Microwave oven power adjusting circuit

Abstract

The utility model particularly relates to a microwave oven power adjusting circuit, which 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 adjusted step by step to adjust the power of the microwave oven. 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 an IGBT switch driving circuit 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 utility model relates to a microwave oven power adjusting circuit. BACKGROUND

[0002] The microwave oven is an important stove in daily life. The consistency of the microwave power of various gears of the microwave oven becomes an important index. The microwave oven of the related art includes a magnetron for controlling the output power of the microwave. However, the microwave oven of the related art has differences in the microwave oven controller in batch production. It is difficult to achieve the consistency of the input power or the output power of the microwave oven device of the same specification and model, especially the consistency of the microwave power of various gears. The most adverse deviation is caused by the inconsistency of the important index of the input power and the output power of the same specification and model, and the low power and high power products appear, which reduces the cooking quality of food and causes poor quality of the microwave oven. SUMMARY

[0003] The utility model aims at at least one of the technical problems existing in the prior art. Therefore, one purpose of the utility model is to provide a microwave oven power adjusting circuit, which adjusts parameters and algorithm parameters according to specific application scenarios, optimizes measurement performance, and ensures stable and efficient operation of the whole system.

[0004] According to the microwave oven power adjusting circuit, the power supply circuit supplies power to the control chip U2 and the IGBT switch driving circuit, the IGBT switch driving circuit includes the insulated gate bipolar transistor IGBT, the second connector CN2, the one-way thyristor TR1, the PWM end, the AD end, the SCR end, the ACL end, the sixth resistor R6 and the ZERO end, the ACL end, the sixth resistor R6 and the ZERO end 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 insulated gate bipolar transistor IGBT is connected to the 1st pin of the second connector CN2, the E pole of the insulated gate bipolar transistor IGBT is connected to the AD end, the AD end is also connected to the 7th pin of the control chip U2, the 2nd pin of the second connector CN2 is connected to the one-way thyristor TR1, the G pole of the one-way thyristor TR1 is connected to the 8th pin of the control chip U2, the A pole of the one-way thyristor TR1 is connected to the VCC end, the control chip U2 is connected to the firepower gear button group, the control chip U2 can receive the power detection signal of the IGBT switch driving circuit and send the control instruction, and the IGBT switch driving circuit can adjust the power according to the instruction of the control chip.

[0005] Specific further, the A pole of the unidirectional thyristor TR1 is connected with the VCC end through the thirteenth resistance R13, and the G pole of the unidirectional thyristor TR1 is connected with the 8 pin of the control chip U2 through the second resistance R2.

[0006] Specific further, the C pole of the IGBT is connected with the 1 pin of the second connector CN2 through the first resistance R1.

[0007] Specific further, the G pole of the IGBT is connected with the PWM end through the third resistance R3.

[0008] Specific further, the E pole of the IGBT is connected with the AD end through the seventh resistance R7 and the eighth resistance R8.

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

[0010] Specific further, the power supply circuit comprises the step-down chip POWR1, the +12V end and the 5V-OUT end, and the 8 pin of the step-down chip POWR1 is connected with the +12V end.

[0011] Specific further, the power supply circuit comprises the first connector CN1, the rectifier bridge DB1, the transformer T1, the first inductor L1, the second diode D2, the +5V end, the first optocoupler U1 and the adjusting chip IC1, the 1 pin and the 2 pin of the first connector CN1 are connected with the 2 pin and the 3 pin of the rectifier bridge DB1 respectively, the 1 pin of the rectifier bridge DB1 is connected with the 1 pin of the transformer T1, the 4 pin of the rectifier bridge DB1 is connected with the 1 pin, the 2 pin, the 7 pin and the 8 pin of the adjusting chip IC1 respectively, the 3 pin and the 4 pin of the adjusting chip IC1 are connected with the 3 pin and the 4 pin of the first optocoupler U1 respectively, the 2 pin and the 1 pin of the first optocoupler U1 are connected with the 5 pin and the 4 pin of the transformer T1 respectively, and the 4 pin of the transformer T1 is sequentially connected with the first inductor L1, the second diode D2 and the +5V end.

[0012] The beneficial effects of the utility model are: the circuit adjusts IGBT switch drive circuit, and detects input power of external frequency conversion power supply in real time, compares actual input power with theoretical input power, and then dynamically adjusts duty cycle of PWM (pulse width modulation) signal generated by IGBT switch drive circuit, so as to realize accurate control on microwave oven working state. BRIEF DESCRIPTION OF DRAWINGS

[0013] The above and / or additional aspects and advantages of the present utility model will become apparent and more readily appreciated from the following description of the embodiments, with reference to the following figures.

[0014] Figure 1 is the control chip diagram of the present utility model.

[0015] Figure 2 is the IGBT switch driving circuit diagram of the present utility model.

