CN208707290U

CN208707290U - A kind of IGBT current foldback circuit and air conditioner

Info

Publication number: CN208707290U
Application number: CN201821460174.6U
Authority: CN
Inventors: 赵新荣; 薄传海; 孙海波; 熊刚
Original assignee: Aux Air Conditioning Co Ltd
Current assignee: Aux Air Conditioning Co Ltd
Priority date: 2018-09-07
Filing date: 2018-09-07
Publication date: 2019-04-05
Anticipated expiration: 2028-09-07

Abstract

The utility model provides a kind of IGBT current foldback circuit and air conditioner, a kind of IGBT current foldback circuit, including current sampling unit, protection location, driving unit and control unit, wherein, the current sampling unit emitter with the switching tube respectively, the DC side cathode of rectifier bridge in the circuit of power factor correction, the input terminal of the protection location is connected, the output end of the protection location is divided into two-way, it is connected all the way with the input terminal of described control unit, another way is connected by a conducting wire with the input terminal of the driving unit, the output end of described control unit is connected with the input terminal of the driving unit, the output end of the driving unit is connected with the grid of the switching tube.In this way, the IGBT current foldback circuit can generate hardware protection in circuit of power factor correction overcurrent, the switching tube more in time, is more effectively protected to realize.

Description

IGBT over-current protection circuit and air conditioner

Technical Field

The utility model relates to an air conditioner technical field, in particular to IGBT overcurrent protection circuit and air conditioner.

Background

The inverter air conditioner generally increases the active Power Factor Correction (Power Factor Correction) control technology to improve the Power Factor, adjust the harmonic current simultaneously, reduce the influence of air conditioner to the electric wire netting. However, the active power factor correction control scheme is relatively complex, overcurrent and overheating are easily generated due to improper control, so that an Insulated Gate Bipolar Transistor (IGBT) is burnt, and a protection device is usually added in a circuit to improve the reliability of the circuit. In the prior art, a mode of combining software and hardware is basically adopted, the hardware detects the on-current of an IGBT, when the on-current exceeds a threshold value set by overcurrent, a singlechip is triggered, then the singlechip sends a signal to stop power factor correction, and if the software setting and the control sequence and the logic of the singlechip are unreasonable or the singlechip is poor in anti-interference performance, protection delay or runaway can occur, the IGBT is burnt, and the air conditioner fails.

SUMMERY OF THE UTILITY MODEL

In view of this, the utility model aims at providing an IGBT overcurrent protection circuit to solve the easy problem of burning out because of the PFC circuit overflows of IGBT.

In order to achieve the above purpose, the technical scheme of the utility model is realized like this:

an IGBT overcurrent protection circuit is used for carrying out overcurrent protection on a switching tube in a power factor correction circuit and comprises a current sampling unit, a protection unit, a driving unit and a control unit; wherein,

the current sampling unit is respectively connected with an emitter of the switching tube, a direct-current side cathode of a rectifier bridge in the power factor correction circuit and an input end of the protection unit, and samples the output current of the power factor correction circuit to obtain a sampling current and transmits the sampling current to the input end of the protection unit;

the protection unit 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 is divided into two paths, one path is connected with the input end of the control unit, and the other path is connected with the input end of the driving unit through a lead;

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

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

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

Furthermore, the protection unit further comprises a self-locking circuit to prevent the output of the first comparator from turning over twice, the input end of the self-locking circuit is connected with the output end of the first comparator, the output end of the self-locking circuit is connected with the first input end of the first comparator, and the self-locking circuit is a one-way conduction circuit.

Furthermore, the protection unit further comprises a starting circuit for unlocking the self-locking circuit, the input end of the starting circuit is connected with the output end of the first comparator, and the output end of the starting circuit is connected with the signal output port of the control unit.

Furthermore, the self-locking circuit comprises a first diode, wherein the cathode of the first diode is connected with the first input end of the first comparator, and the anode of the first diode is connected with the output end of the first comparator.

