Electromagnet bridge type control circuit and microwave oven

Abstract

The utility model provides an electromagnet bridge type control circuit and a microwave oven. The circuit comprises a single-chip microcomputer, a positive switching circuit, a negative switching circuit, an overcurrent protection circuit, a sampling resistor and an electromagnet. The single-chip microcomputer is connected with the electromagnet through the positive switching circuit and the negative switching circuit, the positive switching circuit is connected with the overcurrent protection circuit through the negative switching circuit, and one end, away from the negative switching circuit, of the overcurrent protection circuit is connected with one end of the sampling resistor. The other end, far away from the negative switching circuit, of the overcurrent protection circuit and the other end of the sampling resistor are connected in parallel and grounded; according to the electromagnet bridge type control circuit and the microwave oven, the structure of the control circuit can be simplified, and the production cost of the microwave oven is reduced. And interference of induced current can be avoided through optimization of the control circuit, the reliability of the control circuit is improved, and the working efficiency of the control circuit is improved.

Description

Technical Field

[0001] This utility model relates to the field of microwave oven technology, and more specifically, to an electromagnet bridge control circuit for two-step door opening and a microwave oven. Background Technology

[0002] To meet the two-step door opening requirement of the new UL standard, some microwave oven control systems use electromagnets. These electromagnets typically have two windings: one energized for a push-button action, and the other for a pull-button action. Together, they control the door lock, achieving the first step of opening the door. However, having two windings significantly increases the number of turns in the electromagnet's coil, and the winding directions of the two windings need to be distinguished, thus increasing the production cost of the electromagnet within the microwave oven. Furthermore, the two windings cannot operate simultaneously; when one winding is energized, the other will also have an induced current, causing interference and potentially leading to electromagnet malfunction. Therefore, researching how to optimize the internal circuitry of microwave ovens while reducing production costs and minimizing current interference is of great significance.

[0003] Patent CN212299459U discloses a safety protection circuit and a microwave oven, including a button circuit, a button detection circuit, a button control circuit, an output control circuit, a door detection circuit, and a processor. In the button detection circuit, the second terminal of the switching transistor Q4 is connected to the first terminal of Q4 via a resistor R4 and is used to connect to a third power supply. The third terminal is used to connect to the second terminal of the motor. A capacitor C2 is connected in parallel to the first terminal of the switching transistor Q4 for filtering and interference prevention. This provides protection when the user is using the microwave oven, but it does not solve the problems of complex control circuitry, high production costs, and significant current interference during the electromagnet-controlled door opening and closing process. Utility Model Content

[0004] In view of this, the present invention aims to propose an electromagnet bridge control circuit and a microwave oven to solve the problems existing in the prior art, such as the complexity of the control circuit, the high production cost of the microwave oven, and the significant current interference between different windings in the circuit during the electromagnet-controlled opening and closing of the oven door. This simplifies the control circuit structure and reduces the production cost of the microwave oven. Furthermore, by optimizing the control circuit, it avoids interference from induced currents, improves the reliability of the control circuit, and enhances its working efficiency.

[0005] To achieve the above objectives, the technical solution of this utility model is implemented as follows:

[0006] This utility model relates to an electromagnet bridge control circuit and a microwave oven. The electromagnet bridge control circuit includes a microcontroller, a positive switch circuit, a negative switch circuit, an overcurrent protection circuit, a sampling resistor, and an electromagnet. The microcontroller is connected to the electromagnet through the positive switch circuit and the negative switch circuit. The positive switch circuit is connected to the overcurrent protection circuit through the negative switch circuit. The end of the overcurrent protection circuit away from the negative switch circuit is connected to one end of the sampling resistor, and the other end of the overcurrent protection circuit away from the negative switch circuit is connected to ground in parallel with the other end of the sampling resistor.

[0007] Furthermore, the electromagnet is a single-winding magnetically protected electromagnet.

[0008] Furthermore, the microcontroller includes a controller, which is integrated inside the microcontroller.

[0009] Furthermore, the positive switch circuit includes a positive switch circuit one and a positive switch circuit two; both positive switch circuit one and positive switch circuit two are connected to the microcontroller and the electromagnet respectively, and one end of positive switch circuit one and positive switch circuit two are connected in parallel to the power supply VDD.

