to each other at the connection point P8, and the anode of the rectifier diode 422 is connected to the ground line LG. Has been.

  Similarly, in the third arm, the cathodes of the rectifier diodes 431 and 432 are respectively disposed on the first end side of the third arm, and the anodes of the rectifier diodes 431 and 432 are respectively provided in the third arm. It is arrange | positioned at the said 2nd end side of this arm. Specifically, the cathode of the rectifier diode 431 is connected to the connection point Px, the anode of the rectifier diode 431 and the cathode of the rectifier diode 432 are connected to each other at the connection point P9, and the anode of the rectifier diode 432 is connected to the ground line LG. Has been.

  In addition, secondary windings 312 and 322 of the transformers 31 and 32 are individually H-bridge connected between the adjacent arms of the first to third arms. Specifically, the secondary winding 312 of the transformer 31 is H-bridge connected between a first arm and a second arm that are adjacent to each other. Further, the secondary winding 322 of the transformer 32 is H-bridge connected between the second arm and the third arm adjacent to each other. More specifically, the secondary winding 312 is inserted between the connection point P7 on the first arm and the connection point P8 on the second arm, and A secondary winding 322 is inserted between the connection point P8 and the connection point P9 on the third arm.

  A choke coil Lch is disposed between the first to third arms and the output smoothing capacitor Cout. Specifically, a choke is connected between the connection point (connection point Px) of the first ends of the first to third arms and the first end of the output smoothing capacitor Cout via the output line LO. The coil Lch is inserted and arranged. The connection point between the second ends of the first to third arms is connected to the second end of the output smoothing capacitor Cout on the ground line LG.

  In the rectifying / smoothing circuit 4 having such a configuration, the AC voltage output from the transformers 31 and 32 is rectified and output in the rectifying circuit including the rectifying diodes 411, 412, 421, 422, 431, and 432. It has become. Further, in the smoothing circuit constituted by the choke coil Lch and the output smoothing capacitor Cout, the DC output voltage Vout is generated by smoothing the voltage rectified by the rectifier circuit. The DC output voltage Vout generated in this way is output from the output terminals T3 and T4 to a second battery (not shown) and supplied with power.

(Drive circuit 5)
The drive circuit 5 is a circuit that performs switching drive for controlling the operations of the switching elements S1 to S4 in the inverter circuits 21 and 22, respectively. Specifically, the drive circuit 5 supplies drive signals SG1 to SG4 to the switching elements S1 to S4, respectively, thereby controlling the on / off operation of the switching elements S1 to S4.

  Here, in the present embodiment, the drive circuit 5 performs switching drive so that the two inverter circuits 21 and 22 operate with a phase difference (a phase difference φ described later). In other words, the drive circuit 5 performs switching phase control on the switching elements S1 to S4, and stabilizes the DC output voltage Vout by appropriately setting the phase difference. At this time, the drive circuit 5 will be described in detail later. In these inverter circuits 21 and 22, for example, the length of the on-duty period of each of the switching elements S1 to S4 is substantially the maximum value (preferably the maximum value). Switching driving is performed so that The drive circuit 5 corresponds to a specific example of a “drive unit” in the present invention.

[Operation and action / effect]
(A. Basic operation)
In the switching power supply device 1, an alternating voltage is generated by switching the direct current input voltage Vin supplied from the input terminals T 1 and T 2 in the inverter circuits 21 and 22. This AC voltage is supplied to the primary windings 311 and 321 in the transformers 31 and 32. The transformers 31 and 32 transform the alternating voltage, and the transformed alternating voltage is output from the secondary windings 312 and 322.

  In the rectifying / smoothing circuit 4, the AC voltage (transformed AC voltage) output from the transformers 31 and 32 is rectified by the rectifying diodes 411, 412, 421, 422, 431, and 432, and then the choke coil Lch and the output smoothing circuit. Smoothed by the capacitor Cout. As a result, the DC output voltage Vout is output from the output terminals T3 and T4. The DC output voltage Vout is fed to a second battery (not shown) to be charged, and the load 7 is driven.

(B. Detailed operation)
Next, a detailed operation of the switching power supply device 1 will be described with reference to FIGS.

  FIG. 2 is a timing waveform diagram showing the voltage waveform or current waveform of each part in the switching power supply device 1. Specifically, FIGS. 2A and 2B show voltage waveforms of the drive signals SG1 to SG4. 2 (C) to 2 (F) show currents I311 and I321 flowing through the primary windings 311 and 321 and rectifier diodes 411, 412, 421, 422 and 431, respectively, as shown in FIG. , 432, current waveforms of currents I 411, I 412, I 421, I 422, I 431, I 432, respectively. FIG. 2G shows the voltage waveform of the voltage VPx applied between the connection point Px and the ground line LG as shown in FIG. FIG. 2H shows the current waveforms of the current ILch flowing through the choke coil Lch and the output current Iout, as shown in FIG. In addition, the direction of each voltage and each current is set to the direction indicated by the arrow in FIG.

  3 to 11 schematically show the operation states of the switching power supply device 1 at the respective timings (timing t0 to t5) shown in FIG. 2 by circuit diagrams. Note that the operation shown in FIG. 2 is an operation for one cycle including the operation at timing t0 to t5 (for the first half cycle) and the operation at timing t5 to t0 (for the second half cycle). ing.

(B-1. Operation for half cycle of first half)
First, with reference to FIG. 2 to FIG. 11, the operation for the first half cycle (timing t0 to t5) will be described.

  The drive signals SG1 to SG4 (FIGS. 2A and 2B) of the switching elements S1 to S4 are as follows. In other words, the switching elements S1 to S4 are driven with a combination and timing at which the input terminals T1 and T2 to which the DC input voltage Vin is applied are not electrically short-circuited in any state of the switching operation. Specifically, the switching elements S3 and S4 are not simultaneously turned on, and the switching elements S1 and S2 are not simultaneously turned on. The time interval taken to avoid turning them on at the same time is called "dead time". Further, the two inverter circuits 21 and 22 (switching elements S1 and S2 and swing elements S3 and S4) operate with a phase difference φ as shown in FIG. 2, for example. That is, the drive circuit 5 performs switching phase control with respect to these switching elements S1 to S4.

(Timing t0 to t1)
First, in a period before timing t0, the switching elements S2 and S3 are in the on state, and the switching elements S1 and S4 are in the off state (FIGS. 2A and 2B). Next, in a period from timing t0 to t1, first, the switching element S3 is turned off at timing t0 (FIG. 2B).

  Then, as shown in FIG. 3, loop currents Ia, Ib, Ic, and Id flow on the primary sides (inverter circuits 21 and 22) of the transformers 31 and 32, respectively. Specifically, the loop current Ia flows through the battery 10, the input terminal T2, the capacitor C52, the capacitor C51, the input terminal T1, and the battery 10 in this order. The loop current Ib flows so as to circulate through the primary side winding 311, the switching element S <b> 2, the capacitor C <b> 52 and the primary side winding 311 in this order. The loop current Ic flows through the resonance inductor Lr, the primary winding 321, the capacitor C51, the capacitor C3 and the resonance inductor Lr in this order. The loop current Id flows so as to circulate through the resonance inductor Lr, the primary winding 321, the capacitor C52, the capacitor C4, and the resonance inductor Lr in this order.

  Among these, the loop currents Ic and Id (corresponding to “circulating current” to be described later) flow due to the energy stored in the resonance inductor Lr and the leakage inductance (not shown) of the transformer 32. It flows so that the direction is maintained. In other words, the resonance inductor Lr and the leakage inductance of the transformer 32 and the capacitors C3, C4, C51, and C52 cooperate to form an LC resonance circuit and perform an LC resonance operation. Loop currents Ic and Id flow. These loop currents Ic and Id charge the capacitor C3 while discharging the capacitor C4.

