Power supply device

Abstract

To provide a power supply device capable of performing a sufficient protection to an over-voltage generated by a resonance voltage generated when a power supply is stood.SOLUTION: An over-voltage protection circuit 5 connected to between a first DC bus 11 and a second DC bus 12 contains a semiconductor switch 52. The over-voltage protection circuit 5 performs an operation for protecting an inverter circuit 6 as a circuit device from an over-voltage when the semiconductor switch 52 is turned on. A driving circuit 9 is a circuit for driving the semiconductor switch 52. The driving circuit 9 becomes a driving available state that the semiconductor switch 52 is turned on in a first period that is from a rising start of a DC voltage in accordance with a power supply start to the power supply terminal PT to a half period of a resonator generated in a closing circuit CL containing a power supply 200, a capacitor 4, and an inductor 3 when a driving power is supplied by a power supply to a power supply terminal PT.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a power supply device that supplies power to a load. [Background technology]

[0002] Patent Document 1 (JP 2020-124104 A) discloses a power supply device, which is a type of power supply device that supplies power to a load. In the power supply device of Patent Document 1, an electrolytic capacitor may not be used as a smoothing capacitor, but a film capacitor with a smaller capacity than an electrolytic capacitor may be used. In an overvoltage protection circuit provided in a power supply device, the period from when the power is turned on until the drive circuit that drives the overvoltage protection circuit is in a state where the semiconductor switch of the overvoltage protection circuit can be turned on and off may be longer than 1 / 2 cycle of the LC resonant voltage generated across the capacitor. Summary of the Invention [Problem to be solved by the invention]

[0003] If the period from when the power is turned on until the drive circuit is in a state where it can turn the overvoltage protection circuit on and off is longer than half the LC resonance period, the overvoltage protection circuit may not be able to operate at the point when the power supply device starts up and an overvoltage occurs. In particular, in a configuration in which the power supply that supplies drive power to the drive circuit is the same as the power supply that supplies power to the power supply device, the overvoltage protection circuit may not be able to operate in time for the overvoltage state.

[0004] A problem with power supplies is providing adequate protection against overvoltages caused by resonant voltages that occur during power up. [Means for solving the problem]

[0005] A power supply device according to a first aspect includes a first DC bus to which a DC voltage is applied, a second DC bus having a lower potential than the first DC bus, and a capacitor connected between the first DC bus and the second DC bus, and converts DC power supplied to the first DC bus and the second DC bus to supply power to a load. The power supply device includes a power supply terminal, an inductor, a circuit device, an overvoltage protection circuit, and a drive circuit. The inductor is inserted in a power supply terminal to which power is supplied from a power supply, and in a wiring path from the power supply terminal to the first DC bus and the second DC bus. The circuit device is connected between the first DC bus and the second DC bus. The overvoltage protection circuit is connected between the first DC bus and the second DC bus, includes a semiconductor switch, and operates to protect the circuit device from an overvoltage when the semiconductor switch is turned on. The drive circuit is a circuit that drives the semiconductor switch. The drive circuit is supplied with drive power by supplying power to the power supply terminal, and is in a driveable state in which it can turn on the semiconductor switch during a first period from the start of the rise in DC voltage accompanying the start of power supply to the power supply terminal to half the period of resonance occurring in a closed circuit including the power supply, capacitor, and inductor.

[0006] In the power supply device of the first aspect, the overvoltage protection circuit is driven by a drive circuit that is in a driveable state in which the semiconductor switch can be turned on during a first period from when the DC voltage starts to rise to a half cycle of the resonance occurring in the closed circuit. As a result, before the circuit device becomes overvoltage due to the resonance when the DC voltage rises, the semiconductor switch of the overvoltage protection circuit is turned on to suppress the application of an overvoltage to the circuit device, thereby improving the reliability of the overvoltage protection for the power supply device.

[0007] A power supply device of a second aspect is the power supply device of the first aspect, wherein the drive circuit compares the line voltage between the first DC bus and the second DC bus with a threshold voltage that is higher than the line voltage in a stable state, and turns on the semiconductor switch when the line voltage exceeds the threshold voltage.

[0008] A power supply device according to a third aspect is the power supply device according to the first or second aspect, wherein the circuit device is an inverter circuit connected between a first DC bus and a second DC bus and including a semiconductor element.

[0009] A power supply device of a fourth aspect is a power supply device of any of the first aspect to the third aspect, comprising a first power supply circuit that supplies power to the drive circuit for a predetermined period including a first period in response to power supply to the power supply terminal, and within the first period, a first output voltage of the first power supply circuit becomes a voltage that satisfies a drivable state.

[0010] A power supply device of a fifth aspect is the power supply device of the fourth aspect, further comprising a second power supply circuit that supplies power to the drive circuit during a second period after a predetermined period, and the second power supply circuit causes a second output voltage of the second power supply circuit to reach a voltage that satisfies a drivable state after the first period and by the end of the predetermined period.

[0011] In the power supply device of the fifth aspect, a power supply circuit having a higher efficiency than the first power supply circuit is used for the second power supply circuit, thereby making it possible to reduce loss in the power supply circuits.

[0012] A sixth aspect of the power supply device is the power supply device of the fifth aspect, in which the first power supply circuit stops after the second output voltage of the second power supply circuit reaches a voltage that satisfies a drivable state.

[0013] In the power supply device of the sixth aspect, the first power supply circuit is stopped after the second output voltage of the second power supply circuit reaches a voltage that satisfies the drivable state, thereby making it possible to reduce power consumption in the first power supply circuit.

[0014] A power supply device according to a seventh aspect is the power supply device according to the fifth or sixth aspect, wherein the first power supply circuit has a smaller power capacity than the second power supply circuit.

[0015] In the power supply device of the seventh aspect, the power capacity of the first power supply circuit is reduced, thereby making it possible to reduce the cost and size of the first power supply circuit, thereby making it possible to suppress increases in cost and size of a power supply system that combines the first power supply circuit and the second power supply circuit.

[0016] The power supply device of an eighth aspect is a power supply device of any of the fifth to seventh aspects, comprising a diode having an anode to which the second output voltage of the second power supply circuit is applied and a cathode to which the first output voltage of the first power supply circuit is applied, and the drive circuit is configured to receive power from the cathode of the diode.

[0017] A power supply device of a ninth aspect is a power supply device of any of the fifth aspect to the eighth aspect, wherein the first power supply circuit includes a Zener diode and a current limiting element or a current limiting circuit, and the current limiting element or the current limiting circuit limits the current flowing through the Zener diode.

[0018] A power supply device according to a tenth aspect is the power supply device according to the ninth aspect, in which the current limiting circuit is a constant current circuit.

[0019] A power supply device of an eleventh aspect is a power supply device of any one of the first to tenth aspects, wherein the power source is an AC power source, and a rectifier that rectifies the AC voltage of the AC power source to a DC voltage is inserted in a wiring path from the power source terminal to the first DC busbar and the second DC busbar. [Brief description of the drawings]

[0020] [Figure 1] 1 is a schematic diagram showing an example of the configuration of a power supply device according to a first embodiment. [Diagram 2] 4 is a schematic diagram showing another example of the configuration of the power supply device according to the first embodiment. FIG. [Diagram 3] 4 is a schematic diagram showing another example of the configuration of the power supply device according to the first embodiment. FIG. [Figure 4] 4 is a schematic diagram showing another example of the configuration of the power supply device according to the first embodiment. FIG. [Diagram 5] 4 is a schematic diagram showing another example of the configuration of the power supply device according to the first embodiment. FIG. [Figure 6] FIG. 11 is a block diagram showing an example of a configuration of a power supply device according to a second embodiment. [Figure 7] FIG. 11 is a circuit diagram showing an example of the configuration of a power supply device according to a third embodiment. [Figure 8] 8 is a circuit diagram of a voltage detection circuit, a comparator power supply circuit, and a DC voltage comparator in FIG. 7. [Figure 9] 8 is a circuit diagram of a first power supply circuit, a second power supply circuit, and a power supply switching unit in FIG. 7. [Figure 10] FIG. 4 is a circuit diagram showing another example of the first power supply circuit. [Figure 11] FIG. 4 is a circuit diagram showing another example of the first power supply circuit. [Figure 12] FIG. 4 is a circuit diagram showing another example of the first power supply circuit. [Figure 13] FIG. 4 is a circuit diagram showing another example of the first power supply circuit. [Figure 14] FIG. 4 is a circuit diagram showing another example of the first power supply circuit. [Figure 15] 1 is a circuit diagram illustrating an example of a switching power supply. [Figure 16] FIG. 13 is a block diagram showing another example of a configuration for selecting the first power supply circuit or the second power supply circuit. [Figure 17] FIG. 8 is a circuit diagram showing an example of a drive circuit of FIG. 7. [Figure 18] 4 is a timing chart showing an example of a first output voltage of a first power supply circuit, a second output voltage of a second power supply circuit, and a stop signal. [Figure 19] FIG. 13 is a circuit diagram for explaining an example of an overvoltage protection circuit and a drive circuit of a power supply device according to a fourth embodiment. [Figure 20] FIG. 13 is a circuit diagram for explaining another example of the overvoltage protection circuit and the drive circuit of the power supply device according to the fourth embodiment. [Figure 21] FIG. 13 is a circuit diagram for explaining another example of the overvoltage protection circuit and the drive circuit of the power supply device according to the fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] First Embodiment (1) Overall structure Fig. 1 shows an example of the configuration of a power supply device 1 according to the first embodiment. The power supply device 1 in Fig. 1 includes a power supply terminal PT to which power is supplied from a power supply 200, and a first DC bus bar 11 and a second DC bus bar 12 to which a DC voltage is applied. The second DC bus bar 12 has a lower potential than the first DC bus bar. The power supply device 1 also includes a capacitor 4 connected between the first DC bus bar 11 and the second DC bus bar 12. The power supply device 1 converts the power supplied to the first DC bus bar 11 and the second DC bus bar 12, and supplies the power to a load 100.

