Power supply circuit

Abstract

To make a current output from a plurality of circuits uniform when the current output from the plurality of circuits each including a DC-DC converter is synthesized and supplied to a load in a power supply circuit.SOLUTION: A voltage output from isolated DC-DC converters 12A, 12B is input to non-isolated DC-DC converters 13A, 13B, respectively. A synthesized current path obtained by synthesizing a current output from the non-isolated DC-DC converters 13A, 13B is output from an output unit 3. The non-isolated DC-DC converters 13A, 13B are controlled by a common control signal so that a current value Is of a composite current detected by a composite current detection unit 16 becomes a predetermined value. A voltage output from at least one of the isolated DC-DC converters 12A, 12B can be adjusted so as to reduce difference between current values Ia, Ib of the current output from the non-isolated DC-DC converter 13A, 13B and detected by individual current detection units 15A, 15B.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a power supply circuit.

Background Art

[0002] In the power supply system described in Patent Document 1, voltage is input from one power supply to a plurality of DC-DC converters. Each DC-DC converter has two FETs, and by controlling the two FETs, the voltage input from the power supply is stepped up or down. Then, the current synthesized from the currents output from these plurality of DC-DC converters is supplied to one load. Thereby, in Patent Document 1, a large current can be supplied to the load.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Here, in the power supply system of Patent Document 1, if there is a difference in the output current among a plurality of DC-DC converters, the life of the DC-DC converter with a large output current becomes short, and the life of this DC-DC converter becomes the life of the entire power supply system. Therefore, in order to extend the life of the power supply system, it is preferable that the output currents of the plurality of DC-DC converters be uniform. Thus, for example, it is conceivable to make the output currents of the plurality of DC-DC converters uniform by forming the plurality of DC-DC converters using the same type of components. However, even for components of the same type, there are slight differences in characteristics among the components. Also, there are differences in the length of the wiring for connecting to the power supply and the length of the wiring for connecting to the load among the plurality of DC-DC converters. Therefore, inevitably, there will be some difference in the output currents among the plurality of DC-DC converters.

[0005] An object of the present invention is to provide a power supply circuit capable of equalizing the output currents of a plurality of circuits each including a DC-DC converter when synthesizing the output currents of the plurality of circuits and supplying the same to a load.

Means for Solving the Problems

[0006] The power supply circuit according to the first invention includes a plurality of isolated DC-DC converters each including a switching element and outputting a voltage corresponding to the on / off switching timing of the switching element with respect to an input voltage from an external power supply, a plurality of non-isolated DC-DC converters provided individually for the plurality of isolated DC-DC converters and connected to the output of the corresponding isolated DC-DC converter, a current output unit that outputs a combined current obtained by combining the output currents of the plurality of non-isolated DC-DC converters to an external load, a combined current detection unit that detects the current value of the combined current, and a current control unit that controls each of the plurality of non-isolated DC-DC converters by a common control signal so that the current value of the combined current detected by the combined current detection unit becomes a predetermined current value. Each of the plurality of isolated DC-DC converters has a voltage adjustment unit capable of adjusting the output voltage of the isolated DC-DC converter so as to reduce the difference in the current values of the output currents of the plurality of non-isolated DC-DC converters.

[0007] According to the present invention, by adjusting the output voltage of at least one of the plurality of isolated DC-DC converters by the voltage adjustment unit, the difference in the current values of the output currents of the plurality of non-isolated DC-DC converters can be reduced. Thereby, the burden due to the flow of current can be equalized between the plurality of isolated DC-DC converters and between the plurality of non-isolated DC-DC converters.

[0008] The power supply circuit of the second invention is the power supply circuit of the first invention, wherein the voltage adjustment unit has a variable resistor, detects the voltage value of the output voltage of the isolated DC-DC converter, and outputs a voltage corresponding to the detected voltage value and the resistance value of the variable resistor. The isolated DC-DC converter controls the on / off switching of the switching element based on the output voltage value output by the voltage adjustment unit.

[0009] According to the present invention, by adjusting the resistance value of the variable resistor of the voltage adjustment unit in at least one of the plurality of isolated DC-DC converters, the difference in the current values of the output currents of the plurality of non-isolated DC-DC converters can be reduced.