[0010] Furthermore, the positive switch circuit includes a first transistor Q1, a third transistor Q3, a second resistor R2, a fourth resistor R4, and a fifth resistor R5. The emitter of the first transistor Q1 is connected in parallel with one end of the second resistor R2 and then connected to the power supply VDD. The base of the first transistor Q1 is connected in parallel with the other end of the second resistor R2 and then connected to the collector of the third transistor Q3 through the fourth resistor R4. The collector of the first transistor Q1 is connected to pin 2 of the electromagnet and the negative switch circuit, respectively. The base of the third transistor Q3 is connected to pin CON2 of the microcontroller through the fifth resistor R5.

[0011] Furthermore, the negative switch circuit includes a negative switch circuit one and a negative switch circuit two; both negative switch circuit one and negative switch circuit two are respectively connected to the microcontroller, the electromagnet, the positive switch circuit, and the overcurrent protection circuit.

[0012] Furthermore, the negative switch circuit includes a fifth transistor Q5 and an eighth resistor R8; the collector of the fifth transistor Q5 is connected to pin 2 of the electromagnet and the positive switch circuit, respectively; the emitter and base of the fifth transistor Q5 are both connected to the overcurrent protection circuit; and the base of the fifth transistor Q5 is connected to pin CON1 of the microcontroller through the eighth resistor R8.

[0013] Furthermore, the overcurrent protection circuit includes a protection circuit one and a protection circuit two; both protection circuit one and protection circuit two are connected to the negative switch circuit, and the ends of protection circuit one and protection circuit two away from the negative switch circuit are connected to one end of the sampling resistor; the other ends of protection circuit one and protection circuit two away from the negative switch circuit and the other end of the sampling resistor are connected to ground in parallel.

[0014] Furthermore, the protection circuit includes an eighth transistor Q8, a second capacitor C2, and a tenth resistor R10; the collector of the eighth transistor Q8 is connected to the base of the fifth transistor Q5, the base of the eighth transistor Q8 is connected to one end of the tenth resistor R10 and the second capacitor C2 respectively, the other end of the tenth resistor R10 is connected to the emitter of the fifth transistor Q5 and one end of the sampling resistor respectively, and the emitter of the eighth transistor Q8, the second capacitor C2, and the other end of the sampling resistor are connected to ground in parallel.

[0015] A microwave oven includes an electromagnet bridge control circuit, the control circuit being disposed inside the microwave oven.

[0016] Compared with the prior art, the electromagnet bridge control circuit and microwave oven described in this utility model have the following advantages:

[0017] By configuring the control circuit as described, the structure of the control circuit can be simplified, the number of electromagnet windings can be reduced, the manufacturing process of the electromagnet can be improved, and the cost of the electromagnet can be reduced, thereby reducing the production cost of the microwave oven. Furthermore, the optimization of the control circuit can avoid interference from induced currents, improve the reliability of the control circuit, and enhance its operating efficiency. Attached Figure Description

[0018] The accompanying drawings, which constitute a part of this utility model, are used to provide a further understanding of the utility model. The illustrative embodiments and descriptions of the utility model are used to explain the utility model and do not constitute an undue limitation of the utility model. In the drawings:

[0019] Figure 1 This is a schematic diagram of the overall circuit principle of the control circuit.

[0020] Explanation of reference numerals in the attached diagram: 1. Microcontroller; 2. Positive switch circuit; 21. Positive switch one circuit; 22. Positive switch two circuit; 3. Negative switch circuit; 31. Negative switch one circuit; 32. Negative switch two circuit; 4. Overcurrent protection circuit; 41. Protection one circuit; 42. Protection two circuit; 5. Sampling resistor; 6. Electromagnet. Detailed Implementation

[0021] The inventive concepts of this disclosure will be described below using terminology commonly used by those skilled in the art to convey the essence of their work to others skilled in the art. However, these inventive concepts may be embodied in many different forms and should not be construed as limited to the embodiments described herein.

[0022] It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments of the present invention can be combined with each other.

[0023] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0024] This embodiment is for a microwave oven. Similar to a conventional microwave oven, the overall structure consists of an oven door, a turntable mechanism, and an oven cavity.