  On the other hand, on the secondary side (rectifier smoothing circuit 4) of the transformers 31 and 32, as shown in FIG. 3, loop currents Ie and If and an output current Iout flow, respectively. The loop current Ie flows through the secondary winding 312, the rectifier diode 421, the choke coil Lch, the output smoothing capacitor Cout, the rectifier diode 412 and the secondary winding 312 in this order. The loop current If flows through the secondary winding 322, the rectifier diode 421, the choke coil Lch, the output smoothing capacitor Cout, the rectifier diode 432, and the secondary winding 322 in this order. The output current Iout flows so as to circulate through the output smoothing capacitor Cout, the output terminal T3, the load 7, the output terminal T4, and the output smoothing capacitor Cout in this order, thereby driving the load 7.

  Thereafter, when the voltage between both ends of the switching element S3 = Vin and the voltage between both ends of the switching element S4 reaches 0V (the potential at the connection point P2 = 0V) in the period of the timing t0 to t1, become that way.

  That is, as shown in FIG. 4, the diode D4 as the body diode becomes conductive. Therefore, instead of the loop currents Ic and Id shown in FIG. 3, a loop current Ih flowing through the diode D4 flows. Specifically, the loop current Ih flows so as to circulate through the resonance inductor Lr, the primary side winding 321, the capacitor C52, the diode D4, and the resonance inductor Lr in this order.

  At this time, on the primary side of the transformers 31 and 32, a loop current Ig as shown in FIG. 4 flows instead of the loop current Ia shown in FIG. Specifically, the loop current Ig flows so as to circulate through the battery 10, the input terminal T1, the capacitor C51, the capacitor C52, the input terminal T2, and the battery 10 in this order. On the secondary side of the transformers 31 and 32, the loop currents Ie and If and the output current Iout shown in FIG. 3 continue to flow as they are, and the load 7 is driven.

  Subsequently, after the diode D4 is turned on in this way, the switching element S4 is turned on as shown in FIG. 5 (FIG. 2B). Thereby, ZVS (zero volt switching) operation is realized, and as a result, the loss (switching loss) in the switching element S4 is reduced. At this time, as shown in FIG. 5, a loop current Ii flowing through the switching element S4 flows instead of the loop current Ih shown in FIG. The loop current Ii flows so as to circulate through the resonance inductor Lr, the primary winding 321, the capacitor C 52, the switching element S 4, and the resonance inductor Lr in this order. The time when the energy stored in the above-described resonance inductor Lr and the leakage inductance of the transformer 32 is completely released corresponds to the timing t1 in FIG.

(Timing t1 to t2)
Next, as shown in FIG. 6, during the period of timing t1 to t2, the following occurs. That is, on the primary side of the transformers 31 and 32, a loop current Ij in the direction opposite to the loop current Ii shown in FIG. 4 flows. That is, the direction of the loop current is reversed. The loop current Ij flows so as to circulate through the resonance inductor Lr, the switching element S4, the capacitor C52, the primary winding 321 and the resonance inductor Lr in this order. When such a loop current Ij flows, energy is stored (excited) in the resonance inductor Lr and the leakage inductance of the transformer 32. That is, the period of the timings t1 to t2 corresponds to an energy accumulation period (excitation period) to the resonance inductance Lr and the leakage inductance of the transformer 32.

  In addition, with the current reversal on the primary side, the loop current Ik flows on the secondary side of the transformers 31 and 32 instead of the loop current If described so far, as shown in FIG. It becomes like this. This loop current Ik circulates through the secondary winding 322, rectifier diode 431, choke coil Lch, output smoothing capacitor Cout, rectifier diode 412, secondary winding 312 and secondary winding 322 in this order. It flows like.

  Here, the current (loop current Ij) flowing through the resonance inductor Lr and the primary winding 321 is equivalent to the current flowing through the secondary winding 322 (loop current Ik). When the number of turns of the primary side winding 321 and the number of turns of the secondary side winding 322 in the transformer 32 are Np2 and Ns2, respectively, the current (= I321) flowing through the resonance inductor is (secondary side winding 322). Current)) × (Ns2 / Np2).

(Timing t2 to t3)
Subsequently, a period from timing t2 to t3 is a power transmission period from the primary side to the secondary side of the transformers 31 and 32. A period from timing t2 to timing t5 described later is a power transmission period using the transformer 32.

  In the period from the timing t2 to t3, each loop current flows as shown in FIG. That is, the loop current Ie does not flow among the loop currents shown in FIG. 6, and the loop current Ik and the output current Iout flow on the secondary side of the transformers 31 and 32.

  At this time, in the primary side winding 321 of the transformer 32, the connection point P3 side is in the “H (High)” state, and the connection point P6 side is in the “L (Low)” state, and in the secondary side winding 322, the connection point P9. The side is in the “H” state, and the connection point P8 side is in the “L” state. Therefore, a voltage | V322 | represented by (Vin / 2) × (Ns2 / Np2) is generated between both ends of the secondary winding 322.

  On the other hand, in the primary side winding 311 of the transformer 31, the connection point P3 side is in the “H” state and the connection point P1 side is in the “L” state, and in the secondary side winding 312, the connection point P8 side is in the “H” state. The point P7 side is in the “L” state. Therefore, assuming that the number of turns of the primary side winding 311 and the number of turns of the secondary side winding 312 in the transformer 31 are Np1 and Ns1, respectively, (Vin / 2) × A voltage | V312 | represented by (Ns1 / Np1) is generated.

  Since the potential high and low states (“H” state and “L” state) at both ends of the secondary windings 312 and 322 are as described above, during the period from the timing t2 to the timing t3, the following occurs. That is, these secondary windings 312 and 322 are in a state of being connected in series with each other (a “two series connection state” described later). In other words, as shown in FIG. 2, the period from the timing t <b> 2 to t <b> 3 is the series connection state period ΔTs between the secondary windings 312 and 322. Accordingly, equal currents flow through the secondary windings 312 and 322, and the voltage VPx (FIG. 2G) applied between the connection point Px and the ground line LG = (| V312). | + | V322 |).

(Timing t3 to t4)
Next, in a period from timing t3 to t4, first, at the timing t3, the switching element S2 is turned off (FIG. 2A).

  Then, as shown in FIG. 8, on the primary side of the transformers 31 and 32, the loop currents Il and Im flow together with the loop currents Ig and Ij described so far. Specifically, the loop current Il flows so as to circulate through the primary winding 311, the capacitor C1, the capacitor C51, and the primary winding 311 in this order. The loop current Im flows so as to circulate via the primary winding 311, the capacitor C 2, the capacitor C 52, and the primary winding 311 in this order.

  These loop currents Il and Im (corresponding to “circulating current” to be described later) flow due to the energy stored in the leakage inductance (not shown) of the transformer 31 so that the current direction so far is maintained. Flowing into. In other words, the leakage inductance of the transformer 32 and the capacitors C1, C2, C51, and C52 cooperate to form an LC resonance circuit, and the LC resonance operation is performed, so that the loop currents Il and Im flow. . The loop currents Il and Im charge the capacitor C2 while discharging the capacitor C1.

  On the other hand, on the secondary side of the transformers 31 and 32, as shown in FIG. 8, the loop current Io flows together with the loop current Ik and the output current Iout described so far. This loop current Io flows so as to circulate through the secondary winding 322, the rectifier diode 431, the choke coil Lch, the output smoothing capacitor Cout, the rectifier diode 422, and the secondary winding 322 in this order.

