JPH02280659A - Drive output circuit for switching semiconductor device - Google Patents

Abstract

PURPOSE:To realize a low loss drive circuit by inserting a diode having polarity for feeding collector current in series with the collector circuit of a transistor Tr at non-output stage side in two Darlington connection transistors Tr. CONSTITUTION:Two npn Tr 1A, 2A are Darlington connected in a drive output circuit 01A, and a diode 3 is inserted in forward direction into the collector circuit of the Tr 1A at the prestage (non-output stage) side. Base current IB of the drive output circuit 01A flows through the base B of Tr 1A - emitter E thereof - base B of Tr 2A-emitter E thereof. Within the range of low collector current IC, only the Tr 2A functions as a single Tr in the drive output circuit 01A resulting in a low collector-emitter voltage VCE 2 of the Tr 2A. Within the range of high collector current IC, the drive output circuit 01A functions as a Darlington Tr including the Tr 1A.

Description

[Detailed description of the invention] [Industrial application field]

The present invention is directed to a common semiconductor device for driving different types of switching semiconductor devices (hereinafter also referred to as power devices) having different drive input characteristics, each of which is mainly composed of bipolar transistors, IGBTs as insulated gate transistors, MOSFETs, etc. The present invention relates to a drive output circuit, and particularly to a drive output circuit for a switching semiconductor device that can be integrated into an IC. In the following figures, the same reference numerals indicate the same or corresponding parts, and also indicate logic or levels "High" and "L".
ow" is simply written as 1lH11,llL".

[Conventional technology]

