JP2015128356A - Overvoltage protection circuit and power conversion device having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact and low-cost overvoltage protection circuit and a power conversion device having the same, protecting equipment from an instantaneous overvoltage.SOLUTION: In an overvoltage protection circuit 50, a second switch 12 is normally turned on to close a bypass circuit 35, to thereby prevent power consumption in a second impedance circuit 22 and to enable avoiding the decrease of a voltage to be applied to equipment 30 as large as a voltage fall in the second impedance circuit 22. Also, at overvoltage, a switch 11 in an overvoltage conduction circuit 10 is turned on and the second switch 12 is turned off, so that only a voltage corresponding to the impedance ratio of the first impedance circuit 21 to the second impedance circuit 22 is applied to the equipment 30. Thus, the equipment 30 is protected from overvoltage.

Description

  The present invention relates to an overvoltage protection circuit and a power conversion device including the same.

  A device used in an area where the power supply voltage is likely to fluctuate may cause a failure of the device depending on the countermeasure against the voltage rise. Therefore, an overvoltage protection circuit as disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2009-207329) is provided. This overvoltage protection circuit is configured to shut off the power supply with a relay when the voltage is equal to or higher than a predetermined voltage.

  However, the time required for the power supply voltage to become excessive is extremely short, and the response is slow and it is difficult to reliably protect it by the interruption by the relay. In particular, a semiconductor element such as a semiconductor element that has a short time to withstand overvoltage cannot be protected by being interrupted by a relay. Further, increasing the breakdown voltage of a semiconductor element or the like only for an instantaneous excessive voltage leads to an increase in cost and size.

  Accordingly, an object of the present invention is to provide a small and low-cost overvoltage protection circuit that protects a device from a momentary excessive voltage, and a power conversion device including the same.

  An overvoltage protection device according to a first aspect of the present invention is an overvoltage protection circuit connected between a power supply and a device to which power is supplied from the power supply, and includes an overvoltage conduction circuit, a first impedance circuit, 2 impedance circuit. The overvoltage conduction circuit is connected in parallel with the device between a pair of power supply lines connecting the power source and the device, and allows current to flow when overvoltage occurs. The first impedance circuit is connected between the pair of power supply lines in parallel with the device and in series with the overvoltage conduction circuit. The second impedance circuit is connected between the power supply in the power supply line and the first impedance circuit.

  In this overvoltage protection circuit, a closed circuit of [power supply-overvoltage conduction circuit-first impedance circuit-second impedance circuit-power supply] is configured by conducting the overvoltage conduction circuit at the time of overvoltage. As a result, since only a voltage corresponding to the ratio of the impedances of the two impedance circuits is applied to the device, the device can be protected from overvoltage.

  An overvoltage protection circuit according to a second aspect of the present invention is the overvoltage protection circuit according to the first aspect, wherein the overvoltage conduction circuit is a device that causes a current to flow when overvoltage occurs. Any one of the diodes is included.

  A transient voltage suppressor, a Zener diode, a surge absorber, and an avalanche diode are all elements that operate with a short response time with respect to voltage transient fluctuations. Therefore, in this overvoltage protection circuit, when the element conducts at the time of overvoltage, only a voltage corresponding to the ratio of the impedances of the two impedance circuits is applied to the device, and thus the device can be protected from the overvoltage.

  An overvoltage protection circuit according to a third aspect of the present invention is the overvoltage protection circuit according to the first aspect, and further includes a voltage detector that detects the voltage of the power supply. The overvoltage conduction circuit has a switch that opens and closes between the power supply line and the first impedance circuit. This switch is turned on when the detection value by the voltage detector exceeds a predetermined threshold value, and conducts between the power supply line and the first impedance circuit.

  In this overvoltage protection circuit, for example, when the impedance of each of the first impedance circuit and the second impedance circuit is Za and Zb, the switch causes the power supply line and the first impedance circuit to conduct at the time of overvoltage. Since only a voltage according to the ratio {Za / (Za + Zb)} of the two impedances of the power supply voltage is applied, the device can be protected from overvoltage.

  An overvoltage protection circuit according to a fourth aspect of the present invention is the overvoltage protection circuit according to the first aspect or the second aspect, and further includes a voltage detector and a bypass circuit. The voltage detector detects the voltage of the power supply. The bypass circuit is a circuit that bypasses the second impedance circuit. The bypass circuit has a second switch that opens and closes the bypass circuit. The second switch normally closes the bypass circuit, and shuts off the bypass circuit when the value detected by the voltage detector exceeds a predetermined threshold value.

  In this overvoltage protection circuit, for example, when the impedances of the first impedance circuit and the second impedance circuit are Za and Zb, the bypass circuit is normally closed, so that power is not consumed by the impedance Zb. It is also possible to avoid the voltage applied to the device being lowered by the voltage drop at the impedance Zb.

  On the other hand, since the second switch cuts off the bypass circuit at the time of overvoltage, only the voltage according to the ratio of two impedances of power supply voltage {Za / (Za + Zb)} is applied to the device, so that the device is protected from overvoltage. Can do.

  An overvoltage protection circuit according to a fifth aspect of the present invention is the overvoltage protection circuit according to the third aspect, and further includes a bypass circuit. The bypass circuit is a circuit that bypasses the second impedance circuit. The bypass circuit has a second switch that opens and closes the bypass circuit. The second switch normally closes the bypass circuit, and shuts off the bypass circuit when the detection value by the voltage detector exceeds a predetermined threshold value.

  In this overvoltage protection circuit, for example, when the impedances of the first impedance circuit and the second impedance circuit are Za and Zb, the bypass circuit is normally closed, so that power is not consumed by the impedance Zb. It is also possible to avoid the voltage applied to the device being lowered by the voltage drop at the impedance Zb.

  On the other hand, since the second switch cuts off the bypass circuit at the time of overvoltage, only the voltage according to the ratio of two impedances of power supply voltage {Za / (Za + Zb)} is applied to the device, so that the device is protected from overvoltage. Can do.

  An overvoltage protection circuit according to a sixth aspect of the present invention is the overvoltage protection circuit according to the first aspect or the second aspect, and further includes a voltage detector and a third switch. The voltage detection value detects the voltage of the power supply. The third switch opens and closes the power line. The third switch normally turns on the power line, and shuts off the power line after the operation of the second switch when the value detected by the voltage detector exceeds a predetermined threshold.

  In this overvoltage protection circuit, for example, when the impedances of the first impedance circuit and the second impedance circuit are Za and Zb, the switch and the second switch operate at the time of overvoltage, so that the device has two impedances of the power supply voltage. Since only a voltage corresponding to the ratio {Za / (Za + Zb)} is applied, the device can be protected from overvoltage, and further, the power at the impedances Za and Zb can be obtained by operating the third switch to cut off the power line. Stop consumption. As a result, overheating of the impedances Za and Zb can be suppressed and the power rating can be reduced.

  An overvoltage protection circuit according to a seventh aspect of the present invention is the overvoltage protection circuit according to any one of the third aspect to the fifth aspect, and further includes a third switch. The third switch opens and closes the power line. The third switch normally turns on the power line, and shuts off the power line after the operation of the second switch when the value detected by the voltage detector exceeds a predetermined threshold.

  In this overvoltage protection circuit, for example, when the impedances of the first impedance circuit and the second impedance circuit are Za and Zb, the switch and the second switch operate at the time of overvoltage, so that the device has two impedances of the power supply voltage. Since only a voltage corresponding to the ratio {Za / (Za + Zb)} is applied, the device can be protected from overvoltage, and further, the power at the impedances Za and Zb can be obtained by operating the third switch to cut off the power line. Stop consumption. As a result, overheating of the impedances Za and Zb can be suppressed and the power rating can be reduced.

  An overvoltage protection circuit according to an eighth aspect of the present invention is the overvoltage protection circuit according to any one of the first to seventh aspects, wherein the power supply is an AC power supply.

  In this overvoltage protection circuit, even if the supply voltage from the AC power supply is an excessive voltage, only a voltage corresponding to the ratio of the two impedances is applied to the device. Therefore, it is not necessary to design the equipment with a high voltage rating only for protection from an excessive voltage for a short time, which is reasonable.

  An overvoltage protection circuit according to a ninth aspect of the present invention is the overvoltage protection circuit according to any one of the first to seventh aspects, wherein the power supply is a DC power supply.

  In this overvoltage protection circuit, the switch for turning on and off the alternating current needs bidirectionality, but the switch arranged on the downstream side of the DC power supply may be a one-way switch, so that the cost of the switch can be reduced.

  A power conversion device according to a tenth aspect of the present invention includes a converter circuit, an inverter circuit, and an overvoltage protection circuit according to any one of the first to ninth aspects. The converter circuit is connected to an AC power source and converts an AC voltage into a DC voltage. The inverter circuit converts a DC voltage into an AC voltage.

  In this power converter, the overvoltage protection circuit can protect the converter circuit from excessively applied excessive AC voltage or the inverter circuit from transiently applied excessive DC voltage.

  In the overvoltage protection device according to the first aspect of the present invention, a closed circuit of [power supply-overvoltage conduction circuit-first impedance circuit-second impedance circuit-power supply] is configured by conducting the overvoltage conduction circuit at the time of overvoltage. The As a result, since only a voltage corresponding to the ratio of the impedances of the two impedance circuits is applied to the device, the device can be protected from overvoltage.

  The overvoltage protection circuit according to the second aspect of the present invention protects the device from overvoltage because the device conducts at the time of overvoltage so that only a voltage corresponding to the impedance ratio of the two impedance circuits is applied to the device. Can do.

  In the overvoltage protection circuit according to the third aspect of the present invention, for example, when the impedances of the first impedance circuit and the second impedance circuit are Za and Zb, the switch is connected between the power supply line and the first impedance circuit when overvoltage occurs. By conducting the current, only a voltage corresponding to the ratio of two impedances of the power supply voltage {Za / (Za + Zb)} is applied to the device, so that the device can be protected from overvoltage.

  In the overvoltage protection circuit according to the fourth aspect or the fifth aspect of the present invention, for example, when the impedance of each of the first impedance circuit and the second impedance circuit is Za and Zb, the bypass circuit is normally closed. No power is consumed by the impedance Zb, and it can be avoided that the voltage applied to the device is lowered by the voltage drop at the impedance Zb.

  On the other hand, since the second switch cuts off the bypass circuit at the time of overvoltage, only the voltage according to the ratio of two impedances of power supply voltage {Za / (Za + Zb)} is applied to the device, so that the device is protected from overvoltage. Can do.

  In the overvoltage protection circuit according to the sixth aspect or the seventh aspect of the present invention, for example, when the impedances of the first impedance circuit and the second impedance circuit are Za and Zb, the switch and the second switch operate at the time of overvoltage. Thus, only a voltage corresponding to the ratio of the two impedances of the power supply voltage {Za / (Za + Zb)} is applied to the device, so that the device can be protected from overvoltage, and the third switch operates to By cutting off, power consumption at the impedances Za and Zb is stopped. As a result, overheating of the impedances Za and Zb can be suppressed and the power rating can be reduced.

  In the overvoltage protection circuit according to the eighth aspect of the present invention, even if the supply voltage from the AC power supply is an excessive voltage, only a voltage corresponding to the ratio of the two impedances is applied to the device. Therefore, it is not necessary to design the equipment with a high voltage rating only for protection from an excessive voltage for a short time, which is reasonable.

  In the overvoltage protection circuit according to the ninth aspect of the present invention, the switch for turning on and off the alternating current needs bidirectionality, but the switch arranged on the downstream side of the DC power supply may be a one-way switch, so the cost of the switch is low. Can be achieved.

  In the power conversion device according to the tenth aspect of the present invention, the overvoltage protection circuit protects the converter circuit from an excessive AC voltage applied transiently or protects the inverter circuit from an excessive DC voltage applied transiently. be able to.

The circuit diagram of the apparatus provided with the overvoltage protection circuit which concerns on 1st Embodiment of this invention. The circuit diagram of the apparatus provided with the overvoltage protection circuit which concerns on 2nd Embodiment of this invention. The circuit diagram of a voltage detector. The circuit diagram of the apparatus provided with the overvoltage protection circuit which concerns on 3rd Embodiment of this invention. The circuit diagram of the apparatus provided with the overvoltage protection circuit which concerns on 4th Embodiment of this invention. The circuit diagram of the power converter device provided with the overvoltage protection circuit which concerns on 5th Embodiment of this invention. The circuit diagram of the power converter device provided with the overvoltage protection circuit which concerns on 6th Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following embodiments are specific examples of the present invention and do not limit the technical scope of the present invention.

<First Embodiment>
(1) Configuration of Overvoltage Protection Circuit 50 FIG. 1 is a circuit diagram of a device including an overvoltage protection circuit 50 according to the first embodiment of the present invention. In FIG. 1, the device 30 is supplied with power from a commercial power supply 90 via a pair of power supply lines 901 and 902. The overvoltage protection circuit 50 is connected between the commercial power supply 90 and the device 30.

  The overvoltage protection circuit 50 includes an overvoltage conduction circuit 10, a first impedance circuit 21, and a second impedance circuit 22.

(2) Detailed configuration of overvoltage protection circuit 50 (2-1) Overvoltage conduction circuit 10
The overvoltage conduction circuit 10 is composed of an element that allows current to flow when overvoltage occurs. As an element for passing a current at the time of overvoltage, a transient voltage suppressor, a Zener diode, a surge absorber, or an avalanche diode is employed.

  In the present embodiment, the overvoltage conduction circuit 10 is composed of one surge absorber. A surge absorber is a voltage-dependent element and has a high resistance in a normal state. However, when the applied voltage exceeds a predetermined voltage, the voltage is limited by abruptly decreasing the resistance. It can be carried out. Specific elements of the surge absorber include, but are not limited to, arresters and discharge tubes.

