CN111509664A

CN111509664A - Three-stage back-voltage protection circuit of chip special for electromagnetic oven

Info

Publication number: CN111509664A
Application number: CN202010385883.8A
Authority: CN
Inventors: 缪建斌; 胡川
Original assignee: CROWN RICH ELECTRONIC (SHENZHEN) CO LTD
Current assignee: CROWN RICH ELECTRONIC (SHENZHEN) CO LTD
Priority date: 2020-05-09
Filing date: 2020-05-09
Publication date: 2020-08-07

Abstract

The invention relates to a three-stage back-voltage protection circuit of a chip special for an induction cooker. The three-stage back pressure protection circuit of the special chip for the induction cooker comprises a rectifying filter circuit, a wire coil resonance and driving circuit, an IGBT driving circuit, a synchronous circuit, a surge signal acquisition circuit and an MCU control chip, wherein the synchronous circuit comprises a back pressure acquisition circuit, and the MCU control chip comprises a CPU, a comparator COMP1, a comparator COMP2, a comparator COMP3, a PPG control circuit and a surge protection circuit. Compared with the traditional special chip for the induction cooker, the three-level back-pressure protection circuit for the special chip for the induction cooker provided by the application can properly increase the back pressure VCE and increase the power; and the output of PPG can be timely reduced when a weak surge signal arrives, and the driving pulse width of the next IGBT is not wide even if a small surge signal exists, so that the back pressure of the next IGBT is not high.

Description

Three-stage back-voltage protection circuit of chip special for electromagnetic oven

Technical Field

The invention relates to the technical field of induction cookers, in particular to a three-level back-pressure protection circuit of a chip special for an induction cooker.

Background

At present, a special chip for an induction cooker is provided with a back-pressure protection circuit (back pressure, namely the voltage of a C pole of an IGBT to an E pole of the IGBT, namely VCE), and the purpose of adopting the circuit is to ensure that the back-pressure VCE of the IGBT does not exceed rated maximum withstand voltage (for example 1200V).

However, the existing back-voltage protection generally adopts one stage, that is, when the VCE of the IGBT is close to the rated maximum value, the sampled voltage of the VCE allows the comparator to output a falling edge signal, which allows the MCU to generate an interrupt, and appropriately reduces the pulse width of the PPG in the interrupt service routine, thereby ensuring that the VCE does not exceed the standard. In order to increase the power of the induction cooker, manufacturers can increase the actual working voltage of the VCE as much as possible, but due to cost factors, the manufacturers rarely select the IGBT with high VCE voltage resistance. Therefore, the actual operating voltage of the VCE of the IGBT is usually made close to the rated maximum voltage, and there is little margin for the operating voltage of the VCE. Since surge voltage is often present in the commercial power, the voltage of the VCE is abnormally increased. If the IGBT operates normally with little margin for VCE, even a weak surge signal can cause VCE to exceed the rated maximum, resulting in IGBT damage.

Disclosure of Invention

The invention aims to provide a three-stage back pressure protection circuit of a special chip for an induction cooker, which can not only properly improve the power of the induction cooker, but also ensure that the IGBT back pressure is not high when a weak surge signal comes.

In order to realize the purpose of the invention, the invention adopts the following technical scheme:

a three-stage back pressure protection circuit of a chip special for an induction cooker comprises a rectifying filter circuit, a wire coil resonance and driving circuit, an IGBT driving circuit, a synchronous circuit, a surge signal acquisition circuit and an MCU control chip, wherein the synchronous circuit comprises a back pressure acquisition circuit, and the MCU control chip comprises a CPU, a comparator COMP1, a comparator COMP2, a comparator COMP3, a PPG control circuit and a surge protection circuit;

the input end of the rectification filter circuit is connected with a live wire and a zero wire of an external alternating current power supply, the first output end of the rectification filter circuit is connected with the first input end of the wire coil resonance and driving circuit, and the output end of the wire coil resonance and driving circuit is connected with a wire coil of the induction cooker; the second output end of the rectification filter circuit is connected with the input end of the surge protection circuit through the surge signal acquisition circuit;

