Microwave oven power adjusting circuit and power adjusting method using same

Abstract

The invention particularly relates to a microwave oven power adjusting circuit and a power adjusting method applying the circuit, the circuit comprises a power supply circuit, a control chip U2 and an IGBT switch driving circuit, the power supply circuit supplies power to the power supply circuit and the control chip U2, the IGBT switch driving circuit is composed of an insulated gate bipolar transistor IGBT, a second connector CN2 and a unidirectional thyristor TR1, and the IGBT switch driving circuit is connected with the control chip U2. According to the circuit, the IGBT switch driving circuit is adjusted step by step, the input power of an external variable-frequency power supply is detected in real time, the actual input power is compared with the theoretical input power, the duty ratio of a PWM signal generated by a micro controller of the microwave oven is dynamically adjusted, and the working state of the microwave oven is accurately controlled; besides, parameters and algorithm parameters can be adjusted according to specific application scenes, the measurement performance is optimized, stable and efficient operation of the whole system is ensured, and therefore the power control level and the working performance of the microwave oven are effectively improved.

Description

Technical Field

[0001] The invention specifically relates to a microwave oven power adjustment circuit and a power adjustment method using the circuit. Background Art

[0002] Microwave ovens are important stoves in daily family life. Among them, the consistency of microwave power at various gears of microwave ovens has become an important indicator. Microwave ovens in related art include magnetrons, which are used to control the output power of microwaves. However, microwave oven controllers in related art microwave ovens have differences in mass production. It is difficult for mass-produced microwave ovens to achieve consistency in input power or output power of microwave oven devices of the same specifications and models, especially it is difficult to achieve consistency in microwave power at various gears. The inability to achieve consistency in important indicators such as input power and output power of the same specifications and models leads to the worst deviation, resulting in the appearance of low-power and high-power products, which reduces the quality of food cooking and causes poor quality of microwave ovens. Summary of the invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, one purpose of the present invention is to provide a microwave oven power adjustment circuit and a power adjustment method using the circuit, adjust parameters and algorithm parameters according to specific application scenarios, optimize measurement performance, and ensure stable and efficient operation of the entire system.

[0004] According to the present invention, a microwave oven power adjustment circuit includes a power supply circuit, a control chip U2 and an IGBT switch drive circuit. The power supply circuit supplies power to the control chip U2 and the IGBT switch drive circuit respectively. The IGBT switch drive circuit includes an insulated gate bipolar transistor IGBT, a second connector CN2, a unidirectional thyristor TR1, a PWM terminal, an AD terminal, an SCR terminal, an ACL terminal, a sixth resistor R6 and a ZERO terminal. The ACL terminal, the sixth resistor R6 and the ZERO terminal are connected in series. The 4th pin of the control chip U2 is connected to the G pole of the insulated gate bipolar transistor IGBT. The C pole of the transistor IGBT is connected to the 1st pin of the second connector CN2, the E pole of the gate bipolar transistor IGBT is connected to the AD terminal, the AD terminal is also connected to the 7th pin of the control chip U2, the 2nd pin of the second connector CN2 is connected to the unidirectional thyristor TR1, the G pole of the unidirectional thyristor TR1 is connected to the 8th pin of the control chip U2, the A pole of the unidirectional thyristor TR1 is connected to the VCC terminal, the control chip U2 is connected to the fire gear button group, the control chip U2 can receive the power detection signal of the IGBT switch drive circuit and issue a control instruction, and the IGBT switch drive circuit can adjust the power according to the instruction of the control chip.

[0005] Specifically, the A pole of the unidirectional thyristor TR1 is connected to the VCC terminal via a thirteenth resistor R13, and the G pole of the unidirectional thyristor TR1 is connected to the 8th pin of the control chip U2 via a second resistor R2.

[0006] Specifically, the C pole of the edge-gate bipolar transistor IGBT is connected to the 1st pin of the second connector CN2 via a first resistor R1.

[0007] Specifically, the G pole of the edge-gate bipolar transistor IGBT is connected to the PWM terminal via a third resistor R3.

[0008] Specifically, a seventh resistor R7 and an eighth resistor R8 are connected in series between the E terminal and the AD terminal of the edge-gate bipolar transistor IGBT.

