JP2007228714A - Power converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a power converter that can instantaneously detect an overcurrent at a current detection line even if a process for adjusting the output characteristic of a current detector by using a circuit element such as a resistor element is not necessary, can perform the high-responsiveness off-operation of a semiconductor switch element, and can protect the semiconductor switch element from the overcurrent. <P>SOLUTION: The power converter comprises: a control signal generation part that outputs either an upper-limit threshold voltage or a lower-limit threshold voltage that correspond to the current detection sensitivity of the current detector and an offset voltage; and a gate blocking circuit that off-operates the semiconductor switch element when a detected voltage is higher than the upper-limit threshold voltage, or when the detected voltage is lower than the lower-limit threshold voltage. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a power conversion device that performs overcurrent protection based on a current value detected by a current detector.

  In the conventional power converter, in order to freely control the output voltage and the output frequency, a converter unit that converts an AC voltage into a DC voltage, a smoothing capacitor that smoothes the DC voltage converted by the converter unit, and a converter unit And an inverter unit that reconverts the DC voltage smoothed in step 1 into an AC voltage. Also, a current detector for detecting the output current value of the inverter unit is provided, and the inverter unit is protected when the current value detected by the current detector exceeds a predetermined overcurrent protection level (threshold voltage). Have a function of turning off (shut off) the semiconductor switch elements constituting the inverter unit (see, for example, Patent Document 1).

  The current detector surrounds the current detection line, and includes a magnetic core having an air gap, a Hall element disposed in the air gap portion of the magnetic core, and a detection circuit that amplifies the output voltage from the Hall element. It is configured. A current detector using a Hall element has a predetermined value due to variations in the size of the magnetic core, variations in the characteristics of the Hall element, variations in resistance elements constituting the detection circuit, and variations in characteristics of circuit components such as operational amplifiers. Current detection sensitivity (sensitivity of detection voltage to current) and offset voltage cannot be obtained.

  For this reason, a function trimming resistor or semi-fixed resistor is used so that the current detection sensitivity and offset voltage are within the specified range while a specific current is applied to the current detection line and the output voltage is monitored by operating the detection circuit. The output characteristic of the current detector is adjusted by adjusting the resistance value of the resistance element that constitutes the detection circuit, using a parallel connection body of the correction resistor and the correction resistor (for example, see Patent Document 2). In addition, the current value detected by the current detector is taken into the microcomputer so that the process of adjusting the output characteristics of the current detector is not required, and the microcomputer compares the current value with the threshold voltage, and the inverter unit And the semiconductor switch element is turned off (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 6-133592 (pages 2, 4 and 1, 2) JP 2004-20560 A (page 2-3, FIGS. 1 and 9)

  In conventional power converters, it is necessary to adjust the current detector output characteristics of the current detector by adjusting the current detection sensitivity and offset voltage of the Hall element by adjusting the resistance value of the resistor elements that make up the detection circuit for each power converter. Met. In order to eliminate the step of adjusting the output characteristics of the current detector, the current value detected by the current detector is taken into the microcomputer, and when the microcomputer determines whether the current value exceeds the threshold voltage, Since the processing time in the microcomputer is required, there is a problem that the overcurrent detection in the current detection line cannot be performed instantaneously and the semiconductor switch element having a quick response cannot be turned off.

  The present invention has been made to solve the above-described problems. Even when a step of adjusting the output characteristics of the current detector by a circuit element such as a resistance element is unnecessary, an overcurrent in the current detection line is reduced. A power conversion device that instantly detects and performs a turn-off operation of a semiconductor switch element having a quick response to protect the semiconductor switch element against an overcurrent is obtained. In addition, since the process of adjusting the output characteristics of the current detector is not necessary, the manufacturing process can be simplified.

  A power conversion device according to the present invention includes a semiconductor switch element connected to a voltage terminal, a current detector that detects a current flowing between the voltage terminal and the semiconductor switch element and outputs a detection voltage, and a current detector Control signal generating means for outputting at least one of an upper threshold voltage and a lower threshold voltage corresponding to the current detection sensitivity and the offset voltage, and when the detected voltage is greater than the upper threshold voltage or the detected voltage is smaller than the lower threshold voltage In some cases, the semiconductor switching device includes a gate cutoff circuit that turns off the semiconductor switch element.