[0025] To address the problems of complex control circuits, high microwave oven production costs, and significant current interference between different windings in existing electromagnet-controlled oven door opening and closing technologies, this embodiment proposes an electromagnet bridge control circuit and a microwave oven. The electromagnet bridge control circuit includes a microcontroller 1, a positive switching circuit 2, a negative switching circuit 3, an overcurrent protection circuit 4, a sampling resistor 5, and an electromagnet 6. The microcontroller 1 is connected to the electromagnet 6 through the positive switching circuit 2 and the negative switching circuit 3. The positive switching circuit 2 is connected to the overcurrent protection circuit 4 through the negative switching circuit 3. The end of the overcurrent protection circuit 4 furthest from the negative switching circuit 3 is connected to one end of the sampling resistor 5, and the other end of the overcurrent protection circuit 4 furthest from the negative switching circuit 3 is connected in parallel to the other end of the sampling resistor 5 and grounded. The electromagnet 6 is a single-winding magnetically protected electromagnet. When pin 1 of the inner winding of the electromagnet 6 is positive and pin 2 is negative, the electromagnet 6 performs a push-rod action; when pin 1 of the inner winding of the electromagnet 6 is negative and pin 2 is positive, the electromagnet 6 performs a pull-rod action.

[0026] By configuring the control circuit as described above, the structure of the control circuit can be simplified, the number of electromagnet windings can be reduced, the manufacturing process of electromagnet 6 can be improved, and the cost of electromagnet 6 can be reduced, thereby reducing the production cost of microwave ovens. Furthermore, the optimization of the control circuit can avoid interference from induced currents, improve the reliability of the control circuit, and enhance its operating efficiency.

[0027] The microcontroller 1 includes a controller, which is integrated inside the microcontroller 1 and is used to send signals to the control circuit indicating the actions that the electromagnet 6 needs to perform. The action signals that the electromagnet 6 needs to perform include any one of the following: a push-rod action signal, a pull-rod action signal, or a no-action signal.

[0028] The positive switch circuit 2 includes a positive switch circuit 1 21 and a positive switch circuit 22. Both positive switch circuit 1 21 and positive switch circuit 22 are connected to the microcontroller 1 and the electromagnet 6, respectively. One end of positive switch circuit 1 21 and positive switch circuit 22 are connected in parallel and then connected to the power supply VDD.

[0029] The positive switch circuit 21 includes a first transistor Q1, a third transistor Q3, a second resistor R2, a fourth resistor R4, and a fifth resistor R5. The emitter of the first transistor Q1 is connected in parallel with one end of the second resistor R2 and then connected to the power supply VDD. The base of the first transistor Q1 is connected in parallel with the other end of the second resistor R2 and then connected to the collector of the third transistor Q3 through the fourth resistor R4. The collector of the first transistor Q1 is connected to pin 2 of the electromagnet 6 and the negative switch circuit 3. The base of the third transistor Q3 is connected to pin CON2 of the microcontroller 1 through the fifth resistor R5.

[0030] The positive switch circuit 22 includes a second transistor Q2, a fourth transistor Q4, a first resistor R1, a third resistor R3, and a sixth resistor R6. The emitter of the second transistor Q2 is connected in parallel with one end of the first resistor R1 and then connected to the power supply VDD. The base of the second transistor Q2 is connected in parallel with the other end of the first resistor R1 and then connected to the collector of the fourth transistor Q4 through the third resistor R3. The collector of the second transistor Q2 is connected to pin 1 of the electromagnet 6 and the negative switch circuit 3. The base of the fourth transistor Q4 is connected to pin CON1 of the microcontroller 1 through the third resistor R3.

[0031] By setting up positive switch circuit 21 and positive switch circuit 22, the positive terminal VDD of the power supply can be turned on and off. Since both are set in the control circuit, the electromagnet 6 can switch between the two circuit directions through a single winding. This reduces the number of windings and the production cost of the electromagnet 6, thereby avoiding the generation of induced current and ensuring the safe and stable operation of the circuit.

[0032] The negative switch circuit 3 includes a negative switch circuit 31 and a negative switch circuit 32. Both the negative switch circuit 31 and the negative switch circuit 32 are connected to the microcontroller 1, the electromagnet 6, the positive switch circuit 2, and the overcurrent protection circuit 4, respectively.

