Power supply device

Abstract

To reduce a variation in voltage of DC buses due to the regenerative electric power and power consumption of a load device and stably maintain the voltage of the DC buses without greatly increasing a circuit scale.SOLUTION: When the voltage of DC buses 20a, 20b exceeds an overvoltage threshold Vth1, an overvoltage protection circuit 23a stops power supply from a power supply device 2 to a motor 4. A switch Q1 and a resistance R1 are connected with the DC buses 20a, 20b. When the voltage of the DC buses 20a, 20b exceeds a discharge threshold Vth3, a discharge control circuit 26 controls the switch Q1 to consume the power of the DC buses 20a, 20b to reduce the voltage of the DC buses 20a, 20b.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a power supply device.

Background Art

[0002] When a load device includes a motor, the regenerative power generated by the motor may flow into the circuit in front of it (such as a motor controller, a power supply device, etc.). For example, Patent Document 1 discloses a DC stabilized power supply system that absorbs power fluctuations and maintains power quality when regenerative power is generated by a motor.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When regenerative power is generated by a motor, the voltage of the DC bus of the circuit in front of it, for example, the power supply device, may increase. Usually, when the voltage of the DC bus increases, the power supply device determines that further power supply is unnecessary and stops the operation of the circuit (for example, the switching operation of the inverter). If the power consumption of the load device suddenly increases during the period when the operation of the circuit is stopped, it takes time to respond until the power required for the load device is supplied, and the voltage of the DC bus may decrease. Therefore, even when the regenerative power and power consumption of the load device fluctuate suddenly, it is required to reduce the fluctuation of the voltage of the DC bus and stably maintain the voltage of the DC bus.

[0005] In order to reduce fluctuations in the voltage of the DC bus caused by the regenerative power and power consumption of the load device, for example, it is conceivable to connect a large number of capacitors to the DC bus. However, in this case, the size of the power supply device increases in order to mount a large number of capacitors. Further, since the regenerative power is simply received by the capacitor, the voltage of the DC bus itself rises, and fluctuations in the voltage of the DC bus cannot be sufficiently reduced.

[0006] An object of the present disclosure is to provide a power supply device that can reduce fluctuations in the voltage of the DC bus caused by the regenerative power and power consumption of the load device and stably maintain the voltage of the DC bus without significantly increasing the circuit scale.

Means for Solving the Problems

[0007] According to the power supply device according to one aspect of the present disclosure, a power supply device that supplies DC power to a load device, a DC bus connected to the load device, an overvoltage protection circuit that stops power supply from the power supply device to the load device when the voltage of the DC bus exceeds a predetermined overvoltage threshold value, a discharge circuit connected to the DC bus, a discharge control circuit that controls the discharge circuit so as to consume the power of the DC bus and lower the voltage of the DC bus when the voltage of the DC bus exceeds a discharge threshold value that is higher than the target voltage of the DC bus and lower than the overvoltage threshold value.

[0008] Thereby, it is possible to reduce fluctuations in the voltage of the DC bus caused by the regenerative power and power consumption of the load device and stably maintain the voltage of the DC bus without significantly increasing the circuit scale.

[0009] According to the power supply device according to one aspect of the present disclosure, the discharge control circuit monitors the voltage of the DC bus at a second node closer to the load device than a first node at which the overvoltage protection circuit monitors the voltage of the DC bus, The power supply device further includes a diode that blocks the current flowing from the second node to the first node.

[0010] Thereby, even when the overvoltage threshold is lower than the regeneration threshold, the regenerative power can be consumed using the discharge circuit without stopping the power supply from the power supply device to the load device, and the load device itself can consume the regenerative power.

[0011] According to the power supply device according to one aspect of the present disclosure, the power supply device a transformer, a power conversion circuit provided on the primary side of the transformer, which converts an input voltage into an output voltage and supplies the output voltage to the transformer, a voltage control circuit provided on the primary side of the transformer, which controls the output voltage of the power conversion circuit, and a voltage feedback circuit provided on the secondary side of the transformer, which monitors the voltage of the DC bus. The overvoltage protection circuit, the voltage control circuit, and the discharge control circuit acquire the voltage of the DC bus from the voltage feedback circuit.