[0022] In order to apply a DC voltage to the first DC bus bar 11 and the second DC bus bar 12, for example, as in the power supply device 1 of Fig. 1, an AC power supply is used as the power supply 200, and a rectifier 2 that rectifies the AC voltage of the power supply 200 to a DC voltage is inserted in the wiring path from the power supply terminal PT to the first DC bus bar 11 and the second DC bus bar 12. However, the power supply 200 is not limited to an AC power supply. For example, the power supply 200 may be a DC power supply. When the power supply 200 is a DC power supply, for example, the rectifier 2 is omitted.

[0023] The power supply device 1 includes an inductor 3 inserted in a wiring path from the power supply terminal PT to the first DC bus bar 11 and the second DC bus bar 12. The inductor 3 included in the power supply device 1 may be a single inductor or a plurality of inductors. In the power supply device 1 shown in FIG. 1, the inductor 3 is inserted in series in the first DC bus bar 11. Examples in which the inductor 3 is inserted in a wiring path from the power supply terminal PT to the first DC bus bar 11 and the second DC bus bar 12 are shown in FIGS. 2 to 5. For example, FIG. 2 shows an example in which the rectifier 2 is a bridge rectifier circuit that rectifies a single-phase AC current, and the inductor 3 is inserted in series in the first DC bus bar 11. The insertion position of the inductor 3 shown in FIG. 2 is the DC voltage output side of the bridge rectifier circuit that rectifies a single-phase AC current. For example, FIG. 3 shows an example in which the rectifier 2 is a bridge rectifier circuit that rectifies a three-phase AC current, and the inductor 3 is inserted in series in the first DC bus bar 11. The insertion position of the inductor 3 shown in Fig. 3 is the output side of the DC voltage of a bridge rectifier circuit that rectifies three-phase AC. Figs. 2 and 3 show an example in which the inductor 3 is inserted in a wiring path from the rectifier 2, which is located closer to the first DC bus 11 than the power supply terminal PT, to the first DC bus 11. Although Figs. 2 and 3 show an example in which the inductor 3 is inserted in the first DC bus 11, the inductor 3 may be inserted in the output side of the DC voltage of the bridge rectifier circuit and in the second DC bus 12. Furthermore, the inductor 3 may be inserted in both the input side of the AC voltage and the output side of the DC voltage of the bridge rectifier circuit.

[0024] For example, FIG. 4 shows an example in which the rectifier 2 is a bridge rectifier circuit that rectifies a single-phase AC, and the inductor 3 is disposed between the power supply terminal PT and the bridge rectifier circuit that rectifies the single-phase AC. The insertion position of the inductor 3 shown in FIG. 4 is the input side of the AC voltage of the bridge rectifier circuit that rectifies the single-phase AC. For example, FIG. 4 shows an example in which the rectifier 2 is a bridge rectifier circuit that rectifies a three-phase AC, and the inductor 3 is disposed between the power supply terminal PT and the bridge rectifier circuit that rectifies the three-phase AC. The insertion position of the inductor 3 shown in FIG. 4 is the input side of the AC voltage of the bridge rectifier circuit that rectifies the three-phase AC. FIGS. 4 and 5 show an example in which the inductor 3 is inserted in the wiring path between the rectifier 2, which is located closer to the power supply terminal PT than the first DC bus 11, and the power supply terminal PT. Note that FIG. 4 shows an example in which the inductor 3 is inserted between one of the power supply terminals PT and the rectifier 2, but two inductors 3 may be inserted between each of the power supply terminals PT and the rectifier 2. Furthermore, the inductor 3 may be inserted on both the AC voltage input side and the DC voltage output side of the bridge rectifier circuit.

[0025] The power supply device 1 shown in Fig. 1 further includes an inverter circuit 6, which is a circuit device, an overvoltage protection circuit 5, and a drive circuit 9. The inverter circuit 6, which is a circuit device, is connected between a first DC bus bar 11 and a second DC bus bar 12. Here, the inverter circuit 6 is given as an example of the circuit device, but the circuit device is not limited to the inverter circuit 6, and may be a circuit device other than the inverter circuit 6 as long as it is a circuit device that is provided with a line voltage applied between the first DC bus bar 11 and the second DC bus bar 12.

[0026] The overvoltage protection circuit 5 is connected between the first DC bus 11 and the second DC bus 12. The overvoltage protection circuit 5 includes a semiconductor switch 52. When the semiconductor switch 52 is turned on, the overvoltage protection circuit 5 operates to protect the circuit device (the inverter circuit 6 in FIG. 1) from overvoltage. The drive circuit 9 drives the semiconductor switch 52. The overvoltage protection circuit 5 turns off the semiconductor switch 52 and does not allow current to flow when the voltage is equal to or lower than a predetermined voltage at which overvoltage protection is not performed. Here, the overvoltage is a voltage at which the circuit device cannot operate normally or at which the circuit device is broken. Therefore, the above-mentioned predetermined voltage is a voltage that is smaller than the overvoltage and larger than the line voltage between the first DC bus 11 and the second DC bus 12 in a stable state. The target to be protected from overvoltage may be the capacitor 4 or the rectifier 2.

[0027] The drive circuit 9 is supplied with drive power by power supply to the power supply terminal PT. The drive circuit 9 is configured to be in a driveable state in which the semiconductor switch 52 can be turned on during a first period from when the DC voltage starts to rise with the start of power supply to the power supply terminal PT to a half period of resonance occurring in the closed circuit CL. The closed circuit CL is a closed circuit including a power supply 200, a capacitor 4, and an inductor 3. The closed circuit CL is shown by a two-dot chain line in FIG. 1.

[0028] When the supply of power to the power terminal PT starts, in the power supply device 1 of FIG. 1, the rectifier 2 starts applying a DC voltage to the first DC bus 11 and the second DC bus 12. If the amount of charge stored in the capacitor 4 is low because the supply of power to the power terminal PT has been stopped for a while, the line voltage Vb between the first DC bus 11 and the second DC bus 12 starts to rise from zero or a very small voltage when the supply of power to the power terminal PT starts. When the DC voltage applied to the first DC bus 11 and the second DC bus 12 changes in this way, series resonance occurs due to the capacitance component of the capacitor 4 and the inductance component of the inductor 3 connected in series in the closed circuit CL. In addition to the capacitor 4 and the inductor 3, the closed circuit CL also has a capacitance component, an inductance component, and a resistance component. However, the series resonance occurs because the capacitor 4 and the inductor 3 are arranged in series in the closed circuit CL.

[0029] The drive circuit 9 receives power from the first DC bus bar 11 and the second DC bus bar 12. Therefore, when the DC voltage between the first DC bus bar 11 and the second DC bus bar 12 is zero or very small and close to zero, the drive circuit 9 cannot turn on the semiconductor switch 52. This state can be said to be an inoperable state.

[0030] The series resonance occurring in the closed circuit CL when the power supply to the power supply terminal PT starts reaches a peak half the resonance period from the start of the rise of the DC voltage. Therefore, if the drive circuit 9 is in a driveable state during the first period from the start of the rise of the DC voltage to half the period of the resonance occurring in the closed circuit CL, the semiconductor switch 52 can be turned on before the voltage superimposed by the series resonance reaches a peak. As a result, the semiconductor switch 52 of the overvoltage protection circuit 5 can be turned on to prevent the inverter circuit 6, which is a circuit device, from being subjected to an overvoltage due to the resonance when the DC voltage rises. The power supply device 1 configured in this manner can improve the reliability of the overvoltage protection by the overvoltage protection circuit 5.

