CN201178498Y

CN201178498Y - Surge protection circuit for electromagentic furnace

Info

Publication number: CN201178498Y
Application number: CNU2008200932453U
Authority: CN
Inventors: 伍炎军; 冯世荣; 刘建伟
Original assignee: Shenzhen H&T Intelligent Control Co Ltd
Current assignee: Shenzhen H&T Intelligent Control Co Ltd
Priority date: 2008-04-03
Filing date: 2008-04-03
Publication date: 2009-01-07
Anticipated expiration: 2018-04-03

Abstract

The utility model relates to a surge protection circuit of an electromagnetic furnace, which comprises a rectifier and filter circuit (1), and a detection circuit (2), a resonant circuit (7) and an IGBT (5) connected with the rectifier and filter circuit (1), wherein the surge protection circuit further includes a switch circuit (6) connected between the detection circuit (2) and the IGBT (5) for controlling to switch off the IGBT (5) after a surge disturbance signal is generated; and the switch circuit (6) includes a current limiting resistor R43 and a transistor Q3. In order to solve the disadvantages in the prior art that the IGBT can be easily damaged due to the longer response time for switching off the IGBT and lower protection speed, the switch circuit (6) is added between the output terminal of the detection circuit (2) for generating a surge detection signal and the gate of the IGBT (5), so that the gate of the IGBT (5) is directly controlled by the surge detection signal, thereby improving the protection speed of the hardware circuit and increasing the operation reliability of the electromagnetic furnace.

Description

The electromagnetic oven surge protection circuit

Technical field

The utility model relates to surge protection circuit, more particularly, relates to a kind of highly reliable quick electromagnetic stove surge protection circuit.

Background technology

Surge (electrical surge) also be surging, as the term suggests be exactly the transient overvoltage that exceeds normal working voltage.Say that in essence surge is to occur in the microsecond level to interior a kind of high-voltage pulse of Millisecond time, may cause that the reason of surge has jumbo, short circuit, power supply to switch or big-block engine.In Electronic Design, surge mainly refers to the strong pulse that power supply moment sudden change produces, because the non-linear of circuit itself might have the pulse that is higher than power supply itself, perhaps, other parts in power supply or the circuit are called surge owing to being subjected to or external spike interference own.Surge probably makes circuit burn out in a flash, blows as the puncture of PN junction electric capacity, resistance etc.And surge protection utilizes the protective circuit of non-linear element to the sensitivity design of high frequency (surge) exactly.

As depicted in figs. 1 and 2, show the system block diagram and the schematic diagram of the electromagnetic oven surge protection circuit on the prior art respectively.The output control of surge protection generally is an output port of control oscillation circuit; when the input of electromagnetic oven power supply produces the surge interference in current rectifying and wave filtering circuit 1; this interference signal produces disturbing signal on constantan wire resistance R 31; behind the resistance R 57 of this disturbing signal by testing circuit 2, R52, the R39; cause the potential change of comparator U1A the 5th pin, in low-level output signal of output (i.e. the 2nd pin) generation of comparator U1A.This signal is sent into single-chip microcomputer and is produced interruption, and promptly single-chip microcomputer stops to export control signal, by diode D2 the 11st pin current potential of the comparator U1D of oscillating circuit 3 is dragged down simultaneously, and then makes the 13rd pin output low level of comparator U1D.Produce low level by drive circuit 4 backs at IGBT 5 grids IGBT 5 is ended, thereby protected IGBT 5.What output OUT1 was connected with OUT2 among the figure is heater coil, when alternating current behind current rectifying and wave filtering circuit 1, form high relatively direct voltage, in the drain electrode through being added to IGBT 5 behind the heater coil.When the grid of IGBT 5 is high level, IGBT 5 conductings, because the internal resistance during IGBT 5 conductings is very little, electric energy just is converted into magnetic energy and is stored in the heater coil like this.When the grid of IGBT 5 was low level, IGBT 5 ended, because the electric current in the heater coil can not suddenly change, can only just, be converted into electric field energy to magnetic field energy by capacitor C 14 discharges to capacitor C 14 chargings, to the heater coil discharge, so go round and begin again just forms resonance to capacitor C 14 again subsequently.The high frequency magnetic field that heater coil produces has produced powerful eddy current at the irony pan, and the bottom of a pan generates heat rapidly, and the electromagnetic energy in the heater coil is converted into heat energy.