Further, the starting circuit comprises a second diode, an anode of the second diode is connected with the output end of the first comparator, and a cathode of the second diode is connected with a 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 second comparator includes a first input terminal and a second input terminal; the second input end of the second comparator is connected with the output end of the first comparator, the first input end of the second comparator is divided into two paths, one path is grounded through the seventh resistor, and the other path is connected with the second direct-current power supply through the sixth resistor; the output end of the second comparator is divided into two paths, one path is connected with a power supply through the eighth resistor, and the other path is connected with one end of the ninth resistor; the other end of the ninth resistor is connected with the input end of the control unit and the input end of the driving unit respectively.

Furthermore, the protection unit further comprises a first capacitor, a second capacitor, a third capacitor, a fourth capacitor and a fifth capacitor, wherein one end of the first capacitor, one end of the second capacitor, one end of the third capacitor, one end of the fourth capacitor and one end of the fifth capacitor are all grounded, the other end of the first capacitor is connected with the second output end of the first comparator, the other end of the second capacitor is connected with the first input end of the first comparator, the other end of the third capacitor is connected with the output end of the first comparator, the other end of the fourth capacitor is connected with the first input end of the second comparator, and the other end of the fifth capacitor is connected with the ninth resistor.

Furthermore, the current sampling circuit comprises a sampling resistor, one end of the sampling resistor is respectively connected with the negative electrode of the direct current side of the rectifier bridge and the third resistor, and the other end of the sampling resistor is connected with the emitter of the switching tube and is grounded.

Compared with the prior art, IGBT overcurrent protection circuit have following advantage:

IGBT overcurrent protection circuit in, the output of protection unit divide into two the tunnel, all the way with the control unit's input links to each other, another way through a wire with drive unit's input links to each other, when power factor correction circuit overflows, IGBT overcurrent protection circuit can produce hardware protection at first, and hardware protection response time is short than software protection response time, thereby the realization is right the switch tube is more timely, more effectively protected for the switch tube does not damage because of power factor correction circuit overflows, has realized the overcurrent protection of switch tube, has improved the stability of circuit, and the reliability is higher.

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

an air conditioner comprises the IGBT overcurrent protection circuit.

Compared with the prior art, the air conditioner and the IGBT overcurrent protection circuit have the same advantages, and the detailed description is omitted.

Drawings

The accompanying drawings, which form a part hereof, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention without undue limitation. In the drawings:

fig. 1 is a schematic diagram of an IGBT overcurrent protection circuit according to an embodiment of the present invention;

fig. 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.

Description of reference numerals:

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-driving unit, 401-driving chip, 50-control unit, IGBT-switching tube, AC-alternating current power supply, BG 1-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 direct current power supply, VD-second direct current power supply, R1-first resistor, r2-second resistor, R3-third resistor, R4-fourth resistor, R5-fifth resistor, R6-sixth resistor, R7-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, IC 1A-first comparator, IC 1B-second comparator, CLR-signal output port and ZD 1-voltage stabilizing diode.

Detailed Description

It should be noted that, in the present invention, the embodiments and features of the embodiments may be combined with each other without conflict.

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

Example 1

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

Referring to fig. 2, the current sampling unit 20 is respectively connected to an emitter of the switching transistor IGBT, a negative electrode of a dc side of a rectifier bridge BG1 in the power factor correction circuit 10, and an input end of the protection unit 30, and the current sampling unit 20 samples an output current of the power factor correction circuit 10 to obtain a sampling current, and transmits the sampling current to the input end of the protection unit 30.

The protection unit 30 is configured to convert the sampling current into a sampling voltage, compare the sampling voltage with a reference voltage, and output a detection signal; the output terminal of the protection unit 30 is divided into two paths, one path of PWM _ EN is connected to the input terminal of the control unit 50, and the other path of IPM _ FO is connected to the input terminal of the driving unit 40 through a wire.

The output end PFC _ PWM of the control unit 50 is connected to 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.

An output end IGBT _ Driver of the driving unit 40 is connected to a gate of the switching tube IGBT, and the driving unit 40 is configured to control 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 pfc circuit 10 is abnormal or the detection signal is abnormal due to the surge and over-voltage of the power grid, the driving unit 40, after receiving the detection signal directly transmitted by the protection unit 30 through the wire, may timely cut off the driving signal output to the gate of the switch tube igbt to turn off the switch tube igbt, thereby implementing the hardware protection of the switch tube igbt; after receiving the detection signal transmitted by the protection unit 30, the control unit 50 performs signal processing on the detection signal, and outputs 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 switch tube igbt, thereby realizing software protection of the switch tube igbt.