the output end of the wire coil resonance and driving circuit is connected with the input end of the synchronous circuit, and the output end of the synchronous circuit is respectively connected with the negative phase input end of the comparator COMP1, the negative phase input end of the comparator COMP2, the negative phase input end of the comparator COMP3 and the first input end of the PPG control circuit; the input end of the CPU is connected to the output end of the surge protection circuit, the output end of the comparator COMP1, the output end of the comparator COMP2, and the output end of the comparator COMP3, respectively; the output end of the CPU is connected to the positive-phase input end of the comparator COMP1, the positive-phase input end of the comparator COMP2, the positive-phase input end of the comparator COMP3, and the second input end of the PPG control circuit, respectively; a third input end of the PPG control circuit is connected to an output end of the surge protection circuit, an output end of the comparator COMP1, an output end of the comparator COMP2, and an output end of the comparator COMP3, respectively; and the output end of the PPG control circuit is connected with the second input end of the wire coil resonance and driving circuit through the IGBT driving circuit.

Compared with the traditional special chip for the induction cooker, the three-level back-pressure protection circuit for the special chip for the induction cooker provided by the application can properly increase the back pressure VCE and increase the power; and the output of PPG can be timely reduced when a weak surge signal arrives, and the driving pulse width of the next IGBT is not wide even if a small surge signal exists, so that the back pressure of the next IGBT is not high. Namely, a stage of pre-protection is added before the IGBT stops working, so that the IGBT can not be protected and shut down due to a weak surge signal under the condition that the actual working voltage of the VCE is properly increased. The three-stage back-voltage protection circuit also has the following functions: when a user lifts the pot quickly, the load of the circuit is suddenly reduced, the back pressure of the IGBT can also be increased abnormally, the IGBT can be damaged, and the IGBT can be quickly turned off by the three-stage back pressure protection circuit when the user lifts the pot quickly, so that the IGBT is prevented from being damaged. When parameters of the wire coil resonance circuit are suddenly changed (for example, the capacity of the wire coil resonance capacitor is suddenly reduced), the back pressure of the IGBT is also abnormally increased, and under the condition, the three-stage back pressure protection circuit can rapidly turn off the IGBT to prevent the IGBT from being damaged.

In one embodiment, the PPG control circuit includes a PPG generator, a PPG stop circuit, a PPG large reduction circuit, and a PPG small reduction circuit, where a first input terminal of the PPG generator is connected to an output terminal of the PPG stop circuit, an output terminal of the PPG large reduction circuit, and an output terminal of the PPG small reduction circuit, respectively, and an output terminal of the PPG generator is connected to a second input terminal of the wire coil resonance and driving circuit through the IGBT driving circuit;

the CPU comprises an MCU core component and an MCU interruption module, wherein the input end of the MCU interruption module is respectively connected with the output end of the comparator COMP1, the output end of the comparator COMP2, the output end of the comparator COMP3 and the output end of the surge protection circuit, and the output end of the MCU interruption module is connected with the input end of the MCU core component; the output end of the MCU core is connected to the positive input end of the comparator COMP1, the positive input end of the comparator COMP2, and the positive input end of the comparator COMP3, respectively, and the first input end of the PPG stop circuit, the first input end of the PPG large reduction circuit, the first input end of the PPG small reduction circuit, and the second input end of the PPG generator are connected to each other; a second input end of the PPG stop circuit is connected to an output end of the surge protection circuit and an output end of the comparator COMP3, respectively; a second input end of the PPG amplitude reduction circuit is connected to an output end of the comparator COMP 2; a second input end of the PPG small amplitude reduction circuit is connected to an output end of the comparator COMP 1; and a third input end of the PPG generator is connected with an output end of the synchronous circuit.

