JP6371226B2 - Switching power supply with reverse current protection - Google Patents

Description

  The present invention relates to a switching power supply that is operated in parallel redundant operation, and relates to a switching power supply with reverse current protection that has a function of protecting an internal circuit from a reverse current from another switching device connected in parallel.

  A power supply system having a parallel redundant configuration in which a plurality of power supply devices are connected in parallel is used as a power supply for a load (for example, a server system, a storage system, and a communication device) that is required to stably operate stably (for example, Patent Document 1). reference). In the power supply system of the parallel redundant configuration, the output current from each power supply device is controlled to be equal by the current balance function, but there is a region where the current balance function does not work. For example, when the load becomes lighter, the current does not decrease equally, and the output current of the power supply apparatus varies. As a result, a reverse current is generated from the power supply apparatus having a high output voltage to the power supply apparatus having a low output voltage.

  In order to prevent the reverse current from flowing into the internal circuit, a blocking diode is generally provided at the output of each power supply device. In recent years, where high efficiency is strongly demanded, ORing FETs with less power loss have been used in place of blocking diodes. An amplifier or a control IC that turns off the ORing FET when the source-drain voltage exceeds a set voltage is added to the ORING FET. Thus, when a reverse current is generated, the ORing FET is turned off, and the internal circuit is protected.

JP 2007-221880 A

  In order to further increase the efficiency, an ultra-low on-resistance ORing FET has been developed. When the on-resistance is minimized, it becomes difficult to generate a potential difference between the source and drain of the ORing FET, and it becomes difficult to detect a reverse current by an amplifier or a control IC. The use of a high-precision amplifier or control IC increases the cost.

  The present invention has been made in view of such a situation, and an object of the present invention is to provide a technology for protecting an internal circuit from a reverse current at a low cost while minimizing power loss in a switching power supply device operated in parallel redundant operation. There is.

  One embodiment of the present invention is a switching power supply with reverse current protection. This device is a switching power supply device operated in parallel redundant operation, and an ORING semiconductor switch is connected to the output of this switching power supply device. A control circuit for turning off the semiconductor switch is added to the semiconductor switch when the voltage across the semiconductor switch becomes equal to or higher than a set voltage. The switching power supply includes a DC-DC converter, a voltage monitoring unit that monitors an input voltage of the DC-DC converter, and stops the switching operation of the DC-DC converter for a predetermined time when the input voltage exceeds a set value. A control unit.

  Another aspect of the present invention is also a switching power supply with reverse current protection. This device is a switching power supply device operated in parallel redundant operation, and an ORING semiconductor switch is connected to the output of this switching power supply device. A control circuit for turning off the semiconductor switch is added to the semiconductor switch when the voltage across the semiconductor switch becomes equal to or higher than a set voltage. The switching power supply includes a DC-DC converter, a discharge circuit for discharging the charge accumulated on the primary side of the DC-DC converter, a voltage monitoring unit that monitors an input voltage of the DC-DC converter, And a controller that discharges the charge from the discharge circuit when the input voltage exceeds a set value.

  According to the present invention, an internal circuit can be protected from a reverse current at a low cost while minimizing power loss in a switching power supply that is operated in parallel redundant operation.

It is a figure which shows the structure of the power supply system which concerns on embodiment of this invention. It is a figure which shows the structural example of the switching power supply device which concerns on embodiment of this invention. It is a figure which shows the structural example of an insulation type DC-DC converter. It is a figure which shows the structure of the switching power supply device which should be compared with FIG. FIGS. 5A and 5B are waveform diagrams showing an operation when a reverse current is generated. It is a figure which shows the structural example of the switching power supply device which concerns on a modification.

  FIG. 1 is a diagram showing a configuration of a power supply system 1 according to an embodiment of the present invention. The power supply system 1 includes a plurality of switching power supply devices 10 connected in parallel. In FIG. 1, for simplification, a configuration in which two switching power supply devices 10 are connected in parallel is illustrated, but a configuration in which three or more switching power supply devices 10 are connected in parallel may be used. An AC voltage is input in parallel from the AC power supply 2 to the two switching power supply devices 10. The outputs of the two switching power supply devices 10 are combined into one and connected to the load 3. Therefore, the sum of the output currents of the two switching power supply devices 10 becomes the input current supplied to the load 3.

  In the above configuration, when the balance of the output currents of the two switching power supply devices 10 in the light load region is lost, a part of the output current of one switching power supply device 10 flows back to the output terminal of the other switching power supply device 10. Will do. As a countermeasure, an ORing FET (M1) is connected to the output of the switching power supply device 10 in FIG. An n-channel type MOSFET is used for the ORing FET (M1), the source terminal is connected to the switching power supply device 10 side, and the drain terminal is connected to the load 3 side.

