PFC (Power Factor Correction) circuit suitable for electrode high-voltage discharge

Abstract

The invention discloses a PFC (Power Factor Correction) circuit suitable for electrode high-voltage discharge. The PFC circuit comprises an EMI (Electro-Magnetic Interference) filtering module, a starting protection module, a PFC power conversion module and a PWM (Pulse-Width Modulation) switch type auxiliary power supply module which are connected in sequence. The EMI filtering module realizes bidirectional suppression of interference, and when the circuit is powered off, the bleeder resistor enables the common mode inductor and the differential mode capacitor to rapidly discharge, so that secondary interference is prevented; according to the PWM switch type auxiliary power supply module, a high-voltage area and a low-voltage area are isolated, and it is guaranteed that the power supply input pin of the control chip U2 / U3 can be within the normal working voltage; according to the invention, the control chip U2 limits the PWM duty ratio of the control chip U3 through the control logic, so that overcurrent protection is realized; when the MOS tube Q1 / Q2 is conducted, the resistor R22 consumes energy generated by discharging of the capacitor C21, meanwhile, resonance between the capacitor C21 and the energy storage inductor L2 is restrained, high-frequency electromagnetic interference is prevented, and electromagnetic compatibility of the whole system is achieved.

Description

Technical Field

[0001] This invention specifically relates to an electric flame stove. Background Technology

[0002] An electric flame stove is a novel flame-generating method. It uses two different electrodes to generate an electric field by high-voltage breakdown of the gas flow. The gas flow collides with electrons in the electric field, ionizing the gas molecules and forming plasma. This plasma has a temperature of over 1,000 degrees Celsius and is used to heat cookware. Currently, electric flame stoves on the market are also known as electric fire stoves, electric fire starter stoves, electric flame stoves, electric combustion stoves, electric open flame stoves, plasma stoves, etc. All of these stoves use the working principle of two electrodes discharging and high-voltage breakdown of the gas flow to generate plasma for heating cookware.

[0003] During electrode discharge, the load switches frequently between gas (high resistance) and plasma (low resistance), generating a large number of electromagnetic waves. This causes drastic fluctuations in discharge current / voltage, and high voltage can easily enter the control terminal, causing the control chip to burn out. In addition, high voltage discharge is prone to "overvoltage and overcurrent". If protection is not provided in time, it can lead to the burnout of components such as MOSFETs, capacitors, and diodes. At the same time, electromagnetic interference with sampling and control signals can cause the protection logic to be falsely triggered (such as falsely judging overcurrent and shutting down the output). Summary of the Invention

[0004] To overcome the shortcomings mentioned above, the present invention aims to provide a technical solution that can solve the above problems.

