JP2000262047A - Switching regulator power unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance efficiency by suppressing the flyback voltage added to a switch element, even if a sufficient value of inductance to control the recovery current from an output rectifying diode is inserted. SOLUTION: A path leading to a switch element SW from an output rectifying diode D1 of a boosting chopper is provided with an inductance L2 for current control, to control the recovery current to an output rectifying diode D1 in a transient period, when the switching element SW is shifted from on to off. Moreover, a snubber circuit A, where a diode D2 for absorbing the flyback voltage generated in the inductance L2 for recovery current control during the transition period when the switching element SW is shifted from off to on, and a capacitor C2 are connected in series, is connected in parallel with the switching element SW. Furthermore, this power unit is provided with an energy shifting course which causes the energy accumulated in the capacitor of the snubber circuit to shift from the junction between the diode D2 and the capacitor C2 of the snubber circuit A to the positive side of the capacitor C1 for smoothing of output via an inductance L3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching regulator power supply using a boost chopper.

[0002]

2. Description of the Related Art Conventionally, as a switching regulator power supply using a boost chopper of this type, for example, FIG.
There are the following.

In FIG. 6, a step-up chopper includes a choke coil L1 for a chopper and a switching element S such as an FET.
W, a diode D1 as an output rectifier, and an output smoothing capacitor C1.

[0004] The switching element SW is controlled by a pulse control circuit PG to obtain a ratio Vou between an input voltage Vin and an output voltage Vout.
On / off control is performed by the switch-on time with respect to the switching cycle T so that t / Vin exceeds 1.

When the switching element SW is on, magnetic energy is stored in the chopper choke coil L1 by a current from the input power supply, and when the switching element SW is off, the energy of the input power supply and the chopper choke coil L1 is converted into a diode. The operation of shifting to the load-side output smoothing capacitor C1 through D1 is repeated.

[0006]

However, the switching regulator power supply using such a conventional boosting chopper has the following problems.

In the conventional step-up chopper, a recovery current from the diode D1, ie, a transient reverse current, is generated during a transition period of the switching element SW from off to on due to the recovery characteristic of the diode D1 used as an output rectifying element. A current flows through the switching element SW. For this reason, there is a problem that the recovery current directly causes loss of the switching element SW, and loss of the switching element is large.

[0008] Further, due to a sudden current change at the moment when the switching element SW is switched from on to off, an abrupt change in magnetic flux is obtained from an area S2 of a hatched portion generated in a wiring connecting the switching element SW, the diode D1 and the output smoothing capacitor C1. This causes adverse effects such as malfunctions on surrounding electronic components, and when viewed as a power supply device, disadvantages such as large output noise and large input feedback noise are likely to occur.

In order to solve the problem of the loss in the switching element SW due to the recovery current of the diode D1, an inductance may be inserted in the loop between the diode D1 and the switching element SW. In the conventional step-up chopper of FIG. 6, an inductance L depending on an area S2 of a hatched portion generated in a wiring connecting the switching element SW, the diode D1, and the output smoothing capacitor C1.
4 equivalently exists between the diode D1 and the switching element SW. However, the effect of suppressing the recovery current cannot be expected because the value of the inductance L4 is small.

For this reason, there is a type in which an inductance for suppressing a recovery current is inserted between the switching element SW of the diode D1 and the switching element SW. However, since the flyback voltage generated by this inductance applies a high voltage to the switching element SW, it is easy. Large values could not be inserted.

The present invention has been made in view of such a conventional problem, and a flyback which is added to a switching element even when an inductance having a sufficient value for suppressing a recovery current flowing from an output rectifying diode is inserted. It is an object of the present invention to provide a switching regulator power supply using a boost chopper that suppresses voltage and increases efficiency.

