A zero-crossing detection and frequency adaptive control circuit

Abstract

The application discloses a zero-crossing detection and frequency adaptive control circuit, comprising an AC input unit, a switching unit, an optical coupler, a signal amplification unit and a control unit; the AC input unit is used for accessing external AC power; the switching unit is electrically connected with the AC input unit, the control unit and an external load respectively, and is used for controlling the switching on or switching off of the external load; the optical coupler is arranged between the AC input unit and the signal amplification unit, and is used for signal relay transmission; the signal amplification unit is also electrically connected with the control unit, and is used for realizing the amplification processing of the relay transmission signal and sending the amplified signal to the control unit; and the control unit is used for controlling the switching unit according to the received amplified signal. The circuit can realize efficient work at different frequencies, correct the time precision of the timing function, prolong the product life and improve the product safety.

Description

Technical Field

[0001] This utility model relates to the field of timing control technology, and more specifically, to a control circuit for zero-crossing detection and frequency adaptation. Background Technology

[0002] The core function of an oven is to bake food using heating elements. To achieve complex cooking processes (such as segmented temperature control, preheating reminders, and precise timing), modern ovens rely on microcontroller-based electronic control systems. A key component of this system is the power switching element that controls the on / off state of the heating elements, typically using electromagnetic relays or solid-state relays.

[0003] Existing oven products mainly face the following technical challenges in practical use: The mains power standards vary across different regions of the world, primarily ranging from 50Hz to 60Hz. The control circuits of existing ovens often rely on a fixed crystal oscillator clock source for their internal timing. When an oven designed for a 50Hz environment is used with a 60Hz power grid, its internal clock accumulates errors because its software timing fails to synchronize with the actual AC cycle.

[0004] Furthermore, the heating element of an oven is a high-current, resistive load. Most ovens currently use relays to control the heating element, but their switching action is often random. That is, the contacts close at any phase point of the AC current, generating a huge inrush current and a strong electric spark. Long-term, frequent electric spark erosion can severely damage the relay contacts, leading to contact oxidation, increased contact resistance, abnormal heating, and even adhesion. This not only significantly shortens the lifespan of the relay and the entire control board, but is also one of the main causes of oven malfunctions and poses a safety hazard. The strong electric sparks generated by random switching are also a significant source of electromagnetic interference, which may affect the stable operation of the oven's internal microprocessor and other sensitive circuits, causing program errors. Simultaneously, contact adhesion may prevent the oven from disconnecting when power is needed, resulting in the risk of dry burning and a fire hazard.

[0005] Therefore, there is an urgent need for a control scheme for ovens that can adapt to different power grid frequencies and fundamentally eliminate electrical sparks when relays are switched, so as to comprehensively improve the frequency adaptability, timing accuracy, service life and safety of the product. Utility Model Content

[0006] To overcome the technical problems of insufficient frequency adaptability, timing accuracy, service life and safety in the prior art, this utility model provides a control circuit with zero-crossing detection and frequency self-adaptation.

[0007] To solve the above-mentioned technical problems, the technical solution of this utility model is as follows: A zero-crossing detection and frequency adaptive control circuit includes: an AC input unit, a switching unit, an optocoupler, a signal amplification unit, and a control unit; The AC input unit is used to connect to external AC power; The switching unit is electrically connected to the AC input unit, the control unit and the external load respectively, and is used to control the connection or disconnection of the external load; The optocoupler is disposed between the AC input unit and the signal amplification unit for signal relay transmission; The signal amplification unit is also electrically connected to the control unit, and is used to amplify the relay transmission signal and send the amplified signal to the control unit. The control unit is used to control the switching unit based on the received amplified signal.

[0008] Preferably, the switching unit includes: a relay RLY, a third diode D3, and a first power supply; The first terminal of the relay RLY is connected to the anode of the third diode D3 and serves as the first input terminal of the switching unit; the fourth terminal of the relay RLY is connected to the cathode of the third diode D3 and serves as the second input terminal of the switching unit; the second terminal of the relay RLY serves as the first output terminal of the switching unit; the third terminal of the relay RLY serves as the second output terminal of the switching unit. The first input terminal of the switching unit is connected to the output terminal of the control unit; the second input terminal of the switching unit is connected to the first power supply; the first output terminal of the switching unit is connected to the external load; and the second output terminal of the switching unit is connected to the input terminal of the AC input unit.