In one embodiment, the rectifying and filtering circuit includes an X capacitor C1, an X capacitor C2, a common mode inductor T1, a choke coil L2, and a rectifying bridge stack BG1, a first end of the X capacitor C1 and a first input end of the common mode inductor T1 are both connected to the live line, a first output end of the common mode inductor T1 is respectively connected to a first end of the X capacitor C2 and a first ac input end of the rectifying bridge stack BG1, an anode of a dc output end of the rectifying bridge stack BG1 is connected to a first end of the choke coil L2, a second end of the X capacitor C1 and a second input end of the common mode inductor T1 are both connected to the neutral line, a second output end of the common mode inductor T1 is respectively connected to a second end of the X capacitor C2 and a second ac input end of the rectifying bridge stack BG1, and a cathode of the dc output end of the rectifying bridge stack BG1 is grounded.

In one embodiment, the coil resonance and driving circuit includes a capacitor C3, a capacitor C4, a resistor R1, a resistor R2, and an IGBT Q1, wherein a second end of the choke L2 is respectively connected to a first end of the capacitor C3, a first end of the capacitor C4, and a first end of the coil of the induction cooker, a second end of the capacitor C3 is grounded, a second end of the coil of the induction cooker is respectively connected to a second end of the capacitor C4 and a collector of the IGBT Q1, a gate of the IGBT Q1 is respectively connected to a first end of the resistor R1 and a first end of the resistor R2, and a second end of the resistor R1 is grounded to an emitter of the IGBT Q1.

In one embodiment, the synchronization circuit comprises a resistor R3, a resistor R4, a resistor R5, a resistor R6, a capacitor C5 and a capacitor C6, a first end of the resistor R3 is connected to a first end of the induction cooker wire coil, and a second end of the resistor R3 is connected to a first end of the resistor R5, a first end of the capacitor C5, a first end of the capacitor C6 and a third input end of the PPG generator, respectively; a first end of the resistor R4 is connected to a second end of the coil of the induction cooker, a second end of the resistor R4 is connected to a first end of the resistor R6, a second end of the capacitor C5, a negative phase input end of the comparator COMP1, a negative phase input end of the comparator COMP2, a negative phase input end of the comparator COMP3, and a third input end of the PPG generator, and a second end of the resistor R5, a second end of the resistor R6, and a second end of the capacitor C6 are all grounded.

In one embodiment, the IGBT driving circuit includes a transistor Q2, a transistor Q3, a transistor Q4, a diode D1, a resistor R7, a resistor R8, a resistor R9, a capacitor C7, and an electrolytic capacitor EC1, wherein a second terminal of the resistor R2 is respectively connected to an anode of the diode D1, an emitter of the transistor Q2, and an emitter of the transistor Q3, a cathode of the diode D1, a first terminal of the resistor R7, a first terminal of the resistor R8, a first terminal of the resistor R9, a first terminal of the capacitor C7, and an anode of the electrolytic capacitor EC1 are respectively connected to an 18V power supply, a second terminal of the resistor R7 is connected to a collector of the transistor Q2, a base of the transistor Q2 is respectively connected to a second terminal of the resistor R8, a base of the transistor Q3, a collector of the transistor Q4, and a base of the transistor Q4 is respectively connected to a second terminal of the resistor R9, The output end of the PPG generator is connected, and the collector of the triode Q3, the emitter of the triode Q4, the second end of the capacitor C7 and the negative electrode of the electrolytic capacitor EC1 are all grounded.

In one embodiment, the surge signal acquisition circuit includes a diode D2, a diode D3, a resistor R10, a resistor R11, a resistor R12, a capacitor C8, and a capacitor C9, an anode of the diode D2 is connected to a first output terminal of the common-mode inductor T1, an anode of the diode D3 is connected to a second output terminal of the common-mode inductor T1, a cathode of the diode D2, a cathode of the diode D3, and a first end of the resistor R10 are connected to a first end of the capacitor C8 in common, a first end of the resistor R11 is connected to a second end of the resistor R10 and a second end of the capacitor C8, a second end of the resistor R11 is connected to a first end of the resistor R12, a first end of the capacitor C9, and an input terminal of the surge protection circuit, and a second end of the resistor R12 is connected to a second end of the capacitor C9.

