CN101478142B - Power switch tube protecting circuit in semi-bridge induction heating circuit - Google Patents

Abstract

The invention belongs to the technical field of circuit protection for induction heating circuits, and includes a current resonant circuit, a signal conversion circuit, a rectifier circuit and a combined logic circuit. The output end of the current resonant circuit is connected to the input end of the signal conversion circuit, and the output of the signal conversion circuit The end is connected with the input end of the rectification circuit; it also includes a phase detection pulse generation circuit, the input end of the phase detection pulse generation circuit is connected with the output end of the rectification circuit, and the output end of the phase detection pulse generation circuit is connected with the input end of the combinational logic circuit , the output terminal of the combinational logic circuit is connected with the current resonant circuit. On the basis of the conventional current resonant circuit, the present invention uses a signal conversion circuit and a rectifier circuit to generate a DC voltage signal, and then uses a phase detection pulse generation circuit to generate a phase detection pulse. The phase detection pulse is forced to let The power switch tube in the current resonance circuit is turned off in advance before the current value naturally drops to zero, so as to protect the power switch tube.

Description

A power switch tube protection circuit in a half-bridge induction heating circuit

technical field

The invention belongs to the technical field of circuit protection of an induction heating circuit, and particularly relates to a circuit for protecting a power switch tube of a half-bridge induction heating circuit through current phase detection.

technical background

The half-bridge induction heating circuit is the most commonly used topology in the current field of induction heating technology, and is mainly composed of two power switch tubes and a resonant capacitor. The topology of the technology is simple, the control method is flexible, and the work efficiency is high. However, this technology generally uses circuits with high power and large current, and the most important thing is that the power switch tubes start to work under the conditions of zero current and zero voltage. And if one of the power switch tubes is turned off when the current naturally drops to zero, then the other switch tube is not turned on under zero current and zero voltage conditions, so under high current working conditions, the power switch The tube loss is large, and the temperature rises, which will cause the power switch tube to burn out in severe cases.

In the prior art, the stable operation of the half-bridge induction heating requires many protection circuits to ensure that the existing protection circuits include peak current protection circuits, frequency tracking protection circuits, etc., but there is no current phase detection circuit to ensure power The switch tube is forcibly turned off before the current naturally drops to zero.

Contents of the invention

The purpose of the present invention is to address the deficiencies in the prior art, to design a power switch tube protection circuit in the existing half-bridge induction heating circuit, which can realize that the power switch tube is forcibly turned off before the current naturally drops to zero, thereby It can better protect the power switch tube.

In order to solve the above technical problems, the present invention includes the following technical solutions: a power switch protection circuit in a half-bridge induction heating circuit, including a current resonance circuit, a signal conversion circuit, a rectification circuit and a combinational logic circuit, the current resonance circuit The output end is connected to the input end of the signal conversion circuit, and the output end of the signal conversion circuit is connected to the input end of the rectification circuit; it also includes a phase detection pulse signal that can be generated before the DC voltage signal crosses zero voltage, and acts on the current resonance circuit through a combinational logic circuit The phase detection pulse generating circuit of the power switching tube is forcibly turned off, the input end of the phase detection pulse generating circuit is connected with the output end of the rectifier circuit, the output end of the phase detection pulse generating circuit is connected with the input end of the combinational logic circuit, and the combination The output terminal of the logic circuit is connected to the current resonance circuit.

The phase detection pulse generation circuit includes a phase detection circuit and a synchronous output circuit, and the output terminals of the phase detection circuit and the synchronous output circuit are connected to the input terminal of the combinational logic circuit through a logic relationship of phase and.

Described phase detection circuit comprises comparator T41, resistance R41, resistance R42, resistance R43, resistance R44, electric capacity C41, electric capacity C42; Connected to the output terminal of the rectifier circuit; the other end of the capacitor C41 is connected to the positive terminal of the comparator T41, the resistor R42, the resistor R43, and one end of the capacitor C42, and the resistor R43 is connected in parallel with the capacitor C42 to ground, and the other end of the resistor R42 is connected to the power supply voltage U1;

Described synchronous output circuit comprises comparator T42, resistance R45, resistance R46, electric capacity C44; The positive end of comparator T42 is connected with triangular sawtooth wave signal Uj input end, and the negative end of comparator T42 is connected with resistance R45, resistance R46, electric capacity respectively. One end of C44 is connected; the other end of resistor R46 is connected to power supply voltage U1, resistor R45 is connected in parallel with capacitor C44 and grounded;

After the output terminal of the comparator T42 is connected with the output terminal of the comparator T41, it is connected with the power supply voltage U1 through the resistor R44, and connected with the input terminal of the combinational logic circuit through the diode D41.

The synchronous output circuit also includes a triode Q41. The base of the triode Q41 is connected to the mains zero-crossing voltage signal U3, the emitter is connected to the power ground, and the collector is connected to the output terminal of the comparator T42.