  Thereafter, when the voltage between both ends of the switching element S2 = Vin and the voltage between both ends of the switching element S1 reaches 0V (the potential at the connection point P1 = Vin) in the period from the timing t3 to t4, become that way.

  That is, as shown in FIG. 9, the diode D1 as the body diode becomes conductive. Therefore, instead of the loop currents Il and Im shown in FIG. 8, the loop current Ip flowing through the diode D1 flows. Specifically, the loop current Ip flows so as to circulate through the primary side winding 311, the diode D 1, the capacitor C 51, and the primary side winding 311 in this order.

  At this time, on the secondary side of the transformers 31 and 32, the loop currents Ik and Io and the output current Iout shown in FIG. 8 continue to flow as they are, and the load 7 is driven.

  Subsequently, after the diode D1 is turned on in this way, the switching element S1 is turned on as shown in FIG. 10 (FIG. 2A). Thereby, the ZVS operation is realized, and as a result, the loss (switching loss) in the switching element S1 is reduced. At this time, as shown in FIG. 10, a loop current Iq flowing through the switching element S1 flows instead of the loop current Ip shown in FIG. This loop current Iq flows so as to circulate through the primary winding 311, the switching element S 1, the capacitor C 51 and the primary winding 311 in this order. Note that the time when the energy stored in the leakage inductance of the transformer 31 described above is completely released corresponds to the timing t4 in FIG.

(Timing t4 to t5)
Next, as shown in FIG. 11, during the period from timing t4 to t5, the following occurs. That is, first, on the primary side of the transformers 31 and 32, a loop current Ir having a direction opposite to the loop current Iq shown in FIG. 10 flows. That is, the direction of the loop current is reversed. This loop current Ir flows so as to circulate through the primary winding 311, the switching element S 1, the capacitor C 51 and the primary winding 311 in this order.

  With such current reversal on the primary side, on the secondary side of the transformers 31 and 32, as shown in FIG. 11, the loop current Is flows instead of the loop current Ik described so far. Become. The loop current Is flows so as to circulate through the secondary winding 312, the rectifier diode 411, the choke coil Lch, the output smoothing capacitor Cout, the rectifier diode 422, and the secondary winding 312 in this order.

  Further, the period from the timing t4 to t5 is a power transmission period from the primary side to the secondary side of the transformers 31 and 32. Note that a period from the timing t4 to a timing t8 described later is a power transmission period using the transformer 31.

  At this time, in the primary side winding 311 of the transformer 31, the connection point P3 side is in the “L” state, the connection point P1 side is in the “H” state, and in the secondary side winding 312, the connection point P8 side is in the “L” state. The connection point P7 side is in the “H” state. Therefore, a voltage | V312 | represented by (Vin / 2) × (Ns1 / Np1) is generated between both ends of the secondary winding 312.

  On the other hand, in the primary side winding 321 of the transformer 32, the connection point P3 side is in the “H” state and the connection point P6 side is in the “L” state, and in the secondary side winding 322, the connection point P9 side is in the “H” state. The point P8 side is in the “L” state. Therefore, a voltage | V322 | represented by (Vin / 2) × (Ns2 / Np2) is generated between both ends of the secondary winding 322.

  Since the potential levels (“H” state, “L” state) at both ends of the secondary windings 312 and 322 are as described above, during the period from the timing t4 to the timing t5, the following occurs. That is, these secondary windings 312 and 322 are in a state of being connected in parallel to each other (a “two parallel connection state” described later). In other words, as shown in FIG. 2, the period from timing t4 to t5 is the parallel connection state period ΔTp between the secondary windings 312 and 322. Therefore, the voltage VPx applied between the connection point Px and the ground line LG (FIG. 2 (G)) = | V312 | = | V322 |, and the period of the above-described timing t2 to t3 (series connection state period ΔTs). The value of the voltage VPx is halved (1/2).

  Further, since the choke coil Lch (inductor) functions as a current source, it tries to maintain a flowing current. Therefore, even if the secondary windings 312 and 322 are connected in parallel to each other during the period of the timing t4 to t5, the current flowing through the choke coil Lch is out of the secondary windings 312 and 322. , Mainly through the secondary winding 322. Therefore, in FIG. 11, the loop current Is flowing through the secondary winding 312 and the loop current Ir flowing through the corresponding primary winding 311 are indicated by broken lines for convenience.

  After that, at timing t5, the switching element S4 is turned off (FIG. 2B). Thus, the operation for the first half cycle (timing t0 to t5) is completed.

(B-2. Operation for half cycle in the latter half)
Next, the operation of the latter half cycle (timing t5 to t0) after timing t0 to t5 shown in FIG. 2 will be described.

  The operation for the latter half cycle is basically the same as the operation for the first half cycle (timing t0 to t5) described with reference to FIGS. That is, as indicated by parentheses in FIG. 2, timing t0 and timing t5, timing t1 and timing t6, timing t2 and timing t7, timing t3 and timing t8, and timing t4 and timing t9 are basically It is an equivalent state. Further, the operation for the latter half cycle is the relationship between the switching element S2 (capacitor C2, diode D2) and the switching element S4 (capacitor C4, diode D4) in the operation for the first half cycle. The relationship is replaced by the relationship between the capacitor C1, the diode D1) and the switching element S3 (capacitor C3, diode D3).

  Therefore, the description of the details of the operation for the latter half cycle is omitted. This is the end of the description of the series of operations shown in FIG.

(C. Action / effect)
As described above, the switching power supply device 1 according to the present embodiment has the circuit configuration shown in FIG. 1 and the operations shown in FIGS. It is done.

  That is, first, the drive circuit 5 performs switching drive so that the two inverter circuits 21 and 22 operate with a phase difference φ. At this time, the drive circuit 5 performs switching driving so that the connection state between the secondary windings 312 and 322 included in the two transformers 31 and 32 is switched (switched at a predetermined time ratio). The output voltage Vout is controlled.

  Here, with reference to the schematic diagrams shown in FIGS. 12A to 12C, the control of the output voltage Vout by such switching of the connection state will be specifically described.

  In the present embodiment, the drive circuit 5 has a connection state between the secondary windings 312 and 322 in the two parallel connection state (see FIG. 12B) and the two series connection state (see FIG. 12C). Switching drive for each of the inverter circuits 21 and 22 is performed. In other words, the two parallel connection state or the two series connection state is switched between when the outputs of the two transformers 31 and 32 are in the same phase and in the opposite phase.

  In the two parallel connection state, as shown in FIG. 12B, the secondary windings 312 and 322 have currents I2p1 and I2p2 in the direction of the combination indicated by the solid line or the broken line, respectively. Flow in parallel with each other. Specifically, referring to the configuration of the rectifying / smoothing circuit 4 shown in FIG. 12A, the current I2p1 indicated by the solid line is applied to the rectifying diode 412, the secondary winding 312 and the rectifying diode 421 in this order. It flows to go through. Further, the current I2p1 indicated by the broken line flows through the rectifier diode 422, the secondary winding 312 and the rectifier diode 411 in this order. Similarly, the current I2p2 indicated by the solid line flows through the rectifier diode 432, the secondary winding 322, and the rectifier diode 421 in this order. Further, the current I2p2 indicated by the broken line flows through the rectifier diode 422, the secondary winding 322, and the rectifier diode 431 in this order.

  On the other hand, in the two-series connection state, as shown in FIG. 12C, the current I2s is serially applied to the secondary windings 312 and 322 in the combination direction indicated by the solid line or the broken line. Flowing into. Specifically, referring to the configuration of the rectifying / smoothing circuit 4 shown in FIG. 12A, the current I2s shown by the solid line is the rectifier diode 412, the secondary winding 312, the secondary winding 322, and the rectification. Each of the diodes 431 flows in this order. The current I2s indicated by the broken line flows through the rectifier diode 432, the secondary winding 322, the secondary winding 312 and the rectifier diode 411 in this order.