[0009] Specifically, a common end between the seventh resistor R7 and the eighth resistor R8 is connected to a metal film resistor RJ1, a first capacitor C1 is also connected in parallel to the metal film resistor RJ1, and the other end of the metal film resistor RJ1 is connected to a ground end GND.

[0010] Specifically, the power supply circuit includes a step-down chip POWR1, a +12V terminal and a 5V-OUT terminal, and the 8th pin of the step-down chip POWR1 is connected to the +12V terminal.

[0011] Specifically, the power supply circuit includes a first plug CN1, a rectifier bridge DB1, a transformer T1, a first inductor L1, a second diode D2, a +5V terminal, a first photocoupler U1 and a regulating chip IC1. Pin 1 and pin 2 of the first plug CN1 are respectively connected to pin 2 and pin 3 of the rectifier bridge DB1, pin 1 of the rectifier bridge DB1 is connected to pin 1 of the transformer T1, pin 4 of the rectifier bridge DB1 is respectively connected to pin 1, pin 2, pin 7 and pin 8 of the regulating chip IC1, pin 3 and pin 4 of the regulating chip IC1 are respectively connected to pin 3 and pin 4 of the first photocoupler U1, pin 2 and pin 1 of the first photocoupler U1 are respectively connected to pin 5 and pin 4 of the transformer T1, and pin 4 of the transformer T1 is sequentially connected to the first inductor L1, the second diode D2 and the +5V terminal.

[0012] The present invention also discloses a power adjustment method for a microwave oven power adjustment circuit using any of the above schemes, comprising the following steps: step 1: initial power detection, setting the microwave oven's power level to level 1 through a power level button group, starting detection and adjustment at this level, and providing basic data and a stable starting state for subsequent adjustments to higher levels; connecting an external variable frequency power supply to power the microwave oven, utilizing the connection relationship between a control chip U2 and an insulated gate bipolar transistor IGBT in an IGBT switch drive circuit, detecting the input power of the external variable frequency power supply in real time, and generating a first input power value by the control chip U2; the external variable frequency power supply provides electrical energy to the microwave oven, and the magnitude of its input power directly affects the working state of the microwave oven; by detecting the input power in real time, the actual power consumption of the microwave oven at the current power level can be accurately obtained.

[0013] Step 2: Power comparison and duty cycle adjustment control chip U2 compares the first input power value with the theoretical input power value corresponding to power level 1 pre-stored in the microwave oven to obtain a first difference; the theoretical input power value is determined during the microwave oven design and testing phase, and represents the ideal power consumption of the microwave oven at power level 1. By comparing the actual input power with the theoretical input power, it can be determined whether the current working state of the microwave oven deviates from the ideal state.

[0014] If the first difference is a positive number, it means that the actual input power is greater than the theoretical input power, and the microwave oven may be in an overpower operation state; at this time, the control chip U2 reduces the first duty cycle of the PWM signal generated by the microwave oven's microcontroller according to a preset value based on the first difference; since the PWM end in the IGBT switch drive circuit works in conjunction with the control chip U2, reducing the duty cycle means reducing the average power of the signal, thereby reducing the actual input power of the microwave oven by adjusting the working state of the insulated gate bipolar transistor IGBT to make it close to the theoretical input power.

[0015] If the first difference is a non-positive number, it means that the actual input power is less than or equal to the theoretical input power, and the microwave oven may be in an under-power operation state; at this time, the control chip U2 increases the first duty cycle of the PWM signal generated by the microcontroller of the microwave oven according to a preset value based on the first difference, increases the average power of the signal, and increases the actual input power of the microwave oven by adjusting the working state of the insulated gate bipolar transistor IGBT to make it close to the theoretical input power; based on the adjusted first duty cycle, the control chip U2 generates first frequency adjustment information and stores it, and the frequency adjustment information records the duty cycle adjustment status under the current firepower level, providing a basis for subsequent control and analysis.

