Power supply system

Abstract

To ensure that there is enough time for a current caused by the back electromotive force of an inductive load to flow back into the inductive load.SOLUTION: A power supply device includes a power supply that outputs DC power, a pair of output lines, a first output line and a second output line, for supplying the DC power to an inductive load, a switch connected between the pair of output lines, and a control circuit that turns on the switch such that a current due to the back electromotive force of the inductive load flows back to the inductive load via the switch.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a power supply device and a power supply system. [Background technology]

[0002] There is known a power supply device that includes a rectifier circuit that rectifies the AC input from the secondary coil of a transformer to DC, and a smoothing circuit that smoothes the output voltage of the rectifier circuit, and supplies the smoothed voltage to a load (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-134951 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the conventional technology, when the load is an inductive load, it is difficult to ensure the time for the current caused by the back electromotive force of the inductive load to flow back to the inductive load.

[0005] The present disclosure provides a power supply device capable of ensuring time for a current caused by a back electromotive force of an inductive load to flow back to the inductive load. [Means for solving the problem]

[0006] In one aspect of the present disclosure, A power supply that outputs DC power; a pair of output lines, a first output line and a second output line, for supplying the DC power to an inductive load; a switch connected between the pair of output lines; and a control circuit that turns on the switch so that a current due to a back electromotive force of the inductive load flows back to the inductive load via the switch. Effect of the Invention

[0007] According to one aspect of the present disclosure, it is possible to ensure time for a current caused by a back electromotive force of an inductive load to flow back to the inductive load. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating an example of a configuration of a power supply device according to a first embodiment. [Diagram 2] 2 is a diagram showing a configuration example of a power supply provided in the power supply device of the first embodiment. FIG. [Diagram 3] 4 is a timing chart showing an example of operation of the power supply device according to the first embodiment. [Figure 4] FIG. 11 is a diagram illustrating an example of a configuration of a power supply device according to a second embodiment. [Diagram 5] FIG. 11 is a diagram for explaining the operation of a power supply provided in a power supply device according to the second embodiment. [Figure 6] 13A and 13B are diagrams for explaining an operation when a power supply provided in the power supply device of the second embodiment is stopped. [Figure 7] 10 is a timing chart showing an example of operation of the power supply device according to the second embodiment. [Figure 8] 1 is a diagram illustrating an example of a configuration of a power supply system according to a first embodiment. [Figure 9] FIG. 11 is a diagram illustrating an example of a configuration of a power supply system according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0010] Fig. 1 is a diagram showing an example of a configuration of a power supply device according to a first embodiment. The power supply device 101 shown in Fig. 1 supplies DC power P generated by a power supply 10 to an inductive load 201. The power supply device 101 is an inductive load power supply device for driving the inductive load 201. The inductive load 201 has an inductance component, and is, for example, a coil. The power supply device 101 is a device that is required to continuously return a current I due to a back electromotive force of the inductive load 201 to the inductive load 201 for a certain period of time or more when the power supply 10 is switched from operating (operating) to stopped (when the output of the DC power P is stopped).

[0011] The power supply device 101 includes a first output terminal 23, a second output terminal 24, a power supply 10, a first output line 21, a second output line 22, a switch 30, a filter 40, and a control circuit 50.

[0012] The first output terminal 23 is a connection terminal for electrically connecting the first output line 21 to the inductive load 201, and is electrically connected to a first end of the inductive load 201. The second output terminal 24 is a connection terminal for electrically connecting the second output line 22 to the inductive load 201, and is electrically connected to a second end of the inductive load 201. The power supply device 101 outputs DC power P from the first output terminal 23 and the second output terminal 24 to the inductive load 201.

[0013] The power supply 10 is a circuit that outputs DC power P. The power supply 10 has a first output point 27 connected to the first output line 21 and a second output point 28 connected to the second output line 22. The power supply 10 outputs DC power P from the first output point 27 and the second output point 28 to the filter 40. The power supply 10 may be a circuit that has, for example, a converter that converts AC or DC to DC, and outputs DC power P generated by the converter.

[0014] FIG. 2 is a diagram showing an example of a configuration of a power supply provided in the power supply device of the first embodiment. The power supply device 101A shown in FIG. 2 has a converter 10A which is an example of the power supply 10. The converter 10A is an insulating converter circuit including a transformer 11 and a diode bridge circuit 13. In FIG. 2, the primary side of the transformer 11 is omitted. The transformer 11 has a secondary winding 12. The diode bridge circuit 13 has a series circuit of a diode 14 and a diode 15, and a series circuit of a diode 16 and a diode 17. The midpoint between the diode 14 and the diode 15 is connected to one end of the secondary winding 12, and the midpoint between the diode 16 and the diode 17 is connected to the other end of the secondary winding 12. The diode bridge circuit 13 rectifies the AC output from the secondary winding 12 of the transformer 11 to DC and outputs DC power P.