[0009] Preferably, the AC input unit includes: a first resistor R1, a second resistor R2, a third resistor R3, a first diode D1, and a second diode D2; The first terminal of the first resistor R1 serves as the first input terminal of the AC input unit; the anode of the second diode D2 is connected to the first terminal of the third resistor R3 and serves as the second input terminal of the AC input unit; the second terminal of the first resistor R1 is connected to the first terminal of the second resistor R2; the second terminal of the second resistor R2 is connected to the anode of the first diode D1; the cathode of the first diode D1 is connected to the cathode of the second diode D2 and the second terminal of the third resistor R3 and serves as the first output terminal of the AC input unit; the first terminal of the third resistor R3 serves as the second output terminal of the AC input unit. The first input terminal of the AC input unit is connected to the first input port ACL of the external AC power and is connected to the second output terminal of the switch unit; the second input terminal of the AC input unit is connected to the second input port ACN of the external AC power; the first output terminal and the second output terminal of the AC input unit are respectively connected to the input terminal of the optocoupler.

[0010] Preferably, the optical coupler has A as its first input terminal, K as its second input terminal, E as its first output terminal, and C as its second output terminal. The first and second input terminals of the optocoupler are respectively connected to the first and second output terminals of the AC input unit; the first and second output terminals of the optocoupler are respectively connected to the input terminal of the signal amplification unit.

[0011] Preferably, the signal amplification unit includes: a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a second capacitor C2, a transistor T, and a second power supply; The second terminal of the fifth resistor R5 is connected to the first terminal of the second capacitor C2, the first terminal of the sixth resistor R6, and the base of the transistor T; the second terminals of the second capacitor C2, the sixth resistor R6, and the emitter of the transistor T are all grounded; the first terminal of the fifth resistor R5 serves as the first input terminal of the signal amplification unit; the first terminal of the fourth resistor R4 is connected to the second power supply and serves as the second input terminal of the signal amplification unit; the second terminal of the fourth resistor R4 is connected to the collector of the transistor T and serves as the output terminal of the signal amplification unit. The first and second input terminals of the signal amplification unit are respectively connected to the first and second output terminals of the optocoupler; the output terminal of the signal amplification unit is connected to the input terminal of the control unit.

[0012] Preferably, the control unit includes: a microcontroller, a first capacitor C1, and a third power supply; The seventh terminal of the microcontroller and the first terminal of the first capacitor C1 are both grounded; the eighth terminal of the microcontroller is connected to the first capacitor C1 and the third power supply; the first terminal of the microcontroller serves as the input terminal of the control unit; the second terminal of the microcontroller serves as the output terminal of the control unit; all other ports of the microcontroller are left empty. The input terminal of the control unit is connected to the output terminal of the signal amplification unit; the output terminal of the control unit is connected to the first input terminal of the switching unit.

[0013] Preferably, the first power supply, the second power supply, and the third power supply are all 5V DC power supplies.

[0014] Preferably, the first resistor R1 and the second resistor R2 both have a resistance of 56KΩ; the third resistor R3 has a resistance of 1MΩ; the fourth resistor R4 has a resistance of 3.3KΩ; the fifth resistor R5 has a resistance of 10KΩ; and the sixth resistor has a resistance of 22KΩ.

[0015] Preferably, the microcontroller is model BF7412AM20-SJLX; the optocoupler is model EL817C; and the relay RLY is model 1-1393194-9.

[0016] Preferably, the first diode D1 is a rectifier diode; the second diode D2 and the third diode D3 are switching diodes.

[0017] Compared with the prior art, the beneficial effects of this utility model's technical solution are: This invention combines five modules—an AC input unit, a switch unit, an optocoupler, a signal amplification unit, and a control unit—in a coordinated manner. Based on hardware, it can detect the mains frequency; with software support, the circuit can operate efficiently at different frequencies. This application corrects the timing accuracy of the timing function, achieving synchronization with the mains clock and millisecond-level precision. Furthermore, by detecting 0V AC power, the microcontroller controls the connection or disconnection of external loads based on the detection result, thus avoiding electrical sparks that may occur when manually switching switches, extending the lifespan of the relay and the product, and improving product safety. Attached Figure Description

[0018] Figure 1 This is a structural framework diagram of a zero-crossing detection and frequency adaptive control circuit in Example 1; Figure 2 This is a circuit diagram of a zero-crossing detection and frequency adaptive control circuit in Example 2. Detailed Implementation

[0019] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the scope of this application. To better illustrate this embodiment, some parts in the accompanying drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions; It will be understood by those skilled in the art that certain well-known structures and their descriptions may be omitted in the accompanying drawings.

