CN103825434A - Driving circuit for insulated gate bipolar translator (IGBT) - Google Patents

Abstract

The invention relates to the technology of an integrated electronic circuit, and particularly relates to a gate driving circuit for an insulated gate bipolar translator (IGBT). The driving circuit for the IGBT comprises an optical coupler 1, a switching circuit 2 and a driving protection circuit 3, wherein the optical coupler 1 is respectively connected with the switching circuit 2 and the driving protection circuit 3; the switching circuit 2 is connected with the driving protection circuit 3. On-off of the optical coupler 1 and the driving circuit is controlled by the switching circuit 2 so as to realize overcurrent protection of the IGBT. As electronic devices are not arranged on the network for controlling IGBT in the circuit, the reliability of the circuit is greatly enhanced. The driving circuit has the beneficial effects that the complexity of the circuit is effectively lowered, and the reliability and stability of the circuit are enhanced. The invention is particularly suitable for the driving circuit for IGBT.

Description

A kind of IGBT driving circuit

technical field

The invention relates to integrated electronic circuit technology, in particular to a gate drive circuit for IGBT.

Background technique

With the rapid development of power electronic technology, IGBT is widely used in various power electronic systems because of its characteristics of easy to be driven, strong current capacity, high withstand voltage, fast speed and low saturation voltage drop. Such as frequency conversion power supply, welding machine, switching power supply, etc.

Although IGBT has superior performance, it still needs an external circuit to drive and protect it. Due to the large power required to drive the IGBT, ordinary drive circuits cannot complete its drive. Therefore, it is necessary to design a circuit that specifically drives the IGBT module. The performance and reliability of the IGBT drive circuit directly affect the performance and reliability of the circuit system. Therefore, it is very important to design a high-performance, safe and reliable IGBT drive circuit.

Generally speaking, the driving methods of IGBT are mainly divided into two types, one is direct drive and the other is isolated drive. Since IGBTs usually work in high voltage and high current situations. The driving IGBT is mainly realized by PWM (Pulse Width Modulation). The PWM generation system is a weak signal system. In order to be safe and reduce the interference of the high-voltage part of the circuit to the weak signal circuit, electrical isolation is required between the two. Therefore, the isolated drive exhibits higher reliability.

At present, the common IGBT overcurrent protection network usually realizes the soft turn-off of the IGBT by designing the charging delay of the resistor and the capacitor. In this way, the circuit needs to accurately design the values of the capacitor and the resistor to obtain an appropriate off time, which makes the circuit structure more complicated.

Contents of the invention

What the present invention aims to solve is to propose an IGBT drive circuit with simple structure and reliable performance, aiming at the problem of complicated structure of the current IGBT drive circuit.

The technical solution adopted by the present invention to solve the above-mentioned technical problems is: as shown in Figure 1, a kind of IGBT driving circuit comprises optocoupler 1, switch circuit 2 and drive protection circuit 3, and described optocoupler 1 is connected with switch circuit respectively 2 is connected to the drive protection circuit 3, and the switch circuit 2 is connected to the drive protection circuit 3; the switch circuit 2 includes resistors R21, R23, and an NMOS transistor MN22; the drive protection circuit 3 includes a PMOS transistor MP301, an NMOS transistor MN302, Transistor NPN32, resistors R31, R34, R36, R38, R303, R306, diodes D35, D37, D304, capacitors C33, C39, C305; among them,

One end of R21, one end of R31, one end of R34, one end of R38, one end of R306, the positive pole of D37, the source and substrate of MP301 are all connected to the power supply VDD;

The other end of R21 is respectively connected to the gate of MN32 and the collector of NPN32, the source and substrate of MN32 are connected to the collector of the subsequent stage of optocoupler 1, the drain of MN32 is connected to one end of R23, and the other end of R23 Connect to the other end of R31, the gate of MP301, and one end of gate C33 of MN302;

The other end of R34 is connected to the negative pole of D35 and one end of R36, the positive pole of D35 is connected to the base set of NPN32, and the other end of R36 is connected to the other end of R38 and one end of C39;

After the drain of MP301 is connected to the drain of MN302, it is connected to the gate of IGBT through R303, the collector of IGBT is connected to the negative pole of D37, the emitter of IGBT is connected to the other end of R306, one end of C305, the negative pole of D304, optical coupling The cathode connection of the rear stage of device 1;

The emitter of the subsequent stage of the optocoupler 1, the other end of C33, the emitter of NPN32, the other end of C39, the source and substrate of MN302, the positive pole of D304, and the other end of C305 are all grounded to GND.

