Electromagnetic heating device, cooking appliance and heating control method

Abstract

The application discloses an electromagnetic heating device, a cooking utensil and a heating control method. The electromagnetic heating device comprises a rectification filtering module, a zero-crossing detection module, a control module, a driving module and a heating inverter module. The rectification filtering module is used for rectifying and filtering an alternating power supply and supplying the heating inverter module. The zero-crossing detection module is used for detecting a voltage zero-crossing signal of the alternating power supply. The driving module is used for driving the heating inverter module to work. The inverter heating module comprises a power switch tube and a resonant heating unit, and the power switch tube controls the resonant heating unit to work in resonance. In the electromagnetic heating device, on the basis of using a large-capacity capacitor in the rectification filtering module, the conduction time of the power switch tube is increased in the time interval near the zero-crossing point of the commercial power, so that the grid current is closer to a sine in the time interval of the zero-crossing point of the commercial power, the distortion is eliminated or reduced, and the electromagnetic compatibility of the electromagnetic cooker is avoided from being affected by the EMC current harmonic exceeding the standard.

Description

Technical Field

[0001] This application relates to the field of household appliance technology, and in particular to an electromagnetic heating device, cooking appliance, and heating control method. Background Technology

[0002] An induction cooker is an electric cooking appliance that uses the principle of electromagnetic induction heating. It generates an alternating magnetic field through a high-frequency induction heating coil (i.e., an excitation coil), which induces eddy currents in a metal pot placed on the cooktop, thus heating the food. Induction cookers are widely used due to their advantages such as high efficiency and energy saving, ease of control, and wide applicability.

[0003] Currently, as people's demands for the heating performance of induction cookers increase, the requirements for a wide power range are also increasing. The maximum power range for household induction cookers is required to be 50W-7400W. With the expansion of the power of induction cookers, electromagnetic compatibility (EMC) issues are becoming increasingly prominent.

[0004] In related technologies, to increase the differential mode suppression capability of induction cookers, the capacitance of the differential mode filter in the induction cooker can be increased, that is, a large-capacity capacitor is used in the differential mode filter. However, when the induction cooker is heating at low power, the mains zero voltage cannot be reduced to a lower voltage or 0V, causing the mains current to be distorted in the time domain at the mains zero voltage, resulting in excessive EMC current harmonics. Summary of the Invention

[0005] This application aims to address at least one of the technical problems existing in the prior art. To this end, this application provides an electromagnetic heating device, a cooking appliance, and a heating control method.

[0006] The electromagnetic heating device according to this application includes a rectification and filtering module, a zero-crossing detection module, a control module, a drive module, and a heating inverter module. The rectification and filtering module is connected to an AC power supply and the heating inverter module, and is used to rectify and filter the AC power supply before supplying it to the heating inverter module. The zero-crossing detection module is connected to the AC power supply and is used to detect the zero-crossing signal of the AC power supply. The drive module is connected to the heating inverter module and is used to drive the heating inverter module to operate. The inverter heating module includes a power switch and a resonant heating unit. The control electrode of the power switch is connected to the drive module, and the power switch controls the resonant heating unit to resonate. The control module is connected to the drive module and the zero-crossing detection module. When the control module determines that the voltage of the AC power supply is within the zero-crossing range based on the zero-crossing signal, it controls the drive module to output a first drive voltage to drive the power switch to operate. The control module is further configured to, when it is determined from the voltage zero-crossing signal that the voltage of the AC power supply is outside the zero-crossing interval, control the drive module to output a second drive voltage to drive the power switch to operate, wherein the amplitude of the first drive voltage is equal to the amplitude of the second drive voltage, and the pulse width of the first drive voltage is greater than the pulse width of the second drive voltage.

[0007] In some implementations, the duration of the zero-crossing interval ranges from 0.5 to 10 milliseconds.

[0008] In some embodiments, the control module controls the drive module to output a first drive voltage at a fixed frequency or a variable frequency to drive the power switch to work, with the drive frequency ranging from 20,000 to 40,000 Hz.

[0009] In some embodiments, the control module controls the drive module to output a first drive voltage via frequency conversion, and the zero-crossing interval includes a start point, a zero-crossing point, and an end point. When the voltage of the AC power supply is determined to be within the interval from the start point to the zero-crossing point based on the voltage zero-crossing signal, the pulse width of the first drive voltage increases. When the voltage of the AC power supply is determined to be within the interval from the zero-crossing point to the end point based on the voltage zero-crossing signal, the pulse width of the first drive voltage decreases.

[0010] In some implementations, at the zero-crossing point of the AC power supply, the collector voltage of the power switch oscillates to a minimum.

[0011] In some embodiments, both the drive module and the heating inverter module include multiple modules, with each drive module used to drive one heating inverter module to operate.

[0012] In some embodiments, the rectifier-filter module includes a filter unit, a rectifier unit, and a differential-mode filter connected in sequence. The filter unit is connected to the AC power supply and is used to filter out noise interference in the AC power supply. The rectifier unit is connected to the filter unit and is used to rectify the AC power supply to output DC power. The differential-mode filter is connected to both the rectifier unit and the inverter-heating module and is used to filter out noise interference in the DC power supply and provide it to the inverter-heating module.

