CN106505839A - IGBT device drive circuit and method for reducing turn-off loss - Google Patents

Abstract

The invention discloses a kind of IGBT device drive circuit for reducing switching loss and method, including detection module, electric current drive module, comparison module and Logic control module；The input of Logic control module is used for connecting the pulse-width signal of outside and digit order number selects signal, the feedback end of Logic control module connects the output end of comparison module, the input of electric current drive module is connected to the output end of Logic control module, the output end of electric current drive module is used for the control end for connecting IGBT device, the input of detection module is used for the output end for being connected to IGBT device, and the output end of detection module is connected to the input of comparison module.The present invention can reduce the switch-off power loss of IGBT device, avoid because caused by shut-off, Current Voltage overshoot burns device, simultaneously can be with the output voltage of precise control drive circuit and electric current, accelerate turn-off speed while IGBT shut-off overshoot voltages are not increased, signal delay is less, it is ensured that the backfeed loop normal work of IGBT device drive module within the of short duration turn-off time.

Description

IGBT device drive circuit and method for reducing turn-off loss

technical field

The invention belongs to the field of power electronics, and more specifically relates to an IGBT device drive circuit that reduces turn-off loss.

Background technique

IGBT (Insulated Gate Bipolar Transistor, insulated gate bipolar transistor) is a device composed of MOSFET (insulated gate field effect transistor, input stage) and BJT transistor (bipolar transistor, output stage). MOSFET devices have the characteristics of low driving power and fast switching speed (control and response), and bipolar devices have the characteristics of low saturation voltage and large capacity (power level is more durable), and the frequency characteristics are between MOSFETs and power transistors. Normally working in the frequency range of tens of kHz, it is the leading device of small and medium power power electronic equipment, and is widely used in inverters, lighting circuits, switching power supplies and other fields.

The IGBT driver is an intermediate circuit located between the main circuit and the control circuit and used to process the signal of the control circuit. Its input terminal is connected to the control signal of the control circuit, and its output terminal is connected to the IGBT gate. The isolation transmission, level adjustment and power amplification of the control signal are realized through a series of built-in circuits, so that the control circuit can control the turn-on and turn-off of the IGBT, and then realize various functions of the circuit.

The drive circuit is a bridge connecting the control circuit and the IGBT device. Since the IGBT is mostly used in high-voltage applications, sufficient input and output electrical isolation capabilities are required, so the drive circuit should be strictly isolated from the entire control circuit in terms of potential. In addition, the IGBT drive circuit is also closely related to the reliability of the IGBT. A high-quality IGBT drive circuit can optimize the IGBT switching characteristics, reduce turn-off time and loss, and improve system efficiency. The conventional IGBT open-loop drive circuit controls the gate drive current Ig by changing the gate resistance Rg: when Rg is small, the gate current is large, and the turn-off speed of the IGBT device is faster at this time, but due to the existence of parasitic inductance , a large voltage overshoot will occur on the DC bus, which may cause damage to the device in severe cases. When Rg is larger, the gate current is smaller, and the turn-off speed of the IGBT device is slower at this time, and the turn-off time is longer. According to the waveform diagram of the IGBT turn-off period, it can be seen that the voltage and current overlap on the IGBT device The time also increases accordingly, which will lead to large turn-off loss and electromagnetic interference (EMI), increase the overall power consumption of the system, and cause adverse effects such as heat generation.

Contents of the invention

Aiming at the defects of the prior art, the purpose of the present invention is to provide an IGBT device drive circuit with reduced turn-off loss, aiming to solve the problems of large turn-off loss and electromagnetic interference when the IGBT is turned off in the prior art.

The invention provides an IGBT device drive circuit that reduces switching loss, including: a detection module, a current drive module, a comparison module and a logic control module; the input end of the logic control module is used to connect external pulse width modulation signals and digital Bit selection signal, the feedback terminal of the logic control module is connected to the output terminal of the comparison module, the input terminal of the current drive module is connected to the output terminal of the logic control module, and the output terminal of the current drive module is used for The control terminal of the IGBT device is connected, the input terminal of the detection module is used to be connected to the output terminal of the IGBT device, and the output terminal of the detection module is connected to the input terminal of the comparison module.