[0033] The negative switch circuit 31 includes a fifth transistor Q5 and an eighth resistor R8. The collector of the fifth transistor Q5 is connected to pin 2 of the electromagnet 6 and the collector of the first transistor Q1 of the positive switch circuit 21. The emitter and base of the fifth transistor Q5 are both connected to the overcurrent protection circuit 4. The base of the fifth transistor Q5 is connected to pin CON1 of the microcontroller 1 through the eighth resistor R8.

[0034] The negative switch circuit 32 includes a sixth transistor Q6 and a seventh resistor R7. The collector of the sixth transistor Q6 is connected to pin 1 of the electromagnet 6 and the collector of the second transistor Q2 in the positive switch circuit 22. The emitter and base of the sixth transistor Q6 are both connected to the overcurrent protection circuit 4. The base of the sixth transistor Q6 is connected to pin CON2 of the microcontroller 1 through the seventh resistor R7.

[0035] By configuring negative switch circuit 31 and negative switch circuit 32, the negative terminal GND of the power supply can be turned on and off. Furthermore, their coordination with positive switch circuit 21 and positive switch circuit 22 respectively improves the integrity and reliability of the control circuit and avoids interference between control signals.

[0036] The overcurrent protection circuit 4 includes a first protection circuit 41 and a second protection circuit 42. Both the first protection circuit 41 and the second protection circuit 42 are connected to the negative switch circuit 3. The ends of the first protection circuit 41 and the second protection circuit 42 away from the negative switch circuit 3 are connected to one end of the sampling resistor 5. The other ends of the first protection circuit 41 and the second protection circuit 42 away from the negative switch circuit 3 and the other end of the sampling resistor 5 are connected to ground in parallel.

[0037] The protection circuit 41 includes an eighth transistor Q8, a second capacitor C2, and a tenth resistor R10. The collector of the eighth transistor Q8 is connected to the base of the fifth transistor Q5 in the negative switch circuit 31. The base of the eighth transistor Q8 is connected to one end of the tenth resistor R10 and the second capacitor C2. The other end of the tenth resistor R10 is connected to the emitter of the fifth transistor Q5 in the negative switch circuit 31 and one end of the sampling resistor 5. The emitter of the eighth transistor Q8, the second capacitor C2, and the other end of the sampling resistor 5 are connected to ground in parallel.

[0038] The second protection circuit 42 includes a seventh transistor Q7, a first capacitor C1, and a ninth resistor R9. The collector of the seventh transistor Q7 is connected to the base of the sixth transistor Q6. The base of the seventh transistor Q7 is connected to one end of the ninth resistor R9 and one end of the first capacitor C1. The other end of the ninth resistor R9 is connected to the emitter of the sixth transistor Q6 and one end of the sampling resistor 5. The emitter of the seventh transistor Q7, the first capacitor C1, and the other end of the sampling resistor 5 are connected to ground in parallel.

[0039] By adding the hardware overcurrent protection circuit 4, the structural stability of the control circuit is enhanced, and its reliability and safety are improved. This makes the microwave oven more reliable to use. Furthermore, the overcurrent protection circuit 4 implements overcurrent protection for the control circuit in hardware, eliminating the need for an additional control port on the microcontroller 1 processor. This allows the control circuit to respond to microcontroller 1 commands faster and also makes communication between the control circuit and microcontroller 1 more reliable.

[0040] The positive switch circuit 21 and positive switch circuit 22, the negative switch circuit 31 and negative switch circuit 32, the protection circuit 41 and protection circuit 42, the electromagnet 6, and the sampling resistor 5 constitute a bridge control circuit; and the electromagnet 6 in this bridge control circuit only needs one winding for control. The power signal at both ends of this single winding can be positive at one end and negative at the other end; or negative at one end and positive at the other end, thereby realizing the switching of the two current directions of the single winding, thus ensuring that the electromagnet 6 can perform push rod and pull rod actions.

[0041] By using a single-winding electromagnet 6, bidirectional current control within the control circuit can be achieved, thereby significantly reducing the number of windings and improving the manufacturing process of the electromagnet 6, while also lowering its cost. Furthermore, the single winding eliminates the interference of induced currents found in dual-winding systems, greatly improving the reliability of the control circuit. Moreover, the control circuit design of this application does not increase the overall standby power consumption. During standby, all transistors in the control circuit are in the off state, resulting in no increased power loss, significantly conserving resources, extending the circuit's lifespan, and reducing operating costs.

