A plug discharge control circuit for IH electric hot pot

Abstract

This utility model discloses a plug discharge control circuit for an IH electric hot pot. The control circuit includes: a mains power detection circuit configured to monitor the AC power zero-crossing point in real time and output a detection signal; a main control chip connected to the mains power detection module, used to receive the zero-crossing signal and generate a fan drive command; and a fan execution circuit that responds to the drive command and converts the electrical energy in the safety capacitor CX1 at the power input terminal into mechanical energy for dissipation. This control circuit eliminates the risk of arcing through zero-crossing discharge: the timing error of accurately capturing the AC zero-crossing point by the mains power detection circuit is <±100μs, triggering fan discharge only at the voltage zero point, completely avoiding the arcing probability caused by non-zero-crossing conduction, reducing it to 0.01%, meeting the safety requirements of GB 15092.1 for plug disconnection, achieving a breakthrough in safety performance. Furthermore, the energy conversion efficiency between the capacitor and the fan reaches 82%, significantly improving energy utilization compared to the heat dissipation scheme of the discharge resistor.

Description

Technical Field

[0001] This utility model relates to the field of IH electric hot pot technology, and in particular to a plug discharge control circuit for IH electric hot pot. Background Technology

[0002] In the design of IH electric hot pots, to effectively suppress electromagnetic interference (EMI), a large-capacity safety capacitor (such as a 10μF / 275AC polypropylene capacitor) is typically connected in parallel at the power input to form an EMC filter circuit. These capacitors have the advantages of excellent high-frequency characteristics and low loss. However, their large capacity also brings significant problems: when the device is powered off, the charge stored in the capacitor releases slowly, resulting in high voltage residue on the power plug.

[0003] According to electrical safety standards (such as IEC 60335-1), the residual voltage between the two poles of the power plug must drop below 34V within one second after the equipment is powered off (i.e., the plug discharge test requirement). Existing solutions to this capacitor residual voltage problem mainly have the following drawbacks.

[0004] Defect 1: Passive discharge resistor scheme: A power resistor is connected in parallel across the safety capacitor for continuous discharge (e.g., Figure 1 (As shown in the dashed box). Although this solution has a simple structure, the resistor continuously consumes energy during the device's standby or operation, causing the overall standby power consumption to significantly exceed the standard (usually greater than 0.5W), violating increasingly stringent energy efficiency regulations (such as the ErP Directive).

[0005] Defect 2: Dedicated Discharge Chip Solution: This solution uses an additional dedicated integrated circuit (IC) to control the discharge switching circuit, which consists of transistors (such as BJTs or MOSFETs). While this solution can effectively reduce standby power consumption (discharging only when needed), it significantly increases material costs and the footprint of the printed circuit board (PCB), contradicting the current design trend of miniaturization and high integration in home appliances.

[0006] Thirdly, the limitations of existing intelligent discharge technology: Some designs attempt to reuse the original cooling fan motor windings as a discharge path. However, if the fan is started directly without precise control (especially when the AC current is not at a zero-crossing point), the fan motor windings may be at risk of high-voltage breakdown due to the residual high voltage of the capacitor (the peak voltage at the moment of power failure can exceed 300V). More seriously, this disordered timing of conduction can easily cause arcing when the plug is unplugged, posing a safety hazard and failing to meet the safety requirements for plug disconnection in standards such as GB 15092.1.

[0007] In summary, the core challenge facing the IH electric hot pot industry in addressing the discharge issue of large-capacity safety capacitor plugs lies in how to achieve plug discharge control that meets residual voltage requirements while eliminating arcing risks and achieving low standby power consumption, without adding extra hardware or increasing material costs. Current technologies have not yet effectively resolved this challenge. Summary of the Invention

[0008] This invention aims to solve at least one of the technical problems existing in the prior art. Therefore, one objective of this invention is to provide a plug discharge control circuit for IH electric hot pots, which, through a zero-hardware, low-cost plug discharge control scheme and a zero-crossing detection-coordinated fan multiplexing mechanism, completely eliminates additional energy consumption while meeting safety discharge standards.

[0009] This utility model also provides a plug discharge control circuit for an IH electric hot pot, comprising the following components.

[0010] The AC power detection circuit is configured to monitor the zero-crossing point of the AC power supply in real time and output a detection signal.

[0011] The main control chip, connected to the mains power detection module, is used to receive zero-crossing signals and generate fan drive commands.

[0012] The fan execution circuit, in response to the drive command, converts the electrical energy in the safety capacitor CX1 at the power input terminal into mechanical energy for dissipation.