  A power conversion device according to the present invention includes a semiconductor switch element connected to a voltage terminal, a current detector that detects a current flowing between the voltage terminal and the semiconductor switch element and outputs a detection voltage, and a current detector Control signal generating means for outputting at least one of an upper threshold voltage and a lower threshold voltage corresponding to the current detection sensitivity and the offset voltage, and when the detected voltage is greater than the upper threshold voltage or the detected voltage is smaller than the lower threshold voltage In some cases, a gate cutoff circuit for turning off the semiconductor switch element is provided, so even if a process of adjusting the output characteristics of the current detector by a circuit element such as a resistance element is unnecessary, an overcurrent in the current detection line Is detected instantly, the semiconductor switch element with fast response is turned off, and the semiconductor switch element is protected against overcurrent. That.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram for one output circuit of a power conversion device including a current detector according to Embodiment 1 for carrying out the present invention. In FIG. 1, the semiconductor switch elements 1 and 2 of the main circuit are constituted by parallel bodies of IGBTs (Insulated Gate Bipolar Transistors) 1a and 2a and diodes 1b and 2b. In the parallel body, the collector terminals of the IGBTs 1a and 2a are connected to the cathode terminals of the diodes 1b and 2b, respectively, and the emitter terminals of the IGBTs 1a and 2a and the anode terminals of the diodes 1b and 2b are connected to each other.

  The positive terminal of the smoothing capacitor 3 that is a DC voltage input unit is connected to the collector terminal of the semiconductor switch element 1. The emitter side terminal of the semiconductor switch element 1 is connected to the collector side terminal of the semiconductor switch element 2 and the AC terminal 5 which is a voltage terminal. That is, the semiconductor switch elements 1 and 2 are connected to the voltage terminal. The N terminal on the negative voltage side of the smoothing capacitor 4 is connected to the emitter side terminal of the semiconductor switch element 2. The semiconductor switch element 1 and the semiconductor switch element 2 constitute a main circuit for one output of the power converter.

  The semiconductor switch element 1 is driven by a gate driver circuit 6. The semiconductor switch element 2 is driven by a gate driver circuit 7. The gate driver circuits 6 and 7 convert a control voltage signal based on a predetermined common voltage into a gate drive voltage signal based on the emitter terminal voltage of each of the IGBTs 1a and 2a. The gate driver circuits 6 and 7 have a function of increasing the current supply capability to a necessary current level in order to drive the IGBTs 1a and 2a.

  The magnetic core 8 has an annular shape, has an air gap in part, and surrounds an AC output line 5a (current detection line) connecting the semiconductor switch element 1 and the semiconductor switch element 2 to the AC terminal 5. is set up. In the air gap of the magnetic core 8, a Hall element 9 that converts a magnetic flux generated by a current flowing through the AC output line 5 a into a voltage is disposed. The output terminal of the Hall element 9 is connected to the input terminal of a current detection circuit 10 that amplifies the output voltage of the Hall element 9 to a desired value. The current detector uses a Hall element 9, and includes a magnetic core 8, a Hall element 9, and a current detection circuit 10. The current detector detects a current flowing between the AC terminal 5 which is a voltage terminal and the semiconductor switch elements 1 and 2 and outputs a detection voltage.

  The current detection output line Isen of the current detection circuit 10 is connected to each input terminal of the positive voltage side gate cutoff circuit 11, the negative voltage side gate cutoff circuit 12 and the microcomputer 13. The detection voltage is input to the positive voltage side gate cutoff circuit 11, the negative voltage side gate cutoff circuit 12, and the microcomputer 13 via the current detection output line Isen. The microcomputer 13 controls the positive voltage side gate cutoff circuit 11, the negative voltage side gate cutoff circuit 12 and the analog switch circuit 14. Capacitors 15 and 16 for holding threshold voltage data are respectively connected between the analog switch circuit 14 and the positive voltage side gate cutoff circuit 11 and between the analog switch circuit 14 and the negative voltage side gate cutoff circuit 12. Has been.

