An automatic deviation correction method for IGBT expansion drive signal used for composite switch

Abstract

The present invention relates to intelligent electronic technology, and in particular to an automatic deviation correction method for an IGBT expansion drive signal for a composite switch. An automatic deviation correction method for an IGBT expansion drive signal for a composite switch, wherein a signal sampling circuit detects the change in the driving voltage of an IGBT drive signal when connected in parallel, and converts the change into a level signal through a signal conversion circuit. The level signal is used to judge whether the change time of the IGBT drive signal is synchronized through multiple sets of synchronous logic judgment circuits. If the two are not synchronized, the logic output is a high level, and the output signal drives the locking circuit to operate, locking out the drive signal that changes first and compensating the difference between the two through time delay. The beneficial effect of the present invention is that the reaction time of the electronic circuit is less than most single-chip microcomputer scanning cycles, and the operating state of the parallel IGBT can be quickly adjusted. The analog quantity is converted into a digital quantity through the circuit, and the problem of judging the synchronization of the drive signal is converted into the problem of judging the digital signal.

Description

Technical Field

[0001] The present invention relates to the field of intelligent electronic technology, and in particular to an automatic deviation correction method for an IGBT capacity expansion drive signal used for a composite switch. Background Art

[0002] When IGBTs are used in parallel in a circuit, there is a problem of asynchronous driving signals due to factors such as IGBTs not sharing a common driving chip and inconsistent line lengths. IGBTs will have overvoltage and overcurrent problems that damage the device and cause the problem of uneven current sharing in parallel IGBTs. When the IGBT driving signals are not synchronized, IGBT1 is turned on first and IGBT2 is turned on later. During the dynamic current sharing process of the device, the current flowing through IGBT1 rises first, causing the current flowing through it to be greater than the current flowing through IGBT2 before reaching a static state. During this rising process, the currents flowing through the parallel devices are different, which may cause damage to the device or exceed the threshold of its maximum allowable current, and the IGBT will be damaged by overcurrent. The asynchronous driving signals of IGBTs will also cause different pole-emitter voltages of parallel devices, and in severe cases, it will cause overvoltage damage to a certain IGBT. Summary of the invention

[0003] The technical problem to be solved by the present invention is to overcome the shortcomings existing in the prior art. In order to solve the problem of uneven current caused by the asynchronous driving signal when IGBTs are used in parallel, an automatic deviation correction method for the IGBT expansion driving signal for a composite switch is provided based on the characteristics of the action frequency during the engineering application of the composite switch, so that when the driving signals are asynchronous, the two can achieve automatic deviation correction through delay.

[0004] The present invention is realized by the following technical scheme: a signal sampling circuit detects the change of the driving voltage of the IGBT driving signal when connected in parallel. When the voltage reaches the set threshold, it is considered that the IGBT receives the driving signal, and the signal conversion circuit converts it into a level signal, thereby realizing the conversion of the parallel IGBT conduction time into the level change in time. The level signal passes through multiple groups of logic judgment chips to realize the judgment of whether the change time of the IGBT driving signal is synchronized. If the two are synchronized, the logic output is a low level, and the IGBT is normally turned on; if the two are not synchronized, the logic output is a high level, and the output signal drives the locking circuit to act, locking out the driving signal that changes first to compensate for the difference between the two through a certain time delay.

[0005] According to the above technical solution, preferably, the signal sampling circuit obtains the voltage change of the driving signal, and the voltage sampling circuit is mainly composed of a voltage follower and a signal short delay circuit. By setting a reasonable voltage threshold, when the voltage signal collected by the voltage follower is greater than the voltage threshold, the voltage follower outputs a voltage signal. Through multiple groups of signal sampling circuits, the change time t1 and t2 of the IGBT driving signal are recorded through the change of the output voltage. Based on the actual engineering sampling circuit connected to the main circuit, the signal will be interfered by various mutations and impact signals, and the influence of interference signals on the sampling circuit can be avoided through an external RC short delay circuit.

[0006] According to the above technical solution, preferably, the signal output by the signal sampling circuit is converted into a TTL level signal before being input into the logic judgment chip, and the difference in the conduction time of the IGBT drive signal is converted into a change in the level in time. The signal conversion circuit includes: R1, R2, R3, R4, R5, voltage stabilizing capacitors C1, C2, transistors Q1, Q2, Q3, Q4. R1, R2, R3, transistors Q1, Q2 constitute a signal holding circuit, R4, voltage stabilizing capacitors C1, C2 constitute a voltage stabilizing circuit, and Q3, Q4, R5 constitute a signal conversion circuit. The signal conversion circuit converts the voltage signal into a level signal, and at the same time, the difference Δt in the conduction time of the IGBT becomes a change in the time of the TTL signal. The signal conversion circuit adopts a push-pull output structure, and there is no rise delay and fall delay in the signal change process, which reduces the time required for the signal transmission process.

