CN213547476U

CN213547476U - IGBT overvoltage crowbar and air conditioner

Info

Publication number: CN213547476U
Application number: CN202022508924.6U
Authority: CN
Inventors: 俞贤桥; 黄猛; 王京; 陈宁宁; 肖尊辉; 杨博
Original assignee: Gree Electric Appliances Inc of Zhuhai
Current assignee: Gree Electric Appliances Inc of Zhuhai
Priority date: 2020-11-03
Filing date: 2020-11-03
Publication date: 2021-06-25
Anticipated expiration: 2030-11-03

Abstract

The utility model provides a IGBT overvoltage crowbar and air conditioner, IGBT overvoltage crowbar, including the working circuit who is equipped with IGBT, through driving resistance Rg with the drive circuit that working circuit connects still includes: the protection circuit is connected with the working circuit and the driving circuit, and the IGBT is turned on again by the protection circuit when the IGBT is turned off under overvoltage; and one end of the driving resistor Rg is connected with the working circuit, and the other end of the driving resistor Rg is connected with the driving circuit. Compared with the prior art, the utility model discloses IGBT overvoltage crowbar simple structure, low cost can make the TVS pipe work near rated point simultaneously, has improved voltage clamp's precision and circuit validity greatly.

Description

IGBT overvoltage crowbar and air conditioner

Technical Field

The utility model relates to an electrical apparatus field, especially a IGBT overvoltage crowbar and air conditioner.

Technical Field

The IGBT is widely applied to products such as power supplies, household appliances and air conditioners as a common power device, and plays a key role. In practical applications, however, when a current overload or short circuit occurs, voltage overshoot may result due to the high di/dt and the presence of stray inductance in the commutation path, which may exceed the breakdown voltage of the IGBT and damage the IGBT. This would severely limit the range of IGBT applications if the dc bus voltage were high. Therefore, a clamp circuit is usually added to the driving circuit to ensure that the collector potential is not too high.

Referring to fig. 1, a currently common collector-emitter clamp utilizes an external TVS transistor Dz and a diode D1. When the potential at the collector of the IGBT exceeds a certain voltage threshold value Uce, the unidirectional TVS diode Dz conducts and passes current, at which time Q2 turns on and the IGBT turns off. If the Uce voltage is higher than the avalanche voltage of diode Dz, current flows through Dz, D1, Rg, and Q2.

Referring to fig. 2, the operating characteristics of the TVS tube are shown, in a normal condition, the TVS tube can operate near a rated breakdown point (operating point 1), if the current of the TVS tube increases sharply after breakdown, the voltage of the TVS tube increases sharply from the operating point 1 to the operating point 2, which means that the CE voltage of the IGBT also increases, and the clamping effect of the IGBT cannot be achieved. Meanwhile, the power consumption of the TVS tube is very large, so that the TVS tube with larger package must be selected, and the TVS tube has the characteristics of more expensive materials, difficulty in purchase, larger error, overhigh junction capacitance and the like.

Therefore, how to design an IGBT overvoltage protection circuit and an air conditioner can greatly improve the accuracy and effectiveness of IGBT clamping, which is a technical problem to be solved urgently in the industry.

SUMMERY OF THE UTILITY MODEL

To the not good technical problem of IGBT clamp effect among the prior art, the utility model provides an IGBT overvoltage crowbar and air conditioner.

The technical scheme of the utility model for, a IGBT overvoltage protection circuit is proposed, including the working circuit that is equipped with IGBT, through driving resistance Rg with the drive circuit that working circuit connects still includes: the protection circuit is connected with the working circuit and the driving circuit, and the IGBT is turned on again by the protection circuit when the IGBT is turned off under overvoltage;

and one end of the driving resistor Rg is connected with the working circuit, and the other end of the driving resistor Rg is connected with the driving circuit.

Further, the protection circuit includes: the detection unit is used for detecting the current state of the IGBT and the control unit is connected with the working circuit;

the detection unit sends an overvoltage signal to the control unit when detecting that the IGBT is overvoltage, and the control unit controls the IGBT to be turned on again when receiving the overvoltage signal.

