JP2005328609A - Drive circuit for voltage drive type semiconductor element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the switching loss of a voltage drive type semiconductor element while suppressing radiation noise generated from the voltage drive type semiconductor element. <P>SOLUTION: A capacitor C101 and a current limiting circuit Q102 are connected in series between the gate terminal G of the voltage drive type semiconductor element Q101 and the common line of the drive circuit of the voltage drive type semiconductor element Q101. This drive circuit limits a current so that the current flowing to the capacitor C101 may decrease according as the collector current of the voltage drive type semiconductor element Q101 increases by means of an inventing amplifier 110, an operational amplifier I101, LP filters R102 and C102, and a resistor R101. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a circuit for driving a voltage-driven semiconductor element such as an IGBT (Insulated Gate Bipolar Transistor).

  In a power semiconductor device such as an inverter that performs power switching using a voltage-driven semiconductor element and drives a load, if the collector current change rate dIc / dt when the voltage-driven semiconductor element is turned on is large, The current and voltage of the oscillates and radiates noise. This increase in radiation noise not only causes a radiation noise disturbance, but also makes the operation of the power semiconductor device itself unstable.

  Therefore, a capacitor is connected between the gate and the emitter of the voltage-driven semiconductor element to reduce the collector current change rate dIc / dt at turn-on to suppress the generation of radiation noise, and the collector voltage Vce at turn-on is reduced. There is known a drive circuit for a voltage-driven semiconductor element in which the “tail” (a phenomenon in which the collector voltage Vce gradually decreases to the on-voltage when the voltage-driven semiconductor element is turned on) is reduced to suppress switching loss. (For example, refer to Patent Document 1).

Prior art documents related to the invention of this application include the following.
JP 2003-125574 A

  However, in the conventional voltage-driven semiconductor element drive circuit described above, the amount of radiation noise is reduced in the region where the collector current Ic is large, but the voltage-driven semiconductor element is always switched between the gate and the emitter when switching. The connected capacitor is charged / discharged, the switching speed is lowered, and the switching loss is increased. Therefore, even if the tail of the collector voltage Vce at the turn-on time of the voltage-driven semiconductor element is reduced to reduce the switching loss, the switching loss increases due to the reduction of the switching speed due to the charging / discharging of the capacitor, and the switching loss as a whole. May not be reduced.

  A capacitor and a current limiting circuit are connected in series between the gate terminal of the voltage driven semiconductor element and the common line of the driving circuit of the voltage driven semiconductor element, and the collector current of the voltage driven semiconductor element is reduced by the current limiting circuit. The current is limited so that the current flowing through the capacitor decreases as the value increases.

  ADVANTAGE OF THE INVENTION According to this invention, the switching loss of a voltage drive type semiconductor element can be reduced, suppressing the radiation noise which generate | occur | produces from a voltage drive type semiconductor element.

  An embodiment in which an inductive load is driven using an IGBT which is a voltage-driven semiconductor element will be described.

  In addition to the collector terminal C, the emitter terminal E, and the gate terminal G, the IGBT (Q101) is provided with a sense terminal S connected to the emitter current detection cell. Between the collector terminal C and the emitter terminal E of the IGBT (Q101), an inductive load L101 and a DC power supply VB are connected in series, and the inductive load L101 has both ends for energy regeneration of the inductive load L101. Are connected in parallel. The emitter terminal E of the IGBT (Q101) is connected to the common line GNDC of the power circuit of the voltage driven semiconductor element.

  The push-pull connected NPN transistor Q103 and PNP transistor Q104 are input circuits for inputting an input signal Vin for driving the IGBT (Q101), and the input signal Vin for driving the IGBT is input to the base terminals of the transistors Q103 and Q104. Is done. The emitter terminal of the NPN transistor Q103 is connected to the gate terminal G of the IGBT (Q101) via the gate resistor Rgon, and the collector terminal of the PNP transistor Q104 is connected to the gate terminal G of the IGBT (Q101) via the gate resistor Rgoff. Connected to.

  A capacitor C101 and an Nch-MOSFET (Q102) are connected in series between the gate terminal G of the IGBT (Q101) and the common line of the drive circuit so as to be connected in parallel between the gate and emitter of the IGBT (Q101). Is done. The capacitor C101 is for reducing the rate of change dIc / dt of the collector current Ic when the IGBT (Q101) is turned on and suppressing the generation of radiation noise. The Nch-MOSFET (Q102) limits the charge / discharge current flowing to the capacitor C101 in the region where the collector current Ic of the IGBT (Q101) is large, and reduces the “tail” of the collector voltage Vce of the IGBT (Q101). This is to suppress loss.

  The sense terminal S provided for detecting the collector current Ic of the IGBT (Q101) is connected to the common line GNDC of the power circuit of the voltage driven semiconductor element via the sense resistor R101. One end of the sense resistor R101 is connected to a low pass filter (LP filter) composed of a resistor R102 and a capacitor C102, and the output of the low pass filter (LP filter) is connected to an input positive terminal of an operational amplifier I101 having a voltage follower configuration. Is done. The operational amplifier I101 performs impedance conversion.