Drawings

FIG. 1 is a schematic structural diagram of a three-level back-voltage protection circuit of a chip dedicated for an induction cooker in an embodiment;

FIG. 2 is a schematic circuit diagram of a rectifying and filtering circuit according to an embodiment;

FIG. 3 is a schematic diagram of the electrical circuit of the coil resonance and actuation circuit in one embodiment;

FIG. 4 is a schematic circuit diagram of a synchronization circuit according to an embodiment;

FIG. 5 is a schematic circuit diagram of an IGBT driving circuit according to an embodiment;

fig. 6 is a schematic circuit diagram of a surge signal acquisition circuit in an embodiment.

Detailed Description

To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature.

Referring to fig. 1, the embodiment provides a three-stage back pressure protection circuit of a chip dedicated for an induction cooker, which includes a rectifying and filtering circuit, a wire coil resonance and driving circuit, an IGBT driving circuit, a synchronization circuit, a surge signal acquisition circuit, and an MCU control chip, where the synchronization circuit includes the back pressure acquisition circuit, and the MCU control chip includes a CPU, a comparator COMP1, a comparator COMP2, a comparator COMP3, a PPG control circuit, and a surge protection circuit;

the input end of the rectification filter circuit is connected with a live wire (L) and a zero wire (N) of an external alternating current power supply, the first output end of the rectification filter circuit is connected with the first input end of the wire coil resonance and driving circuit, and the output end of the wire coil resonance and driving circuit is connected with a wire coil of the induction cooker;

the output end of the wire coil resonance and driving circuit is connected with the input end of the synchronous circuit, and the output end of the synchronous circuit is respectively connected with the negative phase input end of the comparator COMP1, the negative phase input end of the comparator COMP2, the negative phase input end of the comparator COMP3 and the first input end of the PPG control circuit; the input end of the CPU is respectively connected with the output end of the surge protection circuit, the output end of a comparator COMP1, the output end of a comparator COMP2 and the output end of a comparator COMP 3; the output end of the CPU is connected to the positive-phase input end of the comparator COMP1, the positive-phase input end of the comparator COMP2, the positive-phase input end of the comparator COMP3, and the second input end of the PPG control circuit, respectively; a third input end of the PPG control circuit is connected with an output end of the surge protection circuit, an output end of the comparator COMP1, an output end of the comparator COMP2 and an output end of the comparator COMP3 respectively; the output end of the PPG control circuit is connected with the second input end of the wire coil resonance and driving circuit through the IGBT driving circuit.

The PPG control circuit comprises a PPG generator, a PPG stopping circuit, a PPG large-amplitude reduction circuit and a PPG small-amplitude reduction circuit, wherein a first input end of the PPG generator is respectively connected with an output end of the PPG stopping circuit, an output end of the PPG large-amplitude reduction circuit and an output end of the PPG small-amplitude reduction circuit, and an output end of the PPG generator is connected with a second input end of the wire coil resonance and driving circuit through an IGBT driving circuit; the CPU comprises an MCU core component and an MCU interruption module, wherein the input end of the MCU interruption module is respectively connected with the output end of a comparator COMP1, the output end of a comparator COMP2, the output end of a comparator COMP3 and the output end of a surge protection circuit, and the output end of the MCU interruption module is connected with the input end of the MCU core component; the output end of the MCU core component is respectively connected with the positive phase input end of a comparator COMP1, the positive phase input end of a comparator COMP2 and the positive phase input end of a comparator COMP3, and the first input end of the PPG stopping circuit, the first input end of the PPG large amplitude reduction circuit, the first input end of the PPG small amplitude reduction circuit and the second input end of the PPG generator are connected; a second input end of the PPG stopping circuit is respectively connected with an output end of the surge protection circuit and an output end of a comparator COMP 3; a second input end of the PPG large amplitude reduction circuit is connected with an output end of a comparator COMP 2; a second input end of the PPG small amplitude reduction circuit is connected with an output end of a comparator COMP 1; and a third input end of the PPG generator is connected with an output end of the synchronous circuit.