[0010] The power supply circuit of the third invention is the power supply circuit of the second invention, further comprising a plurality of individual current detection units provided individually for each of the plurality of non-isolated DC-DC converters to detect the current value of the output current of the corresponding non-isolated DC-DC converter. The voltage adjustment unit can adjust the output voltage so as to reduce the difference in the current values of the output currents detected by each of the plurality of individual current detection units.

[0011] According to the present invention, by adjusting the output voltage of at least one of the plurality of isolated DC-DC converters so as to reduce the difference in the current values of the output currents of the plurality of non-isolated DC-DC converters detected by the plurality of individual current detection units, the difference in the current values of the output currents of the plurality of non-isolated DC-DC converters can be reduced.

[0012] The power supply circuit of the fourth invention is the power supply circuit of the third invention, further comprising a resistance adjustment circuit that adjusts the resistance value of the variable resistor so as to reduce the difference in the current values of the output currents of the plurality of non-isolated DC-DC converters detected by the plurality of individual current detection units.

[0013] According to the present invention, by adjusting the resistance value of the variable resistor in the resistance adjustment circuit, it is possible to reduce the difference in the current values of the output currents of a plurality of non-isolated DC-DC converters detected by a plurality of individual current detection units.

[0014] The method for adjusting the power supply circuit according to the fifth invention is a method for adjusting the power supply circuit according to the third invention, wherein the variable resistor is configured to be adjustable in resistance value from the outside, and each of the plurality of individual current detection units is detachably provided for the corresponding non-isolated DC-DC converter. The method includes: an attachment step of attaching the individual current detection unit to each of the plurality of non-isolated DC-DC converters; a resistance adjustment step of adjusting the variable resistor of the voltage adjustment unit so as to reduce the difference in the current values of the output currents of the plurality of non-isolated DC-DC converters while monitoring the current value of the output current of the corresponding non-isolated DC-DC converter detected by the individual current detection unit; and a removal step of removing the plurality of individual current detection units after the adjustment step.

[0015] After adjusting the resistance value of the variable resistor in the voltage adjustment unit of at least one isolated DC-DC converter, the plurality of individual current detection units become unnecessary in the power supply circuit. Therefore, in the present invention, individual current detection units are attached to a plurality of non-isolated DC-DC converters, and the variable resistor of the voltage adjustment unit is adjusted so as to reduce the difference in the current values of the output currents of the plurality of non-isolated DC-DC converters while monitoring the current value of the output current of the non-isolated DC-DC converter detected by the individual current detection unit, and then the plurality of individual current detection units are removed. Thereby, the configuration of the power supply circuit after the above adjustment can be simplified. In addition, the removed individual current detection unit can be used for adjusting the resistance value of the variable resistor in another power supply circuit.

Effect of the Invention

[0016] According to the present invention, by adjusting the output voltage of at least one of a plurality of isolated DC-DC converters with a voltage regulator unit, the difference in the current values of the output currents of a plurality of non-isolated DC-DC converters can be reduced. Thereby, the burden caused by the flow of current can be made uniform among a plurality of isolated DC-DC converters and among a plurality of non-isolated DC-DC converters.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0018] Hereinafter, preferred embodiments of the present invention will be described.

[0019] As shown in FIG. 1, the power supply circuit 1 of the present embodiment has an input unit 2 and an output unit 3. The input unit 2 is connected to an external AC power supply 100, and an AC voltage is input from the AC power supply 100. The output unit 3 is connected to an external load 101 and outputs a combined current described later to the load 101. The load 101 is a device that requires a relatively large current for operation, such as a medical device, an accelerator, or the like. In the present embodiment, the output unit 3 corresponds to the "current output unit" of the present invention.

[0020] In addition, the power supply circuit 1 includes a rectifying and smoothing circuit 11, isolated DC-DC converters 12A and 12B, non-isolated DC-DC converters 13A and 13B, gate drive circuits 14A and 14B, individually provided removable current detection units 15A and 15B, a combined current detection unit 16, a PWM signal generation circuit 17, and a control circuit 18.

[0021] The rectifying and smoothing circuit 11 is connected to the input unit 2. The rectifying and smoothing circuit 11 rectifies and smooths the AC voltage input to the input unit 2 by the AC power supply 100 to convert it into a DC voltage and outputs it as a DC voltage.