[0016] Figure 3 is the first embodiment circuit diagram of the power supply circuit of the present utility model.

[0017] Figure 4 is the second embodiment circuit diagram of the power supply circuit of the present utility model.

[0018] Figure 5 is the detection waveform diagram of the present utility model. DETAILED DESCRIPTION

[0019] The embodiments of the present utility model will be described in detail below, examples of which are shown in the drawings, wherein the same or similar reference signs represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary, only for explaining the present utility model, and cannot be understood as limiting the present utility model.

[0020] The embodiments of the present utility model will be described in detail below, examples of which are shown in the drawings, wherein the same or similar reference signs represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary, only for explaining the present utility model, and cannot be understood as limiting the present utility model. Figures 1 to 5 A microwave oven power adjusting circuit according to the embodiments of the present utility model is described below, which comprises a power supply circuit, further comprises a control chip U2 and an IGBT switch driving circuit, the power supply circuit respectively supplies power to the control chip U2 and the IGBT switch driving circuit, the IGBT switch driving circuit comprises an insulated gate bipolar transistor IGBT, a second connector CN2, a unidirectional thyristor TR1, a PWM end, an AD end, an SCR end, an ACL end, a sixth resistor R6 and a ZERO end, the ACL end, the sixth resistor R6 and the ZERO end are connected in series, the 4-pin of the control chip U2 is connected to the G pole of the insulated gate bipolar transistor IGBT, the C pole of the insulated gate bipolar transistor IGBT is connected to the 1-pin of the second connector CN2, the E pole of the insulated gate bipolar transistor IGBT is connected to the AD end, the AD end is further connected to the 7-pin of the control chip U2, the 2-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 8-pin of the control chip U2, the A pole of the unidirectional thyristor TR1 is connected to the VCC end, 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 driving circuit and send control instructions, and the IGBT switch driving circuit can adjust the power according to the instructions of the control chip.

[0021] The circuit realizes dynamic adjustment of microwave oven power through IGBT switch driving and bidirectional feedback control, and core function modules thereof include power supply, IGBT switch control, zero-crossing detection, current feedback and thyristor auxiliary voltage regulation.

[0022] The power supply circuit supplies power to the control chip U2 and the IGBT switch driving circuit respectively, and the circuit provides two power supply circuits, the first of which comprises 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 +12V voltage and +5V voltage, which are used to drive the control chip U2 and the IGBT switch driving circuit.

[0023] The second one comprises a first plug CN1, a rectifier bridge DB1, a transformer T1, a first inductor L1, a second diode D2, a +5V terminal, a first optocoupler U1 and a regulating chip IC1, the 1st pin and the 2nd pin of the first plug CN1 are connected to the 2nd pin and the 3rd pin of the rectifier bridge DB1 respectively, the 1st pin of the rectifier bridge DB1 is connected to the 1st pin of the transformer T1, the 4th pin of the rectifier bridge DB1 is connected to the 1st pin, the 2nd pin, the 7th pin and the 8th pin of the regulating chip IC1 respectively, the 3rd pin and the 4th pin of the regulating chip IC1 are connected to the 3rd pin and the 4th pin of the first optocoupler U1 respectively, the 2nd pin and the 1st pin of the first optocoupler U1 are connected to the 5th pin and the 4th pin of the transformer T1 respectively, and the 4th pin of the transformer T1 is sequentially connected with the first inductor L1, the second diode D2 and the +5V terminal. The input alternating current is rectified into pulsating direct current by the rectifier bridge DB1, and is divided into two paths after being stepped down by the 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, and is used to supply power to the control chip U2 and the sensor, the first optocoupler U1 and the regulating chip IC1 cooperate to realize input-output isolation, so as to avoid high-voltage interference to the control circuit. The secondary signal of the transformer is fed back to the regulating chip IC1 through the first 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.

[0024] The PWM driving and power regulation of the IGBT switch driving circuit are as follows: 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 being current-limited by the third resistor R3, so as to control the on-off frequency and the duty cycle of the edge gate bipolar transistor IGBT. In addition, the C pole (collector) of the edge gate bipolar transistor IGBT is connected to the second connector CN2 (which can be connected to a 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, so as to form a current sampling path.