[0013] In some embodiments, the electromagnetic heating device further includes a voltage detection module, a power supply module, and a current detection module. The voltage detection module is connected to the AC power supply and the control module, and is used to detect the voltage of the AC power supply and provide it to the control module. The power supply module is connected to the AC power supply and the control module, and is used to supply power to the control module. The current detection module is connected to the rectifier unit, and is used to detect the current of the DC power supply.

[0014] This application also provides a cooking appliance, which includes an electromagnetic heating device that implements any one of the above embodiments.

[0015] This application also provides a heating control method for an electromagnetic heating device. The electromagnetic heating device includes a driving module, a heating inverter module, and a zero-crossing detection module. The driving module is used to drive the heating inverter module to operate. The heating inverter module includes a resonant heating unit and a power switch for controlling the resonant heating unit to operate resonantly. The heating control method includes: upon receiving a low-power heating command, detecting a zero-crossing signal of the AC power supply input to the electromagnetic heating device through the zero-crossing detection module; if the voltage of the AC power supply is determined to be within the zero-crossing interval based on the voltage zero-crossing signal, controlling the driving module to output a first driving voltage to drive the power switch to operate; if the voltage of the AC power supply is determined to be outside the zero-crossing interval based on the voltage zero-crossing signal, controlling the driving module to output a second driving voltage to drive the power switch to operate, wherein the amplitude of the first driving voltage is equal to the amplitude of the second driving voltage, and the pulse width of the first driving voltage is greater than the pulse width of the second driving voltage.

[0016] In some implementations, the duration of the zero-crossing interval ranges from 0.5 to 10 milliseconds.

[0017] In some embodiments, the control module controls the drive module to output a first drive voltage at a fixed frequency or a variable frequency to drive the power switch to work, with the drive frequency ranging from 20,000 to 40,000 Hz.

[0018] In some embodiments, the control module controls the drive module to output a first drive voltage via frequency conversion, and the zero-crossing interval includes a start point, a zero-crossing point, and an end point. When the voltage of the AC power supply is determined to be within the interval from the start point to the zero-crossing point based on the voltage zero-crossing signal, the pulse width of the first drive voltage increases. When the voltage of the AC power supply is determined to be within the interval from the zero-crossing point to the end point based on the voltage zero-crossing signal, the pulse width of the first drive voltage decreases.

[0019] In some implementations, at the zero-crossing point of the AC power supply, the collector voltage of the power switch oscillates to a minimum.

[0020] In the electromagnetic heating device, cooking appliance, and heating control method of this application, based on the use of a large-capacity capacitor in the rectifier filter module, the conduction time of the power switching transistor is increased during the time interval near the zero-crossing point of the mains power. This makes the mains current closer to a sinusoidal signal during the zero-crossing period, eliminating or reducing distortion and preventing excessive EMC current harmonics from affecting the electromagnetic compatibility of the cooking appliance.

[0021] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0022] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, wherein:

[0023] Figure 1 This is a schematic diagram of the structure of the electromagnetic heating device according to an embodiment of this application;

[0024] Figure 2 This is a schematic diagram showing the changes over time of the AC power supply voltage, zero-volt detection input signal, zero-volt detection signal, power switch power, and resonant voltage waveforms in an embodiment of this application.

[0025] Main component reference numerals:

[0026] Electromagnetic heating device 100, rectifier and filter module 10, filter unit 11, rectifier unit 12, differential mode filter 13, zero-crossing detection module 20, control module 30, drive module 40, heating inverter module 50, AC power supply 60, voltage detection module 70, power supply module 80, and current detection module 90. Detailed Implementation

[0027] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0028] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0029] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0030] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0031] The following disclosure provides many different embodiments or examples for implementing different structures of this application. To simplify the disclosure, specific examples of components and arrangements are described below. Of course, these are merely examples and are not intended to limit the scope of this application. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, various specific examples of processes and materials are provided in this application, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0032] Currently, as people's demands for the heating performance of induction cookers increase, the requirements for a wide power range are also increasing. The maximum power range for household induction cookers is required to be 50W-7400W. With the expansion of the power of induction cookers, electromagnetic compatibility (EMC) issues are becoming increasingly prominent.

[0033] Electromagnetic compatibility (EMC) focuses on ensuring that electronic devices, when operating in an electromagnetic environment, do not generate unacceptable electromagnetic interference to other devices, nor are they subject to electromagnetic interference from other devices. Distortions in the mains current generate additional harmonic components; if these harmonic components exceed certain standards, they are considered EMC problems. Therefore, when the mains current distorts at the moment of zero voltage, it may lead to excessive EMC current harmonics, thus affecting the EMC of the induction cooker.

[0034] In related technologies, in order to increase the differential mode suppression capability of induction cookers, the capacitance of the differential mode filter in the induction cooker can be increased, that is, the differential mode filter uses a large-capacity capacitor.

