CN203166499U

CN203166499U - IGBT overvoltage protection circuit of electromagnetic oven

Info

Publication number: CN203166499U
Application number: CN 201320138118
Authority: CN
Inventors: 柳翼
Original assignee: Changsha University of Science and Technology
Current assignee: Changsha University of Science and Technology
Priority date: 2013-03-25
Filing date: 2013-03-25
Publication date: 2013-08-28
Anticipated expiration: 2023-03-25

Abstract

The utility model discloses an IGBT overvoltage protection circuit of an electromagnetic oven. The IGBT overvoltage protection circuit comprises a rectifier bridge circuit, an induction coil coupled at an output end of the rectifier bridge circuit and a resonant capacitor connected in parallel with the induction coil, wherein a common end of the induction coil and the resonant capacitor is connected with a collector electrode of an IGBT, a resistor R1 and a resistor R2 are connected in series between the collector electrode of the IGBT and a ground, a resistor R3 and a resistor R4 are connected in series between an external power source and the ground, two input ends of a comparator are respectively connected with a common end of the resistor R1 and the resistor R2 and a common end of the resistor R3 and the resistor R4, and an output end of the comparator is coupled with a grid electrode of the IGBT. The IGBT overvoltage protection circuit can effectively provide overvoltage protection for the power transistor IGBT of the electromagnetic oven, further reduces precision requirements on a detection protection circuit of fault current and further reduces difficulties in hardware design and debugging. The IGBT overvoltage protection circuit has a simple structure and greatly improves work reliability of the electromagnetic oven.

Description

The IGBT overvoltage crowbar of electromagnetic oven

Technical field

The utility model relates to a kind of protective circuit, especially relates to a kind of overvoltage crowbar for electromagnetic oven power transistor IGBT.

Background technology

IGBT(insulated gate bipolar transistor in the prior art electromagnetic oven) protection, generally by surge protection circuit is set, the sudden change of protective circuit monitoring line voltage, catch voltage fluctuation and voltage surge signal, when reality is used, for the bigger signal of voltage fluctuation, surge protection circuit detects easily at present, but the signal less to voltage fluctuation can be omitted, and damages phenomenon and produce IGBT; For this reason; the electromagnetic oven circuit technology has been done further improvement; can detect the less signal of voltage fluctuation; but this kind improvement; when the small voltage fluctuation that causes under special electrical network condition and during other electricity piece plug-ins work, surge protection circuit will produce action, protection system work; thereby intermittently heating phenomena occurs, cause system frequently to protect.In addition; in the existing current surge protective circuit; when tending to occur surge on the electrical network and occurring; IGBT is conducting; the shortcoming that has signal lag, this protection that slightly lags behind has suitable risk, causes the damage of IGBT easily; and still false triggering may appear in that particular electrical is off the net, influence the safe handling of electromagnetic oven.

CN201120200617.X proposes a kind of electromagnetic oven of IGBT overvoltage protection; comprise the main resonance loop; the rectification circuit and the microprocessor that are electrically connected with the main resonance loop; the main resonance loop is provided with IGBT and IGBT control circuit; microprocessor is connected with the IGBT control circuit; described rectification circuit one end is connected with the dual overvoltage crowbar of IGBT; the dual overvoltage crowbar of IGBT comprises first comparison circuit that the IGBT ON time is adjusted and second comparison circuit that IGBT is turn-offed, and first comparison circuit of the dual overvoltage crowbar of IGBT and the output of second comparison circuit are connected to microprocessor and control the IGBT control circuit by microprocessor.But this IGBT overvoltage crowbar element is more, circuit structure is complicated and realize that cost is higher.

The utility model content

Be to solve prior art problems, the utility model proposes a kind of circuit simple, realize lower-cost IGBT overvoltage crowbar, effective protection is provided in the time of can be to the power transistor IGBT overvoltage of electromagnetic oven.

The utility model adopts following technical scheme to realize:, a kind of IGBT overvoltage crowbar of electromagnetic oven, comprise rectifier circuit, be coupled in the induction coil of rectifier circuit output, the resonant capacitance in parallel with induction coil; Induction coil is connected the collector electrode of IGBT with the common port of resonant capacitance, series resistor R1 and resistance R 2 between the collector electrode of this IGBT and the ground; Series resistor R3 and resistance R 4 between external power source and the ground; The comparator that two inputs are connected with the common port of common port, resistance R 3 and the resistance R 4 of resistance R 1 and resistance R 2 respectively, the output of this comparator couples the grid of IGBT.

Wherein, the IGBT overvoltage crowbar of described electromagnetic oven also comprises: at an output serial connection choke induction of rectifier circuit.