  The overvoltage conduction circuit 10 is connected in parallel with the device 30 between a pair of power supply lines 901 and 902. When the commercial power supply 90 is a multiphase power supply and overvoltage protection between phases is performed, the overvoltage conduction circuit 10 is connected between the power supply lines for each phase.

(2-2) First impedance circuit 21
The first impedance circuit 21 is a circuit configured such that an impedance that is a ratio of a voltage and a current in the circuit is Za.

  The first impedance circuit 21 is connected between the pair of power supply lines 901 and 902 in parallel with the device 30 and in series with the overvoltage conduction circuit 10.

(2-3) Second impedance circuit 22
The second impedance circuit 22 is a circuit configured such that an impedance that is a ratio of a voltage and a current in the circuit is Zb.

  The second impedance circuit 22 is connected between the commercial power supply 90 and the first impedance circuit 21 on the power supply line 902.

(3) Operation of Overvoltage Protection Circuit 50 For convenience of explanation, the voltage of the commercial power supply 90 is Vac, the voltage applied to the device 30 is Va, and the voltage applied to both ends of the second impedance circuit 22 is Vb.

  In FIG. 1, since the surge absorber of the overvoltage conduction circuit 10 is not conducted normally, the voltage Va = Vac−Vb is applied to the device 30.

  When the voltage Vac of the commercial power supply 90 suddenly fluctuates and becomes overvoltage, and the voltage Va exceeds the operation start voltage of the surge absorber, the surge absorber of the overvoltage conduction circuit 10 becomes conductive, and the commercial power supply 90-overvoltage conduction circuit 10-first A closed circuit of 1 impedance circuit 21 -second impedance circuit 22 -commercial power supply 90 is formed. At this time, only the voltage Va = Vac × Za / (Za + Zb) corresponding to the ratio of the two impedances of the voltage Vac is applied to the device 30. As a result, the device 30 is protected from overvoltage.

(4) Features of the first embodiment (4-1)
In the overvoltage protection circuit 50, when the surge absorber of the overvoltage conduction circuit 10 conducts at the time of overvoltage, only a voltage corresponding to the impedance ratio of the first impedance circuit 21 and the second impedance circuit 22 is applied to the device 30. 30 is protected from overvoltage.

(4-2)
Even if the supply voltage from the commercial power supply 90 is an excessive voltage, only a voltage corresponding to the ratio of the two impedances is applied to the device 30. Therefore, it is not necessary to design the device 30 with a high voltage rating only for protection from an excessive voltage for a short time, which is reasonable.

Second Embodiment
(1) Configuration of Overvoltage Protection Circuit 50 FIG. 2 is a circuit diagram of a device including an overvoltage protection circuit 50 according to the second embodiment of the present invention. In FIG. 2, the device 30 is supplied with power from a commercial power supply 90 via a pair of power supply lines 901 and 902. The overvoltage protection circuit 50 is connected between the commercial power supply 90 and the device 30.

  The overvoltage protection circuit 50 includes an overvoltage conduction circuit 10, a first impedance circuit 21, a second impedance circuit 22, and a voltage detector 33.

(2) Detailed configuration of overvoltage protection circuit 50 (2-1) Overvoltage conduction circuit 10
The overvoltage conduction circuit 10 employs a switch 11 instead of the surge absorber in the first embodiment. As shown in FIG. 2, the switch 11 is composed of a phototriac coupler, and a light emitting diode 11a is provided on the input side (between A1 and A2), and a phototriac 11b is provided on the output side (between B1 and B2). Yes. The equivalent circuit of the phototriac 11b has a configuration in which two photothyristors 111 and 112 are connected in parallel in opposite directions.

  The anode A1 of the light emitting diode 11a is connected to the power source Vc via the resistor R1. The cathode A2 of the light emitting diode 11a is connected to the control unit 40 through a signal line.

  The first anode B1 of the phototriac 11b is connected to the power supply line 901. The second anode B2 of the phototriac 11b is connected to the first impedance circuit 21.

  The light emitting diode 11a emits light when a current flows. When the phototriac 11b receives light from the light emitting diode 11a in a state where the potential of the first anode B1 is higher than the potential of the second anode B2, the photothyristor 111 is turned on. On the other hand, when light from the light emitting diode 11a is received in a state where the potential of the first anode B1 is smaller than the potential of the second anode B2, the photothyristor 112 is turned on.

  As described above, the phototriac 11b is a bidirectional element that operates with respect to a bidirectional applied voltage, and also operates at a high speed, and thus is used as a bidirectional high-speed switch.

  Note that the bidirectional high-speed switch is not limited to the phototriac, but may be a normal triac or a MOSFET connected so as to conduct in both directions. When another form of high-speed switch is used, a drive circuit corresponding to the form of the switch is appropriately used.

  The overvoltage conduction circuit 10 is connected in parallel with the device 30 between a pair of power supply lines 901 and 902. When overvoltage protection between phases is performed when the commercial power supply 90 is a multiphase power supply, the overvoltage conduction circuit 10 is connected between the power supply lines for each phase.

  Further, the control unit 40 performs operation control of the switch 11, that is, energization control to the light emitting diode 11a.

(2-2) First impedance circuit 21
The first impedance circuit 21 is a circuit configured such that an impedance that is a ratio of a voltage and a current in the circuit is Za.

  The first impedance circuit 21 is connected between the pair of power supply lines 901 and 902 in parallel with the device 30 and in series with the overvoltage conduction circuit 10.

(2-3) Second impedance circuit 22
The second impedance circuit 22 is a circuit configured such that an impedance that is a ratio of a voltage and a current in the circuit is Zb.

  The second impedance circuit 22 is connected between the commercial power supply 90 and the first impedance circuit 21 on the power supply line 902.

(2-4) Voltage detector 33
The voltage detector 33 is configured by an AC voltage detection circuit. There are various AC voltage detection circuits, and they are appropriately adopted depending on use conditions. For example, FIG. 3 is a circuit diagram of a general voltage detector 33. In FIG. 3, the voltage detector 33 includes a transformer circuit 331 and a converter circuit 332.

  The transformer circuit 331 is located on the input side and includes a primary winding 331a and a secondary winding 331b.

  The converter circuit 332 is a circuit in which a rectifying unit 332a formed of a rectifying diode and a smoothing capacitor 332b are connected in parallel.

  In the voltage detector 33, when an AC voltage is applied to the transformer circuit 331, the AC voltage is transformed by the transformer circuit 331. Then, the voltage across the secondary winding 331 b is input to the converter circuit 332.

  The transformed AC voltage input to the converter circuit 332 is converted into a DC voltage by the rectifying unit 332a and smoothed by the smoothing capacitor 332b. This smoothed DC voltage is input to the control unit 40. That is, a DC voltage corresponding to the voltage applied to the primary winding 331a is input to the control unit 40.

(3) Operation of Overvoltage Protection Circuit 50 For convenience of explanation, the voltage of the commercial power supply 90 is Vac, the voltage applied to the device 30 is Va, and the voltage applied to both ends of the second impedance circuit 22 is Vb.

  In FIG. 2, since the switch 11 of the overvoltage conduction circuit 10 is normally off, the voltage Va = Vac−Vb is applied to the device 30.

  When the voltage Vac of the commercial power supply 90 suddenly increases and the control unit 40 determines that the voltage output from the voltage detector 33 has exceeded the threshold value, the control unit 40 energizes the light emitting diode 11a of the switch 11. As a result, the phototriac 11b is turned on, and a closed circuit of commercial power supply 90-overvoltage conduction circuit 10-first impedance circuit 21-second impedance circuit 22-commercial power supply 90 is formed. At this time, only the voltage Va = Vac × Za / (Za + Zb) corresponding to the ratio of the two impedances of the voltage Vac is applied to the device 30. As a result, the device 30 is protected from overvoltage. In order to protect the device 30, the switch 11 is required to operate at high speed.

  When the control unit 40 determines that the voltage Vac of the commercial power supply 90 has dropped and the voltage output from the voltage detector 33 has fallen below the threshold for recovery, the control unit 40 turns off the light-emitting diode 11a of the switch 11 To do. As a result, the photo triac 11b is turned off and returns to normal operation.

(4) Features of the second embodiment (4-1)
In the overvoltage protection circuit 50, since the switch 11 of the overvoltage conduction circuit 10 is turned on at the time of overvoltage, only a voltage corresponding to the impedance ratio of the first impedance circuit 21 and the second impedance circuit 22 is applied to the device 30. 30 is protected from overvoltage.

(4-2)
Even if the supply voltage from the commercial power supply 90 is an excessive voltage, only a voltage corresponding to the ratio of the two impedances is applied to the device 30. Therefore, it is not necessary to design the device 30 with a high voltage rating only for protection from an excessive voltage for a short time, which is reasonable.

<Third Embodiment>
(1) Configuration of Overvoltage Protection Circuit 50 FIG. 4 is a circuit diagram of a device including an overvoltage protection circuit 50 according to the third embodiment of the present invention. In FIG. 4, the device 30 is supplied with power from a commercial power supply 90 via a pair of power supply lines 901 and 902. The overvoltage protection circuit 50 is connected between the commercial power supply 90 and the device 30.

  The overvoltage protection circuit 50 includes an overvoltage conduction circuit 10, a first impedance circuit 21, a second impedance circuit 22, a voltage detector 33, and a bypass circuit 35.

(2) Detailed Configuration of Overvoltage Protection Circuit 50 In the third embodiment, a bypass circuit 35 is added to the second embodiment, and an overvoltage conduction circuit 10, a first impedance circuit 21, a second impedance circuit 22, and The same voltage detector 33 is employed. Therefore, only the bypass circuit 35 will be described here.

(2-1) Bypass circuit 35
The bypass circuit 35 is a circuit that is connected in parallel to the second impedance circuit 22 and bypasses the second impedance circuit 22. The bypass circuit 35 includes the second switch 12. The second switch 12 opens and closes the bypass circuit 35. Here, opening and closing the bypass circuit 35 means making the bypass circuit 35 conductive or non-conductive to make it non-conductive.

(2-2) Second switch 12
The second switch 12 normally closes the bypass circuit 35, that is, keeps it in a conductive state. This is because if the bypass circuit 35 is left open (non-conducting state) during normal operation, the second impedance circuit 22 is always connected and power is always consumed, and the voltage applied to the device 30 is second. This is because the voltage is lowered by the voltage drop of the impedance Zb of the impedance circuit 22.

  On the other hand, in order to protect the device 30 during overvoltage, the bypass circuit 35 is quickly opened and the second impedance circuit 22 is connected, and the commercial power supply 90—overvoltage conduction circuit 10—first impedance circuit 21—second impedance circuit 22— It is necessary to configure a closed circuit called a commercial power supply 90. For this reason, the second switch 12 is required to operate at high speed.

  As the second switch 12, a triac, a MOSFET connected so as to conduct in both directions, or the like is employed. In the present embodiment, a phototriac coupler is employed as with the switch 11.

  As shown in FIG. 4, the second switch 12 is provided with a light emitting diode 12a on the input side (between C1 and C2) and a phototriac 12b on the output side (between D1 and D2). The equivalent circuit of the phototriac 12b has a configuration in which two photothyristors 121 and 122 are connected in parallel in opposite directions.

  The anode C1 of the light emitting diode 12a is connected to the power source Vc via the resistor R2. The cathode C2 of the light emitting diode 12a is connected to the control unit 40 via a signal line.

  The first anode D1 of the phototriac 12b is connected between the second impedance circuit 22 in the power supply line 902 and the device 30. The second anode D2 of the photo triac 12b is connected to the power line 902 between the second impedance circuit 22 and the commercial power source 90.

  The operating principle of the photothyristors 121 and 122 of the light-emitting diode 12a and the phototriac 12b is the same as the operating principle of the light-emitting diode 11a and the photothyristor 111 and 112 of the phototriac 11b in the switch 11, so that the description of the operation is omitted here. .

(3) Operation of Overvoltage Protection Circuit 50 In FIG. 4, the switch 11 of the overvoltage conduction circuit 10 is normally turned off and the bypass circuit 35 is in the conduction state with the second switch 12 closed, so that the voltage Va is applied to the device 30. = Vac is applied.

  When the voltage Vac of the commercial power supply 90 suddenly increases and the control unit 40 determines that the voltage output from the voltage detector 33 has exceeded the threshold, the control unit 40 energizes the light emitting diode 11a of the switch 11 to generate a photo The triac 11b is turned on. At the same time, the control unit 40 stops energization of the light emitting diode 12a of the second switch 12 and turns off the phototriac 12b.

  As a result, a closed circuit of commercial power supply 90-overvoltage conduction circuit 10-first impedance circuit 21-second impedance circuit 22-commercial power supply 90 is formed. At this time, only the voltage Va = Vac × Za / (Za + Zb) corresponding to the ratio of the two impedances of the voltage Vac is applied to the device 30. As a result, the device 30 is protected from overvoltage.

  When the control unit 40 determines that the voltage Vac of the commercial power supply 90 has dropped and the voltage output from the voltage detector 33 has fallen below the threshold for recovery, the control unit 40 turns off the light-emitting diode 11a of the switch 11 Then, the photo triac 11b is turned off. At the same time, the control unit 40 energizes the light emitting diode 12a of the second switch 12 to turn on the phototriac 12b. As a result, the normal operation is restored.

(4) Features of the third embodiment (4-1)
In the overvoltage protection circuit 50, since the second switch 12 is normally turned on and the bypass circuit 35 is closed, power is not consumed by the second impedance circuit 22, and the voltage applied to the device 30 is the second voltage. It can also be avoided that the voltage drop in the impedance circuit 22 is lowered.