[0012] Thereby, the overvoltage protection circuit, the voltage control circuit, and the discharge control circuit can monitor the voltage of the DC bus.

[0013] According to the power supply device according to one aspect of the present disclosure, the voltage feedback circuit includes a variable resistor that sets a target voltage of the DC bus, and the discharge control circuit acquires the voltage applied to the variable resistor as the voltage of the DC bus.

[0014] Thereby, the discharge threshold can be changed according to the increase or decrease of the target voltage of the DC bus.

[0015] According to the power supply device according to one aspect of the present disclosure, The power supply device further includes an abnormality determination circuit that determines an abnormality in the power conversion circuit or the voltage control circuit. When an abnormality occurs in the power conversion circuit or the voltage control circuit, the abnormality determination circuit controls the discharge circuit to stop the consumption of power on the DC bus.

[0016] Thereby, even if an abnormality occurs in the power conversion circuit or the voltage control circuit, excessive heat generation of the discharge circuit can be prevented.

[0017] According to the power supply device according to one aspect of the present disclosure, The discharge threshold has hysteresis.

[0018] Thereby, the number of transitions of the discharge circuit between on and off can be reduced, and the power supply device can operate stably.

[0019] According to the power supply device according to one aspect of the present disclosure, The load device includes a motor.

[0020] Thereby, the power supply device can supply power to a load device that generates regenerative power.

Advantages of the Invention

[0021] According to the power supply device according to one aspect of the present disclosure, without significantly increasing the circuit scale, fluctuations in the voltage of the DC bus caused by the regenerative power and power consumption of the load device can be reduced, and the voltage of the DC bus can be stably maintained.

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Modes for Carrying Out the Invention

[0023] Hereinafter, embodiments according to one aspect of the present disclosure will be described with reference to the drawings. In each drawing, the same reference numerals denote the same components.

[0024] [Application Example] FIG. 1 is a block diagram showing an example of the configuration of the power system according to the first embodiment. The power system in FIG. 1 includes an AC power supply 1, a power supply device 2, a motor controller 3, and a motor 4.

[0025] The AC power supply 1 may be, for example, a commercial single-phase or three-phase AC power supply.

[0026] The power supply device 2 receives power supply from the AC power supply 1 and supplies DC power to the motor controller 3 and the motor 4 which are load devices. The power supply device 2 includes at least DC buses 20a, 20b, an overvoltage protection circuit 23a, a switch Q1, a resistor R1, and a discharge control circuit 26. The DC buses 20a, 20b are connected to the motor controller 3 and the motor 4. When the voltage of the DC buses 20a, 20b exceeds a predetermined overvoltage threshold value, the overvoltage protection circuit 23a stops the power supply from the power supply device 2 to the motor controller 3 and the motor 4. The voltage of the DC buses 20a, 20b indicates the potential difference across the positive DC bus 20a and the negative DC bus 20b. The switch Q1 and the resistor R1 are a discharge circuit connected to the DC buses 20a, 20b. The switch Q1 is, for example, a field effect transistor. When the voltage of the DC buses 20a, 20b exceeds a discharge threshold value which is higher than the target voltage of the DC buses 20a, 20b and lower than the overvoltage threshold value, the discharge control circuit 26 turns on the switch Q1, and thereby consumes the power of the DC buses 20a, 20b by the resistor R1 to lower the voltage of the DC buses 20a, 20b.

[0027] The motor controller 3 receives power supply from the power supply device 2 and controls the operation of the motor 4. The motor 4 may generate regenerative power, and the generated regenerative power flows to the DC buses 20a, 20b of the power supply device 2 via the motor controller 3. The motor controller 3 includes a regenerative control circuit 3a that consumes the regenerative power to lower the voltage of the internal bus when the voltage of its internal bus (not shown) exceeds a predetermined regenerative threshold value due to the regenerative power.

[0028] Figure 2 is a graph showing an example of the voltage of the DC buses 20a, 20b of the power system in Figure 1. V0 indicates the target voltage of the DC buses 20a, 20b, and the power supply device 2 operates to match or approach the voltage of the DC buses 20a, 20b to the target voltage V0. Vth1 indicates the overvoltage threshold value of the overvoltage protection circuit 23a. Vth2 indicates the regenerative threshold value of the regenerative control circuit 3a. Vth3 indicates the discharge threshold value of the discharge control circuit 26.