[0022] The isolated DC-DC converter 12A is connected to the rectifying and smoothing circuit 11, and a DC voltage is input from the rectifying and smoothing circuit 11. That is, a voltage obtained by converting the AC voltage from the AC power supply 100 into a DC voltage is input to the isolated DC-DC converter 12A via the rectifying and smoothing circuit 11. The isolated DC-DC converter 12A has a circuit including an FET 21A. The isolated DC-DC converter 12A outputs a voltage having a voltage value according to the input voltage and the timing at which the on / off of the FET 21A is switched. Since the configuration and operation of the circuit including the FET 21A in the isolated DC-DC converter 12A are the same as those in the prior art, further detailed description thereof is omitted here. In the present embodiment, the FET 21A and the FET 21B described later correspond to the "switching element" of the present invention. Further, the FET 21A and the FET 21B described later may be replaced with another switching element such as a transistor other than the FET.

[0023] The isolated DC-DC converter 12A further includes a PWM signal generation circuit 22A, an output voltage detection circuit 23A, and a control circuit 24A.

[0024] The PWM signal generation circuit 22A generates a PWM signal for switching the on / off of the FET 21A. The output voltage detection circuit 23A outputs a voltage (a signal having a voltage value) according to the voltage input to the input unit 51A described later and the resistance value of the variable resistor 53A described later.

[0025] More specifically, as shown in FIG. 2, the output voltage detection circuit 23A includes an input section 51A, an output section 52A, a variable resistor 53A, and a resistor 55A. The input voltage of the isolated DC-DC converter 12A is input to the input section 51A. The output section 52A is connected to the control circuit 24A.

[0026] The variable resistor 53A is connected between the input section 51A and the output section 52A. The resistance value of the variable resistor 53A can be changed from the outside. One end of the resistor 55A is connected between the variable resistor 53A and the output section 52A, and the other end is grounded.

[0027] Accordingly, from the output section 52A, a signal having a voltage value obtained by dividing the voltage value of the voltage input to the input section 51A by the ratio of the resistance value of the variable resistor 53A to the resistance value of the resistor 55A is output. Therefore, even if the voltage value of the voltage input to the input section 51A (the output voltage of the isolated DC-DC converter 12A) is the same, when the resistance value of the variable resistor 53A is changed, the voltage value of the signal output from the output section 52A changes. Specifically, when the voltage value of the voltage input to the input section 51A is the same, the larger the resistance value of the variable resistor 53A, the larger the ratio of the resistance value of the variable resistor 53A to the resistance value of the resistor 55A, and the lower the voltage value of the signal output from the output section 52A.

[0028] The control circuit 24A controls the PWM signal generation circuit 22A based on the voltage output from the output section 52A of the output voltage detection circuit 23A. For example, when the voltage output from the output section 52A of the output voltage detection circuit 23A is lower than a predetermined voltage value, the control circuit 24A increases the duty ratio of the PMW signal generated by the PMW signal generation circuit 22A, and when the voltage of the signal output from the output section 52A of the output voltage detection circuit 23A is higher than the predetermined voltage value, the control circuit 24A decreases the duty ratio of the PMW signal generated by the PMW signal generation circuit 22A to control the PMW signal generation circuit 22A. Thereby, the on / off switching of the FET 21A is controlled so that the voltage value of the output voltage of the isolated DC-DC converter 12A becomes the predetermined voltage value when the voltage output from the output section 52A of the output voltage detection circuit 23A is the predetermined voltage value. In the present embodiment, the combination of the output voltage detection circuit 23A and the control circuit 24A, and the combination of the output voltage detection circuit 23B and the control circuit 24B described later correspond to the "voltage adjustment unit" of the present invention.

[0029] The isolated DC-DC converter 12B is connected to the rectifying and smoothing circuit 11, and a DC voltage is input from the rectifying and smoothing circuit 11. That is, a voltage is input to the isolated DC-DC converter 12B from the AC power supply 100 via the rectifying and smoothing circuit 11.

[0030] Also, similar to the isolated DC-DC converter 12A, the isolated DC-DC converter 12B includes a circuit including the FET 21B, a PWM signal generation circuit 22B, an output voltage detection circuit 23B, and a control circuit 24B. Also, similar to the output voltage detection circuit 23A, the output voltage detection circuit 23B includes an input section 51B, an output section 52B, a variable resistor 53B, and a resistor 55B. And the voltage value of the output voltage of the isolated DC-DC converter 12B is controlled so that the voltage output from the output section 52B of the output voltage detection circuit 23B becomes the predetermined voltage value.

