Control circuit for heating element with output feedback function and kettle

Abstract

This invention discloses a control circuit for a heating element with an output feedback function and a kettle. [Solution] The control circuit includes a switching power supply circuit, a microcontroller, an input voltage detection circuit, an output current detection circuit, an input zero-crossing signal detection circuit, an output zero-crossing signal detection circuit, a thyristor power output circuit, and a heating element. Under the wide voltage and different frequency input voltages of the world's power grid, the present invention can dynamically adjust the output in real time each time based on feedback such as output active power, output current, and input voltage, ensuring that the heating element operates safely, stably, and efficiently under constant power, preventing safety problems, and meeting the performance requirements of the equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of kettles, and specifically to a control circuit for a heating element with an output feedback function and a kettle.

Background Art

[0002] A kettle usually electrically heats the water inside the kettle using a heating element. However, since the input power supply and frequency vary from country to country, kettles often lack compatibility worldwide. To solve this problem, the currently commercially available kettles are designed with a mechanism that adds a resistor to the power input terminal to detect the input voltage and zero-cross signal, adjust the on / off cycle of the thyristor, and adjust the power. Although this method can realize basic functions, it has serious defects and may cause many problems.

[0003] Specifically, in this conventional solution, a detection circuit is not arranged at the output end, and important parameters such as the effective power, voltage value, and effective current value output cannot be monitored and fed back in real time, and closed-loop control cannot be realized. Therefore, a deviation occurs between the output waveform, power, current value, etc. set at the control end and the actual output value, and in some cases, they may not completely match. In particular, when the power grid is interfered with or the performance of the thyristor changes due to factors such as heat, the microprocessor may incorrectly adjust the on and off of the thyristor to adjust the power, and there is no immediate feedback mechanism at the output end to correct this error. Such a situation not only seriously affects the heating effect of the kettle, but also may cause components such as the heating tube, circuit board, and even the exterior to overheat and be damaged due to long-term abnormal operation. In more serious cases, it may cause safety hazards such as fires. Such accidents are not uncommon in the market, highlighting the drawbacks of existing solutions in terms of stability and security. Therefore, it is very important to optimize and upgrade the control circuit of the kettle, especially to add a monitoring and feedback mechanism at the output end.

Summary of the Invention

[0004] In order to overcome the problem that conventional kettle control circuits do not have an immediate feedback mechanism at the output terminal, making closed-loop control impossible, the present invention provides a control circuit for a heating element and a kettle equipped with an output feedback function.

[0005] The technical solution of the present invention is as follows:

[0006] In a first aspect, the present invention provides a control circuit for a heating element with an output feedback function, comprising a switching power supply circuit, a microcontroller, an input voltage detection circuit, an output current detection circuit, an input zero-crossing signal detection circuit, an output zero-crossing signal detection circuit, a thyristor power output circuit, and a heating element. The aforementioned switching power supply circuit is used to convert the AC input voltage of the input power supply into a DC output voltage. The input voltage detection circuit is used to detect the voltage of the input power supply in real time and output it to the microcontroller. When the input power supply changes or the voltage fluctuates, the microcontroller controls the thyristor power output circuit to adjust the output power. The output current detection circuit detects the operating current in real time and outputs it to the input voltage detection circuit to calculate the active power. The input voltage detection circuit outputs the calculated active power to the microcontroller. The microcontroller adjusts the output power of the thyristor power output circuit according to the currently fed-back active power. The aforementioned input zero-crossing signal detection circuit is used to detect the input zero-crossing signal of the input power supply in real time and output it to the microcontroller. The output zero-crossing signal detection circuit is used to detect the output zero-crossing signal in real time after power output and output it to the microcontroller. The thyristor power output circuit is used to adjust the output power according to the control commands of the microcontroller.

[0007] As a preferred solution of the present invention, the input voltage detection circuit includes resistors R24, R25, R26, R27, R28, R29, R30, capacitor C2, and a measurement chip U3, wherein one end of resistor R24 ​​is connected to the live terminal of the input power supply, and the other end of resistor R24 ​​passes through resistors R25, R26, R27, R28, and R29, and is then connected to one end of resistor R30, one end of capacitor C2, and the fourth pin of the measurement chip U3, respectively, the other end of resistor R30 and the other end of capacitor C2 are both grounded, and the sixth, seventh, and eighth pins of the measurement chip U3 are all connected to the microcontroller.