[0035] When an induction cooker operates at a low power (e.g., 50W), its internal circuitry and components require precise control of current and voltage to maintain this low power output. In the waveform of alternating current (AC), there are moments when the voltage is zero, known as the zero-voltage moment. These moments occur at the intersections of a sine wave, where the voltage is theoretically zero. However, due to factors such as the charging and discharging effects of the large capacitors in the differential-mode filter, the actual voltage at the zero-voltage moment cannot drop to near or completely zero as theoretically possible when the induction cooker is heating at low power. Because the voltage cannot drop low enough, when the induction cooker attempts to maintain a stable current output at low power, the mains current may become distorted at the zero-voltage moment. This distortion manifests as the current waveform no longer being a smooth sine wave, but instead exhibiting uneven or abrupt sections.

[0036] In view of this, please refer to Figure 1 and Figure 2This application provides an electromagnetic heating device 100, which includes a rectifier and filter module 10, a zero-crossing detection module 20, a control module 30, a drive module 40, and a heating inverter module 50.

[0037] The rectifier and filter module 10 connects to the AC power supply 60 and the heating inverter module 50, and is used to rectify and filter the AC power supply 60 before supplying it to the heating inverter module 50. The zero-crossing detection module 20 connects to the AC power supply 60 and is used to detect the zero-crossing signal of the AC power supply 60. The drive module 40 connects to the heating inverter module 50 and is used to drive the heating inverter module 50 to operate. The heating inverter module 50 includes a power switch and a resonant heating unit. The control electrode of the power switch is connected to the drive module 40, and the power switch controls the resonant heating unit to operate resonantly.

[0038] The control module 30 is connected to the drive module 40 and the zero-crossing detection module 20. When the control module 30 determines that the voltage of the AC power supply 60 is within the zero-crossing range based on the voltage zero-crossing signal, it controls the drive module 40 to output a first drive voltage to drive the power switch. The control module 30 is also used to control the drive module 40 to output a second drive voltage to drive the power switch when the voltage of the AC power supply 60 is outside the zero-crossing range based on the voltage zero-crossing signal. The amplitude of the first drive voltage is equal to the amplitude of the second drive voltage, and the pulse width of the first drive voltage is greater than the pulse width of the second drive voltage.

[0039] In the electromagnetic heating device 100 of this application, based on the use of a large-capacity capacitor in the rectifier filter module 10, the conduction time of the power switch is increased during the time T1 interval near the zero-crossing point of the mains power. This makes the mains current closer to a sine wave during the zero-crossing point interval, eliminating or reducing distortion and preventing excessive EMC current harmonics from affecting the electromagnetic compatibility of the induction cooker.

[0040] Specifically, the rectifier-filter module 10 includes a filter unit 11, a rectifier unit 12, and a differential-mode filter 13 connected in sequence. The filter unit 11 is connected to the AC power supply 60 and is used to filter out noise interference in the AC power supply 60. The rectifier unit 12 is connected to the filter unit 11 and is used to rectify the AC power supply 60 to output DC power. The differential-mode filter 13 is connected to both the rectifier unit 12 and the heating inverter module 50, and is used to filter out noise interference in the DC power and provide it to the heating inverter module 50.

[0041] The differential-mode filter 13 includes components such as capacitors and inductors. In this embodiment, the differential-mode filter 13 uses a large-capacity capacitor; for example, a capacitor with a capacitance of 5 microfarads is commonly used, while this application uses a capacitor with a capacitance of 7-8 microfarads to enhance the differential-mode filtering and suppression effect. The main function of the differential-mode filter 13 is to filter out differential-mode interference in the DC output of the rectifier unit 12. Differential-mode interference refers to interference existing between signal lines or between power lines, which may be caused by ripple generated during rectification, internal switching noise, or other factors. The differential-mode filter 13 attenuates or eliminates differential-mode interference signals through a filtering network composed of inductors, capacitors, and other components, thereby providing a clean and stable DC power supply to the heating inverter module 50. This not only protects the heating inverter module 50 from interference but also improves the electromagnetic compatibility of the entire system.

[0042] In summary, the rectifier-filter module 10, through the coordinated operation of the filter unit 11, the rectifier unit 12, and the differential mode filter 13, converts the AC power supply 60 into a stable and clean DC power supply, providing reliable power support for the subsequent heating inverter module 50.

[0043] The zero-crossing detection module 20 monitors the voltage waveform of the AC power supply 60 in real time and accurately captures the signal at the zero-crossing point of the voltage. Its output signal is transmitted to the control module 30 to determine whether the current voltage is in the zero-crossing range.

[0044] The heating inverter module 50 includes a power switching transistor and a resonant heating unit. The power switching transistor can be an insulated-gate bipolar transistor (IGBT). The power switching transistor rapidly switches according to the signal from the drive module 40, inverting DC power into high-frequency AC power to supply the resonant heating unit. The resonant heating unit uses the high-frequency AC power to generate an electromagnetic field, inducing eddy currents inside the object being heated through electromagnetic induction, thereby achieving rapid heating.