[0015] The configuration of the power supply 10 is not limited to the converter 10A illustrated in FIG. 2. For example, the diodes 14-17 may be replaced with switching elements such as transistors. The configuration of the power supply 10 is not limited to an insulating type, and may be a non-insulating type. The method by which the power supply 10 generates the DC power P is not limited to a full-bridge type, and may be a half-bridge type.

[0016] In Fig. 1, a first output line 21 and a second output line 22 are a pair of output lines for supplying DC power P output from a power source 10 to an inductive load 201. The first output line 21 has a higher potential than the second output line 22. The second output line 22 is electrically connected to the same potential as a potential reference such as ground. The first output line 21 and the second output line 22 are paths through which a DC current passes, and are not limited to simple conductors. For example, the first output line 21 or the second output line 22 may be a conductor having a shape other than a linear shape.

[0017] The switch 30 is an element connected between a pair of output lines 21 and 22. Specific examples of the switch 30 include semiconductor switching elements such as a metal oxide semiconductor field effect transistor (MOSFET) and an insulated gate bipolar transistor (IGBT). Fig. 1 illustrates the case where the switch 30 is a field effect transistor (FET).

[0018] The switch 30 has a first main electrode electrically connected to the first output line 21 at a first connection point 25, a second main electrode electrically connected to the second output line 22 at a second connection point 26, and a control electrode electrically connected to the control circuit 50. For example, the first main electrode is a drain or collector, the second main electrode is a source or emitter, and the control electrode is a gate.

[0019] The switch 30 is a switch in which a diode 31, whose forward direction is from the second output line 22 to the first output line 21, is provided in parallel. The diode 31 is reverse-connected between the main terminals. The diode 31 may be a parasitic diode of the switch 30.

[0020] The filter 40 is a circuit that is interposed between the power source 10 and the switch 30, and smoothes and outputs the DC power P from the power source 10. The filter 40 is an LC filter that has an inductor 41 and a capacitor .

[0021] The capacitor 42 is a capacitive element connected between the pair of output lines 21, 22 between the power source 10 and the switch 30. The capacitor 42 is, for example, a polarized capacitor. Specific examples of the capacitor 42 include an electrolytic capacitor and a functional polymer capacitor. The capacitor 42 may be a non-polarized capacitor.

[0022] The inductor 41 is an inductive element inserted in series in the first output line 21 between the power supply 10 and the capacitor 42. The inductor 41 is also called a reactor.

[0023] It should be noted that the power supply device 101 does not necessarily have to include the filter 40. Moreover, the filter 40 does not necessarily have to include the inductor 41. Moreover, the filter 40 does not necessarily have to include the capacitor .

[0024] The power supply device 101 may include a reverse current prevention element 32 inserted in series in the first output line 21 between the first connection point 25 and the first output terminal 23. The reverse current prevention element 32 blocks a current (reverse current) flowing in the direction from the first output terminal 23 to the first connection point 25. The reverse current prevention element 32 is formed using, for example, a transistor or a diode. The reverse current prevention element 32 may be used as an ORing element in a configuration in which a plurality of power supply devices are connected in parallel, as described later. The reverse current prevention element 32 may be omitted.

[0025] The control circuit 50 controls the power supply 10 and the switch 30. The control circuit 50 has, for example, a processor 51 and a drive circuit 52. The processor 51 generates and outputs a command signal Sc for controlling the operation or stop of the power supply 10, and generates and outputs a command signal Sr for commanding the switch 30 to be turned on or off. The drive circuit 52 turns the switch 30 on or off in accordance with the command signal Sr from the processor 51. The drive circuit 52 turns the switch 30 on or off by controlling the gate voltage Vg of the switch 30.

[0026] The functions of the control circuit 50 are realized by a processor 51 such as a CPU (Central Processing Unit) operating according to a program stored in a memory. The functions of the control circuit 50 may be realized by a Field Programmable Gate Array (FPGA) or an Application Specific Integrated Circuit (ASIC).

[0027] When the power supply 10 is started up by an operation command from the command signal Sc, the power supply 10 generates and outputs DC power P. When the DC power P is output, the output voltage Vo, which is the voltage between the first connection point 25 of the first output line 21 and the second connection point 26 of the second output line 22 (the voltage across the capacitor 42), becomes a predetermined target voltage value while the switch 30 is off. Meanwhile, the power supply 10 stops the operation of outputting the DC power P in response to a stop command from the command signal Sc. When the operation of the power supply 10 stops, a back electromotive force is generated in the inductive load 201.