In this way, because the output end of the protection unit 30 is directly connected with the input end of the driving unit 40 through a wire, when the power factor correction circuit 10 is overcurrent, the IGBT overcurrent protection circuit firstly generates hardware protection, and the hardware protection response time is shorter than the software protection response time, so that the switching tube IGBT is protected more timely and effectively, the switching tube IGBT is not damaged due to overcurrent of the power factor correction circuit 10, the stability of the circuit is improved, and the reliability is higher.

Example 2

As described above, the difference between the IGBT overcurrent protection circuit of this embodiment and the embodiment is that, as shown in fig. 2, the power factor correction circuit 10 of this embodiment includes an AC power supply AC, a rectifier bridge BG1, an inductor L, a switching tube IGBT, a fourth diode D4, an electrolytic capacitor E1, and an electrolytic capacitor E2. A first alternating current input end of the rectifier bridge BG1 is connected to a zero line end ACN of an alternating current power supply AC, and a second alternating current input end of the rectifier bridge BG1 is connected to a phase line end ACL of the alternating current power supply AC. The positive electrode of the direct-current side of the rectifier bridge BG1 is connected to one end of an inductor L, 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 a 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 shown in fig. 2, the protection unit 30 of the present embodiment includes a first comparison circuit 301, and the first comparison circuit 301 includes a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a first comparator IC1A, and a first dc power 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 dc power VCC through the second resistor R2. The second input end of the first comparator IC1A is divided into two paths, one path is connected to the negative electrode of the dc side of the rectifier bridge BG1 and the current sampling unit 20 through the third resistor R3, and the other path is connected to the first dc power source VCC through the first resistor R1. An output terminal of the first comparator IC1A is connected to an input terminal of the control unit 50, an input terminal of the driving unit 40, and one terminal of the fifth resistor R5, respectively. The other end of the fifth resistor R5 is connected to a 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 milliampere, so that the voltage drop is negligible. 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 R61 is connected with the emitter of the switching tube IGBT and is grounded. Preferably, the first input of the first comparator IC1A is its non-inverting input and the second input is its inverting input. The first resistor R1, the second resistor R2, the third resistor R3 and the fourth resistor R4 are voltage dividing resistors, and the resistor R5 is a pull-up resistor at the output terminal of the first comparator IC 1A. In this embodiment, the reference voltage Ub of the equidirectional input terminal of the first comparator IC1A is (R4/R4+ R2) × VCC, the reference voltage Ua of the inverting input terminal of the first comparator IC1A is (R3/R3+ R1) × VCC, the output terminal voltage of the first comparator IC1A is Uf, Uf is the detection signal voltage value, and the reference voltage is set to Ua greater than Ub.

When the power factor correction circuit 10 is in normal operation, Ua is greater than Ub, the voltage Uf at the output terminal of the first comparator IC1A is at low level, and the input terminals of the driving unit 40 and the control unit 50 are both at low level and active. The low-level detection signal output by the first comparator IC1A is directly transmitted to the input terminal of the driving unit 40 through a wire, meanwhile, the first comparator IC1A outputs the low-level detection signal to the control unit 50, the control unit 50 processes the detection signal, and after determining that the current is not overcurrent, the control unit 50 outputs the control signal to the input terminal of the driving unit 40. In this way, the output end of the driving unit 40 outputs a driving signal to the gate of the switching tube IGBT to charge the parasitic capacitance of the gate of the switching tube IGBT, the switching tube IGBT is turned on, and the power factor correction circuit 10 allows operation. At this time, the current flowing through the sampling resistor R61 is Iac, the sampling resistor R61 divides the voltage, the voltage Ua decreases, and if Ua is still greater than Ub, the IGBT overcurrent protection circuit does not enter 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 surge and the voltage are too strong to cause Ua to be smaller than Ub, the first comparator IC1A is turned over, the output voltage Uf of the first comparator IC1A is at a high level, so that the protection unit 30 directly outputs a high-level detection signal to the input end of the driving unit 40 through a lead, the driving unit 40 stops outputting the driving signal, the switching tube IGBT stops working, and hardware protection of the switching tube IGBT is completed; meanwhile, 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 the current is judged to be overcurrent, software turns off the output of the control unit 50, thereby completing software protection of the switching tube IGBT. When Ua is equal to Ub, the overcurrent protection threshold point is reached, and from this threshold point, the overcurrent current Iac is equal to [ VCC- (VCC-Ub)/R1 (R3+ R1) ]/R61.

