CN109004620A - A kind of IGBT current foldback circuit and air conditioner - Google Patents

Abstract

The present invention provides an IGBT overcurrent protection circuit and an air conditioner. An IGBT overcurrent protection circuit includes a current sampling unit, a protection unit, a drive unit and a control unit, wherein the current sampling unit is connected to the switching tube respectively. The emitter of the power factor correction circuit, the negative pole of the DC side of the rectifier bridge in the power factor correction circuit, and the input terminal of the protection unit are connected, and the output terminal of the protection unit is divided into two circuits, one of which is connected to the input terminal of the control unit, The other path is connected to the input terminal of the driving unit through a wire, the output terminal of the control unit is connected to the input terminal of the driving unit, and the output terminal of the driving unit is connected to the gate of the switching tube. In this way, when the power factor correction circuit is over-current, the IGBT over-current protection circuit will generate hardware protection, thereby realizing more timely and effective protection for the switching tube.

Description

A kind of IGBT overcurrent protection circuit and air conditioner

technical field

The invention relates to the technical field of air conditioners, in particular to an IGBT overcurrent protection circuit and an air conditioner.

Background technique

Inverter air conditioners generally add active power factor correction (Power Factor Correction, power factor correction) control technology in order to improve the power factor, and at the same time adjust harmonic currents to reduce the impact of air conditioners on the power grid. However, the active power factor correction control scheme is relatively complicated. Improper control can easily cause overcurrent and overheating and burn down the IGBT (Insulated Gate Bipolar Transistor). Usually, a protection device is added to the circuit to improve the performance of the circuit. reliability. The existing technology basically uses the combination of software and hardware. The hardware detects the conduction current of the IGBT. When it exceeds the threshold value set by the overcurrent, it triggers the single-chip microcomputer, and then the single-chip microcomputer sends a signal to stop the power factor correction. MCU software settings, control timing, logic unreasonable or poor MCU anti-interference, protection delay or loss of control may occur, resulting in IGBT burnout, resulting in failure of the air conditioner.

Contents of the invention

In view of this, the present invention aims to provide an IGBT overcurrent protection circuit to solve the problem that the IGBT is easily burned due to the overcurrent of the PFC circuit.

In order to achieve the above object, technical solution of the present invention is achieved in that way:

An IGBT overcurrent protection circuit is used for overcurrent protection of a switch tube in a power factor correction circuit, including a current sampling unit, a protection unit, a drive unit and a control unit; wherein,

The current sampling unit is respectively connected to the emitter of the switching tube, the negative pole of the DC side of the rectifier bridge in the power factor correction circuit, and the input terminal of the protection unit, and the current sampling unit is connected to the power factor correction circuit sampling the output current to obtain a sampling current, and delivering the sampling current to the input terminal of the protection unit;

The protection unit is used to convert the sampling current into a sampling voltage and compare it with a reference voltage to output a detection signal; the output terminal of the protection unit is divided into two circuits, one of which is connected to the input terminal of the control unit, and the other One path is connected to the input end of the drive unit through a wire;

The output end of the control unit is connected to the input end of the drive unit, and the control unit outputs a control signal to control the drive unit according to the detection signal output by the protection unit;

The output terminal of the driving unit is connected to the gate of the switching tube, and the driving unit is used to control the conduction and switching of the switching tube according to the detection signal output by the protection unit and the control signal output by the control unit. off.

Further, the protection unit includes a first comparison circuit, and the first comparison circuit includes a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a first comparator, a first DC power supply , the first comparator includes a first input terminal and a second input terminal; the first input terminal of the first comparator is divided into two paths, one path is grounded through the fourth resistor, and the other path is grounded through the second The resistor is connected to the first DC power supply; the second input terminal of the first comparator is divided into two paths, and one path is respectively connected to the negative pole of the DC side of the rectifier bridge and the current sampling unit through the third resistor. The other path is connected to the first DC power supply through the first resistor; the output terminal of the first comparator is respectively connected to the input terminal of the control unit, the input terminal of the driving unit, and the first DC power supply. One end of the five resistors is connected; the other end of the fifth resistor is connected to the power supply.

Further, the protection unit also includes a self-locking circuit to prevent the output of the first comparator from flipping twice, the input terminal of the self-locking circuit is connected to the output terminal of the first comparator, and the self-locking circuit The output terminal of the lock circuit is connected with the first input terminal of the first comparator, and the self-lock circuit is a one-way conduction circuit.

Further, the protection unit also includes a start-up circuit to unlock the circuit from the self-locking circuit, the input end of the start-up circuit is connected to the output end of the first comparator, and the output end of the start-up circuit It is connected with the signal output port of the control unit.