Among them, when working, the logic control module accesses the pulse width modulation signal from the outside to control the switch of the current drive module, and then controls the opening and closing of the IGBT device; through the detection module, the voltage differential value during the IGBT turn-off process is sampled in real time, and by comparison The module compares the collected voltage with the preset reference voltage, and outputs the control signal to the logic control module; the logic control module can input the digital bit selection signal at the same time, and the two signals are processed by the logic control module to jointly control the working state of the current drive module ; The current drive module provides a controllable drive current during the IGBT turn-off process according to the output of the logic control module.

The invention compares the voltage differential value signal with the reference value by sampling the voltage differential value signal, and then controls the number of opening and closing of the current drive module, which can be used to reduce the power loss of the IGBT device when it is turned off, and avoid burning the device due to current and voltage overshoot caused by the shutdown. The difference between the conventional open-loop mode IGBT drive scheme is that this scheme uses the voltage differential value as the feedback value to ensure the low delay of the overall feedback loop (<20ns), realize the closed-loop control of the gate drive, and accurately control the output voltage of the drive circuit And current, the turn-off speed is accelerated without increasing the IGBT turn-off overshoot voltage, and the signal delay is small, which can ensure the normal operation of the feedback loop of the IGBT device driving module within a short turn-off time. The invention has strong applicability and can drive various power electronic switching devices.

Furthermore, the detection module includes: a resistor R and a capacitor C; one end of the capacitor C is used as the input terminal of the detection module, and the other end of the capacitor C is used as the output terminal of the detection module. One end is connected to the other end of the capacitor C, and the other end of the resistor R is grounded.

Furthermore, when the differential value of the input voltage of the comparison module is greater than the preset voltage reference value, the comparison module outputs an enable signal to the logic control module to trigger feedback, and the logic control module controls the output current driven by the current to reduce the feedback To the size of the drive current to achieve the purpose of controlling the voltage overshoot.

Furthermore, the preset voltage reference value is between 0-Vdd, usually Vdd/2, and Vdd is the power supply voltage.

Furthermore, the current drive module includes: n forward charging current units and m reverse discharging current units, the forward charging current units are used to provide forward charging current for the IGBT grid; the reverse discharging current units are used for To provide reverse discharge current for the gate of the IGBT; both m and n are positive integers, and m is less than n.

Furthermore, the current drive module includes: n reverse discharge current drive units, for providing reverse discharge current to the IGBT gate; n is a positive integer.

The present invention also provides a method for driving an IGBT device that reduces switching losses, comprising the following steps:

(1) Real-time acquisition of the voltage differential value during the IGBT turn-off process;

(2) Comparing the collected voltage differential value with a preset reference voltage, and outputting the comparison result;

(3) Perform logical operation on the comparison result and the digital bit selection signal to control the working state of the current drive module, and provide a controllable drive current during the IGBT turn-off process.

In the present invention, the turn-off process of the IGBT device is divided into three stages for control: the first stage uses a large gate current (the current drives more than 70% of the full load current) to accelerate the turn-off speed of the IGBT device. The two schemes in the second stage are slightly different. When it is detected that the voltage differential value exceeds the reference value set by the comparison module, for scheme one, the logic control module will control the current drive module to turn on a positive current drive unit (where a ≤n, controlled by the digital bit selection signal), reduce the peak of voltage overcharge, and the input charging current is different according to the set digital bit selection signal, and may even charge the gate of the device in a short time, so n must be is greater than m; for the second scheme, the logic control module will control the current drive module to turn off a current drive unit to slow down the shutdown of the device. In the third stage, when the detected voltage differential value is less than the preset reference value, the voltage spike has passed after a period of inherent delay of the feedback loop, the forward current drive unit is turned off, and the large current is continued to be used for discharge, thus speeding up the shutdown speed. Reduce switching losses.

Furthermore, when the voltage differential value is greater than the preset reference value, the enable signal output by the comparator makes the logic control module turn on the forward charging current drive unit to reduce the discharge current of the gate of the IGBT device and slow down the voltage across the IGBT device. The rising trend reduces the voltage overshoot; when the voltage differential value is less than the preset reference value again, the feedback loop is closed, and the forward drive current module is also closed at this time, and the device continues to discharge with a large current to achieve rapid shutdown.

Furthermore, the preset voltage reference value is between 0 and the power supply voltage (Vdd), and can usually be set to Vdd/2. The smaller the setting, the earlier the feedback will enter, and the larger the setting, the later the feedback will enter. .

In the present invention, when designing each module, by selecting the small transistors with channel width and length in the chip foundry's process technology library (the transistor parameters of different technology libraries are different), and the circuit delay is simulated, While the circuit function can be realized, the delay of the whole feedback loop is strictly controlled below 20ns.