Example 4

As mentioned above, the difference between the present embodiment and the IGBT overcurrent protection circuit is that, as shown in fig. 2, the protection unit 30 further includes 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 conducting circuit.

When the control signal of the power factor correction circuit 10 is abnormal or the power grid surge and the voltage are too strong to cause Ua to be smaller than Ub, the first comparator IC1A is turned over, Uf output by the first comparator IC1A is at a high level, and the switching 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, and it is ensured that the first comparator IC1A is not turned over twice due to increase of Ua.

Thus, due to the effect of the self-locking circuit 302, when the switching tube IGBT in this embodiment stops working due to overcurrent of current, the first comparator IC1A will not turn over twice due to Ua increase, and even if the control unit 50 makes a judgment mistake and does not stop outputting a control signal to the input end of the driving unit 40, the switching tube IGBT will not turn on automatically, so that the IGBT overcurrent protection circuit in this embodiment has a self-locking function, thereby avoiding an out-of-control state where the switching tube IGBT is turned off and the output of the control unit 50 is not turned off, and ensuring that the circuit does not oscillate after the switching tube IGBT is turned off.

Example 5

As mentioned above, the difference between the present embodiment and the IGBT overcurrent protection circuit is that, as shown in fig. 2, the protection unit 30 further includes a start circuit 303 to unlock the self-locking circuit 302 from the circuit, an input end of the start circuit 303 is connected to an output end of the first comparator IC1A, and an output end of the start circuit 303 is connected to the signal output port CLR of the control unit 50.

After the switching tube IGBT is protected, if the switching tube IGBT is to be turned on again, the signal output port CLR of the control unit 50 can output a low level signal, Uf discharges through the start circuit 303, the level of Uf is pulled low, it can be ensured that the Ub voltage is restored to the initial reference point, then the signal output port CLR is turned to a high level again, the switching tube IGBT can be turned on, and the power factor correction circuit 10 can work again.

Therefore, after the overcurrent protection of the switching tube IGBT in the embodiment, if the switching tube IGBT is to be turned on again, the locking function is directly released through software, and the protection time can be freely adjusted through the software, so that the protection time of the IGBT overcurrent protection circuit in the embodiment can be freely adjusted.

Example 6

As described above, the difference between the IGBT overcurrent protection circuit of this embodiment and the embodiment is that, as shown in fig. 2, the self-locking circuit 302 includes the first diode D1, the cathode of the first diode D1 is connected to the first input terminal of the first comparator IC1A, and the anode is connected to the output terminal of the first comparator IC 1A.

In this embodiment, after the IGBT stops working, the voltage Uf is directly applied to Ub through the first diode D1, so that the Ub voltage is raised, and it is ensured that the first comparator IC1A does not flip twice due to increase of Ua.

Thus, due to the unidirectional conduction of the first diode D1, the voltage Uf can only be applied to Ub via the first diode D1, which ensures the stability of the circuit. And the resistance is very little when first diode D1 switches on, and the voltage drop when voltage Uf passes through first diode D1 is less, and the voltage of acting on Ub is bigger, and the Ub voltage is higher by the lifting, and self-locking circuit 302's self-locking function is stronger.

Example 7

As described above, the difference between the IGBT overcurrent protection circuit of this embodiment and the IGBT overcurrent protection circuit of fig. 2 is that the start circuit 303 includes the second diode D2, the anode of the second diode D2 is connected to the output terminal of the first comparator IC1A, and the cathode is connected to the signal output port CLR of the control unit 50.

In this embodiment, after the IGBT is protected, if the IGBT is to be turned on again, the CLR port of the signal output port of the control unit 50 outputs a low level signal, Uf directly discharges through the second diode D2, because the resistance is small when the second diode D2 is turned on, the blocking effect on the current is small, the discharging speed of Uf is faster, the level is pulled down faster, it can be ensured that the Ub voltage is quickly restored to the initial reference point, and the speed at which the start circuit 303 releases the locking of the self-locking circuit 302 to the circuit is faster.