Further, the detection unit includes a resistor R1, a resistor R2, a resistor R3, a resistor R4, and an amplifier U1;

the non-inverting input end of the amplifier U1 is connected in series with the resistor R1 and then connected between the resistor Rg and the working circuit, the inverting input end of the amplifier U1 is connected in series with the resistor R3 and then connected between the resistor Rg and the driving circuit, one end of the resistor R2 is connected between the resistor R1 and the non-inverting input end of the amplifier U1, the other end of the resistor R2 is connected with the power supply V-REF, the resistor R4 is connected with the inverting input end and the output end of the amplifier U1, and the output end of the amplifier U1 is also connected to the input of the control unit as the output of the detection unit.

Further, the control unit comprises a resistor R5, a resistor R6, a resistor R7, a resistor R8, a triode Q3 and a comparator U2;

the non-inverting input end of the comparator U2 is connected to the output of the detection unit as the input of the control unit, the inverting input end of the comparator U2 is connected in series to the power supply VCC after the resistor R5, one end of the resistor R6 is connected between the resistor R5 and the inverting input end of the comparator U2, the other end of the resistor R6 is grounded, the output end of the comparator U2 is connected to the base of the triode Q3 after being connected with the resistor R7 in series, the collector of the triode Q3 is connected to the power supply VCC after being connected with the resistor R8 in series, and the emitter of the triode Q3 is connected between the resistor Rg and the working circuit.

Further, the working circuit comprises an IGBT, a TVS tube Dz and a diode D1, wherein a collector of the IGBT is connected with a cathode of the TVS tube Dz, a gate of the IGBT is connected with the resistor Rg, an emitter of the IGBT is grounded, an anode of the TVS tube Dz is connected with an anode of the diode D1, and a cathode of the diode D1 is connected between the resistor Rg and the gate of the IGBT.

Further, the current protection value of the TVS tube Dz Is, and the voltage of the power supply V-REF satisfies the following conditions: V-REF Is more than or equal to Is Rg R2/R1.

Further, the calculation relationship of the resistor R5 and the resistor R6 is as follows: vcc R6/(R5+ R6) = Is Rg R2/R1+ V-REF.

Further, when the current in the resistor Rg Is greater than or equal to Is, the amplifier U1 outputs the overvoltage signal, the comparator U1 receives the overvoltage signal and sends a high-level signal, and the triode Q3 Is turned on to make the IGBT turned on again.

Further, the driving circuit comprises a triode Q1 and a triode Q2, wherein a collector of the triode Q1 is connected with a power supply VCC, an emitter of the triode Q1 is connected with an emitter of the triode Q2, a collector of the triode Q2 is grounded, and a base of the triode Q1 is connected with a base of the triode Q2; the base electrode of the triode Q1 and the base electrode of the triode Q2 are also connected with PWM signal input, one end of the resistor Rg is connected between the emitting electrode of the triode Q1 and the emitting electrode of the triode Q2, and the other end of the resistor Rg is connected with the grid electrode of the IGBT.

The utility model also provides an air conditioner, the air conditioner adopts above-mentioned IGBT overvoltage protection circuit.

Compared with the prior art, the utility model discloses following beneficial effect has at least:

1. the utility model discloses IGBT overvoltage protection circuit simple structure, low cost.

2. The TVS tube can work near the rated point, and the accuracy of voltage clamping and the effectiveness of the circuit are greatly improved.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the embodiments or the prior art descriptions will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive labor.

FIG. 1 is a schematic diagram of a prior art collector-emitter clamp configuration;

FIG. 2 is a schematic diagram of the operation characteristics of a TVS tube;

fig. 3 is a schematic diagram of the circuit structure of the present invention.

Detailed Description

In order to make the technical problem, technical solution and advantageous effects to be solved by the present invention more clearly understood, the following description is given in conjunction with the accompanying drawings and embodiments to illustrate the present invention in further detail. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Thus, a feature indicated in this specification will serve to explain one of the features of an embodiment of the invention, and not to imply that every embodiment of the invention must have the described feature. Further, it should be noted that this specification describes many features. Although some features may be combined to show a possible system design, these features may also be used in other combinations not explicitly described. Thus, the combinations illustrated are not intended to be limiting unless otherwise specified.

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

Referring to fig. 3, the IGBT overvoltage protection circuit includes a working circuit provided with an IGBT, a driving circuit connected to the working circuit through a driving resistor Rg, and a protection circuit connected to the working circuit and the driving circuit, wherein when the IGBT is turned off due to overvoltage, the protection circuit turns on the IGBT again. After the IGBT is turned on again, di/dt in the turn-off process of the IGBT can be reduced, so that voltage overshoot is reduced, and the TVS tube works near a rated working point.