The power switch tube provided in the current resonance circuit is an IGBT tube or a MOSFET tube.

The signal transformation circuit includes a current transformer connected to the current resonant circuit on one side.

The rectification circuit is a bridge rectification circuit.

The combinational logic circuit includes a resistor R51, a resistor R52, a capacitor C53, a capacitor C54, a Zener diode D51 and an integrated chip X1;

Pin 3 of the integrated chip X1 is connected to the cathode of diode D41 and the cathode of Zener diode D51, and the anode of Zener diode D51 is connected to pin 1 and pin 16 of the integrated chip X1 and grounded; pins 2, 13 and 14 of the integrated chip X1 Connect with pin 15 externally; pin 8 of integrated chip X1 is connected to power supply voltage U1;

Capacitors C53 and C54 are connected in parallel to form a filter circuit, one end of which is connected to pin 12 of the integrated chip X1 and connected to the power supply voltage U1, and the other ends of capacitors C53 and C54 are respectively connected to pin 11 of the integrated chip X1 and then grounded; The pins 10 and 10 output IGBT driving signals, and are connected to the input control pins of the current resonance circuit through resistors R51 and R52 respectively.

Compared with the prior art, the invention converts the AC current signal in the half-bridge current resonant circuit into a DC voltage signal after sequentially passing through the signal conversion circuit and the rectification circuit respectively. In the phase detection pulse generating circuit, the reference voltage is set according to the desired phase, and the comparator is used to compare the DC voltage signal with the reference voltage, so that the AC current signal in the half-bridge current resonance circuit is controlled by the comparator before it naturally drops to zero. A phase detection pulse is output, and the phase detection pulse, under the action of the combinational logic circuit, forces the power switch tube in the half-bridge current resonance circuit to be turned off in advance before the current value naturally drops to zero, so as to protect the power switch tube. The realization principle of this circuit is simple and effective, the cost is low, and it is safe and reliable.

Description of drawings

Fig. 1 is a block diagram of the present invention;

Fig. 2 is a schematic circuit diagram of the present invention;

Fig. 3 is the circuit schematic diagram of the embodiment of the present invention;

Fig. 4A is the waveform diagram of the period of the alternating current signal in the half-bridge type current resonant circuit of the present invention being T;

FIG. 4B is a waveform diagram of the present invention in which the AC current signal is converted into a DC voltage signal Up with a period T after passing through the signal conversion circuit and the rectification circuit in sequence.

Detailed ways

As shown in Figure 1, it includes a half-bridge current resonance circuit 1, a signal conversion circuit 2, a rectification circuit 3, a phase detection pulse generation circuit 4 and a combinational logic circuit 5, wherein the output terminal of the current resonance circuit 1 is connected to the output terminal of the signal conversion circuit 2 The input end is connected, the output end of the signal conversion circuit 2 is connected with the input end of the rectification circuit 3, the input end of the phase detection pulse generation circuit 4 is connected with the output end of the rectification circuit 3, and the output end of the phase detection pulse generation circuit 4 is connected with the combinational logic circuit 5. The input terminal and the output terminal of the combinational logic circuit 5 are connected to the current resonance circuit 1 .

There are two power switch tubes in the half-bridge current resonant circuit 1, and the power switch tubes in this embodiment are IGBTs, which are respectively located on the upper and lower bridge arms. As shown in FIG. 4A , assuming that the period of each AC current signal in the half-bridge current resonant circuit 1 is T, the IGBT1 and IGBT2 of the upper and lower bridge arms each work for half a period, ie T/2. The first half cycle is the working cycle of the upper bridge arm IGBT1, and the time is 0-T/2, and the second half cycle is the working cycle of the lower bridge arm IGBT2, and the time is T/2-T;

As shown in FIG. 4B , the AC current signal passes through the signal transformation circuit 2 and the rectification circuit 3 in sequence and then is converted into a DC voltage signal Up, the frequency of which is twice that of the AC current signal, and the phase lags slightly behind the AC current signal. The previous cycle is the working cycle of the upper bridge arm IGBT1, and the time is 0-T/2, and the latter cycle is the working cycle of the lower bridge arm IGBT2, and the time is T/2-T.

The function of the circuit of the present invention is to allow the DC voltage signal Up to generate a high-level pulse signal before crossing the zero voltage (that is, T/4-T/2 and 3T/4-T cycle periods), and the pulse signal time should be long enough, that is The phase detection phase is large, so that the AC current signal is forced to turn off the IGBT before it naturally drops to zero, so as to protect the IGBT.