[0025] The A pole of the unidirectional thyristor TR1 is connected with the VCC end through the thirteenth resistor R13, and the G pole of the unidirectional thyristor TR1 is connected with the 8 pin of the control chip U2 through the second resistor R2. The C pole of the edge gate bipolar transistor IGBT is connected with the 1 pin of the second joint CN2 through the first resistor R1. The G pole of the edge gate bipolar transistor IGBT is connected with the PWM end through the third resistor R3. The E pole of the edge gate bipolar transistor IGBT is connected with the AD end through the seventh resistor R7 and the eighth resistor R8 in series. The common end between the seventh resistor R7 and the eighth resistor R8 is connected with the metal film resistor RJ1, the metal film resistor RJ1 is connected with the first capacitor C1 in parallel, and the other end of the metal film resistor RJ1 is connected with the ground end GND. The current feedback and protection of the IGBT switch driving circuit: the AD end (i.e. the 7 pin of the control chip U2) collects the current signal of the voltage division of the seventh resistor R7 and the eighth resistor R8 in real time, combines the RC filter network composed of the metal film resistor RJ1 and the first capacitor C1, feeds back to the control chip after filtering out high-frequency noise. When the current is out of limit, the control chip U2 automatically reduces the PWM duty ratio or closes the edge gate bipolar transistor IGBT to prevent overcurrent damage. The zero-crossing detection and thyristor cooperative voltage regulation of the IGBT switch driving circuit: the zero-crossing synchronization mechanism: the ACL end, the sixth resistor R6 and the ZERO end are connected in series to form a zero-crossing detection circuit, which monitors the phase zero point of the alternating current to ensure that the IGBT and the thyristor trigger are synchronized with the power grid, reducing electromagnetic interference. Thyristor auxiliary voltage regulation: the G pole of the unidirectional thyristor TR1 is controlled by the 8 pin (SCR end) of the control chip, and is triggered by the second resistor R2. When TR1 is turned on, the VCC end provides an additional path for the load through the thirteenth resistor R13, maintaining partial power output during the shutdown of the edge gate bipolar transistor IGBT, and realizing multi-stage power regulation. The dynamic power adjustment process of the IGBT switch driving circuit: the load demand response, after the user sets the power, the control chip U2 combines the AD end current signal and the zero-crossing phase; dynamic adjustment: high power mode: increase the conduction frequency of the edge gate bipolar transistor IGBT, and the unidirectional thyristor TR1 remains always on; low power mode: reduce the duty ratio of the edge gate bipolar transistor IGBT, and use the unidirectional thyristor TR1 to intermittently conduct in the alternating current half cycle to reduce energy output; anti-interference design: the first resistor R1, the third resistor R3, the thirteenth resistor R13, etc. are used to suppress transient peak voltage to protect the edge gate bipolar transistor IGBT and the thyristor. The optoelectronic coupler U1 belongs to an isolation high-low voltage circuit to avoid ground loop interference. The edge gate bipolar transistor IGBT and the unidirectional thyristor TR1 are mixed driven, combining the high-frequency switching characteristics of the edge gate bipolar transistor IGBT and the low-cost advantage of the unidirectional thyristor TR1 to realize wide-range power regulation (such as 100W~1000W).In addition, double feedback mechanism: current sampling (AD end) and zero-crossing detection (ZERO end) double feedback, improve control accuracy and response speed; Anti-surge design: metal film resistor RJ1 and high voltage capacitor C1 form a buffer circuit, effectively absorbing the reverse electromotive force when IGBT is off. In addition, the firepower button group is mainly used to adjust the heating power command into the control chip U2, and the control chip U2 implements different microwave output modes and application scenarios corresponding to different gears.

[0026] The circuit realizes precise and efficient adjustment of the microwave oven power by the composite voltage regulation scheme of high-frequency PWM driving IGBT as the main part and phase control of one-way thyristor TR1 as the auxiliary part, cooperates with real-time current feedback and zero-crossing synchronization technology, realizes precise and efficient adjustment of the microwave oven power, and has overcurrent protection and electromagnetic compatibility characteristics, and meets the double requirements of energy efficiency and safety of modern household appliances.

[0027] The power adjustment method applied to the microwave oven power adjustment circuit comprises the following steps: step one: initial power detection; the firepower of the microwave oven is set to 1 gear through the firepower button group, and the initial power is detected and adjusted at the gear, so that the basic data and stable starting state are provided for the adjustment of the higher gear; the external frequency conversion power supply is connected to supply power to the microwave oven, the connection relationship (i.e. the 4th pin of the control chip U2 is connected to the G pole of the IGBT, the E pole of the IGBT is connected with the AD end, and the AD end is also connected with the 7th pin of the control chip U2) between the control chip U2 and the IGBT in the IGBT switch driving circuit is utilized, the input power of the external frequency conversion power supply is detected in real time, and the first input power value is generated by the control chip U2; the external frequency conversion power supply provides power for the microwave oven, and the size of the 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 firepower can be accurately obtained.

[0028] Step two: 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 1-gear firepower of the microwave oven pre-stored in the microwave oven, and obtains the first difference. The theoretical input power value is determined in the design and test stage of the microwave oven, and represents the ideal power consumption of the microwave oven at 1-gear firepower; by comparing the actual input power with the theoretical input power, whether the current working state of the microwave oven deviates from the ideal state can be judged.