[0028] When the output voltage Vo becomes a negative voltage during a period when the power supply 10 is stopped, the control circuit 50 turns on the switch 30 so that the current I caused by the back electromotive force of the inductive load 201 flows back to the inductive load 201 via the switch 30. When the switch 30 is turned on, the current I caused by the back electromotive force of the inductive load 201 flows back to the inductive load 201 via the switch 30.

[0029] If the switch 30 and the diode 31 are not present, the current I due to the back electromotive force of the inductive load 201 flows back to the inductive load 201 via a path that passes through the second output point 28, the power supply 10, the first output point 27, and the inductor 41 in this order, and a path that passes through the second output point 28, the capacitor 42, and the first output point 27 in this order. However, when the current I flows during a period when the power supply 10 is stopped, the voltage drop from the second output point 28 to the first output point 27 via the power supply 10 corresponds to the reverse charging voltage of the capacitor 42 and is relatively large. For example, in the embodiment in FIG. 2 where the switch 30 and the diode 31 are not present, a voltage drop that is approximately equal to the sum of the forward voltages of the diodes 17 and 16 (or the forward voltages of the diodes 15 and 14) and the voltage generated in the inductor 41 occurs between the second output point 28 and the first output point 27. Therefore, the capacitor 42 is reversely charged to this voltage, and the current I of the inductive load 201 attenuates in a short time, making it difficult to continuously circulate the current I due to the back electromotive force of the inductive load 201 for a certain period of time or more.

[0030] On the other hand, in the embodiment shown in FIG. 1 or FIG. 2 in which the switch 30 is present, the switch 30 is interposed between the filter 40 and the inductive load 201, so that the path through which the current I due to the back electromotive force of the inductive load 201 flows back to the inductive load 201 is provided between the filter 40 and the inductive load 201. When the output voltage Vo becomes a negative voltage during the stop period of the power supply 10, the switch 30 is turned on by the control circuit 50. As a result, during the stop period of the power supply 10, the impedance of the path from the second connection point 26 to the first connection point 25 via the switch 30 is sufficiently smaller than the impedance of the path from the second connection point 26 to the first connection point 25 via the second output point 28, the power supply 10, the first output point 27, and the inductor 41. Therefore, during the stop period of the power supply 10, most of the current I due to the back electromotive force of the inductive load 201 flows through the path from the second connection point 26 to the first connection point 25 via the switch 30. At this time, the voltage between the first connection point 25 and the second connection point 26 becomes lower than the voltage between the first output point 27 and the second output point 28. Therefore, the back electromotive force of the inductive load 201 is clamped at a relatively small voltage (the voltage drop of the turned-on switch 30), so that the current I flowing through the inductive load 201 is prevented from immediately attenuating. As a result, it becomes easy to continuously return the current I due to the back electromotive force of the inductive load 201 to the inductive load 201 for a certain period of time or more.

[0031] In this way, the control circuit 50 in the first embodiment adjusts the gate voltage Vg of the switch 30 to turn on the switch 30 so that the current I caused by the back electromotive force of the inductive load 201 flows back to the inductive load 201 via the switch 30. This makes it possible to secure the time during which the current I caused by the back electromotive force of the inductive load 201 flows back to the inductive load 201.

[0032] Moreover, when the switch 30 is turned on, the current I generated by the back electromotive force of the inductive load 201 passes through the switch 30, so that the loss can be reduced compared to the case where the current passes through the power source 10. In other words, the temperature rise of the switch 30 can be suppressed.

[0033] 3 is a timing chart showing an example of the configuration of the power supply device of the first embodiment. The processor 51 of the control circuit 50 outputs a command signal Sr for maintaining the switch 30 off during the period in which the power supply 10 is operated. When the processor 51 of the control circuit 50 switches the command signal Sc of the power supply 10 from an operation command to a stop command at timing t1, the output (DC power P) of the power supply 10 is stopped. As a result, the output voltage Vo starts to decrease, and a counter electromotive force is generated in the inductive load 201.

[0034] In order to turn on the switch 30 after the output voltage Vo transitions from a positive voltage to a negative voltage, a period during which the output voltage Vo is a negative voltage and the switch 30 is off (dead time t2-t3) is provided. By providing the dead time t2-t3, it is possible to prevent a short circuit between the first output line 21 and the second output line 22 when the output voltage Vo is a positive voltage. The length of the dead time t2-t3 is determined taking into consideration the state of the inductive load 201, a detection delay of the output voltage Vo, etc.