[0020] The technical solution of this utility model will be further described below with reference to the accompanying drawings and embodiments.

[0021] Example 1 A zero-crossing detection and frequency adaptive control circuit, the structural framework diagram of which is shown below. Figure 1As shown, it includes: an AC input unit, a switching unit, an optocoupler, a signal amplification unit, and a control unit; The AC input unit is used to connect to external AC power; The switching unit is electrically connected to the AC input unit, the control unit and the external load respectively, and is used to control the connection or disconnection of the external load; The optocoupler is disposed between the AC input unit and the signal amplification unit for signal relay transmission; The signal amplification unit is also electrically connected to the control unit, and is used to amplify the relay transmission signal and send the amplified signal to the control unit. The control unit is used to control the switching unit based on the received amplified signal.

[0022] In the specific implementation process, the AC input unit is connected to external AC power, and after processing by the AC input unit, it is input to the optocoupler. The optocoupler performs relay processing on the signal and periodically outputs a DC signal. The DC signal is amplified by the signal amplification unit and transmitted to the control unit for judgment. The control unit realizes frequency detection and timing based on the judgment result, or controls the connection or disconnection of the external load.

[0023] Example 2 A zero-crossing detection and frequency adaptive control circuit includes: an AC input unit, a switching unit, an optocoupler, a signal amplification unit, and a control unit; The AC input unit is used to connect to external AC power; The switching unit is electrically connected to the AC input unit, the control unit and the external load respectively, and is used to control the connection or disconnection of the external load; The optocoupler is disposed between the AC input unit and the signal amplification unit for signal relay transmission; The signal amplification unit is also electrically connected to the control unit, and is used to amplify the relay transmission signal and send the amplified signal to the control unit. The control unit is used to control the switching unit based on the received amplified signal.

[0024] The switching unit includes: a relay RLY, a third diode D3, and a first power supply; The first terminal of the relay RLY is connected to the anode of the third diode D3 and serves as the first input terminal of the switching unit; the fourth terminal of the relay RLY is connected to the cathode of the third diode D3 and serves as the second input terminal of the switching unit; the second terminal of the relay RLY serves as the first output terminal of the switching unit; the third terminal of the relay RLY serves as the second output terminal of the switching unit. The first input terminal of the switching unit is connected to the output terminal of the control unit; the second input terminal of the switching unit is connected to the first power supply; the first output terminal of the switching unit is connected to the external load; and the second output terminal of the switching unit is connected to the input terminal of the AC input unit.

[0025] The AC input unit includes: a first resistor R1, a second resistor R2, a third resistor R3, a first diode D1, and a second diode D2; The first terminal of the first resistor R1 serves as the first input terminal of the AC input unit; the anode of the second diode D2 is connected to the first terminal of the third resistor R3 and serves as the second input terminal of the AC input unit; the second terminal of the first resistor R1 is connected to the first terminal of the second resistor R2; the second terminal of the second resistor R2 is connected to the anode of the first diode D1; the cathode of the first diode D1 is connected to the cathode of the second diode D2 and the second terminal of the third resistor R3 and serves as the first output terminal of the AC input unit; the first terminal of the third resistor R3 serves as the second output terminal of the AC input unit. The first input terminal of the AC input unit is connected to the first input port ACL of the external AC power and is connected to the second output terminal of the switch unit; the second input terminal of the AC input unit is connected to the second input port ACN of the external AC power; the first output terminal and the second output terminal of the AC input unit are respectively connected to the input terminal of the optocoupler.

[0026] The optocoupler has A terminal as its first input terminal, K terminal as its second input terminal, E terminal as its first output terminal, and C terminal as its second output terminal. The first and second input terminals of the optocoupler are respectively connected to the first and second output terminals of the AC input unit; the first and second output terminals of the optocoupler are respectively connected to the input terminal of the signal amplification unit.