But the shortcoming of this circuit is that the surge detection signal will pass through oscillating circuit 3 and drive circuit 4, and the reaction time that IGBT5 ends is longer, so protection speed is fast inadequately, causes IGBT 5 to damage sometimes.

The utility model content

The technical problems to be solved in the utility model is, and is longer at the reaction time that the above-mentioned IGBT of prior art ends, and the defective of the fast inadequately and fragile IGBT of protection speed provides a kind of reliable quick electromagnetic stove surge protection circuit.

The technical scheme that its technical problem that solves the utility model adopts is: construct a kind of electromagnetic oven surge protection circuit; the testing circuit, resonant circuit, the IGBT that comprise current rectifying and wave filtering circuit and be connected to rectification circuit, it also comprises being connected and is used for after the surge disturbing signal switching circuit that control IGBT ends between testing circuit and the IGBT.

In electromagnetic oven surge protection circuit described in the utility model; described switching circuit comprises current-limiting resistance R43 and triode Q3; resistance R 43 is connected between the base stage of the output of testing circuit and triode Q3, and the collector electrode of triode Q3 is connected to the grid of IGBT, grounded emitter.

In electromagnetic oven surge protection circuit described in the utility model, described current rectifying and wave filtering circuit comprises rectifier bridge heap, filter inductance and the filter capacitor that is connected between AC power and the IGBT.

In electromagnetic oven surge protection circuit described in the utility model; described testing circuit comprises constantan wire resistance R 31, comparator U1A and resistance R 39, R52, R57; resistance R 31 is connected between rectifier bridge heap and the ground; the 4th pin of comparator U1A is connected between R31 and the rectifier bridge heap by resistance R 39, R52, R57, and produces output signal by the 2nd pin.

Implement electromagnetic oven surge protection circuit of the present utility model; has following beneficial effect: between the grid of the output of the testing circuit that produces the surge detection signal and IGBT, increase a switching circuit; directly control the grid of IGBT by the surge detection signal; accelerate the protection speed of hardware circuit, strengthened the reliability of electromagnetic oven work.

Description of drawings

The utility model is described in further detail below in conjunction with drawings and Examples, in the accompanying drawing:

Fig. 1 is the module map of the electromagnetic oven surge protection circuit of prior art;

Fig. 2 is the schematic diagram of the electromagnetic oven surge protection circuit of prior art;

Fig. 3 is the module map of an embodiment of the utility model electromagnetic oven surge protection circuit;

Fig. 4 is the schematic diagram of an embodiment of the utility model electromagnetic oven surge protection circuit.

Embodiment

As shown in Figure 3; shown electromagnetic oven surge protection circuit comprises current rectifying and wave filtering circuit 1, testing circuit 2, oscillating circuit 3, drive circuit 4, IGBT 5, switching circuit 6 and resonant circuit 7; current rectifying and wave filtering circuit 1 is connected respectively to testing circuit 2 and resonant circuit 7; resonant circuit 7 is connected to IGBT 5; switching circuit 6 is connected between testing circuit 2 and the IGBT 5; oscillating circuit 3 is connected to drive circuit 4, and drive circuit 4 is connected to IGBT 5.Produce disturbing signal from the surge interference signal of electromagnetic oven power supply input by current rectifying and wave filtering circuit 1; this disturbing signal is passed to testing circuit 2; produce a detection signal by testing circuit 2; this detection signal is by after the switching circuit 2; further IGBT 5 is controlled; detection signal just need not pass through oscillating circuit 3 and drive circuit 4 like this, directly IGBT 5 is controlled, thereby has accelerated protection speed.