(4-2)
In addition, when overvoltage occurs, the switch 11 of the overvoltage conduction circuit 10 is turned on and the second switch 12 is turned off, so that the device 30 has only a voltage corresponding to the impedance ratio of the first impedance circuit 21 and the second impedance circuit 22. Since it is not applied, the device 30 is protected from overvoltage.

(4-3)
Even if the supply voltage from the commercial power supply 90 is an excessive voltage, only a voltage corresponding to the ratio of the two impedances is applied to the device 30. Therefore, it is not necessary to design the device 30 with a high voltage rating only for protection from an excessive voltage for a short time, which is reasonable.

<Fourth embodiment>
(1) Configuration of Overvoltage Protection Circuit 50 FIG. 5 is a circuit diagram of an apparatus including an overvoltage protection circuit 50 according to the fourth embodiment of the present invention. In FIG. 5, the device 30 is supplied with power from a commercial power supply 90 via a pair of power supply lines 901 and 902. The overvoltage protection circuit 50 is connected between the commercial power supply 90 and the device 30.

  The overvoltage protection circuit 50 includes an overvoltage conduction circuit 10, a first impedance circuit 21, a second impedance circuit 22, a voltage detector 33, a bypass circuit 35, and a third switch 13.

(2) Detailed Configuration of Overvoltage Protection Circuit 50 In the fourth embodiment, a third switch 13 is added to the third embodiment, and an overvoltage conduction circuit 10, a first impedance circuit 21, a second impedance circuit 22, The same voltage detector 33 and bypass circuit 35 are employed. Therefore, only the third switch 13 will be described here.

(2-1) Third switch 13
The third switch 13 opens and closes the power line 901. Here, opening and closing the power supply line 901 means that the power supply line 901 is turned on or off to make it non-conductive.

  The third switch 13 normally closes the power supply line 901, that is, keeps it conductive. On the other hand, at the time of overvoltage, the switch 11 is turned on, the second switch 12 is turned off, and a closed circuit of the commercial power supply 90-overvoltage conduction circuit 10-first impedance circuit 21-second impedance circuit 22-commercial power supply 90 is formed. After the protection operation of the device 30 is performed, the third switch 13 is turned off and the power line 901 is shut off.

  The purpose of cutting off the power supply line 901 is to stop power consumption in the first impedance circuit 21 and the second impedance circuit 22, and it is possible to suppress overheating of the first impedance circuit 21 and the second impedance circuit 22. The power rating can be reduced, and the cost can be reduced.

  Since the third switch 13 is not required to have high speed like the switch 11 and the second switch 12, a relay circuit is employed in this embodiment.

  As shown in FIG. 5, the third switch 13 includes a relay contact 13a for opening and closing the power supply line 901, a relay coil 13b for operating the relay contact 13a, and a transistor 13c for energizing and de-energizing the relay coil 13b. Is included. One end of the relay coil 13b is connected to the positive electrode of the power source Vb, and the other end is connected to the collector side of the transistor 13c. The controller 40 switches between the presence and absence of the base current of the transistor 13c, turns on and off the collector and the emitter, and energizes and de-energizes the relay coil 13b.

(3) Operation of Overvoltage Protection Circuit 50 In FIG. 5, normally, the switch 11 of the overvoltage conduction circuit 10 is turned off, the bypass circuit 35 is in the conduction state with the second switch 12 closed, and the third switch 13 is a power source. Since the line 901 is in a conducting state, the voltage Va = Vac is applied to the device 30.

  When the voltage Vac of the commercial power supply 90 suddenly increases and the control unit 40 determines that the voltage output from the voltage detector 33 has exceeded the threshold, the control unit 40 energizes the light emitting diode 11a of the switch 11 to generate a photo The triac 11b is turned on. At the same time, the control unit 40 stops energization of the light emitting diode 12a of the second switch 12 and turns off the phototriac 12b.

  As a result, a closed circuit of commercial power supply 90-overvoltage conduction circuit 10-first impedance circuit 21-second impedance circuit 22-commercial power supply 90 is formed. At this time, only the voltage Va = Vac × Za / (Za + Zb) corresponding to the ratio of the two impedances of the voltage Vac is applied to the device 30. As a result, the device 30 is protected from overvoltage.

  Thereafter, when the overvoltage state continues, the third switch 13 cuts off the power supply line 901 and stops power consumption in the first impedance circuit 21 and the second impedance circuit 22.

  When the control unit 40 determines that the voltage Vac of the commercial power supply 90 has dropped and the voltage output from the voltage detector 33 has fallen below the threshold for recovery, the control unit 40 turns off the light-emitting diode 11a of the switch 11 Then, the photo triac 11b is turned off. At the same time, the control unit 40 energizes the light emitting diode 12a of the second switch 12 to turn on the phototriac 12b. Further, the third switch 13 is turned on and the power supply line 901 is connected to return to the normal operation.

(4) Features of the fourth embodiment (4-1)
In the overvoltage protection circuit 50, since the second switch 12 is normally turned on and the bypass circuit 35 is closed, power is not consumed by the second impedance circuit 22, and the voltage applied to the device 30 is the second voltage. It can also be avoided that the voltage drop in the impedance circuit 22 is lowered.

(4-2)
In addition, when overvoltage occurs, the switch 11 of the overvoltage conduction circuit 10 is turned on and the second switch 12 is turned off, so that the device 30 has only a voltage corresponding to the impedance ratio of the first impedance circuit 21 and the second impedance circuit 22. Since it is not applied, the device 30 is protected from overvoltage.

(4-3)
Further, the third switch 13 cuts off the power supply line 901 to stop power consumption in the first impedance circuit 21 and the second impedance circuit 22. As a result, overheating of the first impedance circuit 21 and the second impedance circuit 22 can be suppressed, and the power rating can be reduced.

(4-4)
Even if the supply voltage from the commercial power supply 90 is an excessive voltage, only a voltage corresponding to the ratio of the two impedances is applied to the device 30. Therefore, it is not necessary to design the device 30 with a high voltage rating only for protection from an excessive voltage for a short time, which is reasonable.

<Fifth Embodiment>
(1) Configuration of Power Converter 200 FIG. 6 is a circuit diagram of a power converter 200 including an overvoltage protection circuit 100 according to the fifth embodiment of the present invention. In FIG. 6, the power conversion device 200 includes a DC power supply unit 80, an inverter 95, and an overvoltage protection circuit 100.

  The inverter 95 is supplied with power from the DC power supply unit 80 via a pair of power supply lines 801 and 802. The overvoltage protection circuit 100 is connected between the DC power supply unit 80 and the inverter 95.

(1-1) DC power supply unit 80
The DC power supply unit 80 includes a rectifying unit 81 and a smoothing capacitor 82 connected in parallel with the rectifying unit 81.

  The rectifying unit 81 is configured in a bridge shape by four diodes D1a, D1b, D2a, and D2b. Specifically, the diodes D1a and D1b and D2a and D2b are respectively connected in series. The cathode terminals of the diodes D1a and D2a are both connected to the plus side terminal of the smoothing capacitor 82 and function as the positive side output terminal of the rectifying unit 81. The anode terminals of the diodes D1b and D2b are both connected to the minus terminal of the smoothing capacitor 82 and function as the negative output terminal of the rectifier 81.

  A connection point between the diode D1a and the diode D1b is connected to one pole of the commercial power supply 90. A connection point between the diode D2a and the diode D2b is connected to the other pole of the commercial power supply 90. The rectifying unit 81 rectifies the AC voltage output from the commercial power supply 90 to generate a DC voltage, and supplies this to the smoothing capacitor 82.

  The smoothing capacitor 82 smoothes the voltage rectified by the rectifying unit 81. The smoothed voltage Vdc is applied to the inverter 95 connected to the output side of the smoothing capacitor 82.

  In addition, as a kind of capacitor | condenser, although an electrolytic capacitor, a film capacitor, a tantalum capacitor etc. are mentioned, in this embodiment, an electrolytic capacitor is employ | adopted as the smoothing capacitor 82. FIG.

  The DC power supply unit 80 can be rephrased as a converter circuit that converts an AC voltage into a DC voltage.

(1-2) Inverter 95
The inverter 95 includes a plurality of IGBTs (insulated gate bipolar transistors, hereinafter simply referred to as transistors) and a plurality of free-wheeling diodes. The inverter 95 is applied with the voltage Vdc from the smoothing capacitor 82, and each transistor is turned on and off at the timing instructed by the gate drive circuit 96, thereby generating a drive voltage for driving the motor 150. The motor 150 is, for example, a compressor motor or a fan motor of a heat pump type air conditioner.

  In addition, although the inverter 95 of this embodiment is a voltage source inverter, it is not limited to it, A current source inverter may be sufficient.

(1-3) Gate drive circuit 96
The gate drive circuit 96 changes the on / off state of each transistor of the inverter 95 based on a command from the control unit 40.

(1-4) Overvoltage protection circuit 100
The overvoltage protection circuit 100 includes an overvoltage conduction circuit 60, a first impedance circuit 71, a second impedance circuit 72, a voltage detector 83, a bypass circuit 85, and a third switch 63.

(2) Detailed Configuration of Overvoltage Protection Circuit 100 The fifth embodiment is different from the first to fourth embodiments already described in that the overvoltage protection circuit 100 is provided in the DC section. Therefore, in view of the fact that each component is also replaced from the AC specification to the DC specification, the description will be given again by changing the code even if the names are the same.

(2-1) Overvoltage conduction circuit 60
The overvoltage conduction circuit 60 employs a switch 61 instead of the switch 11 in the fourth embodiment.

  As shown in FIG. 6, the switch 61 includes a photocoupler 61a, a drive circuit 61b, and a transistor 61c. The photocoupler 61a includes a light emitting diode 611 and a phototransistor 612.

  The light emitting diode 611 of the photocoupler 61a is connected to the input side (between E1 and E2) of the switch 61. The anode E1 of the light emitting diode 611 is connected to the power source Vc via the resistor R1. The cathode E2 of the light emitting diode 611 is connected to the control unit 40 via a signal line. The phototransistor 612 is connected between the drive circuit 61b and GND.

  A transistor 61c is provided on the output side of the switch 61 (between F1 and F2). The collector F1 of the transistor 61c is connected to the power supply line 801. The emitter F2 of the transistor 61c is connected to the first impedance circuit 71.

  The control signal of the control unit 40 is input to the drive circuit 61b through the photocoupler 61a. A driving power supply (not shown) is connected to the driving circuit 61b. When the control unit 40 turns on the signal line of the light emitting diode 611, the light emitting diode 611 emits light and the phototransistor 612 becomes conductive. While the phototransistor 612 is conducting, a driving signal is output from the driving circuit 61b to the base of the transistor 61c, and the collector F1-emitter F2 of the transistor 61c is conducted.

  Conversely, when the control unit 40 turns off the signal line of the light emitting diode 611, the light emitting diode 611 does not emit light, and the phototransistor 612 does not conduct. While the phototransistor 612 is not conducting, the collector F1 and the emitter F2 of the transistor 61c are not conducting.

  As described above, when the DC circuit is opened and closed, a one-way switch may be used. Therefore, bidirectionality when the AC circuit is opened and closed is not required, and there is a cost merit. The configuration of the one-way switch is not limited to this embodiment, but it is desirable that the switch operation can be performed at high speed like a semiconductor switch.

  The overvoltage conduction circuit 60 is connected in parallel with the device 30 between the pair of power supply lines 801 and 802.

(2-2) First impedance circuit 71
The first impedance circuit 71 is a circuit configured such that an impedance that is a ratio of a voltage and a current in the circuit is Za. In general, a resistance element is employed.

  The first impedance circuit 71 is connected between the pair of power supply lines 801 and 802 in parallel with the inverter 95 and in series with the overvoltage conduction circuit 60.

(2-3) Second impedance circuit 72
The second impedance circuit 72 is a circuit configured such that an impedance that is a ratio of a voltage and a current in the circuit is Zb. In general, a resistance element is employed.

  The second impedance circuit 72 is connected between the DC power supply unit 80 and the first impedance circuit 71 on the power supply line 802.

(2-4) Voltage detector 83
The voltage detector 83 is connected to the output side of the smoothing capacitor 82, and detects the voltage across the smoothing capacitor 82, that is, the value of the smoothed voltage Vdc. For example, the voltage detector 83 is configured such that two resistors connected in series with each other are connected in parallel to the smoothing capacitor 82 and the voltage Vdc is divided. The voltage value at the connection point between the two resistors is input to the control unit 40.

(2-5) Bypass circuit 85
The bypass circuit 85 is a circuit that is connected in parallel to the second impedance circuit 72 and bypasses the second impedance circuit 72. The bypass circuit 85 has a second switch 62. The second switch 62 opens and closes the bypass circuit 85. Here, opening and closing the bypass circuit 85 means that the bypass circuit 35 is turned on or off to make it non-conductive.

(2-6) Second switch 62
The second switch 62 normally closes the bypass circuit 85, that is, keeps it in a conductive state. This is because if the bypass circuit 85 is left open (non-conducting state) during normal operation, power is always consumed by the second impedance circuit 72, and the voltage applied to the inverter 95 is the voltage of the impedance Zb of the second impedance circuit 72. This is because it is lowered by the amount of descent.

  On the other hand, in order to protect the inverter 95 at the time of overvoltage, the bypass circuit 85 is quickly opened, and a closed circuit of DC power supply unit 80-overvoltage conduction circuit 60-first impedance circuit 71-second impedance circuit 72-DC power supply unit 80. Need to be configured. For this reason, the second switch 62 is required to operate at high speed. In the present embodiment, the same switch as the switch 61 is employed. The switch is not limited to this embodiment.

