IGBT circuit protection device based on a pfc circuit

Abstract

The present application relates to the field of IGBT protection, in particular to an IGBT circuit protection device based on a PFC circuit. The scheme comprises: a temperature detection circuit unit detecting the temperature of an IGBT body and outputting a first voltage signal; a temperature hysteresis protection circuit unit comparing the first voltage signal with a threshold value and outputting an over-temperature protection signal; a microcontroller outputting a control signal to a current threshold setting comparison circuit unit to set an IGBT over-current protection threshold according to the mapping relationship between the first voltage signal, the temperature of the IGBT body and the protection current value; a current detection circuit unit detecting a PFC current and outputting a second voltage signal; the current threshold setting comparison circuit unit comparing the second voltage signal with the IGBT over-current protection threshold and outputting an over-current protection signal; the microcontroller outputting a pulse control signal according to the first voltage signal, the second voltage signal, the over-current protection signal and the over-temperature protection signal; and an IGBT drive circuit unit outputting a drive signal to control the IGBT according to the over-temperature protection signal, the over-current protection signal and the pulse control signal. The present application is suitable for IGBT circuits.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of IGBT circuit protection, in particular to an IGBT circuit protection device based on a PFC circuit. BACKGROUND

[0002] At present, most of the high-power household appliances, such as variable frequency air conditioners, have active power factor correction circuits (PFC) designed in the circuit to improve the power factor. In household variable frequency air conditioners, the PFC circuit often adopts a Boost type circuit structure, mainly composed of a PFC inductor, an insulated gate bipolar transistor (IGBT), a fast recovery diode, and a bus electrolytic capacitor. By controlling the IGBT in the PFC circuit to turn on and off in a specified manner, the power factor of the air conditioner can be improved, and the bus capacitor voltage value can be controlled to rise.

[0003] Whether the IGBT can work reliably is related to the reliable operation of the PFC circuit and the entire variable frequency air conditioner. Therefore, it is necessary to protect the IGBT reliably. In actual use, common damage reasons of IGBT include overcurrent, overvoltage, and overtemperature, among which overcurrent damage accounts for a large proportion.

[0004] The common hardware overcurrent protection for IGBT in air conditioners is to convert the IGBT current into a voltage signal through a sampling resistor, compare it with a set threshold voltage, and when the voltage value of the sampling resistor is greater than the set threshold voltage, the hardware circuit immediately blocks the IGBT drive control signal or disconnects the IGBT drive power supply. The advantage of the above-mentioned hardware protection method is that the protection can be realized immediately once the condition is triggered, and the protection is timely. The disadvantage is that the overcurrent protection threshold is fixed and unique. If the protection threshold is set too low, the protection is triggered frequently; if the protection threshold is set too high, the effective protection cannot be achieved. Moreover, as the characteristics of IGBT change with the change of its temperature during operation, it is difficult to reliably protect the IGBT from overcurrent in different states by using a fixed and unique overcurrent protection threshold.

[0005] The common software overcurrent protection method for IGBT in air conditioners is to transmit the voltage value of the IGBT current sampling resistor to the controller AD sampling interface after processing by the signal conditioning circuit. The controller judges whether the IGBT is overcurrent by logical operation processing of the sampled voltage signal. If it is judged that the IGBT is overcurrent, the IGBT drive control signal output is stopped immediately, and the IGBT is turned off to achieve protection. The advantage of the above-mentioned software protection method is that different protection current values can be set according to the control logic to achieve IGBT overcurrent protection while improving the performance of the air conditioner. The disadvantage is that the time from the occurrence of IGBT overcurrent to the realization of IGBT protection is relatively long, the protection is not timely, and there is a risk of IGBT overcurrent damage.

[0006] And for the air conditioner PFC circuit IGBT over temperature protection is little or not involved. Therefore, it is more reasonable and necessary to set over temperature protection, over current protection for IGBT, and adjust the corresponding over current protection value in time according to the temperature change in the working process of IGBT. SUMMARY

[0007] The purpose of the present application is to provide an IGBT circuit protection device based on PFC circuit, which realizes over temperature and over current protection for IGBT and improves the protection ability for IGBT of PFC circuit.

[0008] The present application realizes the above-mentioned purpose by adopting the following technical scheme, an IGBT circuit protection device based on PFC circuit, comprising:

[0009] a temperature detection circuit unit, a temperature hysteresis protection circuit unit, a microcontroller unit and an IGBT drive circuit unit;

[0010] The temperature detection circuit unit is used for detecting the body temperature of IGBT in the PFC circuit and converting the body temperature of IGBT into a first voltage signal output to the temperature hysteresis protection circuit unit and the microcontroller unit;

[0011] The temperature hysteresis protection circuit unit is provided with a first upper threshold value and a first lower threshold value, and is used for comparing the received first voltage signal with the first upper threshold value and the first lower threshold value respectively, processing the over temperature protection signal according to the comparison result, and outputting the processed over temperature protection signal to the microcontroller unit and the IGBT drive circuit unit;

[0012] The microcontroller unit outputs a drive control signal to the IGBT drive circuit unit according to the received first voltage signal and the processed over temperature protection signal;

[0013] The IGBT drive circuit unit is used for outputting an IGBT drive signal to control the conduction or turn-off of IGBT according to the processed over temperature protection signal and the drive control signal.