[0031] When the power supply 200 is an AC power supply, there are conditions that make it easy for an overvoltage to occur depending on the line voltage phase and the power supply frequency at the timing when the power supply starts up. The phase condition is near the phase where the voltage obtained by rectifying the AC power supply voltage is maximum, which is near 90° or 270° in the case of a single-phase AC power supply. Furthermore, the lower the power supply frequency is compared with the resonant frequency, the more likely it is that an overvoltage will occur near these phases. In addition, in a three-phase AC power supply, an overvoltage will occur easily when the phase voltage phase is near 30°, 90°, 150°, 210°, 270°, or 330°.

[0032] (2) Operation of the driver circuit 9 The drive circuit 9 compares the line voltage Vb between the first DC bus 11 and the second DC bus with a first threshold voltage Vt1 that is higher than the line voltage Vb in a stable state, and turns on the semiconductor switch 52 when the line voltage Vb exceeds the first threshold voltage Vt1. Here, the stable state refers to a state in which oscillations in the DC voltage caused by resonance in the closed circuit CL have converged.

[0033] (3) Example of a circuit device The circuit device is an inverter circuit 6 that is connected between a first DC bus 11 and a second DC bus 12 and includes a semiconductor element Q.

[0034] (4) Capacitor 4 The capacitor 4 does not have a capacity to smooth the voltage fluctuations occurring on the first DC bus 11 and the second DC bus 12 due to the rectifier 2, but has a capacity to suppress the voltage fluctuations occurring due to the switching of the inverter circuit 6. In other words, the capacitor 4 is provided not as a smoothing capacitor like a normal electrolytic capacitor, but to remove high-frequency components occurring in the inverter circuit 6. Therefore, the capacitance of the capacitor 4 is small. The upper limit of the capacitance of the capacitor 4 is a capacitance such that, for example, when the AC rectified by the rectifier 2 is single-phase, the maximum value of the voltage across the capacitor 4 is at least twice the minimum value. In addition, when the AC rectified by the rectifier 2 is three-phase, the power supply voltage of the power supply 200 rectified by the rectifier 2 is Vac, and the maximum power of the AC power output by the inverter circuit 6 is Pmax, the upper limit of the capacitance C of the capacitor 4 is C≦350×10-6 ×(Pmax / Vac 2 ) is given by

[0035] However, if the capacitance of capacitor 4 is very small, a very large voltage ripple occurs in capacitor 4 due to the switching of inverter circuit 6. Therefore, a capacitance is required to keep the voltage ripple within a certain range. As a guideline, the capacitance should be at least such that the ripple in the capacitor voltage caused by the switching operation of inverter circuit 6 is 1 / 10 or less of the average capacitor voltage.

[0036] (5) How to determine the time until the drive circuit 9 is ready to operate When the power is turned on, the line voltage between the first DC bus 11 and the second DC bus 12 is actually measured, and half the resonance period of the resonance phenomenon that occurs is measured.The time required to bring the drive circuit 9 into a driveable state can be determined to be a time shorter than half the measured resonance period.

[0037] Also, a parasitic inductance component usually exists between the power supply terminal PT and the power supply 200. When such a parasitic inductance component exists, the resonance period becomes longer than the resonance period of a closed circuit having only the inductor 3 and the capacitor 4. Therefore, the resonance period may be calculated from the inductance value of the inductor 3 and the capacitance value of the capacitor 4, and the time until the drive circuit 9 is made drivable may be determined so that the resonance period is half or less of the calculated resonance period. If determined in this way, the drive circuit 9 will be made drivable in a shorter time than the time determined by actual measurement as described above, but this is not a problem since it is in the direction of increasing safety.

[0038] For example, when the power supply 200 supplies a single-phase AC current to the power supply terminal PT, the resonance period T is T=2π(LC). 1 / 2 is given by the formula:

[0039] For example, when the power supply 200 supplies three-phase AC to the power supply terminal PT, the inductances of the inductors 3 of each phase arranged on the AC side of the rectifier 2 as shown in Fig. 5 are L1, L2, and L3. When the power supply is turned on, the circuit that charges the capacitor 4 becomes a closed circuit with the current path being the two phases where the line voltage between the first DC bus 11 and the second DC bus 12 is maximum. When the inductances of the inductors 3 of these two phases are L1 and L2 and the capacitance of the capacitor 4 is C, the period T of the resonance generated by the inductor 3 and the capacitor 4 is T = 2π((L1 + L2) C) 1 / 2 is given by:

[0040] <Second embodiment> (6) Overall structure An example of the configuration of a power supply device 1 according to a second embodiment is shown in Fig. 6. The power supply device 1 in Fig. 6 includes a power supply terminal PT to which power is supplied from a power supply 200, a first DC bus 11 and a second DC bus 12 to which a DC voltage is applied, an inductor 3, a capacitor 4, an inverter circuit 6 which is a circuit device, an overvoltage protection circuit 5, and a drive circuit 9. These configurations of the second embodiment shown in Fig. 6 are similar to the configurations of the first embodiment shown in Fig. 1, so a description thereof will be omitted here.

[0041] The power supply device 1 of the second embodiment includes a first power supply circuit 301 and a second power supply circuit 302. The first power supply circuit 301 and the second power supply circuit 302 are circuits that operate by receiving DC power from a first DC bus 11 and a second DC bus 12. The first power supply circuit 301 supplies power to the drive circuit 9 for a predetermined period including a first period in response to power supply to the power supply terminal PT. The second power supply circuit 302 supplies power to the drive circuit 9 for a second period after the predetermined period. In other words, the power supply device 1 switches so as to supply power from the first power supply circuit 301 to the drive circuit 9 until the predetermined period, and then supply power from the second power supply circuit 302 to the drive circuit 9 after the predetermined period.

[0042] The first power supply circuit 301 is configured so that the first output voltage output to the drive circuit 9 becomes a voltage that satisfies the drivable state within the first period. The second power supply circuit 302 outputs a second output voltage to the drive circuit 9. The first power supply circuit 301 stops after the second output voltage of the second power supply circuit 302 becomes a voltage that satisfies the drivable state. The first power supply circuit 301 has a smaller power capacity than the second power supply circuit 302. The first power supply circuit 301 is a dedicated power supply circuit that supplies power to at least the drive circuit 9 and the minimum circuits necessary for turning on and off the semiconductor switch 52. In contrast, the second power supply circuit 302 is a multi-purpose power supply circuit that supplies power to the drive circuit 9 but also to circuits other than those necessary for turning on and off the semiconductor switch 52. Since the first power supply circuit 301 is a dedicated power supply circuit that supplies power to the above-mentioned minimum circuits, it is easy to quickly raise the first output voltage.

[0043] It is also possible to configure only one power supply circuit that functions as both the first power supply circuit 301 and the second power supply circuit 302, without providing the first power supply circuit 301 as in the second embodiment. However, in that case, the one power supply circuit is configured so that the first output voltage output to the drive circuit 9 becomes a voltage that satisfies the drivable state within the first period, and is configured to supply power to circuits other than the drive circuit 9 after a predetermined period. Therefore, the one power supply circuit is inevitably a large-scale, high-performance circuit with high power consumption.

[0044] (7) Detailed configuration (7-1) Switching between the first power supply circuit 301 and the second power supply circuit 302 6 includes a power supply switching unit 303 for switching between a first power supply circuit 301 and a second power supply circuit 302. After the second output voltage of the second power supply circuit 302 reaches a voltage that satisfies a drivable state, the power supply switching unit 303 outputs a stop signal for stopping the first power supply circuit 301. Upon receiving the stop signal from the power supply switching unit 303, the first power supply circuit 301 stops outputting the first output voltage.

[0045] In order for the power supply switching unit 303 to determine the timing of stopping the first power supply circuit 301, the power supply device 1 in FIG. 6 includes a power supply circuit voltage comparator 304. The second output voltage of the second power supply circuit 302 is provided to the power supply switching unit 303 and the power supply circuit voltage comparator 304. Since the second output voltage is a voltage that satisfies the drivable state, the power supply switching unit 303 can operate with the second output voltage of the second power supply circuit 302. The power supply circuit voltage comparator 304 compares the second output voltage with a switching threshold. When the second output voltage is equal to or greater than the switching threshold, the second output voltage is a voltage that satisfies the drivable state. When the second output voltage is equal to or greater than the switching threshold, the power supply circuit voltage comparator 304 outputs a signal to stop the output of the first output voltage of the first power supply circuit 301.

[0046] The power supply device 1 includes a comparator power supply circuit 305 that supplies power to a power supply circuit voltage comparator 304 and a DC section voltage comparator 306. The comparator power supply circuit 305 receives power from a first power supply circuit 301 and a second power supply circuit 302. The comparator power supply circuit 305 first operates with the first output voltage of the first power supply circuit 301, and then operates with the second output voltage of the second power supply circuit 302 to supply power to the power supply circuit voltage comparator 304. Therefore, the power supply circuit voltage comparator 304 can operate relatively quickly compared to the case where it operates only with the second output voltage of the second power supply circuit 302 without using the first output voltage of the first power supply circuit 301.