  Here, as shown in FIG. 2, the two switching elements S1 and S2 in the inverter circuit 21 are switched and driven with a phase difference of 180 °, and the two switching elements in the inverter circuit 22 are switched. S3 and S4 are also switched by a phase difference of 180 °. Further, as described above, these two inverter circuits 21 and 22 are driven so as to operate with the phase difference φ shown in FIG. 2, for example.

  Therefore, by controlling this phase difference φ, the time ratio (duty) between the two parallel connection states and the two series connection states can be changed, and as a result, the magnitude of the output voltage Vout can be adjusted. become. Specifically, increasing the phase difference φ increases the overlap period of the drive signal SG1 and the drive signal SG3 and the overlap period of the drive signal SG2 and the drive signal SG4, that is, in FIG. This is equivalent to increasing the series connection state period ΔTs shown in FIG.

  Further, in the present embodiment, the drive circuit 5 causes the inverter circuits 21 and 22 so that, for example, the length of the on-duty period of each of the switching elements S1 to S4 is substantially the maximum value (preferably the maximum value). In addition, switching driving is performed.

  Here, as described above, a circulating current (for example, loop currents Ic, Id, Il, Im) is generated using the LC resonance operation in the off-duty period in which power transmission by the transformers 31 and 32 is not performed. Thus, the ZVS operation when the switching element is turned on is realized. However, since the circulating current necessary for this ZVS operation exists in the off-duty period, the power loss increases as the off-duty period becomes longer, and the power conversion efficiency decreases.

  Therefore, in the present embodiment, as described above, in the inverter circuits 21 and 22, switching driving is performed so that the length of the on-duty period of each of the switching elements S1 to S4 becomes a substantially maximum value. As a result, the off-duty period is limited to only the short time described above (in the example of FIG. 2, each period of timing t0 to t1, t3 to t4, t5 to 6, t8 to t9). The generation of circulating current required for ZVS operation is minimized. As a result, power loss due to the circulating current flowing through the body diodes (diodes D1 to D4) of the switching elements S1 to S4 is minimized, and power conversion efficiency is improved. In order to reduce the loss due to the circulating current, it is desirable that the length of the on-duty period of each of the switching elements S1 to S4 is a substantially maximum value. It is possible to work.

  As described above, in the present embodiment, the switching power supply device 1 has the circuit configuration shown in FIG. 1 and the operations shown in FIGS. 2 to 11 are performed, so that it is necessary for the ZVS operation. The generation of circulating current can be minimized. As a result, the conduction loss that does not contribute to power transmission in each of the switching elements S1 to S4 is reduced, and the power conversion efficiency can be easily improved.

  In addition, by reducing such loss, it is possible to use an element with a lower rating, and it is possible to reduce costs. Furthermore, since the heat loss in each of the switching elements S1 to S4 is reduced by reducing the loss, it is possible to lower the performance required for the heat dissipation insulating plate necessary to achieve both heat dissipation and insulation, In this respect as well, cost reduction can be achieved.

  In addition, in the present embodiment, the waveform of the output voltage (for example, corresponding to the voltage VPx shown in FIG. 2G) from the transformers 31 and 32 has a two-stage step shape. For this reason, the amplitude of the ringing generated in each rectifier diode 411, 412, 421, 422, 431, 432 in the rectifying / smoothing circuit 4 is halved compared to the case of the conventional phase shift full bridge converter. As described above, since ringing generated in each rectifier diode is reduced, it is possible to use an element having a lower withstand voltage. Therefore, it becomes possible to use a device having a lower withstand voltage, so that it is possible to reduce costs and reduce loss in each rectifier diode.

<2. Modification>
Subsequently, modified examples (modified examples 1 to 6) of the above-described embodiment will be described. In the following modifications, the same components as those in the embodiment are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

[Modification 1]
(A. Configuration)
FIG. 13 is a circuit diagram illustrating a schematic configuration example of the switching power supply device (switching power supply device 1A) according to the first modification.

  In the switching power supply device 1A of the present modification, in the switching power supply device 1 of the embodiment, the number of inverter circuits and transformers is changed from two to three (the number of these is additionally provided one by one), Accordingly, the configuration of the rectifying / smoothing circuit is also changed. Specifically, the switching power supply 1 </ b> A is provided with an inverter circuit 23 and a transformer 33 in the switching power supply 1, and a rectifying / smoothing circuit 4 </ b> A instead of the rectifying / smoothing circuit 4.

(Inverter circuit 23)
The inverter circuit 23 is arranged in parallel with the inverter circuits 21 and 22 between the input terminals T1 and T2 and the primary side windings 311, 321 and 331 in the transformers 31 to 33. Similarly to the inverter circuits 21 and 22, the inverter circuit 23 is also configured by a half bridge circuit including two switching elements.

  Specifically, the inverter circuit 23 includes two switching elements S5 and S6, capacitors C5 and C6 and diodes D5 and D6 connected in parallel to the switching elements S5 and S6, respectively, and two capacitors C51 and C52. And have. That is, the capacitors C51 and C52 are shared by the inverter circuits 21 to 23, respectively. The diodes D5 and D6 are both connected in the reverse direction, with the cathode disposed on the primary high voltage line L1H side and the anode disposed on the primary low voltage line L1L side.

  In the inverter circuit 23, the first ends of the switching elements S5 and S6, the first ends of the capacitors C5 and C6, the anode of the diode D5, and the cathode of the diode D6 are connected to each other at the connection point P10. Yes. The first ends of the capacitors C51 and C52 are connected to each other at the connection point P3. The second end of the switching element S5, the second end of the capacitor C5, the cathode of the diode D5, and the second end of the capacitor C51 are connected to each other at a connection point P4 on the primary high-voltage line L1H. The second end of the switching element S6, the second end of the capacitor C6, the anode of the diode D6, and the second end of the capacitor C52 are connected to each other at a connection point P5 on the primary side low-voltage line L1L. Between the connection points P3 and P10, a primary winding 331 of a transformer 33 described later is inserted and disposed.

  With this configuration, in the inverter circuit 23, the switching elements S5 and S6 perform on / off operations in accordance with the drive signals SG5 and SG6 supplied from the drive circuit 5, so that the DC input is performed similarly to the inverter circuits 21 and 22. The voltage Vin is converted into an AC voltage and output to the transformer 33. As shown in FIG. 13, these drive signals SG5 and SG6 are the same signals as the drive signals SG1 and SG2 supplied to the switching elements S1 and S2 in the inverter circuit 21, respectively.

  In addition, switching element S5, S6 is comprised by switch elements, such as MOS-FET and IGBT similarly to switching element S1-S4. When MOS-FETs are used as the switching elements S5 and S6, the capacitors C5 and C6 and the diodes D5 and D6 can be constituted by parasitic capacitances or parasitic diodes of the MOS-FETs, respectively. Further, the capacitors C5 and C6 can be configured by junction capacitances of the diodes D5 and D6, respectively. In such a configuration, it is not necessary to provide the capacitors C5 and C6 and the diodes D5 and D6 separately from the switching elements S5 and S6, and the circuit configuration of the inverter circuit 23 can be simplified.