[0016] Step 3: Adjustment and repeated detection at each level. Increase the power level of the microwave oven by one level and set it to level 2 through the power level button group. As the power level increases, the working intensity of the microwave oven increases, and it is necessary to re-detect the input power and make corresponding adjustments. The same goes for each level, i.e., repeating steps 1 and 2. The control chip U2 detects the input power at each power level in real time, compares it with the corresponding theoretical input power, adjusts the duty cycle of the PWM signal according to the difference, and uses the IGBT switch drive circuit to adjust the working state of the insulated gate bipolar transistor IGBT, so that the microwave oven can operate stably and accurately at each power level.

[0017] The beneficial effects of the present invention are as follows: the circuit adjusts the IGBT switch drive circuit and detects the input power of the external variable frequency power supply in real time, compares the actual input power with the theoretical input power, and then dynamically adjusts the duty cycle of the PWM (pulse width modulation) signal generated by the IGBT switch drive circuit to achieve precise control of the working state of the microwave oven; at the same time, the IGBT switch drive circuit parameters and algorithm parameters are adjusted according to the specific application scenario to optimize the measurement performance and ensure stable and efficient operation of the entire system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments with reference to the following drawings.

[0019] Figure 1 It is a control chip diagram of the present invention.

[0020] Figure 2 It is the IGBT switch driving circuit diagram of the present invention.

[0021] Figure 3 FIG. 1 is a circuit diagram of a first embodiment of a power supply circuit of the present invention.

[0022] Figure 4 FIG. 4 is a circuit diagram of a second embodiment of a power supply circuit of the present invention.

[0023] Figure 5 It is the detection waveform diagram of the present invention. DETAILED DESCRIPTION

[0024] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0025] Reference below Figures 1 to 5A microwave oven power adjustment circuit according to an embodiment of the present invention is described, including a power supply circuit, a control chip U2 and an IGBT switch drive circuit, the power supply circuit supplies power to the control chip U2 and the IGBT switch drive circuit respectively, the IGBT switch drive circuit includes an insulated gate bipolar transistor IGBT, a second connector CN2, a unidirectional thyristor TR1, a PWM terminal, an AD terminal, an SCR terminal, an ACL terminal, a sixth resistor R6 and a ZERO terminal, the ACL terminal, the sixth resistor R6 and the ZERO terminal are connected in series, the 4th pin of the control chip U2 is connected to the G pole of the insulated gate bipolar transistor IGBT, and the insulated gate The C pole of the bipolar transistor IGBT is connected to the 1st pin of the second connector CN2, the E pole of the gate bipolar transistor IGBT is connected to the AD terminal, the AD terminal is also connected to the 7th pin of the control chip U2, the 2nd pin of the second connector CN2 is connected to the unidirectional thyristor TR1, the G pole of the unidirectional thyristor TR1 is connected to the 8th pin of the control chip U2, the A pole of the unidirectional thyristor TR1 is connected to the VCC terminal, the control chip U2 is connected to the fire gear button group, the control chip U2 can receive the power detection signal of the IGBT switch drive circuit and issue a control instruction, and the IGBT switch drive circuit can adjust the power according to the instruction of the control chip.

[0026] The circuit realizes dynamic regulation of microwave oven power through IGBT switch drive and bidirectional feedback control. Its core functional modules include power supply, IGBT switch control, zero-crossing detection, current feedback and thyristor-assisted voltage regulation.

[0027] Among them, the power supply circuit supplies power to the control chip U2 and the IGBT switch driving circuit respectively, and two power supply circuits are provided through this circuit. The first one is: the power supply circuit includes a step-down chip POWR1, a +12V terminal and a 5V-OUT terminal, the 8th pin of the step-down chip POWR1 is connected to the +12V terminal, and the 7th pin of the step-down chip POWR1 is connected to the 5V-OUT terminal; the step-down chip POWR1 generates two types of +12V voltage and +5V electricity, which are used to drive the control chip U2 and the IGBT switch driving circuit.