[0047] (7-2) Switching the driver circuit 9 on and off The power supply device 1 shown in FIG. 6 includes a voltage detection circuit 8. The voltage detection circuit 8 is connected between a first DC bus 11 and a second DC bus 12. The voltage detection circuit 8 has resistors 81 and 82 connected in series between the first DC bus 11 and the second DC bus 12. The resistors 81 and 82 divide the line voltage between the first DC bus 11 and the second DC bus 12. The voltage across the resistor 81 dividing the line voltage is output to a DC voltage comparator 306. The DC voltage comparator 306 compares the line voltage with a first threshold voltage Vt1 that is higher than the line voltage in a stable state. When the line voltage becomes higher than the first threshold voltage Vt1, the DC voltage comparator 306 outputs a signal to the drive circuit 9 to turn on the semiconductor switch 52. When the line voltage is equal to or lower than the first threshold voltage Vt1, the DC section voltage comparator 306 outputs a signal to the drive circuit 9 to turn off the semiconductor switch 52.

[0048] (7-3) Overvoltage protection circuit 5 The overvoltage protection circuit 5 includes a resistor 51 and a semiconductor switch 52 connected in series to each other. One end of the resistor 51 is connected to the first DC bus 11, and the other end of the resistor 51 is connected to one end of the semiconductor switch 52. The other end of the semiconductor switch 52 is connected to the second DC bus 12. The semiconductor switch 52 is a semiconductor switch that can be freely turned on and off, and is, for example, a transistor. Examples of transistors that can be used for the semiconductor switch 52 include a bipolar transistor (BJT), an insulated gate bipolar transistor (IGBT), and a field effect transistor (FET). When the semiconductor switch 52 is an N-channel IGBT, the emitter is connected to the second DC bus 12, and the collector is connected to the other end of the resistor 51. A voltage signal for switching the overvoltage protection circuit 5 on and off is output from the drive circuit 9 to the gate of the insulated gate bipolar transistor. In the overvoltage protection circuit 5, since it is the resistor 51 that mainly consumes power, it is possible to use a semiconductor element with a smaller power capacity than in an overvoltage protection circuit that uses a Zener diode.

[0049] <Third embodiment> (8) Overall structure Fig. 7 shows an example of the configuration of a power supply device 1 according to a third embodiment. The power supply device 1 in Fig. 7 includes a power supply terminal PT to which power is supplied from a power supply 200, a first DC bus 11 and a second DC bus 12 to which a DC voltage is applied, an inductor 3, a capacitor 4, an inverter circuit 6 which is a circuit device, an overvoltage protection circuit 5, and a drive circuit 9. These configurations of the third embodiment shown in Fig. 6 are similar to the configurations of the first embodiment shown in Fig. 1.

[0050] The power supply device 1 of the third embodiment shown in Fig. 7 includes a voltage detection circuit 8, a first power supply circuit 301, a second power supply circuit 302, a power supply switching unit 303, a power supply circuit voltage comparator 304, a comparator power supply circuit 305, and a DC section voltage comparator 306. These configurations of the third embodiment shown in Fig. 7 are similar to the configurations of the second embodiment shown in Fig. 6.

[0051] (8-1) Supply of DC power to the first DC bus 11 and the second DC bus 12 A DC voltage is applied from a rectifier 2 to a first DC bus 11 and a second DC bus 12 shown in FIG. 7. The rectifier 2 shown in FIG. 7 is supplied with three-phase AC power from a power source 200. The rectifier 2 in FIG. 7 is a rectifier circuit that rectifies the three-phase AC. The rectifier circuit constituting the rectifier 2 is a three-phase bridge rectifier circuit made up of six diodes D1. Here, a three-phase bridge rectifier circuit is taken as an example of the rectifier 2, but the rectifier 2 is not limited to a three-phase bridge rectifier circuit. For example, a single-phase bridge rectifier circuit may also be used as the rectifier 2.

[0052] 7, an inductor 3 is inserted in series into the first DC bus 11. The inductor 3 is provided to reduce harmonics generated in a DC link consisting of the first DC bus 11 and the second DC bus 12. The position where the inductor 3 is inserted may be other than the position described in the first embodiment, for example, the inductor 3 may be provided in the second DC bus 12 or between the power source 200 and the rectifier 2.

[0053] In the first DC bus 11 of the power supply device 1 of FIG. 7, the rectifier 2, the inductor 3, one end of the capacitor 4, one end of the voltage detection circuit 8, one end of the overvoltage protection circuit 5, and the upper arm UA of the inverter circuit 6 are arranged in this order. In the second DC bus 12 of the power supply device 1 of FIG. 7, the rectifier 2, the other end of the capacitor 4, the other end of the voltage detection circuit 8, the other end of the overvoltage protection circuit 5, and the lower arm DA of the inverter circuit 6 are arranged in this order. A DC voltage is applied between one end and the other end of the capacitor 4 by the first DC bus 11 and the second DC bus 12. In addition, a DC voltage is applied between one end and the other end of the voltage detection circuit 8 by the first DC bus 11 and the second DC bus 12, a DC voltage is applied between one end and the other end of the overvoltage protection circuit 5, and a DC voltage is applied between the upper arm UA and the lower arm DA of the inverter circuit 6.

[0054] (8-2) Inverter circuit 6 The inverter circuit 6 shown in Fig. 7 converts DC power supplied to the first DC bus bar 11 and the second DC bus bar 12, and supplies three-phase AC power to a load 100. The load 100 shown in Fig. 7 is an inductive load. In Fig. 7, a three-phase AC motor is shown as an example of an inductive load. The inverter circuit 6 shown in Fig. 7 is a circuit that converts DC power supplied to the first DC bus bar 11 and the second DC bus bar 12 into three-phase AC power, and supplies the three-phase AC power.

[0055] The upper arm UA includes three semiconductor switches. The upper arm UA includes, for example, three transistors as the semiconductor switches. The transistors are, for example, N-channel insulated gate bipolar transistors Qup, Qvp, and Qwp as shown in FIG. 7. Hereinafter, the insulated gate bipolar transistor may be abbreviated as IGBT. The IGBTs Qup, Qvp, and Qwp each have a collector connected to the first DC bus 11, an emitter connected to the load 100, and a gate connected to the gate driver 21. The IGBTs Qup, Qvp, and Qwp are respectively connected in anti-parallel to freewheel diodes Dup, Dvp, and Dwp. In other words, the cathodes of the freewheel diodes Dup, Dvp, and Dwp are connected to the collectors of the IGBTs Qup, Qvp, and Qwp, and the anodes of the freewheel diodes Dup, Dvp, and Dwp are connected to the emitters of the IGBTs Qup, Qvp, and Qwp.

[0056] The lower arm DA includes three semiconductor switches. The lower arm DA includes, for example, three transistors as the semiconductor switches. The transistors are, for example, N-channel insulated gate bipolar transistors Qun, Qvn, and Qwn as shown in FIG. 2. The IGBTs Qun, Qvn, and Qwn have emitters connected to the second DC bus 12, collectors connected to the load 100, and gates connected to the gate driver 21. The IGBTs Qun, Qvn, and Qwn are connected in anti-parallel to freewheel diodes Dun, Dvn, and Dwn, respectively. In other words, the cathodes of the freewheel diodes Dun, Dvn, and Dwn are connected to the collectors of the IGBTs Qun, Qvn, and Qwn, respectively, and the anodes of the freewheel diodes Dun, Dvn, and Dwn are connected to the emitters of the IGBTs Qun, Qvn, and Qwn, respectively. The output from the emitter of IGBTQup and the collector of IGBTQun is applied to the U phase of the load 100. The output from the emitter of IGBTQvp and the collector of IGBTQvn is applied to the V phase of the load 100. The output from the emitter of IGBTQwp and the collector of IGBTQwn is applied to the W phase of the load 100.

[0057] (8-3) Voltage detection circuit 8 The voltage detection circuit 8 is a circuit for detecting a voltage occurring between the first DC bus bar 11 and the second DC bus bar 12. The voltage detection circuit 8 detects a line voltage occurring between the first DC bus bar 11 and the second DC bus bar 12 between the capacitor 4 and the inverter circuit 6. The voltage detection circuit 8 is a circuit including resistors 81 and 82 connected in series between the first DC bus bar 11 and the second DC bus bar 12. The voltage detection circuit 8 outputs the voltage across the resistor 81 to the DC section voltage comparator 306. The DC section voltage comparator 306 compares it with a first threshold voltage Vt1.