  A gate signal line GateH from the microcomputer 13 and an overcurrent threshold line IthH from the capacitor 15 are connected to the input terminals of the positive voltage side gate cutoff circuit 11. A gate drive signal line GateH * connected to the input terminal of the gate driver circuit 6 is connected to the output terminal of the positive voltage side gate cutoff circuit 11. Similarly, a gate signal line GateL from the microcomputer 13 and an overcurrent threshold line IthL from the capacitor 16 are connected to the input terminals of the negative voltage side gate cutoff circuit 12. A gate drive signal line GateL * connected to the input terminal of the gate driver circuit 7 is connected to the output terminal of the negative voltage side gate cutoff circuit 12. The overcurrent threshold line IthH and the overcurrent threshold line IthL are connected to the output terminal of the analog switch circuit 14 via the capacitors 15 and 16. An analog data output line Ith, a selection signal line SelectH, and a selection signal line SelectL from the microcomputer 13 are connected to input terminals of the analog switch circuit 14.

Here, the detail of the circuit structure for one output circuit of a power converter device is demonstrated. FIG. 2 is a circuit diagram of Hall element 9 and current detection circuit 10 according to the first embodiment. The current detection circuit 10 includes a constant current circuit unit having a function of a constant current circuit for the Hall element 9 and an amplifier circuit unit having a function of an amplifier circuit. First, the function of the constant current circuit will be described. One terminal of the Hall element 9 in the vertical direction is connected to the power supply Vcc, and the other terminal is connected to the collector terminal of the transistor Tr. The emitter terminal of the transistor Tr is connected to a common voltage line (control signal reference voltage line) via a resistor Rc, and the base terminal of the transistor Tr is connected to the output terminal of the operational amplifier OPA1. A voltage obtained by dividing the power supply voltage Vcc by the resistor Ra and the resistor Rb is input to the + side input terminal of the operational amplifier OPA1. The negative input terminal of the operational amplifier OPA1 is connected to the connection point between the emitter terminal of the transistor Tr and the resistor Rc. The resistors Ra, Rb, Rc, the transistor Tr, and the operational amplifier OPA1 constitute a constant current circuit, and supplies a drive current to the Hall element 9. The drive current ih that flows through the Hall element 9 can be expressed as Equation (1).
ih = Rb / (Rc × (Ra + Rb)) × Vcc (1)

Next, the function of the amplifier circuit will be described. An output voltage depending on the magnetic flux density of the magnetic core 8 is output from the horizontal output terminal of the Hall element 9. One output terminal in the horizontal direction is connected to the negative input terminal of the operational amplifier OPA2 through the resistor R1, and the other output terminal in the horizontal direction is connected to the positive input terminal of the operational amplifier OPA2 through the resistor R2. Yes. The negative input terminal of the operational amplifier OPA2 is also connected to the output terminal of the operational amplifier OPA2 via the resistor R3, and is connected to the detection current output line Isen. The + side input terminal of the operational amplifier OPA2 is connected via a resistor R4 to a voltage terminal Vref that determines the center voltage of the amplitude of the output voltage from the Hall element 9. Assuming that the resistance values of the resistors R1 and R2 are the same and the resistance values of the resistors R3 and R4 are the same, and the voltage between the output terminals of the Hall element 9 is ΔV, the detection voltage at the current detection output line Isen is The voltage value Visen that is can be expressed as shown in Equation (2).
Visen = Vref + R3 / R1 × ΔV −−− (2)
From the equation (2), it can be seen that in the amplifier circuit section, the center value of the amplitude of the output voltage of the Hall element 9 is set to Vref, and the amplitude of the output voltage is amplified by R3 / R1 times.

  FIG. 3 is a circuit diagram of the analog switch circuit 14 and the data holding capacitors 15 and 16 in the first embodiment. The analog switch circuit 14 includes bidirectional n-type MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) and p-type MOSFETs connected in parallel, switch units 141 and 143, and gate circuits 142 and 144 that drive the switch units. It is configured. The selection signal lines SelectH and SelectL are connected to the gate circuits 142 and 144, respectively.