Further, the self-locking circuit includes a first diode, the cathode of the first diode is connected to the first input terminal of the first comparator, and the anode is connected to the output terminal of the first comparator .

Further, the startup circuit includes a second diode, the anode of the second diode is connected to the output terminal of the first comparator, and the cathode is connected to the signal output port of the control unit.

Further, the protection unit further includes a second comparison circuit, the second comparison circuit includes a second comparator, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, and a second DC power supply, and the first The second comparator includes a first input terminal and a second input terminal; the second input terminal of the second comparator is connected to the output terminal of the first comparator, and the first input terminal of the second comparator is divided into Two paths, one path is grounded through the seventh resistor, and the other path is connected to the second DC power supply through the sixth resistor; the output terminal of the second comparator is divided into two paths, one path is connected to the second DC power supply through the eighth resistor It is connected to the power supply, and the other is connected to one end of the ninth resistor; the other end of the ninth resistor is respectively connected to the input end of the control unit and the input end of the drive unit.

Further, the protection unit further includes a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, and a fifth capacitor, the first capacitor, the second capacitor, the third capacitor, the first capacitor Four capacitors, one end of the fifth capacitor are all grounded, the other end of the first capacitor is connected to the second output end of the first comparator, and the other end of the second capacitor is connected to the first comparator connected to the first input end of the third capacitor, the other end of the third capacitor is connected to the output end of the first comparator, and the other end of the fourth capacitor is connected to the first input end of the second comparator, so The other end of the fifth capacitor is connected to the ninth resistor.

Further, the current sampling circuit includes a sampling resistor, one end of which is connected to the negative pole of the DC side of the rectifier bridge and the third resistor, and the other end is connected to the emitter of the switching tube and grounded.

Compared with the prior art, the IGBT overcurrent protection circuit of the present invention has the following advantages:

In the IGBT overcurrent protection circuit of the present invention, the output end of the protection unit is divided into two paths, one path is connected to the input end of the control unit, and the other path is connected to the input end of the drive unit through a wire. When the factor correction circuit is overcurrent, the IGBT overcurrent protection circuit will first generate hardware protection, and the response time of the hardware protection is shorter than the response time of the software protection, so as to realize more timely and effective protection for the switch tube, so that the switch tube will not be damaged due to The power factor correction circuit is damaged due to overcurrent, which realizes the overcurrent protection of the switch tube, improves the stability of the circuit, and has higher reliability.

Another object of the present invention is to provide an air conditioner to solve the problem that the IGBT in the existing air conditioner is easily burned due to the overcurrent of the PFC circuit.

In order to achieve the above object, technical solution of the present invention is achieved in that way:

An air conditioner includes the above-mentioned IGBT overcurrent protection circuit.

Compared with the prior art, the air conditioner has the same advantages as the above-mentioned IGBT overcurrent protection circuit, which will not be repeated here.

Description of drawings

The drawings constituting a part of the present invention are used to provide a further understanding of the present invention, and the schematic embodiments and descriptions of the present invention are used to explain the present invention, and do not constitute an improper limitation of the present invention. In the attached picture:

Fig. 1 is the schematic diagram of the IGBT overcurrent protection circuit described in the embodiment of the present invention;

2 is a circuit diagram of a power factor correction circuit, a sampling unit and a protection unit according to an embodiment of the present invention;

FIG. 3 is a circuit diagram of a driving unit according to an embodiment of the present invention.

Explanation of reference signs:

10-power factor correction circuit, 20-current sampling unit, 30-protection unit, 301-first comparison circuit, 302-self-locking circuit, 303-starting circuit, 304-second comparison circuit, 40-drive unit, 401- Driver chip, 50-control unit, IGBT-switch tube, AC-AC power supply, BG1-rectifier bridge, L-inductor, C1-first capacitor, C2-second capacitor, C3-third capacitor, C4-fourth capacitor , C5-fifth capacitor, D1-first diode, D2-second diode, D3-third diode, D4-fourth diode, E1, E2-electrolytic capacitor, VCC-first DC power supply, VD-second DC power supply, R1-first resistor, R2-second resistor, R3-third resistor, R4-fourth resistor, R5-fifth resistor, R6-sixth resistor, R7-first Seventh resistor, R8-eighth resistor, R9-ninth resistor, R10-tenth resistor, R11-eleventh resistor, R12-twelfth resistor, R13-thirteenth resistor, R14-fourteenth resistor, R15 - Fifteenth resistor, R61 - sampling resistor, IC1A - first comparator, IC1B - second comparator, CLR - signal output port, ZD1 - Zener diode.