  As shown in FIG. 6, in the second switch 62, a light emitting diode 621 of a photocoupler 62a is provided on the input side (between G1 and G2), and a transistor 62c is provided on the output side (between H1 and H2). The anode G1 of the light emitting diode 621 is connected to the power source Vc via the resistor R2. The cathode G2 of the light emitting diode 621 is connected to the control unit 40 via a signal line.

  The collector H1 of the transistor 62c is connected between the second impedance circuit 72 in the power supply line 802 and the inverter 95. The emitter H2 of the transistor 62c is connected to the power supply line 802 between the second impedance circuit 72 and the DC power supply unit 80.

  Since the operation principle of the second switch 62 is the same as that of the switch 61, the description of the operation is omitted here.

(2-7) Third switch 63
The third switch 63 opens and closes the power line 801. Here, opening and closing the power supply line 801 is to turn the power supply line 801 on or off to make it non-conductive.

  The third switch 63 normally closes the power supply line 801, that is, keeps it conductive. On the other hand, at the time of overvoltage, the switch 61 is turned on, the second switch 62 is turned off, and a closed circuit of DC power supply unit 80-overvoltage conduction circuit 60-first impedance circuit 71-second impedance circuit 72-DC power supply unit 80 is formed. After the configuration and the protective operation of the inverter 95 is performed, the third switch 63 is turned off and the power line 801 is shut off.

  The purpose of cutting off the power supply line 801 is to stop power consumption in the first impedance circuit 71 and the second impedance circuit 72, and it is possible to suppress overheating of the first impedance circuit 71 and the second impedance circuit 72. The power rating can be reduced, and the cost can be reduced.

  Since the third switch 63 does not require high speed like the switch 61 and the second switch 62, a relay circuit is employed in the present embodiment.

  As shown in FIG. 6, the third switch 63 includes a relay contact 63a for opening and closing the power supply line 801, a relay coil 63b for operating the relay contact 63a, and a transistor 63c for energizing and de-energizing the relay coil 63b. Is included. One end of the relay coil 63b is connected to the positive electrode of the power source Vb, and the other end is connected to the collector side of the transistor 63c. The controller 40 switches between the presence and absence of the base current of the transistor 63c, turns on and off the collector and the emitter, and performs energization and de-energization of the relay coil 63b.

(3) Operation of Overvoltage Protection Circuit 50 In FIG. 6, normally, the switch 61 of the overvoltage conduction circuit 60 is turned off, the bypass circuit 85 is in the conduction state with the second switch 62 closed, and the third switch 63 is a power source. Since the line 801 is in a conductive state, the voltage Va = Vdc is applied to the inverter 95.

  When the voltage Vdc of the DC power supply unit 80 increases rapidly and the control unit 40 determines that the voltage output from the voltage detector 83 exceeds the threshold value, the control unit 40 energizes the light emitting diode 611 of the switch 61, The transistor 61c is turned on. At the same time, the control unit 40 stops energization of the light emitting diode 621 of the second switch 62 and turns off the transistor 62c.

  As a result, a closed circuit of the DC power supply unit 80-overvoltage conduction circuit 60-first impedance circuit 71-second impedance circuit 72-DC power supply unit 80 is formed. At this time, only the voltage Va = Vdc × Za / (Za + Zb) corresponding to the ratio of the two impedances of the voltage Vdc is applied to the inverter 95. As a result, the inverter 95 is protected from overvoltage.

  Thereafter, when the overvoltage state continues, the third switch 63 cuts off the power supply line 801 and stops the power consumption in the first impedance circuit 71 and the second impedance circuit 72.

  When the control unit 40 determines that the voltage Vac of the commercial power supply 90 and the voltage Vdc of the DC power supply unit 80 are decreased and the voltage output from the voltage detector 83 is lower than the threshold for recovery, the control unit 40 switches the switch 61. The light-emitting diode 611 is turned off, and the transistor 61c is turned off. At the same time, the control unit 40 energizes the light emitting diode 621 of the second switch 62 to turn on the transistor 62c. Further, by turning on the third switch 63 and connecting the power supply line 801, the normal operation is restored.

(4) Features of the fifth embodiment (4-1)
In the overvoltage protection circuit 100, since the second switch 62 is normally turned on and the bypass circuit 85 is closed, power is not consumed by the second impedance circuit 72, and the voltage applied to the inverter 95 is the second voltage. It can also be avoided that the voltage drops by the voltage drop in the impedance circuit 72.

(4-2)
In addition, when overvoltage occurs, the switch 61 of the overvoltage conduction circuit 60 is turned on and the second switch 62 is turned off, so that the inverter 95 has only a voltage corresponding to the impedance ratio of the first impedance circuit 71 and the second impedance circuit 72. Since it is not applied, the inverter 95 is protected from overvoltage.

(4-3)
Further, the third switch 63 cuts off the power supply line 801 to stop power consumption in the first impedance circuit 71 and the second impedance circuit 72. As a result, overheating of the first impedance circuit 71 and the second impedance circuit 72 can be suppressed, and the power rating can be reduced.

(4-4)
Furthermore, since the switch 61 and the second switch 62 disposed on the downstream side of the DC power supply unit 80 may be unidirectional switches, the cost of the switches can be reduced.

<Sixth Embodiment>
(1) Configuration of Overvoltage Protection Circuit 100 FIG. 7 is a circuit diagram of a power conversion device 200 including the overvoltage protection circuit 100 according to the sixth embodiment of the present invention. In FIG. 7, the inverter 95 is supplied with power from a DC power supply unit 80 via a pair of power supply lines 801 and 802. A part of the overvoltage protection circuit 100 is connected between the commercial power supply 90 and the DC power supply unit 80, and the other part is connected between the DC power supply unit 80 and the inverter 95.

  The overvoltage protection circuit 100 includes an overvoltage conduction circuit 60, a first impedance circuit 71, a second impedance circuit 72, a voltage detector 33, a bypass circuit 85, and a third switch 13.

  The difference between the sixth embodiment and the fifth embodiment already described is that a voltage detector and a third switch, which are components of the overvoltage protection circuit 100, are provided between the commercial power supply 90 and the DC power supply unit 80. It is that. That is, the arrangement of the voltage detector and the third switch is the same as the arrangement of the voltage detector 33 and the third switch 13 in the fourth embodiment. Therefore, in view of the fact that the voltage detector and the third switch are replaced from the DC specification to the AC specification, the voltage detector 33 and the third switch 13 of the fourth embodiment are employed.

  Therefore, the content of each component includes the voltage detector 33 and the third switch 13 of the fourth embodiment, the overvoltage conduction circuit 60 of the fifth embodiment, the first impedance circuit 71, the second impedance circuit 72, and the bypass circuit 85. Therefore, the description is omitted here and only the operation is described.

(2) Operation of Overvoltage Protection Circuit 50 In FIG. 7, normally, the switch 61 of the overvoltage conduction circuit 60 is turned off, the bypass circuit 85 is in the conduction state with the second switch 62 closed, and the third switch 63 is a power source. Since the line 901 is in a conducting state, the voltage Va = Vdc is applied to the inverter 95.

  When the control unit 40 determines that the voltage output from the voltage detector 33 has exceeded the threshold value due to the fluctuation of the voltage Vac of the commercial power supply 90, the control unit 40 energizes the light emitting diode 611 of the switch 61. Then, the transistor 61c is turned on. At the same time, the control unit 40 stops energization of the light emitting diode 621 of the second switch 62 and turns off the transistor 62c.

  As a result, a closed circuit of the DC power supply unit 80-overvoltage conduction circuit 60-first impedance circuit 71-second impedance circuit 72-DC power supply unit 80 is formed. At this time, only the voltage Va = Vdc × Za / (Za + Zb) corresponding to the ratio of the two impedances of the voltage Vdc is applied to the inverter 95. As a result, the inverter 95 is protected from overvoltage.

  Thereafter, the third switch 13 cuts off the power supply line 901 and stops power consumption in the first impedance circuit 71 and the second impedance circuit 72.

(3) Features of the sixth embodiment (3-1)
In the overvoltage protection circuit 100, since the second switch 62 is normally turned on and the bypass circuit 85 is closed, power is not consumed by the second impedance circuit 72, and the voltage applied to the inverter 95 is the second voltage. It can also be avoided that the voltage drops by the voltage drop in the impedance circuit 72.

(3-2)
In addition, when overvoltage occurs, the switch 61 of the overvoltage conduction circuit 60 is turned on and the second switch 62 is turned off, so that the inverter 95 has only a voltage corresponding to the impedance ratio of the first impedance circuit 71 and the second impedance circuit 72. Since it is not applied, the inverter 95 is protected from overvoltage.

(3-3)
Further, the third switch 13 cuts off the power supply line 901 to stop the power consumption in the first impedance circuit 71 and the second impedance circuit 72. As a result, overheating of the first impedance circuit 71 and the second impedance circuit 72 can be suppressed, and the power rating can be reduced.

(3-4)
Furthermore, since the switch 61 and the second switch 62 disposed on the downstream side of the DC power supply unit 80 may be unidirectional switches, the cost of the switches can be reduced.

<Other embodiments>
(A)
The embodiment in which the bypass circuit 35 in the third embodiment shown in FIG. 4 is connected in parallel to the second impedance circuit 22 in the first embodiment shown in FIG. 1 is also effective.

  Normally, the second switch 12 is turned on and the bypass circuit 35 is closed, so that no power is consumed in the second impedance circuit 22, and the voltage applied to the device 30 is equal to the voltage drop in the second impedance circuit 22. Only lowering can be avoided.

(B)
An embodiment in which the power supply line 901 in the first embodiment shown in FIG. 1 and the second embodiment shown in FIG. 2 is opened and closed by the third switch 13 in the fourth embodiment shown in FIG. 5 is also effective.

  Since the third switch 13 stops the power consumption in the first impedance circuit 21 and the second impedance circuit 22 by cutting off the power supply line 901, the power rating of the first impedance circuit 21 and the second impedance circuit 22 is reduced. Can do.

(C)
The overvoltage protection circuit 50 according to the first embodiment shown in FIG. 1, the second embodiment shown in FIG. 2, and the third embodiment shown in FIG. 4 is an overvoltage protection circuit for an AC voltage. When the power source is a DC power source or when a DC power source unit that rectifies an AC power source is provided in the device, each component may be replaced with the DC specification and provided downstream of the DC power source unit.

(D)
The sixth embodiment is different from the fifth embodiment in that the voltage detector and the third switch are provided between the commercial power supply 90 and the DC power supply unit 80, but only the voltage detector is commercialized. You may make it provide between the power supply 90 and the DC power supply part 80. FIG.

(E)
In the fifth embodiment and the sixth embodiment, the example in which the overvoltage protection circuit is provided inside the device has been described, but the device is not limited to the one having the converter circuit and the inverter circuit.

(F)
In the third embodiment, the third switch is turned off after the protection operation of the device 30 is performed. However, the third switch may be turned off after a predetermined time has elapsed since the protection operation was performed.

(G)
In the third embodiment, the third switch is turned off after the protection operation of the device 30 is performed. However, the device further includes a device voltage detector that detects the device voltage V, and the device voltage exceeds a predetermined value. Sometimes the third switch may be turned off.

(H)
In the first embodiment, a surge absorber has been described as an example of an element that allows a current to flow during overvoltage. In this case, as described in the first embodiment, since the voltage is not held by the element itself when conducting, the power supply voltage is divided by the impedance ratio and applied to the device 30. However, when an overvoltage circuit is applied to an overvoltage circuit, such as a varistor or Zener diode that maintains a predetermined voltage when the element itself is on, the voltage obtained by removing the retained voltage from the power supply voltage. Is divided by the impedance ratio. In this case, since only the voltage obtained by adding the holding voltage of the element and the voltage divided by the impedance is applied to the device, the applied voltage to the device is limited, and the device can be protected from overvoltage.

  INDUSTRIAL APPLICABILITY The present invention is useful for equipment used in an area where power supply voltage is likely to fluctuate, such as a refrigeration apparatus.

10, 60 Overvoltage conduction circuit 11, 61 Switch 12, 62 Second switch 13, 63 Third switch 21, 71 First impedance circuit 22, 72 Second impedance circuit 33, 83 Voltage detector 35, 85 Bypass circuit 50, 100 Overvoltage protection circuit 80 DC power supply (DC power supply, converter circuit)
90 Commercial power (AC power)
95 Inverter (Inverter circuit)

JP 2009-207329 A

  The present invention relates to an overvoltage protection circuit and a power conversion device including the same.

  A device used in an area where the power supply voltage is likely to fluctuate may cause a failure of the device depending on the countermeasure against the voltage rise. Therefore, an overvoltage protection circuit as disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2009-207329) is provided. This overvoltage protection circuit is configured to shut off the power supply with a relay when the voltage is equal to or higher than a predetermined voltage.

  However, the time required for the power supply voltage to become excessive is extremely short, and the response is slow and it is difficult to reliably protect it by the interruption by the relay. In particular, a semiconductor element such as a semiconductor element that has a short time to withstand overvoltage cannot be protected by being interrupted by a relay. Further, increasing the breakdown voltage of a semiconductor element or the like only for an instantaneous excessive voltage leads to an increase in cost and size.

  Accordingly, an object of the present invention is to provide a small and low-cost overvoltage protection circuit that protects a device from a momentary excessive voltage, and a power conversion device including the same.

An overvoltage protection device according to a first aspect of the present invention is an overvoltage protection circuit connected between a power supply and a device to which power is supplied from the power supply, and includes an overvoltage conduction circuit, a first impedance circuit, 2 impedance circuit. The overvoltage conduction circuit is connected in parallel with the device between a pair of power supply lines connecting the power source and the device, and allows current to flow when overvoltage occurs. The first impedance circuit is connected between the pair of power supply lines in parallel with the device and in series with the overvoltage conduction circuit. The second impedance circuit is connected between the power supply in the power supply line and the first impedance circuit. The overvoltage conduction circuit includes any one of a transient voltage suppressor, a Zener diode, a surge absorber, and an avalanche diode as an element that allows a current to flow when overvoltage occurs.