Through the above technical solution conceived by the present invention, compared with the prior art, due to the introduction of feedback control, the device turn-off speed can be increased without increasing the voltage overshoot, and the device turn-off loss can be reduced. The overall delay is less than 20ns, ensuring that the overall feedback loop can be effective during the brief turn-off of the IGBT device.

Description of drawings

Fig. 1 is the functional block diagram of the IGBT device drive circuit that reduces turn-off loss provided by the embodiment of the present invention;

Fig. 2 is the specific circuit diagram of the voltage differential value detection module in the IGBT device driving circuit that reduces the turn-off loss provided by the embodiment of the present invention;

3 is a schematic structural diagram of a current drive module in an IGBT device drive circuit that reduces turn-off loss provided by an embodiment of the present invention;

Fig. 4 is another schematic structural diagram of the current drive module in the IGBT device drive circuit with reduced turn-off loss provided by an embodiment of the present invention;

Fig. 5 is a schematic structural diagram of a comparison module in an IGBT device drive circuit with reduced turn-off loss provided by an embodiment of the present invention;

6 is a schematic structural diagram of an embodiment of a logic control and protection module in an IGBT device drive circuit with reduced turn-off loss provided by an embodiment of the present invention;

7 is a schematic structural diagram of another embodiment of a logic control and protection module in an IGBT device drive circuit that reduces turn-off loss provided by an embodiment of the present invention;

FIG. 8 is a schematic diagram of theoretical working waveforms in the IGBT device driving circuit with reduced turn-off loss provided by an embodiment of the present invention.

detailed description

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

In order to solve the problem that the traditional open-loop drive circuit cannot simultaneously take into account the turn-off loss and the voltage overshoot at turn-off, the present invention designs a set of closed-loop control IGBT drive schemes. By sampling the voltage differential value of the IGBT device in real time, and then through the control module Perform closed-loop control on the gate current drive module. The IGBT device driving circuit with reduced switching loss provided by the invention can control the gate drive current in the dynamic process of turning off the IGBT to achieve the purpose of reducing the turning-off loss.

The IGBT device drive circuit that reduces switching losses provided by the present invention includes: a detection module, a current drive module, a comparison module and a logic control module; the input of the logic control module is used to connect external pulse width modulation signals and digital bit selection signals, and the logic The feedback terminal of the control module is connected to the output terminal of the comparison module, the input terminal of the current drive module is connected to the output terminal of the logic control module, the output terminal of the current drive module is used to connect the control terminal of the IGBT device, and the input terminal of the detection module is used to connect To the output terminal of the IGBT device, the output terminal of the detection module is connected to the input terminal of the comparison module.

The logic control module accesses the pulse width modulation signal (PWM) from the outside to control the switch of the current drive module, and then controls the opening and closing of the IGBT device; uses the detection module to sample the voltage differential value during the IGBT turn-off process in real time, and uses the comparison module to compare The collected voltage is compared with a preset reference voltage, and a control signal is output to a logic control module. The logic control module can input a digital bit selection signal at the same time, and the two signals jointly control the working state of the current drive module after being processed by the logic control module. The current drive module can provide a controllable drive current during the IGBT turn-off process according to the output of the logic control module.

In the embodiment of the present invention, the detection module includes: a resistor R and a capacitor C, one end of the capacitor C is connected to the drain of the IGBT device as the input terminal of the detection module, and the other end of the capacitor C is used as the output terminal of the detection module. One end is connected to the other end of the capacitor C, and the other end of the resistor R is grounded. The voltage value on the resistor R is the voltage differential value of the IGBT device.

In the embodiment of the present invention, when the input voltage differential value is greater than the preset voltage reference value, the comparison module outputs an enable signal to the logic control module to trigger feedback, and the logic control module controls the output current driven by the current , reduce the size of the reverse drive current to achieve the purpose of controlling voltage overshoot. And when the collected voltage is less than the preset reference voltage, the comparison module outputs a disable (disable) signal to the logic control module without triggering feedback, so that the current drive module continues to output a reverse drive large current (more than 70% of the maximum allowable current of the IGBT device ). The preset reference value of the comparison module can be adjusted according to the needs of the control. Its value is between 0 and the power supply voltage (Vdd), and it can usually be set to Vdd/2. The later the big feedback is triggered.