Detailed ways

It should be noted that, in the case of no conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

The present invention will be described in detail below with reference to the accompanying drawings and examples.

Example 1

As shown in FIG. 1 , it is a schematic diagram of the IGBT overcurrent protection circuit in this embodiment; wherein, the IGBT overcurrent protection circuit includes a current sampling unit 20 , a protection unit 30 , a driving unit 40 and a control unit 50 .

As shown in FIG. 2 , the current sampling unit 20 is respectively connected to the emitter of the switching tube IGBT, the negative pole of the DC side of the rectifier bridge BG1 in the power factor correction circuit 10, and the input terminal of the protection unit 30. The current sampling unit 20 is connected to the power factor correction circuit. The output current of 10 is sampled to obtain a sampled current, and the sampled current is sent to the input terminal of the protection unit 30 .

The protection unit 30 is used to convert the sampling current into a sampling voltage and compare it with a reference voltage to output a detection signal; the output terminal of the protection unit 30 is divided into two circuits, one channel PWM_EN is connected to the input terminal of the control unit 50, and the other channel IPM_FO It is connected to the input terminal of the driving unit 40 through a wire.

The output terminal PFC_PWM of the control unit 50 is connected to the input terminal of the driving unit 40 , and the control unit 50 outputs a control signal to control the driving unit 40 according to the detection signal output by the protection unit 30 .

The output terminal IGBT_Driver of the driving unit 40 is connected to the gate of the switching tube IGBT. The driving unit 40 is used to control the switching on and off of the switching tube IGBT according to the detection signal output by the protection unit 30 and the control signal output by the control unit 50 .

If the control signal in the power factor correction circuit 10 is abnormal or the detection signal is abnormal due to power grid surge or excessive voltage, after the drive unit 40 receives the detection signal directly transmitted by the protection unit 30 through the wire, it will cut off the output to the switch tube 1 in time. The driving signal of the GBT grid is used to turn off the switch tube I GBT, thereby realizing the hardware protection of the switch tube I GBT; and, after the control unit 50 receives the detection signal transmitted by the protection unit 30, it performs signal processing on the detection signal , outputting a control signal to the driving unit 40 to control the driving unit 40 to stop outputting the driving signal to the gate of the switching tube IGBT, so as to realize the software protection of the switching tube IGBT.

In this way, since the output terminal of the protection unit 30 is directly connected to the input terminal of the drive unit 40 through a wire, when the power factor correction circuit 10 is overcurrent, the IGBT overcurrent protection circuit first generates hardware protection, and the response time of the hardware protection is shorter than that of the software protection. The response time is short, so that the switch tube IGBT can be protected more timely and effectively, so that the switch tube IGBT will not be damaged due to the overcurrent of the power factor correction circuit 10, and the stability of the circuit is improved, and the reliability is higher.

Example 2

As the above-mentioned IGBT overcurrent protection circuit, the difference of this embodiment is that, as shown in FIG. , the fourth diode D4, the electrolytic capacitor E1, and the electrolytic capacitor E2. The first AC input terminal of the rectifier bridge BG1 is connected to the neutral terminal ACN of the AC power supply AC, and the second AC input terminal of the rectifier bridge BG1 is connected to the phase terminal ACL of the AC power supply AC. The anode of the DC side of the rectifier bridge BG1 is connected to one end of the inductor L, and the other end of the inductor L is divided into two paths, one path is connected to the collector of the switching tube IGBT, and the other path is connected to the anode of the fourth diode D4. The cathode of the fourth diode D4 is the output terminal of the power factor correction circuit 10 , and the electrolytic capacitor E1 and the electrolytic capacitor E2 are both connected between the cathode of the fourth diode D4 and the ground.

Example 3

As the above-mentioned IGBT overcurrent protection circuit, the difference of this embodiment is that, as shown in FIG. R2, the third resistor R3, the fourth resistor R4, the fifth resistor R5, the first comparator IC1A, and the first DC power supply VCC.

The first comparator IC1A includes a first input terminal and a second input terminal. The first input terminal of the first comparator IC1A is divided into two paths, one path is grounded through the fourth resistor R4, and the other path is connected to the first direct path through the second resistor R2. The current power supply VCC is connected. The second input end of the first comparator IC1A is divided into two paths, one path is respectively connected to the negative pole of the DC side of the rectifier bridge BG1 and the current sampling unit 20 via the third resistor R3, and the other path is connected to the first DC power supply via the first resistor R1 VCC is connected. The output terminal of the first comparator IC1A is respectively connected with the input terminal of the control unit 50 , the input terminal of the driving unit 40 , and one terminal of the fifth resistor R5 . The other end of the fifth resistor R5 is connected to the power supply.