[0007] According to the above technical solution, preferably, the synchronous logic judgment circuit judges the synchronization of the driving voltage of the IGBT through the input TTL level signal, and the logic judgment chip 1 judges the input level signal. If one of the driving signals of the two IGBTs is in the triggered state, the logic judgment chip 2 is driven to work; if both are in the untriggered state, the logic judgment chip 2 is locked. The logic judgment chip 2 judges the synchronization of the driving signal through the input level signal. If the driving signals of the two IGBTs are both in the triggered state, the logic judgment chip 2 is driven to output a low level to the protection circuit; if only one of them is in the triggered state, the logic judgment chip 2 outputs a high level to the protection circuit.

[0008] According to the above technical solution, preferably, after the signal output by the chip is converted into a voltage signal by the optocoupler chip, the control protection circuit is put into the driving circuit of the IGBT to realize the function of locking the driving signal. The protection circuit includes transistors Q5, Q6, R21, R22, C5, R23, R24, and R25. Capacitor C4 is used as a voltage stabilizing capacitor to stabilize the voltage signal output by the synchronization signal judgment circuit. The base of the transistor Q5 is connected to the output of the synchronization signal judgment circuit. The base of the transistor Q6 is connected to the external driving signal of the IGBT through the base resistor R23. Q7, Q8, and R26 constitute a push-pull output structure. The protection circuit determines the operating state of the circuit through the output of the synchronization signal judgment circuit. If the output is a high-level signal, the driving signal of the IGBT is locked, so that the IGBT will not be turned on. The protection circuit adopts a push-pull output structure, which can quickly turn off the driving signal of the IGBT and improve the reaction speed and reliability of the circuit.

[0009] The beneficial effects of the present invention are:

[0010] 1. The automatic deviation correction circuit and method of the IGBT expansion drive signal for a composite switch of the present invention has a reaction time of the electronic circuit that is shorter than most of the single-chip microcomputer scanning cycles compared to the current single-chip microcomputer control scheme, and can quickly adjust the operating status of the parallel IGBT.

[0011] 2. Creatively convert the time difference of IGBT drive signal into high and low level signal level, convert analog quantity into digital quantity through circuit, and convert the problem of judging the synchronization of drive signal into the problem of judging digital signal.

[0012] 3. The circuit adopts high-speed operational amplifier, fast logic chip and push-pull output structure, which makes the signal transmission speed fast and improves the circuit response speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A structural diagram of an embodiment of the present invention is shown.

[0014] Figure 2 A flow chart illustrating an embodiment of the present invention is shown.

[0015] Figure 3 A signal conversion circuit diagram of an embodiment of the present invention is shown.

[0016] Figure 4 The signal logic judgment flow chart of the embodiment of the present invention is shown as follows

[0017] Figure 5 A circuit diagram of a latching circuit according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0018] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and the best embodiments.

[0019] like Figure 1 As shown, the signal sampling circuit detects the change in the driving voltage of the IGBT driving signal when connected in parallel. When the voltage reaches the set threshold, it is considered that the IGBT receives the driving signal, which is converted into a level signal through the signal conversion circuit, thereby realizing the conversion of the parallel IGBT conduction time into the level change in time. The level signal passes through multiple sets of logic judgment chips to realize the judgment of whether the change time of the IGBT driving signal is synchronized. If the two are synchronized, the logic output is low level, and the IGBT is normally turned on; if the two are not synchronized, the logic output is high level, and the output signal drives the locking circuit to operate, locking out the driving signal that changes first and compensates for the difference between the two through a certain time delay.

[0020] The signal sampling circuit obtains the voltage change of the driving signal. The voltage sampling circuit is mainly composed of a voltage follower and a signal short delay circuit. By setting a reasonable voltage threshold, the voltage follower outputs a voltage signal when the voltage signal collected by the voltage follower is greater than the voltage threshold. Through multiple sets of signal sampling circuits, the change time t1 and t2 of the IGBT driving signal is recorded through the change of the output voltage. Based on the actual engineering sampling circuit connected to the main circuit, the signal will be interfered by various mutations and impact signals. The influence of interference signals on the sampling circuit can be avoided through an external RC short delay circuit.

[0021] like Figure 3 As shown, the signal output by the signal sampling circuit must be converted into a TTL level signal before being input into the logic judgment chip, and the difference in the conduction time of the IGBT drive signal is converted into a change in the level in time. The signal conversion circuit includes: R1, R2, R3, R4, R5, voltage stabilizing capacitors C1, C2, transistors Q1, Q2, Q3, Q4. R1, R2, R3, transistors Q1, Q2 constitute a signal holding circuit, R4, voltage stabilizing capacitors C1, C2 constitute a voltage stabilizing circuit, and Q3, Q4, R5 constitute a signal conversion circuit. The signal conversion circuit converts the voltage signal into a level signal, and at the same time, the difference Δt in the conduction time of the IGBT is converted into a change in the time of the TTL signal. The signal conversion circuit adopts a push-pull output structure, and there is no rise delay and fall delay in the signal change process, which reduces the time required for the signal transmission process.