[0035] When the output voltage Vo transitions from a positive voltage to a negative voltage at timing t2, a current I due to the back electromotive force of the inductive load 201 starts to flow to the diode 31. During the period in which the current I flows through the diode 31, the output voltage Vo becomes a first negative voltage lower than zero (≈zero - the forward voltage of the diode 31).

[0036] When the elapsed time from timing t1 at which the power supply 10 is switched to a stopped state reaches a first predetermined time, the control circuit 50 switches the command signal Sr for operating the switch 30 from an OFF command to an ON command (timing t3). As a result, the drive circuit 52 increases the gate voltage Vg from an OFF voltage to an ON voltage at timing t4, turning on the switch 30. As the switch 30 switches from OFF to ON, the path through which the current I passes switches from the diode 31 to the switch 30. As a result, the output voltage Vo rises to a second negative voltage slightly lower than zero (=zero-the voltage drop of the switch 30).

[0037] When the elapsed time from timing t3 at which the command signal Sr is switched from an OFF command to an ON command reaches a second predetermined time, the control circuit 50 switches the command signal Sr from an ON command to an OFF command. As a result, the drive circuit 52 reduces the gate voltage Vg from an ON voltage to an OFF voltage, and the switch 30 turns off (timing t5). As the switch 30 switches from ON to OFF, the path through which the current I passes switches from the switch 30 to the diode 31. As a result, the output voltage Vo drops from the second negative voltage to the first negative voltage.

[0038] In order to turn off the switch 30 early before the output voltage Vo transitions from a negative voltage to a positive voltage, a period during which the output voltage Vo is negative and the switch 30 is off (dead time t5-t6) is provided. By providing the dead time t5-t6, it is possible to prevent a short circuit between the first output line 21 and the second output line 22 when the output voltage Vo is a positive voltage. The length of the dead time t5-t6 is determined taking into consideration the rise speed of the output voltage Vo, the delay time from the off command of the command signal Sr until the switch 30 actually turns off, and the like.

[0039] When the elapsed time from the timing at which the command signal Sr is switched from an on command to an off command reaches a third predetermined time, the control circuit 50 switches the command signal Sc of the power source 10 from a stop command to an operation command (timing t6). When the command signal Sc is switched to an operation command, the output of the DC power P resumes, so that the output voltage Vo starts to rise and transitions from a negative voltage to a positive voltage (timing t7). Since the output voltage Vo transitions from a negative voltage to a positive voltage after the control circuit 50 switches the switch 30 from on to off, it is possible to prevent a short circuit between the first output line 21 and the second output line 22 when the output voltage Vo is a positive voltage.

[0040] 3, the control circuit 50 turns off the switch 30 when the output voltage Vo is a positive voltage, and turns on the switch 30 when the output voltage Vo is a negative voltage. This makes it possible to supply the DC power P or the power stored in the capacitor 42 to the inductive load 201 when the output voltage Vo is a positive voltage, and to ensure the time for the current I due to the back electromotive force of the inductive load 201 to flow when the output voltage Vo is a negative voltage.

[0041] 3, the control circuit 50 switches the switch 30 from off to on (t3-t5) after the output voltage Vo transitions from a positive voltage to a negative voltage (timing t2). This makes it possible to prevent a short circuit between the first output line 21 and the second output line 22 when the output voltage Vo is a positive voltage.

[0042] The control circuit 50 switches the switch 30 from off to on (t3-t5) after the current I caused by the back electromotive force of the inductive load 201 flows through the diode 31 during the period t2-t3. When the current I flows through the diode 31, the output voltage Vo becomes a negative voltage, so that it is possible to prevent a short circuit between the first output line 21 and the second output line 22 when the output voltage Vo is a positive voltage.

[0043] The control circuit 50 may turn off the switch 30 when the output voltage Vo is higher than a set voltage (negative set voltage Va) that is lower than the voltage of the second output line 22 (approximately zero volts), and may turn on the switch 30 when the output voltage Vo is equal to or lower than the set voltage Va. This turns on the switch 30 when the output voltage Vo is a negative voltage (turns off when the output voltage Vo is a positive voltage), thereby preventing a short circuit between the first output line 21 and the second output line 22 due to the switch 30 being turned on when the output voltage Vo is a positive voltage.

