JP4713347B2 - Semiconductor device drive circuit - Google Patents

Description

  The present invention relates to a power converter for converting direct current and alternating current to each other, and more particularly to a semiconductor element drive circuit for controlling a switching element used in the power converter.

  IGBTs (Insulated Gate Bipolar Transistors) capable of high-speed switching and controlling large power are used in a wide range of fields from home appliances to high-power applications such as railway inverters. The IGBT has three terminals of a gate, a collector, and an emitter, and can control a current flowing between the collector and the emitter by a voltage applied to the gate. What is important when using an IGBT is gate control during switching. At the time of switching, there are problems such as destruction of the IGBT and generation of noise due to loss, overvoltage, voltage / current vibration and the like.

In order to cope with this, a means for monitoring the state between the collector and the emitter and applying feedback to the gate is disclosed in Patent Document 1 and the like. In Patent Document 1, the current flowing through the IGBT is monitored by the voltage generated in the inductance connected in series with the IGBT or the parasitic inductance of the wiring, and when the change of the voltage exceeds a certain condition, the gate control is fed back. Yes.
JP 2004-312796 A

  However, in the above-described invention, since a change in current is detected and fed back to the gate, the signal passes through a di / dt signal measuring means, an interface circuit, an amplifier, and the like, so that a delay occurs until the gate is controlled. For this reason, it can be applied when the time change is slow, such as detection of a dynamic avalanche state, etc., but in the case of a steep change such as during normal switching operation, control of the gate is not in time and control is not possible. There was a problem.

  In order to solve the above problems, in the present invention, an IGBT, a switching speed control circuit that controls the switching speed of the IGBT, a switching detection circuit that detects the switching start of the IGBT and sends a signal to the switching speed control circuit, A current detection circuit that detects a change in the current of the IGBT and sends a signal to the switching speed control circuit, and the switching speed control circuit is ready for operation by a signal from the switching detection circuit, It is characterized by operating with signals.

  According to the present invention, when the switching of the IGBT is started, the switching detection circuit detects the switching start, and the switching speed control circuit is set in an operation ready state in advance, so that the gate can be controlled without delay when the IGBT is switched. Overvoltage and noise generated during switching can be reduced.

  If the overvoltage and noise can be reduced, a snubber circuit and a filter circuit for suppressing surges are not necessary, and the inverter device can be reduced in size and weight. In addition, since destruction due to overvoltage can be prevented, there is an effect of improving the reliability of the inverter device.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows a first embodiment of the present invention. In FIG. 1, 100 is a command unit that outputs a signal for driving the IGBT, 101 is a gate drive circuit, 102 is a switching detection circuit, 103 is a current detection circuit, 104 is an IGBT, 105 is a freewheel diode, and 106 is a current. Inductance for detection. 106 may be an inductance component connected in series with the IGBT, an inductance of wiring, or a parasitic inductance in wiring inside the IGBT package. Reference numerals 110 to 114 denote signals of the respective parts, and the change with time is shown in FIG. 2 together with the operation waveform of the IGBT.

  The first embodiment will be described with reference to FIGS. 1 and 2. When a turn-off command is output from the command unit 100 at time t1, the signal 110 from the command unit falls to the Lo level, and the drive circuit 101 starts to decrease the gate voltage to turn off the IGBT. On the other hand, when receiving the turn-off command, the switching detection circuit 102 immediately sets the output 111 to the Hi level. When the output 111 from the switching detection circuit 102 is input, the switching speed control circuit 107 gives a necessary potential to the internal circuit node, and is ready to operate quickly when a trigger from the current detection circuit 103 is applied. Become. When the drive circuit 101 reduces the potential of the gate of the IGBT to some extent, the IGBT starts to shift to the off state. When the IGBT starts to turn off, the collector voltage increases, and then the collector current starts to decrease at time t2. When the collector current changes, a voltage is generated across the inductance 106, and 114 becomes Hi level. The current detection circuit 103 determines that the current has changed when 114 becomes higher than a predetermined voltage, and inverts 112 to the Hi level. The switching speed control circuit 107 starts the gate control operation with the inversion of 112 as a trigger.