[0012]

In order to achieve this object, the present invention is configured as follows. First, the present invention is a switching regulator power supply device using a boost chopper. The boost chopper accumulates magnetic energy in a chopper inductance with a current flowing during an on period of the switching element, and inputs the magnetic energy during an off period of the switching element. The energy of the power supply and the chopper inductance is transferred to the load-side output smoothing capacitor through the output rectifier.

The present invention relates to a switching regulator power supply device using such a step-up chopper. The present invention relates to a recovery current flowing in an output rectifying element during a transitional period when the switching element changes from on to off in a path from the output rectifying element to the switching element. A recovery current suppression inductance is provided in parallel with the switching element, and a diode and a capacitor are connected in series to absorb the flyback voltage generated in the recovery current suppression inductance during the transition period when the switching element transitions from off to on. The snubber circuit is connected in parallel with the switching element, and an energy transfer path for transferring the energy stored in the snubber circuit capacitor is provided from the connection point of the diode and the capacitor of the snubber circuit to the positive side of the output smoothing capacitor. To be

As described above, according to the present invention, even if an inductance large enough to block the recovery current is inserted into the loop of the output rectifier diode and the switching element, a large flywheel is provided by providing the recovery current blocking inductance. Since the back voltage is absorbed by the snubber circuit connected in parallel with the switching element, the recovery current can be surely suppressed and the loss of the switching element can be reduced without increasing the withstand voltage of the switching element.

A diode is connected to a capacitor that absorbs flyback energy of a snubber circuit connected in parallel with the switching element, and prevents energy stored in the capacitor from flowing back to the switching element to prevent loss.

Also, by providing a path for moving the energy stored in the capacitor of the snubber circuit to the output smoothing capacitor on the load side, the energy stored in the recovery current element inductance can be efficiently released to the output side. Can be.

Further, the loop of the snubber circuit connected in parallel with the switching element reduces the area of the wiring that undergoes a rapid current change when the switching element changes from on to off, and the magnetic flux generated from this wiring area portion And the adverse effect on the control system of the device itself is reduced.

An energy transfer inductance is inserted and connected to an energy transfer path for transferring the energy stored in the snubber circuit capacitor to the output side. If the loss is not large or the cost is reduced, a resistor for energy transfer may be inserted and connected to the energy transfer path from the snubber circuit.

The connection on the output capacitor side of the energy transfer path for transferring the energy stored in the snubber circuit capacitor is connected between the output rectifying element and the recovery current suppressing inductance.

As the connection position of the recovery current suppressing inductance, the recovery current suppressing inductance is inserted and connected between the chopper inductance and the output rectifying element, and the positive side of the switching element is connected to the chopper inductance and the recovery current suppressing inductance. Connect between

As another connection position of the recovery current suppressing inductance, a recovery current suppressing inductance is inserted and connected to a path connecting the connection point between the chopper inductance and the output rectifying element to the plus side of the switching element. This connection is suitable when it is necessary to reduce the wiring interval between the chopper inductance and the output rectifier diode on the substrate.

[0022]

FIG. 1 is a circuit diagram of a first embodiment of a switching regulator power supply device using a step-up chopper according to the present invention.

In FIG. 1, the step-up chopper includes a choke coil L1 for a chopper, a switching element SW, an output rectifier diode D1, and an output smoothing capacitor C1. As the switching element SW, for example, MOSF
ET is used, and a control pulse from the pulse control circuit PG is input to the gate G.

The circuit configuration of such a step-up chopper is the same as that of the prior art. In addition to this, in the present invention, first, a path connecting the output rectifier diode D1 and the switching element SW, that is, the drain D of the MOSFET, is provided. A recovery current suppressing choke coil L2 having a sufficient inductance value is inserted.

For this reason, the output rectifier diode D1 is connected during the transition period when the switching element SW is switched from off to on.
Therefore, even if a recovery current that is a transient reverse current flows through the switching element SW, the recovery current flowing through the switching element SW can be suppressed by the recovery current suppressing choke coil L2 having a large inductance value.