In the present embodiment, the non-inverting input terminal of the comparator COMP1 is connected to the reference voltage V1, the non-inverting input terminal of the comparator COMP2 is connected to the reference voltage V2, the non-inverting input terminal of the comparator COMP3 is connected to the reference voltage V3, and V3> V2> V1. The values of the three reference voltages V1, V2 and V3 are controlled by the MCU core, and the user can change the sizes of V1, V2 and V3 through software.

The MCU core component can be used for controlling the starting and stopping of the pulse width of the PPG generator, sending the set value of the PPG pulse width to the PPG generator, and adjusting the reference voltages V1, V2 and V3 at the positive phase input end of the 3 comparators. The PPG pulse width set value, which is loaded into the PPG generator at the falling edge of the output of comparator COMP3, is written to the PPG large reduction circuit. Writing a PPG pulse width set value into a PPG small amplitude reduction circuit, wherein the PPG pulse width set value is loaded into a PPG generator at the falling edge of the output of a comparator COMP 2; the MCU core component can also enable or close the PPG stopping circuit and determine whether the PPG stopping circuit can stop the PPG output of the PPG generator.

The MCU interrupt module is used for processing interrupt signals sent by the three comparators of the back voltage protection circuit and the surge protection circuit.

The PPG small amplitude reduction circuit is used for increasing the back pressure of the IGBT if the PPG pulse width is too wide when no surge signal comes, the back pressure acquisition voltage V exceeds V1, the comparator COMP1 outputs a falling edge signal to the PPG small amplitude reduction circuit, and the module sends a value slightly lower than the current PPG pulse width to the PPG generator, so that the PPG pulse width is reduced in a small amplitude manner; the PPG large reduction circuit is used for outputting a falling edge signal output by the comparator COMP2 to the PPG large reduction circuit when a weak surge signal comes, the back voltage acquisition voltage V exceeds V2, the module sends a value far lower than the current PPG pulse width to the PPG generator, and therefore the PPG pulse width is greatly reduced; the PPG stop circuit is used for when a strong surge signal arrives and a user quickly lifts a pot or a wire coil resonant loop parameter changes suddenly (for example, the capacity of a wire coil resonant capacitor is suddenly reduced), the back pressure acquisition voltage V exceeds V3, the comparator COMP3 outputs a falling edge signal to the PPG stop circuit, and the module immediately cuts off the pulse output of the PPG generator.

The MCU control chip has the following three-level back pressure protection process:

when no surge signal comes, if the pulse width of PPG is too wide, the back pressure of the IGBT is increased, the back pressure acquisition voltage V exceeds V1, the output level of a comparator COMP1 is inverted at a falling edge, the falling edge signal is sent to a PPG small amplitude reduction circuit, the output pulse width of the PPG is properly reduced (a PPG pulse set value slightly lower than the current PPG pulse width is sent to a PPG generator), the falling edge signal can also be used as an interrupt signal to be sent to an MCU interrupt module, an MCU core component can properly reduce the output pulse width of the PPG in an interrupt service program, and the back pressure VCE of the IGBT is guaranteed not to exceed the standard;

when a weak surge signal comes, the back pressure acquisition voltage V exceeds V2, the output level of the comparator COMP2 is inverted by a falling edge, the falling edge signal is sent to a PPG large-amplitude reduction circuit on one hand, the PPG output pulse width is immediately and greatly reduced (a PPG pulse set value far lower than the current PPG pulse width is sent to a PPG generator), and the back pressure VCE of the next IGBT does not exceed the standard. On the other hand, the falling edge signal is sent to the MCU interruption module as an interruption signal, so that the MCU core component generates interruption, the MCU core component can recover normal power output in a short time, and the MCU core component still continuously heats in the view of a user;

when a strong surge signal arrives and a user quickly lifts a pot or a wire coil resonant loop parameter suddenly changes (for example, the capacity of a wire coil resonant capacitor suddenly becomes smaller), the back pressure acquisition voltage V exceeds V3, the output level of the comparator COMP3 is inverted at a falling edge, and the falling edge signal is sent to a PPG stop circuit to immediately turn off the PPG output. On the other hand, the falling edge signal is sent to an MCU interrupt module of the singlechip, so that the singlechip is interrupted, and the singlechip restarts the electromagnetic heating after delaying for several seconds. That is, when a strong surge pulse comes, the single chip will stop working for several seconds and then start heating.