  In this overvoltage protection circuit, a closed circuit of [power supply-overvoltage conduction circuit-first impedance circuit-second impedance circuit-power supply] is configured by conducting the overvoltage conduction circuit at the time of overvoltage. As a result, since only a voltage corresponding to the ratio of the impedances of the two impedance circuits is applied to the device, the device can be protected from overvoltage.

Further, the transient voltage suppressor, the Zener diode, the surge absorber, and the avalanche diode are all elements that operate with a short response time with respect to the voltage transient fluctuation. Therefore, in this overvoltage protection circuit, since the element conducts at the time of overvoltage, only a voltage according to the impedance ratio of the two impedance circuits is applied to the device, so that the device can be protected from overvoltage.

An overvoltage protection circuit according to a second aspect of the present invention is the overvoltage protection circuit according to the first aspect, and further includes a voltage detector that detects the voltage of the power supply. The overvoltage conduction circuit has a switch that opens and closes between the power supply line and the first impedance circuit. This switch is turned on when the detection value by the voltage detector exceeds a predetermined threshold value, and conducts between the power supply line and the first impedance circuit.

  In this overvoltage protection circuit, for example, when the impedance of each of the first impedance circuit and the second impedance circuit is Za and Zb, the switch causes the power supply line and the first impedance circuit to conduct at the time of overvoltage. Since only a voltage according to the ratio {Za / (Za + Zb)} of the two impedances of the power supply voltage is applied, the device can be protected from overvoltage.

An overvoltage protection circuit according to a third aspect of the present invention is the overvoltage protection circuit according to the first aspect, and further includes a voltage detector and a bypass circuit. The voltage detector detects the voltage of the power supply. The bypass circuit is a circuit that bypasses the second impedance circuit. The bypass circuit has a second switch that opens and closes the bypass circuit. The second switch normally closes the bypass circuit, and shuts off the bypass circuit when the value detected by the voltage detector exceeds a predetermined threshold value.

  In this overvoltage protection circuit, for example, when the impedances of the first impedance circuit and the second impedance circuit are Za and Zb, the bypass circuit is normally closed, so that power is not consumed by the impedance Zb. It is also possible to avoid the voltage applied to the device being lowered by the voltage drop at the impedance Zb.

  On the other hand, since the second switch cuts off the bypass circuit at the time of overvoltage, only the voltage according to the ratio of two impedances of power supply voltage {Za / (Za + Zb)} is applied to the device, so that the device is protected from overvoltage. Can do.

An overvoltage protection circuit according to a fourth aspect of the present invention is the overvoltage protection circuit according to the second aspect , and further includes a bypass circuit. The bypass circuit is a circuit that bypasses the second impedance circuit. The bypass circuit has a second switch that opens and closes the bypass circuit. The second switch normally closes the bypass circuit, and shuts off the bypass circuit when the detection value by the voltage detector exceeds a predetermined threshold value.

  In this overvoltage protection circuit, for example, when the impedances of the first impedance circuit and the second impedance circuit are Za and Zb, the bypass circuit is normally closed, so that power is not consumed by the impedance Zb. It is also possible to avoid the voltage applied to the device being lowered by the voltage drop at the impedance Zb.

  On the other hand, since the second switch cuts off the bypass circuit at the time of overvoltage, only the voltage according to the ratio of two impedances of power supply voltage {Za / (Za + Zb)} is applied to the device, so that the device is protected from overvoltage. Can do.

An overvoltage protection circuit according to a fifth aspect of the present invention is the overvoltage protection circuit according to the first aspect, and further includes a voltage detector and a third switch. The voltage detection value detects the voltage of the power supply. The third switch opens and closes the power line. The third switch normally turns on the power line, and shuts off the power line after the operation of the second switch when the value detected by the voltage detector exceeds a predetermined threshold.

  In this overvoltage protection circuit, for example, when the impedances of the first impedance circuit and the second impedance circuit are Za and Zb, the switch and the second switch operate at the time of overvoltage, so that the device has two impedances of the power supply voltage. Since only a voltage corresponding to the ratio {Za / (Za + Zb)} is applied, the device can be protected from overvoltage, and further, the power at the impedances Za and Zb can be obtained by operating the third switch to cut off the power line. Stop consumption. As a result, overheating of the impedances Za and Zb can be suppressed and the power rating can be reduced.

An overvoltage protection circuit according to a sixth aspect of the present invention is the overvoltage protection circuit according to any one of the second to fourth aspects, and further includes a third switch. The third switch opens and closes the power line. The third switch normally turns on the power line, and shuts off the power line after the operation of the second switch when the value detected by the voltage detector exceeds a predetermined threshold.

  In this overvoltage protection circuit, for example, when the impedances of the first impedance circuit and the second impedance circuit are Za and Zb, the switch and the second switch operate at the time of overvoltage, so that the device has two impedances of the power supply voltage. Since only a voltage corresponding to the ratio {Za / (Za + Zb)} is applied, the device can be protected from overvoltage, and further, the power at the impedances Za and Zb can be obtained by operating the third switch to cut off the power line. Stop consumption. As a result, overheating of the impedances Za and Zb can be suppressed and the power rating can be reduced.

An overvoltage protection circuit according to a seventh aspect of the present invention is the overvoltage protection circuit according to any one of the first to sixth aspects, wherein the power supply is an AC power supply.

  In this overvoltage protection circuit, even if the supply voltage from the AC power supply is an excessive voltage, only a voltage corresponding to the ratio of the two impedances is applied to the device. Therefore, it is not necessary to design the equipment with a high voltage rating only for protection from an excessive voltage for a short time, which is reasonable.

An overvoltage protection circuit according to an eighth aspect of the present invention is the overvoltage protection circuit according to any one of the first to sixth aspects, wherein the power supply is a DC power supply.

  In this overvoltage protection circuit, the switch for turning on and off the alternating current needs bidirectionality, but the switch arranged on the downstream side of the DC power supply may be a one-way switch, so that the cost of the switch can be reduced.

A power converter according to a ninth aspect of the present invention includes a converter circuit, an inverter circuit, and an overvoltage protection circuit according to a seventh aspect . The converter circuit converts the AC voltage into a DC voltage. The inverter circuit converts a DC voltage into an AC voltage.

  In this power converter, the overvoltage protection circuit can protect the converter circuit from excessively applied excessive AC voltage or the inverter circuit from transiently applied excessive DC voltage.

  A power converter according to a tenth aspect of the present invention includes an inverter circuit and an overvoltage protection circuit according to an eighth aspect. The inverter circuit converts the voltage of the DC power source into an AC voltage.

  In this power converter, the overvoltage protection circuit can protect the converter circuit from excessively applied excessive AC voltage or the inverter circuit from transiently applied excessive DC voltage.

  In the overvoltage protection device according to the first aspect of the present invention, a closed circuit of [power supply-overvoltage conduction circuit-first impedance circuit-second impedance circuit-power supply] is configured by conducting the overvoltage conduction circuit at the time of overvoltage. The As a result, since only a voltage corresponding to the ratio of the impedances of the two impedance circuits is applied to the device, the device can be protected from overvoltage.

In addition , since the device conducts at the time of overvoltage, only a voltage corresponding to the impedance ratio of the two impedance circuits is applied to the device, so that the device can be protected from the overvoltage.

In the overvoltage protection circuit according to the second aspect of the present invention, for example, when the impedances of the first impedance circuit and the second impedance circuit are Za and Zb, the switch is connected between the power supply line and the first impedance circuit when overvoltage occurs. By conducting the current, only a voltage corresponding to the ratio of two impedances of the power supply voltage {Za / (Za + Zb)} is applied to the device, so that the device can be protected from overvoltage.

In the overvoltage protection circuit according to the third aspect or the fourth aspect of the present invention, for example, when the impedance of each of the first impedance circuit and the second impedance circuit is Za and Zb, the bypass circuit is normally closed. No power is consumed by the impedance Zb, and it can be avoided that the voltage applied to the device is lowered by the voltage drop at the impedance Zb.

  On the other hand, since the second switch cuts off the bypass circuit at the time of overvoltage, only the voltage according to the ratio of two impedances of power supply voltage {Za / (Za + Zb)} is applied to the device, so that the device is protected from overvoltage. Can do.

In the overvoltage protection circuit according to the fifth or sixth aspect of the present invention, for example, when the impedances of the first impedance circuit and the second impedance circuit are Za and Zb, the switch and the second switch operate at the time of overvoltage. Thus, only a voltage corresponding to the ratio of the two impedances of the power supply voltage {Za / (Za + Zb)} is applied to the device, so that the device can be protected from overvoltage, and the third switch operates to By cutting off, power consumption at the impedances Za and Zb is stopped. As a result, overheating of the impedances Za and Zb can be suppressed and the power rating can be reduced.

In the overvoltage protection circuit according to the seventh aspect of the present invention, even if the supply voltage from the AC power supply is an excessive voltage, only a voltage corresponding to the ratio of the two impedances is applied to the device. Therefore, it is not necessary to design the equipment with a high voltage rating only for protection from an excessive voltage for a short time, which is reasonable.

In the overvoltage protection circuit according to the eighth aspect of the present invention, the switch for turning on and off the alternating current needs bidirectionality, but the switch arranged on the downstream side of the DC power supply may be a one-way switch, so the cost of the switch is low. Can be achieved.

In the power conversion device according to the ninth aspect or the tenth aspect of the present invention, the overvoltage protection circuit protects the converter circuit from an excessive AC voltage applied transiently, or an excessive DC applied the inverter circuit transiently. Can be protected from voltage.

The circuit diagram of the apparatus provided with the overvoltage protection circuit which concerns on 1st Embodiment of this invention. The circuit diagram of the apparatus provided with the overvoltage protection circuit which concerns on 2nd Embodiment of this invention. The circuit diagram of a voltage detector. The circuit diagram of the apparatus provided with the overvoltage protection circuit which concerns on 3rd Embodiment of this invention. The circuit diagram of the apparatus provided with the overvoltage protection circuit which concerns on 4th Embodiment of this invention. The circuit diagram of the power converter device provided with the overvoltage protection circuit which concerns on 5th Embodiment of this invention. The circuit diagram of the power converter device provided with the overvoltage protection circuit which concerns on 6th Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following embodiments are specific examples of the present invention and do not limit the technical scope of the present invention.

<First Embodiment>
(1) Configuration of Overvoltage Protection Circuit 50 FIG. 1 is a circuit diagram of a device including an overvoltage protection circuit 50 according to the first embodiment of the present invention. In FIG. 1, the device 30 is supplied with power from a commercial power supply 90 via a pair of power supply lines 901 and 902. The overvoltage protection circuit 50 is connected between the commercial power supply 90 and the device 30.

  The overvoltage protection circuit 50 includes an overvoltage conduction circuit 10, a first impedance circuit 21, and a second impedance circuit 22.

(2) Detailed configuration of overvoltage protection circuit 50 (2-1) Overvoltage conduction circuit 10
The overvoltage conduction circuit 10 is composed of an element that allows current to flow when overvoltage occurs. As an element for passing a current at the time of overvoltage, a transient voltage suppressor, a Zener diode, a surge absorber, or an avalanche diode is employed.

  In the present embodiment, the overvoltage conduction circuit 10 is composed of one surge absorber. A surge absorber is a voltage-dependent element and has a high resistance in a normal state. However, when the applied voltage exceeds a predetermined voltage, the voltage is limited by abruptly decreasing the resistance. It can be carried out. Specific elements of the surge absorber include, but are not limited to, arresters and discharge tubes.

  The overvoltage conduction circuit 10 is connected in parallel with the device 30 between a pair of power supply lines 901 and 902. When the commercial power supply 90 is a multiphase power supply and overvoltage protection between phases is performed, the overvoltage conduction circuit 10 is connected between the power supply lines for each phase.

(2-2) First impedance circuit 21
The first impedance circuit 21 is a circuit configured such that an impedance that is a ratio of a voltage and a current in the circuit is Za.

  The first impedance circuit 21 is connected between the pair of power supply lines 901 and 902 in parallel with the device 30 and in series with the overvoltage conduction circuit 10.

(2-3) Second impedance circuit 22
The second impedance circuit 22 is a circuit configured such that an impedance that is a ratio of a voltage and a current in the circuit is Zb.

  The second impedance circuit 22 is connected between the commercial power supply 90 and the first impedance circuit 21 on the power supply line 902.

(3) Operation of Overvoltage Protection Circuit 50 For convenience of explanation, the voltage of the commercial power supply 90 is Vac, the voltage applied to the device 30 is Va, and the voltage applied to both ends of the second impedance circuit 22 is Vb.

  In FIG. 1, since the surge absorber of the overvoltage conduction circuit 10 is not conducted normally, the voltage Va = Vac−Vb is applied to the device 30.

  When the voltage Vac of the commercial power supply 90 suddenly fluctuates and becomes overvoltage, and the voltage Va exceeds the operation start voltage of the surge absorber, the surge absorber of the overvoltage conduction circuit 10 becomes conductive, and the commercial power supply 90-overvoltage conduction circuit 10-first A closed circuit of 1 impedance circuit 21 -second impedance circuit 22 -commercial power supply 90 is formed. At this time, only the voltage Va = Vac × Za / (Za + Zb) corresponding to the ratio of the two impedances of the voltage Vac is applied to the device 30. As a result, the device 30 is protected from overvoltage.