[0045] Based on the signal provided by the zero-crossing detection module 20, the control module 30 intelligently adjusts the control strategy for the drive module 40 to optimize heating efficiency and reduce harmonic pollution. When the voltage is detected to be within the zero-crossing range, the control module 30 outputs a first drive voltage through the drive module 40. When the voltage is outside the zero-crossing range, a second drive voltage is output. The pulse width of the first drive voltage is larger than that of the second drive voltage, which is beneficial for the power switch to complete its switching action during periods of relatively smooth voltage change, reducing switching losses. The pulse width of the second drive voltage is smaller than that of the first drive voltage, which is beneficial for adapting to environments with rapid voltage changes while maintaining heating efficiency. The amplitudes of the two drive voltages are the same, and by adjusting the pulse width, the control module 30 can flexibly control the heating power and efficiency.

[0046] The drive module 40 receives the signal from the control module 30 and generates a corresponding drive voltage to drive the power switch in the heating inverter module 50.

[0047] Please see Figure 2 In some implementations, the duration of the zero-crossing interval ranges from 0.5 to 10 milliseconds.

[0048] Specifically, the duration of the zero-crossing interval is the time period during which the AC power supply voltage waveform transitions from the positive half-cycle to the negative half-cycle or from the negative half-cycle to the positive half-cycle, passing through zero. The duration of the zero-crossing interval can be, for example, 0.5 milliseconds, 1 millisecond, 2 milliseconds, 3 milliseconds, 4 milliseconds, 5 milliseconds, 6 milliseconds, 7 milliseconds, 8 milliseconds, 9 milliseconds, or 10 milliseconds.

[0049] A short zero-crossing interval increases the difficulty of control. Due to the reduced time window, the system requires higher precision and faster response speed to accurately capture the zero-crossing point and execute the corresponding control strategy. This may place higher demands on hardware and software design. In practical applications, noise and interference in the power system can affect the accuracy of the zero-crossing signal. If the zero-crossing interval is too short, the presence of noise and interference may lead to misjudgment or missed zero-crossing points, thereby affecting the stability and reliability of the system.

[0050] An excessively long zero-crossing interval can slow down the system response. In applications requiring rapid response, a long zero-crossing interval can delay the generation and execution of control signals, impacting overall system performance. A long zero-crossing interval can also increase current waveform distortion. In an AC power supply system, if the zero-crossing interval is not precisely controlled, the current may fluctuate significantly near the zero point, increasing harmonic content and reducing power quality.

[0051] In conclusion, setting the zero-crossing interval to a range of 0.5-10 milliseconds is a relatively reasonable choice. This range takes into account the impact of factors such as system response speed and current waveform distortion, while also considering the requirements of control difficulty, signal interference, and practical application needs.

[0052] In some embodiments, the control module 30 controls the drive module 40 to output a first drive voltage at a fixed frequency or a variable frequency to drive the power switching transistor to work, with the drive frequency ranging from 20,000 to 40,000 Hz.

[0053] Specifically, IGBT drivers can be configured as fixed-frequency or variable-frequency drives. Fixed-frequency drives are simpler but may lack flexibility, while variable-frequency drives offer greater flexibility and response speed. A driving frequency of 20kHz ≤ f ≤ 40kHz ensures good switching performance while reducing high-frequency noise and switching losses.

[0054] During the zero-crossing interval, variable frequency drive (VFD) is preferred, while a mirror-symmetric VFD is used at the zero-crossing point itself. Using a mirror-symmetric VFD involves gradually increasing the frequency to the zero-crossing point and then gradually decreasing it to a preset time interval. To maintain stable low-power output during the zero-crossing interval, the voltage decreases first and then increases, while the corresponding current increases first and then decreases. The mirror-symmetric VFD strategy at the zero-crossing point further optimizes the current waveform. This means that before the zero-crossing point, the drive frequency gradually increases to help boost the current; after the zero-crossing point, it gradually decreases to match the natural downward trend of the current. This strategy significantly improves the sinusoidal nature of the grid current, reduces harmonic content, and enhances the overall system performance.

[0055] Please see Figure 2 In some embodiments, the control module 30 controls the drive module 40 to output a first drive voltage via frequency conversion. The zero-crossing interval includes a starting point, a zero-crossing point, and an ending point. When the voltage of the AC power supply 60 is determined to be within the interval from the starting point to the zero-crossing point based on the voltage zero-crossing signal, the pulse width of the first drive voltage increases. When the voltage of the AC power supply 60 is determined to be within the interval from the zero-crossing point to the ending point based on the voltage zero-crossing signal, the pulse width of the first drive voltage decreases.

[0056] The zero-crossing interval includes the starting point, the zero-crossing point, and the ending point. If the AC power supply voltage waveform of 60V passes through zero voltage during the transition from the positive half-cycle to the negative half-cycle, then the starting point of the positive half-cycle is the starting point, and the ending point of the negative half-cycle is the ending point. If the AC power supply voltage waveform of 60V passes through zero voltage during the transition from the negative half-cycle to the positive half-cycle, then the starting point of the negative half-cycle is the starting point, and the ending point of the positive half-cycle is the ending point. The zero-crossing point is the moment when the AC power supply voltage of 60V is zero.

[0057] The pulse width directly determines the conduction time of power devices (such as IGBTs) per unit time, thus affecting the output power. A longer pulse width results in a longer conduction time for the power device and a higher output power; conversely, a shorter pulse width results in a lower output power. In the control strategy of the electromagnetic heating device 100, the control module 30 further optimizes the heating process and reduces electromagnetic interference by precisely controlling the frequency conversion output of the drive module 40, particularly by dynamically adjusting the pulse width of the first drive voltage within the zero-crossing interval.