(Transformer 33)
The transformer 33 includes a primary side winding 331 and a secondary side winding 332, similarly to the transformers 31 and 32. The primary winding 331 has a first end connected to the connection point P3 and a second end connected to the connection point P10. The secondary winding 332 has a first end connected to a connection point P9 in the rectifying / smoothing circuit 4A described later, and a second end connected to a connection point P11 in the rectifying / smoothing circuit 4A. Similarly to the transformers 31 and 32, the transformer 33 converts the AC voltage generated by the inverter circuit 23 (AC voltage input to the transformer 33) and outputs the AC voltage from the end of the secondary winding 332. It is supposed to be. In this case, the degree of voltage conversion is determined by the turn ratio between the primary winding 331 and the secondary winding 332.

(Rectifying / smoothing circuit 4A)
The rectifying / smoothing circuit 4A is disposed between the secondary windings 312, 322, and 332 in the transformers 31 to 33 and the output terminals T3 and T4. The rectifying / smoothing circuit 4A includes eight rectifying diodes 411, 412, 421, 422, 431, 432, 441, 442, one choke coil Lch, and one output smoothing capacitor Cout. . That is, as will be described below, the rectifying / smoothing circuit 4 </ b> A further includes rectifying diodes 441 and 442 in the rectifying / smoothing circuit 4. Each of these rectifier diodes 441 and 442 also corresponds to a specific example of “rectifier element” in the present invention.

  In this rectifying / smoothing circuit 4A, four arms are formed by two rectifying diodes arranged in series in the same direction. Specifically, the rectifier diodes 411 and 412 form a first arm, the rectifier diodes 421 and 422 form a second arm, the rectifier diodes 431 and 432 form a third arm, and the rectifier diode 441. , 442 form a fourth arm. That is, a fourth arm is additionally formed in addition to the first to third arms formed in the rectifying / smoothing circuit 4A. The first to fourth arms are arranged in parallel between the output terminals T3 and T4. Specifically, the connection point (connection point Px) between the first ends of the first to fourth arms is connected to the output terminal T3 via the choke coil Lch and the output line LO, and the first to fourth arms. A connection point between the second ends of the arms is connected to a ground line LG extending from the output terminal T4.

  Here, in the additionally formed fourth arm, the cathodes of the rectifier diodes 441 and 442 are respectively disposed on the first end side of the fourth arm, and the anodes of the rectifier diodes 441 and 442 are provided. Are arranged on the second end side of the fourth arm. Specifically, the cathode of the rectifier diode 441 is connected to the connection point Px, the anode of the rectifier diode 441 and the cathode of the rectifier diode 442 are connected to each other at the connection point P11, and the anode of the rectifier diode 442 is connected to the ground line LG. Has been.

  In addition, secondary windings 312, 322, and 332 of the transformers 31 to 33 are individually H-bridge connected between adjacent ones of the first to fourth arms. Specifically, the secondary winding 312 of the transformer 31 is H-bridge connected between the first arm and the second arm that are adjacent to each other, and the second arm and the third arm that are adjacent to each other. Between these, the secondary winding 322 of the transformer 32 is H-bridge connected. Further, the secondary winding 332 of the transformer 33 is H-bridge connected between the third arm and the fourth arm adjacent to each other. More specifically, the secondary winding 312 is inserted between the connection point P7 on the first arm and the connection point P8 on the second arm, and A secondary winding 322 is inserted between the connection point P8 and the connection point P9 on the third arm. Further, the secondary winding 332 is inserted between the connection point P9 on the third arm and the connection point P11 on the fourth arm.

(B. Operation and action / effect)
The switching power supply device 1A basically operates in the same manner as the switching power supply device 1, and thus basically the same effect can be obtained by the same operation.

  At this time, the drive signals SG5 and SG6 are the same signals as the drive signals SG1 and SG2 supplied to the switching elements S1 and S2 in the inverter circuit 21, respectively, as described above. Therefore, in the switching power supply device 1A as a whole, from the left side to the right side in FIG. 13, the odd-numbered inverter circuits (inverter circuits 21 and 23 in this example) use the same drive signal to switch each internal switching. The element is driven. Further, in the even-numbered inverter circuits (inverter circuit 22 in this example), the internal switching elements are driven using the same drive signal.

  Further, for example, as schematically illustrated in FIGS. 14A to 14C, in this switching power supply device 1 </ b> A, the connection state is switched as follows, similarly to the switching device 1 of the embodiment. To work. In other words, in the drive circuit 5 of this modification, the connection state of the three secondary windings 312, 322, and 332 has three parallel connection states (see FIG. 14B) and three series connection states (see FIG. 14). Switching driving is performed for each of the inverter circuits 21, 22, and 23. In other words, the three parallel connection state or the three series connection state is switched between when the outputs of the three transformers 31, 32, and 33 are in the same phase and in the opposite phase. As a result, in this modified example, it is possible to further expand the voltage range at the time of voltage conversion from the DC input voltage Vin to the DC output voltage Vout, as compared to the above embodiment.

  In the three parallel connection state, as shown in FIG. 14B, the secondary windings 312, 322, and 332 have currents I 3 p 1, 1 in the direction of the combination indicated by the solid line or the broken line, respectively. I3p2 and I3p3 flow in parallel with each other. Specifically, referring to the configuration of the rectifying / smoothing circuit 4A shown in FIG. 14A, the current I3p1 indicated by the solid line is applied to the rectifying diode 412, the secondary winding 312 and the rectifying diode 421 in this order. It flows to go through. Further, the current I3p1 indicated by the broken line flows through the rectifier diode 422, the secondary winding 312 and the rectifier diode 411 in this order. Similarly, a current I3p2 indicated by a solid line flows through the rectifier diode 432, the secondary winding 322, and the rectifier diode 421 in this order. Further, the current I3p2 indicated by the broken line flows through the rectifier diode 422, the secondary winding 322, and the rectifier diode 431 in this order. Similarly, a current I3p3 indicated by a solid line flows through the rectifier diode 432, the secondary winding 332, and the rectifier diode 441 in this order. Also, the current I3p3 indicated by the broken line flows through the rectifier diode 442, the secondary winding 332, and the rectifier diode 431 in this order.

  On the other hand, in the three-series connection state, as shown in FIG. 14C, the secondary windings 312, 322, and 332 each have a current I3s in the combination direction indicated by a solid line or a broken line. It flows in series. Specifically, referring to the configuration of the rectifying / smoothing circuit 4A shown in FIG. 14A, the current I3s shown by the solid line is the rectifier diode 412, the secondary winding 312, the secondary winding 322, 2 Each flows through the secondary winding 332 and the rectifier diode 441 in this order. The current I3s indicated by the broken line flows through the rectifier diode 442, the secondary winding 332, the secondary winding 322, the secondary winding 312 and the rectifier diode 411 in this order.

[Modification 2]
FIG. 15A to FIG. 15C schematically illustrate a circuit configuration example and an operation example of the switching power supply device (switching power supply device 1B) according to the modification example 2, respectively.

(A. Configuration)
In the switching power supply device 1B of the present modification, in the switching power supply device 1 of the embodiment, the number of inverter circuits and transformers is changed from two to four (two of these are additionally provided), Accordingly, the configuration of the rectifying / smoothing circuit is also changed. Specifically, the switching power supply device 1B is obtained by further providing inverter circuits 23 and 24 and transformers 33 and 34 in the switching power supply device 1 and a rectifying and smoothing circuit 4B instead of the rectifying and smoothing circuit 4. . In other words, the switching power supply device 1B further includes the inverter circuit 24 and the transformer 34 having the primary side winding 341 and the secondary side winding 342 in the switching power supply device 1A described in the first modification, and rectification. A rectifying / smoothing circuit 4B is provided instead of the smoothing circuit 4A.