  As described above, according to the first embodiment, since the switching speed control circuit 107 is in an operation ready state at the start of switching, the gate can be quickly controlled when a current change occurs, and at the time of switching without delay. You can control the gate. As a result, gate control is possible even during a normal switching operation that has been difficult in the past, and overvoltage and noise generated during switching can be reduced.

  FIG. 3 shows a second embodiment of the present invention. 3, the same components as those in FIG. 1 are denoted by the same reference numerals. The feature of the second embodiment is that the switching speed of the IGBT is controlled by inputting the output of the switching speed control circuit 107 to the gate drive circuit 101 and the switching speed control circuit 107 controlling the gate drive circuit 101. . An IGBT gate drive circuit with a rated current of several hundred amps must instantaneously control a few amps of current. For this reason, switching elements having a rating of about several amperes are used in the gate drive circuit 101, but these elements are large in size and high in cost. When the switching speed control circuit 107 directly controls the gate of the IGBT as in the first embodiment, these elements are also required inside the switching speed control circuit 107. In the second embodiment, since the switching speed control circuit 107 only controls the gate driving circuit 101, these switching elements are not necessary, which is effective in reducing the size and cost of the gate driving circuit.

  FIG. 4 shows a third embodiment of the present invention. 4, the same components as those in FIGS. 1 and 2 are denoted by the same reference numerals. In FIG. 4, reference numeral 300 denotes a voltage detection circuit.

  The feature of the third embodiment is that a voltage detection circuit 300 is provided in place of the current detection circuit 103 of the first embodiment as means for detecting the switching of the IGBT. In the first embodiment, the current is detected by using the parasitic inductance of the wiring. However, when the wiring inductance is configured to be sufficiently small, a sufficient voltage for detecting the current cannot be obtained and the current change is detected. May not be detected. In addition, when the present technology is applied to an IGBT having a small current of about several A, the voltage generated in the parasitic inductance is similarly reduced, and thus the first embodiment cannot be applied.

  In the third embodiment, the collector voltage is monitored, and when the collector voltage exceeds a predetermined voltage, it is determined that the IGBT has been cut off, and a trigger signal is output to the switching speed control circuit 107. The voltage for determining that the IGBT has entered the cutoff state may be set to, for example, a collector voltage at which the collector current at time t2 in FIG. By adopting such a configuration, the present invention can be applied even to an IGBT having a small parasitic inductance or an IGBT having a small current capacity.

  In the third embodiment, the method of directly controlling the gate of the IGBT by the output of the switching speed control circuit 107 is shown. Of course, the second embodiment in which the gate driving circuit 101 is controlled by the output of the switching speed control circuit 107 is shown. Applicable to configuration.

  FIG. 5 shows a fourth embodiment of the present invention. 5, the same components as those in FIGS. 1 to 4 are denoted by the same reference numerals. In FIG. 5, reference numeral 400 denotes a gate resistor, and 401 denotes a gate current detection circuit. A switching detection circuit 102 is configured by the gate resistor 400 and the gate detection circuit 401.

  The feature of the fourth embodiment is that the detection of switching is not detected by a signal from the command unit, but is determined by a gate current. The gate current detection circuit monitors the gate current by monitoring the voltage generated in the gate resistor 400. When the gate current exceeds a predetermined value, it is determined that switching is started, and a signal is output to the switching speed control circuit 107. In this case, there are a method of determining by the absolute value of the gate current and a method of determining by the integrated value of the gate current, and the latter is characterized by being resistant to noise.

  The fourth embodiment also has a feature that the period from the detection of the start of switching to the operation of the switching speed control circuit 107 can be shortened. In the case of the first and second embodiments, the switching speed control circuit is brought into a ready state as soon as a command value is input. The switching speed control circuit in the ready state easily operates when noise enters, and the circuit may operate at a time other than the desired timing. If the switching speed control circuit operates at a time other than the desired timing, a predetermined switching operation cannot be obtained, causing overvoltage and noise. For this reason, there is an advantage that malfunction can be suppressed by shortening the period from when the switching speed control circuit 107 is in a ready state to when it actually operates as in this embodiment.