[0014] Further, the IGBT drive circuit unit outputs an IGBT drive signal to control the conduction or turn-off of IGBT according to the processed over temperature protection signal and the drive control signal specifically comprises:

[0015] The temperature hysteresis protection circuit unit compares the first voltage signal with the first upper threshold value and the first lower threshold value respectively, if the first voltage signal is greater than or equal to the first upper threshold value, the over-temperature protection signal jumps from a high level signal to a low level signal, the low level over-temperature protection signal is valid, and the low level signal forcibly pulls down the drive control signal, at this time, the IGBT drive circuit unit outputs a low level signal to control the IGBT to be turned off, triggering the IGBT hardware over-temperature protection; after the microcontroller unit detects that the over-temperature protection signal is valid, the microcontroller unit stops generating the PWM signal of the next IGBT switching period, and the current PWM signal remains at a low level, triggering the IGBT software over-temperature protection.

[0016] Further, after triggering the over-temperature protection, the IGBT stops working, and the temperature of the IGBT body decreases; if the first voltage signal decreases to be less than or equal to the first lower threshold value, the over-temperature protection signal jumps from a low level to a high level, the high level over-temperature protection signal is invalid, and the IGBT hardware over-temperature protection is exited; after the microcontroller unit detects that the over-temperature protection signal is invalid, the IGBT software over-temperature protection is exited, and the microcontroller outputs the next switching period and the subsequent PWM pulse control signal according to the current state, at this time, the IGBT drive circuit unit controls the IGBT to be turned on or turned off according to the PWM pulse control signal.

[0017] Further, the device further comprises a current detection circuit unit and a current threshold setting comparison circuit unit;

[0018] The current detection circuit unit is used for detecting the PFC circuit current, and outputs a second voltage signal to the current threshold setting comparison circuit unit and the microcontroller unit after processing the voltage drop across the sampling resistor of the PFC circuit current;

[0019] The microcontroller unit outputs an over-current threshold setting control signal to the current threshold setting comparison circuit unit according to the received first voltage signal and the mapping relationship between the temperature of the IGBT body and the IGBT over-current protection current value;

[0020] The current threshold setting comparison circuit unit adjusts the IGBT over-current protection threshold value according to the received over-current threshold setting control signal by adjusting circuit parameters;

[0021] The current threshold setting comparison circuit unit compares the second voltage signal with the IGBT over-current protection threshold value, processes the over-current protection signal according to the comparison result, and outputs the over-current protection signal to the microcontroller unit and the IGBT drive circuit unit.

[0022] Further, the microcontroller unit is further used for outputting a drive control signal to the IGBT drive circuit unit according to the received first voltage signal, the second voltage signal, the processed over-current protection signal and the processed over-temperature protection signal.

[0023] The IGBT drive circuit unit is further configured to output an IGBT drive signal to control turning on or turning off of the IGBT according to the processed over-temperature protection signal, the processed over-current protection signal and the drive control signal.

[0024] Further, the IGBT drive circuit unit outputs the IGBT drive signal to control turning on or turning off of the IGBT according to the processed over-temperature protection signal, the processed over-current protection signal and the drive control signal specifically includes:

[0025] The current threshold setting comparison circuit unit compares the second voltage signal with the IGBT over-current protection threshold, and if the second voltage signal is greater than or equal to the over-current protection threshold signal, the over-current protection signal jumps from a high-level signal to a low-level signal, the low-level over-current protection signal is valid, the low-level signal forcibly pulls down the drive control signal, at this time, the IGBT drive circuit unit outputs a low-level signal to control turning off of the IGBT, and triggers the IGBT hardware over-current protection; after the microcontroller unit detects that the over-current protection signal is valid, the IGBT software over-current protection is triggered, the PWM signal of the next IGBT switching period is stopped from being generated, and the current PWM signal remains low, the holding time is set by software, and after the holding time ends, the IGBT over-current protection of this time ends.

[0026] Or the temperature hysteresis protection circuit unit compares the first voltage signal with the first upper threshold and the first lower threshold respectively, if the first voltage signal is greater than or equal to the first upper threshold, the over-temperature protection signal jumps from a high-level signal to a low-level signal, the low-level over-temperature protection signal is valid, the low-level signal forcibly pulls down the drive control signal, at this time, the IGBT drive circuit unit outputs a low-level signal to control turning off of the IGBT, and triggers the IGBT hardware over-temperature protection; after the microcontroller unit detects that the over-temperature protection signal is valid, the PWM signal of the next IGBT switching period is stopped from being generated, and the current PWM signal remains low, and the IGBT software over-temperature protection is triggered.

[0027] Further, the microcontroller unit outputs the over-current threshold setting control signal according to the received first voltage signal and the mapping relationship between the IGBT body temperature and the IGBT over-current protection current value specifically includes:

[0028] According to the relationship between the IGBT body temperature and the IGBT junction temperature, and the relationship between the IGBT junction temperature and the IGBT impact current, the IGBT body temperature is divided into intervals, the IGBT overcurrent current value corresponding to each IGBT body temperature interval is calculated, and the mapping relationship between the temperature interval and the overcurrent current value is stored in the microcontroller in advance, the microcontroller unit calculates the IGBT body temperature according to the received first voltage signal, and finds the IGBT overcurrent current value corresponding to the IGBT body temperature according to the mapping relationship between the temperature interval and the overcurrent current value, and finally outputs the overcurrent threshold setting control signal according to the found IGBT overcurrent current value.

[0029] Further, the current threshold setting comparison circuit unit includes a two-stage comparator structure, the first-stage comparator compares the second voltage signal with the overcurrent protection threshold signal, the second-stage comparator sets a second upper threshold and a second lower threshold, and compares the first-stage comparator output signal with the second upper threshold and the second lower threshold to output the overcurrent protection signal.

[0030] When the first-stage comparator output signal decreases from high level to less than or equal to the second lower threshold, the second-stage comparator outputs the overcurrent protection signal from high level to low level immediately, and remains low level; when the first-stage comparator output signal increases from low level to greater than or equal to the second upper threshold, the second-stage comparator outputs the overcurrent protection signal from low level to high level immediately, and remains high level.