(4) Features of the first embodiment (4-1)
In the overvoltage protection circuit 50, when the surge absorber of the overvoltage conduction circuit 10 conducts at the time of overvoltage, only a voltage corresponding to the impedance ratio of the first impedance circuit 21 and the second impedance circuit 22 is applied to the device 30. 30 is protected from overvoltage.

(4-2)
Even if the supply voltage from the commercial power supply 90 is an excessive voltage, only a voltage corresponding to the ratio of the two impedances is applied to the device 30. Therefore, it is not necessary to design the device 30 with a high voltage rating only for protection from an excessive voltage for a short time, which is reasonable.

Second Embodiment
(1) Configuration of Overvoltage Protection Circuit 50 FIG. 2 is a circuit diagram of a device including an overvoltage protection circuit 50 according to the second embodiment of the present invention. In FIG. 2, the device 30 is supplied with power from a commercial power supply 90 via a pair of power supply lines 901 and 902. The overvoltage protection circuit 50 is connected between the commercial power supply 90 and the device 30.

  The overvoltage protection circuit 50 includes an overvoltage conduction circuit 10, a first impedance circuit 21, a second impedance circuit 22, and a voltage detector 33.

(2) Detailed configuration of overvoltage protection circuit 50 (2-1) Overvoltage conduction circuit 10
The overvoltage conduction circuit 10 employs a switch 11 instead of the surge absorber in the first embodiment. As shown in FIG. 2, the switch 11 is composed of a phototriac coupler, and a light emitting diode 11a is provided on the input side (between A1 and A2), and a phototriac 11b is provided on the output side (between B1 and B2). Yes. The equivalent circuit of the phototriac 11b has a configuration in which two photothyristors 111 and 112 are connected in parallel in opposite directions.

  The anode A1 of the light emitting diode 11a is connected to the power source Vc via the resistor R1. The cathode A2 of the light emitting diode 11a is connected to the control unit 40 through a signal line.

  The first anode B1 of the phototriac 11b is connected to the power supply line 901. The second anode B2 of the phototriac 11b is connected to the first impedance circuit 21.

  The light emitting diode 11a emits light when a current flows. When the phototriac 11b receives light from the light emitting diode 11a in a state where the potential of the first anode B1 is higher than the potential of the second anode B2, the photothyristor 111 is turned on. On the other hand, when light from the light emitting diode 11a is received in a state where the potential of the first anode B1 is smaller than the potential of the second anode B2, the photothyristor 112 is turned on.

  As described above, the phototriac 11b is a bidirectional element that operates with respect to a bidirectional applied voltage, and also operates at a high speed, and thus is used as a bidirectional high-speed switch.

  Note that the bidirectional high-speed switch is not limited to the phototriac, but may be a normal triac or a MOSFET connected so as to conduct in both directions. When another form of high-speed switch is used, a drive circuit corresponding to the form of the switch is appropriately used.

  The overvoltage conduction circuit 10 is connected in parallel with the device 30 between a pair of power supply lines 901 and 902. When overvoltage protection between phases is performed when the commercial power supply 90 is a multiphase power supply, the overvoltage conduction circuit 10 is connected between the power supply lines for each phase.

  Further, the control unit 40 performs operation control of the switch 11, that is, energization control to the light emitting diode 11a.

(2-2) First impedance circuit 21
The first impedance circuit 21 is a circuit configured such that an impedance that is a ratio of a voltage and a current in the circuit is Za.

  The first impedance circuit 21 is connected between the pair of power supply lines 901 and 902 in parallel with the device 30 and in series with the overvoltage conduction circuit 10.

(2-3) Second impedance circuit 22
The second impedance circuit 22 is a circuit configured such that an impedance that is a ratio of a voltage and a current in the circuit is Zb.

  The second impedance circuit 22 is connected between the commercial power supply 90 and the first impedance circuit 21 on the power supply line 902.

(2-4) Voltage detector 33
The voltage detector 33 is configured by an AC voltage detection circuit. There are various AC voltage detection circuits, and they are appropriately adopted depending on use conditions. For example, FIG. 3 is a circuit diagram of a general voltage detector 33. In FIG. 3, the voltage detector 33 includes a transformer circuit 331 and a converter circuit 332.

  The transformer circuit 331 is located on the input side and includes a primary winding 331a and a secondary winding 331b.

  The converter circuit 332 is a circuit in which a rectifying unit 332a formed of a rectifying diode and a smoothing capacitor 332b are connected in parallel.

  In the voltage detector 33, when an AC voltage is applied to the transformer circuit 331, the AC voltage is transformed by the transformer circuit 331. Then, the voltage across the secondary winding 331 b is input to the converter circuit 332.

  The transformed AC voltage input to the converter circuit 332 is converted into a DC voltage by the rectifying unit 332a and smoothed by the smoothing capacitor 332b. This smoothed DC voltage is input to the control unit 40. That is, a DC voltage corresponding to the voltage applied to the primary winding 331a is input to the control unit 40.

(3) Operation of Overvoltage Protection Circuit 50 For convenience of explanation, the voltage of the commercial power supply 90 is Vac, the voltage applied to the device 30 is Va, and the voltage applied to both ends of the second impedance circuit 22 is Vb.

  In FIG. 2, since the switch 11 of the overvoltage conduction circuit 10 is normally off, the voltage Va = Vac−Vb is applied to the device 30.

  When the voltage Vac of the commercial power supply 90 suddenly increases and the control unit 40 determines that the voltage output from the voltage detector 33 has exceeded the threshold value, the control unit 40 energizes the light emitting diode 11a of the switch 11. As a result, the phototriac 11b is turned on, and a closed circuit of commercial power supply 90-overvoltage conduction circuit 10-first impedance circuit 21-second impedance circuit 22-commercial power supply 90 is formed. At this time, only the voltage Va = Vac × Za / (Za + Zb) corresponding to the ratio of the two impedances of the voltage Vac is applied to the device 30. As a result, the device 30 is protected from overvoltage. In order to protect the device 30, the switch 11 is required to operate at high speed.

  When the control unit 40 determines that the voltage Vac of the commercial power supply 90 has dropped and the voltage output from the voltage detector 33 has fallen below the threshold for recovery, the control unit 40 turns off the light-emitting diode 11a of the switch 11 To do. As a result, the photo triac 11b is turned off and returns to normal operation.

(4) Features of the second embodiment (4-1)
In the overvoltage protection circuit 50, since the switch 11 of the overvoltage conduction circuit 10 is turned on at the time of overvoltage, only a voltage corresponding to the impedance ratio of the first impedance circuit 21 and the second impedance circuit 22 is applied to the device 30. 30 is protected from overvoltage.

(4-2)
Even if the supply voltage from the commercial power supply 90 is an excessive voltage, only a voltage corresponding to the ratio of the two impedances is applied to the device 30. Therefore, it is not necessary to design the device 30 with a high voltage rating only for protection from an excessive voltage for a short time, which is reasonable.

<Third Embodiment>
(1) Configuration of Overvoltage Protection Circuit 50 FIG. 4 is a circuit diagram of a device including an overvoltage protection circuit 50 according to the third embodiment of the present invention. In FIG. 4, the device 30 is supplied with power from a commercial power supply 90 via a pair of power supply lines 901 and 902. The overvoltage protection circuit 50 is connected between the commercial power supply 90 and the device 30.

  The overvoltage protection circuit 50 includes an overvoltage conduction circuit 10, a first impedance circuit 21, a second impedance circuit 22, a voltage detector 33, and a bypass circuit 35.

(2) Detailed Configuration of Overvoltage Protection Circuit 50 In the third embodiment, a bypass circuit 35 is added to the second embodiment, and an overvoltage conduction circuit 10, a first impedance circuit 21, a second impedance circuit 22, and The same voltage detector 33 is employed. Therefore, only the bypass circuit 35 will be described here.

(2-1) Bypass circuit 35
The bypass circuit 35 is a circuit that is connected in parallel to the second impedance circuit 22 and bypasses the second impedance circuit 22. The bypass circuit 35 includes the second switch 12. The second switch 12 opens and closes the bypass circuit 35. Here, opening and closing the bypass circuit 35 means making the bypass circuit 35 conductive or non-conductive to make it non-conductive.

(2-2) Second switch 12
The second switch 12 normally closes the bypass circuit 35, that is, keeps it in a conductive state. This is because if the bypass circuit 35 is left open (non-conducting state) during normal operation, the second impedance circuit 22 is always connected and power is always consumed, and the voltage applied to the device 30 is second. This is because the voltage is lowered by the voltage drop of the impedance Zb of the impedance circuit 22.

  On the other hand, in order to protect the device 30 during overvoltage, the bypass circuit 35 is quickly opened and the second impedance circuit 22 is connected, and the commercial power supply 90—overvoltage conduction circuit 10—first impedance circuit 21—second impedance circuit 22— It is necessary to configure a closed circuit called a commercial power supply 90. For this reason, the second switch 12 is required to operate at high speed.

  As the second switch 12, a triac, a MOSFET connected so as to conduct in both directions, or the like is employed. In the present embodiment, a phototriac coupler is employed as with the switch 11.

  As shown in FIG. 4, the second switch 12 is provided with a light emitting diode 12a on the input side (between C1 and C2) and a phototriac 12b on the output side (between D1 and D2). The equivalent circuit of the phototriac 12b has a configuration in which two photothyristors 121 and 122 are connected in parallel in opposite directions.

  The anode C1 of the light emitting diode 12a is connected to the power source Vc via the resistor R2. The cathode C2 of the light emitting diode 12a is connected to the control unit 40 via a signal line.

  The first anode D1 of the phototriac 12b is connected between the second impedance circuit 22 in the power supply line 902 and the device 30. The second anode D2 of the photo triac 12b is connected to the power line 902 between the second impedance circuit 22 and the commercial power source 90.

  The operating principle of the photothyristors 121 and 122 of the light-emitting diode 12a and the phototriac 12b is the same as the operating principle of the light-emitting diode 11a and the photothyristor 111 and 112 of the phototriac 11b in the switch 11, so that the description of the operation is omitted here. .

(3) Operation of Overvoltage Protection Circuit 50 In FIG. 4, the switch 11 of the overvoltage conduction circuit 10 is normally turned off and the bypass circuit 35 is in the conduction state with the second switch 12 closed, so that the voltage Va is applied to the device 30. = Vac is applied.

  When the voltage Vac of the commercial power supply 90 suddenly increases and the control unit 40 determines that the voltage output from the voltage detector 33 has exceeded the threshold, the control unit 40 energizes the light emitting diode 11a of the switch 11 to generate a photo The triac 11b is turned on. At the same time, the control unit 40 stops energization of the light emitting diode 12a of the second switch 12 and turns off the phototriac 12b.

  As a result, a closed circuit of commercial power supply 90-overvoltage conduction circuit 10-first impedance circuit 21-second impedance circuit 22-commercial power supply 90 is formed. At this time, only the voltage Va = Vac × Za / (Za + Zb) corresponding to the ratio of the two impedances of the voltage Vac is applied to the device 30. As a result, the device 30 is protected from overvoltage.

  When the control unit 40 determines that the voltage Vac of the commercial power supply 90 has dropped and the voltage output from the voltage detector 33 has fallen below the threshold for recovery, the control unit 40 turns off the light-emitting diode 11a of the switch 11 Then, the photo triac 11b is turned off. At the same time, the control unit 40 energizes the light emitting diode 12a of the second switch 12 to turn on the phototriac 12b. As a result, the normal operation is restored.

(4) Features of the third embodiment (4-1)
In the overvoltage protection circuit 50, since the second switch 12 is normally turned on and the bypass circuit 35 is closed, power is not consumed by the second impedance circuit 22, and the voltage applied to the device 30 is the second voltage. It can also be avoided that the voltage drop in the impedance circuit 22 is lowered.

(4-2)
In addition, when overvoltage occurs, the switch 11 of the overvoltage conduction circuit 10 is turned on and the second switch 12 is turned off, so that the device 30 has only a voltage corresponding to the impedance ratio of the first impedance circuit 21 and the second impedance circuit 22. Since it is not applied, the device 30 is protected from overvoltage.

(4-3)
Even if the supply voltage from the commercial power supply 90 is an excessive voltage, only a voltage corresponding to the ratio of the two impedances is applied to the device 30. Therefore, it is not necessary to design the device 30 with a high voltage rating only for protection from an excessive voltage for a short time, which is reasonable.

<Fourth embodiment>
(1) Configuration of Overvoltage Protection Circuit 50 FIG. 5 is a circuit diagram of an apparatus including an overvoltage protection circuit 50 according to the fourth embodiment of the present invention. In FIG. 5, the device 30 is supplied with power from a commercial power supply 90 via a pair of power supply lines 901 and 902. The overvoltage protection circuit 50 is connected between the commercial power supply 90 and the device 30.

  The overvoltage protection circuit 50 includes an overvoltage conduction circuit 10, a first impedance circuit 21, a second impedance circuit 22, a voltage detector 33, a bypass circuit 35, and a third switch 13.

(2) Detailed Configuration of Overvoltage Protection Circuit 50 In the fourth embodiment, a third switch 13 is added to the third embodiment, and an overvoltage conduction circuit 10, a first impedance circuit 21, a second impedance circuit 22, The same voltage detector 33 and bypass circuit 35 are employed. Therefore, only the third switch 13 will be described here.

(2-1) Third switch 13
The third switch 13 opens and closes the power line 901. Here, opening and closing the power supply line 901 means that the power supply line 901 is turned on or off to make it non-conductive.

  The third switch 13 normally closes the power supply line 901, that is, keeps it conductive. On the other hand, at the time of overvoltage, the switch 11 is turned on, the second switch 12 is turned off, and a closed circuit of the commercial power supply 90-overvoltage conduction circuit 10-first impedance circuit 21-second impedance circuit 22-commercial power supply 90 is formed. After the protection operation of the device 30 is performed, the third switch 13 is turned off and the power line 901 is shut off.