In this embodiment, the current sampling unit 20 is preferably a sampling resistor R61, and the resistance of the sampling resistor R61 is in milliampere level, and the voltage drop is negligible. One end of the sampling resistor R61 is respectively connected to the negative pole of the DC side of the rectifier bridge BG1 and the third resistor R3, and the other end is connected to the emitter of the switching tube IGBT and grounded. Preferably, the first input terminal of the first comparator IC1A is its non-inverting input terminal, and the second input terminal is its inverting input terminal. The first resistor R1 , the second resistor R2 , the third resistor R3 , and the fourth resistor R4 are used as voltage dividing resistors, and the resistor R5 is used as a pull-up resistor at the output terminal of the first comparator IC1A. In this embodiment, the reference voltage Ub=(R4/R4+R2)*VCC at the non-inverting input terminal of the first comparator IC1A, and the reference voltage Ua=(R3/R3+R1)*VCC at the inverting input terminal of the first comparator IC1A , the voltage at the output terminal of the first comparator IC1A is Uf, Uf is the detection signal voltage value, and the reference voltage is set so that Ua is greater than Ub.

When the power factor correction circuit 10 works normally, Ua is greater than Ub, the output terminal voltage Uf of the first comparator IC1A is at low level, and the input terminals of the drive unit 40 and the control unit 50 are both active at low level. The low-level detection signal output by the first comparator IC1A is directly delivered to the input end of the drive unit 40 through the wire, and at the same time, the low-level detection signal output by the first comparator IC1A is sent to the control unit 50, and the control unit 50 performs the detection signal. Processing, after judging that the current does not flow, the control unit 50 outputs a control signal to the input terminal of the driving unit 40 . In this way, the output terminal of the driving unit 40 outputs a driving signal to the gate of the switching tube IGBT to charge the parasitic capacitance of the switching tube IGBT grid, the switching tube IGBT is turned on, and the power factor correction circuit 10 is allowed to work. At this time, the current flowing through the sampling resistor R61 is Iac, the sampling resistor R61 divides the voltage, and the voltage Ua decreases. If Ua is still greater than Ub, the IGBT overcurrent protection circuit will not enter the overcurrent protection, and the power factor correction circuit 10 maintains normal operation.

If the control signal of the power factor correction circuit 10 is abnormal, or the power grid surges or the voltage is too strong, causing Ua to be smaller than Ub, the first comparator IC1A reverses, and the output voltage Uf of the first comparator IC1A is at a high level, so that the protection unit 30 directly passes through the wire Output a high-level detection signal to the input terminal of the drive unit 40, the drive unit 40 stops outputting the drive signal, the switching tube IGBT stops working, and completes the hardware protection of the switching tube IGBT; at the same time, the protection unit 30 outputs a high-level detection signal To the control unit 50, the control unit 50 processes the detection signal, and after judging that the current is over-current, the software turns off the output of the control unit 50 to complete the software protection of the switching tube IGBT. When Ua=Ub, it is at the threshold point of overcurrent protection. Through this threshold point, the overcurrent current Iac=[VCC-(VCC-Ub)/R1*(R3+R1)]/R61 can be calculated.

Example 4

As the above-mentioned IGBT overcurrent protection circuit, the difference of this embodiment is that, as shown in FIG. The input terminal of the lock circuit 302 is connected to the output terminal of the first comparator IC1A, the output terminal of the self-lock circuit 302 is connected to the first input terminal of the first comparator IC1A, and the self-lock circuit 302 is a one-way conduction circuit.

When the control signal of the power factor correction circuit 10 is abnormal or Ua is smaller than Ub due to power grid surge or excessive voltage, the first comparator IC1A is reversed, the output Uf of the first comparator IC1A is high level, and the switch tube IGBT stops working. At this time, the voltage Uf is applied to Ub through the self-locking circuit 302, so that the voltage of Ub is raised, so as to ensure that the first comparator IC1A will not be reversed twice due to the increase of Ua.

In this way, due to the function of the self-locking circuit 302, when the switching tube IGBT in this embodiment stops working due to current overcurrent, the first comparator IC1A will not reverse twice due to the increase of Ua, even if the control unit 50 makes a wrong judgment and does not stop The control signal is output to the input terminal of the drive unit 40, and the switching tube IGBT will not be automatically turned on, so that the IGBT overcurrent protection circuit in this embodiment has a self-locking function, which avoids the switching off of the switching tube IGBT and the output of the control unit 50. There is no runaway state of turning off, and it ensures that the circuit does not oscillate after the switching tube IGBT is turned off.