[0005] A PFC circuit suitable for high-voltage discharge of electrodes, used in an electric flame stove, includes: an EMI filter module, a start-up protection module, and a PFC power conversion module connected in sequence. The PFC power conversion module includes a rectifier D8, an energy storage inductor L2, a freewheeling diode D11, MOSFETs Q1 / Q2, control chips U2 / U3, and an energy storage capacitor C22. The second end of the energy storage inductor L2 is connected to the drain of MOSFETs Q1 and Q2. One output pin of the control chip U2 is connected to one input pin of the control chip U3 through a resistor R10. The PWM pin of the control chip U3 is connected to the gate of MOSFETs Q1 and Q22. The two ends of the energy storage inductor L2 are connected to the first end of the energy storage capacitor C22 through diodes D11 and D13, respectively. Preferably, the EMI filtering module includes differential mode capacitors C1 / C2, bleeder resistors R1 / R2 / R4 / R5, and common mode inductor L1. The output and input terminals of the common mode inductor L1 are connected in parallel to the differential mode capacitors C1 and C2, respectively. The two ends of the differential mode capacitor C1 are also connected to the ground through common mode capacitors C3 / C4, and the two ends of the differential mode capacitor C2 are also connected to the ground through common mode capacitors C5 / C6. Preferably, the start-up protection module includes a relay PLY1 and a freewheeling auxiliary resistor R6, wherein the relay PLY1 and the freewheeling auxiliary resistor R6 are connected in parallel. Preferably, the first common node between one output terminal of the EMI filter module and the input terminal of the startup protection module is connected to the first terminal of the PWM switching auxiliary power supply module, and the second terminal of the PWM switching auxiliary power supply module is connected to the other output terminal of the EMI filter module through the power control terminal CN3; Preferably, the PWM switching auxiliary power supply module includes a control chip U4, an optocoupler U5, and field-effect transistors Q11 / Q12; the RT pin of the control chip U4 is connected to the collector of the optocoupler U5 through potentiometer RV2 and resistor R55, and the LED side of the optocoupler U5 is connected to the KEYB and KEYA terminals of connector CN4. Preferably, the sources of the field-effect transistors Q11 / Q12 are both grounded, and their drains are respectively connected to the OUTA and OUTB terminals of connector CN4. The gates of the field-effect transistors Q11 / Q12 are respectively connected to the OUTPUTA and OUTPUTB pins of control chip U4. Preferably, the CT / DISCHARGE / SOFT-START pins of the control chip U4 are connected to resistor R56, capacitor C56 and soft-start capacitor C57 respectively, and the other ends of resistor R56, capacitor C56 and soft-start capacitor C57 are grounded. Preferably, the common cathode node of diode D11 and diode D13 is connected to the detection pin of control chip U2 through detection resistors R23 / R24 / R25, and the common node of the detection pin of control chip U2 and the drive resistor is connected to capacitor C20 and resistor R20 respectively. Preferably, the diode D13, resistor R22, and capacitor C21 form an absorption circuit.

[0006] Compared with the prior art, the advantages of the present invention are: The EMI filtering module of this invention achieves bidirectional interference suppression. When the circuit is powered off, the discharge resistors R1 / R2 / R4 / R5 cause the common-mode inductor and differential-mode capacitor to discharge rapidly, preventing secondary interference. The startup protection module of this invention prevents the impact of surge current during startup and allows the circuit to enter a low-loss normal operating state when the voltage is stable, thereby protecting the circuit. The PWM switching auxiliary power supply module of the present invention isolates the high voltage area from the low voltage area, ensuring that the power input pins of the control chips U2 / U3 are within the normal operating voltage range; In this invention, the detection resistors R23 / R24 / R25 are connected in series between the DC bus and the detection pin of the control chip U2. The control chip U2 limits the PWM duty cycle of the control chip U3 through control logic to achieve overcurrent protection. In this invention, diode D13, resistor R22, and capacitor C21 form an RCD absorption circuit. When MOSFET Q1 / Q2 is turned on, resistor R22 consumes the energy generated by capacitor C21 during discharge, while suppressing the resonance between capacitor C21 and energy storage inductor L2, avoiding secondary spikes, preventing high-frequency electromagnetic interference, and enabling the entire system to achieve electromagnetic compatibility.

[0007] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0008] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0009] Figure 1 This is a circuit schematic diagram of the EMI filtering module, startup protection module, and PFC power conversion module of the present invention.

[0010] Figure 2 This is a schematic diagram of the PWM switching auxiliary power supply module circuit of the present invention. Detailed Implementation

[0011] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0012] In the description of this invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0013] Furthermore, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components; they can refer to a wireless connection or a wired connection. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0014] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0015] Please see Figures 1-2 In this embodiment of the invention, a PFC power conversion module 300 suitable for high-voltage discharge of electrodes is used in an electric flame stove, comprising: an EMI filter module 100, a start-up protection module 200, and a PFC power conversion module 300 connected in sequence.

[0016] The EMI filter module 100 includes differential-mode capacitors C1 / C2, bleeder resistors R1 / R2 / R4 / R5, and a common-mode inductor L1. The output and input terminals of the common-mode inductor L1 are connected in parallel to the differential-mode capacitors C1 and C2, respectively. The two ends of the differential-mode capacitor C1 are also connected to ground through common-mode capacitors C3 / C4, and the two ends of the differential-mode capacitor C2 are also connected to ground through common-mode capacitors C5 / C6. The AC power input from the mains grid contains both common-mode and differential-mode interference, which can cause abnormal circuit operation and excessive electromagnetic radiation. The EMI filter module 100 achieves bidirectional interference suppression through the impedance matching and bypass characteristics of the differential-mode capacitors C1 / C2, C3 / C4, C5 / C6, and the common-mode inductor L1. When the circuit is powered off, the bleeder resistors R1 / R2 / R4 / R5 rapidly discharge the differential-mode capacitors, preventing secondary interference.