  An amplifier AP1 is added to the ORing FET (M1). In the example shown in FIG. 1, the non-inverting input terminal of the amplifier AP1 and the source terminal of the ORing FET (M1) are connected, the inverting input terminal of the amplifier AP1 and the drain terminal of the ORing FET (M1) are connected, and the output terminal of the amplifier AP1. And the gate terminal of the ORing FET (M1). Therefore, when the source-drain voltage of the ORing FET (M1) becomes equal to or higher than the set voltage, the output of the amplifier AP1 changes from high level to low level, and the gate of the ORing FET (M1) is turned off. Thereby, the reverse current from the other switching power supply apparatus 10 is interrupted. As described above, when a reverse current is generated from another switching power supply device 10, the drain voltage increases, and the ORing FET (M1) is turned off.

  In addition, although the example using MOSFET as an element for backflow suppression was demonstrated, you may use the other semiconductor element with the same electric current interruption function. Further, although an example in which the amplifier AP1 is added as it is as an element for controlling the ORing FET (M1) has been described, a control IC having a similar source-drain voltage detection function and gate control function may be used.

  When the ORing FET (M1) is connected to the output of the switching power supply device 10, a loss occurs due to the ON resistance of the ORing FET (M1). In recent years, in order to reduce this loss, an ultra-low on-resistance ORing FET having an on-resistance of 1 mΩ or less has been developed. For example, when the on-resistance is 1 mΩ, the source-drain voltage is 100 mV even when a current of 100 A flows. Therefore, if the offset of the amplifier AP1 is taken into consideration, a considerably high-spec amplifier AP1 is required. The switching power supply device 10 according to the present embodiment described below shows a technique for effectively protecting an internal circuit from a reverse current without using a high-spec amplifier AP1.

  FIG. 2 is a diagram illustrating a configuration example of the switching power supply device 10 according to the embodiment of the present invention. The switching power supply device 10 includes a rectifier circuit 20, a PFC (Power Factor Correction) circuit 30, a capacitor C 1, an insulation type DC-DC converter 40, a control unit 50, and a voltage monitoring circuit 60. The control unit 50 includes a PFC controller 51, a converter controller 52, a sequencer 53, and a timer 54.

  The rectifier circuit 20 is configured by a diode bridge circuit, for example, and rectifies an AC voltage supplied from the AC power supply 2. The PFC circuit 30 is composed of, for example, a boost chopper and improves the power factor. The capacitor C1 smoothes the output voltage of the PFC circuit 30. The insulation type DC-DC converter 40 converts the smoothed voltage into a DC voltage having a set value.

  FIG. 3 is a diagram illustrating a configuration example of the insulation type DC-DC converter 40. The insulated DC-DC converter 40 includes a bridge circuit 41, a transformer 42, a rectifier circuit 43, a smoothing circuit 44, and an output voltage detection circuit 45. The bridge circuit 41 converts the input DC voltage into an AC voltage and supplies it to the primary coil of the transformer 42.

  In the bridge circuit 41, a first arm in which a first switching element S1 and a second switching element S2 are connected in series, and a third switching element S3 and a fourth switching element S4 are connected in series between a power supply line and a ground line. This is an H-bridge circuit configured by connecting second arms in parallel. The midpoint of the first arm is connected to one end of the primary coil of the transformer 42, and the midpoint of the second arm is connected to the other end of the primary coil of the transformer 42.

  MOSFETs or IGBTs can be used for the first switching element S1 to the fourth switching element S4. The first switching element S1 to the fourth switching element S4 are respectively formed or connected in parallel with a first diode D1 to a fourth diode D4 that conduct in the direction from the source to the drain. Note that a p-channel MOSFET may be used for the first switching element S1 and the third switching element S3 on the high side.

  The transformer 42 includes a primary coil and a secondary coil. The transformer 42 insulates the primary side and the secondary side and transforms according to the winding ratio of the primary coil and the secondary coil. The rectifier circuit 43 rectifies the AC voltage input from the secondary coil of the transformer 42 into a DC voltage. The smoothing circuit 44 smoothes the output voltage of the rectifier circuit 43. The smoothed voltage is supplied to the load 3 via the ORing FET (M1) in FIG.