  Here, since the configurations of the inverter circuit 24 and the transformer 34 are the same as the configurations of the inverter circuits 21 to 23 and the transformers 31 to 33, detailed descriptions thereof are omitted. The rectifying / smoothing circuit 4B further includes two rectifying diodes (one arm) in the rectifying / smoothing circuit 4A, and is similar to the relationship between the rectifying / smoothing circuits 4 and 4A described in the first modification. Therefore, detailed description thereof is omitted. Each of the two rectifier diodes described above also corresponds to a specific example of “rectifier element” in the present invention.

(B. Operation and action / effect)
The switching power supply device 1B basically operates in the same manner as the switching power supply devices 1 and 1A, so that basically the same effect can be obtained by the same operation.

  At this time, the drive signals for the switching elements in the inverter circuit 24 are the same signals as the drive signals SG3 and SG4 supplied to the switching elements S3 and S4 in the inverter circuit 22 as described in the first modification. It has become. That is, in the entire switching power supply 1B, from the left side to the right side in FIG. 15, the odd-numbered inverter circuits (inverter circuits 21 and 23 in this example) use the same drive signal to switch each internal switching. The element is driven. Further, in the even-numbered inverter circuits (in this example, the inverter circuits 22 and 24), the internal switching elements are driven using the same drive signal.

  Further, for example, as schematically shown in FIGS. 15A to 15C, the switching power supply device 1B is connected in the following manner, similarly to the switching devices 1 and 1A described so far. Operates so that the state changes. That is, in the drive circuit 5 of this modification, the connection state of the four secondary windings 312, 322, 332, and 342 is such that the four parallel connection states (see FIG. 15A), the two series connections, Switching drive for each of the inverter circuits 21, 22, 23, and 24 so as to switch between a mixed connection state of two parallel connections (see FIG. 15B) and a four series connection state (see FIG. 15C). I do. In other words, the four parallel connection state, the mixed connection state, or the four series connection state is switched between when the outputs of the three transformers 31, 32, 33, and 34 are in the same phase and in the opposite phase. become. As a result, in the present modification, the voltage range for voltage conversion from the DC input voltage Vin to the DC output voltage Vout can be further expanded as compared with the first modification.

  In the four parallel connection state, as shown in FIG. 15A, the secondary windings 312, 322, 332, and 342 have currents in the combinations indicated by solid lines or broken lines, respectively. I4p1, I4p2, I4p3, and I4p4 flow in parallel with each other. On the other hand, in the mixed connection state, as shown in FIG. 15B, the secondary windings 312, 322, 332, and 342 have currents I 2 s 2 p 1 in the direction of the combination indicated by the solid line or the broken line. , I2s2p2 flow in parallel with each other. On the other hand, in the four-series connection state, as shown in FIG. 15C, the secondary windings 312, 322, 332, and 342 have currents in the direction of the combination indicated by the solid line or the broken line, respectively. I4s flows in series. The details of the path (the rectifier diode and the secondary winding through which the currents I4p1, I4p2, I4p3, I4p4, I2s2p1, I2s2p2, and I4s flow shown by the solid line and the broken line will be described with reference to FIGS. Since it is basically the same as that described above, detailed description is omitted.

  In this way, in the present modification, such a 4-parallel connection state, a mixed connection state, and a 4-series connection state can be seamlessly changed by the phase difference between the inverter circuits 21 to 24.

[Modification 3]
(A. Configuration)
FIG. 16 is a circuit diagram illustrating a schematic configuration example of the switching power supply device (switching power supply device 1 </ b> C) according to the third modification.

  The switching power supply device 1C of this modification is provided with inverter circuits 21C and 22C made of full bridge circuits in place of the inverter circuits 21 and 22 made of half bridge circuits in the switching power supply device 1 of the embodiment. It is. These inverter circuits 21C and 22C are arranged in parallel with each other between the input terminals T1 and T2 and the primary windings 311 and 321 as in the inverter circuits 21 and 22.

(Inverter circuits 21C, 22C)
The inverter circuit 21C includes four switching elements S1 to S4, and capacitors C1 to C4 and diodes D1 to D4 that are connected in parallel to the switching elements S1 to S4, respectively. The inverter circuit 22C includes four switching elements S5 to S8, capacitors C5 to C8 and diodes D5 to D8 connected in parallel to the switching elements S5 to S8, respectively, and a resonance inductor Lr. Yes. In addition, all of the diodes D1 to D8 have a cathode disposed on the primary high voltage line L1H side and an anode disposed on the primary low voltage line L1L side, and are in a reverse direction connection state.

  In the inverter circuit 21C, the first ends of the switching elements S1 and S2, the first ends of the capacitors C1 and C2, the anode of the diode D1, and the cathode of the diode D2 are connected to each other at the connection point P1. . The first ends of the switching elements S3 and S4, the first ends of the capacitors C3 and C4, the anode of the diode D3, and the cathode of the diode D4 are connected to each other at the connection point P3. The second ends of the switching elements S1, S3, the second ends of the capacitors C1, C3, and the cathodes of the diodes D1, D3 are connected to each other at a connection point P4 on the primary high-voltage line L1H. . The second ends of the switching elements S2 and S4, the second ends of the capacitors C2 and C4, and the anodes of the diodes D2 and D4 are connected to each other at a connection point P5 on the primary low-voltage line L1L. . A primary winding 311 of the transformer 31 is inserted between the connection points P1 and P3. With this configuration, in the inverter circuit 21C, the switching elements S1 to S4 perform on / off operations according to the drive signals SG1 to SG4 supplied from the drive circuit 5, thereby converting the DC input voltage Vin into an AC voltage. It outputs to the transformer 31. As shown in FIG. 16, the drive signal SG1 and the drive signal SG4 are the same signal, and the drive signal SG2 and the drive signal SG3 are the same signal.

  In the inverter circuit 22C, the first ends of the switching elements S5 and S6, the first ends of the capacitors C5 and C6, the anode of the diode D5, and the cathode of the diode D6 are connected to each other at the connection point P12. . The first ends of the switching elements S7 and S8, the first ends of the capacitors C7 and C8, the anode of the diode D7, and the cathode of the diode D8 are connected to each other at the connection point P13. The second ends of the switching elements S5 and S7, the second ends of the capacitors C5 and C7, and the cathodes of the diodes D5 and D7 are connected to each other at the connection point P4. The second ends of switching elements S6 and S8, the second ends of capacitors C6 and C8, and the anodes of diodes D6 and D8 are connected to each other at connection point P5. Between the connection points P12 and P13, the primary winding 321 of the transformer 32 and the resonance inductor Lr are inserted and arranged in a state of being connected in series with each other. Specifically, the first end of the primary winding 321 is connected to the connection point P12, the second end of the primary winding 321 and the first end of the resonance inductor Lr are connected to each other, and A second end of the inductor Lr is connected to the connection point P13. With this configuration, in the inverter circuit 22C, the switching elements S5 to S8 perform on / off operations according to the drive signals SG5 to SG8 supplied from the drive circuit 5, thereby converting the DC input voltage Vin into an AC voltage. It outputs to the transformer 32. As shown in FIG. 16, the drive signal SG5 and the drive signal SG8 are the same signal, and the drive signal SG6 and the drive signal SG7 are the same signal.

  Each of the switching elements S1 to S8 is configured by a switching element such as a MOS-FET or an IGBT, for example, as described above. When MOS-FETs are used as the switching elements S1 to S8, the capacitors C1 to C8 and the diodes D1 to D8 can be configured by parasitic capacitances or parasitic diodes of the MOS-FETs, respectively. Further, the capacitors C1 to C8 can be configured by junction capacitances of the diodes D1 to D8, respectively. In such a configuration, it is not necessary to provide the capacitors C1 to C8 and the diodes D1 to D8 separately from the switching elements S1 to S8, and the circuit configurations of the inverter circuits 21C and 22C can be simplified.