[0031] The non-isolated DC-DC converter 13A is connected to the isolated DC-DC converter 12A, and the output voltage of the isolated DC-DC converter 12A is input to the non-isolated DC-DC converter 13A. The non-isolated DC-DC converter 13A has an FET 31A. The gate drive circuit 14A is connected to the FET 31A and switches the on / off state of the FET 31A. Then, the non-isolated DC-DC converter 13A boosts or buck-boosts the voltage input from the isolated DC-DC converter 12A according to the switching timing of the on / off state of the FET 31A and outputs it. Note that since the configuration and operation of the non-isolated DC-DC converter 13A are the same as those of the prior art, further detailed description is omitted here.

[0032] The non-isolated DC-DC converter 13B is connected to the isolated DC-DC converter 12B, and the output voltage of the isolated DC-DC converter 12B is input to the non-isolated DC-DC converter 13B. The non-isolated DC-DC converter 13B has an FET 31B. The gate drive circuit 14B is connected to the FET 31B and switches the on / off state of the FET 31B. Then, the non-isolated DC-DC converter 13B boosts or buck-boosts the voltage input from the isolated DC-DC converter 12B according to the switching timing of the on / off state of the FET 31B and outputs it. Note that since the configuration and operation of the non-isolated DC-DC converter 13B are the same as those of the prior art, further detailed description is omitted here.

[0033] Also, the non-isolated DC-DC converters 13A and 13B are connected to a connecting portion 4 connected to the output portion 3. As a result, the current output from the output portion 3 to the load 101 is a combined current obtained by combining the output current of the non-isolated DC-DC converter 13A and the output current of the non-isolated DC-DC converter 13B. And the current value Is of the combined current output from the output portion 3 is the current value (Ia + Ib) obtained by summing the current value Ia of the output current of the non-isolated DC-DC converter 13A and the current value Ib of the output current of the non-isolated DC-DC converter 13B.

[0034] The individual current detection units 15A and 15B and the combined current detection unit 16 are existing current sensors or the like. The individual current detection unit 15A is detachably attached to the wiring connecting the non-insulated DC-DC converter 13A and the connection part 4. The individual current detection unit 15A detects the current value Ia of the output current of the non-insulated DC-DC converter 13A. The individual current detection unit 15B is detachably attached to the wiring connecting the non-insulated DC-DC converter 13B and the connection part 4. The individual current detection unit 15B detects the current value Ib of the output current of the non-insulated DC-DC converter 13B. The combined current detection unit 16 is connected between the connection part 4 and the output part 3. The combined current detection unit 16 detects the current value Is of the combined current.

[0035] The PWM signal generation circuit 17 generates a common PWM signal to output to the gate drive circuits 14A and 14B. The gate drive circuits 14A and 14B switch the on / off states of the FETs 31A and 31B based on the PWM signal input from the PWM signal generation circuit.

[0036] The control circuit 18 controls the PWM signal generation circuit 17 based on the current value Is of the combined current detected by the combined current detection unit 16. For example, when the current value Is is smaller than a predetermined current value, the control circuit 18 increases the duty ratio of the PWM signal generated by the PMW signal generation circuit 17, and when the current value Is is higher than the predetermined current value, the control circuit 18 decreases the duty ratio of the PWM signal generated by the PMW signal generation circuit 17 to control the PWM signal generation circuit 17. Thereby, the switching of the on / off states of the FETs 31A and 31B in the non-insulated DC-DC converters 13A and 13B is controlled so that the current value Is of the combined current becomes the predetermined current value. In this embodiment, the combination of the gate drive circuits 14A and 14B, the PWM signal generation circuit 17, and the control circuit 18 corresponds to the "current control unit" of the present invention.

[0037] Next, a procedure for adjusting the output voltages of the isolated DC-DC converters 12A and 12B will be described. As shown in the flowchart of FIG. 3, when adjusting the output voltages of the isolated DC-DC converters 12A and 12B, first, the individual current detectors 15A and 15B are attached to the wiring connecting the isolated DC-DC converters 12A and 12B and the combined current detector 16 in the power supply circuit 1 from which the individual current detectors 15A and 15B have been removed (S101, attachment step).

[0038] Subsequently, while the operator monitors the current values Ia and Ib of the output currents of the non-isolated DC-DC converters 13A and 13B detected by the individual current detectors 15A and 15B, at least one of the resistance values of the variable resistor 53A of the output voltage detection circuit 23A and the variable resistor 53B of the output voltage detection circuit 23B is adjusted so as to reduce the difference between the current value Ia and the current value Ib (S102, resistance adjustment step).