[0008] As a preferred solution of the present invention, the output current detection circuit includes a sampling resistor R3, a resistor R6, a resistor R9, a capacitor C5, a capacitor C6, a capacitor C9, and an electrolytic capacitor EC1, wherein the input terminal of the sampling resistor R3 is connected to one end of the resistor R6 and the output terminal of the thyristor power output circuit, respectively, and the output terminal of the sampling resistor R3 is connected to one end of the resistor R9, one end of the output zero-cross signal detection circuit, and one end of the heating element, respectively, and the resistor The other end of resistor R6 is connected to one end of capacitor C5 and the second pin of the measurement chip U3, respectively. The other end of resistor R9 is connected to one end of capacitor C9 and the third pin of the measurement chip U3, respectively. The other end of capacitor C5 is connected to the other end of capacitor C9, one end of capacitor C6, and the negative terminal of electrolytic capacitor EC1, respectively. The other end of capacitor C6 is connected to the positive terminal of electrolytic capacitor EC1, the first pin of the measurement chip U3, and the power supply voltage, respectively.

[0009] A preferred solution of the present invention is that the input zero-cross signal detection circuit includes a resistor R11, a resistor R16, a diode D3, and a diode D4, wherein one end of the resistor R11 is connected to the live terminal of the input power supply, the other end of the resistor R11 passes through the resistor R16 and is then connected to the negative terminal of the diode D3, the positive terminal of the diode D4, and the microcontroller, respectively, the positive terminal of the diode D3 is grounded, and the negative terminal of the diode D4 is connected to the power supply voltage.

[0010] As a preferred solution of the present invention, the output zero-cross signal detection circuit includes resistors R36, R37, R38, R39, diode D8, and diode D9, wherein one end of resistor R36 is connected to one end of resistor R38 and the output terminal of the output current detection circuit, respectively, and the other end of resistor R36, after passing through resistor R37, is connected to the positive terminal of diode D8, the negative terminal of diode D9, and the microcontroller, respectively, the negative terminal of diode D8 is connected to the power supply voltage, the positive terminal of diode D9 is grounded, and the other end of resistor R38, after passing through resistor R39, is connected to the live terminal of the input power supply.

[0011] As a preferred solution of the present invention, the thyristor power output circuit includes a triac Q3, a capacitor C8, a resistor R34, a resistor R35, and a resistor R40, wherein the first end of the triac Q3 is connected to one end of the capacitor C8, one end of the resistor R40, and the output terminal of the switching power supply circuit, respectively; the second end of the triac Q3 passes through the resistor R34 and is connected to the other end of the resistor R40 and the microcontroller, respectively; the second end of the triac Q3 is connected to one end of the resistor R35 and the input terminal of the output current detection circuit, respectively; and the other end of the capacitor C8 is connected to the other end of the resistor R35.

[0012] As a preferred solution of the present invention, the switching power supply circuit includes a varistor MOV1, an inductor L2, an electrolytic capacitor EC3, an electrolytic capacitor EC4, and a switching power supply chip U1, wherein one end of the varistor MOV1, the negative terminal of the electrolytic capacitor EC3, the negative terminal of the electrolytic capacitor EC4, and the first, second, third, and fourth pins of the switching power supply chip U1 are all connected to the neutral terminal of the input power supply, the other end of the varistor MOV1, one end of the inductor L2, and the positive terminal of the electrolytic capacitor EC4 are all connected to the live terminal of the input power supply, and the other end of the inductor L2 is connected to the positive terminal of the electrolytic capacitor EC3 and the fifth, sixth, seventh, and eighth pins of the switching power supply chip U1, respectively.

[0013] A preferred solution of the present invention further includes a temperature measurement circuit connected to the microcontroller.

[0014] A preferred solution of the present invention is that the temperature measurement circuit includes a thermistor R10 for detecting the temperature of a thyristor and a thermistor R13 for detecting the water temperature of a kettle, and both thermistor R10 and thermistor R13 are connected to the microcontroller.