The resistor Rg is a driving resistor of the IGBT, one end of the resistor Rg is connected with the working circuit, the other end of the resistor Rg is connected with the driving circuit, and the resistor Rg is large, so that the current rise rate and the voltage rise rate of the IGBT can be inhibited, but the switching time and the switching loss of the IGBT can be increased; rg is small, so that the current rising rate is increased, and the IGBT is switched on or damaged by mistake. The specific data of Rg is related to the specific structure of the driving circuit and the capacity of the IGBT, generally, the Rg value of the IGBT with small capacity is larger within a few ohms to dozens of ohms.

The protection circuit comprises a detection unit and a control unit, the detection unit is connected with the driving circuit and the control unit, and the control unit is connected with the working circuit. The detection unit is used for detecting the current state of the IGBT, when the IGBT is overvoltage, the detection unit can send an overvoltage signal to the control unit, and the control unit controls the IGBT to be turned on again after receiving the overvoltage signal.

Specifically, the detection unit comprises a resistor R1, a resistor R2, a resistor R3, a resistor R4 and an amplifier U1; the non-inverting input end of the amplifier U1 is connected between the resistor Rg and the working circuit after being connected with the resistor R1 in series, the inverting input end of the amplifier U1 is connected between the resistor Rg and the driving circuit after being connected with the resistor R3 in series, one end of the resistor R2 is connected between the resistor R1 and the non-inverting input end of the amplifier U1, the other end of the resistor R2 is connected with the power supply V-REF, one end of the resistor R4 is connected with the inverting input end of the amplifier U1, the other end of the resistor R4 is connected with the output end of the amplifier U1.

The control unit comprises a resistor R5, a resistor R6, a resistor R7, a resistor R8, a triode Q3 and a comparator U2, wherein the non-inverting input end of the comparator U2 is used as the input of the control unit and connected to the output of the detection unit, the inverting input end of the comparator U2 is connected to the power VCC after being connected to a resistor R5 in series, one end of a resistor R6 is connected between the resistor R5 and the inverting input end of the comparator U2, the other end of the resistor R6 is grounded, the output end of the comparator U2 is connected to the base of the triode Q3 after being connected to a resistor R7, the collector of the triode Q3 is connected to the power VCC after being connected to a resistor R8, and the emitter of.

The working circuit comprises an IGBT, a TVS tube Dz and a diode D1, wherein the collector of the IGBT is connected with the cathode of the TVS tube Dz, the grid of the IGBT is connected with a resistor Rg, the emitter of the IGBT is grounded, the anode of the TVS tube Dz is connected with the anode of a diode D1, and the cathode of a diode D1 is connected between the resistor Rg and the grid of the IGBT.

Wherein, referring to the detection unit part in fig. 3, the detection circuit comprises a differential amplification circuit composed of a resistor R1, a resistor R2, a resistor R3, a resistor R4 and an amplifier U1, the output voltage of the output terminal of the amplifier U1 is Uc = (Ub-Ua) R2/R1+ V _ REF, when the circuit normally works, the driving circuit provides voltage to the working circuit, the current direction flows from a to b, the voltage at the point a is higher than that at the point b, so the result of (Ub-Ua) R2/R1 is negative, and because the resistor Rg is connected in series between the point a and the point b, Ua-Ub = I Rg can be obtained, because the size of the resistor is not changed, the value of Ua-Ub is known to be proportional to the current flowing through the resistor, the current is maximum when the IGBT is overvoltage, and the current protection value of the TVS tube Dz is achieved, the current Is, the detection circuit Is used for detecting whether the IGBT Is in overvoltage, so when the IGBT Is in overvoltage, the value of Ua-Ub Is the largest, namely the value of (Ub-Ua) R2/R1 Is negative and the smallest, at the moment, the output Uc of the amplifier U1 Is required to be ensured to be more than or equal to 0, namely (Ub-Ua) R2/R1+ V _ REF Is more than or equal to 0, and V _ REF Is more than or equal to IS Rg R2/R1, when the current Is the largest, the output end of the amplifier U1 can always have the output level after the condition Is ensured.