Conventionally, drive circuits for power devices are generally used for each device depending on the drive input characteristics (also simply referred to as input characteristics) unique to each power device. Fig. 4 shows an example of the drive input characteristics of different types of power devices, and Fig. 4 (A) shows an example of the waveform of the base-emitter voltage VBE of a bipolar transistor and the corresponding base current IB. (B) is the IGBT gate.
Emitter voltage VGE and corresponding gate current IG
Examples of waveforms are shown below. Further, FIG. 5 shows an example of a bipolar transistor drive circuit, and FIG. 6 shows an example of an IGBT drive circuit. In Fig. 5, QB is a bipolar transistor as a power device to be driven, vCC is a forward driving DC power supply, VER is a reverse driving DC power supply, cp is an output stage transistor for forward driving, and QR is a forward driving DC power supply. This is an output stage transistor for reverse direction driving. Now, if the drive signal VD is set to "H", this signal VD becomes N
It is inverted via the OT element N1 to turn on the photocoupler PCI and turn off the other photocoupler PC2. As a result, the DC amount is 1vcc → the phototransistor PTI of the photocoupler PCI → the base and emitter of the output stage transistor QF →
Base current is supplied to the output stage transistor QF for forward drive through the base-emitter of bipolar transistor QB → DC power supply ■cc path, this output stage transistor QF is turned on, and the other reverse output stage transistor QR is turned off. do. Therefore, in the path of DC power supply VCC → forward base current limiting resistor RF → collector/emitter of output stage transistor QF → base/emitter of bipolar transistor QB → DC power supply ■CC, bipolar transistor Q
A base current 181 as a forward drive current is supplied to B, and this bipolar transistor QB is turned on. Next, when the drive signal 7 port is set to “L”, the photocoupler PCI
is turned off and PO2 is turned on. As a result, the output stage transistor QF in the forward direction is turned off, and a new DC power supply VEE→
Emitter/base of bipolar transistor QB → emitter/base of output stage transistor QR → photocoupler P
A base current is supplied to the output stage transistor QR for reverse drive through the path from the phototransistor PT2 of C2 to the DC power supply VEE, and this output stage transistor is turned on. Therefore, DC power supply VEE → emitter/base of bipolar transistor QB → emitter/collector of output stage transistor QR → reverse base current limiting resistor RR → DC power supply VE
A base current IB2 as a reverse drive current is supplied to the bipolar transistor QB through the path E, and the bipolar transistor QB is turned off. Further, in FIG. 6, when the drive signal VD is set to "H", the photocoupler PCO is turned on and the auxiliary transistor QIO is turned off. As a result, the reverse output stage transistor QR is turned off, and the base is connected to the forward output stage transistor QP via the route of DC power supply ■CC → resistor R2 → base/emitter of output stage transistor QF → gate/emitter of IGBTQI → DC power supply ■CC. When current is supplied, this forward output stage transistor QF is turned on. Therefore, a forward drive voltage is applied between the gate and emitter of ICBTQI from the DC power supply vCC via the resistor RF, and I GBTQl is turned on. Next, when the drive signal VD is set to “L”, the photocoupler PCO
is turned off and auxiliary transistor QIO is turned on. As a result, the forward output stage transistor QF is turned off, and the reverse output stage transistor QR is newly connected to the DC power supply VEE → the emitter gate of IGBT QI → the emitter base of the output stage transistor QR → the auxiliary transistor QIO → the DC power supply VEE. When the base current is supplied, this reverse output stage transistor QR is turned on. This allows IGB
A reverse drive voltage is applied between the gate and emitter of TQl from DC power supply VEE via resistor RR, and ICBT
QI turns off. Returning to Figure 4 again, as shown in Figure 4 (A), a bipolar transistor is a current-driven element, and in order to maintain conduction, a base current commensurate with its collector current must be constantly supplied. No. Furthermore, when turning off a conductive element, a reverse bias base current greater than the forward bias base current value is supplied to the base to shorten the turn-off time. The above forward bias base current value can be reduced by connecting the bipolar transistors Qll in multiple stages (three stages in this example) in Darlington as shown in FIG. It is difficult to reduce this because it is necessary to set the value according to the rating of the final stage transistor Q3 (FIG. 7) of the bipolar transistors. Therefore, the base current of the bipolar transistor becomes as indicated by IB in FIG. 4(A) (an example of a three-stage Darlington transistor). Note that after t=tl in the same figure (A), the base-emitter junction of the final stage transistor Q3 (Fig. 7) is restored, and the reverse bias base current is connected in parallel between the base and emitter of the final stage transistor Q3. resistance R
BE (FIG. 7). In this case, the base current value is extremely small (for example, 50 mA). To ensure that the transistor remains off during this period,
It is desirable that a reverse bias voltage of around 1V be applied between the base and emitter of the final stage transistor Q3. On the other hand, as shown in FIG. 4(B), the IGBT is a voltage-driven element, and in order to make the on-voltage a sufficiently low value, it is effective to increase the gate voltage as much as possible within the allowable range. Turn-off is achieved by applying a negative voltage between the gate and emitter to discharge the charge accumulated in the input capacitance. Therefore, (the drive voltage of the GBT is V in the same figure (B)
GH, and since the gate of the IGBT is equivalent to a capacitive load from the driver circuit side, the gate current IG becomes a charging/discharging current of the input capacitance via the gate series resistor, as shown in the figure. The absolute values of the positive and negative peak values of the gate current IG are equal, and the conduction period can be considered as a time constant determined by the gate series resistance value and the input capacitance, and is a short time of 1 μsec or less. Therefore, when used at a switching frequency of 20 KHz or less, the heat generated by the output stage transistors QF and QR of the drive circuit hardly becomes a problem. As is clear from FIGS. 5 and 6, there is no major difference in the basic configuration of the output stage transistors QF and QR of the drive circuit.
The difference in the drive circuit depending on the type of driven power devices QB, Q1, etc. is the configuration of the output stage transistors QF, QR (Darlington configuration or single configuration) and the generated loss. For example, if we consider driving a 50A class bipolar transistor (three-stage Darlington) QB and IGBTQI, the respective drive currents are as shown in FIG. Considering the commonality of the drive output circuit, the maximum collector current of the transistor for forward drive current supply (Fig. 5; QF in Fig. 6) is determined from the IGBT driving condition (0.8 A in this example). The loss generated by this supply transistor QF is the drive output current (5 in this example) when driving the bipolar transistor QB.
0mA) and the supply transistor QF at that output state.
It is determined by the saturation voltage of In addition, a transistor for sinking reverse current of the driven power device (Q
The maximum collector current of R) is determined by the maximum value of the reverse bias current of the bipolar transistor (-IA in this example),
Moreover, the loss generated by this suction transistor QR is the same as the loss caused by the base loss during reverse biasing of the bipolar transistor QB.
It is determined by the reverse bias (base) current including the current flowing through the emitter-to-emitter parallel resistor RBB (FIG. 7) and the saturation voltage when this minute current is passed as its own collector current. However, the saturation voltage of the sinking transistor QR when the collector current is small is limited by the relationship with the voltage value VEIE of the DC iit source VEH for supplying the reverse bias current of the bipolar transistor. FIG. 7 is an explanatory diagram of this reverse bias voltage, and FIG.
The circuit connection for reverse biasing with the reverse current sinking transistor QRI, which is a step-darlington-connected reverse-direction driving transistor, is shown, and FIG. Now, after the base-emitter junction of the final stage transistor Q3 of the bipolar transistor QB has been restored, 1
In order to apply a reverse voltage VBE of approximately V, it is necessary to satisfy the following equation (1). VBE= VCE+ VF(SUDI)+VF(S
[ID2) -VEE=-1(ν)...-(1) Here, VCE is the collector-emitter voltage of the output stage side transistor 2B in the suction transistor QRI, and VF
(SIJDI) and V F (StlD2) are forward voltage drops of diodes 5UDI and 5UD2 connected in antiparallel between the respective bases and emitters of the two preceding transistors Ql and Q2 constituting the bipolar transistor QB, respectively. As can be seen from the above equation (1), the higher the saturation voltage VCE of the current sinking transistor QRI in the drive circuit, the higher the value of VEE is required. Furthermore, the higher the saturation voltage VCE, the greater the loss of one member generated in this mode.