[0015] In a second aspect, the present invention provides a kettle including a kettle body, the kettle body being equipped with a control circuit for a heating element having an output feedback function as described in any of the above solutions. [Effects of the Invention]

[0016] Compared to conventional technology, the beneficial effects of the present invention are as follows: 1. The control circuit for a heating element with an output feedback function provided by the present invention can dynamically adjust the output in real time each time based on feedback such as output active power, output current, and input voltage, under the wide voltage and different frequency input voltages of the world's power grid, ensuring that the heating element operates safely, stably, and efficiently under constant power, preventing safety problems, and meeting the performance requirements of the equipment. 2. By installing an input voltage detection circuit, an output current detection circuit, an input zero-crossing signal detection circuit, an output zero-crossing signal detection circuit, and a temperature measurement circuit, the power grid input voltage, effective output active power, effective output current value, input / output zero-crossing signals, thyristor temperature, and water temperature can be simultaneously monitored. This allows for the detection and notification of whether there is a fault in the input power supply and the thyristor power output circuit, and enables timely shutdown, thereby avoiding safety problems such as burnout and fire. 3. By employing a dual zero-crossing circuit (input zero-crossing signal detection circuit, output zero-crossing signal detection circuit), the output result of the current trigger can be accurately detected. [Brief explanation of the drawing]

[0017] To more clearly explain the technical solutions in the embodiments of the present invention, the drawings that may be used in describing the embodiments or the prior art are briefly introduced below. Clearly, the drawings in the following description are only a few embodiments of the present invention, and those skilled in the art can obtain other drawings based on these without any creative effort.

[0018] [Figure 1] Figure 1 is a block diagram of the control circuit of a heating element with an output feedback function in one embodiment of the present invention. [Figure 2] Figure 2 is a schematic diagram of the control circuit of a heating element equipped with an output feedback function in one embodiment of the present invention. [Figure 3] Figure 3 shows the continuity waveform of the power supply output terminal before adjustment in one embodiment of the present invention. [Figure 4]Figure 4 is a conduction waveform diagram of the adjusted power output terminal in an embodiment of the present invention. [Figure 5] Figure 5 is an output waveform diagram of the thyristor power output circuit in an embodiment of the present invention.

Embodiments for Carrying Out the Invention

[0019] In order to more clearly illustrate the technical problems to be solved, technical solutions, and advantageous effects of the present invention, the present invention will be described in more detail below with reference to the drawings and embodiments. It should be noted that in the following figures, the same reference numerals and characters represent the same items. Once an item is defined in a figure, subsequent figures do not require further definition and explanation. At the same time, it is also specified that the embodiments described below are only used to explain the present invention and do not limit the present invention.

[0020] Unless otherwise specified, terms such as "mount", "provide", "connect", and "fix" should be understood in a broad sense. For example, it may be a fixed connection, a removable connection, or an integrated one, a mechanical connection, an electrical connection, a direct connection, an indirect connection through an intermediary, an internal communication between two elements, or an interaction relationship between two elements. The indicated orientation and positional relationship are the orientation and positional relationship shown in the drawings, or the orientation and positional relationship in which the product of the application is usually placed when in use, or the orientation and positional relationship commonly understood by those skilled in the art, or the orientation and positional relationship in which the product of the application is usually placed during use. It is only for the convenience of the description of the present application and the simplification of the description, and is not intended to indicate or imply that the device or element mentioned must have a specific orientation and must be configured and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present application.

[0021] Referring to FIG. 1, this embodiment provides a control circuit for a heating element with an output feedback function, including a switching power supply circuit 1, a microcontroller 2, an input voltage detection circuit 3, an output current detection circuit 4, an input zero-crossing signal detection circuit 5, an output zero-crossing signal detection circuit 6, a thyristor power output circuit 7, and a heating element 8. The switching power supply circuit 1 is connected to an input power supply, the microcontroller 2, and the thyristor power output circuit 7 respectively. The microcontroller 2 is also connected to the input voltage detection circuit 3, the input zero-crossing signal detection circuit 5, the output zero-crossing signal detection circuit 6, and the thyristor power output circuit 7 respectively. The output current detection circuit 4 is connected to the input voltage detection circuit 3, the output zero-crossing signal detection circuit 6, the thyristor power output circuit 7, and the heating element 8 respectively. The input voltage detection circuit 3, the input zero-crossing signal detection circuit 5, and the heating element 8 are also connected to the input power supply.