  The purpose of cutting off the power supply line 901 is to stop power consumption in the first impedance circuit 21 and the second impedance circuit 22, and it is possible to suppress overheating of the first impedance circuit 21 and the second impedance circuit 22. The power rating can be reduced, and the cost can be reduced.

  Since the third switch 13 is not required to have high speed like the switch 11 and the second switch 12, a relay circuit is employed in this embodiment.

  As shown in FIG. 5, the third switch 13 includes a relay contact 13a for opening and closing the power supply line 901, a relay coil 13b for operating the relay contact 13a, and a transistor 13c for energizing and de-energizing the relay coil 13b. Is included. One end of the relay coil 13b is connected to the positive electrode of the power source Vb, and the other end is connected to the collector side of the transistor 13c. The controller 40 switches between the presence and absence of the base current of the transistor 13c, turns on and off the collector and the emitter, and energizes and de-energizes the relay coil 13b.

(3) Operation of Overvoltage Protection Circuit 50 In FIG. 5, normally, the switch 11 of the overvoltage conduction circuit 10 is turned off, the bypass circuit 35 is in the conduction state with the second switch 12 closed, and the third switch 13 is a power source. Since the line 901 is in a conducting state, the voltage Va = Vac is applied to the device 30.

  When the voltage Vac of the commercial power supply 90 suddenly increases and the control unit 40 determines that the voltage output from the voltage detector 33 has exceeded the threshold, the control unit 40 energizes the light emitting diode 11a of the switch 11 to generate a photo The triac 11b is turned on. At the same time, the control unit 40 stops energization of the light emitting diode 12a of the second switch 12 and turns off the phototriac 12b.

  As a result, a closed circuit of commercial power supply 90-overvoltage conduction circuit 10-first impedance circuit 21-second impedance circuit 22-commercial power supply 90 is formed. At this time, only the voltage Va = Vac × Za / (Za + Zb) corresponding to the ratio of the two impedances of the voltage Vac is applied to the device 30. As a result, the device 30 is protected from overvoltage.

  Thereafter, when the overvoltage state continues, the third switch 13 cuts off the power supply line 901 and stops power consumption in the first impedance circuit 21 and the second impedance circuit 22.

  When the control unit 40 determines that the voltage Vac of the commercial power supply 90 has dropped and the voltage output from the voltage detector 33 has fallen below the threshold for recovery, the control unit 40 turns off the light-emitting diode 11a of the switch 11 Then, the photo triac 11b is turned off. At the same time, the control unit 40 energizes the light emitting diode 12a of the second switch 12 to turn on the phototriac 12b. Further, the third switch 13 is turned on and the power supply line 901 is connected to return to the normal operation.

(4) Features of the fourth embodiment (4-1)
In the overvoltage protection circuit 50, since the second switch 12 is normally turned on and the bypass circuit 35 is closed, power is not consumed by the second impedance circuit 22, and the voltage applied to the device 30 is the second voltage. It can also be avoided that the voltage drop in the impedance circuit 22 is lowered.

(4-2)
In addition, when overvoltage occurs, the switch 11 of the overvoltage conduction circuit 10 is turned on and the second switch 12 is turned off, so that the device 30 has only a voltage corresponding to the impedance ratio of the first impedance circuit 21 and the second impedance circuit 22. Since it is not applied, the device 30 is protected from overvoltage.

(4-3)
Further, the third switch 13 cuts off the power supply line 901 to stop power consumption in the first impedance circuit 21 and the second impedance circuit 22. As a result, overheating of the first impedance circuit 21 and the second impedance circuit 22 can be suppressed, and the power rating can be reduced.

(4-4)
Even if the supply voltage from the commercial power supply 90 is an excessive voltage, only a voltage corresponding to the ratio of the two impedances is applied to the device 30. Therefore, it is not necessary to design the device 30 with a high voltage rating only for protection from an excessive voltage for a short time, which is reasonable.

<Fifth Embodiment>
(1) Configuration of Power Converter 200 FIG. 6 is a circuit diagram of a power converter 200 including an overvoltage protection circuit 100 according to the fifth embodiment of the present invention. In FIG. 6, the power conversion device 200 includes a DC power supply unit 80, an inverter 95, and an overvoltage protection circuit 100.

  The inverter 95 is supplied with power from the DC power supply unit 80 via a pair of power supply lines 801 and 802. The overvoltage protection circuit 100 is connected between the DC power supply unit 80 and the inverter 95.

(1-1) DC power supply unit 80
The DC power supply unit 80 includes a rectifying unit 81 and a smoothing capacitor 82 connected in parallel with the rectifying unit 81.

  The rectifying unit 81 is configured in a bridge shape by four diodes D1a, D1b, D2a, and D2b. Specifically, the diodes D1a and D1b and D2a and D2b are respectively connected in series. The cathode terminals of the diodes D1a and D2a are both connected to the plus side terminal of the smoothing capacitor 82 and function as the positive side output terminal of the rectifying unit 81. The anode terminals of the diodes D1b and D2b are both connected to the minus terminal of the smoothing capacitor 82 and function as the negative output terminal of the rectifier 81.

  A connection point between the diode D1a and the diode D1b is connected to one pole of the commercial power supply 90. A connection point between the diode D2a and the diode D2b is connected to the other pole of the commercial power supply 90. The rectifying unit 81 rectifies the AC voltage output from the commercial power supply 90 to generate a DC voltage, and supplies this to the smoothing capacitor 82.

  The smoothing capacitor 82 smoothes the voltage rectified by the rectifying unit 81. The smoothed voltage Vdc is applied to the inverter 95 connected to the output side of the smoothing capacitor 82.

  In addition, as a kind of capacitor | condenser, although an electrolytic capacitor, a film capacitor, a tantalum capacitor etc. are mentioned, in this embodiment, an electrolytic capacitor is employ | adopted as the smoothing capacitor 82. FIG.

  The DC power supply unit 80 can be rephrased as a converter circuit that converts an AC voltage into a DC voltage.

(1-2) Inverter 95
The inverter 95 includes a plurality of IGBTs (insulated gate bipolar transistors, hereinafter simply referred to as transistors) and a plurality of free-wheeling diodes. The inverter 95 is applied with the voltage Vdc from the smoothing capacitor 82, and each transistor is turned on and off at the timing instructed by the gate drive circuit 96, thereby generating a drive voltage for driving the motor 150. The motor 150 is, for example, a compressor motor or a fan motor of a heat pump type air conditioner.

  In addition, although the inverter 95 of this embodiment is a voltage source inverter, it is not limited to it, A current source inverter may be sufficient.

(1-3) Gate drive circuit 96
The gate drive circuit 96 changes the on / off state of each transistor of the inverter 95 based on a command from the control unit 40.

(1-4) Overvoltage protection circuit 100
The overvoltage protection circuit 100 includes an overvoltage conduction circuit 60, a first impedance circuit 71, a second impedance circuit 72, a voltage detector 83, a bypass circuit 85, and a third switch 63.

(2) Detailed Configuration of Overvoltage Protection Circuit 100 The fifth embodiment is different from the first to fourth embodiments already described in that the overvoltage protection circuit 100 is provided in the DC section. Therefore, in view of the fact that each component is also replaced from the AC specification to the DC specification, the description will be given again by changing the code even if the names are the same.

(2-1) Overvoltage conduction circuit 60
The overvoltage conduction circuit 60 employs a switch 61 instead of the switch 11 in the fourth embodiment.

  As shown in FIG. 6, the switch 61 includes a photocoupler 61a, a drive circuit 61b, and a transistor 61c. The photocoupler 61a includes a light emitting diode 611 and a phototransistor 612.

  The light emitting diode 611 of the photocoupler 61a is connected to the input side (between E1 and E2) of the switch 61. The anode E1 of the light emitting diode 611 is connected to the power source Vc via the resistor R1. The cathode E2 of the light emitting diode 611 is connected to the control unit 40 via a signal line. The phototransistor 612 is connected between the drive circuit 61b and GND.

  A transistor 61c is provided on the output side of the switch 61 (between F1 and F2). The collector F1 of the transistor 61c is connected to the power supply line 801. The emitter F2 of the transistor 61c is connected to the first impedance circuit 71.

  The control signal of the control unit 40 is input to the drive circuit 61b through the photocoupler 61a. A driving power supply (not shown) is connected to the driving circuit 61b. When the control unit 40 turns on the signal line of the light emitting diode 611, the light emitting diode 611 emits light and the phototransistor 612 becomes conductive. While the phototransistor 612 is conducting, a driving signal is output from the driving circuit 61b to the base of the transistor 61c, and the collector F1-emitter F2 of the transistor 61c is conducted.

  Conversely, when the control unit 40 turns off the signal line of the light emitting diode 611, the light emitting diode 611 does not emit light, and the phototransistor 612 does not conduct. While the phototransistor 612 is not conducting, the collector F1 and the emitter F2 of the transistor 61c are not conducting.

  As described above, when the DC circuit is opened and closed, a one-way switch may be used. Therefore, bidirectionality when the AC circuit is opened and closed is not required, and there is a cost merit. The configuration of the one-way switch is not limited to this embodiment, but it is desirable that the switch operation can be performed at high speed like a semiconductor switch.

  The overvoltage conduction circuit 60 is connected in parallel with the device 30 between the pair of power supply lines 801 and 802.

(2-2) First impedance circuit 71
The first impedance circuit 71 is a circuit configured such that an impedance that is a ratio of a voltage and a current in the circuit is Za. In general, a resistance element is employed.

  The first impedance circuit 71 is connected between the pair of power supply lines 801 and 802 in parallel with the inverter 95 and in series with the overvoltage conduction circuit 60.

(2-3) Second impedance circuit 72
The second impedance circuit 72 is a circuit configured such that an impedance that is a ratio of a voltage and a current in the circuit is Zb. In general, a resistance element is employed.

  The second impedance circuit 72 is connected between the DC power supply unit 80 and the first impedance circuit 71 on the power supply line 802.

(2-4) Voltage detector 83
The voltage detector 83 is connected to the output side of the smoothing capacitor 82, and detects the voltage across the smoothing capacitor 82, that is, the value of the smoothed voltage Vdc. For example, the voltage detector 83 is configured such that two resistors connected in series with each other are connected in parallel to the smoothing capacitor 82 and the voltage Vdc is divided. The voltage value at the connection point between the two resistors is input to the control unit 40.

(2-5) Bypass circuit 85
The bypass circuit 85 is a circuit that is connected in parallel to the second impedance circuit 72 and bypasses the second impedance circuit 72. The bypass circuit 85 has a second switch 62. The second switch 62 opens and closes the bypass circuit 85. Here, opening and closing the bypass circuit 85 means that the bypass circuit 35 is turned on or off to make it non-conductive.

(2-6) Second switch 62
The second switch 62 normally closes the bypass circuit 85, that is, keeps it in a conductive state. This is because if the bypass circuit 85 is left open (non-conducting state) during normal operation, power is always consumed by the second impedance circuit 72, and the voltage applied to the inverter 95 is the voltage of the impedance Zb of the second impedance circuit 72. This is because it is lowered by the amount of descent.

  On the other hand, in order to protect the inverter 95 at the time of overvoltage, the bypass circuit 85 is quickly opened, and a closed circuit of DC power supply unit 80-overvoltage conduction circuit 60-first impedance circuit 71-second impedance circuit 72-DC power supply unit 80. Need to be configured. For this reason, the second switch 62 is required to operate at high speed. In the present embodiment, the same switch as the switch 61 is employed. The switch is not limited to this embodiment.

  As shown in FIG. 6, in the second switch 62, a light emitting diode 621 of a photocoupler 62a is provided on the input side (between G1 and G2), and a transistor 62c is provided on the output side (between H1 and H2). The anode G1 of the light emitting diode 621 is connected to the power source Vc via the resistor R2. The cathode G2 of the light emitting diode 621 is connected to the control unit 40 via a signal line.

  The collector H1 of the transistor 62c is connected between the second impedance circuit 72 in the power supply line 802 and the inverter 95. The emitter H2 of the transistor 62c is connected to the power supply line 802 between the second impedance circuit 72 and the DC power supply unit 80.

  Since the operation principle of the second switch 62 is the same as that of the switch 61, the description of the operation is omitted here.

(2-7) Third switch 63
The third switch 63 opens and closes the power line 801. Here, opening and closing the power supply line 801 is to turn the power supply line 801 on or off to make it non-conductive.

  The third switch 63 normally closes the power supply line 801, that is, keeps it conductive. On the other hand, at the time of overvoltage, the switch 61 is turned on, the second switch 62 is turned off, and a closed circuit of DC power supply unit 80-overvoltage conduction circuit 60-first impedance circuit 71-second impedance circuit 72-DC power supply unit 80 is formed. After the configuration and the protective operation of the inverter 95 is performed, the third switch 63 is turned off and the power line 801 is shut off.

  The purpose of cutting off the power supply line 801 is to stop power consumption in the first impedance circuit 71 and the second impedance circuit 72, and it is possible to suppress overheating of the first impedance circuit 71 and the second impedance circuit 72. The power rating can be reduced, and the cost can be reduced.

  Since the third switch 63 does not require high speed like the switch 61 and the second switch 62, a relay circuit is employed in the present embodiment.

  As shown in FIG. 6, the third switch 63 includes a relay contact 63a for opening and closing the power supply line 801, a relay coil 63b for operating the relay contact 63a, and a transistor 63c for energizing and de-energizing the relay coil 63b. Is included. One end of the relay coil 63b is connected to the positive electrode of the power source Vb, and the other end is connected to the collector side of the transistor 63c. The controller 40 switches between the presence and absence of the base current of the transistor 63c, turns on and off the collector and the emitter, and performs energization and de-energization of the relay coil 63b.

