WO2010066096A1

WO2010066096A1 - Voltage and current surge protective method and its circuit for induction cooker

Info

Publication number: WO2010066096A1
Application number: PCT/CN2009/001364
Authority: WO
Inventors: 丘守庆; 许申生; 刘春光; 李鹏; 陈劲锋
Original assignee: 深圳市鑫汇科科技有限公司
Priority date: 2008-12-12
Filing date: 2009-12-04
Publication date: 2010-06-17
Also published as: CN101752845A; CN101752845B

Abstract

A voltage and current surge protective method and its circuit for an induction cooker. The method includes the following steps: detecting a surge voltage signal of an input alternate current power supply, and detecting a surge current signal of a main circuit; processing the detected surge voltage and/or current signal by an OR logic circuit (3) to directly switch off an IGBT drive control module (4) so as to switch off the IGBT when the surge voltage and/or current signal are/is detected; at the same time, sending an output signal of the OR logic circuit (3) to a CPU (5) which switches off its output pulse signal, monitors the surge signal, and provides the pulse signal to the IGBT drive control module (4) after a delay of 0.5-2.5 seconds based on the disappearance of the surge signal so as to drive the IGBT by a driver. The voltage and/or current surge signal can be detected rapidly by adopting the method and its circuit to prevent the IGBT from being switched off continually when a small surge pulse signal appears in a power grid.

Description

Voltage and current surge protection method for electromagnetic oven and circuit thereof

The invention belongs to the technical field of induction cooker heated by electric energy, in particular to a voltage and current surge protection method for an induction cooker and a protection circuit thereof. Background technique

Say

At present, the current surge protection circuit of the common induction cooker adopts a current transformer mode, and the primary of the current transformer is connected in series in the alternating current. When a current surge occurs, the secondary inductance of the current transformer is abruptly changed.

Book

The surge signal is detected by a rectifier or the like, and then the voltage comparison judgment is performed by the comparator, directly or through

The CPU turns off the IGBT power output of the induction cooker. This method requires current transformers, rectifiers, etc., which is more complicated, and has a certain delay to the current surge signal, and the protection effect is not ideal.

The surge protection circuit of the common induction cooker is based on the principle of capturing the voltage surge pulse signal on the power grid and immediately turning off the IGBT power output to achieve the protection effect. However, due to the electromagnetic interference in the induction cooker, component parameter error and other factors, the consistency of the surge strength judgment is not good, and its protection effect is not good. For example: In the mass-produced induction cooker, when some products have a small surge pulse signal in the power grid, they should not be protected but frequently protect the IGBT driver from being turned off, resulting in the induction cooker not being able to output power normally. Some products cannot capture and turn off the IGBT power output when there is a surge pulse signal in the electric meat. Summary of the invention

In order to avoid the above defects existing in the existing induction cooker technology, the present invention provides a voltage and current surge protection method for an induction cooker and a protection circuit for detecting a voltage surge pulse signal of an alternating current connected to the induction cooker and a current wave in the output main circuit. The surge pulse signal provides voltage and current surge protection to the induction cooker system through an IGBT drive control module and CPU. The voltage and current surge protection method for the induction cooker of the present invention takes the following steps:

The voltage surge detection circuit is used to detect the surge voltage signal of the input AC power source, and the current surge detection circuit is used to detect the surge current signal of the main circuit;

When the surge voltage and/or current signal is captured, the measured surge voltage and/or current signal is directly turned off by an OR logic circuit to stop the IGBT drive control module to stop outputting the pulse signal, so that the IGBT is turned off; The output signal of the logic circuit is sent to the CPU, the CPU turns off the pulse signal outputted to the IGBT drive control module, and monitors the surge voltage and/or current signal. After the surge signal disappears, the delay is 0.5~2.5 seconds, and then the IGBT is turned to the IGBT. The drive control module provides a pulse signal that drives the IGBT through the driver.

