IGBT desaturation detection circuit with strong anti-interference capability

Abstract

The utility model discloses an IGBT desaturation detection circuit with strong anti-interference capability, which belongs to the technical field of detection circuits, and comprises an IGBT driving chip U, an external desaturation detection circuit, an IGBT and a driving resistor Rg, the IGBT driving chip U is connected with the external desaturation detection circuit, the IGBT driving chip U is connected with the IGBT through the driving resistor Rg, and the IGBT is connected with the external desaturation detection circuit; the external desaturation detection circuit comprises a capacitor C2, a triode T1, a resistor R3, a comparator 01, a voltage-regulator tube Z1, a capacitor C1, a resistor R1, a resistor R2, a diode D1 and a diode D2. Through the above mode, the scheme does not directly employ a driving chip desaturation detection circuit to carry out IGBT collector-emitter voltage Vce detection, detection is carried out by adding an additional circuit, the Vce desaturation judgment voltage can be set to be a high value through the additional circuit, compared with direct driving chip detection, a higher noise admissible value is achieved, and the detection precision is improved. And the anti-interference capability is higher.

Description

Technical Field

[0001] The utility model relates to the technical field of detection circuits, and particularly relates to an IGBT desaturation detection circuit with strong anti-interference ability. Background Art

[0002] IGBT desaturation refers to a state in which, when the current passing through the IGBT is extremely large, it exits the saturation conduction state and enters the amplification region. At this time, the current is extremely large, the collector-emitter voltage of the IGBT is the bus high voltage, and the IGBT loss is also extremely large. If desaturation detection and protection are not carried out, the IGBT will fail due to overheating.

[0003] Existing IGBT desaturation detection circuits usually directly use the desaturation detection pin desat of the IGBT drive chip, in cooperation with a charging capacitor and an isolation diode, to detect the collector-emitter voltage Vce of the IGBT when it is conducting. When Vce exceeds a certain value, it is considered that the IGBT has desaturated.

[0004] However, the existing technology has the following problems. When the voltage of the desaturation detection pin desat of the drive chip exceeds the internal threshold voltage of the drive chip, it is considered that desaturation has occurred. However, the internal threshold voltage of the drive chip is generally relatively low, usually 7V. Under normal operating conditions, this voltage is generally not exceeded. However, since the desaturation detection circuit is connected to the IGBT collector, when the IGBT switches, the collector voltage changes extremely fast, and parasitic parameters cause very large noise at the desat pin. Since the desaturation detection circuit needs to respond within an extremely short time, simply increasing the filter capacitor is not feasible because it will delay the response time and fail to achieve the purpose of protection. Therefore, due to the low threshold voltage of the existing technical solution and the inability to simply and roughly use capacitor filtering, it is extremely easy to cause false triggering of desaturation detection; on the other hand, the Vce of different IGBTs varies greatly when conducting. When applied to high-current or high-voltage IGBTs, the Vce is even higher, and desaturation detection is more likely to be falsely triggered.

[0005] Based on this, the utility model designs an IGBT desaturation detection circuit with strong anti-interference ability to solve the above problems. Summary of the Utility Model

[0006] In view of the above-mentioned drawbacks of the existing technology, the utility model provides an IGBT desaturation detection circuit with strong anti-interference ability.

[0007] To achieve the above objectives, the utility model is realized through the following technical solutions:

[0008] An IGBT desaturation detection circuit with strong anti-interference ability, including an IGBT driver chip U, an external desaturation detection circuit, an IGBT, and a driving resistor Rg. The IGBT driver chip U is connected to the external desaturation detection circuit. The IGBT driver chip U is connected to the IGBT through the driving resistor Rg. The IGBT is connected to the external desaturation detection circuit;

[0009] The external desaturation detection circuit includes a capacitor C2, a triode T1, a resistor R3, a comparator 01, a zener diode Z1, a capacitor C1, a resistor R1, a resistor R2, a diode D1, and a diode D2.

[0010] Furthermore, one end of the capacitor C2 and the collector of the triode T1 are both connected to the IGBT driver chip U. One end of the diode D2 is electrically connected to the collector of the IGBT. One end of the resistor R1 is connected to the IGBT driver chip U.