[0027] The signal amplification unit includes: a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a second capacitor C2, a transistor T, and a second power supply. The second terminal of the fifth resistor R5 is connected to the first terminal of the second capacitor C2, the first terminal of the sixth resistor R6, and the base of the transistor T; the second terminals of the second capacitor C2, the sixth resistor R6, and the emitter of the transistor T are all grounded; the first terminal of the fifth resistor R5 serves as the first input terminal of the signal amplification unit; the first terminal of the fourth resistor R4 is connected to the second power supply and serves as the second input terminal of the signal amplification unit; the second terminal of the fourth resistor R4 is connected to the collector of the transistor T and serves as the output terminal of the signal amplification unit. The first and second input terminals of the signal amplification unit are respectively connected to the first and second output terminals of the optocoupler; the output terminal of the signal amplification unit is connected to the input terminal of the control unit.

[0028] The control unit includes: a microcontroller, a first capacitor C1, and a third power supply; The seventh terminal of the microcontroller and the first terminal of the first capacitor C1 are both grounded; the eighth terminal of the microcontroller is connected to the first capacitor C1 and the third power supply; the first terminal of the microcontroller serves as the input terminal of the control unit; the second terminal of the microcontroller serves as the output terminal of the control unit; all other ports of the microcontroller are left empty. The input terminal of the control unit is connected to the output terminal of the signal amplification unit; the output terminal of the control unit is connected to the first input terminal of the switching unit.

[0029] The first power supply, the second power supply, and the third power supply are all 5V DC power supplies.

[0030] The first resistor R1 and the second resistor R2 both have a resistance of 56KΩ; the third resistor R3 has a resistance of 1MΩ; the fourth resistor R4 has a resistance of 3.3KΩ; the fifth resistor R5 has a resistance of 10KΩ; and the sixth resistor has a resistance of 22KΩ.

[0031] The microcontroller is model BF7412AM20-SJLX; the optocoupler is model EL817C; and the relay RLY is model 1-1393194-9.

[0032] The first diode D1 is a rectifier diode; the second diode D2 and the third diode D3 are switching diodes.

[0033] In the specific implementation process, the circuit structure diagram is as follows: Figure 2 As shown, after the external AC power is connected to the circuit, it is first divided by the first resistor R1 and the second resistor R2, then protected by the first diode D1 and the second diode D2, and then transmitted to the optocoupler for processing. The optocoupler periodically outputs a DC signal. The DC signal is amplified by the signal amplification circuit composed of the fifth resistor R5, the sixth resistor R6, and the transistor T, and then transmitted to the microcontroller for judgment and processing. The microcontroller, based on the amplified DC signal and in conjunction with the software program, realizes frequency detection and timing functions, or realizes control of the relay, thereby controlling the connection or disconnection of the external load when the external AC power is 0V, avoiding electrical sparks when the external load is connected or disconnected, and improving the product's lifespan and safety.

[0034] The same or similar labels correspond to the same or similar parts; The terms used to describe positional relationships in the accompanying drawings are for illustrative purposes only and should not be construed as limiting this application. Obviously, the above embodiments of this utility model are merely examples for clearly illustrating this utility model, and are not intended to limit the implementation of this utility model. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this utility model should be included within the protection scope of the claims of this utility model.

Claims

1. A control circuit for zero-crossing detection and frequency adaptation, characterized in that, include: AC input unit, switching unit, optocoupler, signal amplification unit, control unit; The AC input unit is used to connect to external AC power; The switching unit is electrically connected to the AC input unit, the control unit and the external load respectively, and is used to control the connection or disconnection of the external load; The optocoupler is disposed between the AC input unit and the signal amplification unit for signal relay transmission; The signal amplification unit is also electrically connected to the control unit, and is used to amplify the relay transmission signal and send the amplified signal to the control unit. The control unit is used to control the switching unit based on the received amplified signal.

2. The zero-crossing detection and frequency adaptive control circuit according to claim 1, characterized in that, The switching unit includes: a relay RLY, a third diode D3, and a first power supply; The first terminal of the relay RLY is connected to the anode of the third diode D3 and serves as the first input terminal of the switching unit; the fourth terminal of the relay RLY is connected to the cathode of the third diode D3 and serves as the second input terminal of the switching unit; the second terminal of the relay RLY serves as the first output terminal of the switching unit; and the third terminal of the relay RLY serves as the second output terminal of the switching unit. The first input terminal of the switching unit is connected to the output terminal of the control unit; the second input terminal of the switching unit is connected to the first power supply; the first output terminal of the switching unit is connected to an external load; and the second output terminal of the switching unit is connected to the input terminal of the AC input unit.