Example 5

As the above-mentioned IGBT overcurrent protection circuit, the difference of this embodiment is that, as shown in FIG. The input end is connected to the output end of the first comparator IC1A, and the output end of the starting circuit 303 is connected to the signal output port CLR of the control unit 50 .

After the switch tube IGBT is protected, if it is to be turned on again, the signal output port CLR port of the control unit 50 can output a low-level signal, Uf is discharged through the starting circuit 303, and the Uf level is pulled down, which can ensure that the Ub voltage returns to The initial reference point, and then the signal output port CLR turns to high level again, the switch tube IGBT can be turned on, and the power factor correction circuit 10 can work again.

In this way, after the switching tube IGBT overcurrent protection in this embodiment, if you want to turn it on again, you can directly unlock the function through software, and the protection time can be freely adjusted by software, so that the protection time of the IGBT overcurrent protection circuit in this embodiment can be freely Adjustment.

Example 6

Like the above-mentioned IGBT overcurrent protection circuit, the difference of this embodiment is that, as shown in FIG. 2, the self-locking circuit 302 includes a first diode D1, and the cathode of the first diode D1 is compared with the The first input terminal of the comparator IC1A is connected, and the anode is connected with the output terminal of the first comparator IC1A.

In this embodiment, after the switching tube IGBT stops working, the voltage Uf is directly applied to Ub through the first diode D1, so that the voltage of Ub is raised to ensure that the first comparator IC1A will not be flipped twice due to the increase of Ua.

In this way, due to the unidirectional conduction of the first diode D1, the voltage Uf can only be applied to Ub through the first diode D1, which ensures the stability of the circuit. And when the first diode D1 is turned on, the resistance is very small, the voltage drop when the voltage Uf passes through the first diode D1 is small, the voltage applied to Ub is larger, and the voltage of Ub is raised higher, and the self-locking circuit 302 The self-locking function is stronger.

Example 7

Like the IGBT overcurrent protection circuit described above, the difference of this embodiment is that, as shown in FIG. The output terminal of IC1A is connected, and the cathode is connected with the signal output port CLR of the control unit 50 .

In this implementation, after the switch tube IGBT is protected, if it is to be turned on again, the signal output port CLR port of the control unit 50 outputs a low-level signal, and Uf is directly discharged through the second diode D2, because the second diode D2 When it is turned on, the resistance is very small, and the resistance to the current is very small. The discharge speed of Uf is faster, and the level is pulled down faster, which can ensure that the Ub voltage quickly returns to the initial reference point, and the startup circuit 303 releases the self-locking circuit 302 The locking of the circuit is faster.

Example 8

As the above-mentioned IGBT overcurrent protection circuit, the difference of this embodiment is that, as shown in FIG. The sixth resistor R6, the seventh resistor R7, the eighth resistor R8, the ninth resistor R9, and the second DC power supply VDD. The second comparator IC1B includes a first input terminal and a second input terminal, the second input terminal of the second comparator IC1B is connected with the output terminal of the first comparator IC1A, and the first input terminal of the second comparator IC1B is divided into two One path is grounded through the seventh resistor R7, and the other path is connected to the second DC power supply VDD through the sixth resistor R6; the output terminal of the second comparator IC1B is divided into two paths, one path is connected to the power supply through the eighth resistor R8, and the other One path is connected to one end of the ninth resistor R9; the other end of the ninth resistor R9 is connected to the input end of the control unit 50 and the input end of the driving unit 40 respectively.

The sixth resistor R6 and the seventh resistor R7 are used as voltage dividing resistors, the eighth resistor R8 is used as a pull-up resistor at the output terminal of the second comparator IC1B, and the ninth resistor R9 is used as a current limiting resistor at the output terminal of the second comparator IC1B.

In many cases, when the power factor correction circuit 10 is working normally, the output of the first comparator IC1A is low level, and when the circuit is over-current, the output of the first comparator IC1A is high level. And when both the control unit 50 and the drive unit 40 are active at the high level of the input terminal, and the input high level outputs the high level, the high level detection signal output by the first comparator IC1A will cause the control unit 50 and the drive unit 40 to output a high level. level, the purpose of turning off the switching tube IGBT cannot be achieved. In this embodiment, when the current of the power factor correction circuit 10 is overcurrent, the second comparison circuit 304 can convert the high-level detection signal output by the first comparator IC1A into a low-level detection signal, so that the control unit 50 and the drive The unit 40 outputs a low level to achieve the purpose of turning off the switching tube IGBT.