Example 8

As described above, the present embodiment differs from the IGBT overcurrent protection circuit described above in that, with reference to fig. 2, the protection unit 30 further includes a second comparison circuit 304, and the second comparison circuit 304 includes a second comparator IC1B, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, and a second dc power VDD. The second comparator IC1B includes a first input end and a second input end, the second input end of the second comparator IC1B is connected with the output end of the first comparator IC1A, the first input end of the second comparator IC1B is divided into two paths, one path is grounded through a seventh resistor R7, and the other path is connected with a second dc power supply VDD through a sixth resistor R6; the output end of the second comparator IC1B is divided into two paths, one path is connected with a power supply through an eighth resistor R8, and the other path is connected with one end of a ninth resistor R9; the other end of the ninth resistor R9 is connected to the input terminal of the control unit 50 and the input terminal of the driving unit 40, respectively.

The sixth resistor R6 and the seventh resistor R7 are voltage dividing resistors, the eighth resistor R8 is a pull-up resistor at the output terminal of the second comparator IC1B, and the ninth resistor R9 is a current limiting resistor at the output terminal of the second comparator IC 1B.

In many cases, when the pfc circuit 10 is operating normally, the output of the first comparator IC1A is at a low level, and when the circuit is over-current, the output of the first comparator IC1A is at a high level. When the control unit 50 and the driving unit 40 both have active high input and output high input, the high detection signal output by the first comparator IC1A will make the control unit 50 and the driving unit 40 output high output, and the IGBT cannot be turned off. In this embodiment, when the current of the power factor correction circuit 10 is overcurrent, the second comparator circuit 304 may 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 driving unit 40 output low levels, thereby achieving the purpose of turning off the IGBT.

In this embodiment, the first input terminal of the second comparator IC1B is preferably the non-inverting input terminal thereof, and the second input terminal thereof is preferably the inverting input terminal thereof. The voltage at the inverting input of the comparator IC1B is Uf, and the reference voltage Ud at the inverting input of the comparator IC1B is (R7/R7+ R6) × VDD. The reference voltage is set to Ua greater than Ub, and Uf is greater than Ud when Uf is high. When the power factor correction circuit 10 works normally, Ua is larger than Ub, the output voltage Uf of the comparator IC1A is at a low level, Uf is smaller than Ud, and the output end of the comparator IC1B outputs a high-level detection signal; when the circuit is over-current, the output voltage Uf of the comparator IC1A is high level; if Uf is larger than Ud, the comparator IC1B inverts, and the comparator IC1B outputs a low-level detection signal.

In this way, due to the function of the second comparison circuit 304, the user has a wider selectable range and a higher degree of freedom when selecting the control unit 50 and the driving unit 40 cooperating with the protection circuit 30 in the present embodiment.

Example 9

As shown in fig. 2, the present embodiment of the IGBT overcurrent protection circuit is different from the IGBT overcurrent protection circuit described above in that the protection unit 30 further includes a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, and a fifth capacitor C5, 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 end of the first comparator IC1A, the other end of the second capacitor C2 is connected to the first input end of the first comparator IC1A, the other end of the third capacitor C3 is connected to the output end of the first comparator IC1A, the other end of the fourth capacitor C4 is connected to the first input end of the second comparator IC1B, and the other end of the fifth capacitor C5 is connected to the ninth resistor 539r 9.

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, and appropriate capacitance values are selected by calculation, so that interference of noise signals to circuits can be filtered, detection signals are closer to true values, and false triggering caused by the noise signals is avoided. The reliability of the circuit is higher.

Example 10

As mentioned above, the difference between the IGBT overcurrent protection circuit of the present embodiment and the IGBT overcurrent protection circuit 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 end of the driving chip 401 is divided into three paths, one path is connected with the output end PFC _ PWM of the control unit 50 through a tenth resistor R10, the other path is grounded through an eleventh resistor R11, and the other path is connected with the output end of the protection unit 30; the output end of the driving chip 401 is connected with the gate of the switching tube IGBT.