Referring to the control unit of fig. 3, the circuit is formed by connecting the output terminals of the resistor R5, the resistor R6, the resistor R7, the comparator U2 and the amplifier U1, when the voltage of the non-inverting input terminal of the comparator U2 is higher than that of the inverting input terminal, the comparator U2 outputs a high level, and when the voltage of the non-inverting input terminal of the comparator U2 is lower than that of the inverting input terminal, the comparator U2 outputs a low level, referring to the transistor Q3 of the control unit of fig. 3, the collector of the transistor Q3 is connected to the power Vcc, the emitter is connected to the gate of the IGBT, and the base is connected to the output terminal of the comparator U2, it can be seen that, when the transistor Q3 is turned on, the power Vcc charges the gate of the IGBT, the IGBT can be turned back on, in order to ensure the transistor Q3 is turned on, the base level of the transistor Q3 is high, and since the base of the transistor Q3 is connected, that is, only when the output level of the output terminal of the comparator U2 is high, the transistor Q3 is turned on, so that the IGBT is turned on again.

Since the non-inverting input of the comparator U2 is connected to the output of the amplifier U1 and the output level of the output of the amplifier U1 is Uc = (Ub-Ua) R2/R1+ V _ REF, in order to make the output of the comparator U2 high, the voltage at the inverting input of the comparator U2 should be lower than that at the non-inverting input thereof, so that when U < Uc, the output of the comparator U2 outputs high. The logic of the circuit Is to enable the circuit to be conducted when the IGBT generates overvoltage, and not to be conducted in other time, so when the IGBT does not generate overvoltage, the voltage of the inverting input end of the comparator U2 needs to be larger than the voltage of the non-inverting input end of the comparator U, at the moment, U > Uc, the voltage of the inverting input end of the comparator U and the voltage of the non-inverting input end of the comparator U need to be divided by whether the IGBT generates overvoltage, when the IGBT generates overvoltage, the current Is, Uc = Is Rg R2/R1+ V-REF, therefore, the voltage of the inverting input end of the comparator U2U = Is Rg R2/R1+ V-REF can be set, when the IGBT generates overvoltage, the current Is increased, the output end of the comparator U2 outputs high level, and when the IGBT does not generate overvoltage, the output end.

Therefore, when the IGBT Is in overvoltage, namely the current I flowing through the resistor Rg Is not less than Is, the amplifier U1 outputs an overvoltage signal, the overvoltage signal Is represented as a signal when the output voltage Uc Is not less than Is Rg R2/R1+ V _ REF, and the comparator U2 outputs a high-level signal after receiving the overvoltage signal output by the amplifier U1, so that the triode Q3 Is conducted, and the IGBT Is conducted again.

The driving circuit is a push-pull circuit and comprises a triode Q1 and a triode Q2, wherein the collector of the triode Q1 is connected with a power supply Vcc, the emitter of the triode Q1 is connected with the emitter of the triode Q2, the collector of the triode Q2 is grounded, the base of the triode Q1 is connected with the base of the triode Q2 and is connected with a PWM signal input, one end of a resistor Rg is connected between the emitter of the triode Q1 and the emitter of the triode Q2, and the other end of the resistor Rg is connected with the grid of an IGBT. When the push-pull circuit works, only one of the two symmetrical triodes is conducted at a time, so that the conduction loss is small. When the driving circuit outputs a high level, the current direction flows from a to b, and when the driving circuit outputs a low level, the current direction flows from b to a, the gate charge released by the IGBT and the working current of the TVS tube flow from point b to point a.

Following the utility model discloses a theory of operation explains, when circuit normal work IGBT does not take place the excessive pressure, sets for the electric current size that flows through resistance Rg this moment and be I₁The output voltage Uc = (Ub-Ua) R2/R1+ V _ REF = V _ REF-I at the output of the amplifier U1 at this time can be derived₁Rg R2/R1, the non-inverting input end of the comparator U2 receives the level signal and then outputs a low level signal, the triode Q3 is cut off, and the IGBT works normally. When the IGBT Is in overvoltage, the output voltage Uc = (Ub-Ua) R2/R1+ V _ REF = V _ REF-Is × Rg R2/R1 of the output end of the amplifier U1 at the moment can be obtained, after the comparator U2 receives the level signal, a high level signal Is output, the triode Q3 Is conducted, and the voltage Vcc Is applied to a capacitor Cgs of the grid electrode of the IGBT (the IGBT)

Internal self-capacitance) to turn on the IGBT again. After the IGBT is turned on, di/dt of the IGBT in the turn-off process can be reduced, so that voltage overshoot is reduced, and the TVS tube works near a rated working point.

Compared with the prior art, the utility model discloses IGBT overvoltage crowbar simple structure, low cost can make TVS pipe work near rated point simultaneously, has improved the validity of voltage clamp's precision and circuit greatly.