Specifically, the drive protection circuit 3 also includes an NMOS transistor MN40, the drain of MN40 is connected to the power supply VDD, the gate is connected to the drain of MP301 and the drain of MN302, the source and the substrate are connected to the other end of R31 and the gate of MP301 Connect to the gate of MN302.

The invention has the beneficial effects of effectively reducing the complexity of the circuit and improving the reliability and stability of the circuit.

Description of drawings

Fig. 1 is the schematic diagram of the IGBT driving circuit of embodiment 1;

Fig. 2 is the schematic diagram of the IGBT drive circuit of embodiment 2;

Fig. 3 is the simulation schematic diagram of the IGBT drive circuit of embodiment 1;

FIG. 4 is a schematic diagram of the simulation of the IGBT driving circuit of the second embodiment.

Detailed ways

Below in conjunction with accompanying drawing and embodiment, describe technical solution of the present invention in detail:

The IGBT driving circuit of the present invention mainly drives the gate of the IGBT through the inverter, and controls the on-off of the optocoupler and the driving circuit by utilizing the characteristic that the saturation voltage rises when the IGBT is short-circuited, so as to realize the overcurrent protection of the IGBT . The electrical isolation between the IGBT and the pre-stage weak signal system is realized through the optocoupler. By switching the MOS tube to control the on-off of the optocoupler and the drive circuit, the overcurrent protection of the IGBT is realized. Since there are no electronic components on the network controlling the IGBT in the circuit, its reliability is greatly enhanced.

Example 1:

As shown in Figure 1, this example includes an optocoupler 1, a switch circuit 2 and a drive protection circuit 3, the optocoupler 1 is connected to the switch circuit 2 and the drive protection circuit 3 respectively, and the switch circuit 2 and the drive protection circuit 3 connection; the switch circuit 2 includes resistors R21, R23, NMOS transistor MN22; the drive protection circuit 3 includes PMOS transistor MP301, NMOS transistor MN302, triode NPN32, resistors R31, R34, R36, R38, R303, R306, diode D35, D37, D304, capacitors C33, C39, C305, wherein the model of the optocoupler 1 is TLP550. Pins 1, 4, and 7 of the TLP550 are unconnected pins, pins 2 and 3 are the front stage of the optocoupler TLP550, pin 2 is the anode, and pin 3 is the cathode of the front stage ; Pin 5, pin 6, and pin 8 are the rear stage of the optocoupler TLP550, pin 5 is the emitter, pin 6 is the collector, and pin 8 is the cathode of the rear stage.

One end of R21, one end of R31, one end of R34, one end of R38, one end of R306, the positive pole of D37, the source and substrate of MP301 are all connected to the power supply VDD;

The other end of R21 is connected to the gate of MN32 and the collector of NPN32, the source and substrate of MN32 are connected to an input end of optocoupler 1, the drain of MN32 is connected to one end of R23, and the other end of R23 is respectively Connect with the other end of R31, the gate of MP301, and one end of gate C33 of MN302;

The other end of R34 is connected to the negative pole of D35 and one end of R36, the positive pole of D35 is connected to the base set of NPN32, and the other end of R36 is connected to the other end of R38 and one end of C39;

After the drain of MP301 is connected to the drain of MN302, it is connected to the gate of IGBT through R303, the collector of IGBT is connected to the negative pole of D37, the emitter of IGBT is connected to the other end of R306, one end of C305, the negative pole of D304, optical coupling One output terminal of device 1 is connected;

The other output end of pin 5 of optocoupler 1, the other end of C33, the emitter of NPN32, the other end of C39, the source and substrate of MN302, the positive pole of D304, and the other end of C305 are all grounded to GND.

This example works as follows:

IGBT conduction: when a control signal appears on pins 2 and 3 of optocoupler 1. At this time, the optocoupler will be turned on, and the potential of point A will be pulled down rapidly. At this time, the inverter MP301 is turned on, and the inverter MN302 is turned off, and a voltage of 20V will be induced on the gate electrode of the IGBT at this time. Since D304 will stabilize the emitter potential of the IGBT at about 5V, the gate voltage of the IGBT is actually 15V. That is, the IGBT is turned on.

Turn off the IGBT: When the control signal on pins 2 and 3 of the optocoupler 1 disappears, the potential at point A will be quickly charged to a high potential, the inverter MP301 is turned off, and the inverter MN302 is turned on, making the IGBT The gate is directly connected to GND. Also because D304 will stabilize the emitter potential of the IGBT at about 5V, the gate voltage of the IGBT is actually -5V at this time. From this point of view, the IGBT can be turned off reliably.

As shown in Figure 3, it is the simulation schematic diagram of this example. From the simulation results, it can be seen that the circuit can provide stable voltages of 20V and 0V for the gate of the IGBT, so as to control the switching of the IGBT.