[0044] The control circuit 50 switches the switch 30 from on to off after the current I has continued to flow back to the inductive load 201 for a predetermined period of time or more, thereby ensuring that the current I flows back to the inductive load 201 for a predetermined period of time or more. For example, even if an instantaneous power outage occurs in the power source 10, the inductive load 201 can continue to operate while suppressing the influence of the instantaneous power outage that occurred in the power source 10 by causing the current I to flow back to the inductive load 201 for a predetermined period of time.

[0045] The dead times t2-t3 and t5-t6 are examples of a first period during which the output voltage Vo is a negative voltage and the switch 30 is off. The period up to the timing t1 and the period after the timing t6 are examples of a second period during which the power supply 10 is operating and the switch 30 is off. The period t4-t5 is an example of a third period during which the power supply 10 is stopped (the output voltage Vo is a negative voltage) and the switch 30 is on. The first period exists between the second period and the third period. The control circuit 50 may control the power supply 10 and the switch 30 so that the second period and the third period are alternately switched. In addition, the control circuit 50 may restart the power supply 10 after the power supply 10 has stopped, in a state in which the current I flowing back to the inductive load 201 becomes 0 A and the switch 30 is off, or in a state in which the output voltage Vo becomes higher than the set voltage Va and the switch 30 is off.

[0046] 4 is a diagram showing an example of the configuration of a power supply device according to the second embodiment. In the second embodiment, the description of the configuration and effects similar to those of the first embodiment will be omitted or simplified by incorporating the above description.

[0047] During the dead time, the current I flows through the diode 31, increasing the loss. In addition, when the current I flows through the diode 31, a reverse voltage due to the forward voltage of the diode 31 is applied to the polarized capacitor 42. If a reverse voltage is applied to the polarized capacitor 42, the life of the capacitor 42 may be shortened.

[0048] The power supply device 102 of the second embodiment includes a control circuit 60 capable of suppressing an increase in loss caused by the current I flowing through the diode 31 and shortening the time during which a reverse voltage is applied to the polar capacitor 42. During the period when the power supply 10 outputs DC power P and during the period when the capacitor 42 is discharging the stored power, the output voltage Vo is a positive voltage, and during the period when a back electromotive force is generated in the inductive load 201 after the discharge of the capacitor 42 is completed, the output voltage Vo is a negative voltage. Using this voltage fluctuation, the control circuit 60 automatically turns the switch 30 on and off (without the processor 51 as in the first embodiment). The power supply 10 is controlled by the processor 51 as in the first embodiment.

[0049] The control circuit 60 sets a voltage (e.g., -30 mV) slightly lower than the voltage (approximately zero volts) of the second output line 22 as the negative set voltage Va. The absolute value of the set voltage Va is lower than the forward voltage of the diode 31. The control circuit 60 feeds back the output voltage Vo of the switch 30, and upon detecting that the output voltage Vo has dropped below the set voltage Va, adjusts the gate voltage Vg of the switch 30 so that the output voltage Vo becomes equal to the set voltage Va.

[0050] 4 shows an example of the configuration of the control circuit 60. The control circuit 60 includes a voltage setting circuit 61 and a drive circuit 64.

[0051] The voltage setting circuit 61 generates a set voltage Va. The voltage setting circuit 61 generates the negative set voltage Va by dividing the negative voltage Vm between the second output line 22 and the negative power supply using resistors 62 and 63.

[0052] When the output voltage Vo is higher than the negative set voltage Va, the drive circuit 64 lowers the gate voltage Vg to turn off the switch 30, and when the output voltage Vo is equal to or lower than the set voltage Va, the drive circuit 64 raises the gate voltage Vg to turn on the switch 30. The drive circuit 64 has an operational amplifier 65, resistors 66 and 67, and a capacitor 68. The operational amplifier 65 has a non-inverting input terminal to which the negative set voltage Va is input, an inverting input terminal electrically connected to the first output line 21 via the resistor 66, and an output terminal to which the gate of the switch 30 is electrically connected.

[0053] Next, the operation of the power supply device of the second embodiment will be described with reference to Fig. 5 and Fig. 6. Fig. 5 and Fig. 6 show a power supply device 102A which is an example of the power supply device of the second embodiment. The power supply device 102A has a converter 10A which is an example of the power supply 10.

[0054] 5 is a diagram for explaining the operation of the power supply provided in the power supply device of the second embodiment. When the converter 10A starts up, the output voltage Vo gradually rises from 0V. Since the output voltage Vo is higher than the set voltage Va, a voltage higher than the set voltage Va is applied to the inverting input terminal of the operational amplifier 65. As a result, the operational amplifier 65 maintains the gate voltage Vg at the off voltage, so that the switch 30 remains off. In other words, during the period in which the DC power P generated by the converter 10A is being output, the pair of output lines 21 and 22 is not short-circuited.