In this embodiment, preferably, the first input terminal of the second comparator IC1B is its non-inverting input terminal, and the second input terminal is its inverting input terminal. The voltage at the inverting input terminal of comparator IC1B is Uf, and the reference voltage Ud at the same input terminal of comparator IC1B=(R7/R7+R6)*VDD. The reference voltage is set so that Ua is greater than Ub, and Uf is greater than Ud when Uf is at a high level. When the power factor correction circuit 10 works normally, Ua is greater than Ub, the comparator IC1A output voltage Uf is low level, Uf is less than Ud, and the output terminal of the comparator IC1B outputs a high level detection signal; when the circuit is overcurrent, the comparator IC1A outputs The voltage Uf is high level; Uf is greater than Ud, the comparator IC1B reverses, and the comparator IC1B outputs a low level detection signal.

In this way, due to the function of the second comparison circuit 304 , when the user selects the control unit 50 and the driving unit 40 that work together with the protection circuit 30 in this embodiment, the selection range is wider and the degree of freedom is higher.

Example 9

The difference between this embodiment and the above-mentioned IGBT overcurrent protection circuit is that, as shown in FIG. 2 , the protection unit 30 further includes a first capacitor C1, a second capacitor C2, a third capacitor C3, and a fourth capacitor C4. , the fifth capacitor C5, one end of the first capacitor C1, the second capacitor C2, the third capacitor C3, the fourth capacitor C4, and the fifth capacitor C5 are all grounded, and the other end of the first capacitor C1 is connected to the first comparator IC1A. The two output ends are connected, the other end of the second capacitor C2 is connected with the first input end of the first comparator IC1A, the other end of the third capacitor C3 is connected with the output end of the first comparator IC1A, and the other end of the fourth capacitor C4 It is connected with the first input terminal of the second comparator IC1B, and the other terminal of the fifth capacitor C5 is connected with the ninth resistor R9.

The first capacitor C1, the second capacitor C2, the third capacitor C3, the fourth capacitor C4, and the fifth capacitor C5 are all used as filter capacitors. Through calculation and selection of appropriate capacitor values, the interference of some noise signals to the circuit can be filtered out, allowing the detection The signal is closer to the real value, avoiding false triggers caused by noise signals. The reliability of the circuit is higher.

Example 10

Like the IGBT overcurrent protection circuit described above, the difference of this embodiment is that, as shown in FIG. 3 , the driving unit 40 includes a driving chip 401 , a tenth resistor R10 , and an eleventh resistor R11 . The input terminal of the driver chip 401 is divided into three routes, one route is connected to the output terminal PFC_PWM of the control unit 50 through the tenth resistor R10, one route is connected to the output terminal of the protection unit 30 through the eleventh resistor R11, and the other route is connected to the output terminal of the protection unit 30; The output end is connected with the gate of the switching tube IGBT.

In this embodiment, the preferred driver chip 401 is a dual-channel low-voltage driver chip IR4427, and the chip IR4427 includes 8 pins: NC, NC, INA, OA, GND, Vcc, INB, OB. Among them, pins INA and INB are two input ports, pins OA and OB are two output ports, pin INA corresponds to pin OA, pin INB corresponds to pin OB, pins INA and INB are both high efficient. When pins INA and INB are at high level, pins OA and OB output high level; when pins INA and INB are at low level, pins OA and OB output low level. In this embodiment, the driving unit 40 further includes a sixth capacitor C6 and a seventh capacitor C7.

Both the pins INA and INB are connected to the output terminal PFC_PWM of the control unit 50 through the tenth resistor R10 , both are grounded through the eleventh resistor R11 , and are connected to the output terminal of the protection unit 30 . The sixth capacitor C6 is connected in parallel with the eleventh resistor R11, one end of the seventh capacitor C7 is grounded, and the other end is respectively connected to the Vcc pin of the IR4427 and the DC power supply. Both the pins OA and OB are connected to the gate of the switching tube IGBT. The tenth resistor R10 is used as a current limiting resistor, the eleventh resistor R11 is used as a voltage dividing resistor, and the sixth capacitor C6 and the seventh capacitor C7 are filter capacitors.

When the power factor correction circuit 10 works normally, the inputs of the pins INA and INB are both high level, so the pins OA and OB both output high level to charge the parasitic capacitance of the switch tube IGBT grid, and the switch tube IGBT is turned on When the power factor correction circuit 10 is overcurrent, the inputs of the pins INA and INB are all low level, so that the pins OA and OB all output low level, and the charge stored in the parasitic capacitance of the switching tube IGBT grid is discharged, and the switch The tube IGBT is turned off.