The voltage surge detecting circuit includes a first comparator and a surge voltage sampling circuit for collecting a surge voltage signal of the input AC power source, and an output signal of the surge voltage sampling circuit is connected to the non-inverting input end of the first comparator; The current surge detecting circuit includes a second comparator, and a surge current sampling circuit composed of a current sampling resistor connected in series between the rectifier bridge and the IGBT and two voltage dividing resistors connected to the current sampling resistor, The output signal of the inrush current sampling circuit is connected to the inverting input terminal of the second comparator, and the non-inverting input terminal of the second comparator is grounded. A voltage and current surge protection circuit for an induction cooker implementing the above method, comprising:

a voltage surge detecting circuit, comprising: a first comparator and a surge voltage sampling circuit for collecting a surge voltage signal of the input AC power source, wherein the output signal of the surge voltage sampling circuit is connected to the non-inverting input terminal of the first comparator ;

a current surge detecting circuit, the detecting circuit comprising a second comparator, and a current sampling resistor connected between the rectifier bridge and the IGBT and a surge current sampling formed by two voltage dividing resistors connected to the current sampling resistor a circuit, an output signal of the inrush current sampling circuit is connected to an inverting input end of the second comparator, and a non-inverting input end of the second comparator is grounded;

Or a logic circuit, wherein two input terminals of the OR circuit are respectively connected to an output end of the first comparator and an output end of the second comparator;

— IGBT drive control module, a control terminal and an input terminal of the IGBT drive control module respectively Connecting the output of the logic circuit and the pulse signal output end of the CPU, and the output of the OR logic circuit is connected to the CPU-input terminal; when capturing a surge voltage and/or current signal, the OR logic The circuit processing directly turns off the IGBT drive control module to stop outputting the pulse signal, and the CPU turns off its pulse signal output, and monitors the surge voltage and/or current signal to wait for the surge to disappear after a delay of 0.5 to 2.5 seconds, and then to the IGBT. The drive control module provides a pulse signal that drives the IGBT through a driver.

The first comparator, the second comparator, or the logic circuit, the IGBT drive control module, and the CPU are all integrated in one SoC (System on a Chip) chip. The SoC chip is preferably a CHK-S008 type SoC chip packaged in a 16 PIN package. The voltage and current surge protection circuit for the electromagnetic circuit of the invention can quickly capture voltage and current surge signals, and when the surge voltage and/or current signal is captured, the logic control circuit directly shuts down the 1GBT drive control module to stop output. Pulse signal, at the same time, the CPU turns off its pulse signal output, and monitors the surge signal for a certain time after the surge disappears, and then starts the IGBT operation. The protection effect is good, and at the same time, the traditional induction cooker avoids a small surge pulse signal in the power grid, frequently turns off the IGBT driver, which causes the induction cooker to fail to output power and heat.

By adjusting the voltage division ratio of the two voltage dividing resistors in the surge current sampling circuit, the protected surge current threshold can be set, the parameter setting is convenient and flexible, and the circuit is simplified. The diode D3 and the capacitor C13 in the surge voltage sampling circuit are The setting has a significant effect on filtering out environmental noise, which is beneficial to distinguish between environmental noise and surge voltage signals, effectively improve the signal-to-noise ratio of the sampling circuit, and can more reliably and accurately identify the intensity of voltage surges, thus For better protection.

Based on the SoC chip technology, several on-chip comparators, or logic circuits, IGBT drive control modules, and CPU are not susceptible to external interference, and the peripheral circuits are simple, which greatly reduces the difficulty and cost of production and maintenance. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing the principle of a voltage and current surge protection circuit for an induction cooker according to the present invention;

2 is a circuit diagram of an exemplary embodiment of the protection circuit of FIG. 1. detailed description

The invention is further described below in conjunction with the drawings.

Referring to Figure 1, the voltage and current surge protection circuit for the induction cooker mainly includes:

The voltage surge detecting circuit comprises a comparator 1 and a surge voltage sampling circuit for collecting a surge voltage signal of the input AC power source, the output signal of the surge voltage sampling circuit is connected to the non-inverting input end of the first comparator; the current surge detecting circuit The circuit includes a second comparator, and a surge current sampling circuit formed by a current sampling resistor connected in series between the rectifier bridge and the IGBT and two voltage dividing resistors connected to the current sampling resistor, the surge current sampling The output signal of the circuit is connected to the inverting input of the comparator 2, and the non-inverting input of the comparator 2 is grounded;

An IGBT drive control module, a control end and an input end of the IGBT drive control module are respectively connected to an output end of the OR logic circuit and a pulse signal output end of the CPU, and an output end of the OR logic circuit is connected to the CPU- Input.

The comparator 1, the comparator 2, or the logic circuit, the IGBT drive control module, and the CPU are all integrated in one SoC chip, and the SoC chip is preferably a CHK-S008 type SoC chip in a 16 PIN package.