[0055] 6 is a diagram for explaining the operation when the power supply provided in the power supply device of the second embodiment is stopped. When the output of the converter 10A is stopped, a counter electromotive force is generated in the inductive load 201, and the output voltage Vo gradually decreases. When the output voltage Vo decreases below the set voltage Va, the operational amplifier 65 increases the gate voltage Vg so that the output voltage Vo becomes equal to the set voltage Va. When the switch 30 is an FET, the operational amplifier 65 increases the gate voltage Vg to the saturation region of the switch 30 so that the output voltage Vo becomes equal to the set voltage Va.

[0056] In this way, the control circuit 60 in the second embodiment sets a voltage (e.g., −30 mV) slightly lower than the voltage (approximately zero volts) of the second output line 22 as the negative set voltage Va. The control circuit 60 turns off the switch 30 when the output voltage Vo is higher than the negative set voltage Va, and turns on the switch 30 when the output voltage Vo is equal to or lower than the set voltage Va. This ensures a time for the current I due to the back electromotive force of the inductive load 201 to flow back to the inductive load 201.

[0057] The operations shown in Figures 5 and 6 appear as the behavior shown in Figure 7. Figure 7 is a timing chart showing an example of the operation of the power supply device of the second embodiment.

[0058] During the period in which the power supply 10 is operated, the control circuit 60 outputs a gate voltage Vg that keeps the switch 30 off, since the output voltage Vo is higher than the negative set voltage Va. When the processor 51 switches the command signal Sc of the power supply 10 from an operation command to a stop command at timing t11, the output of the DC power P is stopped. As a result, the output voltage Vo starts to decrease, and a counter electromotive force is generated in the inductive load 201.

[0059] When the output voltage Vo falls to the negative set voltage Va, the control circuit 60 increases the gate voltage Vg so that the switch 30 turns on (timing t12). This switches the switch 30 from off to on. During the delay time from when the decreasing output voltage Vo reaches zero to when the switch 30 turns on, the current I caused by the back electromotive force of the inductive load 201 flows through the diode 31. In this way, the time during which the current I flows through the diode 31 is extremely short, so that it is possible to suppress an increase in loss due to the current I flowing through the diode 31 and to shorten the time during which a reverse voltage is applied to the polarized capacitor 42.

[0060] The control circuit 60 increases the gate voltage Vg from the off voltage to the on voltage at timing t12, turning on the switch 30. The output voltage Vo is feedback-controlled by the operational amplifier 65 so as to be equal to the set voltage Va, and therefore the output voltage Vo is maintained at the set voltage Va.

[0061] When the time elapsed from the timing of switching the command signal Sc of the power supply 10 from an operation command to a stop command reaches a predetermined time, the processor 51 switches the command signal Sc from a stop command to an operation command (timing t13). When the command signal Sc switches to an operation command, the output of the DC power P is resumed, so that the output voltage Vo starts to rise and the output voltage Vo transitions from a negative voltage to a positive voltage. When the output voltage Vo by the power supply 10 starts to rise, the output voltage Vo becomes higher than the set voltage Va, so that the control circuit 60 turns off the switch 30. It is required to turn off the switch 30 before the output voltage Vo transitions from a negative voltage to a positive voltage. Therefore, it is desirable that the operational amplifier 65 operates at a relatively high speed and has a large sink current. In addition, it is desirable that the power supply 10 performs a soft start operation to raise the output voltage Vo at a constant slope.

[0062] 7, the control circuit 60 turns off the switch 30 when the output voltage Vo is a positive voltage (higher than the set voltage Va), and turns on the switch 30 when the output voltage Vo is a negative voltage (lower than the set voltage Va). This makes it possible to supply DC power P to the inductive load 201 when the power supply 10 is operating, and ensures a time for the current I due to the back electromotive force of the inductive load 201 to flow when the power supply 10 stops operating.

[0063] In FIG. 7, the control circuit 60 switches the switch 30 from off to on (t12) after the output voltage Vo transitions from a positive voltage (a voltage higher than the set voltage Va) to a negative voltage (a voltage lower than the set voltage Va). This makes it possible to prevent a short circuit between the first output line 21 and the second output line 22 when the output voltage Vo is a positive voltage. The control circuit 60 switches the switch 30 from on to off after the current I continues to flow back to the inductive load 201 for a predetermined period of time or more and the current I becomes 0 A, thereby ensuring that the current I flows back to the inductive load 201 for a predetermined period of time or more. The control circuit 60 may control the switch 30 so that a period during which the power supply 10 is operating and the switch 30 is off and a period during which the power supply 10 is stopped and the switch 30 is on are alternately switched. In addition, the control circuit 60 may restart the power supply 10 after the power supply 10 has stopped and the current I flowing back to the inductive load 201 has become 0 A and the switch 30 has turned off, or the output voltage Vo has become higher than the set voltage Va and the switch 30 has turned off.