[0058] Specifically, when the control module 30 determines that the voltage of the AC power supply 60 is within the range from the starting point to the zero-crossing point based on the zero-crossing signal, it controls the pulse width of the first driving voltage output by the drive module 40 to gradually increase. The purpose of this is to gradually increase the conduction time of the power switch as the voltage gradually approaches zero, which can compensate for the natural changes in current, so as to smoothly transition to the next state and reduce electromagnetic noise and harmonic pollution caused by voltage jumps.

[0059] Conversely, as the voltage gradually rises from the zero-crossing point, i.e., within the interval between the zero-crossing point and the termination point, the control module 30 controls the pulse width of the first driving voltage to gradually decrease. This is done to quickly adjust the duty cycle of the power switch when the voltage begins to rise, in order to adapt to rapid voltage changes and maintain stable heating efficiency.

[0060] In this way, the control module 30 can achieve precise control of the heating process, ensuring that the working state of the heating inverter module 50 can smoothly transition when the voltage is near zero crossing, reducing electromagnetic interference and harmonic exceedance problems that may be caused by voltage sudden changes.

[0061] Furthermore, this variable frequency output control strategy can be adjusted and optimized according to specific heating requirements and electromagnetic compatibility requirements. For example, the optimal pulse width variation curve, as well as the specific positions of the start point, zero-crossing point, and end point, can be determined through experiments and simulation analysis to achieve the best heating effect and electromagnetic compatibility.

[0062] In summary, the control module 30 controls the drive module 40 to output the first drive voltage via frequency conversion and dynamically adjusts the pulse width within the zero-crossing interval, which is an effective method to optimize the performance and electromagnetic compatibility of the electromagnetic heating device 100.

[0063] In some implementations, at the zero-crossing point of the AC power supply 60, the collector voltage of the power switch oscillates to a minimum.

[0064] Specifically, when the voltage of AC power supply 60 is at the zero-crossing point, the driving voltage output by the driving module 40 to the power switch is adjusted to 0 based on the zero-crossing signal of AC power supply 60, so that the power switch is in the off state and the collector voltage of the power switch oscillates to the minimum.

[0065] Near the zero-crossing point of AC power supply 60, voltage oscillations may occur due to the interaction of components such as inductors and capacitors in the circuit. By turning off the power switch at the zero-crossing point, the interaction between these components can be reduced, thereby helping to reduce or eliminate voltage oscillations. By precisely controlling the state of the power switch at the zero-crossing point of AC power supply 60, the stability and reliability of the entire system can be improved. This helps to reduce failures and damage caused by voltage fluctuations or transient processes.

[0066] Please see Figure 1 In some embodiments, both the drive module 40 and the heating inverter module 50 include multiple modules, with each drive module 40 used to drive one heating inverter module 50 to work.

[0067] Specifically, the electromagnetic heating device 100 can be, for example, an induction cooker, where multiple foods may be heated simultaneously in the kitchen. The design employing multiple drive modules 40 and corresponding heating inverter modules 50 improves the system's flexibility, reliability, and efficiency. Parameters such as heating power, heating area, and heating time can be adjusted according to actual needs to adapt to different application scenarios and process requirements.

[0068] Even if one or more of the heating inverter modules 50 fail, the other modules can still operate normally, thereby improving the overall system reliability. Furthermore, the independent drive module 40 can also perform fault detection and isolation functions, further reducing the impact of faults on the entire system.

[0069] Please see Figure 1 In some embodiments, the electromagnetic heating device 100 further includes a voltage detection module 70, a power supply module 80, and a current detection module 90. The voltage detection module 70 is connected to the AC power supply 60 and the control module 30, and is used to detect the voltage of the AC power supply 60 and supply it to the control module 30. The power supply module 80 is connected to the AC power supply 60 and the control module 30, and is used to supply power to the control module 30. The current detection module 90 is connected to the rectifier unit 12, and is used to detect the DC current.

[0070] Specifically, the voltage detection module 70 is connected to the AC power supply 60 and the control module 30. The main function of this module is to detect the voltage of the AC power supply 60 in real time and provide the detected voltage value to the control module 30. Based on the voltage value, the control module 30 can determine the current state of the power grid, such as whether the voltage is stable or within the normal range, and thus make corresponding control decisions. For example, when the voltage is too high or too low, the control module 30 can adjust the heating power or take other protective measures to prevent equipment damage or safety accidents.

[0071] The power supply module 80 connects the AC power supply 60 and the control module 30. The power supply module 80 is responsible for providing a stable operating power supply to the control module 30. Since the control module 30 contains various electronic components and sensitive devices such as microprocessors, they require a stable and reliable power supply to ensure their normal operation. The power supply module 80 processes the AC power supply 60 through rectification, filtering, and voltage regulation circuits to convert it into a DC power supply suitable for the control module 30, ensuring the stability of its voltage and current.