By providing the recovery current suppressing choke coil L2 having such a large value, a large flyback voltage is applied to the recovery current suppressing choke coil L2 during the transition period when the switching element SW is switched from on to off. Occurs and is applied to the switching element SW. In order to absorb the flyback voltage generated in the recovery current suppressing choke coil L2, a snubber circuit A is connected in parallel with the switching element SW in the present invention.

In the snubber circuit A, a backflow prevention diode D2 and a flyback voltage absorbing capacitor C2 are connected in series. For this reason, even if an excessive flyback voltage is generated by the recovery current suppressing choke coil L2 having a large value in a transient state in which the switching element SW is switched from on to off, the flyback voltage is provided in the snubber circuit A. It is absorbed by the capacitor C2 and prevents a large flyback voltage from being applied to the switching element SW.

The backflow prevention diode D2 provided in the snubber circuit A causes the energy stored in the capacitor C2 to flow in the reverse direction when the switching element SW is switched from off to on by the flyback voltage, so that the switching element S2
This prevents the loss of W. Further, in the present invention, since the backflow prevention diode D2 is provided, there is no place for the energy stored in the capacitor C2 due to the flyback voltage. Therefore, the output smoothing capacitor C1 is connected via the energy transfer inductance L3 from the connection point of the backflow prevention diode D2 and the capacitor C2.
A new path for energy transfer connected to the positive side of the capacitor is newly provided, and the excess energy stored in the capacitor C2 is transferred to the output smoothing capacitor C1 via the energy transfer inductance L3 to increase the efficiency. I have.

Further, in the first embodiment shown in FIG. 1, a portion where a sudden magnetic flux change occurs due to a sudden current change at the moment when the switching element SW switches from on to off is connected in parallel to the switching element SW. The area S1 of the hatched portion surrounded by the loop wiring including the backflow prevention diode D2 and the capacitor C2 of the snubber circuit A is shown.

The area S1 at which a sudden change in magnetic flux formed by the wiring is generated is determined by the output rectifier diode D1 and the output smoothing capacitor C1 when the snubber circuit is not provided in the conventional switching element SW shown in FIG. Is sufficiently small with respect to an area S2 in which an abrupt change in magnetic flux formed by the wiring of the loop passing through is generated.

As described above, the area S1 in which the magnetic flux formed by the wiring changes abruptly is reduced, thereby adversely affecting the malfunction of the surrounding electronic parts, or causing the output noise and the noise when viewed as a power supply device. Reduce input feedback noise,
An adverse effect on the control system of the device itself can be reduced.

FIG. 2 shows the control pulse VG from the pulse control circuit PG for the switching element SW, the drain current ID flowing through the switching element SW, and the drain-source voltage VDS of the switching element SW in the first embodiment of FIG. It is a waveform diagram.

In the control pulse VG from the pulse control circuit PG shown in FIG. 2A, an ON pulse and an OFF pulse are repeated at a constant period. If the control pulse VG is switched to the ON pulse at time t1, a transition period occurs until time t2 when the switching element SW switches from the OFF state to the ON state.

In this transition period, the output rectifier diode D1 receives the energy of the output smoothing capacitor C1 and attempts to supply a recovery current, which becomes a reverse current, to the switching element SW. However, the output rectifier diode D1
A recovery current suppressing choke coil L2 having an inductance large enough to obtain a recovery current suppressing effect is provided in a path from the switching element SW to the switching element SW. Therefore, the recovery current due to the output rectifier diode D1 is sufficiently suppressed. Thus, the loss of the switching element SW can be suppressed.

Subsequently, when the control pulse VG switches from the on-pulse to the off-pulse at the time t3, a transient period occurs in which the switching element SW switches from on to off until the time t4. By providing the recovery current suppressing choke coil L2 having a large inductance with a recovery current suppressing effect during the transition period when the switching element SW is switched from on to off, a large flyback voltage is applied to the recovery current suppressing choke coil L2. appear.