As shown in the schematic circuit diagram of the embodiment of the present invention in FIG. 3 , the electrical components and their logical connections in the half-bridge current resonant circuit 1 , the signal conversion circuit 2 , and the rectifier circuit 3 are conventional circuits, and will not be repeated here. The phase detection pulse generation circuit 4 includes comparators T41, T42, resistors R41, R42, R43, R44, R45, R46, R47, diode D41, capacitors C41, C42, C43, C44, and transistor Q41.

The negative terminal of the comparator T41 is connected to the resistor R41 and one terminal of the capacitor C41 respectively, and the other terminal of the resistor R41 is connected to the output terminal of the rectifier circuit 3; the other terminal of the capacitor C41 is respectively connected to the positive terminal of the comparator T41, the resistor R42, the resistor R43, One end of the capacitor C42 is connected, the resistor R43 is connected in parallel with the capacitor C42 and grounded, and the other end of the resistor R42 is connected to the switching power supply U1.

The output terminal of the comparator T41 is respectively connected with the capacitor C43, the resistor R44, the anode of the diode D41, the collector of the triode Q41, and the output terminal of the comparator T42. The other end of the capacitor C43 is grounded, the other end of the resistor R44 is connected to the switching power supply U1, the cathode of the diode D41 is used as the phase detection pulse output end, and the emitter of the triode Q41 is grounded. A mains zero-crossing voltage signal U3 is connected to the base of the transistor Q41 through a resistor R47.

The triangular sawtooth wave signal Uj is input to the positive terminal of the comparator T42, and the negative terminal of the comparator T42 is respectively connected to one terminal of the resistors R45, R46 and the capacitor C44. The other end of R46 is connected to the switching power supply U1, and the resistor R45 is connected in parallel with the capacitor C44 to be grounded.

The combinational logic circuit 5 above includes resistors R51, R52; capacitors C53, C54; a Zener diode D51 and an integrated chip X1.

Pin 3 of the integrated chip X1 is connected to the cathode of the diode D41 and the cathode of the Zener diode D51, and the anode of the Zener diode D51 is connected to pins 1 and 16 of the integrated chip X1 and grounded. Pins 2, 13, 14 and 15 of the integrated chip X1 are connected to each other externally. Pin 8 of the integrated chip X1 is connected to the power supply voltage U1. Capacitors C53 and C54 are connected in parallel to form a filter circuit, one end of which is connected to pin 12 of the integrated chip X1 and connected to the power supply voltage U1, and the other ends of capacitors C53 and C54 are respectively connected to pin 11 of the integrated chip X1 and then grounded. Pin 9 and pin 10 of the integrated chip X1 output IGBT driving signals, and are respectively connected to the input control pins of the integrated chip IR2113 through resistors R51 and R52.

Only when the positive terminal voltage of the comparators T41 and T42 is higher than the negative terminal voltage, and the triode Q41 is cut off, can the voltage power supply U1 output a high-level phase detection pulse to the combination logic circuit 5 through the resistor R44 and the diode D41 integrated chip X1, the 9 pins and 10 pins of the integrated chip X1 will output two low-level signals, after limiting the current through resistors R51 and R52, they will be transmitted to the chip IR2113 respectively, then IR2113 will output two low-level signals, so that IGBT1 and IGBT2 are cut off to realize that the AC current signal is forced to turn off the IGBT before it naturally drops to zero, so as to protect the IGBT.

If any one or both of T41 and T42 have a negative terminal voltage higher than the positive terminal voltage, or the triode Q41 is turned on, the diode D41 outputs a low-level signal to the integrated chip X1 in the combinational logic circuit 5, the integrated chip One of pins 9 and 10 of X1 outputs a high-level signal, and the other outputs a low-level signal. After the current is limited by resistors R51 and R52, they are respectively transmitted to the chip IR2113. A low-level signal is output so that one of IGBT1 and IGBT2 is always on, that is, in a normal working state.

The function of the comparator T42 is to make the time for generating the high-level phase detection pulse be between T/4-T/2 or 3T/4-T, that is, before the DC voltage signal Up crosses zero voltage. The implementation method is: the power supply voltage U1 provides a fixed reference voltage Ui to the negative terminal of T42 through the voltage dividing resistors R46 and R45, and the positive terminal of T42 is connected to the triangular sawtooth wave signal Uj. When Uj>Ui, the voltage waveform is between T/4-T/2 or 3T/4-T, so the time to generate the phase detection pulse is between T/4-T/2 or 3T/4-T.

The function of the comparator T41 is to obtain the desired phase t between T/4-T/2 or 3T/4-T. The reference voltage Uk is connected to the negative terminal of the DC voltage signal Up. Assuming that the amplitude of the DC voltage signal is Upmax, then when Uk=0-1/3Upmax, the desired phase t can be obtained.