In one embodiment, referring to fig. 2, the rectifying and filtering circuit includes an X capacitor C1, an X capacitor C2, a common mode inductor T1, a choke coil L2, and a rectifying bridge BG1, a first end of the X capacitor C1 and a first input end of the common mode inductor T1 are both connected to a live line, a first output end of the common mode inductor T1 is respectively connected to a first end of the X capacitor C2 and a first ac input end of the rectifying bridge BG1, an anode of a dc output end of the rectifying bridge BG1 is connected to a first end of the choke coil L2, a second end of the X capacitor C1 and a second input end of the common mode inductor T1 are both connected to a neutral line, a second output end of the common mode inductor T1 is respectively connected to a second end of the X capacitor C2 and a second ac input end of the rectifying bridge BG1, and a cathode of the dc output end of the rectifying bridge BG1 is grounded.

In the embodiment, commercial power signals coming from a live wire (L) and a neutral wire (N) form filtered signals L1 and N1 through an X capacitor C1, a common-mode inductor T1 and an X capacitor C2, are rectified through a rectifier bridge stack BG1, and are filtered by a choke coil L2 to be sent to a wire coil resonance and driving circuit.

In one embodiment, referring to fig. 3, the coil resonance and driving circuit includes a capacitor C3, a capacitor C4, a resistor R1, a resistor R2, and an IGBT Q1, wherein a second terminal of a choke L2 is respectively connected to a first terminal of the capacitor C3, a first terminal of the capacitor C4, and a first terminal of a coil of the induction cooker, a second terminal of the capacitor C3 is grounded, a second terminal of the coil of the induction cooker is respectively connected to a second terminal of the capacitor C4 and a collector of the IGBT Q1, a gate of the IGBT Q1 is respectively connected to a first terminal of the resistor R1 and a first terminal of the resistor R2, and a second terminal of the resistor R1 is grounded to an emitter of the IGBT Q1.

In this embodiment, the coil at the CO L1 and CO L2 ports forms a parallel resonant circuit with capacitor C4Q 1 is an IGBT for energizing the resonant circuit.

In one embodiment, referring to fig. 4, the synchronization circuit includes a resistor R3, a resistor R4, a resistor R5, a resistor R6, a capacitor C5, and a capacitor C6, a first end of the resistor R3 is connected to a first end of a coil of the induction cooker, and a second end of the resistor R3 is connected to a first end of the resistor R5, a first end of the capacitor C5, a first end of the capacitor C6, and a third input terminal of the PPG generator, respectively; the first end of the resistor R4 is connected with the second end of the induction cooker wire coil, the second end of the resistor R4 is respectively connected with the first end of the resistor R6, the second end of the capacitor C5, the negative phase input end of the comparator COMP1, the negative phase input end of the comparator COMP2, the negative phase input end of the comparator COMP3 and the third input end of the PPG generator, and the second end of the resistor R5, the second end of the resistor R6 and the second end of the capacitor C6 are all grounded.

In this embodiment, voltages V _ DC and V _ IGBT _ C at two ends of the wire coil are divided by a resistor R3, a resistor R5, a resistor R4 and a resistor R6 to form a SYNC _ N signal and a SYNC _ P signal, which are used as synchronization signals to synchronize PPG driving and wire coil resonance. Meanwhile, one end of the wire coil is connected with a collector (C pole) of the IGBT, the voltage of the C pole is the back voltage V _ IGBT _ C, the SYNC _ P signal formed after the back voltage V _ IGBT _ C is divided by the resistor R4 and the resistor R6 is also a back voltage acquisition signal, and the signal is sent to negative phase input ends of a comparator COMP1, a comparator COMP2 and a comparator COMP3 in the MCU control chip to form three-level back voltage protection.