[0013] Specifically, the mains power detection circuit includes a first diode D1, a second diode D2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a 5V terminal, a first capacitor C1, and an ACVOL terminal. The cathodes of the first diode D1 and the second diode D2 are connected together. The common terminal of the cathodes of the first diode D1 and the second diode D2 is sequentially connected to the third resistor R3, the fourth resistor R4, and the fifth resistor R5. The ACVOL terminal is connected to the common terminal of the fourth resistor R4 and the fifth resistor R5. The third diode D3 is connected to the 5V terminal. The ACVOL terminal is also connected to one end of the first capacitor C1. The other end of the first capacitor C1 is connected to the other end of the fifth resistor R5. The ACVOL terminal is connected to pin 11 of the main control chip.

[0014] Specifically, pin 1 of the main control chip is connected to a seventh resistor R7, an eighth resistor R8, a second capacitor C2, and a third capacitor C3. The other ends of the seventh resistor R7 and the eighth resistor R8 are connected to an 18V terminal, and the other ends of the second capacitor C2 and the third capacitor C3 are connected to a ground terminal GND.

[0015] Specifically, the main control chip has a first electrolytic capacitor EC1 and a fourth capacitor C4 connected in parallel between pins 2 and 3, a second electrolytic capacitor EC2 and a fifth capacitor C5 connected in parallel between pins 3 and 4, a ground terminal GND connected to pin 3, and a 5V terminal connected to pin 4.

[0016] Specifically, the fan execution circuit includes a fan connector FAN, a fourth diode D4, an 18V terminal, a first transistor Q1, a sixth resistor R6, and a FAN terminal. The first transistor Q1 and the FAN terminal are connected through the sixth resistor R6. The collector of the first transistor Q1 is connected to the anode of the fourth diode D4, and the cathode of the fourth diode D4 is connected to the 18V terminal. The fan connector FAN is connected in parallel with the fourth diode D4, and the FAN terminal is connected to pin 7 of the main control chip.

[0017] This utility model achieves significant improvement through the above technical means, and the specific beneficial effects are as follows.

[0018] I. Zero-crossing discharge eliminates arcing risk: The AC zero-crossing point is accurately captured by the mains power detection circuit (timing error < ±100μs), and the fan discharge is triggered only at the zero voltage point, completely avoiding the arcing caused by non-zero-crossing conduction (the measured arcing probability is reduced to 0.01%), meeting the safety requirements of GB 15092.1 for plug disconnection, and achieving a breakthrough advantage in safety performance.

[0019] II. Residual voltage compliance: Under an initial voltage of 311V, the 10μF capacitor, after being discharged through the fan winding (equivalent resistance 8Ω), drops to below 28V within 0.8 seconds, which is better than the 34V / 1s limit specified in IEC 60335.

[0020] III. Cost and Space Optimization: Cost savings stem from reusing the mains power detection circuit and fan, eliminating the need for any additional hardware.

[0021] IV. Zero standby power consumption: The circuit is completely dormant before discharge, with no continuous current path from the traditional discharge resistor, reducing standby power consumption to 0W, which meets the requirements of ERP Lot 6.

[0022] V. High-efficiency energy conversion: It can improve the mechanical energy conversion efficiency of the fan and significantly improve energy utilization compared with the heat dissipation scheme of the discharge resistor.

[0023] VI. Fan life guarantee: Zero-crossing triggering avoids high-voltage breakdown of the windings, significantly reducing the fan failure rate. Attached Figure Description

[0024] The above and / or additional aspects and advantages of this invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings.

[0025] Figure 1This is the mains power detection circuit diagram of the present invention.

[0026] Figure 2 This is a circuit diagram of the fan actuator of the present invention.

[0027] Figure 3 This is a circuit diagram of the main control chip of this invention. Detailed Implementation

[0028] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0029] The following is for reference. Figures 1 to 3 The present invention describes a plug discharge control circuit for an IH electric hot pot according to an embodiment of the present invention, comprising the following components.

[0030] The AC power detection circuit is configured to monitor the zero-crossing point of the AC power supply in real time and output a detection signal.

[0031] The main control chip, connected to the mains power detection module, is used to receive zero-crossing signals and generate fan drive commands.

[0032] The fan execution circuit, in response to the drive command, converts the electrical energy in the safety capacitor CX1 at the power input terminal into mechanical energy for dissipation.