[0072] The current detection module 90 is connected to the rectifier unit 12. This module is used to detect the current of the DC output from the rectifier unit 12. By detecting the current value in real time, the control module 30 can understand the current load and operating status of the heating system. For example, if the current is too high, it may mean that the heating load is too heavy or there is a fault such as a short circuit. At this time, the control module 30 can quickly cut off the power supply or adjust the heating power to prevent equipment damage or safety accidents. At the same time, the current detection module 90 can also provide feedback signals to the control module 30 to realize closed-loop control and improve the stability and accuracy of the heating system.

[0073] In summary, the voltage detection module 70, power supply module 80, and current detection module 90 each play important roles in the magnetic heating device. They work together to ensure the stable operation and efficient heating of the entire system. By monitoring parameters such as voltage and current in real time, the control module 30 can make accurate control decisions, protecting equipment safety and improving heating efficiency.

[0074] This application also provides a cooking appliance, which includes an electromagnetic heating device 100 that implements any of the above embodiments. Specifically, the structure of the electromagnetic heating device 100 is as described above and will not be repeated here.

[0075] In the cooking appliance of this application, based on the use of a large-capacity capacitor in the rectifier and filter module 10 of the electromagnetic heating device 100, the conduction time of the power switching transistor is increased during the time interval near the zero-crossing point of the mains power. This makes the mains current closer to a sine wave during the zero-crossing point of the mains power, eliminating or reducing distortion and avoiding excessive EMC current harmonics that could affect the electromagnetic compatibility of the cooking appliance.

[0076] This application also provides a heating control method for an electromagnetic heating device 100. The electromagnetic heating device 100 includes a control module 30, a drive module 40, a heating inverter module 50, and a zero-crossing detection module 20. The drive module 40 is used to drive the heating inverter module 50 to operate. The heating inverter module 50 includes a resonant heating unit and a power switch for controlling the resonant heating unit to operate resonantly.

[0077] Heating control methods include:

[0078] 01. Upon receiving a low-power heating command, the zero-crossing signal of the AC power supply 60 input to the electromagnetic heating device 100 is detected by the zero-crossing detection module 20.

[0079] 02. When the voltage of AC power supply 60 is determined to be within the zero-crossing range based on the voltage zero-crossing signal, the first driving voltage is output by controlling the drive module 40 to drive the power switching transistor to work.

[0080] 03. When it is determined from the zero-crossing signal that the voltage of AC power supply 60 is outside the zero-crossing range, the second driving voltage is output by controlling the drive module 40 to drive the power switching transistor to work.

[0081] In this design, the amplitude of the first driving voltage is equal to that of the second driving voltage, and the pulse width of the first driving voltage is greater than that of the second driving voltage. The larger pulse width of the first driving voltage compared to the second driving voltage allows the power switching transistor to complete its switching action during periods of relatively stable voltage change, reducing switching losses. The smaller pulse width of the second driving voltage compared to the first driving voltage helps adapt to environments with rapid voltage changes while maintaining heating efficiency. Since both driving voltages have the same amplitude, the control module 30 can flexibly control the heating power and efficiency by adjusting the pulse width.

[0082] Step 01 is implemented by the zero-crossing detection module 20, which continuously monitors the voltage waveform of the AC power supply 60 input to the electromagnetic heating device 100. When the voltage of the AC power supply 60 approaches zero (i.e., zero-crossing point), the zero-crossing detection module 20 generates a voltage zero-crossing signal.

[0083] Steps 02 and 03 are implemented by the control module 30. Based on the voltage zero-crossing signal, the control module 30 determines whether the voltage of the current AC power supply 60 is within the zero-crossing range, thereby deciding whether to control the drive module 40 to output the first drive voltage or the second drive voltage.

[0084] The heating control method of the electromagnetic heating device 100 is an intelligent control method based on voltage zero-crossing detection. This method achieves effective control of the power switching transistors in the heating inverter module 50 by precisely controlling the driving voltage output by the driving module 40, optimizing the electromagnetic heating process, reducing the generation of current harmonics, and thus avoiding electromagnetic interference.

[0085] In some implementations, the duration of the zero-crossing interval ranges from 0.5 to 10 milliseconds.

[0086] Specifically, the duration of the zero-crossing interval is the time period during which the AC power supply voltage waveform transitions from the positive half-cycle to the negative half-cycle or from the negative half-cycle to the positive half-cycle, passing through zero. The duration of the zero-crossing interval can be, for example, 0.5 milliseconds, 1 millisecond, 2 milliseconds, 3 milliseconds, 4 milliseconds, 5 milliseconds, 6 milliseconds, 7 milliseconds, 8 milliseconds, 9 milliseconds, or 10 milliseconds.

[0087] A short zero-crossing interval increases the difficulty of control. Due to the reduced time window, the system requires higher precision and faster response speed to accurately capture the zero-crossing point and execute the corresponding control strategy. This may place higher demands on hardware and software design. In practical applications, noise and interference in the power system can affect the accuracy of the zero-crossing signal. If the zero-crossing interval is too short, the presence of noise and interference may lead to misjudgment or missed zero-crossing points, thereby affecting the stability and reliability of the system.