[0029] When the voltages of the DC buses 20a and 20b exceed the overvoltage threshold value Vth1 (time t3), as described above, the overvoltage protection circuit 23a stops the power supply from the power device 2 to the motor controller 3 and the motor 4, and thereby the voltages of the DC buses 20a and 20b become zero. Also, when the voltage of the internal bus of the motor controller 3 exceeds the regeneration threshold value Vth2 due to the regenerative power of the motor 4, the voltages of the DC buses 20a and 20b also exceed the regeneration threshold value Vth2 (time t2). At this time, as described above, the regeneration control circuit 3a consumes the regenerative power to lower the voltage of the internal bus, and thereby the voltages of the DC buses 20a and 20b are lowered to the target voltage V0. However, the regeneration threshold value Vth2 has a certain magnitude, and the regeneration control circuit 3a does not operate until the voltage of the internal bus of the motor controller 3 exceeds the regeneration threshold value Vth2, and the voltages of the internal bus and the DC buses 20a and 20b cannot be lowered. On the other hand, according to the power device 2 of FIG. 1, by setting a discharge threshold value Vth3 smaller than the regeneration threshold value Vth2, the switch Q1 can be immediately turned on in response to the increase in the voltages of the DC buses 20a and 20b, and the voltages of the DC buses 20a and 20b can be immediately lowered.

[0030] According to the power supply device 2 according to the embodiment, it is possible to reduce fluctuations in the voltages of the DC buses 20a and 20b without mounting a large number of capacitors. Further, according to the power supply device 2 according to the embodiment, when the voltages of the DC buses 20a and 20b rise due to the regenerative power of the motor 4, the switch Q1 is turned on and the power of the DC buses 20a and 20b is consumed by the resistor R1, thereby reducing fluctuations in the voltages of the DC buses 20a and 20b due to the regenerative power of the motor 4. Further, according to the power supply device 2 according to the embodiment, when the voltages of the DC buses 20a and 20b rise due to the regenerative power of the motor 4, the power supply from the power supply device 2 to the motor controller 3 and the motor 4 continues without stopping. Therefore, even if the power consumption of the motor 4 suddenly increases thereafter, the power supply device 2 can quickly increase its output power and supply the power required for the motor 4. Thus, according to the power supply device 2 according to the embodiment, without significantly increasing the circuit scale, fluctuations in the voltages of the DC buses 20a and 20b due to the regenerative power and power consumption of the motor 4 can be reduced, and the voltages of the DC buses 20a and 20b can be stably maintained.

[0031] [First Embodiment] Hereinafter, the power supply device according to the first embodiment will be further described.

[0032] [Configuration Example of First Embodiment] Referring to FIG. 1, in addition to the DC buses 20a and 20b, the overvoltage protection circuit 23a, the switch Q1, the resistor R1, and the discharge control circuit 26, the power supply device 2 includes a rectifier circuit 21, an inverter 22, a voltage control circuit 23, a transformer T1, a rectifier circuit 24, and a voltage feedback circuit 25.

[0033] The rectifier circuit 21 rectifies the AC power supplied from the AC power source 1 into DC power. The inverter 22 is provided on the primary side of the transformer T1 and is a power conversion circuit that converts the DC power input from the rectifier circuit 21 into AC power of a predetermined voltage and supplies it to the transformer T1. The voltage control circuit 23 is provided on the primary side of the transformer T1 and controls the output voltage of the inverter 22 (i.e., the voltage applied to the primary winding of the transformer T1). In the example of FIG. 1, the overvoltage protection circuit 23a is integrated with the voltage control circuit 23. The rectifier circuit 24 rectifies the AC power generated in the secondary winding of the transformer T1 and outputs it to the DC buses 20a and 20b. The voltage feedback circuit 25 is provided on the secondary side of the transformer T1 and monitors the voltages of the DC buses 20a and 20b. The voltage control circuit 23 and the overvoltage protection circuit 23a obtain the voltages of the DC buses 20a and 20b from the voltage feedback circuit 25. The voltage control circuit 23 controls the output voltage of the inverter 22 so that the voltages of the DC buses 20a and 20b match or approach the target voltage V0 based on the voltages of the DC buses 20a and 20b.