[0064] 8 is a diagram showing a configuration example of the power supply system of the first embodiment. In the power supply system of the first embodiment, the description of the configuration and effects similar to those of the power supply devices of the above embodiments will be omitted or simplified by incorporating the above description.

[0065] 8 shows a power supply system 103 equipped with multiple power supply devices (two power supply devices 103a and 103b in this example) in parallel. By providing multiple power supply devices in parallel that supply power to a common inductive load 201, it is possible to cope with cases where a single power supply device does not have enough power.

[0066] When multiple power supplies are provided in parallel, it is ideal to equally share the current flowing through inductive load 201 (in the case of FIG. 8, current I1 borne by power supply unit 103a = current I2 borne by power supply unit 103b). However, depending on the wiring impedance, for example, an unbalanced state may occur in which one power supply unit bears the entire load and the other power supplies bear no load (current is zero). In this case, the element through which the return current flows must be selected based on the assumption that the current will flow when the full load is applied (excessive design).

[0067] Fig. 9 is a diagram showing an example of a configuration of a power supply system according to a second embodiment that can avoid such an unbalanced state. Fig. 9 shows a power supply system 104 that includes multiple power supply devices (two power supply devices 104a and 104b in this example) in parallel.

[0068] Each of the power supply devices 104a, 104b includes a balancing circuit that increases the current I flowing through itself when the value of the current I flowing through itself is smaller than the value of the current I flowing through the other power supply devices. This makes it possible to avoid the above-mentioned unbalanced state.

[0069] When the value of the current I flowing through each of the multiple power supply devices 104a, 104b is smaller than the value of the current I flowing through the other power supply devices, each balancing circuit increases (brings closer to 0 V) ​​the set voltage Va (in this example, Va1 or Va2) of its own control circuit 60. Each balancing circuit increases the set voltage Va of its own control circuit 60, thereby increasing the current I flowing through it.

[0070] The balancing circuits of the power supply devices 104a and 104b have the same circuit configuration. The power supply device 104a includes a balancing circuit including a current detection circuit 110, an ORing circuit 111, a threshold voltage generation circuit 113, and a voltage adjustment circuit 114. The power supply device 104b includes a balancing circuit including a current detection circuit 120, an ORing circuit 121, a threshold voltage generation circuit 123, and a voltage adjustment circuit 124.

[0071] The current detection circuit 110 detects the current I1 using a shunt resistor or a current transformer, and outputs a voltage Vc1 corresponding to the current value of the current I1. The current detection circuit 120 detects the current I2 using a shunt resistor or a current transformer, and outputs a voltage Vc2 corresponding to the current value of the current I2.

[0072] The ORing circuit 111 is a voltage follower circuit with an ORing diode added thereto, and receives the voltage Vc1 as an input. The ORing circuit 121 is a voltage follower circuit with an ORing diode added thereto, and receives the voltage Vc2 as an input.

[0073] The threshold voltage generating circuit 113 includes a voltage follower circuit to which a voltage Vc1 is input, a diode that generates a voltage Vd1 by adding a forward voltage VF to the voltage Vc1 output from the voltage follower circuit, and a division circuit that generates a threshold voltage Ve1 by dividing the voltage Vd1. The threshold voltage generating circuit 123 includes a voltage follower circuit to which a voltage Vc2 is input, a diode that generates a voltage Vd2 by adding a forward voltage VF to the voltage Vc2 output from the voltage follower circuit, and a division circuit that generates a threshold voltage Ve2 by dividing the voltage Vd2.

[0074] The voltage adjustment circuit 114 has an operational amplifier that adjusts the set voltage Va1 so that the higher of the voltages Vc1 and Vc2 is equal to the threshold voltage Ve1. The voltage adjustment circuit 124 has an operational amplifier that adjusts the set voltage Va2 so that the higher of the voltages Vc1 and Vc2 is equal to the threshold voltage Ve2.

[0075] By having such a configuration, each balancing circuit can increase the current I flowing through it when the value of the current I flowing through it is smaller than the value of the current I flowing through the other power supply devices.

[0076] As described above, the embodiment has been described, but the above embodiment is presented as an example, and the present invention is not limited to the above embodiment. The above embodiment can be implemented in various other forms, and various combinations, omissions, substitutions, modifications, etc. can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the scope of the invention and its equivalents described in the claims.