[0017] The start-up protection module 200 includes a relay PLY1 and a freewheeling auxiliary resistor R6, which are connected in parallel. During the start-up phase of the electric flame stove, relay PLY1 is not engaged. When AC current flows through the freewheeling auxiliary resistor R6, the surge current is limited. The current gradually decreases as the voltage rises. When the voltage rises to approximately 90% of the rated voltage, the auxiliary power supply output stabilizes, the relay coil is energized, the contacts close, and R6 is short-circuited. At this time, the circuit enters a low-loss normal operating state. R6 only operates during the start-up moment, and its lifespan is unaffected.

[0018] The first common node between one output terminal of the EMI filter module 100 and the input terminal of the startup protection module 200 is connected to the first terminal of the PWM switching auxiliary power supply module 400, and the second terminal of the PWM switching auxiliary power supply module 400 is connected to the other output terminal of the EMI filter module 100 through the power control terminal CN3.

[0019] The PWM switching auxiliary power supply module 400 includes a control chip U4, an optocoupler U5, and field-effect transistors Q11 / Q12. The RT pin of the control chip U4 is connected to the collector of the optocoupler U5 through potentiometers RV2 and R55. The LED side of the optocoupler U5 is connected to connector CN4. The sources of the field-effect transistors Q11 / Q12 are both grounded, and their drains are connected to the OUTA and OUTB terminals of connector CN4, respectively. The gates of the field-effect transistors Q11 / Q12 are connected to the OUTPUTA and OUTPUTB pins of the control chip U4, respectively.

[0020] The CT / DISCHARGE / SOFT-START pins of the control chip U4 are connected to resistor R56, capacitor C56, and capacitor C57 respectively, and the other ends of resistor R56, capacitor C56, and capacitor C57 are grounded respectively.

[0021] In this embodiment, the external control signal is completely isolated from the internal power circuit by the optocoupler U5, which prevents high voltage or high frequency interference from the PFC power conversion module 300 from entering the control terminal and ensures the safety of the control circuit. The internal oscillation frequency is adjusted by potentiometer RV2, or external commands (user manual adjustment signals) are received by connector CN4 to dynamically adjust the parameters of the output power supply (such as voltage and power) to adapt to different operating conditions. The soft-start circuit composed of resistor R56 and capacitors C56 / C57 avoids voltage surges at the moment of power-on.

[0022] Specifically, such as Figure 1 and Figure 2As shown, the PFC power conversion module 300 handles high voltage and high current, while its control chips U2 / U3 belong to low voltage and weak current systems. Therefore, the PWM switching auxiliary power supply module 400 constructs a "safety isolation barrier" through the optocoupler U5. In this embodiment, the PWM switching auxiliary power supply module 400 provides the operating voltage to the control chips U2 / U3 of the PFC power conversion module 300 through the VCC terminal, providing stable voltage and circuit protection for the control chips U2 / U3. More specifically, the LED side of the optocoupler U5 is connected to the control terminal through connector CN4, and the phototransistor side of the optocoupler U5 is connected to the control circuit of U4 (associated with the high voltage side of PFC). The two have no direct electrical connection, completely blocking the conduction of high voltage to low voltage side and preventing the power supply terminal of the control chips U2 / U3 from being damaged by high voltage breakdown.