[0034] In the example of FIG. 1, the power supply device 2 is configured as an isolated power conversion circuit including the transformer T1.

[0035] FIG. 3 is a circuit diagram showing an example of the configuration of the power supply device 2 in FIG. 1. For simplicity of illustration, FIG. 3 shows only the secondary side circuit of the transformer T1. The power supply device 2 includes the rectifier circuit 24, the voltage feedback circuit 25, the discharge control circuit 26, the switch Q1, and the resistor R1 described with reference to FIG. 1, and further includes the electrolytic capacitor C2 and the resistors R5 and R6.

[0036] The rectifier circuit 24 includes the diode D1 and the electrolytic capacitor C1. The diode D1 is connected to the secondary winding of the transformer T1. The electrolytic capacitor C1 is connected across the DC buses 20a and 20b and smoothes the voltage rectified by the diode D1.

[0037] The voltage feedback circuit 25 includes resistors R2 to R4, a variable resistor RV, a shunt regulator SR1, and a light-emitting diode LED. The resistor R2, the shunt regulator SR1, and the light-emitting diode LED are connected in series across the DC buses 20a and 20b. The resistors R3 and R4 are also connected in series across the DC buses 20a and 20b, and the variable resistor RV is connected in parallel with the resistor R4. The target voltage of the DC buses 20a and 20b is set according to the resistance value of the variable resistor RV. The voltage of the DC buses 20a and 20b is divided by the resistors R3, R4, and the variable resistor RV, and the divided voltage is applied to the reference terminal of the shunt regulator SR1. The light-emitting diode LED forms a photocoupler together with a phototransistor (not shown) provided in the primary-side circuit of the transformer T1, and notifies the voltage control circuit 23 and the overvoltage protection circuit 23a of the voltage of the DC buses 20a and 20b at the node N1.

[0038] The resistors R5 and R6 are connected in series across the DC buses 20a and 20b, divide the voltage of the DC buses 20a and 20b at the node N2, and send it to the discharge control circuit 26.

[0039] The electrolytic capacitor C2 is connected across the DC buses 20a and 20b to smooth the voltage of the DC buses 20a and 20b.

[0040] The discharge control circuit 26 includes resistors R7 to R9, switch Q2, comparator CMP1, and diode D2. Resistors R7 to R9 and switch Q2 are a voltage source of a reference voltage corresponding to the discharge threshold Vth3. The comparator CMP1 compares the voltages of the DC buses 20a and 20b divided by the resistors R5 and R6 with the discharge threshold Vth3, and turns on the switch Q1 when the voltages of the DC buses 20a and 20b exceed the discharge threshold Vth3. In the example of FIG. 3, the discharge threshold Vth3 has hysteresis. When the switch Q1 is turned on, at the same time, the switch Q2 is also turned on, so the discharge threshold Vth3 changes. For example, when the target voltage V0 of the DC buses 20a and 20b is 48V, the discharge threshold Vth3 for turning on the switch Q1 is set to 55V, and the discharge threshold Vth3 for turning off the switch Q1 is set to 50V.

[0041] In the example of FIG. 3, when the switch Q1 is turned on, a constant current flows through the switch Q1 and the resistor R1.

[0042] When the regeneration threshold Vth2 is higher than the overvoltage threshold Vth1, if the voltages of the DC buses 20a and 20b increase due to the regenerative power, before the regenerative control circuit 3a operates, the overvoltage protection circuit 23a stops the power supply from the power supply device 2 to the motor controller 3 and the motor 4. In order to operate the regenerative control circuit 3a without stopping the power supply from the power supply device 2 to the motor controller 3 and the motor 4, the power supply device 2 and the motor controller 3 need to be always configured to satisfy Vth1 > Vth2.