[0011] Furthermore, the IGBT driver chip U includes a comparator 02, a constant current source I, a triode T2, a desaturation detection signal pin desat, a power supply pin Vcc, a ground pin GND, and an output pin Vg. The desaturation detection signal pin desat is electrically connected to one end of the capacitor C2 and the collector of the triode T1. The base of the triode T1 is electrically connected to one end of the resistor R3. The other end of the resistor R3 is electrically connected to the first end of the comparator 01. The second end of the comparator 01 is electrically connected to one end of the resistor R1, one end of the capacitor C1, and one end of the diode D1. The other end of the diode D1 is electrically connected to one end of the diode D2. The other end of the diode D2 is electrically connected to the collector of the IGBT. The emitter of the IGBT is electrically connected to the ground pin GND. One end of the base of the IGBT is electrically connected to one end of the driving resistor Rg. The other end of the driving resistor Rg is electrically connected to the output pin Vg.

[0012] Furthermore, the other end of the capacitor C2 and the emitter of the triode T1 are both electrically connected to the ground pin GND.

[0013] Furthermore, the other end of the resistor R1 is electrically connected to the output pin Vg.

[0014] Furthermore, the third end of the comparator 01 is electrically connected to one end of the resistor R2 and one end of the zener diode Z1.

[0015] Furthermore, the other end of the resistor R2 is electrically connected to the power supply pin Vcc.

[0016] Furthermore, the other end of the zener diode Z1 and the other end of the capacitor C1 are both electrically connected to the ground pin GND.

[0017] Compared with the prior art, the beneficial effects of the present utility model are as follows: 1. Instead of directly using the desaturation detection circuit of the driving chip to detect the collector-emitter voltage Vce of the IGBT, an additional circuit is added for detection;

[0018] 2. The additional circuit can set the Vce desaturation judgment voltage to a relatively high value, which has a higher noise tolerance and stronger anti-interference ability compared with directly using the driving chip for detection;

[0019] 3. When applied to different IGBT specifications, the threshold value can be adjusted up or down according to the test situation by adjusting the parameters of the zener diode, effectively ensuring the adaptability of the desaturation detection circuit under different application conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present utility model or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present utility model, and those of ordinary skill in the art can also obtain other drawings based on these drawings without creative efforts.

[0021] Figure 1 It is a block diagram of an IGBT desaturation detection circuit with strong anti-interference ability according to the present utility model;

[0022] Figure 2 It is a circuit connection diagram of an IGBT desaturation detection circuit with strong anti-interference ability according to the present utility model. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] In order to make the objectives, technical solutions, and advantages of the embodiments of the present utility model clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present utility model with reference to the drawings in the embodiments of the present utility model. Obviously, the described embodiments are some, but not all, of the embodiments of the present utility model. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments of the present utility model belong to the scope of protection of the present utility model.

[0024] Embodiment 1: In some embodiments, please refer to Figure 1 - Figure 2 of the accompanying drawings of the specification. An IGBT desaturation detection circuit with strong anti-interference ability includes an IGBT driving chip U, an external desaturation detection circuit, an IGBT, and a driving resistor Rg. The IGBT driving chip U is connected to the external desaturation detection circuit. The IGBT driving chip U is connected to the IGBT through the driving resistor Rg, and the IGBT is connected to the external desaturation detection circuit;

[0025] The external desaturation detection circuit includes a capacitor C2, a triode T1, a resistor R3, a comparator 01, a zener diode Z1, a capacitor C1, a resistor R1, a resistor R2, a diode D1, and a diode D2.

[0026] One end of the capacitor C2 and the collector of the triode T1 are both connected to the IGBT driver chip U. One end of the diode D2 is electrically connected to the collector of the IGBT. One end of the resistor R1 is connected to the IGBT driver chip U.

[0027] The IGBT driver chip U adopts conventional and mature technologies in the art, such as Figure 2 As shown, the IGBT driver chip U includes a comparator 02, a constant current source I, a triode T2, a desaturation detection signal pin desat, a power supply pin Vcc, a ground pin GND, and an output pin Vg. The internal connection method of the IGBT driver chip U is as follows: The second end of the comparator 02 is electrically connected to one end of the constant current source I, the collector of the triode T2, and one end of the desaturation detection signal pin desat. The emitter of the triode T2 is electrically connected to the ground pin GND. The third end of the comparator 02 is connected to a 7V power supply.