[0022] The switching power supply circuit 1 is used to convert the AC input voltage of an input power supply (for example, a main power supply) into a smooth DC output voltage (that is, a power supply voltage).

[0023] The input voltage detection circuit 3 is used to detect the voltage of the input power supply in real time and output it to the microcontroller 2. When the input power supply changes rapidly or the voltage fluctuates, the microcontroller 2 controls the thyristor power output circuit to adjust the output power, thereby preventing damage to the heating element 8.

[0024] The output current detection circuit 4 detects the operating current in real time, outputs it to the input voltage detection circuit 3 to calculate the active power, and outputs the calculated active power to the microcontroller 2. The microcontroller 2 adjusts the output power of the thyristor power output circuit 7 according to the currently feedback active power, so that the heating element 8 can maintain a certain heating power under different power supply voltages and frequencies.

[0025] The input zero-crossing signal detection circuit 5 detects the input zero-crossing signal of the input power supply in real time and outputs it to the microcontroller 2. The output zero-crossing signal detection circuit 6 detects the output zero-crossing signal after the power supply has been output in real time and outputs it to the microcontroller 2. The microcontroller 2 can detect and notify whether there is a fault in the power supply input and the thyristor power output circuit 7 through the input zero-crossing signal and the output zero-crossing signal, and can shut down in a timely manner.

[0026] The thyristor power output circuit 7 adjusts the output power by cutting out or discarding waveforms according to the control commands of the microcontroller 2, thereby ensuring that the heating element 8 maintains a constant active power output.

[0027] The microcontroller 2 pre-calculates the thyristor's on-cycle based on the read input power supply voltage and frequency, and generates a zero-crossing pulse corresponding to each zero-crossing moment. The microcontroller 2 then determines the number of trigger pulses in each cycle based on the input power supply voltage and zero-crossing pulse, and generates the corresponding number of trigger pulses in each cycle. The thyristor power output circuit 7 is configured to generate drive signals to control the on or off of the heating element 8 and the power supply based on the trigger pulses generated by the microcontroller 2. Simultaneously, it collects the output active power in each cycle to verify whether it matches the controlled output. If not, the microcontroller 2 readjusts the calculated number of trigger pulses to ensure that the output power is accurate. Thus, the present invention enables the determination of the current input power supply voltage and frequency in a relatively simple manner, the control of heating of the heating element 8 based on the input power supply voltage and frequency, and the adjustment of the output active power according to the output feedback power to achieve closed-loop control. There is no need to add any other power converters.

[0028] Referring to Figure 2, in this embodiment, the microcontroller 2 uses an MCU chip U1 to save costs and facilitate circuit expansion.

[0029] Referring to Figure 2, in this embodiment, the input voltage detection circuit 3 includes resistors R24, R25, R26, R27, R28, R29, R30, capacitor C2, and measurement chip U3. One end of resistor R24 ​​is connected to the live terminal of the input power supply, and the other end of resistor R24 ​​passes through resistors R25, R26, R27, R28, and R29 before being connected to one end of resistor R30, one end of capacitor C2, and the 4th pin of measurement chip U3, respectively. Both the other end of resistor R30 and the other end of capacitor C2 are grounded, and the 6th, 7th, and 8th pins of measurement chip U3 are connected to the 13th, 14th, and 15th pins of MCU chip U1, respectively. The input power supply voltage passes through resistors R24, R25, R26, R27, R28, R29, and R30 and enters pin 4 V2P of the measurement chip U3 for voltage sampling. The MCU chip U1 can obtain the effective output power of the thyristor power output circuit 7 by detecting the signal on pin 6 CF of the measurement chip U3. The MCU chip U1 can obtain the output voltage and effective current value of the thyristor power output circuit 7 by setting pin 8 SEL of the measurement chip U3 and alternately detecting the signal on pin 7 CF1 of the measurement chip U3.