Wherein, the IGBT overvoltage crowbar of described electromagnetic oven also comprises: connect filter capacitor between two outputs of rectifier circuit.

Compared with prior art, the utlity model has following beneficial effect:

The utility model is when detecting IGBT both end voltage generation overvoltage fault-signal; controlling timely conducting IGBT drags down its both end voltage again; avoid it to damage because of over-voltage breakdown, effectively the power transistor IGBT for electromagnetic oven provides overvoltage protection.And, having reduced the difficulty that the accuracy of the detection protective circuit of fault current requires and reduced hardware designs and debugging, circuit structure simply and has greatly improved the functional reliability of electromagnetic oven.

Description of drawings

Fig. 1 is the circuit diagram of an embodiment of the utility model.

Embodiment

In conjunction with shown in Figure 1, the IGBT(insulated gate bipolar transistor that the utility model proposes) overvoltage crowbar comprises: be connected the rectifier circuit of AC power, the wherein output serial connection of this rectifier circuit is used for controlling the choke induction L1 of mutation current; And between two outputs of described rectifier circuit, connecting filter capacitor C1, it is arranged in pairs or groups with described choke induction L1, and the output voltage of described rectifier circuit is carried out filtering; The induction coil L2 of serial connection choke induction L1, the resonant capacitance C2 in parallel with induction coil L2, induction coil L2 is connected the collector electrode (C) of IGBT Q1 with the common port of resonant capacitance C2, the collector electrode of this IGBT Q1 passes through resistance R 1 connection comparator U1's, and the output of comparator U1 couples the grid (G) of IGBT Q1; And two inputs of comparator U1 are respectively by resistance R 2 and resistance R 3 ground connection, and connection external power source VCC behind the resistance R 3 series resistor R4.

After the dividing potential drop of the CE interstage voltage of IGBT Q1 through resistance R 1 and resistance R 2, be input to one of them input of comparator U1; And after the dividing potential drop of external power source VCC through resistance R 3 and resistance R 4, be sent to another input of comparator U1 as reference voltage.

Voltage between the CE of IGBT Q1 level is normal, and when namely comparator U1 negative input end voltage was higher than the voltage of positive input terminal, the output output low level of comparator U1 was sent to the grid of IGBT Q1; Too high between the CE of IGBT Q1 level, when namely the voltage of the positive input terminal of comparator U1 was higher than the voltage of negative input end, the output of comparator U1 output high level was sent to the grid of IGBT Q1.

In foregoing circuit, when IGBT Q1 was conducting state, the electric current that flows through induction coil L2 continued to rise; When IGBT Q1 is off state, the resonant capacitance C2 charging of induction coil L2, at this moment, the voltage between the CE level of IGBT Q1 rises.When the electric current that produces as induction coil L2 is excessive, or when inhaling the magnetic difference with the pan that microwave oven (electromagnetic oven) collocation is used, all may cause the overtension between the CE level of IGBT Q1; At this moment, the high level of the output of comparator U1 output is sent to the grid of IGBT Q1, makes IGBT Q1 conducting; And after IGBT Q1 conducting, induction coil L2 stops resonant capacitance C2 is charged, and the electric current of its generation flows through IGBT Q1, voltage between the CE level of IGBT Q1 is descended, eliminate failure voltage signal, and after the output output low level by comparator U1, IGBT Q1 being turn-offed, the immediate current of avoiding IGBT Q1 conducting under high pressure that its collector electrode is flow through is excessive and cause overcurrent to be burnt.

The above only is preferred embodiment of the present utility model; not in order to limit the utility model; all any modifications of within spirit of the present utility model and principle, doing, be equal to and replace and improvement etc., all should be included within the protection range of the present utility model.

Claims

1. the IGBT overvoltage crowbar of an electromagnetic oven comprises rectifier circuit, is coupled in the induction coil of rectifier circuit output, the resonant capacitance in parallel with induction coil; It is characterized in that, also comprise:

Induction coil is connected the collector electrode of IGBT with the common port of resonant capacitance, series resistor R1 and resistance R 2 between the collector electrode of this IGBT and the ground;

Series resistor R3 and resistance R 4 between external power source and the ground;

The comparator that two inputs are connected with the common port of common port, resistance R 3 and the resistance R 4 of resistance R 1 and resistance R 2 respectively, the output of this comparator couples the grid of IGBT.

2. according to the IGBT overvoltage crowbar of the described electromagnetic oven of claim 1, it is characterized in that, also comprise: at an output serial connection choke induction of rectifier circuit.

3. according to the IGBT overvoltage crowbar of claim 1 or 2 described electromagnetic ovens, it is characterized in that, also comprise: between two outputs of rectifier circuit, connect filter capacitor.