[0058] (8-4) Basic configuration of overvoltage protection circuit 5 The overvoltage protection circuit 5 shown in FIG. 7 is basically a circuit including a semiconductor switch 52 and a resistor 51 connected in series between the first DC bus 11 and the second DC bus 12. In FIG. 2, one end of the resistor 51 is connected to the first DC bus 11. The other end of the resistor 51 is connected to one end of the semiconductor switch 52. The other end of the semiconductor switch 52 is connected to the second DC bus 12. In FIG. 7, the resistor 51 is connected to the first DC bus 11 and the semiconductor switch 52 is connected to the second DC bus 12, but the positions of the resistor 51 and the semiconductor switch 52 can be interchanged to configure the overvoltage protection circuit 5. In the power supply device 1 in FIG. 7, the semiconductor switch 52 is an N-channel IGBT. The collector is connected to the other end of the resistor 51, the emitter is connected to the second DC bus 12, and the gate is connected to the drive circuit 9. In the overvoltage protection circuit 5, a current flows through the first current path CP1 when the semiconductor switch 52 is on. By causing a current to flow through the first current path CP1, power is consumed by the resistor 51, thereby protecting the inverter circuit 6 from an overvoltage.

[0059] (8-4-1) Detailed configuration of overvoltage protection circuit 5 The overvoltage protection circuit 5 shown in FIG. 7 further includes a diode 53 connected in anti-parallel to the resistor 51. The cathode of the diode 53 is connected to the first DC bus 11, and the anode is connected to one end of the semiconductor switch 52. When the semiconductor switch 52 is turned off, the current flowing through the first current path (the resistor 51 and the semiconductor switch 52) is interrupted. If an inductance component exists in the circuit including the overvoltage protection circuit 5, an electromotive force that generates a voltage across the resistor 51 is generated. The diode 53 clamps the voltage generated across the resistor 51 so that a large voltage is not generated across the resistor 51 when the semiconductor switch 52 is turned off. In FIG. 7, the diode 53 is provided in the overvoltage protection circuit 5, but an overvoltage protection circuit 5 that does not include the diode 53 may be used in the power supply device 1.

[0060] (8-4-2) Overvoltage protection by overvoltage protection circuit 5 The line voltage occurring between the first DC bus 11 and the second DC bus 12 is compared with a first threshold voltage Vt1 by the DC section voltage comparator 306. When the line voltage exceeds the first threshold voltage Vt1, the DC section voltage comparator 306 transmits a signal to the drive circuit 9 to turn on the semiconductor switch 52. When the semiconductor switch 52 of the overvoltage protection circuit 5 is turned on, a current flows through the first current path CP1 (resistor 51 and semiconductor switch 52) to suppress the overvoltage and protect the inverter circuit 6. When the line voltage becomes equal to or lower than a second threshold voltage Vt2 lower than the first threshold voltage Vt1, the semiconductor switch 52 is turned off and the overvoltage protection circuit 5 stops operating.

[0061] (8-4-3) Comparator power supply circuit 305 FIG. 8 shows an example of the circuit configuration of the comparator power supply circuit 305. The comparator power supply circuit 305 has resistors R1, R2, and R3 and a shunt regulator U1. As will be described later, when at least one of the first power supply circuit 301 and the second power supply circuit 302 is operating, a voltage is applied to one end of the resistor R1 from at least one of the first power supply circuit 301 and the second power supply circuit 302. For example, when application of a DC voltage to the first DC bus 11 and the second DC bus 12 starts, the first output voltage is applied from the first power supply circuit 301 first, and then the second output voltage is applied from the second power supply circuit 302. The other end of the resistor R1 is connected to the cathode of the shunt regulator U1, and the anode is connected to the common line COM. The potential of the common line COM is the same as that of the second DC bus 12. Further, the reference of the shunt regulator U1 is supplied with a voltage divided by resistors R2 and R3, which are connected in series between the other end of the resistor R1 and the common line COM. A constant voltage is generated across both ends of the shunt regulator U1 (between the cathode and anode). The value of the constant voltage generated across both ends of the shunt regulator U1 is determined by the resistors R2 and R3. A driving voltage is output to the power supply circuit voltage comparator 304 and the DC section voltage comparator 306 from the connection point between the other end of the resistor R1 and the cathode of the shunt regulator U1. Note that a Zener diode, a three-terminal regulator, or the like may be used in place of the shunt regulator in the comparator power supply circuit.

[0062] (8-4-4) Voltage detection circuit 8 Fig. 8 shows an example of a circuit configuration of the voltage detection circuit 8. The voltage detection circuit 8 shown in Fig. 8 includes a capacitor C1 in addition to the resistors 81 and 82 already described. The capacitor C1 is connected between the connection point of the resistors 81 and 82 and the second DC bus 12. The capacitor C1 has a function of removing high-frequency noise generated at the connection point of the resistors 81 and 82, for example.

[0063] (8-4-5) DC voltage comparator 306 FIG. 8 shows an example of the circuit configuration of the DC section voltage comparator 306. The DC section voltage comparator 306 shown in FIG. 8 is a hysteresis comparator using an operational amplifier U2. Although an example using the operational amplifier U2 will be described here, the DC section voltage comparator 306 can also be configured using a comparator instead of the operational amplifier U2. The DC section voltage comparator 306 includes an operational amplifier U2, resistors R5, R6, R7, R8, and R9, and capacitors C2 and C3. One end of the resistor R5 and one end of the resistor R9 are connected to the connection point between the shunt regulator U1 and the resistor R1. In other words, a constant voltage (comparator power supply voltage) is applied to one end of the resistors R5 and R9 from the comparator power supply circuit 305. The resistors R5 and R6 are connected in series with each other, and one end of the resistor R6 is connected to the other end of the resistor R5, and the other end of the resistor R6 is connected to the common line COM. A resistor R7 is connected between the connection point of the resistors R5 and R6 and the non-inverting input terminal (+) of the operational amplifier U2. As a result, the voltage obtained by dividing the output voltage of the comparator power supply circuit 305 by the resistors R5 and R6 is applied to the non-inverting input terminal (+).

[0064] In addition, a capacitor C2 is connected between the non-inverting input terminal (+) of the operational amplifier U2 and the common line COM. Furthermore, the connection point of resistors 81 and 82 is connected to the inverting input terminal (-) of the operational amplifier U2. A resistor R8 is connected between the output terminal and the non-inverting input terminal (+) of the operational amplifier U2, and a capacitor C3 is connected in parallel to the resistor R8. The other end of the resistor R9 is connected to the output terminal of the operational amplifier U2. The capacitor C3 is intended to adjust the transient waveform of the voltage when the voltage at the non-inverting input terminal (+) of the operational amplifier U2 changes due to hysteresis operation, and its presence or absence can be selected as necessary.

[0065] The DC section voltage comparator 306 outputs a high-level signal to the drive circuit 9 when the voltage of the non-inverting input terminal (+) becomes higher by a predetermined value than the voltage at the connection point of the resistors 81 and 82. The DC section voltage comparator 306 outputs a low-level signal to the drive circuit 9 when the voltage of the non-inverting input terminal (+) becomes lower by a predetermined value than the voltage at the connection point of the resistors 81 and 82. A voltage higher by a predetermined value than the voltage of the non-inverting input terminal (+) becomes a first threshold voltage Vt1 for determining whether or not to turn on the semiconductor switch 52 of the overvoltage protection circuit 5. A voltage lower by a predetermined value than the voltage of the non-inverting input terminal (+) becomes a second threshold voltage Vt2 for determining whether or not to turn off the semiconductor switch 52 of the overvoltage protection circuit 5.

[0066] (8-4-6) Power supply switching section 303 Fig. 9 shows an example of the circuit configuration of the power supply switching unit 303. The power supply switching unit 303 shown in Fig. 9 includes a resistor R10, a photocoupler Ph1, and a switch unit SW1. In the power supply switching unit 303, the resistor R10, the light-emitting diode of the photocoupler Ph1, and the switch unit SW1 are connected in series between the output terminal of the second power supply circuit 302 and the common line COM. A signal output by the power supply circuit voltage comparator 304 is provided to the switch unit SW1. The output signal of the power supply circuit voltage comparator 304 is a signal for causing the power supply switching unit 303 to output a stop signal.

[0067] When the output signal of power supply circuit voltage comparator 304 becomes high level, switch unit SW1 turns on and current flows through resistor R10 and the light-emitting element of photocoupler Ph1. When the output signal of power supply circuit voltage comparator 304 becomes low level, switch unit SW1 turns off and no current flows through the light-emitting element. When current flows through the light-emitting element, the light-receiving element of photocoupler Ph1 (between the two output terminals) becomes conductive. When the light-receiving element of photocoupler Ph1 becomes conductive, the first power supply circuit 301 stops.

[0068] (8-4-7) 1st power supply circuit 301 Fig. 9 shows an example of the circuit configuration of the first power supply circuit 301. The first power supply circuit 301 shown in Fig. 9 includes a constant current circuit 307, a Zener diode Z1 for limiting the operating voltage, a capacitor C4, and a Zener diode Z2 for the gate drive power supply. The output terminal of the photocoupler Ph1 is connected to the constant current circuit 307. When the photocoupler Ph1 is conductive, the constant current circuit 307 does not operate, and when the photocoupler Ph1 is non-conductive, the constant current circuit 307 operates, and a first output voltage is output from the first power supply circuit 301.