[0030] Referring to Figure 2, in this embodiment, the output current detection circuit 4 includes a sampling resistor R3, resistors R6 and R9, capacitors C5, C6 and C9, and an electrolytic capacitor EC1. The input terminal of the sampling resistor R3 is connected to one end of resistor R6 and the output terminal of the thyristor power output circuit 7, respectively. The output terminal of the sampling resistor R3 is connected to one end of resistor R9, one end of the output zero-cross signal detection circuit 6, and one end of the heating element 8, respectively. The other end of resistor R6 is connected to one end of capacitor C5 and the second pin of the measurement chip U3, respectively. The other end of resistor R9 is connected to one end of capacitor C9 and the third pin of the measurement chip U3, respectively. The other end of capacitor C5 is connected to the other end of capacitor C9, one end of capacitor C6, and the negative terminal of electrolytic capacitor EC1, respectively. The other end of capacitor C6 is connected to the positive terminal of electrolytic capacitor EC1, the first pin of the measurement chip U3, and the power supply voltage, respectively. The sampling resistor R3 should be a manganese copper resistor or a constantan resistor, which offers excellent thermal stability, hardness, and resistance accuracy.

[0031] The output current detection circuit 4 described above employs differential signal sampling to eliminate interference and ensure the accuracy of output current sampling. The input terminal of sampling resistor R3 is filtered by resistor R6 and capacitor C5 before entering the second pin V1P of measurement chip U3, and the output terminal of sampling resistor R3 is filtered by resistor R9 and capacitor C9 before entering the third pin V1N of measurement chip U3. The two paths form a differential input, providing strong interference immunity and enabling accurate measurement of the current value at the power supply output terminal. This allows for accurate calculation of the output active power with an accuracy of less than 0.2%, enabling real-time monitoring of the output power.

[0032] Specifically, before leaving the factory, the voltage, current, and power values ​​of the measurement chip U3 are measured, then calibrated with a measuring instrument, and the deviation values ​​are adjusted so that its active power meets the accuracy requirements of the 50 / 60Hz IEC 687 / 1036 standard. The power accuracy reaches ±0.2%, and the voltage value accuracy reaches ±0.5%, which are used as a reference for adjusting the power. The measured voltage and current values ​​are processed by the DSP in the measurement chip U3, and then the power value is calculated and output to the MCU chip U1.

[0033] The following is the principle of power adjustment using a heating element 8 with a power of 100V and 1000W as an example.

[0034] When the heating element 8 is used at a voltage of 100V, 50Hz, its power is 1000W. When the input power supply voltage becomes 220V, 50Hz, the initial conduction time is first calculated based on the voltage and current values ​​measured by the measurement chip U3, and then the power is adjusted to a constant power according to the active power fed back by the measurement chip U3.

[0035] In this case, if the voltage is 220V and 50Hz, it is necessary to adjust the power by adjusting the conduction time. Assuming the voltage is 220V and 50Hz, the frequency during conduction is fHz.

[0036] JPEG2026082620000002.jpg14170

[0037] The five waveforms are grouped together, with one of the five waveforms turning on, and so on, until the last waveform of the tenth group turns on at 0.33% of the cycle, and the on waveform is shown in Figure 3 below.

[0038] If the pre-calculated power deviates as described above, adjustments will be necessary in the next cycle. Power can be adjusted through multiple stepwise adjustments. For example, a 100V, 1000W heating element 8 is used in a 220V 50Hz power grid, with a target power of 1000W. The active power returned from the measurement chip U3 is 960W, with a deviation of 40W. In this case, the conduction time is adjusted to be longer, and the calculation is as follows. The frequency during the adjusted conduction is f1.

[0039] f1 / 10.33 = 1000 / 960W, f1 = 10.76Hz, and the adjusted waveform is shown in Figure 4 below.

[0040] Referring to Figure 2, in this embodiment, the input zero-cross signal detection circuit 5 includes resistors R11 and R16, diode D3 and D4. One end of resistor R11 is connected to the live terminal of the input power supply, and the other end of resistor R11 passes through resistor R16 and is then connected to the negative terminal of diode D3, the positive terminal of diode D4, and pin 8 of the MCU chip U1, respectively. The positive terminal of diode D3 is grounded, and the negative terminal of diode D4 is connected to the power supply voltage. The input zero-cross signal detection circuit 5 configured as described above has a simple structure and can detect the input zero-cross signal of the input power supply in real time and output it to the MCU chip U1, allowing the MCU chip U1 to detect and notify in real time whether or not there is a fault in the power supply input, thereby improving the safety performance of the circuit.