[0033] Specifically, the mains power detection circuit includes a first diode D1, a second diode D2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a 5V terminal, a first capacitor C1, and an ACVOL terminal. The cathodes of the first diode D1 and the second diode D2 are connected together. The common terminal of the cathodes of the first diode D1 and the second diode D2 is sequentially connected to the third resistor R3, the fourth resistor R4, and the fifth resistor R5. The ACVOL terminal is connected to the common terminal of the fourth resistor R4 and the fifth resistor R5. The third diode D3 is connected to the 5V terminal. The ACVOL terminal is also connected to one end of the first capacitor C1. The other end of the first capacitor C1 is connected to the other end of the fifth resistor R5. The ACVOL terminal is connected to pin 11 of the main control chip. Pin 1 of the main control chip is connected to a seventh resistor R7, an eighth resistor R8, a second capacitor C2, and a third capacitor C3. The common terminal of the other ends of the seventh resistor R7 and the eighth resistor R8 is connected to an 18V terminal. The common terminal of the other ends of the second capacitor C2 and the third capacitor C3 is connected to a ground terminal GND. Pins 2 and 3 of the main control chip are connected in parallel to a first electrolytic capacitor EC1 and a fourth capacitor C4. Pins 3 and 4 of the main control chip are connected in parallel to a second electrolytic capacitor EC2 and a fifth capacitor C5. Pin 3 of the main control chip is also connected to a ground terminal. The fan execution circuit, which is connected to pin 4 of the main control chip via GND and a 5V terminal, includes a fan connector FAN, a fourth diode D4, an 18V terminal, a first transistor Q1, a sixth resistor R6, and the FAN terminal. The first transistor Q1 and the FAN terminal are connected through the sixth resistor R6. The collector of the first transistor Q1 is connected to the anode of the fourth diode D4, and the cathode of the fourth diode D4 is connected to the 18V terminal. The fan connector FAN is connected in parallel with the fourth diode D4, and the FAN terminal is connected to pin 7 of the main control chip.

[0034] Example: The working principle of the control circuit is described in detail below.

[0035] I. Mains power detection circuit workflow: Signal input path: AC power supply (ACL, ACN) is connected to DC transformer BG1.

[0036] II. Voltage Divider and Waveform Shaping: The pulsating DC voltage rectified by the first diode D1 and the second diode D2 is divided by the voltage divider network consisting of the third resistor R3, the fourth resistor R4, and the fifth resistor R5, generating a wavy voltage with attenuated amplitude at the ACVOL terminal.

[0037] 3. Zero-crossing signal extraction: The emitter of the third diode D3 is grounded, and the cathode is connected to the 5V terminal, forming a clamping circuit. When the voltage at the ACVOL terminal is lower than the breakdown voltage of the third diode D3, the third diode D3 is cut off, and the ACVOL terminal outputs a low level; when the ACVOL voltage exceeds the breakdown voltage of D3, the third diode D3 is turned on, clamping the voltage at the ACVOL terminal to the regulated value of the third diode D3 (e.g., 3.3V).

[0038] IV. Zero-crossing determination mechanism: The zero-crossing point of AC voltage corresponds to the lowest point of the steam wave voltage. At this time, the voltage at the ACVOL terminal is lower than the breakdown threshold of the third diode D3, and a low-level pulse signal is output. The falling edge of this pulse represents the zero-crossing point of the mains voltage.

[0039] V. Filtering and anti-interference: The first capacitor C1 is connected in parallel between the ACVOL terminal and ground to filter out high-frequency noise and ensure the stability of the zero-crossing signal.

[0040] VI. Main Control Chip Cooperative Control Logic: Zero-Crossing Signal Response: The ACVOL terminal is connected to pin 11 of the main control chip (interrupt input pin). When the chip detects the falling edge of a low-level pulse at pin 11, it determines that the mains power has reached the zero-crossing point.

[0041] VII. Discharge Trigger Conditions: When a plug removal event is detected (via hardware switch or current detection), the chip enters the discharge standby state;

[0042] 8. Strict synchronization mechanism: The main control chip only outputs a high-level drive signal from pin 7 (FAN terminal) after receiving a zero-crossing signal.

[0043] IX. Power Management Design: Pin 1 of the main control chip is connected to the 18V terminal to provide a stable operating voltage. The 18V is connected to the RC circuit consisting of the seventh resistor R7, the eighth resistor R8, the second filter capacitor C2, and the second filter capacitor C3 to implement current limiting and filtering functions. In addition, the first electrolytic capacitor EC1 / fourth capacitor C4, the second electrolytic capacitor EC2 / fifth capacitor C5 are connected in parallel to the pins 3 (GND) and 4 (5V terminal) of the main control chip to form a local decoupling network to suppress power supply disturbances.

[0044] 10. The physical process of the fan actuator circuit discharge is as follows: Drive stage: The main control chip outputs a high level at pin 7. The high level is limited by the sixth resistor R6, which drives the first transistor Q1 to conduct, and the fan connector FAN is energized to start the fan motor.

[0045] The first transistor Q1 conducts only at the zero-crossing point of the mains power. At this time, the voltage across the safety capacitor CX1 approaches 0V, preventing the fan windings from being subjected to high voltage breakdown and providing zero-crossing safety. During this process, the fan motor's rotation dissipates electrical energy as heat through the winding resistance, simultaneously converting it into rotor kinetic energy (mechanical energy). The fourth diode D4 is connected across the fan, forming a freewheeling circuit to absorb the back electromotive force when the power supply is turned off.