  An analog data output line Ith is connected to the input terminals of the switch units 141 and 143. The overcurrent threshold line IthH and one terminal of the capacitor 15 are connected to one output terminal of the analog switch circuit 14. An overcurrent threshold line IthL and one terminal of the capacitor 16 are connected to the other output terminal of the analog switch circuit 14. The other terminal of each of the capacitors 15 and 16 is connected to a common voltage line. That is, a switch unit 141 and a capacitor 15 corresponding to the positive voltage side gate cutoff circuit 11 are provided between the microcomputer 13 which is a control signal generating means and the positive voltage side gate cutoff circuit 11 which is a gate cutoff circuit. . A switch unit 143 and a capacitor 16 corresponding to the negative voltage side gate cutoff circuit 12 are provided between the microcomputer 13 and the negative voltage side gate cutoff circuit 12 which is a gate cutoff circuit.

  Next, the operation will be described. The microcomputer 13 which is a control signal generating means calculates an upper limit threshold voltage and a lower limit threshold voltage according to the current detection sensitivity and offset voltage of the current detector, and the upper limit threshold voltage and the lower limit threshold voltage via the analog data output line Ith. At least one of the outputs. The upper limit threshold voltage and the lower limit threshold voltage are threshold voltages of the current detector corresponding to the upper limit current and the lower limit current of the allowable current that may flow through the AC output line 5a in order to protect the semiconductor switch elements 1 and 2. As an example, the upper threshold voltage may be set to 4.5V, and the lower threshold voltage may be set to 0.5V. At this time, a low voltage and a high voltage are output from the microcomputer 13 to the selection signal lines SelectH and SelectL, respectively, and the switch unit 141 is turned on and the switch unit 143 is turned off. As a result, the capacitor 15 stores an upper limit threshold voltage corresponding to the upper limit value of the allowable current of the AC output line 5a.

  Next, a High voltage and a Low voltage are output to the selection signal lines SelectH and SelectL, respectively, and the switch unit 141 is switched off and the switch unit 143 is switched on. After the on / off state is switched, the lower limit threshold voltage corresponding to the lower limit value of the allowable current of the AC output line 5a is output to the analog data output line Ith. As a result, the lower threshold voltage is accumulated in the capacitor 16. The voltages stored in the capacitors 15 and 16 are output to the positive voltage side gate cutoff circuit 11 and the negative voltage side gate cutoff circuit 12, respectively. That is, the microcomputer 13 is a plurality of gate cut-off circuits that control the on / off operation of the switch units 141 and 143 to supply at least one of the upper threshold voltage and the lower threshold voltage via the capacitors 15 and 16. It outputs to the positive voltage side gate cutoff circuit 11 and the negative voltage side gate cutoff circuit 12.

  Here, by setting both the switch portions 141 and 143 to the OFF state, the upper limit threshold voltage data is held in the capacitor 15 and the lower limit threshold voltage data is held in the capacitor 16, respectively. The threshold voltage data held in the capacitors 15 and 16 gradually change due to a voltage leakage phenomenon. For this reason, the switching operation of the analog switch circuit 14 is periodically repeated, and data of a predetermined threshold voltage is accumulated in the capacitors 15 and 16.

  The microcomputer 13 or a storage element that supports the operation of the microcomputer 13 stores the relationship between the current value and the detection voltage of the current detector in order to accurately control the current flowing through the AC output line 5a of the power converter. ing. Further, the upper limit threshold voltage and the lower limit threshold voltage corresponding to the upper limit value of the allowable current flowing through the AC output line 5a and the lower limit value of the allowable current are determined by the relationship between the current value and the detection voltage of the current detector. The detection voltage output to the detection current output line Isen from the current detector in a state where no current flows through the AC output line 5a and a known current are supplied to the AC output line 5a in advance at the time of product inspection. Based on the detection voltage from the current detector in the state, the current detection sensitivity, which is the sensitivity of the detection voltage to the current, and the offset voltage are calculated, and the relationship between the current value and the detection voltage of the current detector is obtained.