The OR logic circuit may consist of a 2-input NOR gate and an inverter connected to the 2-input NOR gate output, or a 2-input OR gate.

The IGBT drive control module is further provided with another control end and a feedback end. The pulse signal outputted by the IGBT drive control module can be fed back to the IGBT drive control module through a feedback circuit to correct the IGBT drive waveform, optimize the pulse signal waveform, and improve Work efficiency. A typical embodiment is shown in FIG. 2. This embodiment adopts the above-mentioned CHK-S008 type SoC chip, and the comparator 1, the comparator 2, the 2 input terminal or the gate circuit, the IGBT drive control module, and the CPU are all built in the CHK-S008 type. Inside the SoC chip. Wherein, the filter is composed of an inductor L1 and a capacitor C4, and the IGBT And the LC resonant circuit (L3 and C3) constitutes a power inverter circuit.

The comparator 1 and the surge voltage sampling circuit in the CHK-S008 SoC chip form a voltage surge detection circuit, and the output signal of the surge voltage sampling circuit is connected to the non-inverting input terminal (1 PIN) of the comparator 1.

The surge voltage sampling circuit includes diodes D1 and D2 respectively connected to the AC input line of the rectifier bridge BG1, a diode D3 connected to the cathode of the diode D1 and D2, and a series resistor R19, R20 and R21 connected between the cathode of the diode D3 and the ground. Resistors R20 and R21 are respectively connected in parallel with capacitors C 14 and C 15. The cathode of diode D3 is grounded through capacitor C 13 , and the common terminal output sampling signals of resistors R20 and R21 are connected to the non-inverting input terminal of comparator 1 . The inverting input terminal is connected to the reference voltage Vref. The diode D3 and capacitor C13 of this circuit are set to have a significant effect on filtering out environmental interference, which is beneficial to distinguish between ambient noise and surge voltage signals. When the surge voltage signal is captured, the comparator 1 outputs a high level, and is connected to a control terminal of the IGBT drive control module and the CPU-input terminal through the 2-input or gate circuit, and directly shuts down. The IGBT drive control module stops outputting the pulse signal to protect the IGBT; at the same time, the CPU receives the voltage surge signal to turn off the pulse signal output, and monitors the surge voltage signal to wait for the surge to disappear after 0.5~2.5 seconds, and then The IGBT drive control module provides a pulse signal, which in turn drives the IGBT through a driver connected to the gate of the IGBT.

The comparator 2 and the inrush current sampling circuit in the CHK-S008 SoC chip constitute a current surge detecting circuit, and the output signal of the surge voltage sampling circuit is connected to the inverting input terminal (11 PIN) of the comparator 2, and the non-inverting input Grounded at the end.

The inrush current sampling circuit is composed of a constant copper wire resistance RK1 connected in series between the rectifier bridge BG1 and the IGBT drain, and two voltage dividing resistors Rl l, R10 connected to the constant copper wire resistance RK1, and the resistor R11 is connected in parallel with the capacitor C4. One end of R10 is connected to the power supply Vcc +5V, the output signal of the inrush current sampling circuit is connected to the inverting input terminal of the comparator 2, and the non-inverting input terminal of the comparator 2 is grounded to GND. The constant copper wire resistance RK1 is connected in series between the rectifier bridge BG1 and the IGBT drain. When the induction cooker current changes, the voltage across the constant copper wire resistance RK1 will also change accordingly. The capacitor C4 connected in parallel with R11 mainly filters out the noise. When the induction cooker is in normal heating state, when the operating current is lower than the maximum limit value, the voltage at the inverting terminal of the comparator 2 is greater than the non-inverting terminal; when the current of the induction cooker suddenly increases, the voltage at the inverting terminal of the comparator 2 suddenly drops, lower than the level of the non-inverting terminal. At GND, the comparator 2 outputs a high level, and the IGBT drive is connected through the 2-input or gate circuit. A control terminal of the dynamic control module and the CPU-input terminal directly turn off the IGBT drive control module to stop outputting the pulse signal to protect the IGBT safety; the same CPU receives the voltage surge signal to turn off the pulse signal output, and monitors the wave. The surge voltage signal is delayed by 0.5~2.5 seconds after the surge disappears, and then the pulse signal is supplied to the IGBT drive control module, and then the IGBT is driven by a driver connected to the gate of the IGBT. The voltage and current surge protection method for the induction cooker realized by the circuit of the embodiment of FIG. 2 is as follows: The voltage surge detection circuit is used to detect the surge voltage signal of the input AC power source, and the current surge detection circuit is used to detect the wave of the main circuit. Inrush current signal