(B. Operation and action / effect)
FIG. 17 is a timing waveform diagram showing the voltage waveform or current waveform of each part in the switching power supply apparatus 1 </ b> C, similar to FIG. 2 described above. Specifically, FIGS. 17A and 17B show voltage waveforms of the drive signals SG1 to SG8. FIGS. 17C to 17F show currents I311 and I321 flowing through the primary windings 311 and 321 and currents I411 and I412 flowing through the rectifier diodes 411, 412, 421, 422, 431 and 432, respectively. , I421, I422, I431, and I432, respectively. FIG. 17G shows the voltage waveform of the voltage VPx described above. FIG. 17H shows current waveforms of the current ILch flowing through the choke coil Lch and the output current Iout. In addition, the direction of each voltage and each current is set to the direction indicated by the arrow in FIG.

  Therefore, the switching power supply device 1C basically operates in the same manner as the switching power supply device 1 and can basically obtain the same effect by the same operation.

  At this time, as described above, the drive signal SG1 and the drive signal SG4 are the same signal, and the drive signal SG2 and the drive signal SG3 are the same signal. Similarly, the drive signal SG5 and the drive signal SG8 are the same signal, and the drive signal SG6 and the drive signal SG7 are the same signal. Also, timings t10 to t19 in FIG. 17 correspond to timings t0 to t9 in FIG. 2 of the embodiment. Similarly, timings t15 to t19 in FIG. 17 correspond to timings t10 to t14 in FIG. Therefore, the drive signals SG1 and SG4 shown in FIG. 17 correspond to the drive signal SG1 shown in FIG. 2, respectively, and the drive signals SG2 and SG3 shown in FIG. 17 correspond to the drive signal SG2 shown in FIG. Similarly, the drive signals SG6 and SG7 shown in FIG. 17 correspond to the drive signal SG3 shown in FIG. 2, respectively, and the drive signals SG5 and SG8 shown in FIG. 17 correspond to the drive signal SG4 shown in FIG. .

  Further, assuming that the number of turns of the primary windings 311 and 321 in this modification is Npf, and the number of turns of the primary windings 311 and 321 in the embodiment is Nph, (Npf / Nph) = 2. Therefore, the following can be said. That is, first, when the size of the load 7 is the same, the current flowing through the switching elements S1 to S8 of the present modification is about half the current flowing through the switching elements S1 to S4 of the embodiment. . In addition, the voltage applied to the transformers 31 and 32 is (Vin / 2) in the embodiment, and is Vin in the present modification. Therefore, the number of turns in the secondary windings 321 and 322 is the same, As described above, by setting (Npf / Nph) = 2, it can be said that the switching power supply devices 1 and 1C are equivalent to each other.

  Incidentally, in the switching power supply 1C of the present modification, in addition to the output voltage control using the phase difference φ between the inverter circuits described above (in this example, between the inverter circuits 21C and 22C), each inverter circuit 21C , 22C can also be used in combination with output voltage control utilizing the phase difference between the arms. However, in this case, since the generation period of the circulating current used for the ZVS operation described above becomes long, the power loss reduction effect (the power conversion efficiency improvement effect) described in the embodiment is reduced. .

  In addition, for the inverter circuit composed of a full bridge circuit as in this modification, three or more inverter circuits are provided in the same manner as in Modifications 1 and 2, and accordingly, three or more transformers are provided and rectification is performed. Instead of the smoothing circuit 4, rectifying and smoothing circuits 4A and 4B may be provided. Further, unlike the inverter circuit consisting of the half bridge circuit shown in FIG. 1 or the like, the inverter circuit consisting of the full bridge circuit as in this modification example is not provided with the capacitors C51 and C52. It is necessary to provide an input smoothing capacitor Cin.

[Modification 4]
FIG. 18 is a circuit diagram illustrating a schematic configuration example of a switching power supply device (switching power supply device 1D) according to Modification 4.

  The switching power supply device 1D of the present modification is provided with inverter circuits 21D and 22D described below in place of the inverter circuits 21 and 22 in the switching power supply device 1 of the embodiment.

  These inverter circuits 21D and 22D are provided with capacitive elements (capacitors C61 and C62) for preventing partial excitation, respectively. Specifically, in the inverter circuit 21D, a capacitor C61 is inserted between the connection point P1 and the primary winding 311 of the transformer 31. In the inverter circuit 22D, a capacitor C62 is inserted between the connection point P6 and the primary winding 321 of the transformer 32.

  With such a configuration, the switching power supply apparatus 1D can suppress (preferably prevent) partial excitation in the transformers 31 and 32, and can avoid various problems caused by such partial excitation.

  In the switching power supply devices 1A to 1C described in the first to third modifications, capacitors C61 and C62 for preventing partial excitation may be provided in the same manner as in this modification.

[Modification 5]
FIG. 19 is a circuit diagram illustrating a schematic configuration example of a switching power supply device (switching power supply device 1E) according to Modification 5.

  A switching power supply device 1E according to this modification is provided with an inverter circuit 22E described below instead of the inverter circuit 22 in the switching power supply device 1 according to the embodiment.

  This inverter circuit 22E is provided with rectifying elements (diodes D51 and D52) for reverse voltage clamping. Specifically, the diode D51 is disposed such that the anode is connected to the connection point P6 and the cathode is connected to the primary high-voltage line L1H (connection point P4). The diode D52 is arranged such that the anode is connected to the primary low-voltage line L1L (connection point P5) and the cathode is connected to the connection point P6. That is, these diodes D51 and D52 are arranged so as to be connected in series with each other via the connection point P6 between the primary high voltage line L1H and the primary low voltage line L1L.

  With such a configuration, in the switching power supply device 1E, generation of a surge voltage due to the on / off operation of each switch element S1 to S4 is suppressed. As a result, it is possible to reduce the loss in each rectifier diode 411, 412, 421, 422, 431, 432 in the rectifier smoothing circuit 4.

  In the switching power supply devices 1A to 1D described in the first to fourth modifications, reverse voltage clamping diodes D51 and D52 may be provided in the same manner as in this modification.

[Modification 6]
20A to 20C show circuit configuration examples of the rectifying / smoothing circuits (rectifying / smoothing circuits 4C, 4D, and 4E) according to the modified example 6, respectively. Specifically, FIG. 20A shows the circuit configuration of the rectifying / smoothing circuit 4C, FIG. 20B shows the circuit configuration of the rectifying / smoothing circuit 4D, and FIG. 20C shows the circuit configuration of the rectifying / smoothing circuit 4E. Each is shown.

  The rectifying / smoothing circuits 4C, 4D, 4E of the present modification are different from the rectifying / smoothing circuits 4, 4A, 4B described so far in the configuration (number, arrangement, etc.) of the choke coil Lch.

  Specifically, in the rectifying / smoothing circuit 4C shown in FIG. 20A, the connection point (connection point Px) between the first ends of the first to third arms described above and the first of the output smoothing capacitor Cout. Between the ends, two choke coils Lch connected in series with each other are inserted and arranged via the output line LO. The connection point between the second ends of the first to third arms is connected to the second end of the output smoothing capacitor Cout on the ground line LG.

  In the rectifying / smoothing circuit 4D shown in FIG. 20B, the ground line LG is connected between the connection point between the second ends of the first to third arms and the second end of the output smoothing capacitor Cout. Thus, one choke coil Lch is inserted and arranged. Further, the connection point (connection point Px) between the first ends of the first to third arms is connected to the first end of the output smoothing capacitor Cout on the output line LO.