  FIG. 4 is a circuit diagram of the positive voltage side gate cutoff circuit 11 and the negative voltage side gate cutoff circuit 12 in the first embodiment. FIG. 4A shows a circuit diagram of the positive voltage side gate cutoff circuit 11. The positive voltage side gate cutoff circuit 11 includes a comparator COPH, an AND logic circuit ANDH, a resistor RxH, and a power supply Vcc. FIG. 4B shows a circuit diagram of the negative voltage side gate cutoff circuit 12. The negative voltage side gate cutoff circuit 12 includes a comparator COPL, an AND logic circuit ANDL, a resistor RxL, and a power supply Vcc. The output terminals of the comparators COPH and COPL are connected to the power supply Vcc via resistors RxH and RxL, respectively, and are connected to one input terminal of each of the AND logic circuits ANDH and ANDL.

  Gate signal lines GateH and GateL from the microcomputer 13 are connected to the other input terminals of the AND logic circuits ANDH and ANDL, respectively. The output terminals of the AND logic circuits ANDH and ANDL are connected to gate drive signal lines GateH * and GateL *, respectively. The overcurrent threshold line IthH is connected to the + side input terminal of the comparator COPH of the positive voltage side gate cutoff circuit 11. The detection current output line Isen is connected to the negative input terminal of the comparator COPH. Further, the detection current output line Isen is connected to the + side input terminal of the comparator COPL of the negative voltage side gate cutoff circuit 12, and the overcurrent threshold line IthL is connected to the − side input terminal of the comparator COPL.

  Next, the operation will be described. When a current within the allowable current value range flows through the AC output line 5a, the detection voltage of the detection current output line Isen is smaller than the upper limit threshold voltage of the overcurrent threshold line IthH and is lower than the lower limit threshold voltage of the overcurrent threshold line IthL. large. For this reason, the outputs of the respective comparators COPH and COPL are high voltages. Here, the High voltage corresponds to Vcc. Therefore, the gate signal output from the microcomputer 13 is output as it is to the gate drive signal lines GateH * and GateL *.

  When a current outside the allowable current value range flows through the AC output line 5a and the detection voltage of the detection current output line Isen becomes larger than the upper limit threshold voltage of the overcurrent threshold line IthH, the output of the comparator COPH becomes a low voltage. Regardless of the state of the gate signal line GateH, the output to the gate drive signal line GateH * becomes a Low voltage, and the semiconductor switch element 1 is cut off. Further, when the detection voltage of the detection current output line Isen becomes lower than the lower limit threshold voltage of the overcurrent threshold line IthL, the output of the comparator COPL becomes a low voltage, and therefore the gate drive signal line regardless of the state of the gate signal line GateL. The output to GateL * becomes a Low voltage, and the semiconductor switch element 2 is cut off. That is, the positive voltage side gate cutoff circuit 11 and the negative voltage side gate cutoff circuit 12 turn off the semiconductor switch elements 1 and 2 when the detected voltage is higher than the upper threshold voltage or when the detected voltage is lower than the lower threshold voltage. This is a gate cutoff circuit.

  When the semiconductor switch elements 1 and 2 are shut off by comparing the detection voltage with the threshold voltage, accurate shutoff can be performed by setting the threshold voltage according to the current detection sensitivity and the offset voltage of the current detector. FIG. 5 is a schematic diagram of output characteristics of the current detector in the first embodiment. FIG. 5A shows the detection voltages of the current detector A and the current detector B having different output characteristics when the threshold voltage is fixed to a specific constant value by power supply voltage division using a fixed resistor. Yes. The current detector A detects the correct current flowing through the AC output line 5a. When an overcurrent flows, the current detector A can protect the semiconductor switch element by performing a gate cutoff operation according to the threshold voltage. On the other hand, unlike the case of the current detector A in which the threshold voltage for operating the gate cutoff circuit is different from that in the current detector A, the current detector B does not perform the gate cutoff operation even if the overcurrent flows and exceeds the threshold voltage. Inconveniences such as gate shutoff occur.