[0041] Referring to Figure 2, in this embodiment, the output zero-cross signal detection circuit 6 includes resistors R36, R37, R38, R39, diode D8, and diode D9. One end of resistor R36 is connected to one end of resistor R38 and the output terminal of the output current detection circuit 4, respectively. The other end of resistor R36 passes through resistor R37 and is then connected to the positive terminal of diode D8, the negative terminal of diode D9, and the 11th pin of the MCU chip U1, respectively. The negative terminal of diode D8 is connected to the power supply voltage, the positive terminal of diode D9 is grounded, and the other end of resistor R38 passes through resistor R39 and is then connected to the live terminal of the input power supply. The output zero-crossing signal detection circuit 6 configured as described above has a simple structure and is designed to detect the output zero-crossing signal after power output in real time. By outputting this signal to the MCU chip U1, the MCU chip U1 can detect and notify in real time whether or not there is a fault in the thyristor power output circuit 7, and can shut it down in a timely manner, thereby improving the safety performance of the circuit.

[0042] Referring to Figure 2, in this embodiment, the thyristor power output circuit 7 includes a triac Q3, a capacitor C8, a resistor R34, a resistor R35, and a resistor R40. The first terminal of the triac Q3 is connected to one terminal of the capacitor C8, one terminal of the resistor R40, and the output terminal of the switching power supply circuit, respectively. The second terminal of the triac Q3 passes through the resistor R34 and is connected to the other terminal of the resistor R40 and the MCU chip U1, respectively. The second terminal of the triac Q3 is connected to one terminal of the resistor R35 and the input terminal of the output current detection circuit 4, respectively. The other terminal of the capacitor C8 is connected to the other terminal of the resistor R35. The thyristor power output circuit 7 employs the triac Q3 to control the heating element 8 and maintain a constant active power output. At the same time, electromagnetic wave absorption is performed using resistor R35 and capacitor C8 to prevent the voltage across triac Q3 from changing rapidly and causing triac Q3 to conduct uncontrollably, thereby ensuring a safe output, and the output waveform is shown in Figure 5.

[0043] Referring to Figure 2, in this embodiment, the switching power supply circuit 1 includes a varistor MOV1, an inductor L2, an electrolytic capacitor EC3, an electrolytic capacitor EC4, and a switching power supply chip U1. One end of the varistor MOV1, the negative terminal of the electrolytic capacitor EC3, the negative terminal of the electrolytic capacitor EC4, and the first, second, third, and fourth pins of the switching power supply chip U1 are all connected to the neutral terminal of the input power supply. The other end of the varistor MOV1, one end of the inductor L2, and the positive terminal of the electrolytic capacitor EC4 are all connected to the live terminal of the input power supply. The other end of the inductor L2 is connected to the positive terminal of the electrolytic capacitor EC3 and the fifth, sixth, seventh, and eighth pins of the switching power supply chip U1, respectively. By installing the varistor MOV1 at the power supply input terminal, the above switching power supply circuit 1 can effectively prevent damage to the circuit board due to lightning strikes. By arranging the inductor L2, electrolytic capacitor EC3, and electrolytic capacitor EC4 to form a filter circuit, EMC problems can be effectively prevented.

[0044] Referring to Figure 1, in one embodiment, the control circuit of the heating element with output feedback function further includes a temperature measurement circuit 9 connected to the microcontroller 2. The temperature measurement circuit 9 can not only detect the water temperature of the kettle but also further detect the temperature of the triac Q3 in the thyristor power output circuit 7. Through the temperature measurement circuit 9, safety issues can be addressed, such as notifying of an NTC failure and stopping heating, or shutting off the output and notifying of an overheating failure of the triac Q3, thereby safely and stably triggering the output of the triac Q3.

[0045] Referring to Figure 2, the temperature measurement circuit 9 includes a thermistor R10 for detecting the temperature of the triac Q3 and a thermistor R13 for detecting the water temperature of the kettle. One end of thermistor R10 and one end of thermistor R13 are connected to the second and third pins of the MCU chip U1, respectively, and the other end of thermistor R10 and the other end of thermistor R13 are both grounded. Thermistor R10 is used to detect the temperature of the triac, preventing the triac Q3 from overheating and directly conducting without being triggered, thereby avoiding safety problems such as combustion and fire. The kettle heats the water according to the temperature value of thermistor R13 and controls the temperature.