3. The zero-crossing detection and frequency adaptive control circuit according to claim 2, characterized in that, The AC input unit includes: a first resistor R1, a second resistor R2, a third resistor R3, a first diode D1, and a second diode D2; The first terminal of the first resistor R1 serves as the first input terminal of the AC input unit; the anode of the second diode D2 is connected to the first terminal of the third resistor R3 and serves as the second input terminal of the AC input unit; the second terminal of the first resistor R1 is connected to the first terminal of the second resistor R2; the second terminal of the second resistor R2 is connected to the anode of the first diode D1; the cathode of the first diode D1 is connected to the cathode of the second diode D2 and the second terminal of the third resistor R3 and serves as the first output terminal of the AC input unit; the first terminal of the third resistor R3 serves as the second output terminal of the AC input unit. The first input terminal of the AC input unit is connected to the first input port ACL of the external AC power and is connected to the second output terminal of the switch unit; the second input terminal of the AC input unit is connected to the second input port ACN of the external AC power; the first output terminal and the second output terminal of the AC input unit are respectively connected to the input terminal of the optocoupler.

4. The zero-crossing detection and frequency adaptive control circuit according to claim 3, characterized in that, The optocoupler has A terminal as its first input terminal, K terminal as its second input terminal, E terminal as its first output terminal, and C terminal as its second output terminal. The first and second input terminals of the optocoupler are respectively connected to the first and second output terminals of the AC input unit; the first and second output terminals of the optocoupler are respectively connected to the input terminal of the signal amplification unit.

5. The zero-crossing detection and frequency adaptive control circuit according to claim 4, characterized in that, The signal amplification unit includes: a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a second capacitor C2, a transistor T, and a second power supply. The second terminal of the fifth resistor R5 is connected to the first terminal of the second capacitor C2, the first terminal of the sixth resistor R6, and the base of the transistor T; the second terminals of the second capacitor C2, the sixth resistor R6, and the emitter of the transistor T are all grounded; the first terminal of the fifth resistor R5 serves as the first input terminal of the signal amplification unit; the first terminal of the fourth resistor R4 is connected to the second power supply and serves as the second input terminal of the signal amplification unit; the second terminal of the fourth resistor R4 is connected to the collector of the transistor T and serves as the output terminal of the signal amplification unit. The first and second input terminals of the signal amplification unit are respectively connected to the first and second output terminals of the optocoupler; the output terminal of the signal amplification unit is connected to the input terminal of the control unit.

6. The zero-crossing detection and frequency adaptive control circuit according to claim 5, characterized in that, The control unit includes: a microcontroller, a first capacitor C1, and a third power supply; The seventh terminal of the microcontroller and the first terminal of the first capacitor C1 are both grounded; the eighth terminal of the microcontroller is connected to the first capacitor C1 and the third power supply; the first terminal of the microcontroller serves as the input terminal of the control unit; the second terminal of the microcontroller serves as the output terminal of the control unit; all other ports of the microcontroller are left empty. The input terminal of the control unit is connected to the output terminal of the signal amplification unit; the output terminal of the control unit is connected to the first input terminal of the switching unit.

7. The zero-crossing detection and frequency adaptive control circuit according to claim 6, characterized in that, The first power supply, the second power supply, and the third power supply are all 5V DC power supplies.

8. The zero-crossing detection and frequency adaptive control circuit according to claim 7, characterized in that, The first resistor R1 and the second resistor R2 both have a resistance of 56KΩ; the third resistor R3 has a resistance of 1MΩ; the fourth resistor R4 has a resistance of 3.3KΩ; the fifth resistor R5 has a resistance of 10KΩ; and the sixth resistor R6 has a resistance of 22KΩ.

9. The zero-crossing detection and frequency adaptive control circuit according to claim 8, characterized in that, The microcontroller is model BF7412AM20-SJLX; the optocoupler is model EL817C; and the relay RLY is model 1-1393194-9.

10. The zero-crossing detection and frequency adaptive control circuit according to claim 9, characterized in that, The first diode D1 is a rectifier diode; the second diode D2 and the third diode D3 are switching diodes.

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