[0039] Here, in the present embodiment, for example, the individual current detectors 15A and 15B have a display unit that displays the detected current values Ia and Ib, and in the resistance adjustment step, the operator monitors the current values Ia and Ib displayed on the display unit of the individual current detectors 15A and 15B. Alternatively, for example, the individual current detectors 15A and 15B are connected to an external device having a display unit such as a PC (not shown), and are configured to display the detected current values Ia and Ib on the display unit of the external device, and in the resistance adjustment step, the operator monitors the current values Ia and Ib displayed on the display unit of the external device.

[0040] Also, in the resistance adjustment step, for example, when the current value Ia is smaller than half of the current value Is (= Ia + Ib) of the combined current, i.e., Is / 2, the resistance value of the variable resistor 53A is increased. In this case, the voltage of the output unit 52A decreases, and in response, as described above, the control circuit 24A controls to increase the voltage output from the output unit 52A to the predetermined voltage value. As a result, the current value Ia increases.

[0041] Also, for example, when the current value Ia is greater than half of the current value Is of the combined current, i.e., Is / 2, the resistance value of the variable resistor 53A is decreased. In this case, the voltage of the output section 52A rises. In response to this, as described above, the control circuit 24A controls to decrease the voltage output from the output section 52A to the predetermined voltage value. As a result, the current value Ia decreases.

[0042] Also, for example, when the current value Ib is less than half of the current value Is of the combined current, i.e., Is / 2, the resistance value of the variable resistor 53B is increased. In this case, the voltage of the output section 52B drops. In response to this, as described above, the control circuit 24B controls to increase the voltage output from the output section 52B to the predetermined voltage value. As a result, the current value Ib increases.

[0043] Also, for example, when the current value Ib is greater than half of the current value Is of the combined current, i.e., Is / 2, the resistance value of the variable resistor 53B is decreased. In this case, the voltage of the output section 52B rises. In response to this, as described above, the control circuit 24B controls to decrease the voltage output from the output section 52B to the predetermined voltage value. As a result, the current value Ib decreases.

[0044] And after the resistance adjustment step, the individual current detectors 15A and 15B are removed from the power supply circuit 1 (S103, removal step).

[0045] <Effect> In this embodiment, by adjusting at least one of the output voltages of the isolated DC-DC converters 12A and 12B, the difference between the current value Ia of the output current of the non-isolated DC-DC converter 13A and the current value Ib of the output current of the non-isolated DC-DC converter 13B can be reduced. As a result, the current can be made uniform between the isolated DC-DC converter 12A and the isolated DC-DC converter 12B, and between the non-isolated DC-DC converter 13A and the non-isolated DC-DC converter 13B.

[0046] Also, in this embodiment, the output voltage detection circuit 23A has a variable resistor 53A and outputs a signal having a voltage value corresponding to the voltage value of the output voltage of the isolated DC-DC converter 12A and the resistance value of the variable resistor 53A. Further, the output voltage detection circuit 23B has a variable resistor 53B and outputs a signal having a voltage value corresponding to the voltage value of the output voltage of the isolated DC-DC converter 12B and the resistance value of the variable resistor 53B. Thereby, by adjusting at least one of the resistance values of the variable resistors 53A and 53B, at least one of the output voltages of the isolated DC-DC converters 12A and 12B is adjusted, and the difference between the current value Ia of the output current of the non-isolated DC-DC converter 13A and the current value Ib of the output current of the non-isolated DC-DC converter 13B can be reduced.

[0047] Also, in this embodiment, the power supply circuit 1 is provided individually for each of the plurality of non-isolated DC-DC converters 13A and 13B, and individual current detection units 15A and 15B for detecting the current values of the output currents of the corresponding non-isolated DC-DC converters 13A and 13B are attached. Thereby, at least one of the output voltages of the isolated DC-DC converters 12A and 12B can be adjusted so as to reduce the difference between the current value Ia of the output current of the non-isolated DC-DC converter 13A detected by the individual current detection unit 15A and the current value Ib of the output current of the non-isolated DC-DC converter 13B detected by the individual current detection unit 15B. As a result, the difference between the current value Ia of the output current of the non-isolated DC-DC converter 13A and the current value Ib of the output current of the non-isolated DC-DC converter 13B can be reduced.