[0043] [Modification of the First Embodiment] FIG. 4 is a circuit diagram showing an example of the configuration of a power supply device 2A according to a first modification of the first embodiment. The power supply device 2A has a configuration obtained by removing resistors R5 and R6 from the power supply device 2 of FIG. 3. Further, according to FIG. 4, the discharge control circuit 26 acquires the voltages of the DC buses 20a and 20b from the voltage feedback circuit 25. Specifically, the discharge control circuit 26 acquires the voltages of the DC buses 20a and 20b at the node N2 divided by the resistors R3, R4, and the variable resistor RV, that is, the voltage applied to the variable resistor RV, as the voltages of the DC buses 20a and 20b. The comparator CMP1 compares the voltage applied to the variable resistor RV with the discharge threshold Vth3. As described above, the target voltage V0 of the DC buses 20a and 20b is set according to the resistance value of the variable resistor RV. According to the power supply device 2A of FIG. 4, even if the voltages of the DC buses 20a and 20b change by changing the resistance value of the variable resistor RV, the voltage input from the voltage feedback circuit 25 to the comparator CMP1 is the same as before changing the resistance value of the variable resistor RV. Therefore, the discharge threshold Vth3 equivalently changes according to the increase or decrease of the target voltage V0 of the DC buses 20a and 20b. According to the power supply device 2A of FIG. 4, the discharge control circuit 26 can be operated to turn on the switch Q1 when the voltages of the DC buses 20a and 20b become a predetermined multiple, for example, 1.3 times the target voltage V0, regardless of the magnitude of the target voltage V0 of the DC buses 20a and 20b. For example, when the target voltage V0 is 50V, the discharge control circuit 26 turns on the switch Q1 when the voltages of the DC buses 20a and 20b reach 65V. Also, when the target voltage V0 is 55V, the discharge control circuit 26 turns on the switch Q1 when the voltages of the DC buses 20a and 20b reach 71.5V.

[0044] FIG. 5 is a circuit diagram showing an example of the configuration of a power supply device 2B according to a second modification of the first embodiment. In addition to each component of the power supply device 2A in FIG. 4, the power supply device 2B includes a diode D3. As described above, the overvoltage protection circuit 23a obtains the voltages of the DC buses 20a and 20b at the node N1 from the voltage feedback circuit 25. Further, the discharge control circuit 26 obtains the voltages of the DC buses 20a and 20b at the node N2 divided by the resistors R3, R4, and the variable resistor RV from the voltage feedback circuit 25. The node N2 is provided closer to the motor controller 3 than the node N1. The diode D3 is inserted into the DC bus 20a so as to block the current flowing from the node N2 to the node N1. In the configurations of the power supply device 2 in FIG. 3 and the power supply device 2A in FIG. 4, as described above, in order to operate the regeneration control circuit 3a without stopping the power supply from the power supply device 2 to the motor controller 3 and the motor 4, the power supply device 2 and the motor controller 3 need to be always configured to satisfy Vth1 > Vth2. On the other hand, according to the power supply device 2B in FIG. 4, by inserting the diode D3 between the nodes N1 and N2, even if the voltage of the node N2 increases due to the regenerative power, the voltage of the node N1 does not increase. Therefore, it is possible to prevent the overvoltage protection circuit 23a from erroneously stopping the power supply from the power supply device 2B to the motor controller 3 and the motor 4. Therefore, according to the power supply device 2B in FIG. 4, even if Vth1 < Vth2, the regenerative power can be consumed using the discharge control circuit 26, the switch Q1, and the resistor R1 without stopping the power supply from the power supply device 2 to the motor controller 3 and the motor 4, and the regeneration control circuit 3a can be operated.

[0045] Note that in the example of FIG. 5, the voltage control circuit 23 obtains the voltages of the DC buses 20a and 20b at the node N2 from the voltage feedback circuit 25. As described above, the voltage of the DC buses 20a and 20b at the node N2 divided by the resistors R3, R4, and the variable resistor RV is applied to the reference terminal of the shunt regulator SR1, and this voltage is notified to the voltage control circuit 23 via a photocoupler including a light emitting diode LED.

[0046] [Effect of the First Embodiment] According to the power supply devices 2, 2A, and 2B according to the first embodiment, without significantly increasing the circuit scale, fluctuations in the voltages of the DC buses 20a and 20b caused by the regenerative power and power consumption of the motor 4 can be reduced, and the voltages of the DC buses 20a and 20b can be stably maintained.

[0047] [Second Embodiment] Hereinafter, the power supply device according to the second embodiment will be described.

[0048] [Configuration Example of the Second Embodiment] FIG. 6 is a block diagram showing an example of the configuration of a power system according to the second embodiment. The power system of FIG. 6 includes a power supply device 2C instead of the power supply device 2 of the power system of FIG. 1. The power supply device 2C includes an abnormality determination circuit 27 and a switch Q3 in addition to each component of the power supply device 2 of FIG. 1.