However, since the snubber circuit A is provided in parallel with the switching element SW, the energy of the flyback voltage generated in the recovery current suppressing choke coil L2 is absorbed by the capacitor C2 via the diode D2 of the snubber circuit A. The flyback voltage applied to the drain-source DS of the switching element SW can be reduced.

The energy stored in the capacitor C2 during the transition period from the time t3 to t4 is transferred to the output smoothing capacitor C1 through the energy transfer inductance L3 when the switching element SW is turned off, and again. Energy can be returned to the output side, and the efficiency of the entire apparatus increases.

When the switching element SW is turned off, the magnetic energy stored in the choke coil L1 for the chopper is transferred to the output smoothing capacitor C1 through the output rectifying element D1 due to the drain current ID flowing during the on period. Of course.

FIG. 3 shows a second embodiment of the present invention. In this embodiment, the snubber circuit A in the first embodiment of FIG.
The energy of the capacitor C2 is output to the output smoothing capacitor C.
1 is characterized in that a resistor R is used in place of the energy transfer inductance L3 provided in the energy transfer path for transferring to 1. This is effective when the loss of the switching regulator power supply device of the present invention using the boost chopper is not so large or when the device cost is reduced.

FIG. 4 is a circuit diagram of a third embodiment of the present invention. In the third embodiment, as an energy transfer path for transferring the energy stored in the capacitor C2 provided in the snubber circuit A to the output smoothing capacitor C1, the output side of the energy transfer inductance L3 is connected to the output rectifier diode D1 and the recovery current suppression. It is connected between the choke coils L2.

In the third embodiment, the distance between the snubber circuit A having the reverse current blocking diode D2 and the capacitor C2 and the output smoothing capacitor C1 is long due to the structure of the printed wiring board, and the positive side of the output smoothing capacitor C1 is increased. This is effective when wiring for connection is difficult as in the embodiment of FIG.

FIG. 5 shows a fourth embodiment of the present invention.
The insertion position of the recovery current suppressing choke coil L2 is changed from the first embodiment. In the fourth embodiment, unlike FIG. 1, the recovery current suppressing choke coil L2 is inserted and connected between the connection point of the chopping coil L1 for the chopper and the output rectifier diode D1 to the drain terminal of the switching element SW. are doing.

The capacitor C2 provided in the snubber circuit A
As an energy transfer path for transferring the energy stored in the storage device to the output smoothing capacitor C1 side, as in the embodiment of FIG.
It is connected to the anode side of the output rectifier diode D1.

The insertion connection position of the recovery current suppressing choke coil L2 in FIG. 5 is determined when the choke coil L1 for chopper and the output rectifier diode D1 are arranged close to each other on the wiring board. It is valid.

In the above embodiment, the case where the choke coil L2 is used as the recovery current suppressing inductance L2 is taken as an example, but the printed wiring board between the output rectifier diode D1 and the switching element SW is used. It can be equivalently obtained by lengthening the above wiring.

The recovery current suppressing inductance may be a saturable reactor using a saturable core other than the choke coil. When a saturable reactor is used as the recovery current suppressing inductance, the loss as a whole can be reduced because the saturable reactor is originally an element that assumes saturation.

Further, in each of the above embodiments, for example, in FIG. 1, for example, the reverse current blocking diode D2 and the capacitor C2 are connected in series to the snubber circuit A connected in parallel with the switching element SW. Switching element SW by recovery current by backflow prevention diode D2 during a transition period when element SW switches from off to on
Loss is reduced.

However, the period during which the recovery current flows through the backflow prevention diode D2 is very short, and the recovery current of the backflow prevention diode D2 no longer flows when the switching element SW is turned on. That is,
Since the carrier of the backflow prevention diode D2 is in a small state, its recovery current is so small that it does not matter, and the influence of the recovery current is not considered as much as the output rectifier diode D1.
, The increase in the loss of the switching element SW due to the recovery current does not matter.