[0028] The desaturation detection signal pin desat is electrically connected to one end of the capacitor C2 and the collector of the triode T1. The base of the triode T1 is electrically connected to one end of the resistor R3. The other end of the resistor R3 is electrically connected to the first end of the comparator 01. The second end of the comparator 01 is electrically connected to one end of the resistor R1, one end of the capacitor C1, and one end of the diode D1. The other end of the diode D1 is electrically connected to one end of the diode D2. The other end of the diode D2 is electrically connected to the collector of the IGBT. The emitter of the IGBT is electrically connected to the ground pin GND. One end of the base of the IGBT is electrically connected to one end of the driving resistor Rg. The other end of the driving resistor Rg is electrically connected to the output pin Vg.

[0029] The other end of the capacitor C2 and the emitter of the triode T1 are both electrically connected to the ground pin GND.

[0030] The other end of the resistor R1 is electrically connected to the output pin Vg.

[0031] The third end of the comparator 01 is electrically connected to one end of the resistor R2 and one end of the zener diode Z1.

[0032] The other end of the resistor R2 is electrically connected to the power supply pin Vcc.

[0033] The other end of the zener diode Z1 and the other end of the capacitor C1 are both electrically connected to the ground pin GND.

[0034] When the drive chip does not receive a drive instruction, the output pin Vg of the drive chip outputs a low level of 0V, the gate of the IGBT is also at a low level, the IGBT is not conducting, the cathode voltage of the diode D2 is the bus high voltage, and the anode is at a low voltage, so both diodes D2 and D1 are cut off. The output pin Vg outputs 0V, so the inverting input terminal Vn of the comparator O1 is 0V. The voltage of the non-inverting input terminal Vp of the comparator O1 is the zener voltage of 10V, so the output of the comparator 01 is high, and the triode T1 conducts, pulling the desaturation detection signal pin desat low through the triode T1. When the drive chip does not receive a drive instruction, the internal logic of the drive chip causes the triode T2 to conduct, and the desaturation detection signal pin desat is also pulled low by the internal triode T2. Therefore, when the drive chip does not receive a drive instruction, the desaturation detection signal pin desat will be pulled low by both the triode T1 and the triode T2, and the internal constant current source I flows into the ground through the triode T1 and the triode T2;

[0035] The input voltage of the desaturation detection signal pin desat is 0V, the inverting input of the internal comparator O2 of the drive chip is 7V, and the output Vo1 of O2 is low, not triggering the desaturation fault judgment circuit of the drive chip, so the drive chip does not consider that the IGBT has undergone desaturation.

[0036] When the drive chip receives a drive instruction, the output pin Vg of the drive chip outputs a high level of 15V equal to the power supply voltage Vcc, and the IGBT conducts. If the IGBT conducts normally and there is no desaturation, the collector-emitter voltage Vce of the IGBT is the saturation conduction voltage drop Vce_sat. And Vce_sat is a relatively low value, usually less than 3V. The output voltage of the output pin Vg of the drive chip is relatively high compared to Vce_desat, so the diodes D1 and D2 conduct forward. At this time, the output voltage of the output pin Vg of the drive chip charges the capacitor C1 through the resistor R1;

[0037] Let the conduction voltage of the diode be V D1、 V D2 . When the IGBT conducts stably, V n voltage is clamped at a relatively low value V n =V D1 +V D2 +Vce_sat by the diodes D1, D2 and Vce_sat. Vce_sat is usually less than 3V, and V D1 and V D2 are usually less than 1V, so Vn is usually less than 5V, then V n of the comparator O1 is less than V P zener voltage of 10V, so the comparator O1 outputs a high level and the triode T1 conducts;

[0038] When the drive chip receives a drive instruction, the internal logic of the drive chip turns off the triode T2. However, since T1 is in the conducting state, the constant current source I inside the drive chip flows to the ground through the triode T1, and the voltage of the desaturation detection signal pin desat is still pulled to the reference ground 0V. Therefore, the comparator 02 inside the drive chip still outputs low, does not trigger the desaturation fault, and the drive chip determines that the IGBT has not undergone desaturation.

[0039] When the IGBT is conducting and desaturation occurs, the collector-emitter voltage Vce of the IGBT increases sharply from the saturation conduction voltage Vce_sat to the bus high voltage. The diodes D1 and D2 are cut off. Because the output voltage of the output pin Vg is high level, it will continuously charge the capacitor C1 through the resistor R1. Since there is no device to clamp the voltage at this point, the voltage on the capacitor C1 will continuously increase. When it exceeds the non-inverting input terminal V of the comparator O1 P When this happens, the comparator flips and outputs low, and the triode T1 is cut off. Because the triode T2 is also cut off when there is a drive instruction, the constant current source I inside the drive chip charges the capacitor C2. When the capacitor is charged to the internal threshold voltage of 7V, the output of the comparator O2 inside the drive chip flips and becomes high, triggering the desaturation protection of the drive chip. The drive chip determines that desaturation has occurred, blocks the output, and Vg becomes low level. Thus, the detection and protection of desaturation are completed.