[0069] A constant current circuit 307, a Zener diode Z1, and a Zener diode Z2 are connected in series between the first DC bus 11 and the second DC bus 12. A capacitor C4 is connected in parallel to the Zener diode Z2. The Zener diodes Z1 and Z2 are connected such that their cathodes are at a higher potential than their anodes. The constant current circuit 307 is a current limiting circuit that limits the current flowing through the Zener diodes Z1 and Z2. The constant current circuit 307 and the Zener diodes Z1 and Z2 are connected in series with each other. When the constant current circuit 307 is operating, a first output voltage is output from the connection point between the anode of the Zener diode Z1 and the cathode of the Zener diode Z2. The cathode of the Zener diode Z2 is connected to the drive circuit 9.

[0070] Here, the breakdown voltage VZ2 of the Zener diode Z2 becomes the first output voltage of the first power supply circuit that becomes ready to drive. If the voltage of capacitor C4 is zero when the power is turned on, the time Δt1 required for the voltage of capacitor C4 to reach VZ2 can be expressed by the relationship Δt1 = CC4 VZ2 / IC1, where IC1 is the current of the constant current circuit and CC4 is the capacitance of capacitor C4. Therefore, by setting the capacitance CC4 to the minimum capacitance required for the drive circuit, it is possible to reduce the startup time or required current of the first output voltage.

[0071] (8-4-7-1) One configuration example of the constant current circuit 307 FIG. 9 shows an example of the circuit configuration of the constant current circuit 307. The constant current circuit 307 shown in FIG. 9 includes resistors R11 and R12, a shunt regulator U3, a MOS transistor Tr1, and a diode D2. One end of the resistor R11 is connected to the first DC bus 11, and the other end of the resistor R11 is connected to the cathode of the shunt regulator U3. The anode of the shunt regulator U3 is connected to the cathode of the Zener diode Z1. The drain of the MOS transistor Tr1 is connected to the first DC bus 11, and the source of the MOS transistor is connected to one end of the resistor R12. The other end of the resistor R12 is connected to the anode of the shunt regulator U3 (the cathode of the Zener diode Z1). The reference of the shunt regulator U3 is connected to the source of the MOS transistor Tr1. The gate of the MOS transistor Tr1 is connected to the anode of the shunt regulator U1. The cathode of the diode D2 is connected to the drain of the MOS transistor Tr1, and the anode of the diode D2 is connected to the source of the MOS transistor Tr1. The two output terminals of the photocoupler Ph1 are connected to the anode and cathode of the shunt regulator U3.

[0072] When the two output terminals of photocoupler Ph1 are non-conductive, the voltage generated between the anode and cathode of shunt regulator U3 is applied between the gate and source of MOS transistor Tr1, turning MOS transistor Tr1 on. A constant current flows between the drain and source of MOS transistor Tr1, which is in the conductive state, and the current flowing between the drain and source flows into the cathode of Zener diode Z1 through resistor R12.

[0073] When the two output terminals of the photocoupler Ph1 are in a conductive state, no voltage is generated between the anode and cathode of the shunt regulator U3, so the MOS transistor Tr1 is turned off. Therefore, the constant current passing through the MOS transistor Tr1 is cut off. The cathode of the Zener diode Z1 is connected to the first DC bus 11 through the resistor R1 and the output terminal of the photocoupler Ph1. However, the resistance value of the resistor R11 is much larger than the resistance value of the resistor R12, and the current flowing through the resistor R11 is extremely small. Therefore, the output power of the first power supply circuit 301 supplied from both ends of the Zener diode Z2 also becomes extremely small, and the circuit is put into a non-operating state.

[0074] (8-4-7-2) Other Configuration Examples of the First Power Supply Circuit 301 FIG. 10 shows another example of the circuit configuration of the first power supply circuit 301. The first power supply circuit 301 includes a resistor 14, a Zener diode Z1, a capacitor C4, and a Zener diode Z2 for a gate drive power supply, as shown in FIG. 10. The resistor R14, the Zener diode Z1, and the Zener diode Z2 are connected in series between the first DC bus 11 and the second DC bus 12. The Zener diode Z2 is connected in parallel to the capacitor C4. The Zener diodes Z1 and Z2 are connected in the reverse direction. The resistor 14 is a current limiting element that limits the current flowing through the Zener diodes Z1 and Z2. The resistor 14 and the Zener diodes Z1 and Z2 are connected in series with each other. A first output voltage is output from the connection point between the anode of the Zener diode Z1 and the cathode of the Zener diode Z2. The cathode of the Zener diode Z2 is connected to the drive circuit 9.

[0075] (8-4-7-3) Other Configuration Examples of the First Power Supply Circuit 301 FIG. 11 shows another example of the circuit configuration of the first power supply circuit 301. The first power supply circuit 301 shown in FIG. 11 includes a constant current circuit 307, a Zener diode Z1, a capacitor C4, and a Zener diode Z2 for a gate drive power supply, similar to the first power supply circuit 301 shown in FIG. 9. The first power supply circuit 301 in FIG. 11 differs from the first power supply circuit 301 in FIG. 9 in that a Zener diode Z3 is used instead of the shunt regulator U3. The cathode of the Zener diode Z3 is connected to the other end of the resistor R11 and the gate of the MOS transistor Tr1. The anode of the Zener diode Z3 is connected to the other end of the resistor R12 and the cathode of the Zener diode Z1. A constant current flows through the MOS transistor Tr1 and the resistor R12 due to a constant voltage generated across the Zener diode Z3. When the two output terminals of the photocoupler Ph1 of the power supply switching unit 303 become conductive, the constant current circuit 307 stops operating, and when the output terminals are non-conductive, the constant current circuit 307 operates, similar to the first power supply circuit 301 of Figure 9.

[0076] 12, 13, and 14, the first power supply circuit 301 may be obtained by removing the Zener diode Z1 from the first power supply circuit 301 shown in FIGS. 9, 10, and 11 and connecting the part where the Zener diode Z1 is removed by wiring. However, when the Zener diode Z1 is not present, a current flows through the first power supply circuit 301 from a state where the DC voltage is lower than when the Zener diode Z1 is present, and the power consumption of the first power supply circuit 301 increases. The parts of the first power supply circuit 301 shown in FIGS. 12, 13, and 14 that are indicated by the same reference numerals as those of the first power supply circuit 301 shown in FIGS. 9, 10, and 11 are the same.

[0077] (8-4-8) Second power supply circuit 302 FIG. 9 shows an example of the circuit configuration of the second power supply circuit 302. The second power supply circuit 302 shown in FIG. 9 includes a diode D3, a resistor R13, an electrolytic capacitor C5, and a switching power supply SM. The diode D3, the resistor R13, and the electrolytic capacitor C5 are connected in series between the first DC bus 11 and the second DC bus 12. The diode D3, the resistor R13, and the electrolytic capacitor C5 form a primary circuit of the switching power supply. The anode of the diode D3 is connected to the first DC bus 11, and the cathode of the diode D3 is connected to one end of the resistor R13. The other end of the resistor R13 is connected to one end of the electrolytic capacitor C5, and the other end of the electrolytic capacitor C5 is connected to the second DC bus 12. The voltage generated across the electrolytic capacitor C5 is applied to the switching power supply SM, and the switching power supply SM generates a second output voltage between the second DC bus 12 and the output terminal SMo. Regarding the diode D3, if fluctuations in the DC voltage do not pose a problem for the operation of the switching power supply SM, the diode D3 may be omitted and the resistor R13 may be directly connected to the first DC bus 11. Also, the resistor R13 may be a PTC (Positive Temperature Coefficient) thermistor.

[0078] (8-4-8-1) Switching power supply SM An example of the circuit configuration of a switching power supply SM is shown in Fig. 15. The switching power supply SM shown in Fig. 15 is a flyback converter. The switching power supply SM includes a transformer T1, a control circuit CC1, a switch unit SW2, a diode D5, and an electrolytic capacitor C6. A closed circuit including the electrolytic capacitor C5 and the switch unit SW2 is formed on the primary side of the transformer T1. By turning the switch unit SW2 on and off, a pulse voltage is generated, and an AC voltage is generated on the secondary side of the transformer.

[0079] In FIG. 15, only the power supply output necessary for turning on and off the semiconductor switch 52 is shown on the secondary side of the transformer T1. However, it is also possible to have a plurality of power supply outputs as power supplies for circuits other than those necessary for overvoltage protection, such as the gate driver 401 for the inverter circuit 6.