[0042] A microwave oven includes an electromagnet bridge control circuit, the control circuit being disposed inside the microwave oven.

[0043] Working principle:

[0044] When the controller inside microcontroller 1 issues a push rod action command, that is, pin CON1 of microcontroller 1 is at a high level and pin CON2 is at a low level. Since pin CON1 is at a high level, the fourth transistor Q4 of the positive switch circuit 22 is turned on, and the signal at the collector (C) of Q4 is pulled low. Then the second transistor Q2 is turned on, and pin 1 of electromagnet 6 is a positive power supply signal. At the same time, the fifth transistor Q5 of the negative switch circuit 31 is turned on, and the collector signal of Q5 is pulled low to a negative power supply signal, that is, pin 2 of electromagnet 6 is a negative power supply signal. Furthermore, since pin CON2 of microcontroller 1 is a low-level signal, the sixth transistor Q6 of the negative switch circuit 32 is in the off state, and the third transistors Q3 and Q1 of the positive switch circuit 21 are also in the off state. Therefore, the entire bridge circuit applies a positive power supply signal to pin 1 of electromagnet 6 and a negative power supply signal to pin 2. Under normal operation, the voltage across the sampling resistor 5 does not reach the turn-on voltage of the eighth transistor Q8 of the protection circuit 41, that is, the overcurrent protection is not triggered. Therefore, the fifth transistor Q5 of the negative switch circuit 31 is still in the conducting state, and the electromagnet 6 realizes the push rod action.

[0045] When the controller of microcontroller 1 issues a lever action command, that is, pin CON1 of microcontroller 1 is at a low level and pin CON2 is at a high level. Since CON2 is a high-level signal, transistor Q3 in the positive switch circuit 21 is turned on, and the signal at the collector (C) of Q3 is pulled low. Therefore, the first transistor Q1 is turned on, and pin 2 of electromagnet 6 receives a positive power supply signal. Simultaneously, the sixth transistor Q6 in the negative switch circuit 32 is turned on, and the collector signal of Q6 is pulled low to a negative power supply signal, meaning pin 1 of electromagnet 6 receives a negative power supply signal. Furthermore, since microcontroller 1... When pin CON1 is low, transistor Q5 in negative switch circuit 31 is in the off state, and transistors Q4 and Q2 in positive switch circuit 22 are also in the off state. The entire bridge circuit applies a negative power supply signal to pin 1 and a positive power supply signal to pin 2 of electromagnet 6. Since the voltage across sampling resistor 5 does not reach the turn-on voltage of transistor Q7 in protection circuit 42 under normal operation, i.e., overcurrent protection is not triggered, transistor Q6 in negative switch circuit 32 is still in the conducting state, and electromagnet 6 achieves the lever action.

[0046] When the controller of microcontroller 1 issues a command to keep electromagnet 6 inactive, that is, when pin CON1 and pin CON2 of microcontroller 1 are at low level, all transistors in the entire bridge circuit are in the cut-off state. Therefore, no voltage is applied to the two ends of the winding of electromagnet 6, and electromagnet 6 does not move.

[0047] In addition, the bridge circuit in this application has a hardware overcurrent protection function. That is, when the bridge circuit is overcurrent, the voltage across the sampling resistor 5, i.e., R11 in the figure, will rise. When it reaches the turn-on voltage of transistor Q7 in protection circuit 2 or transistor Q8 in protection circuit 1, the base voltage of transistor Q6 in negative switch circuit 2 32 is pulled down to ground, making transistor Q6 in the cutoff state, or the base voltage of transistor Q5 in negative switch circuit 1 31 is pulled down to ground, making transistor Q5 in the cutoff state, thus cutting off the current loop of the bridge circuit. Therefore, the bridge circuit will not burn out due to overcurrent.

[0048] In this utility model, any microwave oven may include the electromagnet bridge control circuit structure described in this embodiment. In addition to the relevant structures and assembly relationships of the electromagnet 6 and the microcontroller 1 provided in this embodiment, the microwave oven also includes conventional components such as the oven door, turntable mechanism, and oven cavity. Since these are all prior art, they will not be described in detail here.

