CN204886903U

CN204886903U - IGBT current foldback circuit

Info

Publication number: CN204886903U
Application number: CN201520650979.7U
Authority: CN
Inventors: 唐鹤然
Original assignee: Guangzhou Yi He Medical Skill Development Corp Ltd
Current assignee: Guangzhou Yi He Medical Skill Development Corp Ltd
Priority date: 2015-08-27
Filing date: 2015-08-27
Publication date: 2015-12-16
Anticipated expiration: 2025-08-27

Abstract

The utility model discloses a IGBT current foldback circuit, including electric current acquisition circuit, adopt current sensor for IGBT's C, the electric current at E both ends are flow past in the collection, and change voltage signal output into, signal conditioning circuit handles voltage signal to the output current signal, the peak value circuit keeps the current signal, comparison circuit adopts the comparator for relatively current signal and protection threshold, and the output pulse signal closes IGBT to IGBT, have avoided that its on state current is too big to reduce the risk that IGBT overflowed to the IGBT damage, have lengthened device life, have improved the reliability of using the system of this IGBT device, utilize peak value holding circuit to realize turn -offing time -delayed protection, in case the trigger protection, can make IGBT switch on control in hold time can become invalid.

Description

A kind of IGBT current foldback circuit

Technical field

The utility model relates to field of electronic devices, specifically a kind of IGBT current foldback circuit and the shutoff overvoltage protection that caused by overcurrent protection.

Background technology

Insulated gate bipolar transistor IGBT has that input impedance is high, switching speed is fast, driving power is little, saturation pressure reduces, control circuit is simple and bear the features such as electric current is large, thus, has and use widely in power electronic equipment.

When short circuit and overcurrent, if do not protected rapidly, just easily there is super overheating limit, phenomenon such as generation latching effect, device over-voltage breakdown etc. cause component failure in IGBT.When such as turning off IGBT, the rate of descent of its collector current is higher, especially in case of short-circuit faults, if do not taked soft switching measure, its critical current rate of descent will reach every microsecond kilo-ampere, can cause damage like this, even cause component failure to IGBT.

Utility model content

For solving the deficiency that background technology proposes, the utility model provides a kind of IGBT current foldback circuit.

For achieving the above object, the technical scheme that the utility model adopts is: a kind of IGBT current foldback circuit, comprise the current collection circuit, signal conditioning circuit, overcurrent time detection circuit, comparison circuit and the peak holding circuit that are electrically connected successively, wherein current collection circuit, adopt current sensor, for gathering the electric current at C, E two ends flowing through IGBT, and change into voltage signal output; Signal conditioning circuit, processes voltage signal, and output current signal; Peak current, keeps current signal; Comparison circuit, adopts comparator, and for comparing current signal and protection thresholding, and output pulse signal closes IGBT.

Preferably, described signal conditioning circuit comprises voltage follower circuit, it comprises comparator U2A and resistance R1, and the voltage signal of the positive input termination current collection circuit output of described comparator U2A, the negative input end of comparator U2A connects the output of comparator U2A through resistance R1.

Preferably, described signal conditioning circuit comprises RC filter circuit, and it comprises the resistance R3 and electric capacity C1 that are in series, and resistance R3 one end is connected with the output of comparator U2A, and the other end is through electric capacity C1 ground connection.

Preferably, described signal conditioning circuit comprises amplifying circuit, it comprises comparator U2B and resistance R2/R4/R5, the positive input terminal of comparator U2B is through resistance R5 ground connection, the node of negative input end between resistance R4 connecting resistance R3 and electric capacity C1 of comparator U2B, between the negative input end that resistance R2 is connected in parallel on comparator U2B and output.

Preferably, described comparison circuit comprises comparator U3B, resistance R6/R8, the wherein output of resistance R6 mono-termination Peak current, the negative input end of another termination comparator U3B, resistance R8 one end ground connection, the positive input terminal of another termination comparator U3B, the gate leve of the output termination IGBT of comparator U3B.

Preferably, described protection thresholding comprises resistance R7 and ﹢ 15V power supply, described resistance R7 mono-termination ﹢ 15V power supply, the positive input terminal of another termination comparator U3B.

Preferably, also comprise shutoff overvoltage crowbar, be arranged between the C pole of IGBT and E pole, for absorbing the high pressure that IGBT turn off process produces.

Preferably; described shutoff overvoltage crowbar comprises fly-wheel diode, absorption resistance, piezo-resistance, noninductive electric capacity and indicator light; be connected in parallel between the C pole of IGBT and E pole after described piezo-resistance and indicator light series connection; described fly-wheel diode and absorption resistance are connected in parallel on piezo-resistance two ends respectively, and described noninductive Capacitance parallel connection is at indicator light two ends.