[0031] The beneficial effects of the present application are:

[0032] The IGBT body temperature of the PFC circuit of the air conditioner is detected in real time, and the IGBT over-temperature protection triggering temperature and the IGBT over-temperature protection exit temperature are set respectively, so that the timeliness and efficiency of the IGBT hardware circuit over-temperature protection are realized;

[0033] When the over-temperature protection is triggered, the over-temperature protection signal jumps from high level signal to low level signal, the low level over-temperature protection signal is effective, the low level signal forcibly pulls down the driving control signal, at this time the IGBT driving circuit unit outputs low level signal to control the IGBT to be turned off, and the IGBT hardware over-temperature protection is triggered; after the microcontroller unit detects that the over-temperature protection signal is effective, the microcontroller unit stops generating the PWM signal of the next IGBT switching period, and the current PWM signal remains low level, and the IGBT software over-temperature protection is triggered; through the double over-temperature protection of hardware and software, the reliability of the IGBT over-temperature protection is improved;

[0034] After the over-temperature protection is triggered, the IGBT stops working, and only when the IGBT body temperature is less than or equal to the over-temperature protection exit temperature value, the IGBT hardware over-temperature protection is exited, and the anti-interference ability of the IGBT over-temperature protection is improved;

[0035] In the case that the IGBT hardware over-temperature protection circuit fails without affecting the normal operation of the IGBT driving circuit and the IGBT temperature detection circuit, the microcontroller can still detect the IGBT body temperature in real time, and after logical judgment by software, the IGBT over-temperature protection is realized through software;

[0036] The microcontroller detects the IGBT body temperature in real time, judges the temperature interval to which the IGBT body temperature belongs, finds the IGBT over-current value corresponding to the temperature interval pre-stored in the program, and outputs an IGBT over-current value setting signal, which is used to realize the adjustment of the IGBT hardware over-current protection threshold value.

[0037] The current threshold setting comparison unit adopts two-stage comparators, and the second-stage comparator is set as a hysteresis comparator. After the IGBT over-current occurs, the two-stage comparators ensure that the over-current protection signal maintains a long effective time, further ensures that the IGBT software over-current protection is triggered before the hardware over-current protection is exited, and improves the reliability of the IGBT over-current protection.

[0038] In the case that the IGBT over-temperature protection signal and the over-current protection signal are triggered at will, the corresponding hardware and software double protection can be realized, and the timeliness and reliability of the IGBT protection are improved. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 It is the IGBT circuit protection device circuit structure schematic diagram provided by the embodiment of the application based on the PFC circuit;

[0040] Figure 2 It is the temperature detection circuit unit and the temperature hysteresis protection circuit unit circuit diagram provided by the embodiment of the application;

[0041] Figure 3 It is the input-output characteristic curve diagram of the temperature hysteresis protection circuit unit provided by the embodiment of the application;

[0042] Figure 4 It is the IGBT over-temperature protection timing relationship diagram provided by the embodiment of the application;

[0043] Figure 5 It is the current detection circuit unit circuit diagram provided by the embodiment of the application;

[0044] Figure 6 It is the current threshold setting comparison unit circuit diagram provided by the embodiment of the application;

[0045] Figure 7Is the current threshold setting comparison unit second level hysteresis comparator input-output characteristic curve provided by the embodiment of the application;

[0046] Figure 8 Is the IGBT overcurrent protection timing relationship diagram provided by the embodiment of the application;

[0047] Figure 9 Is the IGBT over-temperature protection flowchart provided by the embodiment of the application;

[0048] Figure 10 Is the IGBT overcurrent threshold setting flowchart provided by the embodiment of the application;

[0049] Figure 11 Is the IGBT overcurrent protection flowchart provided by the embodiment of the application. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical scheme and advantages of the embodiments of the application clearer, the technical scheme in the embodiments of the application will be described clearly and completely below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0051] The specific embodiments of the application will be described in detail below. Figures 1-11 The specific embodiments of the application will be described in detail below.

[0052] The application is based on an IGBT circuit protection device of a PFC circuit, as shown in the figure, which comprises: Figure 1

[0053] A temperature detection circuit unit, a temperature hysteresis protection circuit unit, a current detection circuit unit, a current threshold setting comparison circuit unit, a microcontroller unit and an IGBT drive circuit unit;

[0054] The temperature detection circuit unit is used for detecting the body temperature of the IGBT in the PFC circuit and converting the body temperature of the IGBT into a first voltage signal V1 and outputting the first voltage signal V1 to the temperature hysteresis protection circuit unit and the microcontroller unit;

[0055] The temperature hysteresis protection circuit unit is provided with a first upper threshold value and a first lower threshold value, the first upper threshold value is greater than the first lower threshold value, the temperature hysteresis protection circuit unit is used for comparing the received first voltage signal V1 with the first upper threshold value and the first lower threshold value respectively, processing the over-temperature protection signal T-FO according to the comparison result, and outputting the processed over-temperature protection signal T-FO to the microcontroller unit and the IGBT drive circuit unit; ​

[0056] The current detection circuit unit is used for detecting the PFC circuit current, and outputs a second voltage signal V2 to the current threshold setting comparison circuit unit and the microcontroller unit after processing a voltage drop across a sampling resistor RS of the PFC circuit current;

[0057] The microcontroller unit outputs an overcurrent threshold setting control signal S1 to the current threshold setting comparison circuit unit according to the received first voltage signal V1 and a mapping relationship between the IGBT body temperature and the IGBT overcurrent protection current value;

[0058] The current threshold setting comparison circuit unit adjusts the IGBT overcurrent protection threshold according to the received overcurrent threshold setting control signal S1 by adjusting circuit parameters;

[0059] The current threshold setting comparison circuit unit compares the second voltage signal V2 with the IGBT overcurrent protection threshold, processes the overcurrent protection signal I-FO according to a comparison result, and outputs the overcurrent protection signal I-FO to the microcontroller unit and the IGBT drive circuit unit;

[0060] The microcontroller unit outputs a drive control signal PWM to the IGBT drive circuit unit according to the received first voltage signal V1, the second voltage signal V2, the processed overcurrent protection signal I-FO, the overtemperature protection signal T-FO, and a current system state;

[0061] The IGBT drive circuit unit is also used for outputting an IGBT drive signal PWM-OUT to control the conduction or turn-off of the IGBT according to the processed overtemperature protection signal T-FO, the overcurrent protection signal I-FO, and the drive control signal PWM.