[0022] like Figure 4As shown, the synchronous logic judgment circuit judges the synchronization of the driving voltage of the IGBT through the input TTL level signal. The logic judgment chip 1 judges the input level signal. If one of the driving signals of the two IGBTs is in the trigger state, the logic judgment chip 2 is driven to work; if both are in the untriggered state, the logic judgment chip 2 is locked. The logic judgment chip 2 judges the synchronization of the driving signal through the input level signal. If the driving signals of the two IGBTs are both in the trigger state, the logic judgment chip 2 is driven to output a low level to the protection circuit; if only one of them is in the trigger state, the logic judgment chip 2 outputs a high level to the protection circuit.

[0023] like Figure 5 As shown, after the signal output by the chip is converted into a voltage signal by the optocoupler chip, the control protection circuit is put into the driving circuit of the IGBT to realize the function of locking the driving signal. The protection circuit includes transistors Q5, Q6, R21, R22, C5, R23, R24, and R25. Capacitor C4 is used as a voltage stabilizing capacitor to stabilize the voltage signal output by the synchronization signal judgment circuit. The base of the transistor Q5 is connected to the output of the synchronization signal judgment circuit, and the base of the transistor Q6 is connected to the external driving signal of the IGBT through the base resistor R23. Q7, Q8, and R26 form a push-pull output structure. The protection circuit determines the operating state of the circuit through the output of the synchronization signal judgment circuit. If the output is a high-level signal, the driving signal of the IGBT is locked, so that the IGBT will not be turned on. The protection circuit adopts a push-pull output structure, which can quickly turn off the driving signal of the IGBT and improve the reaction speed and reliability of the circuit.

[0024] The working principle of the automatic deviation correction circuit and method for IGBT expansion drive signal for composite switch of the present invention is as follows:

[0025] A circuit and method for automatically correcting the IGBT expansion drive signal for a composite switch. In the design process of the present invention, the time difference of the IGBT drive signal is creatively converted into a high and low level signal level, and the analog quantity is converted into a digital quantity through the circuit, and the problem of judging the synchronization of the drive signal is converted into the problem of judging the digital signal. The signal sampling circuit quickly collects the signal through a voltage follower, and converts the signal into a level signal through a level conversion circuit. The sampled output signal is judged by a judgment chip to determine whether the drive signal is synchronized, and can track the changes of the input signal in real time, and determine whether to control the protection circuit to lock the drive signal.

[0026] The IGBT protection circuit controls the drive signal of the locked IGBT through a new type of locking circuit. The circuit speeds up the time for the signal to pass through the protection circuit through the push-pull output structure and circuit design, and can ensure a fast locking drive signal. When the external drive signal is high, the signal is not synchronized after synchronization judgment. When the output signal of the protection circuit is high, the protection circuit is activated, the IGBT drive signal is locked, and the IGBTs running in parallel will not operate.

[0027] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for automatically correcting the IGBT expansion drive signal for a composite switch, characterized in that: include: The signal sampling circuit detects the change in the driving voltage of the driving signals of the two parallel IGBTs. When the voltage reaches the set threshold, it is considered that the IGBT has received the driving signal. The signal conversion circuit converts the signal output by the signal sampling circuit into a level signal, and converts the difference in the conduction time of the two parallel IGBTs into the time change of the TTL level signal; The signal conversion circuit includes resistors R1, R2, R3, R4, R5, voltage stabilizing capacitors C1, C2, transistors Q1, Q2, Q3, Q4; Among them, resistors R1, R2, R3, transistors Q1, Q2 constitute a signal holding circuit; resistor R4, voltage stabilizing capacitors C1, C2 constitute a voltage stabilizing circuit; transistors Q3, Q4, resistor R5 constitute a level conversion circuit, and the signal conversion circuit adopts a push-pull output structure; The signal synchronization judgment circuit judges the synchronization of the driving voltage of the two parallel IGBTs through the input TTL level signal. If the two are synchronized, the logic output signal is low, and the IGBT is normally turned on. If the two are not synchronized, the logic output signal is high, and the output signal drives the locking circuit to operate, locking out the driving signal that changes first and compensating the difference between the two through time delay; The signal synchronization judgment circuit uses multiple sets of logic judgment chips to judge whether the change time of the IGBT drive signal is synchronized. The logic judgment chip 1 in the plurality of logic judgment chips judges the input TTL level signal, and if one of the driving signals of the two parallel IGBTs is in a triggered state, the logic judgment chip 2 is driven to act; if the driving signals of the two parallel IGBTs are both in an untriggered state, the logic judgment chip 2 is locked to drive; Among them, the logic judgment chip 2 judges the synchronization of the driving signal through the input level signal. If the driving signals of the two parallel IGBTs are both in the trigger state, the driving logic judgment chip 2 outputs a low level to the locking circuit; if only one of the driving signals of the two parallel IGBTs is in the trigger state, the logic judgment chip 2 outputs a high level to the locking circuit.

2. The automatic deviation correction method for IGBT expansion drive signal for composite switch according to claim 1, characterized in that: The signal sampling circuit obtains the voltage change of the driving signal. The signal sampling circuit is composed of a voltage follower and a signal short delay circuit. The voltage follower sets a threshold. When the voltage signal collected by the voltage follower is greater than the threshold, the voltage follower outputs a voltage signal.

Images