  The output of the operational amplifier I101 is connected to the input of the inverting amplifier circuit 110. The inverting amplifier circuit 110 is composed of an operational amplifier I102 and gain adjusting resistors R103 and R104, and an offset voltage Vo is input to the input plus terminal of the operational amplifier I102 in order to offset the operating voltage. The output of the operational amplifier I102, that is, the output of the inverting amplifier circuit 110 is connected to the gate terminal of the Nch-MOSFET (Q102) for charge / discharge current control of the capacitor C101.

  FIG. 2 is a time chart showing operation waveforms of each part of the drive circuit shown in FIG. The operation of the embodiment will be described with reference to FIG. When the drive input signal Vin of the IGBT (Q101) changes from the low level to the high level, the NPN transistor Q103 is turned on, and a current flows from the power source Vcc to the gate terminal G of the IGBT (Q101) via the gate resistor Rgon. The gate voltage Vge of (Q101) increases. When the gate voltage Vge exceeds the threshold value of the IGBT (Q101), the IGBT (Q101) is turned on, and the collector current Ic flows from the power source VB through the inductive load L101.

  When the IGBT (Q101) is turned on and the collector current Ic flows, the sense current Is flows from the sense terminal S to the resistor R101 in accordance with the collector current Ic. The ratio of the sense current Is to the collector current Ic is determined in advance by the structure of the IGBT (Q101) that is a voltage-driven semiconductor element. A voltage generated across the resistor R101 by the sense current Is is input to the operational amplifier I101 through a low-pass filter (LP-filter). The impedance is converted by the operational amplifier I101 and then input to the inverting amplifier circuit 110. The inverting amplifier circuit 110 inverts the waveform with respect to the offset voltage Vo. The offset voltage Vo is adjusted to be the threshold value Vth of the Nch-MOSFET (Q102). The output of the inverting amplifier circuit 110 is input to the gate terminal of the Nch-MOSFET (Q102). As a result, the gate voltage of the Nch-MOSFET (Q102) decreases as the collector current Ic of the IGBT (Q101) increases.

  FIG. 3 shows the characteristics of the drain-source voltage Vds with respect to the drain current Id of the Nch-MOSFET (Q102). As is apparent from this characteristic, the drain current Id is limited and decreases as the gate voltage Vge of the Nch-MOSFET (Q102) decreases. Since the gate voltage of the Nch-MOSFET (Q102) decreases as the collector current Ic of the IGBT (Q101) increases, the current flowing through the capacitor C101 is suppressed by the Nch-MOSFET (Q102). As a result, the charge amount Q charged / discharged in the capacitor C101 decreases as the collector current Ic of the IGBT (Q101) increases.

  In FIG. 2, when the collector current Ic in the period 1 and the period 2 is compared with the charge amount Q of the capacitor C101, it can be seen that the charge amount Q of the capacitor C101 decreases as the collector current Ic increases. That is, when the collector current Ic of the IGBT (Q101) increases, the current flowing to the capacitor C101 decreases, and the state continuously transitions to an equivalent state as if the capacitor C101 is not connected. The maximum value Qmax of the charge amount Q of the capacitor C101 is a product of the capacitor C101 and the power source Vcc.

  FIG. 4 shows the amount of noise generated with respect to the IGBT collector current Ic when the voltage-driven semiconductor element drive circuit of one embodiment is used. In this embodiment, since the charge / discharge current flowing through the capacitor C101 is limited in the region where the collector current Ic is large, the noise suppression effect by the capacitor C101 is reduced, and the conventional drive circuit which does not use the Nch-MOSFET (Q102). Although the amount of radiation noise generated increases, it can still be sufficiently below the allowable (NG) level.

  FIG. 5 shows the switching loss Esw with respect to the IGBT collector current Ic when the voltage-driven semiconductor element drive circuit according to the embodiment is used. As the collector current Ic increases, the charging / discharging current flowing to the capacitor C101 is suppressed, and it is equivalent to the case where the capacitor C101 is not connected. Therefore, the “tail” of the collector voltage Vce of the IGBT (Q101) is small. Thus, the switching loss Esw is reduced.

  Next, the effect when the voltage-driven semiconductor element drive circuit of one embodiment is applied to an inverter will be described. FIG. 6 shows a power conversion circuit of a three-phase AC inverter. In FIG. 6, P is a positive DC bus, N is a negative DC bus, U is a U-phase AC output line, V is a V-phase AC output line, and W is a W-phase AC output line. In this inverter, an IGBT is used as a voltage-driven semiconductor element.

  7A shows the phase current flowing through the inverter AC output line of any of U, V, and W phases, that is, the collector current Ic of the IGBT, and FIG. 7B shows the switching loss Esw of the IGBT. In the region where the phase current, that is, the collector current Ic of the IGBT is large, this is equivalent to the state where the capacitor C101 is not present, and therefore the switching loss Esw is smaller than that of the conventional drive circuit.