[0049] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. An electromagnet bridge control circuit, characterized in that, It includes a microcontroller (1), a positive switch circuit (2), a negative switch circuit (3), an overcurrent protection circuit (4), a sampling resistor (5), and an electromagnet (6); the microcontroller (1) is connected to the electromagnet (6) through the positive switch circuit (2) and the negative switch circuit (3), the positive switch circuit (2) is connected to the overcurrent protection circuit (4) through the negative switch circuit (3), the end of the overcurrent protection circuit (4) away from the negative switch circuit (3) is connected to one end of the sampling resistor (5), and the other end of the overcurrent protection circuit (4) away from the negative switch circuit (3) is connected to ground in parallel with the other end of the sampling resistor (5).

2. The electromagnet bridge control circuit according to claim 1, characterized in that, The electromagnet (6) is a single-winding magnetically protected electromagnet.

3. The electromagnet bridge control circuit according to claim 2, characterized in that, The microcontroller (1) includes a controller, which is integrated inside the microcontroller (1).

4. The electromagnet bridge control circuit according to claim 2, characterized in that, The positive switch circuit (2) includes a positive switch circuit one (21) and a positive switch circuit two (22); the positive switch circuit one (21) and the positive switch circuit two (22) are respectively connected to the microcontroller (1) and the electromagnet (6), and one end of the positive switch circuit one (21) and the positive switch circuit two (22) are connected in parallel to the power supply VDD.

5. The electromagnet bridge control circuit according to claim 4, characterized in that, The positive switch circuit (21) includes a first transistor Q1, a third transistor Q3, a second resistor R2, a fourth resistor R4, and a fifth resistor R5. The emitter of the first transistor Q1 is connected in parallel with one end of the second resistor R2 and then connected to the power supply VDD. The base of the first transistor Q1 is connected in parallel with the other end of the second resistor R2 and then connected to the collector of the third transistor Q3 through the fourth resistor R4. The collector of the first transistor Q1 is connected to pin 2 of the electromagnet (6) and the negative switch circuit (3) respectively. The base of the third transistor Q3 is connected to pin CON2 of the microcontroller (1) through the fifth resistor R5.

6. The electromagnet bridge control circuit according to claim 4, characterized in that, The negative switch circuit (3) includes a negative switch circuit 1 (31) and a negative switch circuit 2 (32); the negative switch circuit 1 (31) and the negative switch circuit 2 (32) are respectively connected to the microcontroller (1), the electromagnet (6), the positive switch circuit (2) and the overcurrent protection circuit (4).

7. An electromagnet bridge control circuit according to claim 6, characterized in that, The negative switch circuit (31) includes a fifth transistor Q5 and an eighth resistor R8; the collector of the fifth transistor Q5 is connected to pin 2 of the electromagnet (6) and the positive switch circuit (21) respectively; the emitter and base of the fifth transistor Q5 are connected to the overcurrent protection circuit (4); and the base of the fifth transistor Q5 is connected to pin CON1 of the microcontroller (1) through the eighth resistor R8.

8. The electromagnet bridge control circuit according to claim 7, characterized in that, The overcurrent protection circuit (4) includes a first protection circuit (41) and a second protection circuit (42); both the first protection circuit (41) and the second protection circuit (42) are connected to the negative switch circuit (3), and the ends of the first protection circuit (41) and the second protection circuit (42) away from the negative switch circuit (3) are connected to one end of the sampling resistor (5); the other ends of the first protection circuit (41) and the second protection circuit (42) away from the negative switch circuit (3) and the other end of the sampling resistor (5) are connected to ground in parallel.

9. An electromagnet bridge control circuit according to claim 8, characterized in that, The protection circuit (41) includes an eighth transistor Q8, a second capacitor C2, and a tenth resistor R10; the collector of the eighth transistor Q8 is connected to the base of the fifth transistor Q5, the base of the eighth transistor Q8 is connected to one end of the tenth resistor R10 and the second capacitor C2 respectively, the other end of the tenth resistor R10 is connected to the emitter of the fifth transistor Q5 and one end of the sampling resistor (5) respectively, and the other end of the emitter of the eighth transistor Q8, the second capacitor C2, and the sampling resistor (5) is connected to ground in parallel.

10. A microwave oven, characterized in that, The microwave oven includes an electromagnet bridge control circuit according to any one of claims 1-9, and the control circuit is disposed inside the microwave oven.

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