In one embodiment, referring to fig. 5, the IGBT driving circuit includes a transistor Q2, a transistor Q3, a transistor Q4, a diode D1, a resistor R7, a resistor R8, a resistor R9, a capacitor C7, and an electrolytic capacitor EC1, wherein a second terminal of the resistor R2 is connected to an anode of the diode D1, an emitter of the transistor Q2, and an emitter of the transistor Q3, respectively, a cathode of the diode D3, a first terminal of the resistor R3, a positive terminal of the electrolytic capacitor EC 3 are connected to the 18V power supply, a second terminal of the resistor R3 is connected to a collector of the transistor Q3, a base of the transistor Q3 is connected to a second terminal of the resistor R3, a base of the transistor Q3, a collector of the transistor Q3, and a base of the emitter of the, The second end of the capacitor C7 and the negative electrode of the electrolytic capacitor EC1 are both grounded.

In this embodiment, a PPG signal from the PPG generator is inverted by the transistor Q4, and then is followed by the emitter of the transistor Q2 and the emitter of the transistor Q3 to drive the IGBT to operate.

In one embodiment, referring to fig. 6, the surge signal collecting circuit includes a diode D2, a diode D3, a resistor R10, a resistor R11, a resistor R12, a capacitor C8, and a capacitor C9, an anode of the diode D2 is connected to the first output terminal of the common mode inductor T1, an anode of the diode D3 is connected to the second output terminal of the common mode inductor T1, a cathode of the diode D2, a cathode of the diode D3, and a first end of the resistor R10 are connected to a first end of the capacitor C8, a first end of the resistor R11 is connected to the second end of the resistor R10 and the second end of the capacitor C8, a second end of the resistor R11 is connected to the first end of the resistor R12, the first end of the capacitor C9, and the input terminal of the surge protection circuit, and a second end of the resistor R12 is connected to the second end of the capacitor C9.

In the embodiment, a live wire (L) and a zero wire (N) are rectified by a diode D2 and a diode D3, and are subjected to voltage division by a resistor R10, a resistor R11 and a resistor R12 to form a SURGE acquisition signal V _ SURGE which is sent to a SURGE protection circuit in an MCU control chip, wherein a capacitor C8 is used for passing high frequency and low frequency and allowing SURGE signals to pass, and a capacitor C9 is used for filtering.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. A three-stage back pressure protection circuit of a chip special for an induction cooker is characterized by comprising a rectifying filter circuit, a wire coil resonance and driving circuit, an IGBT driving circuit, a synchronous circuit, a surge signal acquisition circuit and an MCU control chip, wherein the synchronous circuit comprises the back pressure acquisition circuit, and the MCU control chip comprises a CPU, a comparator COMP1, a comparator COMP2, a comparator COMP3, a PPG control circuit and a surge protection circuit;

2. The three-stage back-pressure protection circuit of the chip special for the induction cooker according to claim 1, wherein the PPG control circuit comprises a PPG generator, a PPG stop circuit, a PPG large reduction circuit and a PPG small reduction circuit, a first input end of the PPG generator is respectively connected with an output end of the PPG stop circuit, an output end of the PPG large reduction circuit and an output end of the PPG small reduction circuit, and an output end of the PPG generator is connected with a second input end of the wire coil resonance and driving circuit through the IGBT driving circuit;

3. The three-stage back-voltage protection circuit of the chip special for the induction cooker according to claim 2, wherein the rectification filter circuit comprises an X capacitor C1, an X capacitor C2, a common-mode inductor T1, a choke L2 and a rectification bridge stack BG1, a first end of the X capacitor C1 and a first input end of the common-mode inductor T1 are both connected to the live wire, a first output end of the common-mode inductor T1 is respectively connected to a first end of the X capacitor C2 and a first ac input end of the rectification bridge stack BG1, a positive electrode of a dc output end of the rectification bridge stack BG1 is connected to a first end of the choke L2, a second end of the X capacitor C1 and a second input end of the common-mode inductor T1 are both connected to the neutral wire, a second output end of the common-mode inductor T1 is respectively connected to a second end of the X capacitor C2 and a second ac input end of the rectification bridge stack BG1, and a negative electrode of the rectification bridge stack BG1 is grounded.