[0088] An excessively long zero-crossing interval can slow down the system response. In applications requiring rapid response, a long zero-crossing interval can delay the generation and execution of control signals, impacting overall system performance. A long zero-crossing interval can also increase current waveform distortion. In an AC power supply system, if the zero-crossing interval is not precisely controlled, the current may fluctuate significantly near the zero point, increasing harmonic content and reducing power quality.

[0089] In conclusion, setting the zero-crossing interval to a range of 0.5-10 milliseconds is a relatively reasonable choice. This range takes into account the impact of factors such as system response speed and current waveform distortion, while also considering the requirements of control difficulty, signal interference, and practical application needs.

[0090] In some embodiments, the control module 30 controls the drive module 40 to output a first drive voltage at a fixed frequency or a variable frequency to drive the power switching transistor to work, with the drive frequency ranging from 20,000 to 40,000 Hz.

[0091] Specifically, the power switch driver can be configured as a fixed-frequency driver or a variable-frequency driver. Fixed-frequency driving is simple but may lack flexibility, while variable-frequency driving offers greater flexibility and response speed. The driving frequency is 20kHz≤f≤40kHz, a range that ensures good switching performance while reducing high-frequency noise and switching losses.

[0092] During the zero-crossing interval, variable frequency drive (VFD) is preferred, while a mirror-symmetric VFD is used at the zero-crossing point itself. Using a mirror-symmetric VFD involves gradually increasing the frequency to the zero-crossing point and then gradually decreasing it to a preset time interval. To maintain stable low-power output during the zero-crossing interval, the voltage decreases first and then increases, while the corresponding current increases first and then decreases. The mirror-symmetric VFD strategy at the zero-crossing point further optimizes the current waveform. This means that before the zero-crossing point, the drive frequency gradually increases to help boost the current; after the zero-crossing point, it gradually decreases to match the natural downward trend of the current. This strategy significantly improves the sinusoidal nature of the grid current, reduces harmonic content, and enhances the overall system performance.

[0093] In some embodiments, the control module 30 controls the drive module 40 to output a first drive voltage via frequency conversion. The zero-crossing interval includes a start point, a zero-crossing point, and an end point. When the voltage of the AC power supply 60 is determined to be within the interval from the start point to the zero-crossing point based on the voltage zero-crossing signal, the pulse width of the first drive voltage increases. When the voltage of the AC power supply 60 is determined to be within the interval from the zero-crossing point to the end point based on the voltage zero-crossing signal, the pulse width of the first drive voltage decreases.

[0094] Specifically, the pulse width directly determines the conduction time of power devices (such as IGBTs) per unit time, thus affecting the output power. A longer pulse width results in a longer conduction time for the power device and a higher output power; conversely, a shorter pulse width results in a lower output power. In the control strategy of the electromagnetic heating device 100, the control module 30 further optimizes the heating process and reduces electromagnetic interference by precisely controlling the frequency conversion output of the drive module 40, particularly by dynamically adjusting the pulse width of the first drive voltage within the zero-crossing interval.

[0095] Specifically, when the control module 30 determines that the voltage of the AC power supply 60 is within the range from the starting point to the zero-crossing point based on the zero-crossing signal, it controls the pulse width of the first driving voltage output by the drive module 40 to gradually increase. The purpose of this is to gradually increase the conduction time of the power switch as the voltage gradually approaches zero, which can compensate for the natural changes in current, so as to smoothly transition to the next state and reduce electromagnetic noise and harmonic pollution caused by voltage jumps.

[0096] Conversely, as the voltage gradually rises from the zero-crossing point, i.e., within the interval between the zero-crossing point and the termination point, the control module 30 controls the pulse width of the first driving voltage to gradually decrease. This is done to quickly adjust the duty cycle of the power switch when the voltage begins to rise, in order to adapt to rapid voltage changes and maintain stable heating efficiency.

[0097] In this way, the control module 30 can achieve precise control of the heating process, ensuring that the working state of the heating inverter module 50 can smoothly transition when the voltage is near zero crossing, reducing electromagnetic interference and harmonic exceedance problems that may be caused by voltage sudden changes.

[0098] In some implementations, at the zero-crossing point of the AC power supply 60, the collector voltage of the power switch oscillates to a minimum.

[0099] Specifically, when the voltage of AC power supply 60 is at the zero-crossing point, based on the zero-crossing signal of AC power supply 60, the driving voltage output by drive module 40 to power switch is adjusted to 0, so that power switch is in the off state and the collector voltage of power switch oscillates to the minimum.

[0100] Near the zero-crossing point of AC power supply 60, voltage oscillations may occur due to the interaction of components such as inductors and capacitors in the circuit. By turning off the power switch at the zero-crossing point, the interaction between these components can be reduced, thereby helping to reduce or eliminate voltage oscillations. By precisely controlling the state of the power switch at the zero-crossing point of AC power supply 60, the stability and reliability of the entire system can be improved. This helps to reduce failures and damage caused by voltage fluctuations or transient processes.