[0046] Specifically, before heating, the circuit detects the temperature of the triac Q3 via thermistor R10, and if it exceeds the set temperature limit, it is forcibly activated and reports a fault. If there is still power remaining before heating is turned on or after heating is turned off, the kettle reports a fault and warns the user.

[0047] As described above, the control circuit for a heating element with an output feedback function provided by the present invention can dynamically adjust the output in real time each time based on feedback such as output active power, output current, and input voltage, under the wide voltage and different frequency input voltages of the world's power grid. This ensures that the heating element 8 operates safely, stably, and efficiently under constant power, preventing safety problems and meeting the performance requirements of the equipment. By installing the input voltage detection circuit 3, output current detection circuit 4, input zero-crossing signal detection circuit 5, output zero-crossing signal detection circuit 6, and temperature measurement circuit 9, the power grid input voltage, active output active power, active output current value, input / output zero-crossing signals, thyristor temperature, and water temperature can be simultaneously monitored, and the input power supply and thyristor power output circuit can be detected and notified of any faults, enabling timely shutdown. By adopting a dual zero-crossing circuit (input zero-crossing signal detection circuit 5, output zero-crossing signal detection circuit 6), the output result of the current trigger can be accurately detected.

[0048] In one embodiment, the present invention provides a kettle including a kettle body, the kettle body being equipped with a control circuit for a heating element having an output feedback function as described in any of the above embodiments. The kettle can adapt to various power supply voltages and frequencies through the control circuit for a heating element with output feedback, and if the rated power of the heating element 8 is determined, a constant heating power is achieved under various voltages by the triggering and conduction of a thyristor.

[0049] Furthermore, the control circuit for the heating element equipped with the output feedback function of the present invention is applicable not only to kettles but also to other products.

[0050] Those skilled in the art will understand that improvements or modifications can be made based on the above description, and that all such improvements and modifications fall within the scope of protection of the appended claims of the present invention.

[0051] The above has provided an illustrative explanation of the patent of the present invention in conjunction with the attached drawings. However, the realization of the patent of the present invention is not limited to the above method. As long as various improvements are made using the method concept and technical solutions of the patent of the present invention, or as long as the concept and technical solutions of the patent of the present invention are applied directly to other situations without improvement, all such improvements fall within the scope of the protection of the present invention.

Claims

1. A control circuit for a heating element with an output feedback function, comprising a switching power supply circuit, a microcontroller, an input voltage detection circuit, an output current detection circuit, an input zero-crossing signal detection circuit, an output zero-crossing signal detection circuit, a thyristor power output circuit, and a heating element, The aforementioned switching power supply circuit is used to convert the AC input voltage of the input power supply into a DC output voltage. The input voltage detection circuit is used to detect the voltage of the input power supply in real time and output it to the microcontroller. When the input power supply changes or the voltage fluctuates, the microcontroller controls the thyristor power output circuit to adjust the output power. The output current detection circuit is used to detect the operating current in real time and output it to the input voltage detection circuit to calculate the active power. The input voltage detection circuit further outputs the calculated active power to the microcontroller, and the microcontroller adjusts the output power of the thyristor power output circuit according to the currently fed-back active power. The aforementioned input zero-crossing signal detection circuit is used to detect the input zero-crossing signal of the input power supply in real time and output it to the microcontroller. The output zero-crossing signal detection circuit is used to detect the output zero-crossing signal in real time after power output and output it to the microcontroller. The control circuit for a heating element, which has an output feedback function, is characterized in that the thyristor power output circuit is used to adjust the output power according to a control command of a microcontroller.

2. The control circuit for a heating element with an output feedback function according to claim 1, characterized in that the input voltage detection circuit includes resistors R24, R25, R26, R27, R28, R29, R30, capacitor C2, and a measuring chip U3, one end of resistor R24 ​​is connected to the live terminal of the input power supply, the other end of resistor R24 ​​passes through resistors R25, R26, R27, R28, and R29, and then connects to one end of resistor R30, one end of capacitor C2, and the fourth pin of measuring chip U3, respectively, the other end of resistor R30 and the other end of capacitor C2 are both grounded, and the sixth, seventh, and eighth pins of measuring chip U3 are all connected to the microcontroller.