The utility model adopts after said structure, for IGBT, avoids that its On current is excessive reduces the risk of IGBT overcurrent to IGBT damage, extends device useful life, improves the reliability of the system using this IGBT device; Utilize peak holding circuit to realize turn off delay time protection, once trigger protection, IGBT conducting control can be made within the retention time to lose efficacy.

Accompanying drawing explanation

Fig. 1 is logic diagram of the present utility model.

Fig. 2 is shutoff overvoltage crowbar schematic diagram of the present utility model.

Fig. 3 is circuit theory diagrams of the present utility model.

Embodiment

Below in conjunction with the drawings and specific embodiments, the utility model is described in further detail:

As shown in Figure 1, a kind of IGBT current foldback circuit, comprise the current collection circuit, signal conditioning circuit, overcurrent time detection circuit, comparison circuit and the peak holding circuit that are electrically connected successively, wherein current collection circuit, adopt current sensor, for gathering the electric current at C, E two ends flowing through IGBT, and change into voltage signal output; Signal conditioning circuit, carries out servo-actuated, filtering, amplification process to voltage signal, and output current signal; Peak current, keeps current signal; Comparison circuit, adopt comparator, for comparing current signal and protection thresholding, and output pulse signal closes IGBT, for IGBT, avoid its On current excessive to IGBT damage, reduce the risk of IGBT overcurrent, extend device useful life, improve the reliability of the system using this IGBT device; Utilize peak holding circuit to realize turn off delay time protection, once trigger protection, IGBT conducting control can be made within the retention time to lose efficacy.

Current collection circuit adopts high precision electric current transducer LA200, measures with this electric current that IGBT flows through, and with this electric current as the foundation whether starting overcurrent protection.

As shown in Figure 3, described signal conditioning circuit comprises voltage follower circuit, it comprises comparator U2A and resistance R1, the voltage signal of the positive input termination current collection circuit output of described comparator U2A, the negative input end of comparator U2A connects the output of comparator U2A through resistance R1, adopt voltage follower circuit, can realize input impedance high, and output impedance is low, plays buffering, isolation, improve load capacity.

Described signal conditioning circuit comprises RC filter circuit; it comprises the resistance R3 and electric capacity C1 that are in series; resistance R3 one end is connected with the output of comparator U2A; the other end, through electric capacity C1 ground connection, by RC filter circuit filtering high frequency spikes, prevents from triggering; simultaneously; set the retention time by RC filter circuit, i.e. the overcurrent protection time, structure is simple, with low cost.

Described signal conditioning circuit comprises amplifying circuit, it comprises comparator U2B and resistance R2/R4/R5, the positive input terminal of comparator U2B is through resistance R5 ground connection, the node of negative input end between resistance R4 connecting resistance R3 and electric capacity C1 of comparator U2B, between the negative input end that resistance R2 is connected in parallel on comparator U2B and output.

Described peak value protective circuit comprises comparator U3A, diode D1 and electric capacity C2; positive input terminal one tunnel of comparator U3A connects the output of comparator U2B through diode D1; another road is through electric capacity C2 ground connection; the output of the negative input termination comparator U3A of comparator U3A; peak holding circuit is used for keeping circuit to remain on certain value; keep certain hour; the negative input end being mainly comparator U3B provides a stable voltage; or stable electric current, with complete comparison circuit and protection thresholding continue compare.

Described comparison circuit comprises comparator U3B, resistance R6/R8, wherein the output of resistance R6 mono-termination Peak current, the negative input end of another termination comparator U3B, resistance R8 one end ground connection, the positive input terminal of another termination comparator U3B, the gate leve of the output termination IGBT of comparator U3B.

Described protection thresholding comprises resistance R7 and ﹢ 15V power supply, described resistance R7 mono-termination ﹢ 15V power supply, the positive input terminal of another termination comparator U3B.

As shown in Figure 2, also comprise shutoff overvoltage crowbar, be arranged between the C pole of IGBT and E pole, for absorbing the high pressure that IGBT turn off process produces, described shutoff overvoltage crowbar comprises fly-wheel diode, absorption resistance, piezo-resistance, noninductive electric capacity and indicator light, be connected in parallel between the C pole of IGBT and E pole after described piezo-resistance and indicator light series connection, described fly-wheel diode and absorption resistance are connected in parallel on piezo-resistance two ends respectively, described noninductive Capacitance parallel connection is at indicator light two ends, the high pressure produced when IGBT turns off can by fly-wheel diode consumption on absorption resistance, resistance and the power of absorption resistance are determined by load characteristic, when voltage between the C pole and E pole of IGBT exceedes rated voltage, piezo-resistance resistance can reduce rapidly, overvoltage indicator light will light, provide prompting, use RCD as absorbing circuit, add piezo-resistance and display lamp of connecting shows as overvoltage, conveniently debug use.