[0049] The abnormality determination circuit 27 determines an abnormality in the primary side circuit of the transformer T1, that is, an abnormality in the inverter 22 or the voltage control circuit 23. An abnormality in the inverter 22 or the voltage control circuit 23 includes, for example, the occurrence of an excessive output voltage from the inverter 22 due to a failure of the inverter 22 or the voltage control circuit 23, or due to a failure of voltage feedback. The gate of the switch Q1 is grounded via the switch Q3. When an abnormality occurs in the inverter 22 or the voltage control circuit 23, the abnormality determination circuit 27 controls the switch Q1 to stop the power consumption of the DC buses 20a and 20b by turning on the switch Q3.

[0050] FIG. 7 is a circuit diagram showing an example of the configuration of the power supply device 2C in FIG. 6. For simplicity of illustration, FIG. 7 shows only the secondary side circuit of the transformer T1. The abnormality determination circuit 27 includes a reference voltage source E1 and a comparator CMP2. The comparator CMP2 compares the voltage at any node in the secondary side circuit of the transformer T1 with the voltage of the reference voltage source E1, and determines that an abnormality has occurred in the inverter 22 or the voltage control circuit 23 when the voltage of the voltage feedback circuit 25 exceeds the voltage of the reference voltage source E1. In the example of FIG. 7, the comparator CMP2 monitors the voltage of the node N1. When an abnormality occurs in the inverter 22 or the voltage control circuit 23 and an excessive voltage is generated in the primary side circuit of the transformer T1, the voltage of the node N1 in the secondary side circuit of the transformer T1 increases. As described above, since the diode D3 is inserted into the DC bus 20a so as to block the current flowing from the node N2 to the node N1, the voltage of the node N1 does not increase due to the regenerative power of the motor 4. Other components of the power supply device 2C are configured in the same manner as the corresponding components of the power supply device 2B in FIG. 5. When the voltages of the DC buses 20a and 20b rise abnormally, if the discharge control circuit 26 turns on the switch Q1, the switch Q1 and the resistor R1 may overheat and be damaged. On the other hand, when the power supply device 2C in FIG. 7 determines that an abnormality has occurred in the inverter 22 or the voltage control circuit 23, it forcibly turns off the switch Q1 by turning on the switch Q3. Thereby, even if an abnormality occurs in the inverter 22 or the voltage control circuit 23, excessive heat generation of the switch Q1 and the resistor R1 can be prevented.

[0051] [Modification of the Second Embodiment] FIG. 8 is a circuit diagram showing an example of the configuration of a power supply device 2D according to a modification of the second embodiment. The power supply device 2D includes a voltage feedback circuit 25D and a discharge control circuit 26D instead of the voltage feedback circuit 25 and the discharge control circuit 26 in FIG. 7, and further includes resistors R15 and R16.

[0052] The voltage feedback circuit 25D has a configuration in which the variable resistor RV is removed from the voltage feedback circuit 25 in FIG. 7.

[0053] The discharge control circuit 26D includes resistors R11 to R14, a shunt regulator SR2, a switch Q11, and a diode D11. The switch Q11 is, for example, a bipolar transistor. The emitter of the switch Q11 is connected to the DC bus 20a, and the collector is grounded via resistors R15 and R16 connected in series with each other. The connection point between the resistors R15 and R16 is connected to the gate of the switch Q1. The base of the switch Q11 is connected to the cathode of the shunt regulator SR2 via the resistor R13. The resistors R11 and R12 divide the voltages of the DC buses 20a and 20b at the node N2, apply the divided voltage to the control terminal of the shunt regulator SR2, and also apply the divided voltage to the cathode of the diode D11 via the resistor R14. The anode of the diode D11 is connected to the collector of the switch Q11. When the voltages of the DC buses 20a and 20b rise, the cathode of the shunt regulator SR2 becomes a low level, and the switch Q11 is turned on. As a result, the gate voltage of the switch Q1 becomes a high level, and the switch Q1 is turned on. Due to the diode D11 and the resistor R14, the discharge threshold Vth3 for turning on the switch Q1 has hysteresis.