[Problems to be Solved by the Invention] Generally, as described above, drive circuits for power devices are used depending on the type of power device used. The purpose of making these common in the present invention is to realize a drive control IC that can be used with various power devices. Since drive circuits for power devices handle relatively large currents, losses generated inside the IC (power loss) become a problem when integrated into an IC. As mentioned above, one drive circuit consists of bipolar transistors and IGBTs.
In order to be usable in both cases, the transistor in the output stage of the drive circuit must be able to supply a large current with a peak value for a short time and a small current for a long time, with the same base current flowing. It is necessary to have the ability to generate little heat even when supplied. Therefore, this output stage transistor must have a low saturation voltage in a range where the drive output current value is small. However, in order to satisfy the former requirement, the drive output stage transistor must have a Darlington configuration, but in this case, the saturation voltage increases overall, resulting in an increase in power loss. Therefore, the present invention replaces the drive output circuit (that is, the output stage circuit of the drive circuit) corresponding to the output stage transistor for driving a power device with a two-stage Darlington connected transistor.
Furthermore, it is an object of the present invention to solve the above-mentioned problem by inserting a diode in the forward direction in the collector circuit of the transistor on the front stage (non-output stage) side in this Darlington connection. [Means for Solving the Problems] In order to solve the above-mentioned problems, the circuit of the present invention solves the problems described above.
bipolar transistor QB, IGBTQI, etc.)
A common drive output circuit for driving the switching semiconductor device, which opens and closes a DC power supply (VCC, VEE, etc.) via two Darlington-connected transistors (1, 2, etc.) to drive the switching semiconductor device. In a drive output circuit (OIA, OIB, etc.) that applies voltage between the two transistors (base-emitter, gate-emitter, etc.), the transistor is connected in series to the collector circuit of the non-output stage transistor (1, etc.) of the two transistors. , a diode (such as 3) with a polarity that conducts the collector current is inserted.

[For use]

By configuring the drive output circuit of the power device by connecting the Darlington in series to the collector of the transistor on the previous stage (non-output stage) side of the two-stage Darlington-connected transistor, the composite transistor as the drive output circuit can be connected to the transistor in the previous stage (non-output stage). While the same base current is supplied to the side transistors, in the range where the collector current is small, it operates as a single transistor, keeping the collector-emitter voltage at a low value to reduce power loss, and on the other hand, in the range where the collector current is large. In this case, it operates as a Darlington transistor and can supply a large drive current to the power device while supplying a small base current to the front-stage transistor.