  FIG. 5B shows detection voltages of the current detector A and the current detector B having different output characteristics in the case where the current detection according to the present embodiment is performed. Even if the current detector A and the current detector B having different output characteristics are used, the upper and lower threshold voltages are set corresponding to the individual current detectors, so that the gate cutoff operation can be performed at a desired threshold voltage. It becomes. Thus, the threshold voltage can be corrected according to the characteristics of the current detector using the microcomputer 13 without fixing the threshold voltage using the resistance element. Further, the microcomputer 13 compares the threshold voltage corresponding to the preset overcurrent with the detected voltage without determining whether the current value exceeds the threshold voltage, and forms a gate cutoff signal. The operation time is 1 μs or less, and high-speed overcurrent detection and gate interruption are possible.

  In addition, the upper threshold voltage or the lower threshold voltage is set to the gate cutoff by matching the timing of outputting the upper threshold voltage or the lower threshold voltage corresponding to each gate cutoff circuit and the ON / OFF timing of the switch unit 141 or 143. It can be input individually and sequentially into the circuit. Therefore, even when the microcomputer 13 has one analog signal output terminal, the semiconductor switch elements 1 and 2 can be protected via the plurality of gate cutoff circuits 11 and 12. In other words, by providing the analog switch circuit 14, if the three-phase output inverter includes six switch units, only one analog data output terminal needs to be provided. Even when the number of outputs of the power conversion device is further increased, one output circuit portion of the power conversion device can be configured with only one output terminal regardless of the limit of the number of analog output terminals of the microcomputer 13.

  As described above, the control signal generating means for outputting at least one of the upper threshold voltage and the lower threshold voltage corresponding to the current detection sensitivity and offset voltage of the current detector, and the detected voltage is larger than the upper threshold voltage Or, when the detection voltage is lower than the lower threshold voltage, a gate cutoff circuit for turning off the semiconductor switch element is provided, so that the step of adjusting the output characteristics of the current detector by a circuit element such as a resistance element is unnecessary However, it is possible to instantaneously detect an overcurrent in the current detection line, turn off the semiconductor switch element having a quick response, and protect the semiconductor switch element against the overcurrent. In addition, since the process of adjusting the output characteristics of the current detector is not necessary, the manufacturing process can be simplified.

Embodiment 2. FIG.
FIG. 6 is a configuration diagram for one output circuit of a power conversion device including a current detector according to Embodiment 2 for carrying out the present invention. In FIG. 6, the microcomputer 13 is directly connected to the positive voltage side gate cutoff circuit 11 via the overcurrent threshold line IthH and directly connected to the negative voltage side gate cutoff circuit 12 via the overcurrent threshold line IthL. This is different from the first embodiment. In FIG. 6, the same reference numerals as those in FIG. 1 denote the same or corresponding parts, and this is common throughout the entire specification. Moreover, the aspect of the component which appears in the whole specification is an illustration to the last, and is not limited to these description.

  When there is a margin in the number of analog data output terminals of the microcomputer 13, the microcomputer 13 may be directly connected to the current threshold lines IthH and IthL without using an analog switch circuit. If the power converter is a three-phase output inverter, six analog data output terminals are required.

  Next, the operation will be described. When a current within the allowable current value range flows through the AC output line 5a, the detection voltage of the detection current output line Isen is smaller than the upper limit threshold voltage of the overcurrent threshold line IthH and is lower than the lower limit threshold voltage of the overcurrent threshold line IthL. large. For this reason, the outputs of the respective comparators COPH and COPL are high voltages. Here, the High voltage corresponds to Vcc. Therefore, the gate signal output from the microcomputer 13 is output as it is to the gate drive signal lines GateH * and GateL *.

  When a current outside the allowable current value range flows through the AC output line 5a and the detection voltage of the detection current output line Isen becomes larger than the upper limit threshold voltage of the overcurrent threshold line IthH, the output of the comparator COPH becomes a low voltage. Regardless of the state of the gate signal line GateH, the output to the gate drive signal line GateH * becomes a Low voltage, and the semiconductor switch element 1 is cut off. Further, when the detection voltage of the detection current output line Isen becomes lower than the lower limit threshold voltage of the overcurrent threshold line IthL, the output of the comparator COPL becomes a low voltage, and therefore the gate drive signal line regardless of the state of the gate signal line GateL. The output to GateL * becomes a Low voltage, and the semiconductor switch element 2 is cut off. That is, the positive voltage side gate cutoff circuit 11 and the negative voltage side gate cutoff circuit 12 turn off the semiconductor switch elements 1 and 2 when the detected voltage is higher than the upper threshold voltage or when the detected voltage is lower than the lower threshold voltage. This is a gate cutoff circuit.