[0023] Working process of PWM switching auxiliary power supply module 400: After the circuit is powered on, the AC power output by the EMI filter module is processed and used to power the PWM switching auxiliary power supply module. Potentiometer RV2 is at the user-preset initial position. No current flows through the LED side of optocoupler U5 (not conducting). At this time, the phototransistor side of U5 is in an open-circuit cutoff state. Capacitor C56 and resistor R56 work together to generate an initial frequency through the internal oscillator. Control chip U4 generates a PWM signal according to the initial frequency and drives the gates of field-effect transistors Q11 / Q12 through its OUTPUT pin. The alternating switching of MOSFETs Q11 / Q12 ensures a stable low voltage (12V) output at the OUT terminal of connector CN4, supplying power to the PFC control chips U2 / U3. When the user operates the electric flame stove to trigger the "ignition" mode, the external control circuit inputs a high-level signal to connector CN4. This signal drives the LED side of optocoupler U5 to conduct, and the phototransistor side of optocoupler U5 conducts after being illuminated, increasing the frequency of the PWM signal output by control chip U4. Under the high-frequency PWM signal, the switching speed of MOSFETs Q11 / Q12 increases, ensuring that the output 12V voltage remains stable under the instantaneous high current demand during PFC module ignition, preventing voltage drops. When the external control signal returns to a low level, the LED side of optocoupler U5 is cut off, the phototransistor side returns to a high-impedance open-circuit state, the oscillation frequency of control chip U4 decreases, and the auxiliary power supply output switches to "steady-state mode," achieving low switching losses and efficient power supply.

[0024] The PFC power conversion module 300 includes a rectifier D8, an energy storage inductor L2, a freewheeling diode D11, MOSFETs Q1 / Q2, control chips U2 / U3, and an energy storage capacitor C22.

[0025] The second terminal of the energy storage inductor L2 is connected to the drain of MOSFET Q1 and the drain of MOSFET Q2. The PWM pin of the control chip U3 is connected to the gate of MOSFET Q1 and the gate of MOSFET Q2.

[0026] The common node of the cathodes of diodes D11 and D13 is connected to the detection pin of control chip U2 through sensing resistors R23 / R24 / R25. The sensing resistors R23 / R24 / R25 are connected in series between the DC bus and ground, converting the output current into a voltage signal, which is input to the detection pin of control chip U2. If the current exceeds the rated value, control chip U2 will limit the PWM duty cycle of control chip U3 through control logic to achieve overcurrent protection. The common node of the detection pin of control chip U2 and the drive resistor is connected to capacitor C20 and resistor R20 respectively. Capacitor C20 and resistor R20 form an RC filter and phase compensation network to filter out high-frequency noise in the current signal, while ensuring the phase margin of the current loop and preventing the control loop from oscillating due to insufficient phase margin.

[0027] One of the output pins of control chip U2 is connected to one of the input pins of control chip U3 through resistor R10. Control chip U2 amplifies and conditions the sampled signal and then transmits it to control chip U3 through resistor R10. The PWM generator integrated inside control chip U3 generates a high-frequency PWM signal based on the signal conditioning result. The PWM pin of control chip U3 outputs a synchronization signal, which makes MOSFETs Q1 / Q2 turn on / off simultaneously. The parallel switching transistors share the large current, improving the power carrying capacity of the circuit.

[0028] By accurately sampling the input current through U2, the control chip U3 dynamically adjusts the PWM duty cycle to make the input current waveform track the voltage waveform (sine wave), thereby making the input current and voltage in phase, ultimately achieving a power factor close to "1" and significantly improving the energy utilization efficiency.

[0029] The two ends of the energy storage inductor L2 are connected to the first end of the energy storage capacitor C22 through diodes D11 and D13, respectively.

[0030] When MOSFETs Q1 / Q2 are turned off, the current in the energy storage inductor L2 cannot be interrupted instantaneously, resulting in a reverse induced electromotive force (polarity reversed, second terminal positive) due to the "magnetic inertia sudden change". This electromotive force, superimposed on the DC bus voltage, easily forms an ultra-high voltage spike between the drain and source of Q1 / Q2 (potentially far exceeding the MOSFET's withstand voltage). In this embodiment of the invention, as... Figure 2As shown, diode D13, resistor R22, and capacitor C21 form an RCD snubber circuit. When MOSFETs Q1 / Q2 are off, diode D13 is forward biased and conducts, charging capacitor C21 with energy from the energy storage inductor L2, temporarily storing the spike energy in C21. When MOSFETs Q1 / Q2 are on, resistor R22 consumes the energy generated by the discharge of C21, while simultaneously suppressing the resonance between capacitor C21 and energy storage inductor L2, thus avoiding secondary spikes. Voltage spikes are a significant source of high-frequency electromagnetic interference (spikes contain high-frequency harmonics), and the RCD snubber circuit significantly reduces the high-frequency noise radiated from the circuit to the power grid or surrounding equipment by suppressing spikes, making the entire system easier to pass electromagnetic compatibility (EMC) tests and preventing interference to other electrical appliances or the power grid.