The base of the transistor Q41 is connected to the mains zero-crossing voltage signal U3, and the working frequency is 100HZ. The function of this signal is to prevent the current phase detection device of the half-bridge induction heating circuit from working when the mains voltage signal crosses zero, so as to avoid false protection. When this signal appears, it is high level, and the time is very short, and the transistor Q41 will be turned on. It is low level most of the time, and the triode Q41 is cut off. Therefore, during most of the time when the whole machine is working, the triode Q41 is in the cut-off state.

Claims (8)

1. a power switching tube protection circuit in a half-bridge induction heating circuit, comprising a current resonance circuit (1), a signal conversion circuit (2), a rectification circuit (3) and a combinational logic circuit (5), the current resonance circuit The output end of (1) is connected with the input end of the signal conversion circuit (2), and the output end of the signal conversion circuit (2) is connected with the input end of the rectification circuit (3); it is characterized in that: it also includes a DC voltage signal that can cross zero A phase detection pulse signal is generated before the voltage, and the phase detection pulse generation circuit (4) that acts on the current resonance circuit (1) to forcibly turn off the power switching tube through the combinational logic circuit (5), the phase detection pulse generation circuit (4) The input end of the rectifier circuit (3) is connected to the output end of the phase detection pulse generating circuit (4) and the input end of the combinational logic circuit (5) is connected, and the output end of the combinational logic circuit (5) is connected to the current resonance circuit (1) Connection. 2. the power switching tube protection circuit in the half-bridge induction heating circuit according to claim 1, is characterized in that: described phase detection pulse generation circuit (4) comprises phase detection circuit (41), synchronous output circuit (42 ), the output terminals of the phase detection circuit (41) and the synchronous output circuit (42) are connected to the input terminals of the combinational logic circuit (5) after passing through the logic relationship of phase and. 3. The power switching tube protection circuit in the half-bridge induction heating circuit according to claim 2, characterized in that: the phase detection circuit (41) includes a comparator T41, a resistor R41, a resistor R42, a resistor R43, and a resistor R44 , capacitor C41, capacitor C42; the negative terminal of comparator T41 is connected with resistance R41, one end of capacitor C41 respectively, and the other end of resistor R41 is connected with the output terminal of rectifier circuit (3); the other end of capacitor C41 is connected with comparator T41 respectively Positive terminal, resistor R42, resistor R43, one end of capacitor C42 is connected, resistor R43 and capacitor C42 are connected in parallel and grounded, and the other end of resistor R42 is connected to power supply voltage U1; Described synchronous output circuit (42) comprises comparator T42, resistance R45, resistance R46, electric capacity C44; The positive end of comparator T42 is connected with triangular sawtooth wave signal Uj input end, and the negative end of comparator T42 is connected with resistance R45, resistance One end of R46 and capacitor C44 are connected; the other end of resistor R46 is connected to power supply voltage U1, resistor R45 is connected in parallel with capacitor C44 and grounded; After the output terminal of the comparator T42 is connected with the output terminal of the comparator T41, it is connected with the power supply voltage U1 through the resistor R44, and connected with the input terminal of the combinational logic circuit (5) through the diode D41. 4. The power switching tube protection circuit in the half-bridge induction heating circuit according to claim 3, characterized in that: the synchronous output circuit (42) also includes a triode Q41, the base of the triode Q41 It is connected with the zero-crossing voltage signal U3 terminal of the mains, the emitter is connected with the power ground, and the collector is connected with the output terminal of the comparator T42. 5. The power switch tube protection circuit in the half-bridge induction heating circuit according to any one of claims 1 to 4, characterized in that: the power switch tube set in the current resonance circuit (1) is an IGBT tube or a MOSFET tube . 6. The power switching tube protection circuit in the half-bridge induction heating circuit according to claim 5, characterized in that: the signal conversion circuit (2) includes a current mutual inductance connected to the current resonance circuit (1) on one side device. 7. The power switch tube protection circuit in the half-bridge induction heating circuit according to claim 6, characterized in that: the rectification circuit (3) is a bridge rectification circuit. 8. The power switching tube protection circuit in the half-bridge induction heating circuit according to claim 7, characterized in that: the combined logic circuit (5) includes a resistor R51, a resistor R52, a capacitor C53, a capacitor C54, and a Zener diode D51 and integrated chip X1; Pin 3 of the integrated chip X1 is connected to the cathode of diode D41 and the cathode of Zener diode D51, and the anode of Zener diode D51 is connected to pin 1 and pin 16 of the integrated chip X1 and grounded; pins 2, 13 and 14 of the integrated chip X1 Connect with pin 15 externally; pin 8 of integrated chip X1 is connected to power supply voltage U1; After the capacitors C53 and C54 are connected in parallel, one end is connected to the 12-pin of the integrated chip X1 and connected to the power supply voltage U1, and the other ends of the capacitors C53 and C54 are respectively connected to the 11-pin of the integrated chip X1 and then grounded; Output IGBT driving signal, and connect with the input control pin of the current resonant circuit (1) through resistors R51 and R52 respectively.

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