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

The pins INA and INB are both connected to the output end PFC _ PWM of the control unit 50 through the tenth resistor R10, both grounded through the eleventh resistor R11, and both connected to the output end of the protection unit 30. The sixth capacitor C6 is connected in parallel with the eleventh resistor R11, and one end of the seventh capacitor C7 is grounded, and the other end is connected to the Vcc pin of IR4427 and the dc power supply. Pins OA and OB are both connected with the grid electrode 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 input of the pins INA and INB are both high level, so that the pins OA and OB both output high level to charge the parasitic capacitance of the gate of the switching tube IGBT, and the switching tube IGBT is switched on; when the power factor correction circuit 10 is in overcurrent, the input of the pins INA and INB are both low level, so that the pins OA and OB both output low level, the charges stored in the parasitic capacitance of the gate of the switching tube IGBT are discharged, and the switching tube IGBT is turned off.

Example 11

As described above, the present embodiment is different from the IGBT overcurrent protection circuit described above in 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 thirteenth resistor R13, which is connected in parallel with the fourteenth resistor R14, is connected to the pins OA and OB of the driving chip 401 through the twelfth resistor R12, and the other end is connected to the gate of the switching tube IGBT.

In this embodiment, the thirteenth resistor R13 and the fourteenth resistor R14 are both 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 end of the chip IR4427, the output pin of the chip IR4427 outputs a high level to charge the gate parasitic capacitor of the switching tube IGBT, and the twelfth resistor R12 can adjust the charging speed of the gate parasitic capacitor of the switching tube IGBT, so as to prevent the switching tube IGBT from being burnt due to too fast charging.

Example 12

As shown in fig. 3, the driving unit 40 further includes a third diode D3, a cathode of the third diode D3 is connected to pins OA and OB of the driving chip 401, and an anode of the third diode D3 is connected to a 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 driving unit 40 outputs a low level, and since the voltage drop of the third diode D3 is smaller than the voltage drop generated by the same driving turn-off current on the twelfth resistor R12, the charge stored in the gate capacitor of the switching tube IGBT is rapidly discharged through the third diode D3.

Thus, due to the effect of the third diode D3, the switching tube IGBT can be turned off quickly when the circuit is over-current in the embodiment, the protection speed is faster, and the loss of the circuit is reduced.

Example 13

As shown in fig. 3, the difference between the present embodiment and the above-mentioned IGBT overcurrent protection circuit is that the driving unit 40 further includes a zener diode ZD1 and a fifteenth resistor R15, an anode of the zener diode ZD1 is grounded, a cathode of the zener diode ZD1 is connected to the gate of the switching tube IGBT, and the common terminal of the thirteenth resistor R13 and the fourteenth resistor R14, and the fifteenth resistor R15 is connected between the gate of the switching tube IGBT and the ground.

In the switching tube IGBT, the insulation resistance between the grid electrode and the drain electrode and between the grid electrode and the source electrode of the MOS tube is high, the insulation layer is thin, the grid electrode is easy to accumulate charges to break down the insulation layer to damage the MOS tube, and if high voltage is applied to the grid electrode in the using process, the insulation layer is broken down to damage the MOS tube. In the embodiment, the grid of the switching tube IGBT is connected with the voltage stabilizing diode ZD1 in parallel, so that the grid voltage can be limited to be below the voltage stabilizing value of the voltage stabilizing diode ZD1, and the grid of the switching tube IGBT is prevented from being broken down. The fifteenth resistor R15 is used as a pull-down resistor to release electrostatic charges on the gate, so that the charges are not accumulated, and the gate of the switching tube IGBT is prevented from being broken down by the static electricity.

Example 14

The embodiment provides an air conditioner, which comprises the IGBT overcurrent protection circuit in any one of the embodiments. Therefore, due to the effect of the IGBT overcurrent protection circuit, the air conditioner in the embodiment has better protection effect and higher protection speed on the IGBT of the switching tube.

The above description is only a preferred embodiment of the present invention, and should not be taken as limiting the invention, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

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 2-6, 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. The IGBT overcurrent protection circuit of claim 7, 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.

11. The IGBT overcurrent protection circuit of claim 8, wherein the current sampling circuit comprises a sampling resistor (R61), one end of the sampling resistor (R61) is connected with the negative electrode of the rectifier bridge (BG1) on the direct current side 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.

12. An air conditioner characterized by comprising the IGBT overcurrent protection circuit according to any one of claims 1 to 11.