IGBT overcurrent protection: When the IGBT is in the open state, the potentials of points B and C are stable at about 9V. If a short circuit occurs at a certain moment, the overcurrent protection circuit will be triggered. The way to judge whether the IGBT is short-circuited is that when the IGBT is short-circuited, its saturation voltage will rise accordingly. When the saturation voltage drop of the IGBT rises to the point where the blocking D37 is cut off, the line where R34 is located is "floating", and the potentials at points B and C will rapidly rise to the breakdown voltage of the breakdown D35 (about 13V). At this time, breakdown occurs in D35, and NPN32 is turned on. At this time, the gate potential of the switch MN22 will rapidly drop to 0 potential, and the switch MN22 is turned off. Since the switch MN22 is turned off, the optocoupler is completely isolated from the internal driving circuit. Therefore, the potential at point A will gradually increase with the charging and discharging time constants of driving R31 and C33, gradually turning off the inverter MP301 and turning on the inverter MN302. In this way, the soft turn-off of the IGBT is realized.

Example 2:

As shown in Figure 2, the main difference from Embodiment 1 is that the feedback MN40 is added in this example, and the connection method is to connect the gate of the feedback MN40 to the output terminal of the inverter (that is, the drain of the inverter MP301) , its drain is connected to VDD, its source is connected to the substrate and then connected to the input terminal of the inverter (that is, the gate of the inverter MP301).

Its specific implementation is basically the same as the first specific implementation, except that the newly added feedback MN40 will be turned on for a period of time when the high level changes to low level to assist in raising the potential of point A. Thereby accelerating the decline of the output potential to achieve the purpose of making the falling edge of the output waveform steeper.

In order to illustrate the impact of the feedback MN40 on the falling edge of the circuit output waveform, we simulated the circuit structure with the feedback MN40. As shown in Figure 4, comparing the waveform at the output terminal of the inverter in Figure 4 with that in Figure 3, it can be found that the falling edge of the waveform is indeed steeper when there is a feedback MN40.

To sum up, the present invention proposes a novel IGBT driving circuit. This circuit can drive the IGBT by isolating the optocoupler sensing control signal and directly controlling the high and low potential output of the inverter. Since there are no other electronic components involved in the control circuit, the reliability is greatly enhanced. In terms of overcurrent protection, the new circuit uses a switch MOS tube to control the on-off between the optocoupler and the drive circuit, and the switch MOS tube is only disconnected when the IGBT is short-circuited, so it can be turned off reliably when the IGBT is short-circuited .

Claims (2)

1. An IGBT drive circuit, characterized in that it includes an optocoupler (1), a switch circuit (2) and a drive protection circuit (3), and the optocoupler (1) is connected with the switch circuit (2) and the drive The protection circuit (3) is connected, and the switch circuit (2) is connected to the drive protection circuit (3); the switch circuit (2) includes resistors R21, R23, and NMOS tube MN22; the drive protection circuit (3) includes a PMOS Tube MP301, NMOS tube MN302, triode NPN32, resistors R31, R34, R36, R38, R303, R306, diodes D35, D37, D304, capacitors C33, C39, C305; among them, One end of R21, one end of R31, one end of R34, one end of R38, one end of R306, the positive pole of D37, the source and substrate of MP301 are all connected to the power supply VDD; The other end of R21 is respectively connected to the gate of MN32 and the collector of NPN32, the source and substrate of MN32 are connected to the collector of the subsequent stage of the optocoupler (1), the drain of MN32 is connected to one end of R23, and the The other end is respectively connected with the other end of R31, the grid of MP301, and one end of the grid C33 of MN302; The other end of R34 is connected to the negative pole of D35 and one end of R36, the positive pole of D35 is connected to the base set of NPN32, and the other end of R36 is connected to the other end of R38 and one end of C39; After the drain of MP301 is connected to the drain of MN302, it is connected to the gate of IGBT through R303, the collector of IGBT is connected to the negative pole of D37, the emitter of IGBT is connected to the other end of R306, one end of C305, the negative pole of D304, optical coupling The cathode connection of the rear stage of the device (1); The emitter of the subsequent stage of the optocoupler (1), the other end of C33, the emitter of NPN32, the other end of C39, the source and substrate of MN302, the positive pole of D304, and the other end of C305 are all grounded to GND. 2. An IGBT drive circuit according to claim 1, characterized in that the drive protection circuit (3) also includes an NMOS transistor MN40, the drain of MN40 is connected to the power supply VDD, the gate is connected to the drain of MP301 and the drain of MN302 The pole connection, the source and the substrate are connected with the other end of R31 and the gate of MP301 and the gate of MN302.

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