[0080] (8-4-9) Selection of outputs of the first power supply circuit 301 and the second power supply circuit 302 FIG. 9 shows an example of a circuit configuration for selecting the output of the first power supply circuit 301 and the second power supply circuit 302. The circuit for selecting the output of the first power supply circuit 301 and the second power supply circuit 302 is composed of a diode D4. The diode D4 has an anode to which the second output voltage of the second power supply circuit 302 is applied and a cathode to which the first output voltage of the first power supply circuit 301 is applied. The drive circuit 9 receives power from the cathode of the diode D4. In order to select the output of the first power supply circuit 301 and the second power supply circuit 302 and provide it to the drive circuit 9 with a simple configuration of one diode D4, the first output voltage of the first power supply circuit 301 and the second output voltage of the second power supply circuit 302 are set as follows. When the first power supply circuit 301 is operating, the first output voltage of the first power supply circuit is set to be larger than the second output voltage of the second power supply circuit 302. Therefore, when the first power supply circuit 301 is operating, the diode D4 is reverse biased, and the first output voltage of the first power supply circuit 301 is applied to the drive circuit 9. When the operation of the first power supply circuit 301 is stopped, in other words, when the constant current circuit 307 is stopped, the second output voltage of the second power supply circuit 302 becomes larger than the first output voltage of the first power supply circuit 301. Therefore, when the operation of the first power supply circuit 301 is stopped, the diode D4 is forward biased (the second output voltage becomes larger than the first output voltage), and the second output voltage of the second power supply circuit 302 is applied to the drive circuit 9.

[0081] As shown in FIG. 16, the power supply circuit may be selected by a select switch SSW that switches between the first power supply circuit 301 and the second power supply circuit 302. The select switch SSW connects the first power supply circuit 301 and the drive circuit 9 when the power supply is not turned on. The select switch SSW also connects the second power supply circuit 302 and the drive circuit 9 during the period when the second power supply circuit 302 supplies power to the drive circuit 9. The power supply used to switch the select switch SSW may be the second output voltage of the second power supply circuit 302 or another output voltage of the second power supply circuit 302. However, when the select switch SSW is configured to switch between the first power supply circuit 301 and the second power supply circuit 302, the first power supply circuit 301 operates even when the second power supply circuit 302 is connected to the drive circuit 9, so that the loss is larger than when the first power supply circuit 301 is stopped.

[0082] A closed circuit including a diode D5 and an electrolytic capacitor C6 is formed on the secondary side of the transformer T1. The AC voltage generated on the secondary side of the transformer T1 is half-wave rectified by the diode D5 and smoothed by the electrolytic capacitor C6. The voltage across the electrolytic capacitor C6 is the second output voltage of the second power supply circuit 302.

[0083] (8-4-10) Controller 400 and gate driver 401 The power supply device 1 shown in FIG. 7 includes a controller 400 and a gate driver 401. The gate driver 401 is a circuit that outputs drive signals to the gates of the IGBTs Qup, Qvp, Qwp, Qun, Qvn, and Qwn. The controller 400 includes the power circuit voltage comparator 304, the DC section voltage comparator 306, and the microcomputer 320, which have already been described. The gate driver 401 is controlled by the microcomputer 320. The microcomputer 320 also controls the drive circuit 9. The microcomputer 320 includes a control arithmetic device and a storage device. A processor such as a CPU can be used for the control arithmetic device. The control arithmetic device reads a program stored in the storage device, and controls a predetermined device and circuit and performs data calculations according to the program. Furthermore, the control arithmetic device can write the calculation results to the storage device and read information stored in the storage device according to the program.

[0084] (8-4-11) Drive circuit 9 Fig. 17 shows an example of the circuit configuration of the drive circuit 9. The drive circuit 9 shown in Fig. 17 includes a gate driver integrated circuit U4 and resistors R18 and R19. The first output voltage of the first power supply circuit 301 or the second output voltage of the second power supply circuit 302 is applied to a VDD terminal of the gate driver integrated circuit U4. The GND terminal of the gate driver integrated circuit U4 is connected to a common line COM.

[0085] The output terminal of the gate driver integrated circuit U4 is connected to one end of a resistor R18, and the other end of the resistor R18 is connected to the semiconductor switch 52. A resistor R19 is connected between the other end of the resistor R18 and the common line COM. When the on / off signal of the DC voltage comparator 306 is at a low level, the output terminal of the gate driver integrated circuit U4 becomes a high level, and the semiconductor switch 52 turns on. When the on / off signal of the DC voltage comparator 306 is at a high level, the output terminal of the gate driver integrated circuit U4 becomes a low level, and the semiconductor switch 52 turns off. When the output terminal of the gate driver integrated circuit U4 is at a high level, the output voltage is approximately the same voltage as the VDD terminal. Therefore, the gate voltage when the semiconductor switch 52 is turned on is approximately the same voltage as the VDD terminal.

[0086] (8-4-12) Stop signal output by power supply switching unit 303 18 shows the stop signal output by the power supply switching unit 303, the first output voltage of the first power supply circuit 301, and the second output voltage of the second power supply circuit 302. As shown in Fig. 9 and Fig. 17, the output of the first power supply circuit 301 and the output of the second power supply circuit 302 are connected via a diode D4. Therefore, even if the first power supply circuit 301 stops operating, the first output voltage of the first power supply circuit 301 does not become lower than the first output voltage of the second power supply circuit 302.

[0087] In FIG. 18, the power supply is turned on at time t1, and the power supply from the power supply 200 to the power supply terminal PT is started. With the start of the power supply from the power supply 200 to the power supply terminal PT, the first output voltage of the first power supply circuit 301 and the second output voltage of the second power supply circuit 302 start to rise. The first output voltage of the first power supply circuit 301 rises rapidly, and at time t2, it becomes a voltage that can put the drive circuit 9 in a drivable state in which the semiconductor switch 52 can be turned on. However, at this time, the second output voltage of the second power supply circuit 302 has not yet reached a voltage that can put the drive circuit 9 in a drivable state. After a while, at time t3, the second output voltage of the second power supply circuit 302 reaches a voltage that can put the drive circuit 9 in a drivable state. The power supply switching unit 303 outputs a stop signal to the first power supply circuit 301 at time t4 when the second output voltage after time t3 sufficiently exceeds the voltage that can put the drive circuit 9 in a drivable state.

[0088] In the third embodiment, the first output voltage of the first power supply circuit 301 or the second output voltage of the second power supply circuit 302 is applied to the VDD terminal of the gate driver integrated circuit U4, and is output as a high-level voltage of the gate driver integrated circuit U4. Furthermore, the voltage output from the gate driver integrated circuit U4 is applied to the gate of the semiconductor switch 52. When the semiconductor switch 52 is an N-channel IGBT, the voltage applied to the gate must be large enough so that the collector-emitter voltage does not become excessive due to the collector current flowing when the IGBT is turned on. If the gate voltage is insufficient, the collector-emitter voltage becomes large, and the loss increases, leading to thermal destruction of the semiconductor switch. Therefore, in the third embodiment, the voltage that can put the drive circuit 9 into a drivable state can be rephrased as a voltage that can turn on the semiconductor switch without thermal destruction.

[0089] <Fourth embodiment> (9) Overall structure An example of the configuration of the power supply device 1 according to the fourth embodiment is shown in Fig. 19. The power supply device 1 in Fig. 19 includes a power supply terminal PT to which power is supplied from a power supply 200, a first DC bus 11 and a second DC bus 12 to which a DC voltage is applied, an inductor 3, a capacitor 4, an inverter circuit 6 which is a circuit device, an overvoltage protection circuit 5, and a drive circuit 9. In the configuration of the power supply device 1 of the fourth embodiment, the power supply terminal PT to which power is supplied from the power supply 200, the first DC bus 11 and the second DC bus 12 to which a DC voltage is applied, the inductor 3, the capacitor 4, and the inverter circuit 6 are configured in the same manner as the power supply device 1 of the first embodiment, so that a description thereof will be omitted here.

[0090] (10) Detailed configuration (10-1) Overvoltage protection circuit 5 The overvoltage protection circuit 5 of the fourth embodiment shown in Fig. 19 includes a resistor R20 and an NPN bipolar transistor (BJT) Tr2. The overvoltage protection circuit 5 is a series circuit of the resistor R20 and the bipolar transistor Tr2. One end of the resistor R20 is connected to the first DC bus 11, and the other end of the resistor R20 is connected to the collector of the bipolar transistor Tr2. The emitter of the bipolar transistor Tr2 is connected to the second DC bus 12, and the base is connected to the anode of the Zener diode Z4. In the overvoltage protection circuit 5 of Fig. 19, the bipolar transistor Tr2 is a semiconductor switch 52.

[0091] (10-2) Drive circuit 9 The drive circuit 9 of the fourth embodiment shown in Fig. 19 includes a resistor R21 and a Zener diode Z4. The drive circuit 9 is a series circuit of the resistor R21 and the Zener diode Z4. One end of the resistor R21 is connected to the first DC bus 11, and the other end of the resistor R21 is connected to the cathode of the Zener diode Z4. The anode of the Zener diode Z4 serves as the output terminal of the overvoltage protection circuit 5. The output terminal of the drive circuit 9 is connected to the base of the bipolar transistor Tr2.