[0028] The second type is: the power supply circuit includes a first plug CN1, a rectifier bridge DB1, a transformer T1, a first inductor L1, a second diode D2, a +5V terminal, a first photocoupler U1 and a regulating chip IC1, pins 1 and 2 of the first plug CN1 are respectively connected to pins 2 and 3 of the rectifier bridge DB1, pin 1 of the rectifier bridge DB1 is connected to pin 1 of the transformer T1, pin 4 of the rectifier bridge DB1 is respectively connected to pins 1, 2, 7 and 8 of the regulating chip IC1, pins 3 and 4 of the regulating chip IC1 are respectively connected to pins 3 and 4 of the first photocoupler U1, pins 2 and 1 of the first photocoupler U1 are respectively connected to pins 5 and 4 of the transformer T1, and pin 4 of the transformer T1 is sequentially connected to the first inductor L1, the second diode D2 and the +5V terminal. The input AC power is rectified into pulsating DC by the rectifier bridge DB1, and is divided into two paths after being stepped down by transformer T1: one path directly outputs +12V voltage, and the other path is filtered and stabilized by the first inductor L1 and the second diode D2 to power the control chip U2 and the sensor. The optocoupler U1 cooperates with the regulating chip IC1 to achieve input and output isolation to avoid high voltage interference with the control circuit. The transformer secondary signal is fed back to the regulating chip IC1 through the optocoupler U1, and the regulating chip IC1 dynamically adjusts the PWM duty cycle to stabilize the output voltage. That is, the regulating chip IC1 controls the output voltage of the transformer T1.

[0029] The PWM drive and power regulation of the IGBT switch drive circuit are: the 4th pin of the control chip U2 outputs a PWM signal, which drives the G pole (gate) of the edge-gate bipolar transistor IGBT after current limiting by the third resistor R3, and controls its conduction frequency and duty cycle. In addition, the C pole (collector) of the edge-gate bipolar transistor IGBT is connected to the second connector CN2 (which may be connected to the magnetron load) through the first resistor R1, and the E pole (emitter) of the edge-gate bipolar transistor IGBT is grounded through the seventh resistor R7 and the eighth resistor R8, forming a current sampling path.

[0030] The A pole of the unidirectional thyristor TR1 described in this circuit is connected to the VCC terminal through the thirteenth resistor R13, and the G pole of the unidirectional thyristor TR1 is connected to the 8th pin of the control chip U2 through the second resistor R2. The C pole of the edge-gate bipolar transistor IGBT described in this circuit is connected to the 1st pin of the second connector CN2 through the first resistor R1. The G pole of the edge-gate bipolar transistor IGBT described in this circuit is connected to the PWM terminal through the third resistor R3. The E pole of the edge-gate bipolar transistor IGBT described in this circuit is also connected in series with the AD terminal by the seventh resistor R7 and the eighth resistor R8. The common end between the seventh resistor R7 and the eighth resistor R8 described in this circuit is connected to the metal film resistor RJ1, and the metal film resistor RJ1 is also connected in parallel with the first capacitor C1, and the other end of the metal film resistor RJ1 is grounded GND. Current feedback and protection of IGBT switch drive circuit: AD terminal (i.e., pin 7 of control chip U2) collects the current signal of the seventh resistor R7 and the eighth resistor R8 in real time, and combines the RC filter network composed of metal film resistor RJ1 and first capacitor C1 to filter out high-frequency noise and then feedback to the control chip. When the current exceeds the limit, the control chip U2 automatically reduces the PWM duty cycle or turns off the gate bipolar transistor IGBT to prevent overcurrent damage. Zero-crossing detection and thyristor coordinated voltage regulation of IGBT switch drive circuit: Zero-crossing synchronization mechanism: ACL terminal, sixth resistor R6 and ZERO terminal are connected in series to form a zero-crossing detection circuit. By monitoring the zero point of the AC phase, it ensures that the IGBT and thyristor triggering are synchronized with the power grid to reduce electromagnetic interference. Thyristor auxiliary voltage regulation: The G pole of the unidirectional thyristor TR1 is controlled by pin 8 (SCR terminal) of the control chip and is triggered by the current limiting of the second resistor R2. When TR1 is turned on, the VCC terminal provides an additional path for the load through the thirteenth resistor R13, maintaining partial power output during the off period of the gate bipolar transistor IGBT, and realizing multi-level power regulation. The dynamic power adjustment process of the IGBT switch drive circuit: load demand response, after the user sets the power, the control chip U2 integrates the AD terminal current signal and the zero-crossing phase; dynamic adjustment: high power mode: increase the conduction frequency of the gate bipolar transistor IGBT, and the unidirectional thyristor TR1 remains normally on; low power mode: reduce the duty cycle of the gate bipolar transistor IGBT, and use the unidirectional thyristor TR1 to intermittently conduct in the AC half cycle to reduce energy output; anti-interference design: the first resistor R1, the third resistor R3, the thirteenth resistor R13, etc. are all used to suppress transient spike voltages and protect the gate bipolar transistor IGBT and thyristors. The optocoupler U1 is an isolated high and low voltage circuit to avoid ground loop interference. The hybrid drive of the edge-gate bipolar transistor IGBT and the unidirectional thyristor TR1 combines the high-frequency switching characteristics of the edge-gate bipolar transistor IGBT and the low-cost advantage of the unidirectional thyristor TR1 to achieve wide range power regulation (such as 100W~1000W).In addition, the dual feedback mechanism: current sampling (AD end) and zero-crossing detection (ZERO end) dual feedback improves control accuracy and response speed; anti-surge design: metal film resistor RJ1 and high-voltage capacitor C1 form a buffer circuit to effectively absorb the reverse electromotive force when the IGBT is turned off. In addition, the firepower button group is mainly used to adjust the heating power command to enter the control chip U2. The control chip U2 implements different gears corresponding to different microwave output methods and applicable scenarios.