  The output voltage detection circuit 45 detects the output voltage of the insulated DC-DC converter 40 and outputs it to the converter controller 52. The converter controller 52 generates a gate signal to be supplied to the control terminals of the first switching element S1 to the fourth switching element S4 constituting the bridge circuit 41. Specifically, when a forward current is supplied to the primary coil of the transformer 42, a gate signal for turning on the first switching element S1 and the fourth switching element S4 and turning off the second switching element S2 and the third switching element S3. Is generated. The converter controller 52 supplies the generated gate signal to the control terminals of the first switching element S1 to the fourth switching element S4.

  When a reverse current is supplied to the primary coil of the transformer 42, a gate signal for turning off the first switching element S1 and the fourth switching element S4 and turning on the second switching element S2 and the third switching element S3 is generated. The converter controller 52 supplies the generated gate signal to the control terminals of the first switching element S1 to the fourth switching element S4.

  The converter controller 52 supplies a PWM signal to the control terminals of the two switching elements that form the current path of the primary coil of the transformer 42. Converter controller 52 adaptively changes the duty ratio of the switching element during the ON period in accordance with the voltage value from output voltage detection circuit 45. Thereby, the output voltage of the insulation type DC-DC converter 40 is kept constant.

  Converter controller 52 receives a current balance signal from a current detector (not shown). The current detection device monitors the input current of the load 3 and outputs a current value obtained by dividing the input current by the parallel number of the switching power supply devices 10 to the converter controller 52 of each switching power supply device 10. Converter controller 52 adaptively changes the duty ratio of the switching element during the ON period in accordance with the current value indicated by the current balance signal.

  In the above description, an example in which the configuration of the inverter on the primary side of the insulated DC-DC converter 40 is configured by a full bridge circuit is shown, but other configurations such as a half bridge circuit may be adopted. Moreover, although the example which controls the duty ratio of a switching element was shown as output adjustment of the insulation type DC-DC converter 40, you may control a phase difference.

  Returning to FIG. The PFC controller 51 performs switching control of switching elements included in the boost chopper used as the PFC circuit 30.

  The voltage monitoring circuit 60 monitors the input voltage Vint of the isolated DC-DC converter 40. The voltage monitoring circuit 60 supplies the detected input voltage Vint to the timer 54. When the input voltage Vint exceeds the set value, the timer 54 outputs an OFF signal for stopping the operation of the PFC controller 51 and the converter controller 52 to the sequencer 53 for a predetermined time. The sequencer 53 stops the oscillation of the PFC controller 51 and the converter controller 52 during the period when the OFF signal is input from the timer 54. When the operation of the isolated DC-DC converter 40 is stopped, the operation of the amplifier AP1 is also stopped.

  FIG. 4 is a diagram showing a configuration of the switching power supply device 10 to be compared with FIG. FIG. 4 shows a conventional configuration in which the voltage monitoring circuit 60 and the timer 54 are not provided, and there is no mechanism for stopping the operation of the isolated DC-DC converter 40 according to the input voltage Vin.

  FIGS. 5A and 5B are waveform diagrams showing an operation when a reverse current is generated. FIG. 5A shows a waveform diagram in the conventional configuration shown in FIG. 4, and FIG. 5B shows a waveform diagram in the configuration according to the present embodiment shown in FIG. When a reverse current is generated from another switching power supply device 10, the load current becomes negative. A reverse current flows from the load side to the inside until the amplifier AP1 reacts, and the input voltage Vint of the insulated DC-DC converter 40 increases due to the reverse current. In the conventional configuration, as shown in FIG. 5A, before the amplifier AP1 detects the reverse current, there is a case where the breakdown voltage of the internal component occurs.

  As shown in FIG. 5B, in the configuration according to the present embodiment, when the input voltage Vint exceeds the set value, the timer 54 reacts and the output of the timer 54 changes from the high level to the low level. The level is output to the sequencer 53. As a result, the operation of the insulation type DC-DC converter 40 is stopped for a certain time. The converter controller 52 stops the switching control, for example, controls the second switching element S2 and the fourth switching element S4 to be in an ON state, and releases the energy accumulated in the primary coil of the transformer 42 to the ground line. Even if the first switching element S1 to the fourth switching element S4 are all controlled to be in the OFF state, the energy accumulated in the primary coil of the transformer 42 is released to the power supply line via the first diode D1 and the third diode D3. Good. The time for stopping the switching operation by the timer 54 is set to a time derived from experiment, simulation, or knowledge of the designer.

  When the switching operation of the isolated DC-DC converter 40 is stopped, the backflow from the other switching power supply device 10 is eliminated, and the internal components are protected.