  Further, in the rectifying / smoothing circuit 4E shown in FIG. 20C, between the connection point (connection point Px) between the first ends of the first to third arms and the first end of the output smoothing capacitor Cout. A single choke coil Lch is inserted and arranged via the output line LO. In addition, a single choke coil Lch is inserted between the connection point between the second ends of the first to third arms and the second end of the output smoothing capacitor Cout via the ground line LG. Yes. In the example shown in FIG. 20C, two windings are arranged in place of the two choke coils Lch, and the two windings are magnetically coupled to each other. Two choke coils Lch may be formed.

  As described above, various aspects can be applied to the configuration (number, arrangement, etc.) of the choke coil Lch in the rectifying / smoothing circuit.

  In the rectifying / smoothing circuits 4A, 4B described so far, the number and arrangement of the choke coils Lch may be changed in the same manner as the rectifying / smoothing circuits 4C, 4D, 4E of the present modification.

<3. Other variations>
While the present invention has been described with reference to the embodiments and modifications, the present invention is not limited to these embodiments and the like, and various modifications can be made.

  For example, in the above-described embodiment and the like, the configuration of the inverter circuit has been specifically described. However, the configuration of the inverter circuit is not limited to this, and other configurations may be used. Specifically, in the above-described embodiment, the inverter circuit is a half-bridge circuit that includes two switching elements, or the inverter circuit is a full-bridge circuit that includes four switching elements. The inverter circuit included in the switching power supply apparatus has a common configuration. However, the present invention is not limited to this. For example, in a switching power supply device, one inverter circuit is a half-bridge circuit including two switching elements and the other inverter circuit is a full-bridge circuit including four switching elements. Each inverter circuit included may have a different configuration.

  In the above-described embodiment and the like, the configuration of the rectifying / smoothing circuit has been specifically described. However, the configuration of the rectifying / smoothing circuit is not limited to this, and other configurations may be used. Specifically, for example, each rectifying element in the rectifying / smoothing circuit may be configured by a MOS-FET parasitic diode. In such a case, it is preferable that the MOS-FET itself is also turned on (synchronized rectification is performed) in synchronization with the period in which the parasitic diode of the MOS-FET is conducted. This is because rectification can be performed with a smaller voltage drop. In this case, the anode side of the parasitic diode is arranged on the source side in the MOS-FET, and the cathode side of the parasitic diode is arranged on the drain side in the MOS-FET.

  Furthermore, in the above-described embodiment, the number of inverter circuits and transformers is 2, 3, and 4 respectively (the number of rectifying elements in the rectifying and smoothing circuit is 6, 8, and 10). ) Is taken as an example, but the number of them is not limited to this case. Specifically, the present invention can be applied to the case where the number of inverter circuits and transformers is N (N: an integer equal to or greater than 2). That is, the present invention can be similarly applied not only to the case of N = 2, 3, and 4 described in the above embodiments, but also to an arbitrary number of N = 5 or more. In this case, the number of rectifying elements in the rectifying / smoothing circuit is {2 × (N + 1)}, and the number of arms in the rectifying / smoothing circuit is (N + 1). In this case, the type of connection state between the secondary windings of the transformer during the operation of the switching power supply device is determined by the number of divisors in integer N (a combination of divisors). Furthermore, the number and number of inverter circuits, transformers, rectifying elements, and arms are not limited to the physical number or number, and mean the number or number existing in the equivalent circuit.

  In addition, in the above-described embodiment and the like, a DC-DC converter has been described as an example of the switching power supply device according to the present invention. It is also possible to apply to.

  Moreover, you may apply each structural example etc. demonstrated so far in arbitrary combinations.

  DESCRIPTION OF SYMBOLS 1,1A-1E ... Switching power supply device, 10 ... Battery, 21, 22, 23, 24, 21C, 21D, 22C, 22D, 22E ... Inverter circuit, 31, 32, 33, 34 ... Transformer, 311, 321, 331 , 341 ... primary winding, 312, 322, 332, 342 ... secondary winding, 4, 4A to 4E ... rectification smoothing circuit, 411, 412, 421, 422, 431, 432, 441, 442 ... rectification Diode, 5 ... Drive circuit, 7 ... Load, T1, T2 ... Input terminal, T3, T4 ... Output terminal, L1H ... Primary high voltage line, L1L ... Primary low voltage line, LO ... Output line, LG ... Ground line , Vin ... DC input voltage, Vout ... DC output voltage, Iout ... output current, Ia to Is ... current, Cin ... input smoothing capacitor, Cout ... output smoothing capacitor, S1-S8 ... switch SG1-SG8 ... driving signal, D1-D8, D51, D52 ... diode, C1-C8, C51, C52, C61, C62 ... capacitor, Lr ... resonant inductor, Lch ... choke coil, P1-P13 ... connection Points, t0 to t9, t10 to t19, timing, φ, phase difference, ΔTs, series connection state period, ΔTp, parallel connection state period.

Claims (12)

A pair of input terminals to which the input voltage is input;
A pair of output terminals from which output voltage is output;
N (N: an integer of 2 or more) transformers each having a primary winding and a secondary winding;
N inverter circuits arranged in parallel with each other between the input terminal pair and the primary winding, each including a switching element;
And {2 × (N + 1)} rectifier elements, a choke coil, and a capacitive element disposed between the output terminal pair, disposed between the output terminal pair and the secondary winding. A rectifying and smoothing circuit configured to include:
A driving unit that performs switching driving for controlling the operations of the switching elements in the N inverter circuits, respectively.
In the rectifying and smoothing circuit,
(N + 1) arms each having two rectifier elements arranged in series in the same direction are arranged in parallel between the output terminals,
The secondary windings of the N transformers are individually H-bridge connected between adjacent arms of the (N + 1) arms,
The choke coil is disposed between the (N + 1) arms and the capacitive element ,
The drive unit is
The switching drive is performed so that the N inverter circuits operate with a phase difference, and the length of the on-duty period of the switching element is substantially maximum in each of the N inverter circuits. By doing
A switching power supply apparatus that limits an off-duty period of the switching elements only to a dead time period for avoiding an electrical short circuit due to an ON state of the plurality of switching elements between the input terminal pairs . The connection point between the first ends of the (N + 1) arms and the first end of the capacitive element, and the connection point of the second ends of the (N + 1) arms and the first of the capacitive elements. The switching power supply device according to claim 1, wherein the choke coil is inserted and disposed in at least one of the two ends. In each of the (N + 1) arms,
A cathode of the rectifying element is disposed on the first end side;
The switching power supply according to claim 2, wherein an anode of the rectifying element is disposed on the second end side. The switching power supply device according to any one of claims 1 to 3, wherein the rectifying element is configured by a parasitic diode of a field effect transistor. 5. The N inverter circuit includes a half bridge circuit including two switching elements or a full bridge circuit including four switching elements. 6. The switching power supply device described in 1. The drive unit controls the magnitude of the output voltage by performing the switching drive so that the connection state of the N secondary windings included in the N transformers is switched. The switching power supply device according to any one of claims 5 to 5. The switching power supply device according to any one of claims 1 to 6 , wherein N is 2. The drive unit performs the switching drive so that a connection state between the two secondary windings included in the two transformers is switched between a two series connection state and a two parallel connection state. The switching power supply device according to claim 7 . The switching power supply device according to any one of claims 1 to 6 , wherein N is 3. The drive unit performs the switching drive so that the connection state of the three secondary windings included in the three transformers is switched between a three series connection state and a three parallel connection state. The switching power supply device according to claim 9 . The switching power supply device according to any one of claims 1 to 6 , wherein N is 4. In the drive unit, the connection state of the four secondary windings included in the four transformers is a mixture of a 4-series connection state, a 4-parallel connection state, a 2-series connection, and a 2-parallel connection. to switch between a connected state, the switching power supply device according to claim 1 1 for the switching drive.

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