[0062] In an embodiment of the present application, the IGBT drive circuit unit outputs the IGBT drive signal PWM-OUT to control the conduction or turn-off of the IGBT according to the processed overtemperature protection signal T-FO and the drive control signal PWM, and specifically includes:

[0063] The temperature hysteresis protection circuit unit compares the first voltage signal V1 with the first upper threshold and the first lower threshold, respectively, and if the first voltage signal V1 is greater than or equal to the first upper threshold, the overtemperature protection signal T-FO jumps from a high-level signal to a low-level signal, and the overtemperature protection signal T-FO is low-level effective. The low-level signal forcibly pulls down the drive control signal PWM-IN, at this time, the IGBT drive circuit unit outputs a low-level signal PWM-OUT to control the turn-off of the IGBT, triggering the IGBT hardware overtemperature protection; at the same time, the effective overtemperature protection signal T-FO is output to the microcontroller unit, and after the microcontroller unit detects that the overtemperature protection signal is effective, the microcontroller unit stops generating a PWM signal of a next IGBT switching period, and the current PWM signal remains low, triggering the IGBT software overtemperature protection.

[0064] After triggering the over-temperature protection, the IGBT stops working, and the IGBT body temperature gradually decreases. If the first voltage signal V1 gradually decreases to be less than or equal to the first lower threshold value, the over-temperature protection signal T-FO jumps from a low level to a high level, at this time, the over-temperature protection signal is invalid, and the IGBT hardware over-temperature protection is exited. After the microcontroller unit detects the invalid over-temperature protection signal T-FO, the IGBT software over-temperature protection is exited, and the microcontroller calculates the next switching period and the subsequent PWM pulse control signal according to the current state. At this time, the IGBT drive circuit unit controls the IGBT to be turned on or turned off according to the PWM pulse control signal.

[0065] In an embodiment of the present application, the microcontroller unit outputs the over-current threshold setting control signal S1 according to the received first voltage signal V1 and the IGBT body temperature and IGBT over-current protection current value mapping relationship, specifically including:

[0066] According to the relationship between the IGBT body temperature and the IGBT junction temperature, and the relationship between the IGBT junction temperature and the IGBT impact current, the IGBT body temperature is divided into intervals, for example, (T1, T2], (T2, T3], …, (Tn, Tn+1], T1 < Tn+1, the IGBT over-current current value corresponding to each IGBT body temperature interval is calculated, I1, I2, …, In, and I1 > I2 > … > In, and the mapping relationship between the temperature interval and the current is pre-stored in the microcontroller. The microcontroller unit calculates the IGBT body temperature according to the received first voltage signal V1, and finds the IGBT over-current current value corresponding to the IGBT body temperature according to the mapping relationship between the temperature interval and the current, and outputs the IGBT over-current threshold setting control signal S1 according to the found IGBT over-current current value.

[0067] The current threshold setting comparison circuit unit controls the digital potentiometer to change the resistance value of the voltage dividing resistor in the series voltage dividing circuit to realize different voltage division, so as to set the IGBT over-current threshold.

[0068] In an embodiment of the present application, the IGBT drive circuit unit outputs the IGBT drive signal PWM-OUT to control the IGBT to be turned on or turned off according to the processed over-temperature protection signal T-FO, the over-current protection signal I-FO and the drive control signal PWM, specifically including:

[0069] The current threshold setting comparison circuit unit compares the second voltage signal V2 with the set IGBT overcurrent threshold, and if the second voltage signal V2 is greater than or equal to the set IGBT overcurrent threshold, the overcurrent protection signal I-FO jumps from a high-level signal to a low-level signal, and the overcurrent protection signal I-FO is low-level effective. The low-level signal forcibly pulls down the drive control signal PWM-IN, at this time, the IGBT drive circuit unit outputs a low-level signal PWM-OUT to control the IGBT to be turned off, triggering the IGBT hardware overcurrent protection; after the microcontroller unit detects that the overcurrent protection signal is effective, the IGBT software overcurrent protection is triggered, the PWM signal of the next IGBT switching period is stopped from being generated, and the current PWM signal remains low-level, the holding time is set by software, and the holding time ends, then the IGBT overcurrent protection of this time ends;

[0070] The temperature hysteresis protection circuit unit compares the first voltage signal V1 with the first upper threshold and the first lower threshold respectively, and if the first voltage signal V1 is greater than or equal to the first upper threshold, the overtemperature protection signal T-FO jumps from a high-level signal to a low-level signal, and the overtemperature protection signal T-FO is low-level effective. The low-level signal forcibly pulls down the drive control signal PWM-IN, at this time, the IGBT drive circuit unit outputs a low-level signal PWM-OUT to control the IGBT to be turned off, triggering the IGBT hardware overtemperature protection; after the microcontroller unit detects that the overtemperature protection signal is effective, the PWM signal of the next IGBT switching period is stopped from being generated, and the current PWM signal remains low-level, triggering the IGBT software overtemperature protection.