[0031] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A PFC circuit suitable for high-voltage electrode discharge, used in an electric flame stove, characterized in that, include: The EMI filter module, startup protection module, and PFC power conversion module are connected in sequence. The PFC power conversion module includes an energy storage inductor L2, a freewheeling diode D11, MOSFETs Q1 / Q2, control chips U2 / U3, and an energy storage capacitor C22. The second end of the energy storage inductor L2 is connected to the drain of MOSFETs Q1 and Q2. One output pin of the control chip U2 is connected to one input pin of the control chip U3 through a resistor R10. The PWM pin of the control chip U3 is connected to the gate of MOSFETs Q1 and Q2. The two ends of the energy storage inductor L2 are connected to the first end of the energy storage capacitor C22 through diodes D11 and D13, respectively.

2. The PFC circuit suitable for high-voltage electrode discharge according to claim 1, characterized in that, The EMI filtering module includes differential mode capacitors C1 / C2, bleeder resistors R1 / R2 / R4 / R5, and common mode inductor L1. The output and input terminals of the common mode inductor L1 are connected in parallel to the differential mode capacitors C1 and C2, respectively. The two ends of the differential mode capacitor C1 are also connected to the ground through the common mode capacitors C3 / C4, and the two ends of the differential mode capacitor C2 are also connected to the ground through the common mode capacitors C5 / C6.

3. The PFC circuit suitable for high-voltage electrode discharge according to claim 2, characterized in that, The startup protection module includes a relay PLY1 and a freewheeling auxiliary resistor R6, which are connected in parallel.

4. The PFC circuit suitable for high-voltage electrode discharge according to claim 1, characterized in that, The first common node between one output terminal of the EMI filter module and the input terminal of the startup protection module is connected to the first terminal of the PWM switching auxiliary power supply module, and the second terminal of the PWM switching auxiliary power supply module is connected to the other output terminal of the EMI filter module through the power control terminal CN3.

5. The PFC circuit suitable for high-voltage electrode discharge according to claim 4, characterized in that, The PWM switching auxiliary power supply module includes a control chip U4, an optocoupler U5, and field-effect transistors Q11 / Q12. The RT pin of the control chip U4 is connected to the collector of the optocoupler U5 through potentiometer RV2 and resistor R55. The LED side of the optocoupler U5 is connected to the KEYB and KEYA terminals of connector CN4.

6. The PFC circuit suitable for high-voltage electrode discharge according to claim 5, characterized in that, The sources of the field-effect transistors Q11 and Q12 are both grounded, and their drains are connected to the OUTA and OUTB terminals of connector CN4, respectively. The gates of the field-effect transistors Q11 and Q12 are connected to the OUTPUTA and OUTPUTB pins of control chip U4, respectively.

7. The PFC circuit suitable for high-voltage electrode discharge according to claim 1, characterized in that, The CT / DISCHARGE / SOFT-START pins of the control chip U4 are connected to resistor R56, capacitor C56 and soft-start capacitor C57 respectively, and the other ends of resistor R56, capacitor C56 and soft-start capacitor C57 are grounded.

8. The PFC circuit suitable for high-voltage electrode discharge according to claim 1, characterized in that, The common node of the cathodes of diodes D11 and D13 is connected to the detection pin of the control chip U2 through detection resistors R23 / R24 / R25. The common node of the detection pin of the control chip U2 and the drive resistor is connected to capacitor C20 and resistor R20, respectively.

9. The PFC circuit suitable for high-voltage electrode discharge according to claim 1, characterized in that, The diode D13, resistor R22, and capacitor C21 form an absorption circuit.

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