  Thus, the threshold voltage can be corrected according to the characteristics of the current detector using the microcomputer 13 without fixing the threshold voltage using the resistance element. In addition, since the comparator compares the preset overcurrent threshold voltage and the detection voltage and forms a gate cutoff signal, the operation time is 1 μs or less, and high-speed overcurrent detection and gate cutoff are possible.

  As described above, the control signal generating means for outputting at least one of the upper threshold voltage and the lower threshold voltage corresponding to the current detection sensitivity and offset voltage of the current detector, and the detected voltage is larger than the upper threshold voltage Or, when the detection voltage is lower than the lower threshold voltage, a gate cutoff circuit for turning off the semiconductor switch element is provided, so that the step of adjusting the output characteristics of the current detector by a circuit element such as a resistance element is unnecessary However, it is possible to instantaneously detect an overcurrent in the current detection line, turn off the semiconductor switch element having a quick response, and protect the semiconductor switch element against the overcurrent. In addition, since the process of adjusting the output characteristics of the current detector is not necessary, the manufacturing process can be simplified.

  In any embodiment, instead of outputting an analog signal from the microcomputer 13, a plurality of digital output terminals of the microcomputer 13 are used, an analog signal is formed using a D / A conversion circuit, and the signal May be output to the analog signal output line. Further, the microcomputer 13 may correct the current detection sensitivity and the offset voltage, and other types of methods such as a shunt resistance type may be applied as a current detector. As a power converter, a diode and a semiconductor switch element may be used. The present invention may be applied to a DC / DC converter using a choke coil or a transformer of a type that constitutes one output circuit with a series body.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram for one output circuit of the power converter device provided with the current detector which shows Embodiment 1 of this invention. 1 is a circuit diagram of a Hall element and a current detection circuit according to Embodiment 1 of the present invention. 1 is a circuit diagram of an analog switch circuit and a capacitor according to Embodiment 1 of the present invention. It is a circuit diagram of the positive voltage side gate cutoff circuit and negative voltage side gate cutoff circuit in Embodiment 1 of this invention. It is a schematic diagram of the output characteristic of the current detector in Embodiment 1 of this invention. It is a block diagram for one output circuit of the power converter device provided with the current detector which shows Embodiment 2 of this invention.

Explanation of symbols

  1, 2 Semiconductor switch element, 3, 4 Smoothing capacitor, 5 AC terminal, 6, 7 Gate driver circuit, 8 Magnetic core, 9 Hall element, 10 Current detection circuit, 11 Positive voltage side gate cutoff circuit, 12 Negative voltage side Gate cut-off circuit, 13 microcomputer, 14 analog switch circuit, 15, 16 capacitor, 141, 143 switch unit, 142, 144 gate circuit.

Claims (5)

A semiconductor switch element connected to the voltage terminal;
A current detector that detects a current flowing between the voltage terminal and the semiconductor switch element and outputs a detection voltage;
Control signal generating means for outputting at least one of an upper threshold voltage and a lower threshold voltage corresponding to the current detection sensitivity and offset voltage of the current detector;
A power conversion device comprising: a gate cutoff circuit that turns off the semiconductor switch element when the detected voltage is greater than the upper threshold voltage or when the detected voltage is smaller than the lower threshold voltage. Between the control signal generating means and the gate cutoff circuit, a switch unit and a capacitor corresponding to the gate cutoff circuit are provided,
The control signal generating means controls the on / off operation of the switch unit and outputs at least one of an upper threshold voltage and a lower threshold voltage to the gate cutoff circuit via the capacitor. The power converter according to 1. The power conversion device according to claim 1 or 2, wherein the control signal generation means outputs at least one of an upper limit threshold voltage and a lower limit threshold voltage to each of the plurality of gate cutoff circuits. The power converter according to any one of claims 1 to 3, wherein the control signal generating means is a microcomputer. The power converter according to any one of claims 1 to 3, wherein the current detector uses a Hall element.

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