[0071] In the case of triggering of the IGBT overtemperature protection signal and the overcurrent protection signal, the corresponding hardware and software double protection can be realized, and the timeliness and reliability of the IGBT protection are improved.

[0072] The current threshold setting comparison circuit unit utilizes the open-drain output characteristic of the comparator, and a pull-up resistor is connected to the positive power supply and a capacitor is connected to the analog ground at the output end of the comparator, so that the capacitor charging loop and the discharging loop are different. By adjusting the resistance value of the pull-up resistor and the capacitance value of the capacitor, the capacitor charging time and the discharging time can be easily adjusted, and then the output voltage signal characteristic of the comparator can be adjusted. Specifically, when the second voltage signal V2 is greater than or equal to the set IGBT overcurrent threshold, the comparator output is in a low-resistance state, the capacitor is quickly discharged to a low level through the internal circuit of the comparator, and the output voltage of the comparator changes from high level to low level; when the second voltage signal V2 changes to be less than the set IGBT overcurrent threshold, the comparator output is in a high-resistance state, the power supply charges the capacitor through the pull-up resistor, and the output voltage of the comparator changes from low level to high level; the capacitor discharging time is much less than the capacitor charging time.

[0073] In one embodiment of the present application, the current threshold setting comparison circuit unit mainly comprises a two-stage comparator structure. The first stage comparator compares the second voltage signal V2 and the set IGBT overcurrent threshold, and the characteristics of the comparator output voltage signal are adjusted by adjusting the pull-up resistance value and the capacitance value connected to the output end of the comparator. The second stage comparator is a hysteresis comparator, which is provided with a second upper threshold value and a second lower threshold value. The first stage comparator output signal is compared with the second upper and lower threshold values to shape the first stage comparator output signal, and the output is the overcurrent protection signal I-FO. Specifically, when the first stage comparator output signal decreases from high level to less than or equal to the second lower threshold value, the second stage comparator output I-FO immediately jumps from high level to low level and remains low. When the first stage comparator output signal increases from low level to greater than or equal to the second upper threshold value, the second stage comparator output I-FO immediately jumps from low level to high level and remains high. By setting the two-stage comparator, it is ensured that when the IGBT overcurrent occurs, the overcurrent protection signal I-FO remains low for a sufficient time to ensure that the time required for the microcontroller to detect the valid I-FO signal to implement the software overcurrent protection is less than the time for which the I-FO remains low, thereby realizing effective IGBT overcurrent protection and avoiding the situation that after the IGBT overcurrent occurs for the first time, the hardware protection ends while the software protection has not started, and the IGBT overcurrent occurs again or multiple times in succession and fails.

[0074] Referring to Figure 2 In the specific embodiment of the present application, the temperature detection circuit unit detects the IGBT body temperature by using a thermistor RT. The RT can be a compression ring type thermistor, a plug-in type thermistor or other forms of thermistors. In this embodiment, a compression ring type NTC thermistor is selected. The thermistor is fixed tightly with the IGBT body by a screw. The thermistor RT is connected in series with the resistor R13 to divide the voltage. The divided voltage signal is filtered by a filter circuit composed of the capacitor C8, the resistor R14 and the capacitor C9. When the IGBT body temperature rises, the resistance value of the RT decreases, the divided voltage of the resistor R13 increases, and V1 becomes larger. When the IGBT body temperature decreases, the resistance value of the RT increases, the divided voltage of the resistor R13 decreases, and V1 becomes smaller.

[0075] The temperature hysteresis protection circuit unit uses a hysteresis comparator, which is provided with a first upper threshold value VH and a first lower threshold value VL, VL < VH.

[0076]

[0077]

[0078] Among them,

[0079] In this embodiment, the comparator uses LM2903, which is powered by a 5V power supply, R15 = R 17 = 1KΩ, R 16 = R 18 = 4.7KΩ, V OL = 0V, V OH = 5V, then VL=3.40V, VH=4.28V.

[0080] Referring to Figure 3 Fig. 1, in the specific embodiment of the present application, the temperature hysteresis protection circuit unit input-output characteristic is that when the input signal VI gradually increases from 0 to greater than or equal to VH, the output T-FO jumps from high level VCC to low level 0, and as VI continues to increase, the output T-FO remains unchanged at low level; when the input signal VI gradually decreases to less than or equal to VL, the output T-FO jumps from low level to high level, and as VI continues to decrease, the output T-FO remains unchanged at high level.

[0081] Referring to Figure 2 and Figure 4 Fig. 2, the PFC circuit works, and as the IGBT body temperature gradually increases, VI gradually increases. When VI≥VH, the over-temperature protection signal T-FO immediately jumps from high level to low level 0, the clamping diode D2 is turned on to forcibly pull down PWM-IN, and the IGBT drive circuit unit synchronously outputs the PWM-OUT drive signal as low level according to PWM-IN, so that the IGBT is turned off, thereby realizing IGBT hardware over-temperature protection. After the microcontroller detects the valid over-temperature protection signal T-FO, the next IGBT switching period PWM output is immediately stopped and remains as low level, thereby realizing IGBT software over-temperature protection, which is delayed by t1 time length compared with IGBT hardware over-temperature protection. After the IGBT is turned off, as the IGBT body temperature decreases, when VI≤VL, the over-temperature protection signal T-FO immediately jumps from low level to high level, and the clamping diode D2 remains reverse cut-off, thereby exiting IGBT hardware over-temperature protection. After the microcontroller detects that the over-temperature protection signal T-FO is high level, the output PWM control signal is calculated according to the current system state, thereby exiting IGBT software over-temperature protection, which is delayed by t2 time length compared with exiting IGBT hardware over-temperature protection. The IGBT is normally turned on or turned off according to the PWM-OUT drive signal.