  The set value is set to be equal to or lower than the withstand voltage of the used component (eg, MOSFET) on the primary side of the isolated DC-DC converter 40. As a result, it is possible to release energy accumulated on the primary side before the component exceeds the pressure resistance. In the conventional configuration, there is no mechanism of energy release based on the set value. Therefore, when the sensitivity of the amplifier AP1 is low, a case where current interruption is delayed as shown in FIG. 5A occurs.

  As described above, according to the present embodiment, by using the low on-resistance ORing FET (M1), power loss during parallel redundant operation can be minimized. When the on-resistance of the ORing FET (M1) is low, the amount of reverse current until reaching the set detection voltage of the amplifier AP1 and the control IC increases, and the amount of energy regenerated to the primary side also increases.

  On the other hand, in the present embodiment, a voltage monitoring circuit 60 and a timer 54 are provided, and a mechanism for releasing energy from the primary side when the primary side voltage exceeds a set value is introduced. Thereby, it is possible to prevent the internal circuit from withstanding voltage due to the reverse current. In other words, regardless of the characteristic variation of the amplifier AP1, the voltage increase in the internal circuit due to the reverse current can be suppressed by the set value of the input voltage Vint. Therefore, a highly reliable power supply system 1 can be constructed. Further, it is not necessary to configure the amplifier AP1 and the primary side parts with high specifications, so that the cost can be reduced.

  The present invention has been described based on the embodiments. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are also within the scope of the present invention. is there.

  In the configuration shown in FIG. 2, when the input voltage Vint exceeds the set value, the operation of the PFC circuit 30 is stopped in addition to the operation of the isolated DC-DC converter 40. In this regard, if the operation of the insulated DC-DC converter 40 is stopped, the operation stop of the PFC circuit 30 is not essential. For example, a configuration in which the output of the timer 54 is directly supplied to the converter controller 52 is also possible.

  FIG. 6 is a diagram illustrating a configuration example of the switching power supply device 10 according to the modification. In the modification, energy is discharged from the primary side of the insulated DC-DC converter 40 by the discharge circuit. In the modification, a discharge circuit is connected in parallel with the capacitor C1. For example, as shown in FIG. 6, the discharge circuit can be constituted by a series circuit of a resistor R1 and a switch S5. The control unit 50 includes a discharge control circuit 55. The discharge control circuit 55 controls the switch S5 to be in an ON state during a period when the OFF signal is input from the timer 54, and releases energy accumulated on the primary side from the discharge circuit. The same effect as the configuration of FIG. A configuration in which the configuration of FIG. 6 and the configuration of FIG. 2 are used together is also possible.

  DESCRIPTION OF SYMBOLS 1 Power supply system, 2 AC power supply, 3 Load, 10 Switching power supply device, M1 ORing FET, AP1 amplifier, C1 capacitor | condenser, R1 resistance, S1 1st switching element, S2 2nd switching element, S3 3rd switching element, S4 4th Switching element, S5 switch, 20 rectifier circuit, 30 PFC circuit, 40 insulation type DC-DC converter, 41 bridge circuit, 42 transformer, 43 rectifier circuit, 44 smoothing circuit, 45 output voltage detection circuit, 50 control unit, 51 PFC controller , 52 converter controller, 53 sequencer, 54 timer, 55 discharge control circuit, 60 voltage monitoring circuit.

Claims (3)

A switching power supply unit operated in parallel redundant operation,
Is connected to a low on-resistance of the FET for Oaringu between the output and the load of the switching power supply apparatus, on the FET, the source of the FET - amplifier to the drain voltage exceeds the setting voltage off the FET or Control IC is added,
This switching power supply
A DC-DC converter;
A voltage monitoring unit for monitoring an input voltage of the DC-DC converter;
A controller that stops the switching operation of the DC-DC converter for a predetermined time when the input voltage exceeds a set value;
A switching power supply with reverse current protection, comprising:   2. The switching power supply with reverse current protection according to claim 1, wherein the set value is set to be equal to or lower than a withstand voltage of a component used on a primary side of the DC-DC converter. A switching power supply unit operated in parallel redundant operation,
Is connected to a low on-resistance of the FET for Oaringu between the output and the load of the switching power supply apparatus, on the FET, the source of the FET - amplifier for turning off the voltage between the drain becomes equal to or higher than the set voltage the FET Or a control IC is added,
This switching power supply
A DC-DC converter;
A discharge circuit for discharging the charge accumulated on the primary side of the DC-DC converter;
A voltage monitoring unit for monitoring an input voltage of the DC-DC converter;
A controller that discharges the charge from the discharge circuit when the input voltage exceeds a set value;
A switching power supply with reverse current protection, comprising:

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