[0101] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with the described embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0102] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. An electromagnetic heating device, characterized in that, The electromagnetic heating device includes a rectifier and filter module, a zero-crossing detection module, a control module, a drive module, and a heating inverter module; The rectifier and filter module is connected to the AC power supply and the heating inverter module, and is used to rectify and filter the AC power supply before supplying it to the heating inverter module. The zero-crossing detection module is connected to the AC power supply and is used to detect the zero-crossing signal of the AC power supply. The drive module is connected to the heating inverter module and is used to drive the heating inverter module to work; The inverter heating module includes a power switch and a resonant heating unit. The control electrode of the power switch is connected to the drive module, and the power switch controls the resonant heating unit to resonate. The control module connects the drive module and the zero-crossing detection module, and the control module is used for: If the voltage of the AC power supply is determined to be within the zero-crossing range based on the zero-crossing signal, the first driving voltage is output by controlling the driving module to drive the power switching transistor to work. as well as When it is determined from the zero-crossing signal that the voltage of the AC power supply is outside the zero-crossing range, the driving module is controlled to output a second driving voltage to drive the power switch to work. The amplitude of the first driving voltage is equal to the amplitude of the second driving voltage, and the pulse width of the first driving voltage is greater than the pulse width of the second driving voltage.

2. The electromagnetic heating device according to claim 1, characterized in that, The duration of the zero-crossing interval ranges from 0.5 to 10 milliseconds.

3. The electromagnetic heating device according to claim 2, characterized in that, The control module controls the drive module to output a first drive voltage at a fixed frequency or a variable frequency to drive the power switching transistor to work, with the drive frequency ranging from 20000 to 40000 Hz.

4. The electromagnetic heating device according to claim 3, characterized in that, The control module controls the drive module to output a first drive voltage via frequency conversion, and the zero-crossing interval includes a starting point, a zero-crossing point, and an ending point; Based on the voltage zero-crossing signal, the voltage of the AC power supply is determined to be within the range from the starting point to the zero-crossing point, and the pulse width of the first driving voltage increases. Based on the voltage zero-crossing signal, the voltage of the AC power supply is determined to be within the range from the zero-crossing point to the termination point, and the pulse width of the first driving voltage decreases.

5. The electromagnetic heating device according to claim 1, characterized in that, At the zero-crossing point of the AC power supply, the collector voltage of the power switch oscillates to a minimum.

6. The electromagnetic heating device according to claim 1, characterized in that, Both the drive module and the heating inverter module include multiple modules, and each drive module is used to drive one heating inverter module to work.

7. The electromagnetic heating device according to claim 1, characterized in that, The rectifier-filter module includes a filter unit, a rectifier unit, and a differential-mode filter connected in sequence. The filtering unit is connected to the AC power supply and is used to filter out noise interference in the AC power supply. The rectifier unit is connected to the filter unit and is used to rectify the AC power supply and output DC power. The differential mode filter is connected to the rectifier unit and the inverter heating module respectively, and is used to filter out the noise interference of the DC power and provide it to the inverter heating module.

8. The electromagnetic heating device according to claim 7, characterized in that, The electromagnetic heating device also includes: A voltage detection module is connected to the AC power supply and the control module, and is used to detect the voltage of the AC power supply and provide it to the control module; A power module, which is connected to the AC power source and the control module, is used to supply power to the control module; A current detection module, connected to the rectifier unit, is used to detect the current of the DC power supply.

9. A cooking utensil, characterized in that, Includes the electromagnetic heating device according to any one of claims 1-8.

10. A heating control method for an electromagnetic heating device, characterized in that, The electromagnetic heating device includes a drive module, a heating inverter module, and a zero-crossing detection module. The drive module drives the heating inverter module to operate. The heating inverter module includes a resonant heating unit and a power switch for controlling the resonant heating unit to operate resonantly. The heating control method includes: Upon receiving a low-power heating command, the zero-crossing detection module detects the zero-crossing signal of the AC power supply input to the electromagnetic heating device. If, based on the zero-crossing signal, the voltage of the AC power supply is determined to be within the zero-crossing range, the drive module is controlled to output a first drive voltage to drive the power switch transistor to operate; and When it is determined from the zero-crossing signal that the voltage of the AC power supply is outside the zero-crossing range, the driving module is controlled to output a second driving voltage to drive the power switch to work. The amplitude of the first driving voltage is equal to the amplitude of the second driving voltage, and the pulse width of the first driving voltage is greater than the pulse width of the second driving voltage.

11. The heating control method according to claim 10, characterized in that, The duration of the zero-crossing interval ranges from 0.5 to 10 milliseconds.

12. The heating control method according to claim 11, characterized in that, The control module controls the drive module to output a first drive voltage at a fixed frequency or a variable frequency to drive the power switching transistor to work, with the drive frequency ranging from 20000 to 40000 Hz.

13. The heating control method according to claim 12, characterized in that, The control module controls the drive module to output a first drive voltage via frequency conversion, and the zero-crossing interval includes a starting point, a zero-crossing point, and an ending point; Based on the voltage zero-crossing signal, the voltage of the AC power supply is determined to be within the range from the starting point to the zero-crossing point, and the pulse width of the first driving voltage increases. Based on the voltage zero-crossing signal, the voltage of the AC power supply is determined to be within the range from the zero-crossing point to the termination point, and the pulse width of the first driving voltage decreases.

14. The heating control method according to claim 10, characterized in that, At the zero-crossing point of the AC power supply, the collector voltage of the power switch oscillates to a minimum.

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