[0082] In one embodiment of the present application, the air conditioner PFC circuit IGBT over-temperature protection step, as shown in Figure 9 , includes:

[0083] S101. After the air conditioner is started, the PFC circuit is put into work, and the IGBT normally works, so that the IGBT body temperature increases;

[0084] S102. After the air conditioner is started and runs, the temperature detection circuit detects the IGBT body temperature in real time through the thermistor.

[0085] S103. After the air conditioner is started, the temperature threshold comparison unit compares the IGBT body temperature in real time. When the IGBT body temperature is less than the trigger over-temperature protection threshold set by the hardware circuit, the IGBT works normally;

[0086] S104. When the IGBT body temperature is greater than or equal to the trigger over-temperature protection threshold set by the hardware circuit, an effective over-temperature protection signal T-FO is generated immediately, and at the same time the hardware circuit blocks the PWM-IN signal immediately, triggering the IGBT hardware over-temperature protection, turning off the IGBT, and stopping the IGBT from working;

[0087] S105. After the microcontroller detects the effective over-temperature protection signal T-FO, the output of the PWM pulse control signal is stopped and kept at a low level, triggering the IGBT software over-temperature protection;

[0088] S106. The IGBT enters the hardware over-temperature protection and the software over-temperature protection in turn, and is in the off state and remains;

[0089] S107. After the IGBT stops working, as the IGBT body temperature decreases, when the IGBT body temperature is greater than the exit over-temperature protection threshold set by the hardware circuit, the IGBT over-temperature protection is in the off state;

[0090] S108. When the IGBT body temperature is less than or equal to the exit over-temperature protection threshold set by the hardware circuit, the over-temperature protection signal T-FO immediately changes to an invalid state, and the IGBT hardware over-temperature protection is exited;

[0091] S109. After the microcontroller detects the invalid over-temperature protection signal T-FO, the IGBT software over-temperature protection is exited, and the output of the PWM pulse control signal is calculated according to the current system state;

[0092] S110. The IGBT exits the hardware over-temperature protection and the software over-temperature protection in turn, and works normally according to the PWM control signal.

[0093] After triggering the IGBT over-temperature protection, the microcontroller can adjust the limit of the air conditioner compressor operating frequency according to the current system state, reduce the machine load, and reduce the risk of shutdown.

[0094] The microcontroller unit detects the IGBT body temperature voltage signal V1 in real time, and calculates the IGBT body temperature value according to V1. The IGBT body temperature and the IGBT overcurrent protection current value mapping relationship are stored in the microcontroller, the IGBT body temperature is divided into intervals according to the characteristics of the IGBT, such as (T1, T2], (T2, T3], …, (Tn, Tn+1], T1

[0095] Referring to Figure 5 As shown in the figure, the current detection circuit unit detects the voltage across the sampling resistor RS in the PFC circuit to detect the current of the PFC circuit, and outputs the voltage signal V2 after conditioning.

[0096] Referring to Figure 6 As shown in the figure, in the current threshold setting comparison unit circuit, R10 is a digital potentiometer, and the fixed resistance value is R AB The W position is controlled by the control signal S1, and R AW and R WB The resistance R11, the resistance R12 and the digital potentiometer R10 are connected in series, and according to the actual application, appropriate resistance R11 and resistance R12 are selected, which can reduce the voltage value interval corresponding to the digital potentiometer R10, can improve the adjustment resolution of the fixed resolution digital potentiometer R10, and at the same time limits the minimum value and maximum value of the voltage division value VP.

[0097] Among them,

[0098] In an embodiment of the present application, the specific steps of IGBT overcurrent threshold setting are shown in Figure 10 As shown in the figure, it includes:

[0099] S201. The temperature detection unit detects the IGBT body temperature in real time by using a thermistor, converts it into a temperature voltage signal V1 and outputs it to the microcontroller;

[0100] S202. The microcontroller samples the temperature voltage signal V1, calculates the IGBT body temperature, judges the temperature interval, according to the stored temperature interval and overcurrent value mapping relationship, finds the corresponding IGBT overcurrent value and outputs the IGBT overcurrent protection current value setting signal S1 to the current threshold setting comparison circuit unit;

[0101] S203. The current threshold setting comparison circuit unit adjusts the digital potentiometer according to the control signal S1 to set the voltage division value VP, i.e. to achieve the IGBT overcurrent threshold setting.

[0102] Referring to Figure 6 When V2≥VP, the internal switch tube of the comparator U2 is turned on to ground, and the capacitor C5 is discharged quickly through the comparator U2. When V2<VP, the comparator U2 outputs a high resistance state, and the capacitor C5 is charged slowly by VCC through the resistor R9. By adjusting the resistance value of the resistor R9 and the capacitance value of the capacitor C5, the charging and discharging time of the capacitor C5 can be adjusted. The comparator U4, the resistors R20, R21, R22, R23 and the zener diode D3 together constitute a same-phase hysteresis comparator.

[0103] Lower threshold of same-phase hysteresis comparator

[0104] Upper threshold of same-phase hysteresis comparator

[0105] wherein V N = V D3

[0106] In this embodiment, the comparator uses LM2903, which is powered by a 5V power supply, R 21 = 1KΩ, R 23 = 15KΩ, V D3 = 4.3V, then V T- = 4.25V, V T+ = 4.59V.

[0107] Referring to Figure 7 As shown in the figure, the input-output characteristic of the same-phase hysteresis comparator is that when the input signal VC5 gradually increases from 0 to be greater than or equal to VT+, the output I-FO jumps from low level 0 to high level VCC, and as VC5 continues to increase, the output I-FO remains unchanged at high level; when the input signal VC5 gradually decreases to be less than or equal to VT-, the output I-FO jumps from high level to low level, and as VC5 continues to decrease, the output I-FO remains unchanged at low level.