When the surge voltage and/or current signal is captured, the measured surge voltage and/or current signal is directly turned off by the processing of the CHK-S008 type SoC chip or the logic circuit to stop the output pulse signal. The IGBT is turned off; at the same time, the output signal of the logic circuit is sent to the CPU, the CPU turns off the pulse signal outputted to the IGBT drive control module, and monitors the surge voltage and/or current signal, and the delay is 0.5 after the surge signal disappears. ~2.5 seconds, and then provide pulse signal to the IGBT drive control module, the IGBT drive control module output pulse signal pushes the IGBT through the driver connected to the IGBT gate.

Claims

Claim

1. A voltage and current surge protection method for an induction cooker, comprising the following steps:

When the surge voltage and/or current signal is captured, the measured surge voltage and/or current signal is directly turned off by an OR logic circuit to stop the IGBT drive control module to stop outputting the pulse signal, so that the IGBT is turned off; The output signal of the logic circuit is sent to the CPU, the CPU turns off the pulse signal outputted to the IGBT drive control module, and monitors the surge voltage and/or current signal. After the surge signal disappears, the delay is 0.5~2.5 seconds, and then the IGBT is turned to the IGBT. The drive control module provides a pulse signal that drives the IGBT through a driver.

2. The voltage and current surge protection method for an induction cooker according to claim 1, wherein: said voltage surge detecting circuit comprises a first comparator and a surge voltage sampling circuit for collecting a surge voltage signal of the input AC power source, An output signal of the surge voltage sampling circuit is connected to a non-inverting input terminal of the first comparator; the current surge detecting circuit includes a second comparator, and a current sampling resistor connected in series between the rectifier bridge and the IGBT and connected to An inrush current sampling circuit is formed by two voltage dividing resistors of the current sampling resistor, an output signal of the inrush current sampling circuit is connected to an inverting input end of the second comparator, and a non-inverting input end of the second comparator is grounded.

3. A voltage and current surge protection method for an induction hob according to claim 1 or 2, wherein - said OR logic circuit is inverted by a 2-input NOR gate and connected to said 2-input NOR gate output. Composition.

4. A voltage and current surge protection circuit for an induction cooker, characterized in that:

a current surge detecting circuit, the detecting circuit comprising a second comparator, and comprising a current sampling resistor connected in series between the rectifier bridge and the IGBT and two voltage dividing resistors connected to the current sampling resistor a surge current sampling circuit, wherein an output signal of the inrush current sampling circuit is connected to an inverting input end of the second comparator, and a non-inverting input end of the second comparator is grounded;

A voltage and current surge protection circuit for an induction cooker according to claim 4, wherein: said first comparator, said second comparator, or logic circuit, IGBT drive control module and CPU are integrated in one SoC chip .

6. A voltage and current surge protection circuit for an induction cooktop according to claim 4 or 5, wherein: said OR logic circuit is a 2-input or gate.

7. The voltage and current surge protection circuit for an induction cooktop according to claim 4 or 5, wherein: said OR logic circuit is inverted by a 2-input NOR gate and connected to said 2-input NOR gate output terminal. Composition.

A voltage and current surge protection circuit for an induction cooker according to claim 5, wherein: ???said SoC chip is a CHK-S008 type SoC chip of 16 PI package.

A voltage and current surge protection circuit for an induction cooker according to claim 4, wherein: said surge voltage sampling circuit comprises diodes D1 and D2 respectively connected to the two AC input lines of the rectifier bridge, and positive connection diodes D1 and D2. The diode D3 of the negative electrode is connected to the series resistor R19, R20, R21 between the negative pole of the diode D3 and the ground, and the resistors R20 and R21 are respectively connected in parallel with a capacitor. The cathode of the diode D3 is grounded through another capacitor, and the common ends of the resistors R20 and R21. The output signal is coupled to the non-inverting input of the first comparator within the SoC chip.

A voltage and current surge protection circuit for an induction cooker according to claim 4 or 9, wherein: said surge current sampling circuit comprises a constant copper wire resistor connected in series between the rectifier bridge and the IGBT drain

RK1 is composed of two voltage dividing resistors R1, R10 connected to the constant copper wire resistor K1, and its output signal is connected to the inverting input terminal of the second comparator, and the non-inverting input terminal of the second comparator is grounded.