[0031] This circuit uses a composite voltage regulation scheme that mainly uses high-frequency PWM to drive the gate bipolar transistor IGBT and supplemented by the phase control of the unidirectional thyristor TR1, combined with real-time current feedback and zero-crossing synchronization technology, to achieve accurate and efficient regulation of the microwave oven power. It also has over-current protection and electromagnetic compatibility characteristics, meeting the dual needs of modern home appliances for energy efficiency and safety.

[0032] The present invention also discloses a power adjustment method using the microwave oven power adjustment circuit, comprising the following steps: Step 1: Initial power detection: The power level of the microwave oven is set to level 1 through a power level button group, and detection and adjustment are started at this level, which can provide basic data and a stable starting state for subsequent adjustment of higher levels; the microwave oven is powered by an external variable frequency power supply, and the connection relationship between the control chip U2 and the insulated gate bipolar transistor IGBT in the IGBT switch drive circuit is utilized (i.e., the 4th pin of the control chip U2 is connected to the G pole of the insulated gate bipolar transistor IGBT, the E pole of the insulated gate bipolar transistor IGBT is connected to the AD terminal, and the AD terminal is also connected to the 7th pin of the control chip U2) to detect the input power of the external variable frequency power supply in real time, and the control chip U2 generates a first input power value; the external variable frequency power supply provides electric energy for the microwave oven, and the size of its input power directly affects the working state of the microwave oven; by detecting the input power in real time, the actual power consumption of the microwave oven at the current power level can be accurately obtained.

[0033] Step 2: Power comparison and duty cycle adjustment The control chip U2 compares the first input power value with the theoretical input power value corresponding to the power level 1 pre-stored in the microwave oven to obtain a first difference. The theoretical input power value is determined during the microwave oven design and testing phase, and represents the ideal power consumption of the microwave oven at power level 1. By comparing the actual input power with the theoretical input power, it can be determined whether the current working state of the microwave oven deviates from the ideal state.

[0034] If the first difference is a positive number, it means that the actual input power is greater than the theoretical input power, and the microwave oven may be in an overpower operation state; at this time, the control chip U2 reduces the first duty cycle of the PWM signal generated by the microcontroller of the microwave oven according to the preset value based on the first difference. Since the PWM terminal in the IGBT switch drive circuit cooperates with the control chip U2, reducing the duty cycle means reducing the average power of the signal, thereby reducing the actual input power of the microwave oven through the working state adjustment of the insulated gate bipolar transistor IGBT, so that it approaches the theoretical input power.

[0035] If the first difference is a non-positive number, it means that the actual input power is less than or equal to the theoretical input power, and the microwave oven may be in an under-power operation state; at this time, the control chip U2 increases the first duty cycle of the PWM signal generated by the microcontroller of the microwave oven according to a preset value based on the first difference, increases the average power of the signal, and increases the actual input power of the microwave oven by adjusting the working state of the insulated gate bipolar transistor IGBT to make it close to the theoretical input power; based on the adjusted first duty cycle, the control chip U2 generates first frequency adjustment information and stores it, and the frequency adjustment information records the duty cycle adjustment status under the current firepower level, providing a basis for subsequent control and analysis.