3. The output current detection circuit includes a sampling resistor R3, resistors R6 and R9, capacitors C5, C6 and C9, and an electrolytic capacitor EC1. The input terminal of the sampling resistor R3 is connected to one end of the resistor R6 and the output terminal of the thyristor power output circuit, respectively. The output terminal of the sampling resistor R3 is connected to one end of the resistor R9, one end of the output zero-cross signal detection circuit, and one end of the heating element, respectively. The other end of the resistor R6 is connected to one end of the capacitor C5 and the measurement chip. A control circuit for a heating element with an output feedback function as described in claim 2, characterized in that the resistor R9 is connected to the second pin of U3, the other end of the resistor R9 is connected to one end of the capacitor C9 and the third pin of the measurement chip U3, the other end of the capacitor C5 is connected to the other end of the capacitor C9, one end of the capacitor C6, and the negative terminal of the electrolytic capacitor EC1, and the other end of the capacitor C6 is connected to the positive terminal of the electrolytic capacitor EC1, the first pin of the measurement chip U3, and the power supply voltage.

4. The control circuit for a heating element with an output feedback function as described in claim 1, wherein the input zero-crossing signal detection circuit includes a resistor R11, a resistor R16, a diode D3, and a diode D4, one end of the resistor R11 being connected to the live terminal of the input power supply, the other end of the resistor R11 passing through the resistor R16 and then being connected to the negative terminal of the diode D3, the positive terminal of the diode D4, and the microcontroller, respectively, the positive terminal of the diode D3 being grounded, and the negative terminal of the diode D4 being connected to the power supply voltage.

5. The output zero-cross signal detection circuit includes resistors R36, R37, R38, R39, diode D8, and diode D9, wherein one end of resistor R36 is connected to one end of resistor R38 and the output terminal of the output current detection circuit, respectively, and the other end of resistor R36 passes through resistor R37 and is connected to the positive terminal of diode D8, the negative terminal of diode D9, and the microcontroller, respectively, the negative terminal of diode D8 is connected to the power supply voltage, the positive terminal of diode D9 is grounded, and the other end of resistor R38 passes through resistor R39 and is connected to the live terminal of the input power supply, characterized in that the control circuit for a heating element with an output feedback function is as described in claim 1.

6. The control circuit for a heating element with an output feedback function according to claim 1, characterized in that the thyristor power output circuit includes a triac Q3, a capacitor C8, a resistor R34, a resistor R35, and a resistor R40, the first end of the triac Q3 is connected to one end of the capacitor C8, one end of the resistor R40, and the output terminal of the switching power supply circuit, respectively, the second end of the triac Q3 passes through the resistor R34 and is connected to the other end of the resistor R40 and the microcontroller, respectively, the second end of the triac Q3 is connected to one end of the resistor R35 and the input terminal of the output current detection circuit, respectively, and the other end of the capacitor C8 is connected to the other end of the resistor R35.

7. The switching power supply circuit includes a varistor MOV1, an inductor L2, an electrolytic capacitor EC3, an electrolytic capacitor EC4, and a switching power supply chip U1, wherein one end of the varistor MOV1, the negative terminal of the electrolytic capacitor EC3, the negative terminal of the electrolytic capacitor EC4, and the first, second, third, and fourth pins of the switching power supply chip U1 are all connected to the neutral terminal of the input power supply, the other end of the varistor MOV1, one end of the inductor L2, and the positive terminal of the electrolytic capacitor EC4 are all connected to the live terminal of the input power supply, and the other end of the inductor L2 is connected to the positive terminal of the electrolytic capacitor EC3 and the fifth, sixth, seventh, and eighth pins of the switching power supply chip U1, respectively, a control circuit for a heating element with an output feedback function as described in claim 1.

8. The control circuit for a heating element with an output feedback function according to claim 1, further comprising a temperature measurement circuit connected to the microcontroller.

9. The control circuit for a heating element with an output feedback function according to claim 8, characterized in that the temperature measurement circuit includes a thermistor R10 for detecting the temperature of a thyristor and a thermistor R13 for detecting the water temperature of a kettle, and both the thermistor R10 and the thermistor R13 are connected to the microcontroller.

10. A kettle including a kettle body, wherein the kettle body is provided with a control circuit for a heating element having an output feedback function as described in any one of claims 1 to 9.

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