4. The three-stage back-pressure protection circuit of the chip dedicated for the induction cooker according to claim 3, wherein the coil resonance and driving circuit comprises a capacitor C3, a capacitor C4, a resistor R1, a resistor R2 and an IGBT tube Q1, wherein a second end of the choke L2 is respectively connected with a first end of the capacitor C3, a first end of the capacitor C4 and a first end of the coil of the induction cooker, a second end of the capacitor C3 is grounded, a second end of the coil of the induction cooker is respectively connected with a second end of the capacitor C4 and a collector of the IGBT tube Q1, a gate of the IGBT tube Q1 is respectively connected with a first end of the resistor R1 and a first end of the resistor R2, and a second end of the resistor R1 is grounded with an emitter of the IGBT tube Q1.

5. The three-level back-voltage protection circuit of the chip dedicated for the induction cooker according to claim 4, wherein the synchronization circuit comprises a resistor R3, a resistor R4, a resistor R5, a resistor R6, a capacitor C5 and a capacitor C6, a first end of the resistor R3 is connected to a first end of the coil of the induction cooker, and a second end of the resistor R3 is respectively connected to a first end of the resistor R5, a first end of the capacitor C5, a first end of the capacitor C6 and a third input end of the PPG generator; a first end of the resistor R4 is connected to a second end of the coil of the induction cooker, a second end of the resistor R4 is connected to a first end of the resistor R6, a second end of the capacitor C5, a negative phase input end of the comparator COMP1, a negative phase input end of the comparator COMP2, a negative phase input end of the comparator COMP3, and a third input end of the PPG generator, and a second end of the resistor R5, a second end of the resistor R6, and a second end of the capacitor C6 are all grounded.

6. The three-level back voltage protection circuit of the chip dedicated for the induction cooker according to claim 5, wherein the IGBT driving circuit comprises a transistor Q2, a transistor Q3, a transistor Q4, a diode D1, a resistor R7, a resistor R8, a resistor R9, a capacitor C7 and an electrolytic capacitor EC1, the second terminal of the resistor R2 is respectively connected to the anode of the diode D1, the emitter of the transistor Q2 and the emitter of the transistor Q3, the cathode of the diode D1, the first terminal of the resistor R7, the first terminal of the resistor R8, the first terminal of the resistor R9, the first terminal of the capacitor C7 and the anode of the electrolytic capacitor EC1 are all connected to an 18V power supply, the second terminal of the resistor R7 is connected to the collector of the transistor Q2, the base of the transistor Q2 is respectively connected to the second terminal of the resistor R8, the base of the transistor Q3 and the collector of the transistor Q4, the base electrode of the triode Q4 is respectively connected with the second end of the resistor R9 and the output end of the PPG generator, and the collector electrode of the triode Q3, the emitter electrode of the triode Q4, the second end of the capacitor C7 and the cathode of the electrolytic capacitor EC1 are all grounded.

7. The three-level back-voltage protection circuit of the chip specially used for the induction cooker according to claim 6, the surge signal acquisition circuit comprises a diode D2, a diode D3, a resistor R10, a resistor R11, a resistor R12, a capacitor C8 and a capacitor C9, the anode of the diode D2 is connected to the first output terminal of the common mode inductor T1, the anode of the diode D3 is connected to the second output terminal of the common mode inductor T1, a cathode of the diode D2, a cathode of the diode D3, a first terminal of the resistor R10 and a first terminal of the capacitor C8 are connected in common, a first end of the resistor R11 is respectively connected with a second end of the resistor R10 and a second end of the capacitor C8, a second end of the resistor R11 is connected to the first end of the resistor R12, the first end of the capacitor C9, and the input end of the surge protection circuit, respectively, and a second end of the resistor R12 and the second end of the capacitor C9 are grounded.