Example 11

As the above-mentioned IGBT overcurrent protection circuit, the difference of this embodiment is that, as shown in FIG. 3 , the driving unit 40 further includes a twelfth resistor R12 , a thirteenth resistor R13 , and a fourteenth resistor R14 . One end of the parallel connection of the thirteenth resistor R13 and the fourteenth resistor R14 is respectively connected to the pins OA and OB of the driver chip 401 through the twelfth resistor R12 , and the other end is connected to the gate of the switching tube IGBT.

In this embodiment, both the thirteenth resistor R13 and the fourteenth resistor R14 are used as current limiting resistors. When the power factor correction circuit 10 works normally, the protection unit 30 outputs a high level to the input terminal of the chip IR4427, and the output pin of the chip IR4427 outputs a high level to charge the gate parasitic capacitance of the switching tube IGBT, and the twelfth resistor R12 can be Adjust the charging speed of the gate parasitic capacitance of the switching tube IGBT to avoid burning the switching tube IGBT due to too fast charging.

Example 12

As the above-mentioned IGBT overcurrent protection circuit, the difference of this embodiment is that, as shown in FIG. The pins OA and OB are connected, and the anode is connected to the common terminal of the twelfth resistor R12, the thirteenth resistor R13 and the fourteenth resistor R14.

When the switching tube IGBT is turned off, the drive unit 40 outputs a low level, since the voltage drop of the third diode D3 is smaller than the voltage drop generated on the twelfth resistor R12 by the same driving off current, the gate capacitance of the switching tube IGBT The stored charges are rapidly discharged through the third diode D3.

In this way, due to the function of the third diode D3, the switch tube IGBT can be turned off quickly when the circuit is over-current in this embodiment, the protection speed is faster, and the loss of the circuit is reduced.

Example 13

As the above-mentioned IGBT overcurrent protection circuit, the difference of this embodiment is that, as shown in FIG. 3 , the drive unit 40 also includes a Zener diode ZD1 and a fifteenth resistor R15, and the anode of the Zener diode ZD1 is grounded. The cathode is connected to the grid of the switching tube IGBT, the common terminal of the thirteenth resistor R13 and the fourteenth resistor R14, and the fifteenth resistor R15 is connected between the grid of the switching tube IGBT and the ground.

In the switching tube IGBT, the insulation resistance between the gate, the drain and the source of the MOS tube is very high, and the insulating layer is very thin. The gate is easy to accumulate charges to break down the insulating layer and damage the MOS tube. High voltage applied to the gate will also break down the insulating layer and damage the MOS tube. In this embodiment, the gate of the switching tube IGBT is connected in parallel with the Zener diode ZD1, which can limit the gate voltage to be below the voltage regulation value of the Zener diode ZD1, and prevent the gate of the switching tube IGBT from being broken down. The fifteenth resistor R15 acts as a pull-down resistor, which can release the static charge on the gate, prevent the charge from accumulating, and prevent the gate of the switching tube IGBT from being broken down by static electricity.

Example 14

This embodiment provides an air conditioner, including the IGBT overcurrent protection circuit described in any one of the above embodiments. In this way, due to the function of the IGBT overcurrent protection circuit, the air conditioner in this embodiment has a better protection effect on the switching tube IGBT and a faster protection speed.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of the present invention. within the scope of protection.

Claims (10)

1. An IGBT overcurrent protection circuit is used for carrying out overcurrent protection on a switching tube (IGBT) in a power factor correction circuit (10), and is characterized by comprising a current sampling unit (20), a protection unit (30), a driving unit (40) and a control unit (50); wherein,

the current sampling unit (20) is respectively connected with an emitter of the switching tube (IGBT), a negative electrode of a direct current side of a rectifier bridge (BG1) in the power factor correction circuit (10) and an input end of the protection unit (30), the current sampling unit (20) samples output current of the power factor correction circuit (10), obtains sampling current, and transmits the sampling current to the input end of the protection unit (30);

the protection unit (30) is used for converting the sampling current into sampling voltage, comparing the sampling voltage with reference voltage and outputting a detection signal; the output end of the protection unit (30) is divided into two paths, one path is connected with the input end of the control unit (50), and the other path is connected with the input end of the drive unit (40) through a lead;

the output end of the control unit (50) is connected with the input end of the driving unit (40), and the control unit (50) outputs a control signal to control the driving unit (40) according to the detection signal output by the protection unit (30);

the output end of the driving unit (40) is connected with the grid electrode of the switch tube (IGBT), and the driving unit (40) is used for controlling the switch tube (IGBT) to be switched on and off according to the detection signal output by the protection unit (30) and the control signal output by the control unit (50).