The above description is only exemplary of the present invention and should not be taken as limiting the scope of the present invention, as any modifications, equivalents, improvements and the like made within the spirit and principles of the present invention are intended to be included within the scope of the present invention.

Claims

IGBT overvoltage crowbar, including the working circuit that is equipped with IGBT, through driving resistance Rg with the drive circuit that working circuit connects, its characterized in that still includes: the protection circuit is connected with the working circuit and the driving circuit, and the IGBT is turned on again by the protection circuit when the IGBT is turned off under overvoltage;

one end of the driving resistor Rg is connected with the working circuit, and the other end of the driving resistor Rg is connected with the driving circuit;

the protection circuit includes: the detection unit is used for detecting the current state of the IGBT and the control unit is connected with the working circuit;

the detection unit sends an overvoltage signal to the control unit when detecting that the IGBT is overvoltage, and the control unit controls the IGBT to be turned on again when receiving the overvoltage signal;

the detection unit comprises a resistor R1, a resistor R2, a resistor R3, a resistor R4 and an amplifier U1;

the non-inverting input end of the amplifier U1 is connected in series with the resistor R1 and then connected between the resistor Rg and the working circuit, the inverting input end of the amplifier U1 is connected in series with the resistor R3 and then connected between the resistor Rg and the driving circuit, one end of the resistor R2 is connected between the resistor R1 and the non-inverting input end of the amplifier U1, the other end of the resistor R2 is connected with a power supply V-REF, the resistor R4 is connected with the inverting input end and the output end of the amplifier U1, and the output end of the amplifier U1 is also connected to the input of the control unit as the output of the detection unit;

the control unit comprises a resistor R5, a resistor R6, a resistor R7, a resistor R8, a triode Q3 and a comparator U2;

the non-inverting input end of the comparator U2 is connected to the output of the detection unit as the input of the control unit, the inverting input end of the comparator U2 is connected in series to the power supply VCC after the resistor R5, one end of the resistor R6 is connected between the resistor R5 and the inverting input end of the comparator U2, the other end of the resistor R6 is grounded, the output end of the comparator U2 is connected to the base of the triode Q3 after being connected with the resistor R7 in series, the collector of the triode Q3 is connected to the power supply VCC after being connected with the resistor R8 in series, and the emitter of the triode Q3 is connected between the resistor Rg and the working circuit.
2. The IGBT overvoltage protection circuit of claim 1, wherein the working circuit comprises an IGBT, a TVS tube Dz, and a diode D1, wherein a collector of the IGBT is connected to a cathode of the TVS tube Dz, a gate of the IGBT is connected to the resistor Rg, an emitter of the IGBT is grounded, an anode of the TVS tube Dz is connected to an anode of the diode D1, and a cathode of the diode D1 is connected between the resistor Rg and the gate of the IGBT.
3. The IGBT overvoltage protection circuit of claim 2, wherein the current protection value of the TVS tube Dz Is, and the voltage of the power supply V-REF satisfies the following conditions: V-REF Is more than or equal to Is Rg R2/R1.
4. The IGBT overvoltage protection circuit of claim 3, wherein the resistor R5 and the resistor R6 have the computational relationship: vcc R6/(R5+ R6) = Is Rg R2/R1+ V-REF.
5. The IGBT overvoltage protection circuit of claim 4, wherein when a current in the resistor Rg Is greater than or equal to Is, the amplifier U1 outputs the overvoltage signal, the comparator U1 receives the overvoltage signal and sends a high level signal, and the transistor Q3 Is turned on to make the IGBT turned on again.
6. The IGBT overvoltage protection circuit according to claim 1, wherein said driving circuit includes a transistor Q1 and a transistor Q2, a collector of said transistor Q1 is connected to VCC, an emitter of said transistor Q1 is connected to an emitter of said transistor Q2, a collector of said transistor Q2 is grounded, a base of said transistor Q1 is connected to a base of said transistor Q2; the base electrode of the triode Q1 and the base electrode of the triode Q2 are also connected with PWM signal input, one end of the resistor Rg is connected between the emitting electrode of the triode Q1 and the emitting electrode of the triode Q2, and the other end of the resistor Rg is connected with the grid electrode of the IGBT.
7. An air conditioner, characterized in that the air conditioner adopts the IGBT overvoltage protection circuit as claimed in any one of claims 1 to 6.