Further, the present invention is not limited to the above-described embodiments, but includes appropriate modifications without impairing the objects and advantages thereof.

[0050]

As described above, according to the present invention, by providing a recovery current suppressing inductance large enough to suppress the recovery current in the path between the output rectifier diode and the switching element, The recovery current flowing through the output rectifier diode is reduced, thereby reducing the loss of the switching element and improving the efficiency as viewed as a power supply device.

The use of a large recovery current suppressing inductance generates a large flyback voltage when the switching element switches from on to off. However, by providing a snubber circuit in parallel with the switching element, the recovery is reduced. The flyback voltage due to the current suppressing inductance is absorbed, and a switching element having a small reverse withstand voltage can be used.

Further, by providing a snubber circuit in which a reverse current blocking diode and a capacitor are connected in series in parallel with the switching element, a sudden current change when the switching element shifts from ON to OFF causes a sudden change in magnetic flux. The area of the wiring part surrounded by the generated circuit loop decreases,
It is possible to eliminate the adverse effects of malfunctions on electronic components around the switching element and the disadvantages of increased output noise and input feedback noise when viewed as a power supply device.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a first embodiment of the present invention.

FIG. 2 is a signal waveform diagram of the switching element of FIG.

FIG. 3 is a circuit diagram of a second embodiment of the present invention.

FIG. 4 is a circuit diagram of a third embodiment of the present invention.

FIG. 5 is a circuit diagram of a fourth embodiment of the present invention.

FIG. 6 is a circuit diagram of a conventional device.

[Explanation of symbols]

L1: Chopper choke coil (chopper inductance) L2: recovery current suppression choke coil (recovery current suppression inductance) L3: energy transfer inductance D1: output rectifier diode D2: reverse current blocking diode C1: output smoothing capacitor C2: Flyback absorption capacitor SW: Switching element PG: Pulse control circuit

Claims (6)

[Claims] A current flowing during an on-period of a switching element accumulates magnetic energy in a chopper inductance, and during an off-period of the switching element, an input power supply and the energy of the chopper inductance are passed through an output rectifier to a load side. In a switching regulator power supply device using a boost chopper that shifts to an output smoothing capacitor, the output rectification is performed during a transition period in which the switching element shifts from on to off in a path from the output rectifying element to the switching element. A recovery current suppressing inductance for suppressing a recovery current flowing through the element is provided, and a diode and a capacitor for connecting a diode and a capacitor for absorbing a flyback voltage generated in the recovery current suppressing inductance during a transition period when the switching element transitions from off to on are connected. The snubber circuit is connected in parallel with the switching element, and an energy transfer path for transferring the energy stored in the capacitor of the snubber circuit from the connection point of the diode and the capacitor of the snubber circuit to the plus side of the output smoothing capacitor. A switching regulator power supply device, comprising: 2. The switching regulator power supply device according to claim 1, wherein an energy transfer inductance is inserted and connected to the energy transfer path. 3. The switching regulator power supply device according to claim 1, wherein an energy transfer resistor is inserted and connected to said energy transfer path. 4. The switching regulator power supply device according to claim 1, wherein an output capacitor side of the energy transfer path is connected between the output rectifying element and a recovery current suppressing inductance. A switching regulator power supply device characterized by the above-mentioned. 5. The switching regulator power supply according to claim 1, wherein said recovery current suppressing inductance is inserted and connected between said chopper inductance and an output rectifying element, and a positive side of said switching element is connected to said chopper. A switching regulator power supply device is connected between the switching inductance and the recovery current suppressing inductance. 6. The switching regulator power supply according to claim 1, wherein the recovery current suppressing inductance is inserted into a path connecting a connection point between the chopper inductance and an output rectifying element to a plus side of the switching element. A switching regulator power supply characterized by being connected.