[0048] Also, in the power supply circuit 1, after once adjusting at least one of the resistance values of the variable resistors 53A and 53B, the individual current detection units 15A and 15B become unnecessary. Therefore, by making the individual current detection units 15A and 15B detachable from the power supply circuit 1 and removing them, the configuration of the power supply circuit 1 after the adjustment of the resistance value can be simplified. Further, the removed individual current detection units 15A and 15B can be used for adjusting at least one of the resistance values of the variable resistors 53A and 53B in another power supply circuit 1.

[0049] <Modification Example> As described above, the preferred embodiments of the present invention have been explained. However, the present invention is not limited to the above-described embodiments, and various modifications are possible as long as they are within the scope described in the claims.

[0050] In the above-described embodiment, the positions of the variable resistor 53A and the resistor 55A may be reversed. In this case, the increase and decrease of the resistance value of the variable resistor 53A in the control for reducing the difference between the current value Ia and the current value Ib are opposite to those described in the above-described embodiment. Similarly, in the above-described embodiment, the positions of the variable resistor 53B and the resistor 55B may be reversed. In this case, the increase and decrease of the resistance value of the variable resistor 53B in the control for reducing the difference between the current value Ia and the current value Ib are opposite to those described in the above-described embodiment.

[0051] Also, in the above-described embodiment, the operator adjusts at least one of the resistance values of the variable resistor 53A and the variable resistor 53B based on the current values Ia and Ib to reduce the difference between the current value Ia and the current value Ib. However, the present invention is not limited to this.

[0052] In one modification example, as shown in FIGS. 4 and 5, in addition to having the same configuration as the power supply circuit 1, the power supply circuit 201 includes a resistance adjustment circuit 202. The resistance adjustment circuit 202 is connected to the individual current detection units 15A and 15B. Here, in this modification example, the output voltage detection circuit 23A has a control signal input unit 54A connected to the variable resistor 53A, and the output voltage detection circuit 23B has a control signal input unit 54B connected to the variable resistor 53B. The resistance adjustment circuit 202 is connected to the control signal input units 54A and 54B and the individual current detection units 15A and 15B. Then, based on the current values Ia and Ib detected by the individual current detection units 15A and 15B, the resistance adjustment circuit 202 transmits a control signal to at least one of the output voltage detection circuits 23A and 23B to control at least one of the resistance values of the variable resistor 53A and the variable resistor 53B so as to reduce the difference between the current value Ia and the current value Ib.

[0053] Specifically explaining the control of the resistance value of at least one of the variable resistors 53A and 53B, when the current value Ia is smaller than the current value Is / 2 which is half of the current value Is of the combined current, the resistance adjustment circuit 202 transmits a control signal to the output voltage detection circuit 23A to increase the resistance value of the variable resistor 53A. As a result, similar to what was described in the above-described embodiment, the current value Ia increases.

[0054] Also, when the current value Ia is larger than the current value Is / 2 which is half of the current value Is of the combined current, the resistance adjustment circuit 202 transmits a control signal to the output voltage detection circuit 23A to decrease the variable resistor 53A. In this case, similar to what was described in the above-described embodiment, the current value Ia decreases.

[0055] Also, when the current value Ib is smaller than the current value Is / 2 which is half of the current value Is of the combined current, the resistance adjustment circuit 202 transmits a control signal to the output voltage detection circuit 23B to increase the variable resistor 53B. In this case, similar to what was described in the above-described embodiment, the current value Ib increases.

[0056] Also, when the current value Ib is larger than the current value Is / 2 which is half of the current value Is of the combined current, the resistance adjustment circuit 202 transmits a control signal to the output voltage detection circuit 23B to decrease the variable resistor 53B. In this case, similar to what was described in the above-described embodiment, the current value Ib decreases.

[0057] Also, in the above-described embodiment, the output voltage detection circuits 23A and 23B each included the variable resistors 53A and 53B, but this is not limiting. One of the variable resistor 53A of the output voltage detection circuit 23A and the variable resistor 53B of the output voltage detection circuit 23B may be a fixed resistor whose resistance value cannot be changed.

[0058] In the above-described embodiment, the individual current detection units 15A and 15B are removable and are removed after adjusting the resistance value of at least one of the variable resistors 53A and 53B. However, the present invention is not limited to this. The individual current detection units 15A and 15B may not be removed after adjusting the resistance value of at least one of the variable resistors 53A and 53B.