[0040] Embodiment 2: In some embodiments, as Figure 2 shown, as a preferred embodiment of the present invention, in the existing solution, only the comparator inside the drive chip is used for detection. Then, the preset IGBT conduction voltage drop is:

[0041] Vce1 = 7 - V D1 -V D2 = 5V

[0042] If the detection is carried out through the present utility model, the preset IGBT desaturation detection threshold is:

[0043] Vce2 = 10 - V D1 -V D2 = 8V

[0044] Because when the IGBT is desaturated, Vce is close to the bus high voltage, there is no such statement that setting the threshold voltage too high will cause the IGBT not to be protected during desaturation.

[0045] Obviously, Vce2 is greater than Vce1, and the threshold is higher, which means that if there is noise in the detection circuit, the existing desaturation detection circuit is more likely to be falsely triggered, and the present invention has a higher noise tolerance. At the same time, in the existing solution, 7V is fixed inside the chip and cannot be changed, while in the present invention, because 10V is completely set by the voltage regulator Z1, different voltage regulators can be used to achieve different desaturation detection thresholds, which can be high or low, and have good adaptability.

[0046] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An IGBT desaturation detection circuit with strong anti-interference ability, characterized in that It includes an IGBT drive chip (U), an external desaturation detection circuit, an IGBT, and a drive resistor (Rg). The IGBT drive chip U is connected to the external desaturation detection circuit. The IGBT drive chip U is connected to the IGBT through the drive resistor (Rg). The IGBT is connected to the external desaturation detection circuit; The external desaturation detection circuit includes a capacitor (C2), a triode (T1), a resistor (R3), a comparator (01), a zener diode (Z1), a capacitor (C1), a resistor (R1), a resistor (R2), a diode (D1), and a diode (D2).

2. The IGBT desaturation detection circuit with strong anti-interference ability according to claim 1, wherein One end of the capacitor (C2) and the collector of the triode (T1) are both connected to the IGBT drive chip (U). One end of the diode (D2) is electrically connected to the collector of the IGBT. One end of the resistor (R1) is connected to the IGBT drive chip (U).

3. The IGBT desaturation detection circuit with strong anti-interference ability according to claim 2, characterized in that, The IGBT drive chip U includes a comparator (02), a constant current source (I), a triode (T2), a desaturation detection signal pin (desat), a power supply pin (Vcc), a ground pin (GND), and an output pin (Vg). The desaturation detection signal pin (desat) is electrically connected to one end of the capacitor (C2) and the collector of the triode (T1). The base of the triode (T1) is electrically connected to one end of the resistor (R3). The other end of the resistor (R3) is electrically connected to the first end of the comparator (01). The second end of the comparator (01) is electrically connected to one end of the resistor (R1), one end of the capacitor (C1), and one end of the diode (D1). The other end of the diode (D1) is electrically connected to one end of the diode (D2). The other end of the diode (D2) is electrically connected to the collector of the IGBT. The emitter of the IGBT is electrically connected to the ground pin (GND). One end of the base of the IGBT is electrically connected to one end of the drive resistor (Rg). The other end of the drive resistor (Rg) is electrically connected to the output pin (Vg).

4. The IGBT desaturation detection circuit with strong anti-interference ability according to claim 3, characterized in that, The other end of the capacitor (C2) and the emitter of the triode (T1) are both electrically connected to the ground pin (GND).

5. The IGBT desaturation detection circuit with strong anti-interference ability according to claim 4, characterized in that The other end of the resistor (R1) is electrically connected to the output pin (Vg).

6. The IGBT desaturation detection circuit with strong anti-interference ability according to claim 5, characterized in that, The third end of the comparator (01) is electrically connected to one end of the resistor (R2) and one end of the zener diode (Z1).

7. The IGBT desaturation detection circuit with strong anti-interference ability according to claim 6, characterized in that, The other end of the resistor (R2) is electrically connected to the power supply pin (Vcc).

8. The IGBT desaturation detection circuit with strong anti-interference ability according to claim 7, characterized in that, The other end of the zener diode (Z1) and the other end of the capacitor (C1) are both electrically connected to the ground pin (GND).

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