  In the fourth embodiment, the IGBT gate is directly controlled by the output of the switching speed control circuit 107. Of course, the second embodiment in which the gate drive circuit 101 is controlled by the output of the switching speed control circuit 107 is shown. Applicable to configuration.

  FIG. 6 shows a fifth embodiment of the present invention. In FIG. 6, the same components as those in FIGS. 1 to 5 are denoted by the same reference numerals. In FIG. 6, 500 is a positive power supply line of the gate drive circuit, 501 to 506 are resistors, and 507 to 509 are bipolar transistors. The bipolar transistor 507 and the resistors 502 and 503 constitute the switching speed control circuit 107.

  The fifth embodiment describes a specific circuit configuration of the switching speed control circuit 107 described in the first embodiment. The drive circuit 101 shows only the bipolar transistor at the output stage, and other circuits are omitted.

  The operation will be described. First, consider a state in which the IGBT is turned on. When the IGBT is on, the output from the command unit 100 is at a high level, the bipolar transistor 508 is on, and the 509 is off. For this reason, the potential of the positive power supply line 500 is directly applied to the gate of the IGBT. On the other hand, a current corresponding to the load flows through the IGBT, but the output of 103 is always set to a high level when the current changes in this state. Since the current detection circuit 103 outputs a high level, the bipolar transistor 507 is off. Further, since the signal from the command unit 100 is an on command, the switching detection circuit 102 similarly outputs a high level.

  Next, when an off command is issued from command unit 100, bipolar transistor 508 is turned off and 509 is turned on. Then, current flows from the gate of the IGBT through the gate resistor 504, the bipolar transistor 509, and the resistor 505, and the gate voltage starts to decrease.

  As soon as the switching detection circuit 102 receives a signal from the command unit 100, the switching detection circuit 102 inverts the output to a low level and lowers the base potential of the bipolar transistor. At this time, the switching detection circuit 102 is set so as not to lower the base potential to the potential at which the bipolar transistor 507 is turned on, but to the base potential immediately before being turned on. Next, when the gate potential of the IGBT continues to decrease, the collector voltage starts to increase, and when the collector voltage reaches the power supply voltage, the collector current starts to decrease. Then, a voltage is generated in the inductance 106, and when this voltage exceeds a predetermined value, the current detection circuit 103 operates to lower the output to a low level. At this time, since the bipolar transistor 507 is already in the state immediately before being turned on by the switching detection circuit 102, it is turned on immediately when a signal from the current detection circuit 103 is input, and a current flows from the positive power supply line 500 to the gate. become. When a current flows into the gate through the bipolar transistor 507, a decrease in the gate potential of the IGBT is suppressed by this current, and the collector current can be gradually decreased.

  In the fifth embodiment, as the switching detection means, the means using the signal from the command unit 100 shown in the first embodiment is shown, but the same effect can be realized by the means for detecting by the gate current shown in the fourth embodiment. it can. Although the configuration using the current detection circuit 103 has been described, the same effect can be obtained even if the means for detecting the collector voltage shown in the second embodiment is applied.

  FIG. 7 shows a sixth embodiment of the present invention. In FIG. 7, the same components as those in FIGS. 1 to 6 are denoted by the same reference numerals. In FIG. 7, reference numerals 601 to 605 denote resistors and 606 to 608 denote bipolar transistors. The bipolar transistor 608 and the resistors 603, 604, and 605 constitute the switching speed control circuit 107.

  The sixth embodiment shows a specific circuit configuration of the switching speed control circuit 107 of the second embodiment. The drive circuit 101 shows only the bipolar transistor at the output stage, and other circuits are omitted. In the sixth embodiment, a variable gate resistance circuit using a bipolar transistor is shown as a switching speed control circuit.

  In general, an IGBT drive circuit receives a signal from a command unit and drives a bipolar transistor having a totem pole configuration as indicated by reference numerals 606 and 607 in FIG. 7 to control the gate of the IGBT. At this time, resistors as indicated by reference numerals 601 to 603 are arranged as elements for controlling the switching speed, but these resistance values are fixed and cannot be changed during the switching operation. In the sixth embodiment, the bipolar transistor 608 is used to change the resistance value at the time of turn-off.