[0108] Referring to Figure 6 and Figure 8As shown, when the PFC circuit current sampling signal V2≥VP, the comparator U2 outputs a low resistance state, the capacitor C5 is immediately discharged through the internal circuit of the comparator U2, and the voltage VC5 quickly decreases to VT- of the hysteresis comparator, the overcurrent protection signal I-FO jumps from high to low, the clamping diode D1 is turned on to forcibly pull down PWM-IN, the IGBT drive circuit unit synchronously outputs PWM-OUT as a low level according to PWM-IN, the IGBT is turned off, and the IGBT hardware overcurrent protection is triggered. When the IGBT is turned off, the current decreases, and when V2<VP, the comparator U2 outputs a high resistance state, VCC charges the capacitor C5 slowly through the resistor R9, the voltage VC5 rises, and rises to VT+ of the hysteresis comparator, the overcurrent protection signal I-FO jumps from low to high, and the IGBT hardware overcurrent protection is exited. The duration of the IGBT hardware overcurrent protection is t4.

[0109] After the microcontroller detects the valid overcurrent protection signal I-FO, the next IGBT switching cycle PWM output is stopped immediately, and the output is kept as a low level, so that the IGBT software overcurrent protection is realized. The software overcurrent protection time is maintained for t3, and the IGBT software overcurrent protection is exited after the software protection time t3 ends, that is, the IGBT overcurrent protection of this time is ended.

[0110] Further, from the IGBT overcurrent to triggering the software overcurrent protection, t5 is needed. It is ensured that t5 is much smaller than t4, so that the IGBT hardware overcurrent protection is exited, and the software overcurrent protection is triggered, which causes the IGBT to continuously overcurrent again or multiple times and fails.

[0111] In an embodiment of the present application, the IGBT overcurrent protection steps of the PFC circuit of the air conditioner are as shown in the following table. Figure 11 As shown, the steps include:

[0112] S301. After the air conditioner is started, the PFC circuit is put into work, and the IGBT normally works.

[0113] S302. After the air conditioner is normally started, the current detection circuit detects the current of the IGBT of the PFC circuit through the sampling resistor RS.

[0114] S303. When the detected IGBT current value is less than the IGBT overcurrent threshold set by the hardware circuit, the IGBT normally works.

[0115] S304. When the detected IGBT current value is greater than or equal to the IGBT overcurrent threshold set by the hardware circuit, a valid overcurrent protection signal I-FO is immediately generated, and at the same time, the hardware circuit immediately blocks the PWM-IN signal, triggers the IGBT hardware overcurrent protection, turns off the IGBT, and the IGBT stops working. The duration of the IGBT hardware overcurrent protection is t4.

[0116] S305. After the microcontroller detects the valid over-current protection signal I-FO, the output of the PWM pulse control signal is stopped and kept at a low level, triggering the IGBT software over-current protection, and the software sets the IGBT software over-current protection maintenance time as t3. The time from the occurrence of over-current of the IGBT to the triggering of the software over-current protection is t5, and there is a relationship of t5 < t4 < t3;

[0117] S306. When the IGBT software over-current protection time t3 is not ended, the IGBT is in the off state and remains;

[0118] S307. When the IGBT software over-current protection time t3 is ended, the IGBT exits the software over-current protection. The microcontroller calculates the output PWM pulse control signal according to the current system state, and the IGBT normally works according to the PWM control signal.

[0119] In summary, the application realizes the timeliness and efficiency of the hardware circuit over-temperature protection, improves the reliability of the IGBT over-temperature protection through the hardware and software double over-temperature protection, improves the anti-interference ability of the IGBT over-temperature protection only when the IGBT body temperature is less than or equal to the exit over-temperature protection temperature value, and creatively associates the IGBT body temperature with the IGBT over-current protection current threshold, realizes the use of different over-current protection values in different temperature intervals of the IGBT body, the main feature is that the higher the IGBT body temperature, the lower the over-current protection value, which improves the timeliness and effectiveness of the IGBT over-current protection, and further ensures the reliability of the IGBT over-current protection through the two-stage comparator circuit setting.

Claims

1. An IGBT circuit protection device based on a PFC circuit, characterized by The application relates to a temperature hysteresis protection circuit unit for an IGBT in a PFC circuit. The temperature detection circuit unit is used for detecting the body temperature of the IGBT in the PFC circuit and converting the body temperature of the IGBT into a first voltage signal output to the temperature hysteresis protection circuit unit and the microcontroller unit. The temperature hysteresis protection circuit unit is provided with a first upper threshold value and a first lower threshold value, and is used for comparing the received first voltage signal with the first upper threshold value and the first lower threshold value respectively, processing an over-temperature protection signal according to the comparison result, and outputting the processed over-temperature protection signal to the microcontroller unit and the IGBT drive circuit unit. The microcontroller unit outputs a drive control signal to the IGBT drive circuit unit according to the received first voltage signal and the processed over-temperature protection signal. The IGBT drive circuit unit is used for outputting an IGBT drive signal to control the conduction or turn-off of the IGBT according to the processed over-temperature protection signal and the drive control signal. The current detection circuit unit is used for detecting the PFC circuit current, processing the voltage drop of a sampling resistor at two ends of the PFC circuit current, and outputting a second voltage signal to the current threshold setting comparison circuit unit and the microcontroller unit. The microcontroller unit outputs an over-current threshold setting control signal to the current threshold setting comparison circuit unit according to the received first voltage signal and the mapping relationship between the IGBT body temperature and the IGBT over-current protection current value. The current threshold setting comparison circuit unit adjusts the IGBT over-current protection threshold by adjusting circuit parameters according to the received over-current threshold setting control signal. The current threshold setting comparison circuit unit compares the second voltage signal with the IGBT over-current protection threshold, processes an over-current protection signal according to the comparison result, and outputs the over-current protection signal to the microcontroller unit and the IGBT drive circuit unit. The microcontroller unit outputs an over-current threshold setting control signal according to the received first voltage signal and the mapping relationship between the IGBT body temperature and the IGBT over-current protection current value, and the specific process comprises the following steps: According to the relationship between the IGBT body temperature and the IGBT junction temperature and the relationship between the IGBT junction temperature and the IGBT impact current, the IGBT body temperature is divided into intervals, the IGBT over-current current value corresponding to each IGBT body temperature interval is calculated, the mapping relationship between the temperature interval and the over-current current value is pre-stored in the microcontroller, the microcontroller unit calculates the IGBT body temperature according to the received first voltage signal, finds the IGBT over-current current value corresponding to the IGBT body temperature according to the mapping relationship between the temperature interval and the over-current current value, and finally outputs the over-current threshold setting control signal according to the found IGBT over-current current value. The IGBT drive circuit unit outputs an IGBT drive signal to control the conduction or turn-off of the IGBT according to the processed over-temperature protection signal and the drive control signal, and the specific process comprises the following steps:

2. The PFC circuit based IGBT circuit protection apparatus according to claim 1, wherein, ​ The temperature hysteresis protection circuit unit compares the first voltage signal with a first upper threshold value and a first lower threshold value respectively, and if the first voltage signal is greater than or equal to the first upper threshold value, the over-temperature protection signal jumps from a high level signal to a low level signal, the low level over-temperature protection signal is valid, and the low level signal forcibly pulls down the drive control signal, at this time, the IGBT drive circuit unit outputs a low level signal to control the IGBT to be turned off, and the IGBT hardware over-temperature protection is triggered; after the microcontroller unit detects that the over-temperature protection signal is valid, the microcontroller unit stops generating a PWM signal of a next IGBT switching period, and the current PWM signal remains at a low level, and the IGBT software over-temperature protection is triggered.

3. The PFC circuit based IGBT circuit protection apparatus according to claim 2, wherein, After the over-temperature protection is triggered, the IGBT stops working, and the temperature of the IGBT body decreases; if the first voltage signal decreases to be less than or equal to the first lower threshold value, the over-temperature protection signal jumps from a low level to a high level, the high level over-temperature protection signal is invalid, and the IGBT hardware over-temperature protection is exited; after the microcontroller unit detects that the over-temperature protection signal is invalid, the IGBT software over-temperature protection is exited, and the microcontroller outputs a next switching period and a subsequent PWM pulse control signal according to a current state, at this time, the IGBT drive circuit unit controls the IGBT to be turned on or turned off according to the PWM pulse control signal.

4. The PFC circuit based IGBT circuit protection apparatus according to claim 1, wherein, The microcontroller unit is further configured to output a drive control signal to the IGBT drive circuit unit according to the received first voltage signal, second voltage signal, processed over-current protection signal and processed over-temperature protection signal.

5. The PFC circuit based IGBT circuit protection apparatus according to claim 4, wherein, The IGBT drive circuit unit is further configured to output an IGBT drive signal to control the IGBT to be turned on or turned off according to the processed over-temperature protection signal, processed over-current protection signal and drive control signal.

6. The PFC circuit based IGBT circuit protection apparatus according to claim 5, wherein, The IGBT drive circuit unit outputs an IGBT drive signal to control the IGBT to be turned on or turned off according to the processed over-temperature protection signal, processed over-current protection signal and drive control signal, and specifically includes the following steps: The current threshold setting comparison circuit unit compares the second voltage signal with an IGBT over-current protection threshold value, and if the second voltage signal is greater than or equal to the over-current protection threshold value signal, the over-current protection signal jumps from a high level signal to a low level signal, the low level over-current protection signal is valid, and the low level signal forcibly pulls down the drive control signal, at this time, the IGBT drive circuit unit outputs a low level signal to control the IGBT to be turned off, and the IGBT hardware over-current protection is triggered; after the microcontroller unit detects that the over-current protection signal is valid, the IGBT software over-current protection is triggered, the microcontroller unit stops generating a PWM signal of a next IGBT switching period, and the current PWM signal remains at a low level, a holding time is set by software, and after the holding time ends, the IGBT over-current protection of this time is ended. Or the temperature hysteresis protection circuit unit compares the first voltage signal with the first upper threshold and the first lower threshold respectively, if the first voltage signal is greater than or equal to the first upper threshold, the over-temperature protection signal jumps from high level signal to low level signal, the low level over-temperature protection signal is effective, the low level signal forcibly pulls down the drive control signal, at this time the IGBT drive circuit unit outputs low level signal to control IGBT to turn off, triggering IGBT hardware over-temperature protection; After the microcontroller unit detects that the over-temperature protection signal is effective, it stops generating the next IGBT switching cycle PWM signal, and the current PWM signal remains low level, triggering IGBT software over-temperature protection.

7. The PFC circuit based IGBT circuit protection apparatus according to any one of claims 1 to 6, wherein The current threshold setting comparison circuit unit includes two-stage comparator structure, the first stage comparator compares the second voltage signal with the over-current protection threshold signal, the second stage comparator sets the second upper threshold and the second lower threshold, compares the first stage comparator output signal with the second upper threshold and the second lower threshold, and outputs the over-current protection signal.

8. The PFC circuit based IGBT circuit protection apparatus according to claim 7, wherein, When the first stage comparator output signal decreases from high level to less than or equal to the second lower threshold, the second stage comparator outputs the over-current protection signal from high level to low level immediately, and remains low level; When the first stage comparator output signal increases from low level to greater than or equal to the second upper threshold, the second stage comparator outputs the over-current protection signal from low level to high level immediately, and remains high level.

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