[0054] The diode D3 is inserted into the DC bus 20a so as to block the current flowing from the node N2 to the node N1.

[0055] According to the power supply device 2D of FIG. 8, by including the abnormality determination circuit 27, similar to the power supply device 2C of FIG. 7, even if an abnormality occurs in the inverter 22 or the voltage control circuit 23, excessive heat generation of the switch Q1 and the resistor R1 can be prevented.

[0056] [Effects of the Second Embodiment] According to the power supply devices 2C and 2D according to the second embodiment, similar to the power supply devices 2, 2A, and 2B according to the first embodiment, without significantly increasing the circuit scale, it is possible to reduce fluctuations in the voltages of the DC buses 20a and 20b caused by the regenerative power and power consumption of the motor 4, and stably maintain the voltages of the DC buses 20a and 20b. Further, according to the power supply devices 2C and 2D according to the second embodiment, even if an abnormality occurs in the inverter 22 or the voltage control circuit 23, excessive heat generation of the switch Q1 and the resistor R1 can be prevented.

[0057] [Other Modification Examples] As described above, the embodiments of the present disclosure have been described in detail. However, the above description is merely an exemplification of the present disclosure in all respects. Needless to say, various improvements and modifications can be made without departing from the scope of the present disclosure. For example, the following changes are possible. In the following, the same reference numerals are used for the same components as in the above embodiment, and the description of the same points as in the above embodiment is omitted as appropriate. The following modification examples can be combined as appropriate.

[0058] In the example of FIG. 3 and the like, the case where the rectifier circuit 24 is configured as a half-wave rectifier circuit including one diode D1 has been described. However, the rectifier circuit may be configured as a full-wave rectifier circuit.

[0059] Further, the power supply device may be configured to receive power supply from a DC power source instead of an AC power source.

[0060] Further, the power supply device may be configured as a non-insulated power conversion circuit that does not include a transformer.

[0061] In the examples of FIGS. 1 and 6, the regenerative control circuit 3a is shown as being integrated with the motor controller 3. However, the regenerative control circuit 3a may be provided separately from the motor controller 3.

[0062] Further, the power supply device may be configured to supply power not only to the motor controller 3 and the motor 4 but also to any load device that generates regenerative power.

[0063] [Summary] The power supply devices according to each aspect of the present disclosure may be expressed as follows.

[0064] According to the power supply devices 2, 2A to 2D according to one aspect of the present disclosure, power supply devices 2, 2A to 2D that supply DC power to a load device are provided. The power supply device 2 includes DC buses 20a, 20b, an overvoltage protection circuit 23a, a discharge circuit, and a discharge control circuit 26. The DC buses 20a, 20b are connected to the load device. The overvoltage protection circuit 23a stops the power supply from the power supply device 2 to the load device when the voltage of the DC buses 20a, 20b exceeds a predetermined overvoltage threshold. The discharge circuit is connected to the DC buses 20a, 20b. The discharge control circuit 26 controls the discharge circuit to consume the power of the DC buses 20a, 20b and lower the voltage of the DC buses 20a, 20b when the voltage of the DC buses 20a, 20b exceeds a discharge threshold that is higher than the target voltage of the DC buses 20a, 20b and lower than the overvoltage threshold.

[0065] According to the power supply devices 2B to 2D according to one aspect of the present disclosure, the discharge control circuit 26 monitors the voltage of the DC buses 20a, 20b at a second node N2 that is closer to the load device than a first node N1 at which the overvoltage protection circuit 23a monitors the voltage of the DC buses 20a, 20b. The power supply device 2 further includes a diode D3 that blocks the current flowing from the second node N2 to the first node N1.

[0066] According to the power supply devices 2A to 2C according to one aspect of the present disclosure, the power supply devices 2A to 2C further include a transformer T1, an inverter 22, a voltage control circuit 23, and a voltage feedback circuit 25. The inverter 22 is provided on the primary side of the transformer T1, converts an input voltage into an output voltage, and supplies it to the transformer T1. The voltage control circuit 23 is provided on the primary side of the transformer T1 and controls the output voltage of the inverter 22. The voltage feedback circuit 25 is provided on the secondary side of the transformer T1 and monitors the voltages of the DC buses 20a and 20b. The overvoltage protection circuit 23a, the voltage control circuit 23, and the discharge control circuit 26 acquire the voltages of the DC buses 20a and 20b from the voltage feedback circuit 25.