2. The IGBT overcurrent protection circuit of claim 1, wherein the protection unit (30) comprises a first comparison circuit (301), the first comparison circuit (301) comprises a first resistor (R1), a second resistor (R2), a third resistor (R3), a fourth resistor (R4), a fifth resistor (R5), a first comparator (IC1A), a first direct current power supply (VCC), and the first comparator (IC1A) comprises a first input terminal and a second input terminal; a first input end of the first comparator (IC1A) is divided into two paths, one path is grounded through the fourth resistor (R4), and the other path is connected with a first direct current power supply (VCC) through the second resistor (R2); a second input end of the first comparator (IC1A) is divided into two paths, one path is respectively connected with a negative electrode of a direct current side of the rectifier bridge (BG1) and the current sampling unit (20) through the third resistor (R3), and the other path is connected with a first direct current power supply (VCC) through the first resistor (R1); the output end of the first comparator (IC1A) is respectively connected with the input end of the control unit (50), the input end of the driving unit (40) and one end of the fifth resistor (R5); the other end of the fifth resistor (R5) is connected with a power supply.

3. The IGBT overcurrent protection circuit of claim 2, wherein the protection unit (30) further comprises a self-locking circuit (302) to prevent the output of the first comparator (IC1A) from flipping twice, the input terminal of the self-locking circuit (302) is connected to the output terminal of the first comparator (IC1A), the output terminal of the self-locking circuit (302) is connected to the first input terminal of the first comparator (IC1A), and the self-locking circuit (302) is a unidirectional conduction circuit.

4. The IGBT overcurrent protection circuit according to claim 2, wherein the protection unit (30) further comprises a start circuit (303) to unlock the self-locking circuit (302) from the circuit, an input terminal of the start circuit (303) is connected to an output terminal of the first comparator (IC1A), and an output terminal of the start circuit (303) is connected to the signal output port (CLR) of the control unit (50).

5. The IGBT overcurrent protection circuit according to claim 2, characterized in that the self-locking circuit (302) comprises a first diode (D1), a cathode of the first diode (D1) being connected to a first input of the first comparator (IC1A), and an anode of the first diode being connected to an output of the first comparator (IC 1A).

6. The IGBT overcurrent protection circuit of claim 4, wherein the start-up circuit (303) comprises a second diode (D2), an anode of the second diode (D2) being connected to the output of the first comparator (IC1A), and a cathode of the second diode being connected to the signal output (CLR) of the control unit (50).

7. The IGBT overcurrent protection circuit according to any one of claims 2-6, wherein the protection unit (30) further comprises a second comparison circuit (304), the second comparison circuit (304) comprises a second comparator (IC1B), a sixth resistor (R6), a seventh resistor (R7), an eighth resistor (R8), a ninth resistor (R9), a second direct current power supply (VDD), and the second comparator (IC1B) comprises a first input terminal and a second input terminal; a second input end of the second comparator (IC1B) is connected with an output end of the first comparator (IC1A), a first input end of the second comparator (IC1B) is divided into two paths, one path is grounded through the seventh resistor (R7), and the other path is connected with the second direct current power supply (VDD) through the sixth resistor (R6); the output end of the second comparator (IC1B) is divided into two paths, one path is connected with the power supply through the eighth resistor (R8), and the other path is connected with one end of the ninth resistor (R9); the other end of the ninth resistor (R9) is respectively connected with the input end of the control unit (50) and the input end of the driving unit (40).

8. The IGBT overcurrent protection circuit of claim 7, wherein the protection unit (30) further comprises a first capacitor (C1), a second capacitor (C2), a third capacitor (C3), a fourth capacitor (C4), and a fifth capacitor (C5), wherein one end of each of the first capacitor (C1), the second capacitor (C2), the third capacitor (C3), the fourth capacitor (C4), and the fifth capacitor (C5) is grounded, the other end of the first capacitor (C1) is connected to the second output terminal of the first comparator (IC1A), the other end of the second capacitor (C2) is connected to the first input terminal of the first comparator (IC1A), the other end of the third capacitor (C3) is connected to the output terminal of the first comparator (IC1A), and the other end of the fourth capacitor (C4) is connected to the first input terminal of the second comparator (IC1B), the other end of the fifth capacitor (C5) is connected with the ninth resistor (R9).

9. The IGBT overcurrent protection circuit according to any one of claims 2-8, wherein the current sampling circuit comprises a sampling resistor (R61), one end of the sampling resistor (R61) is respectively connected with the negative electrode of the direct current side of the rectifier bridge (BG1) and the third resistor (R3), and the other end of the sampling resistor is connected with the emitter of the switching tube (IGBT) and is grounded.

10. An air conditioner characterized by comprising the IGBT overcurrent protection circuit according to any one of claims 1 to 9.