[0092] The Zener voltage of Zener diode Z4 becomes the threshold voltage that turns on bipolar transistor Tr2, which is semiconductor switch 52, during overvoltage protection. Resistor R21 of drive circuit 9 is selected so that a necessary current flows through bipolar transistor Tr2 of semiconductor switch 52 during overvoltage protection.

[0093] According to the voltage rise of the DC section (first DC bus 11 and second DC bus 12), the bipolar transistor Tr2 can be brought into a driveable state by 1 / 2 resonance period of the closed circuit CL, and overvoltage protection can be performed. The resistor R21, which is a current limiting element, may be replaced with the constant current circuit 307 shown in FIG. 9 and FIG. 11 (see FIG. 20). In the constant current circuit 307 in FIG. 20, the parts indicated by the same reference numerals as those in the constant current circuit 307 shown in FIG. 9 are the same. Furthermore, by providing a drive circuit 9 using the second power supply circuit 302 in a stable state, it is possible to drive with reduced power consumption (see FIG. 21). In the drive circuit 9 in FIG. 21, the parts indicated by the same reference numerals as those in the power supply switching section 303 and the constant current circuit 307 shown in FIG. 9 are the same. A voltage is applied to the bipolar transistor Tr2 from the second power supply circuit 302 through a diode D6. Moreover, a second power supply circuit 302 is connected to one terminal of the resistor R10, and a photocoupler Ph1 is connected to the other terminal of the resistor R10. In this case, a circuit that supplies a drive current using a current limiting element (resistor R20) or a constant current circuit 307 and a Zener diode Z4 performs the same function as the first power supply circuit 301.

[0094] (11) Features (11-1) In the power supply device 1 of the first to third embodiments, the drive circuit 9 is in a drivable state in which the semiconductor switch 52 can be turned on during a first period from when the DC voltage applied to the first DC bus 11 and the second DC bus 12 starts to rise to a half cycle of the resonance occurring in the closed circuit CL (see FIG. 1). In the power supply device 1, the overvoltage protection circuit 5 is driven by such a drive circuit 9. Before the inverter circuit 6, which is a circuit device, becomes overvoltage due to the resonance when the DC voltage applied to the first DC bus 11 and the second DC bus 12 rises, the semiconductor switch 52 of the overvoltage protection circuit 5 can be turned on. As a result, it is possible to suppress the overvoltage from being applied to the inverter circuit 6, and improve the reliability of the overvoltage protection for the power supply device 1.

[0095] (11-2) The power supply device 1 of the second or third embodiment includes a second power supply circuit 302 that supplies power to the drive circuit 9 during a second period after a predetermined period. In FIG. 18, the first power supply circuit 301 stops at time t4 after the second output voltage of the second power supply circuit 302 becomes a voltage that satisfies the drivable state. In FIG. 18, the predetermined period is a period from time t2 to time t4. The period after time t4 is the second period, and after time t4, the second power supply circuit 302 substantially supplies power to the drive circuit 9. By stopping the first power supply circuit 301 after the second output voltage of the second power supply circuit 302 becomes a voltage that satisfies the drivable state, it is possible to reduce the power consumption of the first power supply circuit 301. In particular, in the power supply device 1 having the configuration as shown in FIG. 9, the power consumption of the first power supply circuit 301 can be kept to a necessary minimum.

[0096] (11-3) In the power supply device 1 of the second or third embodiment, the power capacity of the first power supply circuit 301 dedicated to the drive circuit 9 is smaller than the power capacity of the second power supply circuit. By reducing the power capacity of the first power supply circuit 301, it is possible to shorten the period until the first output voltage of the first power supply circuit 301 reaches a voltage that satisfies the drivable state.

[0097] (11-4) In the power supply device 1 of the third embodiment, the output of the first power supply circuit 301 and the output of the second power supply circuit 302 are connected via the diode D4 as shown in Fig. 9, so that the length of the period until the first power supply circuit 301 becomes operable in the first period can be prevented from being affected by the electrolytic capacitor C6 (see Fig. 15) on the output side of the second power supply circuit 302. Specifically, the power supply device 1 of the third embodiment can prevent an increase in the rise time of the output voltage of the first power supply circuit 301 caused by charging the electrolytic capacitor C6 in addition to the capacitor C4.

[0098] (12) Variations (12-1) Variation A In the third embodiment, as shown in Fig. 10, a resistor R14 is used as the current limiting element. However, the current limiting element is not limited to a resistor. For example, a varistor or a PTC (Positive Temperature Coefficient) thermistor can be used as the current limiting element.

[0099] (12-2) Variation B In the third embodiment, as shown in Fig. 9 and Fig. 11, the constant current circuit 307 is used as the current limiting circuit. However, the current limiting circuit is not limited to the constant current circuit. For example, the current limiting circuit may be a current clamp circuit.

[0100] (12-3) Variation C In the above first to third embodiments, the inverter circuit 6 has been described as an example of a circuit device. However, the circuit device is not limited to the inverter circuit 6. The circuit device may be, for example, a DC-DC converter. In this case, the load is a DC load.

[0101] Although the embodiments of the present disclosure have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the present disclosure described in the claims. [Explanation of symbols]

[0102] 1 Power supply device 2 rectifier 3. Inductor 4 Capacitors 5. Overvoltage protection circuit 6 Inverter circuit (example of circuit device) 9 Drive circuit 11 1st DC bus 12 2nd DC bus 52 Semiconductor Switch 301 1st power supply circuit 302 2nd power supply circuit 307 Constant current circuit (example of current limiting circuit) D4 Diode PT power terminal R14 Resistor (example of current limiting element) Z1, Z2 Zener diode [Prior art documents] [Patent documents]

[0103] [Patent Document 1] JP 2020-124104 A

Claims

1. A power supply device comprising: a first DC bus (11) to which a DC voltage is applied; a second DC bus (12) having a lower potential than the first DC bus; and a capacitor (4) connected between the first DC bus and the second DC bus, and configured to convert power supplied to the first DC bus and the second DC bus and supply the power to a load, a power supply terminal (PT) to which power is supplied from a power supply; an inductor (3) inserted in a wiring path from the power supply terminal to the first DC bus and the second DC bus; a circuit device (6) connected between the first DC bus and the second DC bus; an overvoltage protection circuit (5) connected between the first DC bus and the second DC bus, including a semiconductor switch (52), and operating to protect the circuit device from an overvoltage when the semiconductor switch is turned on; A drive circuit (9) for driving the semiconductor switch; Equipped with the drive circuit is supplied with drive power by power supply to the power supply terminal, and is in a drivable state in which the semiconductor switch can be turned on during a first period from when the DC voltage starts to rise due to the start of power supply to the power supply terminal to when a half cycle of resonance occurs in a closed circuit including the power supply, the capacitor, and the inductor; a first power supply circuit (301) that supplies power to the drive circuit for a predetermined period including the first period in response to the supply of power to the power supply terminal; a second power supply circuit (302) that supplies power to the drive circuit during a second period after the predetermined period; Further equipped with the first power supply circuit is configured such that a first output voltage of the first power supply circuit becomes a voltage that satisfies the drivable state within the first period, the second power supply circuit causes a second output voltage of the second power supply circuit to become a voltage that satisfies the drivable state after the first period and by the end of a predetermined period; Power supply device (1).

2. the drive circuit compares a line voltage between the first DC bus and the second DC bus with a threshold voltage that is higher than the line voltage in a stable state, and turns on the semiconductor switch when the line voltage exceeds the threshold voltage.

2. The power supply device (1) according to claim 1.

3. The circuit device is an inverter circuit (6) connected between the first DC bus and the second DC bus and including a semiconductor element. A power supply device (1) according to claim 1 or claim 2.

4. the first power supply circuit is stopped after the second output voltage of the second power supply circuit becomes a voltage that satisfies the drivable state.

2. The power supply device (1) according to claim 1.

5. The first power supply circuit has a smaller power capacity than the second power supply circuit.

2. The power supply device (1) according to claim 1.

6. a diode (D4) having an anode to which the second output voltage of the second power supply circuit is applied and a cathode to which the first output voltage of the first power supply circuit is applied; The drive circuit is configured to receive power from the cathode of the diode.

2. The power supply device (1) according to claim 1.

7. The first power supply circuit includes a Zener diode (Z2) and a current limiting element (R14) or a current limiting circuit (307), The current limiting element or the current limiting circuit limits a current flowing through the Zener diode.

2. The power supply device (1) according to claim 1.

8. The current limiting circuit is a constant current circuit (307).

8. Power supply device (1) according to claim 7.

9. The power source is an AC power source, and a rectifier (2) that rectifies the AC voltage of the AC power source to the DC voltage is inserted in a wiring path from the power source terminal to the first DC bus bar and the second DC bus bar. A power supply device (1) according to claim 1 or claim 2.

Images