【Example】

The present invention will be described in detail below with reference to FIGS. 1 to 3. FIG. 1 shows the configuration of a drive output circuit of the present invention (a circuit corresponding to the output stage transistors QP and QR in FIGS. 5 and 6), and FIG. 2 shows an example of the characteristics of this drive output circuit. First, OIA is a drive output circuit with an npn transistor configuration, and OIB is a drive output circuit with a pnp transistor configuration. That is, in the drive output circuit 01A, two npn transistors IA and 2A are connected in Darlington, and the transistor 1^ on the previous stage (non-output stage) side
A diode 3 is inserted in the collector circuit in the forward direction. Similarly, in the drive output circuit 01B, two pnp transistors IB and 2B are connected in Darlington, and a diode 3 is inserted in the forward direction into the collector circuit of the transistor IB on the preceding stage. Here, for convenience, the transistor IAIB on the front stage (non-output stage) side is replaced by the first transistor 1. Transistors 2A and 2B on the rear stage (output stage) side
It is also called transistor 2. Next, the operation of this drive output circuit will be explained using OIA as an example. Letting the base current of this drive output circuit 014 be IB, IB flows from the base B of the first transistor 1A to the emitter E of the first transistor 1A to the base B of the second transistor 2 and then to the emitter E of the first transistor 1A. Here, if there is no diode 3, a part of 1B is the base B of the first transistor IA →
Collector C→Collector C- of the second transistor 2A
As a result, the collector-emitter voltage VCE(2) of the second transistor 2A is
A potential relationship as shown in the following equation (2) occurs with the transistor 18, and as a result, VCE(2) becomes high. V CE (2) = V BE (2) + V BE (1
) -V BC(1) -1---(2) However, VB
E(2) and VBE(1) are each transistor 2
A, indicates the base-emitter voltage of IA, and MBC (1
) indicates the voltage between the base and collector of the transistor 140. However, in the present invention, as mentioned above, by inserting the diode 3, this potential relationship does not occur.
As a result, in the range of low collector current IC where the first transistor 18 does not need to function as a transistor, only the second transistor 2^ operates as a single transistor in the drive output circuit 01A, and as a result, VCE(2
) can be set to a low value. On the other hand, in a range where the collector current IC is large, the drive output circuit 01A functions as a Darlington transistor including the first transistor 18. The explanation above applies to the drive output circuit 01B as well. In this way, the output characteristics of the drive output circuits 01A and OIB, that is, the relationship between the collector current IC and the collector-emitter voltage VCE(2), become as shown in FIG. The output characteristics of transistor 2 (dashed line) and the first. It operates on the lower characteristic of VCE (2) and the output characteristic of the transistor in which 28 is connected to the second transistor l by Darlington (--dotted chain line). Therefore, the output characteristics of the drive output circuits 01A and OIB are as shown by the solid lines in the figure. Figure 3 shows the drive output stage transistors QF and QI in Figure 6.
? Instead, drive output circuits 01A and OI in FIG.
The configuration of a drive circuit using B is shown, and the basic parts of this circuit can be used in common to drive power devices such as IGBTQI and bipolar transistor QB.

[Effects of the Invention] According to the present invention, the drive output circuit of a power device can be configured by using two-stage Darlington-connected transistors and further inserting a diode in the forward direction into the collector circuit of the previous-stage transistor in this transistor. Therefore, it is possible to realize a low-loss drive circuit that can be applied to both power devices such as a bipolar transistor IGBT and a MOSFET not mentioned here. By achieving low loss in this drive circuit, it has become possible to use C, which makes it possible to further downsize power device application circuits.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a power device drive output circuit as an embodiment of the present invention, FIG. 2 is a diagram showing an example of the output characteristics of the circuit in FIG. 1, and FIG. 3 is a diagram showing an example of the output characteristics of the circuit in FIG. 4 is a diagram showing an example of the drive input characteristics of a bipolar transistor and an IGBT. FIG. 5 is a diagram showing an example of the configuration of a bipolar transistor drive circuit. The figure shows an example of the configuration of an I GET drive circuit.
The figure is an explanatory diagram of the reverse bias voltage of a bipolar transistor, and FIG. 8 is a diagram showing an example of the drive current of a power device. 014, OIB: Drive output circuit, 1 (LA, 1B)
: first transistor, 2 (2A, 2B): second transistor, : diode. /-

Claims (1)

[Claims] 1) A common drive output circuit for driving different types of switching semiconductor devices having different drive input characteristics, the circuit comprising: In the drive output circuit applied between the drive input terminals of the switching semiconductor device, a diode with a polarity that conducts the collector current is inserted in series with the collector circuit of the transistor on the non-output stage side of the two transistors. Features a drive output circuit for switching semiconductor devices.