[0077] For example, the switch 30 and the diode 31 may be replaced with other semiconductor elements such as a thyristor.

[0078] For example, the power supply device may be used in an industrial power supply device or an electric motor drive device, or may be used in a power supply device for mobile objects such as automobiles, ships, and railway vehicles. [Explanation of symbols]

[0079] 10 Power supply 10A Converter 11. Transformer 12 Secondary winding 21,22 Output lines 23,24 Output terminal 25,26 Connection points 27,28 Output points 30 Switch 31 Diode 32 Backflow prevention element 40 Filters 41 Inductor 42 Capacitor 50 Control circuit 51 Processors 52 Drive circuit 60 Control circuit 101,101A,102 Power supply 103,104 Power supply system 201 Inductive load

Claims

1. A power supply that outputs DC power; a pair of output lines, a first output line and a second output line, for supplying the DC power to an inductive load; a switch connected between the pair of output lines; a control circuit that turns on the switch so that a current due to a back electromotive force of the inductive load flows back to the inductive load via the switch.

2. 2. The power supply device according to claim 1, wherein the control circuit turns off the switch when an output voltage, which is a voltage between the pair of output lines, is a positive voltage, and turns on the switch when the output voltage is a negative voltage.

3. The power supply device of claim 2 , wherein the control circuit switches the switch from off to on after the output voltage transitions from a positive voltage to a negative voltage.

4. 4. The power supply device according to claim 1, wherein the control circuit turns off the switch when an output voltage, which is a voltage between the pair of output lines, is higher than a set voltage that is lower than the voltage of the second output line, and turns on the switch when the output voltage is equal to or lower than the set voltage.

5. 4. The power supply device according to claim 1, wherein the control circuit switches the switch from on to off after a period during which the current flows back to the inductive load continues for a predetermined period of time or longer.

6. 4. The power supply device according to claim 1, wherein an output voltage, which is a voltage between the pair of output lines, transitions from 0 V to a positive voltage after the control circuit switches the switch from on to off.

7. 4. The power supply device according to claim 1, wherein the control circuit turns off the switch when the power supply is operating, and turns on the switch when the power supply is stopped.

8. 8. The power supply of claim 7, wherein there is a first period during which the power supply is off and the switch is off.

9. 9. The power supply of claim 8, wherein the first period exists between a second period during which the power supply is operational and the switch is off and a third period during which the power supply is stopped and the switch is on.

10. 8. The power supply device according to claim 7, wherein a second period during which the power supply is operational and the switch is off alternates with a third period during which the power supply is stopped and the switch is on.

11. The power supply device according to claim 1 , wherein the control circuit adjusts a gate voltage of the switch so that the current flows back to the inductive load via the switch.

12. 12. The power supply device according to claim 11, wherein the switch is a switch in which a diode is provided in parallel, the diode having a forward direction from the second output line to the first output line.

13. The power supply of claim 12 , wherein the control circuit switches the switch from off to on after the current flows through the diode.

14. the control circuit turns off the switch when an output voltage, which is a voltage between the pair of output lines, is higher than a set voltage which is lower than the voltage of the second output line, and turns on the switch when the output voltage is equal to or lower than the set voltage; 14. The power supply device according to claim 13, wherein the set voltage has an absolute value lower than a forward voltage of the diode.

15. 12. The power supply of claim 11, wherein the switch is a field effect transistor.

16. The control circuit includes: a voltage setting circuit for generating the set voltage; 15. The power supply device according to claim 14, comprising: an operational amplifier having a non-inverting input terminal to which the set voltage is input, an inverting input terminal electrically connected to the first output line, and an output terminal electrically connected to a gate of the switch.

17. the power supply has a first output point connected to the first output line and a second output point connected to the second output line; the first output line has a first connection point to which one end of the switch is electrically connected; the second output line has a second connection point to which the other end of the switch is electrically connected; 4. The power supply device according to claim 1, wherein when the current flows during a period when the power supply is stopped, the voltage between the first connection point and the second connection point is lower than the voltage between the first output point and the second output point.

18. 4. The power supply device according to claim 1, wherein the power supply includes a converter that converts AC or DC to DC.

19. 20. The power supply device of claim 18, wherein the converter includes a diode bridge circuit that outputs the DC power.

20. A power supply system comprising a plurality of power supply devices according to claim 1 connected in parallel.

21. 21. The power supply system according to claim 20, wherein each of the plurality of power supply devices increases the current flowing therethrough when a value of the current flowing therethrough is smaller than a value of the current flowing through another power supply device.

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