As shown in Figure 4, there is shown the schematic diagram of an embodiment of the utility model electromagnetic oven surge protection circuit.Switching circuit 6 shown in the figure comprises current-limiting resistance R43 and triode Q3, and resistance R 43 is connected between the base stage of the output of testing circuit 2 and triode Q3, and the collector electrode of triode Q3 is connected to the grid of IGBT 5, grounded emitter.Current rectifying and wave filtering circuit 1 comprises rectifier bridge heap, filter inductance and the filter capacitor that is connected between AC power and the resonant circuit 7.Testing circuit 2 comprises constantan wire resistance R 31, comparator U1A and resistance R 39, R52, R57, resistance R 31 is connected between rectifier bridge heap and the ground, the 4th pin of comparator U1A is connected between R31 and the rectifier bridge heap by resistance R 39, R52, R57, and produces output signal by the 2nd pin.Wherein the output of testing circuit 2 is also connected to single-chip microcomputer, is used for producing interrupting.

When the input of electromagnetic oven power supply produced the surge interference, this interference signal produced disturbing signal (constantan wire is used for detecting electric current) on constantan wire resistance R 31.This disturbing signal causes the potential change of comparator U1A the 4th pin of testing circuit 2 by resistance R 57, R52, R39, produces a high level output signal at the output (i.e. the 2nd pin) of comparator U1A.This detection signal is sent into single-chip microcomputer and is produced interruption, and promptly single-chip microcomputer stops to export control signal, and the current-limiting resistance R43 by switching circuit 6 makes triode Q3 conducting simultaneously.If this moment, IGBT 5 grids were high level, because triode Q3 conducting, IGBT 5 grids will be dragged down is low level, thereby effectively protects IGBT 5 not to be damaged.If this moment, the grid of IGBT 5 was a low level, then the conducting of triode Q3 can't influence the state of IGBT 5 grids, and IGBT 5 still is a cut-off state.IGBT 5 can conducting under the above-mentioned two states, thereby can protect IGBT 5 not to be damaged fast and effectively.

The related switching circuit of the utility model comprises and is not limited to the structure shown in the figure, structure shown in the figure is an embodiment of the present utility model, triode Q3 shown in the figure can use the device of same effect to replace on an equal basis, as transistor, relay etc.

The utility model is longer at the reaction time that prior art IGBT 5 ends; the defective of the fast inadequately and fragile IGBT 5 of protection speed; between the grid of the output of the testing circuit 3 that produces the surge detection signal and IGBT5, increase a switching circuit 6; directly control the grid of IGBT 5 by the surge detection signal; accelerate the protection speed of hardware circuit, strengthened the reliability of electromagnetic oven work.

The utility model is described by some embodiment, and those skilled in the art know, under the situation that does not break away from spirit and scope of the present utility model, can carry out various changes or equivalence replacement to these features and embodiment.In addition, under instruction of the present utility model, can make amendment to these features and embodiment can not break away from spirit and scope of the present utility model to adapt to concrete situation and material.Therefore, the utility model is not subjected to the restriction of specific embodiment disclosed herein, and all interior embodiment of claim scope that fall into the application belong to protection range of the present utility model.

Claims

1, a kind of electromagnetic oven surge protection circuit; the testing circuit (2), resonant circuit (7), the IGBT (5) that comprise current rectifying and wave filtering circuit (1) and be connected to current rectifying and wave filtering circuit (1); it is characterized in that, also comprise being connected being used between testing circuit (2) and the IGBT (5) after producing the surge disturbing signal, controlling the switching circuit (6) that IGBT (5) ends.

2, electromagnetic oven surge protection circuit according to claim 1; it is characterized in that; described switching circuit (6) comprises current-limiting resistance R43 and triode Q3; resistance R 43 is connected between the base stage of the output of testing circuit (2) and triode Q3; the collector electrode of triode Q3 is connected to the grid of IGBT (5), grounded emitter.

3, electromagnetic oven surge protection circuit according to claim 1 is characterized in that, described rectification circuit (1) comprises rectifier bridge heap, filter inductance and the filter capacitor that is connected between AC power and the IGBT (5).

4, electromagnetic oven surge protection circuit according to claim 3; it is characterized in that; described testing circuit (2) comprises constantan wire resistance R 31, comparator U1A and resistance R 39, R52, R57; resistance R 31 is connected between rectifier bridge heap and the ground; the 4th pin of comparator U1A is connected between R31 and the rectifier bridge heap by resistance R 39, R52, R57, and produces output signal by the 2nd pin.