(3) Operation of Overvoltage Protection Circuit 50 In FIG. 6, normally, the switch 61 of the overvoltage conduction circuit 60 is turned off, the bypass circuit 85 is in the conduction state with the second switch 62 closed, and the third switch 63 is a power source. Since the line 801 is in a conductive state, the voltage Va = Vdc is applied to the inverter 95.

  When the voltage Vdc of the DC power supply unit 80 increases rapidly and the control unit 40 determines that the voltage output from the voltage detector 83 exceeds the threshold value, the control unit 40 energizes the light emitting diode 611 of the switch 61, The transistor 61c is turned on. At the same time, the control unit 40 stops energization of the light emitting diode 621 of the second switch 62 and turns off the transistor 62c.

  As a result, a closed circuit of the DC power supply unit 80-overvoltage conduction circuit 60-first impedance circuit 71-second impedance circuit 72-DC power supply unit 80 is formed. At this time, only the voltage Va = Vdc × Za / (Za + Zb) corresponding to the ratio of the two impedances of the voltage Vdc is applied to the inverter 95. As a result, the inverter 95 is protected from overvoltage.

  Thereafter, when the overvoltage state continues, the third switch 63 cuts off the power supply line 801 and stops the power consumption in the first impedance circuit 71 and the second impedance circuit 72.

  When the control unit 40 determines that the voltage Vac of the commercial power supply 90 and the voltage Vdc of the DC power supply unit 80 are decreased and the voltage output from the voltage detector 83 is lower than the threshold for recovery, the control unit 40 switches the switch 61. The light-emitting diode 611 is turned off, and the transistor 61c is turned off. At the same time, the control unit 40 energizes the light emitting diode 621 of the second switch 62 to turn on the transistor 62c. Further, by turning on the third switch 63 and connecting the power supply line 801, the normal operation is restored.

(4) Features of the fifth embodiment (4-1)
In the overvoltage protection circuit 100, since the second switch 62 is normally turned on and the bypass circuit 85 is closed, power is not consumed by the second impedance circuit 72, and the voltage applied to the inverter 95 is the second voltage. It can also be avoided that the voltage drops by the voltage drop in the impedance circuit 72.

(4-2)
In addition, when overvoltage occurs, the switch 61 of the overvoltage conduction circuit 60 is turned on and the second switch 62 is turned off, so that the inverter 95 has only a voltage corresponding to the impedance ratio of the first impedance circuit 71 and the second impedance circuit 72. Since it is not applied, the inverter 95 is protected from overvoltage.

(4-3)
Further, the third switch 63 cuts off the power supply line 801 to stop power consumption in the first impedance circuit 71 and the second impedance circuit 72. As a result, overheating of the first impedance circuit 71 and the second impedance circuit 72 can be suppressed, and the power rating can be reduced.

(4-4)
Furthermore, since the switch 61 and the second switch 62 disposed on the downstream side of the DC power supply unit 80 may be unidirectional switches, the cost of the switches can be reduced.

<Sixth Embodiment>
(1) Configuration of Overvoltage Protection Circuit 100 FIG. 7 is a circuit diagram of a power conversion device 200 including the overvoltage protection circuit 100 according to the sixth embodiment of the present invention. In FIG. 7, the inverter 95 is supplied with power from a DC power supply unit 80 via a pair of power supply lines 801 and 802. A part of the overvoltage protection circuit 100 is connected between the commercial power supply 90 and the DC power supply unit 80, and the other part is connected between the DC power supply unit 80 and the inverter 95.

  The overvoltage protection circuit 100 includes an overvoltage conduction circuit 60, a first impedance circuit 71, a second impedance circuit 72, a voltage detector 33, a bypass circuit 85, and a third switch 13.

  The difference between the sixth embodiment and the fifth embodiment already described is that a voltage detector and a third switch, which are components of the overvoltage protection circuit 100, are provided between the commercial power supply 90 and the DC power supply unit 80. It is that. That is, the arrangement of the voltage detector and the third switch is the same as the arrangement of the voltage detector 33 and the third switch 13 in the fourth embodiment. Therefore, in view of the fact that the voltage detector and the third switch are replaced from the DC specification to the AC specification, the voltage detector 33 and the third switch 13 of the fourth embodiment are employed.

  Therefore, the content of each component includes the voltage detector 33 and the third switch 13 of the fourth embodiment, the overvoltage conduction circuit 60 of the fifth embodiment, the first impedance circuit 71, the second impedance circuit 72, and the bypass circuit 85. Therefore, the description is omitted here and only the operation is described.

(2) Operation of Overvoltage Protection Circuit 50 In FIG. 7, normally, the switch 61 of the overvoltage conduction circuit 60 is turned off, the bypass circuit 85 is in the conduction state with the second switch 62 closed, and the third switch 63 is a power source. Since the line 901 is in a conducting state, the voltage Va = Vdc is applied to the inverter 95.

  When the control unit 40 determines that the voltage output from the voltage detector 33 has exceeded the threshold value due to the fluctuation of the voltage Vac of the commercial power supply 90, the control unit 40 energizes the light emitting diode 611 of the switch 61. Then, the transistor 61c is turned on. At the same time, the control unit 40 stops energization of the light emitting diode 621 of the second switch 62 and turns off the transistor 62c.

  As a result, a closed circuit of the DC power supply unit 80-overvoltage conduction circuit 60-first impedance circuit 71-second impedance circuit 72-DC power supply unit 80 is formed. At this time, only the voltage Va = Vdc × Za / (Za + Zb) corresponding to the ratio of the two impedances of the voltage Vdc is applied to the inverter 95. As a result, the inverter 95 is protected from overvoltage.

  Thereafter, the third switch 13 cuts off the power supply line 901 and stops power consumption in the first impedance circuit 71 and the second impedance circuit 72.

(3) Features of the sixth embodiment (3-1)
In the overvoltage protection circuit 100, since the second switch 62 is normally turned on and the bypass circuit 85 is closed, power is not consumed by the second impedance circuit 72, and the voltage applied to the inverter 95 is the second voltage. It can also be avoided that the voltage drops by the voltage drop in the impedance circuit 72.

(3-2)
In addition, when overvoltage occurs, the switch 61 of the overvoltage conduction circuit 60 is turned on and the second switch 62 is turned off, so that the inverter 95 has only a voltage corresponding to the impedance ratio of the first impedance circuit 71 and the second impedance circuit 72. Since it is not applied, the inverter 95 is protected from overvoltage.

(3-3)
Further, the third switch 13 cuts off the power supply line 901 to stop the power consumption in the first impedance circuit 71 and the second impedance circuit 72. As a result, overheating of the first impedance circuit 71 and the second impedance circuit 72 can be suppressed, and the power rating can be reduced.

(3-4)
Furthermore, since the switch 61 and the second switch 62 disposed on the downstream side of the DC power supply unit 80 may be unidirectional switches, the cost of the switches can be reduced.

<Other embodiments>
(A)
The embodiment in which the bypass circuit 35 in the third embodiment shown in FIG. 4 is connected in parallel to the second impedance circuit 22 in the first embodiment shown in FIG. 1 is also effective.

  Normally, the second switch 12 is turned on and the bypass circuit 35 is closed, so that no power is consumed in the second impedance circuit 22, and the voltage applied to the device 30 is equal to the voltage drop in the second impedance circuit 22. Only lowering can be avoided.

(B)
An embodiment in which the power supply line 901 in the first embodiment shown in FIG. 1 and the second embodiment shown in FIG. 2 is opened and closed by the third switch 13 in the fourth embodiment shown in FIG. 5 is also effective.

  Since the third switch 13 stops the power consumption in the first impedance circuit 21 and the second impedance circuit 22 by cutting off the power supply line 901, the power rating of the first impedance circuit 21 and the second impedance circuit 22 is reduced. Can do.

(C)
The overvoltage protection circuit 50 according to the first embodiment shown in FIG. 1, the second embodiment shown in FIG. 2, and the third embodiment shown in FIG. 4 is an overvoltage protection circuit for an AC voltage. When the power source is a DC power source or when a DC power source unit that rectifies an AC power source is provided in the device, each component may be replaced with the DC specification and provided downstream of the DC power source unit.

(D)
The sixth embodiment is different from the fifth embodiment in that the voltage detector and the third switch are provided between the commercial power supply 90 and the DC power supply unit 80, but only the voltage detector is commercialized. You may make it provide between the power supply 90 and the DC power supply part 80. FIG.

(E)
In the fifth embodiment and the sixth embodiment, the example in which the overvoltage protection circuit is provided inside the device has been described, but the device is not limited to the one having the converter circuit and the inverter circuit.

(F)
In the third embodiment, the third switch is turned off after the protection operation of the device 30 is performed. However, the third switch may be turned off after a predetermined time has elapsed since the protection operation was performed.

(G)
In the third embodiment, the third switch is turned off after the protection operation of the device 30 is performed. However, the device further includes a device voltage detector that detects the device voltage V, and the device voltage exceeds a predetermined value. Sometimes the third switch may be turned off.

(H)
In the first embodiment, a surge absorber has been described as an example of an element that allows a current to flow during overvoltage. In this case, as described in the first embodiment, since the voltage is not held by the element itself when conducting, the power supply voltage is divided by the impedance ratio and applied to the device 30. However, when an overvoltage circuit is applied to an overvoltage circuit, such as a varistor or Zener diode that maintains a predetermined voltage when the element itself is on, the voltage obtained by removing the retained voltage from the power supply voltage. Is divided by the impedance ratio. In this case, since only the voltage obtained by adding the holding voltage of the element and the voltage divided by the impedance is applied to the device, the applied voltage to the device is limited, and the device can be protected from overvoltage.

  INDUSTRIAL APPLICABILITY The present invention is useful for equipment used in an area where power supply voltage is likely to fluctuate, such as a refrigeration apparatus.

10, 60 Overvoltage conduction circuit 11, 61 Switch 12, 62 Second switch 13, 63 Third switch 21, 71 First impedance circuit 22, 72 Second impedance circuit 33, 83 Voltage detector 35, 85 Bypass circuit 50, 100 Overvoltage protection circuit 80 DC power supply (DC power supply, converter circuit)
90 Commercial power (AC power)
95 Inverter (Inverter circuit)

JP 2009-207329 A

Claims (10)

An overvoltage protection circuit connected between a power source and a device supplied with power from the power source,
An overvoltage conduction circuit (10, 60) that is connected in parallel with the device between a pair of power supply lines connecting the power source and the device, and causes a current to flow in the event of an overvoltage,
A first impedance circuit (21, 71) connected in parallel with the device between a pair of power supply lines and in series with the overvoltage conduction circuit (10, 60);
A second impedance circuit (22, 72) connected between the power supply of the power supply line and the first impedance circuit (21, 71);
Comprising
Overvoltage protection circuit (50, 100). The overvoltage conduction circuit (10, 60) includes any one of a transient voltage suppressor, a Zener diode, a surge absorber, and an avalanche diode as an element that allows a current to flow when overvoltage occurs.
The overvoltage protection circuit (50, 100) according to claim 1. A voltage detector (33, 83) for detecting the voltage of the power source;
The overvoltage conduction circuit (10, 60) has a switch (11, 61) for opening and closing between the power supply line and the first impedance circuit (21, 71),
The switch (11, 61) is turned on when a value detected by the voltage detector (33, 83) exceeds a predetermined threshold, and between the power supply line and the first impedance circuit (21, 71). Continuity,
The overvoltage protection circuit (50, 100) according to claim 1. A voltage detector (33, 83) for detecting the voltage of the power source;
A bypass circuit (35, 85) bypassing the second impedance circuit (22, 72);
Further comprising
The bypass circuit (35, 85) has a second switch (12, 62) for opening and closing the bypass circuit (35, 85),
The second switch (12, 62) normally closes the bypass circuit (35, 85), and when the detected value by the voltage detector (33, 83) exceeds a predetermined threshold, 35, 85),
The overvoltage protection circuit (50, 100) according to claim 1 or 2. A bypass circuit (35, 85) for bypassing the second impedance circuit (22, 72);
The bypass circuit (35, 85) has a second switch (12, 62) for opening and closing the bypass circuit (35, 85),
The second switch (12, 62) normally closes the bypass circuit (35, 85), and when the detected value by the voltage detector (33, 83) exceeds a predetermined threshold, 35, 85),
The overvoltage protection circuit (50, 100) according to claim 3. A voltage detector (33, 83) for detecting the voltage of the power source;
A third switch (13, 63) for opening and closing the power line;
Further comprising
The third switch (13, 63) normally turns on the power supply line, and when the detection value by the voltage detector (33, 83) exceeds a predetermined threshold, the overvoltage conduction circuit (10, 60) shuts off the power line after continuity;
The overvoltage protection circuit (50, 100) according to claim 1 or 2. A third switch (13, 63) for opening and closing the power line;
The third switch (13, 63) normally turns on the power supply line, and when the detection value by the voltage detector (33, 83) exceeds a predetermined threshold, the overvoltage conduction circuit (10, 60) shuts off the power line after continuity;
The overvoltage protection circuit (50, 100) according to any one of claims 3 to 5. The power source is an AC power source;
The overvoltage protection circuit (50) according to any one of claims 1 to 7. The power source is a DC power source;
The overvoltage protection circuit (100) according to any one of claims 1 to 7. A converter circuit (80) connected to an AC power source and converting AC voltage to DC voltage;
An inverter circuit (95) for converting the DC voltage into an AC voltage;
Overvoltage protection circuit (100) according to any one of claims 1 to 9,
Comprising
Power conversion device.

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