A kind of IGBT over-current protection method, its step is

1) a protection thresholding is preset;

2) electric current at C, E two ends of IGBT is gathered, and output voltage signal after carrying out false action-proof process;

3) the voltage signal voltage follower circuit, RC filter circuit and the amplifying circuit that will gather, and draw a retention time by RC filter circuit;

4) allow current signal through peak holding circuit, current signal and protection thresholding are compared, be greater than shutter in limited time at current signal, within the retention time, keep current signal to be added on the gate leve of IGBT, trigger IGBT always and turn off.

Also comprise the step that the high pressure produced C, E two ends of IGBT in turn off process absorbs to protect IGBT.

Comparing of thresholding judge whether to be in over-current state with maintenance by current signal, the Real-Time Monitoring of pure circuit, compared to chip monitoring, circuit is more simple, and cost is saved more, more convenient, energy-conservation.

The above is preferred implementation of the present utility model; certainly the interest field of the utility model can not be limited with this; should be understood that; for those skilled in the art; the technical solution of the utility model is modified or equivalent replacement, do not depart from the protection range of technical solutions of the utility model.

Claims

1. an IGBT current foldback circuit, is characterized in that: comprise the current collection circuit, signal conditioning circuit, comparison circuit and the peak holding circuit that are electrically connected successively, wherein

Current collection circuit, adopts current sensor, for gathering the electric current at C, E two ends flowing through IGBT, and changes into voltage signal output;

Signal conditioning circuit, processes voltage signal, and output current signal;

Peak current, keeps current signal;

Comparison circuit, adopts comparator, and for comparing current signal and protection thresholding, and output pulse signal closes IGBT.

2. a kind of IGBT current foldback circuit according to claim 1; it is characterized in that: described signal conditioning circuit comprises voltage follower circuit; it comprises comparator U2A and resistance R1; the voltage signal of the positive input termination current collection circuit output of described comparator U2A, the negative input end of comparator U2A connects the output of comparator U2A through resistance R1.

3. a kind of IGBT current foldback circuit according to claim 2; it is characterized in that: described signal conditioning circuit comprises RC filter circuit; it comprises the resistance R3 and electric capacity C1 that are in series, and resistance R3 one end is connected with the output of comparator U2A, and the other end is through electric capacity C1 ground connection.

4. a kind of IGBT current foldback circuit according to claim 3; it is characterized in that: described signal conditioning circuit comprises amplifying circuit; it comprises comparator U2B and resistance R2/R4/R5; the positive input terminal of comparator U2B is through resistance R5 ground connection; the node of negative input end between resistance R4 connecting resistance R3 and electric capacity C1 of comparator U2B, between the negative input end that resistance R2 is connected in parallel on comparator U2B and output.

5. a kind of IGBT current foldback circuit according to claim 4; it is characterized in that: described comparison circuit comprises comparator U3B; resistance R6/R8; the wherein output of resistance R6 mono-termination Peak current; the negative input end of another termination comparator U3B; resistance R8 one end ground connection, the positive input terminal of another termination comparator U3B, the gate leve of the output termination IGBT of comparator U3B.

6. a kind of IGBT current foldback circuit according to claim 5, is characterized in that: described protection thresholding comprises resistance R7 and ﹢ 15V power supply, described resistance R7 mono-termination ﹢ 15V power supply, the positive input terminal of another termination comparator U3B.

7. a kind of IGBT current foldback circuit according to claim 1, is characterized in that: also comprise shutoff overvoltage crowbar, is arranged between the C pole of IGBT and E pole, for absorbing the high pressure that IGBT turn off process produces.

8. according to a kind of IGBT current foldback circuit that claim 7 is stated; it is characterized in that: described shutoff overvoltage crowbar comprises fly-wheel diode, absorption resistance, piezo-resistance, noninductive electric capacity and indicator light; be connected in parallel between the C pole of IGBT and E pole after described piezo-resistance and indicator light series connection; described fly-wheel diode and absorption resistance are connected in parallel on piezo-resistance two ends respectively, and described noninductive Capacitance parallel connection is at indicator light two ends.