  As described above, in one embodiment, the capacitor C101 and the Nch-MOSFET (Nch-MOSFET) are connected between the gate terminal G of the voltage driven semiconductor element IGBT (Q101) and the common line of the drive circuit of the voltage driven semiconductor element IGBT (Q101). Q102) are connected in series, and the current flowing through the capacitor C101 increases as the collector current of the voltage-driven semiconductor element IGBT (Q101) increases by the inverting amplifier circuit 110, the operational amplifier I101, the LP filters R102, C102, and the resistor R101. The current was limited so as to decrease. In a region where the collector current is large, where the generation of radiation noise is small, the current flowing through the capacitor can be limited to a small value, so that the charging time to the gate terminal G of the voltage-driven semiconductor element IGBT (Q101) increases, and the collector voltage at turn-on The switching loss can be reduced by reducing the Vce tail. On the other hand, in a region where the collector current where the generation of radiation noise increases is small, the amount of current flowing through the capacitor C101 can be increased, so that generation of radiation noise can be suppressed. That is, the electrical effect of the capacitor C101 continuously changes in accordance with the collector current of the voltage-driven semiconductor element IGBT (Q101), and the switching loss can be reduced while effectively suppressing the generation of radiation noise.

  The correspondence between the constituent elements of the claims and the constituent elements of the embodiment is as follows. That is, IGBT (Q101) is a voltage-driven semiconductor element, capacitor C101 is a capacitor, Nch-MOSFET (Q102), inverting amplifier circuit 110, operational amplifier I101, LP-filters R102 and C102, and resistor R101 are current limiting circuits. Nch-MOSFET (Q102) constitutes a current limiting semiconductor element, and inverting amplifier circuit 110, operational amplifier I101, LP-filters R102 and C102 and resistor R101 constitute a control circuit. In addition, as long as the characteristic function of this invention is not impaired, each component is not limited to the said structure.

  In the embodiment, the IGBT is used as the voltage-driven semiconductor element. However, the voltage-driven semiconductor element is not limited to the IGBT, and may be a power MOSFET, for example.

  In the embodiment described above, a voltage-driven semiconductor element (IGBT) having a sense terminal S that outputs a current at a predetermined ratio with respect to the collector current is used, and the output current from the sense terminal S increases. Although an example in which the current flowing through the capacitor C101 is limited to a small value has been shown, a current sensor that detects a collector current may be used for such a voltage-driven semiconductor element that does not include the sense terminal S.

  Furthermore, in the above-described embodiment, an example in which the Nch-MOSFET (Q102) is used as the current limiting circuit that limits the current flowing through the capacitor C101 has been shown. However, the element used in the current limiting circuit is not limited to the MOSFET. For example, a transistor may be used.

It is a figure which shows the structure of one embodiment. It is a time chart which shows the operation waveform of each part of the circuit of one embodiment. It is a figure which shows the characteristic of Nch-MOSFET. It is a figure which shows the relationship of the noise generation amount with respect to the collector current of IGBT. It is a figure which shows the relationship of the switching loss with respect to the collector current of IGBT. It is a figure which shows the power converter circuit of a three-phase alternating current inverter. It is a figure which shows the collector current (a) and switching loss (b) of IGBT with respect to the phase current of a three-phase alternating current inverter.

Explanation of symbols

Q101 Voltage-driven semiconductor device (IGBT)
Q102 Nch-MOSFET
Q103, Q104 Transistor L101 Load D101 Diode C101, C102 Capacitors R101, R102, R103, R104, Rgon, Rgoff Resistor I101, I102 Operational amplifier VB Power supply 110 Inverting amplifier circuit GNDC Common line of device

Claims (4)

A drive circuit for a voltage-driven semiconductor element in which a capacitor and a current limiting circuit are connected in series between a gate terminal of the voltage-driven semiconductor element and a common line of the drive circuit for the voltage-driven semiconductor element,
The drive circuit for a voltage-driven semiconductor element, wherein the current limiting circuit limits the current so that the current flowing through the capacitor decreases as the collector current of the voltage-driven semiconductor element increases. The drive circuit of the voltage drive type semiconductor device according to claim 1,
The voltage-driven semiconductor element includes a sense terminal that outputs a current at a predetermined ratio with respect to a collector current,
The drive circuit for a voltage-driven semiconductor element, wherein the current limiting circuit limits a current flowing through the capacitor based on an output current from the sense terminal. In the drive circuit of the voltage drive type semiconductor element according to claim 1 or 2,
The current limiting circuit includes a current limiting semiconductor element connected in series with the capacitor, and a control circuit that reduces the current conduction rate of the current limiting semiconductor element as the collector current of the voltage-driven semiconductor element increases. A drive circuit for a voltage-driven semiconductor element, comprising: In the drive circuit of the voltage drive type semiconductor device according to claim 3,
An N-channel MOSFET is used for the current limiting semiconductor element, and the drain terminal is connected to the capacitor and the source terminal is connected to the common line. The control circuit increases the collector current of the voltage-driven semiconductor element. The drive circuit of the voltage drive type semiconductor device, wherein the input voltage to the gate terminal of the N-channel type MOSFET is reduced as it goes.

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