  The operation of the circuit of FIG. 6 will be described. First, consider a state in which the IGBT is turned on. When the IGBT is on, the output from the command unit 100 is at a high level, the bipolar transistor 606 is on, and the 607 is off. For this reason, the potential of the positive power supply line 500 is directly applied to the gate of the IGBT. On the other hand, a current corresponding to the load flows through the IGBT, but the output of 103 is always set to a high level when the current changes in this state. Since the current detection circuit 103 outputs a high level, the bipolar transistor 608 is in a saturated state. In this circuit, the resistance value of 603 is set larger than the resistance value of 604. Further, since the signal from the command unit 100 is an on command, the switching detection circuit 102 outputs a high level.

  Next, when an off command is issued from the command unit 100, the bipolar transistor 606 is turned off and the 607 is turned on. Then, current flows from the gate of the IGBT through the gate resistor 602, the bipolar transistor 607, the resistor 604, and the bipolar transistor 608, and the gate voltage starts to decrease. As described above, since the resistance value of 603 is set larger than the resistance value of 604, the gate current flows through the resistance 604. As soon as the switching detection circuit 102 receives a signal from the command unit 100, the switching detection circuit 102 inverts the output to a low level and lowers the base potential of the bipolar transistor. At this time, the switching detection circuit 102 does not lower the gate potential to the potential at which the bipolar transistor 608 is turned off, but sets the base potential to be lowered so that the bipolar transistor 608 is in a state immediately before the transition from the saturation region to the active region. Next, when the gate potential of the IGBT continues to decrease, the collector voltage starts to increase, and when the collector voltage reaches the power supply voltage, the collector current starts to decrease. Then, a voltage is generated in the inductance 106, and when this voltage exceeds a predetermined value, the current detection circuit 103 operates to lower the output to a low level. At this time, since the bipolar transistor 608 has already been operated by the switching detection circuit 102 immediately before being turned off, the signal is immediately turned off when the signal from the current detection circuit 103 is input so that the gate current flows through the resistor 603. become. Since the resistor 603 is set larger than the resistor 604, the turn-off speed can be reduced.

  In the sixth embodiment, as the switching detection means, the means using the signal from the command unit 100 shown in the first and second embodiments is shown, but the same effect can be obtained by the means for detecting by the gate current shown in the third embodiment. Can be realized. Although the configuration using the current detection circuit 103 has been described, the same effect can be obtained even if the means for detecting the collector voltage shown in the second embodiment is applied.

It is a circuit diagram explaining Example 1 of the present invention. It is a figure which shows the operation | movement waveform of Example 1 of this invention. It is the circuit diagram explaining Example 2 of this invention. It is a circuit diagram explaining Example 3 of the present invention. It is the circuit diagram explaining Example 4 of this invention. It is the circuit diagram explaining Example 5 of this invention. It is the circuit diagram explaining Example 6 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Command part 101 Gate drive circuit 102 Switching detection circuit 103 Current detection circuit 104 IGBT
DESCRIPTION OF SYMBOLS 105 Freewheel diode 106 Inductance 107 Switching speed control circuit 300 Voltage detection circuit 400 Gate resistance 401 Gate current detection circuit 500 Positive power supply line of gate drive circuit 501-506 Resistance 507-509 Bipolar transistor 601-605 Resistance 606-608 Bipolar transistor

Claims (14)