[0046] The plug discharge control circuit for IH electric hot pot described in this utility model includes the following control method: the control method comprises the following steps.

[0047] Step a: Use the mains power detection circuit to detect the zero-crossing point of the AC power supply in real time.

[0048] Step b: When performing a plug discharge test, the main control chip is triggered by the zero-crossing detection signal.

[0049] Step c: The main control chip controls the fan to start, and the electrical energy stored in the safety capacitor CX1 at the power input terminal is discharged and consumed by the fan.

[0050] Specifically, the zero-crossing detection involves capturing the zero-crossing moment of the AC voltage waveform through a mains power detection circuit and generating a synchronization pulse signal that is transmitted to the main control chip. The fan start logic is as follows: after detecting a plug unplugging event, the fan is activated only when the mains power zero-crossing signal arrives, until the capacitor voltage drops to a safe threshold. The safety capacitor CX1 has parameters of 10μF / 275AC and is connected in parallel to the power input for EMC filtering.

[0051] The control method workflow is detailed below.

[0052] Step a: The mains power detection circuit monitors the AC voltage waveform in real time and generates a wavy signal through rectification and voltage division.

[0053] By utilizing the clamping effect of the third diode D3 and the filtering of the first capacitor C1, the valley point (i.e., the zero-crossing point) of the steam wave voltage is extracted, and a low-level synchronization pulse is generated.

[0054] Step b: The plug removal event is transmitted to the main control chip through auxiliary circuitry (such as a plug detection switch).

[0055] The chip locks the discharge command, but does not start the fan yet, waiting for the zero-crossing signal to arrive.

[0056] Step c: When the zero-crossing signal (falling edge) reaches pin 11 of the chip, the main control chip immediately outputs a high level from pin 7; the first transistor Q1 is turned on, forming a discharge circuit of safety capacitor CX1, fan and the first transistor Q1; discharge termination condition: the main control chip continuously monitors the mains voltage, and shuts off the output of pin 7 when the voltage drops to the safety threshold of 34V.

[0057] Although embodiments of the present invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A plug discharge control circuit for an IH electric hot pot, characterized in that, include: The AC power detection circuit is configured to monitor the zero-crossing point of the AC power supply in real time and output a detection signal. The main control chip, connected to the mains power detection module, is used to receive zero-crossing signals and generate fan drive commands; The fan execution circuit, in response to the drive command, converts the electrical energy in the safety capacitor CX1 at the power input terminal into mechanical energy for dissipation.

2. The plug discharge control circuit for an IH electric hot pot according to claim 1, characterized in that, The mains power detection circuit includes a first diode D1, a second diode D2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a 5V terminal, a first capacitor C1, and an ACVOL terminal. The cathodes of the first diode D1 and the second diode D2 are connected together. The common terminal of the cathodes of the first diode D1 and the second diode D2 is connected in sequence to the third resistor R3, the fourth resistor R4, and the fifth resistor R5. The ACVOL terminal is connected to the common terminal of the fourth resistor R4 and the fifth resistor R5. The third diode D3 is connected to the 5V terminal. The ACVOL terminal is also connected to one end of the first capacitor C1. The other end of the first capacitor C1 is connected to the other end of the fifth resistor R5. The ACVOL terminal is connected to pin 11 of the main control chip.

3. The plug discharge control circuit for an IH electric hot pot according to claim 1, characterized in that, Pin 1 of the main control chip is connected to a seventh resistor R7, an eighth resistor R8, a second capacitor C2, and a third capacitor C3. The other ends of the seventh resistor R7 and the eighth resistor R8 are connected to an 18V terminal, and the other ends of the second capacitor C2 and the third capacitor C3 are connected to a ground terminal GND.

4. The plug discharge control circuit for an IH electric hot pot according to claim 1, characterized in that, The main control chip has a first electrolytic capacitor EC1 and a fourth capacitor C4 connected in parallel between pins 2 and 3. The main control chip has a second electrolytic capacitor EC2 and a fifth capacitor C5 connected in parallel between pins 3 and 4. The main control chip also has a ground terminal GND connected to pin 3 and a 5V terminal connected to pin 4.

5. A plug discharge control circuit for an IH electric hot pot according to claim 1, characterized in that, The fan execution circuit includes a fan connector FAN, a fourth diode D4, an 18V terminal, a first transistor Q1, a sixth resistor R6, and a FAN terminal. The first transistor Q1 and the FAN terminal are connected through the sixth resistor R6. The collector of the first transistor Q1 is connected to the anode of the fourth diode D4, and the cathode of the fourth diode D4 is connected to the 18V terminal. The fan connector FAN is connected in parallel with the fourth diode D4, and the FAN terminal is connected to pin 7 of the main control chip.

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