In the embodiment of the present invention, the current driving module includes: n identical forward charging current units and m identical reverse discharging current units, m and n are both positive integers, and n is greater than m; each current driving unit The 100mA forward charging or reverse discharging current provided for the gate of the IGBT is controlled by the logic control module.

In the embodiment of the present invention, a current driving unit is composed of a MOS transistor, the gate of the MOS transistor is the input end of the control, and the saturation current I _Dsat of the MOS transistor is the current provided by the current driving unit.

As another embodiment of the present invention, the current driving module includes: n identical reverse discharge current driving units.

In the embodiment of the present invention, the logic control module is provided with n+m or n output ports corresponding to the current drive module, respectively controlling the working state of each current drive unit, and the digital bit selection signal controls whether the feedback is turned on or off when it takes effect. The number of current units, and then change the size of the current when changing the feedback. For example, if the binary number of the digital bit selection signal represents 10 in decimal, 10 current units are controlled to be turned on or off when the feedback takes effect.

In the embodiment of the present invention, each of the modules described above selects short and narrow transistors in the process library to realize the low delay of the overall feedback loop (the process library is provided by the chip foundry), making the delay of the feedback loop It is controlled below 20ns to realize closed-loop control during the short turn-off time of the IGBT.

In order to further illustrate the IGBT device drive circuit with reduced switching loss provided by the embodiment of the present invention, the specific implementation of the present invention will be further described below:

Fig. 1 is a functional block diagram of the present invention, comprising: a detection module, a comparison module, a logic control module and a current drive module; the detection module detects the voltage variation of the IGBT device in real time to obtain a voltage differential value, and inputs it into the comparison module with the preset Reference value for comparison. When the device is turned off, due to factors such as parasitic inductance, the voltage at both ends of the IGBT will rise rapidly, and the voltage differential value will also rise accordingly. When the detected voltage differential value is greater than the preset reference value of the comparison module, the comparison module A control signal is output to the logic control module to activate the feedback loop, and the logic control module controls the current drive to reduce the gate discharge current according to the digital bit selection signal and the control signal of the comparison module. And when the voltage differential value of the device is less than the reference value, the feedback loop is not opened.

Fig. 2 is the specific circuit diagram of the detection module used by the embodiment of the present invention, the detection module includes: a resistor R and a capacitor C, one end of the capacitor C is connected to the drain of the IGBT device as the input terminal of the detection module, and the other end of the capacitor C is used as As for the output end of the detection module, one end of the resistor R is connected to the other end of the capacitor C, and the other end of the resistor R is grounded. The voltage value on the resistor R is the voltage differential value of the IGBT device.

Fig. 3 is a structural diagram of the current drive module provided by the first embodiment (Scheme 1) of the present invention, the current drive module is divided into n forward charging current drive units and m reverse discharge current drive units, and accepts the control of the logic control module . In the first stage, only the reverse discharge current drive unit is turned on for large current discharge. In the second stage, when the voltage differential value is greater than the preset reference value, the logic control module will receive the enable signal output by the comparator, and at this time the logic control module will turn on the forward charging current drive unit to reduce the gate discharge current, slow down the rising trend of the voltage across the device, and reduce the voltage overshoot. If the voltage rises rapidly, even the gate needs to be charged for a short time, so the number n of forward charging current driving units should be greater than the number m of reverse discharging current driving units. In the third stage, when the voltage differential value is less than the preset reference value of the comparison module again, the feedback loop is closed, and the forward drive current module is also turned off at this time, and the device continues to discharge with a large current to achieve rapid shutdown.

Fig. 4 is a structural diagram of the current drive module provided by the second embodiment (Scheme 2) of the present invention, which is different from the 1st solution in that it omits the forward charging current drive unit, and only relies on the closing part in the second stage of the shutdown process The reverse discharge current drive unit slows down the voltage rise across the device when the device is turned off. Compared with Scheme 1, Scheme 2 has a simpler structure and simpler control, but when the voltage overshoot is large, Scheme 2 cannot suppress the overshoot by charging the gate, so Scheme 2 is not as applicable as Scheme 1.

FIG. 5 is a structural diagram of the comparison module of the present invention, which outputs an enable signal to the logic control module when the input voltage differential value is greater than a preset voltage reference value, otherwise outputs a disable signal.

Fig. 6 is a schematic diagram of a logic control module of Solution 1 of the present invention. There are 3 sets of inputs n+m outputs, and each output port is connected to a current drive unit to realize precise control of gate current.