A switching element having a pair of main terminals for energizing a main current and a control terminal for controlling the main current, a switching speed control circuit for controlling the switching speed of the switching element, and the beginning of the switching operation of the switching element A switching detection circuit that detects and sends a signal to the switching speed control circuit; and a current detection circuit that detects a change in the main current of the switching element and sends a signal to the switching speed control circuit, the switching speed control circuit A driving circuit for a semiconductor device, wherein a signal from the switching detection circuit is put into an operation ready state in which the potential of the gate of the semiconductor device is lowered, and a control operation of the gate is started by a signal from the current detection circuit. The drive circuit for a semiconductor device according to claim 1,
The switching speed control circuit is composed of a bipolar transistor and a resistor. In the operation ready state, the base potential is not lowered to the potential at which the bipolar transistor is turned on, but is set to the state at which the base potential is lowered to the state immediately before being turned on. drive circuit of a semiconductor device characterized by that. In the drive circuit of the semiconductor element according to claim 1 or 2,
A drive circuit for a semiconductor element, wherein the current detection circuit detects a voltage generated in an inductance in a main current path of the switching element . In the drive circuit of the semiconductor element according to claim 1 or 2,
The switching detection circuit monitors a control signal input to a control terminal of the switching element, determines that switching is started when the signal is inverted , and transmits a signal to the switching speed control circuit. A driving circuit for a semiconductor device. In the drive circuit of the semiconductor element according to claim 1 or 2,
The switching detection circuit monitors the current flowing through the control terminal of the switching element, determines that switching starts when the current value exceeds a predetermined value, and transmits a signal to the switching speed control circuit. A drive circuit for a semiconductor element, characterized in that: In the drive circuit of the semiconductor element according to claim 1 or 2 ,
Transmitting the switching detection circuit integrates the current flowing to the control terminal of the switching element, the integral value is determined to start switching when exceeds a predetermined value determined in advance, a signal to said switching speed control circuit A drive circuit for a semiconductor element, characterized in that: In the drive circuit of the semiconductor device according to any one of claims 1 to 6,
The switching speed control circuit is composed of a resistor connected to the control terminal of the switching element and a circuit that varies the resistance. When the switching speed control circuit is in an operating state by a signal from the current detection circuit. And a resistance value of the variable resistor is increased . A switching element having a pair of main terminal pairs and a control terminal for controlling a main current flowing between the pair of main terminals; a switching speed control circuit for controlling a switching speed of the switching element; and a switching operation of the switching element. A switching detection circuit for detecting a start and sending a signal to the switching speed control circuit; and a voltage between the main terminals of the switching element is monitored, and the switching speed control is performed when the voltage between the main terminals exceeds a predetermined value. A voltage detection circuit for sending a signal to the circuit, the switching speed control circuit is in an operation ready state in which the potential of the gate of the semiconductor element is lowered by a signal from the switching detection circuit, and the signal from the voltage detection circuit A drive circuit for a semiconductor element, characterized by starting a gate control operation . In the drive circuit of the semiconductor element according to claim 8 ,
The switching speed control circuit is composed of a bipolar transistor and a resistor. In the operation ready state, the base potential is not lowered to the potential at which the bipolar transistor is turned on, but is set to the state at which the base potential is lowered to the state immediately before being turned on. drive circuit of a semiconductor device characterized by that. In the drive circuit of the semiconductor element according to claim 8 or 9 ,
A drive circuit for a semiconductor element, wherein the voltage detection circuit detects a voltage generated in an inductance connected to one main terminal of the main terminal pair of the semiconductor element. In the drive circuit of the semiconductor element according to claim 8 or 9 ,
The switching detection circuit monitors a control signal input to a control terminal of the switching element, determines that switching is started when the signal is inverted , and transmits a signal to the switching speed control circuit. A driving circuit for a semiconductor device. In the drive circuit of the semiconductor element according to claim 8 or 9 ,
Transmitting the switching detection circuit monitors the current flowing to the control terminal of the switching element, it is determined that the start of the switching when the current value exceeds a predetermined value determined in advance, a signal to said switching speed control circuit A drive circuit for a semiconductor element, characterized in that: In the drive circuit of the semiconductor element according to claim 8 or 9,
The switching detection circuit integrates the current flowing through the control terminal of the switching element, determines that switching starts when the integral value exceeds a predetermined value, and transmits a signal to the switching speed control circuit. A drive circuit for a semiconductor element, characterized in that: In the drive circuit of the semiconductor element according to any one of claims 8 to 13,
The switching speed control circuit is composed of a resistor connected to the control terminal of the switching element and a circuit that varies the resistance. When the switching speed control circuit is in an operating state by a signal from the voltage detection circuit. And a resistance value of the variable resistor is increased.

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