[0029] If the first difference is positive, it means that the actual input power is greater than the theoretical input power, and the microwave oven may be in an over-power running 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 first difference by a preset value. Since the PWM end in the IGBT switch driving circuit works with the control chip U2, reducing the duty cycle means reducing the average power of the signal, thereby adjusting the working state of the insulated gate bipolar transistor IGBT to reduce the actual input power of the microwave oven, so as to approach the theoretical input power.

[0030] If the first difference is not positive, 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 running 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 the first difference by a preset value, increases the average power of the signal, and adjusts the working state of the insulated gate bipolar transistor IGBT to increase the actual input power of the microwave oven, so as to approach the theoretical input power; according to 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 situation under the current firepower level, which provides a basis for subsequent control and analysis;

[0031] Step three: adjusting and repeatedly detecting by level By the firepower level button group, the firepower level of the microwave oven is increased by one level and set to 2; with the increase of the firepower level, the working intensity of the microwave oven increases, and the input power needs to be detected again and adjusted accordingly; each level is similar to the operation of step one and step two, that is, the operation of step one and step two is repeated, the control chip U2 detects the input power under each firepower 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 adjusts the working state of the insulated gate bipolar transistor IGBT by using the IGBT switch driving circuit, so that the microwave oven can stably and accurately run under each firepower level.

[0032] The utility model aims at through adjusting by level to microwave oven firepower level, and detecting input power of external variable frequency power supply in real time, comparing actual input power with theoretical input power, and then dynamically adjusting the duty cycle of the PWM (pulse width modulation) signal generated by the microcontroller of the microwave oven, to realize accurate control of the working state of the microwave oven. At the same time, according to the specific application scene, the parameters and algorithm parameters of the capacitive sensor are adjusted to optimize the measurement performance and ensure that the whole system runs stably and efficiently.

[0033] For example, Figure 5As shown, by detecting that the voltage changes with the turn-on time of the silicon controlled rectifier at the zero-crossing point, the current changes with the duty cycle of the IGBT.

[0034] Although the embodiments of the utility model have been shown and described, those skilled in the art can understand that various changes, modifications, replacements and variations can be made to these embodiments without departing from the principles and purposes of the utility model, and the scope of the utility model is defined by the claims and their equivalents.

Claims

1. A microwave oven power regulation circuit comprising a power supply circuit, characterized by: The control chip U2 and the IGBT switch driving circuit are further included, the power supply circuit supplies power to the control chip U2 and the IGBT switch driving circuit respectively, the IGBT switch driving 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 insulated gate bipolar transistor IGBT is connected to the 1st pin of the second connector CN2, the E pole of the insulated gate bipolar transistor IGBT is connected to the AD terminal, the AD terminal is further 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 firepower gear button group, the control chip U2 can receive the power detection signal of the IGBT switch driving circuit and send a control instruction, and the IGBT switch driving circuit can adjust the power according to the instruction of the control chip.

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

3. The microwave power regulation circuit of claim 2, wherein: The C pole of the insulated gate bipolar transistor IGBT and the 1st pin of the second connector CN2 are connected through the first resistor R1.

4. The microwave power regulation circuit of claim 2, wherein: The G pole of the insulated gate bipolar transistor IGBT and the PWM terminal are connected through the third resistor R3.

5. The microwave power regulation circuit of claim 1, wherein: The E pole of the insulated gate bipolar transistor IGBT and the AD terminal are further connected in series with the seventh resistor R7 and the eighth resistor R8.

6. The microwave power regulation circuit of claim 5, wherein: The common terminal between the seventh resistor R7 and the eighth resistor R8 is connected with a metal film resistor RJ1, the metal film resistor RJ1 is further connected in parallel with a first capacitor C1, and the other end of the metal film resistor RJ1 is connected to the ground terminal GND.

7. The microwave power regulation circuit of claim 1, wherein: 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.

8. The microwave power regulation circuit of claim 1, wherein: 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 optocoupler U1 and an adjusting chip IC1, the 1st pin and the 2nd pin of the first plug CN1 are respectively connected to the 2nd pin and the 3rd pin of the rectifier bridge DB1, the 1st pin of the rectifier bridge DB1 is connected to the 1st pin of the transformer T1, the 4th pin of the rectifier bridge DB1 is respectively connected to the 1st pin, the 2nd pin, the 7th pin and the 8th pin of the adjusting chip IC1, the 3rd pin and the 4th pin of the adjusting chip IC1 are respectively connected to the 3rd pin and the 4th pin of the first optocoupler U1, the 2nd pin and the 1st pin of the first optocoupler U1 are respectively connected to the 5th pin and the 4th pin of the transformer T1, and the 4th pin of the transformer T1 is sequentially connected with the first inductor L1, the second diode D2 and the +5V terminal.

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