[0036] Step 3: Adjustment and repeated detection at each level. Increase the power level of the microwave oven by one level and set it to level 2 through the power level button group. As the power level increases, the working intensity of the microwave oven increases, and it is necessary to re-detect the input power and make corresponding adjustments. The same goes for each level, i.e., repeating steps 1 and 2. The control chip U2 detects the input power at each power level in real time, compares it with the corresponding theoretical input power, adjusts the duty cycle of the PWM signal according to the difference, and uses the IGBT switch drive circuit to adjust the working state of the insulated gate bipolar transistor IGBT, so that the microwave oven can operate stably and accurately at each power level.

[0037] like Figure 5 As shown in the figure, the voltage changes with the conduction time of the thyristor at the zero crossing point, and the current changes with the duty cycle of the gate bipolar transistor IGBT. The longer the conduction time of the unidirectional thyristor TR1 is, the higher the voltage is, and vice versa; the larger the duty cycle of the gate bipolar transistor IGBT is, the higher the current is, and vice versa. This ultimately affects the overall power and achieves the overall power effect of controlling the machine.

[0038] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A microwave oven power adjustment circuit, comprising a power supply circuit, characterized in that: It also includes a control chip U2 and an IGBT switch drive circuit. The power circuit supplies power to the control chip U2 and the IGBT switch drive circuit respectively. The IGBT switch drive circuit includes an insulated gate bipolar transistor IGBT, a second connector CN2, a unidirectional thyristor TR1, a PWM terminal, an AD terminal, an SCR terminal, an ACL terminal, a sixth resistor R6 and a ZERO terminal. The ACL terminal, the sixth resistor R6 and the ZERO terminal are connected in series. The 4th pin of the control chip U2 is connected to the G pole of the insulated gate bipolar transistor IGBT, the C pole of the edge gate bipolar transistor IGBT is connected to the 1st pin of the second connector CN2, the E pole of the edge gate bipolar transistor IGBT is connected to the AD terminal, and the AD terminal is also connected to the 7th pin of the control chip U2. The 2nd pin of the second connector CN2 is connected to the unidirectional thyristor TR1, the G pole of the unidirectional thyristor TR1 is connected to the 8th pin of the control chip U2, the A pole of the unidirectional thyristor TR1 is connected to the VCC terminal, and the control chip U2 is connected to a firepower gear button group. The control chip U2 can receive the power detection signal of the IGBT switch drive circuit and issue a control instruction. The IGBT switch drive circuit can adjust the power according to the instruction of the control chip.

2. The microwave oven power adjustment circuit according to claim 1, characterized in that: The A pole of the unidirectional thyristor TR1 is connected to the VCC terminal via a thirteenth resistor R13, and the G pole of the unidirectional thyristor TR1 is connected to the 8th pin of the control chip U2 via a second resistor R2.

3. The microwave oven power adjustment circuit according to claim 2, characterized in that: The C pole of the edge-gate bipolar transistor IGBT is connected to the 1st pin of the second connector CN2 via a first resistor R1.

4. The microwave oven power adjustment circuit according to claim 2, characterized in that: The G pole of the edge-gate bipolar transistor IGBT is connected to the PWM terminal via a third resistor R3.

5. The microwave oven power adjustment circuit according to claim 1, characterized in that: A seventh resistor R7 and an eighth resistor R8 are connected in series between the E terminal and the AD terminal of the edge-gate bipolar transistor IGBT.

6. The microwave oven power adjustment circuit according to claim 5, characterized in that: A common end between the seventh resistor R7 and the eighth resistor R8 is connected to a metal film resistor RJ1, and a first capacitor C1 is also connected in parallel to the metal film resistor RJ1. The other end of the metal film resistor RJ1 is connected to a ground end GND.

7. The microwave oven power adjustment circuit according to claim 1, characterized in that: The power supply circuit comprises a step-down chip POWR1, a +12V terminal and a 5V-OUT terminal, and the 8th pin of the step-down chip POWR1 is connected to the +12V terminal.