Fig. 7 is a schematic diagram of the logic control module of the second solution of the present invention, which has 3 sets of inputs and n outputs.

Fig. 8 is a theoretical working waveform diagram of the present invention, because the first stage adopts large current discharge, so the voltage across the device rises faster than the conventional driving scheme, and the forward current drive unit is turned on in the second stage to reduce the discharge current, Can make voltage overshoot no larger than conventional drive schemes. Continue to use large current discharge in the third stage to make the device turn off quickly. It can be seen that the IGBT device driven by this scheme reduces the turn-off time and loss without increasing the overshoot voltage, and solves the problem that the two cannot be taken into account in the past.

It is easy for those skilled in the art to understand that the above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, All should be included within the protection scope of the present invention.

Claims (10)

1. A kind of IGBT device drive circuit that reduces switching loss, is characterized in that, comprises: detection module, current drive module, comparison module and logic control module; The input terminal of the logic control module is used to connect the external pulse width modulation signal and digital bit selection signal, the feedback terminal of the logic control module is connected to the output terminal of the comparison module, and the input terminal of the current drive module is connected to The output terminal of the logic control module, the output terminal of the current drive module is used to connect the control terminal of the IGBT device, the input terminal of the detection module is used to connect to the output terminal of the IGBT device, and the output terminal of the detection module Connect to the input of the compare module. 2. The IGBT device drive circuit as claimed in claim 1, wherein, during work, the logic control module accesses the pulse width modulation signal from the outside to control the switch of the current drive module, and then controls the opening and closing of the IGBT device; The detection module samples the voltage differential value during the IGBT turn-off process in real time, compares the collected voltage with the preset reference voltage through the comparison module, and outputs the control signal to the logic control module; the logic control module can also input digital bit selection signals, two After the signals are processed by the logic control module, they jointly control the working state of the current drive module; the current drive module provides a controllable drive current during the IGBT turn-off process according to the output of the logic control module. 3. The IGBT device drive circuit according to claim 1 or 2, wherein the detection module comprises: a resistor R and a capacitor C; One end of the capacitor C is used as the input end of the detection module, the other end of the capacitor C is used as the output end of the detection module, one end of the resistor R is connected to the other end of the capacitor C, and the resistor R is connected to the other end of the capacitor C. The other end of R is grounded. 4. The IGBT device drive circuit according to any one of claims 1-3, wherein when the differential value of the input voltage of the comparison module is greater than a preset voltage reference value, the comparison module outputs an enabling signal to the logic control module Trigger feedback, the logic control module controls the output current of the current drive, and reduces the magnitude of the reverse drive current to achieve the purpose of controlling the voltage overshoot. 5 . The IGBT device driving circuit according to claim 4 , wherein the preset voltage reference value is between 0 and Vdd, usually Vdd/2, and Vdd is the power supply voltage. 6. The IGBT device drive circuit according to any one of claims 1-5, wherein the current drive module comprises: n forward charging current units and m reverse discharging current units, the forward charging current The unit is used to provide the forward charging current for the IGBT gate; the reverse discharge current unit is used to provide the reverse discharge current for the IGBT gate; both m and n are positive integers, and m is less than n. 7. The IGBT device drive circuit according to any one of claims 1-5, wherein the current drive module comprises: n reverse discharge current drive units for providing reverse discharge current to the IGBT grid ; n is a positive integer. 8. A method for driving an IGBT device that reduces switching losses, is characterized in that it may further comprise the steps: (1) Real-time acquisition of the voltage differential value during the IGBT turn-off process; (2) Comparing the collected voltage differential value with a preset reference voltage, and outputting the comparison result; (3) Perform logical operation on the comparison result and the digital bit selection signal to control the working state of the current drive module, and provide a controllable drive current during the IGBT turn-off process. 9. The IGBT device driving method according to claim 8, wherein when the voltage differential value is greater than a preset reference value, the enable signal output by the comparator makes the logic control module turn on the forward charging current drive unit to reduce The discharge current of the gate of the IGBT device slows down the rising trend of the voltage across the IGBT device and reduces the voltage overshoot; when the voltage differential value is less than the preset reference value again, the feedback loop is closed, and the forward drive current module is also closed at this time , the device continues to use high current discharge to achieve fast shutdown. 10. The method for driving an IGBT device according to claim 8, wherein the preset voltage reference value is between 0 and Vdd, usually Vdd/2, and Vdd is a power supply voltage.