[0059] In the above-described embodiment, the power supply circuit 1 includes an isolated DC-DC converter, a non-isolated DC-DC converter, a gate drive circuit, and the number of individual current detection units is two. However, the present invention is not limited to this. The power supply circuit may include three or more isolated DC-DC converters, non-isolated DC-DC converters, gate drive circuits, and individual current detection units. In this case, the resistance value of the variable resistor of at least one of the output voltage detection circuits of the three or more isolated DC-DC converters is adjusted so that the difference between the three or more current values detected by the three or more individual current detection units becomes small.

[0060] In the above-described embodiment, at least one of the output voltages of the isolated DC-DC converters 12A and 12B is adjusted by adjusting the resistance value of at least one of the variable resistors 53A and 53B of the output voltage detection circuits 23A and 23B of the isolated DC-DC converters 12A and 12B. However, the present invention is not limited to this. At least one of the output voltages of the isolated DC-DC converters 12A and 12B may be adjusted by a method other than adjusting the resistance value of the variable resistor of the voltage detection circuit.

Description of Reference Numerals

[0061] 1: Power supply circuit 3: Output unit 12A, 12B: Isolated DC-DC converters 13A, 13B: Non-isolated DC-DC converters 14A, 14B: Gate drive circuits 15A, 15B: Individual current sensors 16: Composite current sensor 17: PWM signal generation circuit 18: Control circuit 21A, 21B: FET 22A, 22B: PWM signal generation circuit 23A, 23B: Output voltage detection circuit 24A, 24B: Control circuit 53A, 53B: Variable resistor 201: Power supply circuit 202: Resistance adjustment circuit

Claims

1. A plurality of isolated DC-DC converters, each including a switching element and outputting a voltage corresponding to the on / off switching timing of the switching element with respect to an input voltage from an external power supply; A plurality of non-isolated DC-DC converters provided individually for the plurality of isolated DC-DC converters and connected to the outputs of the corresponding isolated DC-DC converters; A current output unit that outputs a combined current obtained by combining the output currents of the plurality of non-isolated DC-DC converters to an external load; A combined current detection unit that detects the current value of the combined current; A current control unit that controls each of the plurality of non-isolated DC-DC converters by a common control signal so that the current value of the combined current detected by the combined current detection unit becomes a predetermined current value; Comprising; Each of the plurality of isolated DC-DC converters has a voltage adjustment unit capable of adjusting the output voltage of the isolated DC-DC converter so as to reduce the difference in the current values of the output currents of the plurality of non-isolated DC-DC converters. A power supply circuit characterized by that.

2. The voltage adjustment unit has a variable resistor, detects the voltage value of the output voltage of the isolated DC-DC converter, and outputs a voltage corresponding to the detected voltage value and the resistance value of the variable resistor. The isolated DC-DC converter controls the on / off switching of the switching element based on the output voltage value output by the voltage adjustment unit. The power supply circuit according to claim 1, characterized by that.

3. Further comprising a plurality of individual current detection units provided individually for each of the plurality of non-isolated DC-DC converters and detecting the current value of the output current of the corresponding non-isolated DC-DC converter. The voltage adjustment unit is capable of adjusting the output voltage so as to reduce the difference in the current values of the output currents detected by each of the plurality of individual current detection units. The power supply circuit according to claim 2, characterized by that.

4. Further comprising a resistance adjustment circuit that adjusts the resistance value of the variable resistor so as to reduce the difference in the current values of the output currents of the plurality of non-isolated DC-DC converters detected by the plurality of individual current detection units. The power supply circuit according to claim 3, characterized by that.

5. The variable resistor is configured to be able to adjust the resistance value from the outside, and The method for adjusting a power supply circuit according to claim 3, wherein each of the plurality of individual current detection units is removably provided for the corresponding non-isolated DC-DC converter, an attachment step of attaching the individual current detection unit to each of the plurality of non-isolated DC-DC converters; a resistance adjustment step of adjusting the variable resistor of the voltage adjustment unit so as to reduce the difference in the current values of the output currents of the plurality of non-isolated DC-DC converters while monitoring the current value of the output current of the corresponding non-isolated DC-DC converter detected by the individual current detection unit; and a removal step of removing the plurality of individual current detection units after the adjustment step, the method for adjusting a power supply circuit being characterized by comprising the steps.

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