[0067] According to the power supply devices 2B and 2C according to one aspect of the present disclosure, the voltage feedback circuit 25 includes a variable resistor RV that sets the target voltages of the DC buses 20a and 20b. The discharge control circuit 26 acquires the voltage applied to the variable resistor RV as the voltages of the DC buses 20a and 20b.

[0068] According to the power supply devices 2C and 2D according to one aspect of the present disclosure, the power supply devices 2C and 2D further include an abnormality determination circuit 27 that determines an abnormality in the inverter 22 or the voltage control circuit 23. When an abnormality occurs in the inverter 22 or the voltage control circuit 23, the abnormality determination circuit 27 controls a discharge circuit so as to stop the consumption of power of the DC buses 20a and 20b.

[0069] According to the power supply devices 2, 2A to 2D according to one aspect of the present disclosure, the discharge threshold has hysteresis.

[0070] According to the power supply devices 2, 2A to 2D according to one aspect of the present disclosure, the load device includes a motor 4.

Industrial Applicability

[0071] The power supply device according to each aspect of the present disclosure can be used to supply power to a load device that generates regenerative power.

Description of Reference Numerals

[0072] 1 AC power supply 2, 2A to 2D power supply device 3 Motor controller 3a Regenerative control circuit 4 Motor 20a, 20b DC bus 21 Rectifier circuit 22 Inverter 23 Voltage control circuit 23a Overvoltage protection circuit 24 Rectifier circuit 25, 25D Voltage feedback circuit 26 Discharge control circuit 27 Abnormality determination circuit C1, C2 Electrolytic capacitor CMP1, CMP2 Comparator D1 to D3, D11 Diode E1 Reference voltage source LED Light-emitting diode Q1 to Q3 Switch R1 to R9, R11 to R16 Resistor SR1, SR2 Shunt regulator T1 Transformer RV Variable resistor

Claims

1. A power supply device for supplying DC power to a load device, comprising: a DC bus connected to the load device; an overvoltage protection circuit that stops power supply from the power supply device to the load device when the voltage of the DC bus exceeds a predetermined overvoltage threshold; a discharge circuit connected to the DC bus; a discharge control circuit for controlling the discharge circuit; the load device includes a regeneration control circuit that consumes the regeneration power and reduces the voltage of the DC bus when the voltage of the DC bus exceeds a predetermined regeneration threshold due to the regeneration power; the discharge control circuit controls the discharge circuit to consume the power of the DC bus and reduce the voltage of the DC bus when the voltage of the DC bus exceeds a discharge threshold that is higher than the target voltage of the DC bus and lower than the overvoltage threshold and the regeneration threshold; A power supply device.

2. The discharge control circuit monitors the voltage of the DC bus at a second node closer to the load device than a first node at which the overvoltage protection circuit monitors the voltage of the DC bus, the power supply device further includes a diode that blocks the current flowing from the second node to the first node. The power supply device according to Claim 1.

3. The power supply device includes: a transformer; a power conversion circuit provided on the primary side of the transformer, which converts an input voltage into an output voltage and supplies it to the transformer; a voltage control circuit provided on the primary side of the transformer, which controls the output voltage of the power conversion circuit; a voltage feedback circuit provided on the secondary side of the transformer, which monitors the voltage of the DC bus; the overvoltage protection circuit, the voltage control circuit, and the discharge control circuit obtain the voltage of the DC bus from the voltage feedback circuit. The power supply device according to Claim 1 or 2.

4. The voltage feedback circuit includes a variable resistor for setting the target voltage of the DC bus, the discharge control circuit obtains the voltage applied to the variable resistor as the voltage of the DC bus. The power supply device according to Claim 3.

5. The power supply device further includes an abnormality determination circuit for determining an abnormality in the power conversion circuit or the voltage control circuit, when an abnormality occurs in the power conversion circuit or the voltage control circuit, the abnormality determination circuit controls the discharge circuit to stop consuming the power of the DC bus. The power supply device according to Claim 3 or 4.

6. The discharge threshold has hysteresis. The power supply device according to one of claims 1 to 5. **Claim 7** The load device includes a motor. The power supply device according to one of claims 1 to 6.

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