8. The microwave oven power adjustment circuit according to claim 1, characterized in that: The power supply circuit includes a first plug CN1, a rectifier bridge DB1, a transformer T1, a first inductor L1, a second diode D2, a +5V terminal, a first photoelectric coupler U1 and a regulating chip IC1. Pin 1 and pin 2 of the first plug CN1 are respectively connected to pin 2 and pin 3 of the rectifier bridge DB1, pin 1 of the rectifier bridge DB1 is connected to pin 1 of the transformer T1, pin 4 of the rectifier bridge DB1 is respectively connected to pin 1, pin 2, pin 7 and pin 8 of the regulating chip IC1, pin 3 and pin 4 of the regulating chip IC1 are respectively connected to pin 3 and pin 4 of the first photoelectric coupler U1, pin 2 and pin 1 of the first photoelectric coupler U1 are respectively connected to pin 5 and pin 4 of the transformer T1, and pin 4 of the transformer T1 is sequentially connected to the first inductor L1, the second diode D2 and the +5V terminal.

9. A power regulation method using the microwave oven power regulation circuit according to any one of claims 1 to 8, characterized in that: The steps include: Step 1: Initial power detection: Set the power level of the microwave oven to level 1 through the power level button group, and start detection and adjustment at this level, which can provide basic data and a stable starting state for subsequent adjustments to higher levels; connect an external variable frequency power supply to power the microwave oven, and use the connection relationship between the control chip U2 and the insulated gate bipolar transistor IGBT in the IGBT switch drive circuit to detect the input power of the external variable frequency power supply in real time, and generate a first input power value by the control chip U2; the external variable frequency power supply provides electrical energy to the microwave oven, and the size of its input power directly affects the working state of the microwave oven; By detecting the input power in real time, the actual power consumption of the microwave oven at the current fire level can be accurately obtained; Step 2: Power comparison and duty cycle adjustment The control chip U2 compares the first input power value with the theoretical input power value corresponding to the power level 1 pre-stored in the microwave oven to obtain a first difference value; the theoretical input power value is determined during the microwave oven design and test phase, and represents the ideal power consumption of the microwave oven at power level 1. By comparing the actual input power with the theoretical input power, it can be determined whether the current working state of the microwave oven deviates from the ideal state; If the first difference is a positive number, it means that the actual input power is greater than the theoretical input power, and the microwave oven may be in an overpower operation state; At this time, the control chip U2 reduces the first duty cycle of the PWM signal generated by the microcontroller of the microwave oven according to a preset value based on the first difference; since the PWM terminal in the IGBT switch drive circuit cooperates with the control chip U2, reducing the duty cycle means reducing the average power of the signal, thereby reducing the actual input power of the microwave oven by adjusting the working state of the insulated gate bipolar transistor IGBT to make it close to the theoretical input power; If the first difference is a non-positive number, it means that the actual input power is less than or equal to the theoretical input power, and the microwave oven may be in an under-power operation state; At this time, the control chip U2 increases the first duty cycle of the PWM signal generated by the microcontroller of the microwave oven according to a preset value based on the first difference, increases the average power of the signal, and increases the actual input power of the microwave oven by adjusting the working state of the insulated gate bipolar transistor IGBT to make it close to the theoretical input power; According to the adjusted first duty cycle, the control chip U2 generates first frequency adjustment information and stores it. The frequency adjustment information records the duty cycle adjustment status under the current firepower level, providing a basis for subsequent control and analysis; Step 3: Adjustment and repeated detection at each level. Increase the power level of the microwave oven by one level and set it to level 2 through the power level button group. As the power level increases, the working intensity of the microwave oven increases, and it is necessary to re-detect the input power and make corresponding adjustments. The same goes for each level, i.e., repeating steps 1 and 2. The control chip U2 detects the input power at each power level in real time, compares it with the corresponding theoretical input power, adjusts the duty cycle of the PWM signal according to the difference, and uses the IGBT switch drive circuit to adjust the working state of the insulated gate bipolar transistor IGBT, so that the microwave oven can operate stably and accurately at each power level.

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