Conduction control method and control device of power switch tube and electromagnetic heating equipment

Abstract

The invention discloses a conduction control method and device of a power switch tube and electromagnetic heating equipment, and relates to the technical field of electrical appliances, and the conduction control method of the power switch tube comprises the steps: firstly obtaining a voltage resonance slope when a resonance circuit works; determining a preset resonance voltage value according to the voltage resonance slope; and the delay time of the power switch tube is adjusted according to the determined preset resonance voltage value, and the power switch tube is controlled to be conducted in a delayed manner according to the delay time, so that the power switch tube is conducted when the resonance voltage of the resonance circuit is at the preset resonance voltage value. The invention aims to reduce the conduction loss of the power switch tube, thereby reducing the risk of overheating or damage of the power switch tube, and prolonging the service life of the electromagnetic heating equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of electrical appliances, and particularly to a method for controlling the conduction of a power switch tube, a control device, and an electromagnetic heating device. Background Art

[0002] The core working principle of an electromagnetic heating device is to generate eddy current heating through electromagnetic induction, and its power switch device plays a crucial role. The working state of the power switch device directly affects the efficiency and reliability of the induction cooker. The conduction moment of the power switch device is usually determined by the comparison signal between the bus voltage (i.e., the DC voltage after rectifying and filtering the input AC voltage) and the voltage of the power switch device, and is triggered to conduct after a certain delay time to ensure that it conducts at the optimal moment, so as to achieve zero voltage switching (ZVS), reduce the conduction loss, and reduce heat generation. However, at present, the delay time used by most electromagnetic heating devices on the market to control the conduction moment of the power switch device is a fixed value set at the factory. Due to the difference in the resonance period of the LC resonance circuit under different load conditions, the fixed delay time may cause the phenomenon that the power switch device conducts in advance under high voltage or heavy load conditions, resulting in a large conduction loss, and then causing the power switch tube to overheat or even be damaged, affecting the service life of the electromagnetic heating device. Summary of the Invention

[0003] The main object of the present invention is to propose a method for controlling the conduction of a power switch tube, a control device, and an electromagnetic heating device, aiming to reduce the conduction loss of the power switch tube, thereby reducing the risk of overheating or damage of the power switch tube, and extending the service life of the electromagnetic heating device.

[0004] To achieve the above object, the present invention proposes a method for controlling the conduction of a power switch tube, which is applied to an electromagnetic heating device. The electromagnetic heating device includes a power switch tube and a resonance circuit, and the switch tube is electrically connected to the resonance circuit. The method for controlling the conduction of the power switch tube includes: Obtaining the voltage resonance slope when the resonance circuit is working; Determining a preset resonance voltage value according to the voltage resonance slope; Adjusting the delay time of the power switch tube according to the determined preset resonance voltage value, and controlling the power switch tube to conduct with a delay according to the delay time, so as to conduct when the resonance voltage of the resonance circuit is at the preset resonance voltage value.

[0005] In an embodiment, the obtaining the voltage resonance slope when the resonance circuit is working specifically includes: Obtaining the resonance voltages at at least three different moments; Perform a non - linear fitting on the resonant voltage and time based on the resonant voltages at at least three different moments to obtain a fitting curve of resonant voltage - time; Determine the voltage resonant slope according to the fitting curve of resonant voltage - time.

[0006] In one embodiment, the determining the voltage resonant slope according to the fitting curve of resonant voltage - time specifically includes: Determine the derivatives of a preset number of resonant voltages on the fitting curve of resonant voltage - time according to the fitting curve of resonant voltage - time, and determine the derivatives as the voltage resonant slope.

[0007] In one embodiment, the voltage resonant slope at least includes a first voltage resonant slope and a second voltage resonant slope. The determining the preset resonant voltage value according to the voltage resonant slope specifically includes: Determine the difference between the first voltage resonant slope and the second voltage resonant slope; When the difference is less than or equal to a preset slope difference, determine the preset resonant voltage value.

[0008] In one embodiment, the method for controlling the conduction of the power switch tube further includes: When the difference is less than or equal to the preset slope difference, determine that the change trend of the voltage resonant slope is in a stable stage, and determine the estimated delay time according to the voltage resonant slope in the stable stage.

[0009] In one embodiment, the adjusting the delay time of the power switch tube specifically includes: Increase or decrease the preset delay time to the estimated delay time according to the estimated delay time to adjust the delay time of the power switch tube.

[0010] The present invention also proposes a control device, which includes a memory, a processor, and a conduction control program of a power switch tube stored on the memory and operable on the processor. The conduction control program of the power switch tube is configured to implement the steps of the method for controlling the conduction of the power switch tube described in any one of the above.

[0011] The present invention also proposes an electromagnetic heating device, which includes the above - described control device.

[0012] In one embodiment, the electromagnetic heating device further includes: A power input terminal for connecting to a power supply voltage; A rectifier - filter circuit, the input end of which is connected to the power input terminal, for rectifying and filtering the power supply voltage and then outputting; A power switch tube, with the first end of the power switch tube interconnected to the ground terminal and the output terminal of the rectifying and filtering circuit; A drive circuit, with the drive circuit connected to the controlled terminal of the power switch tube; A resonant circuit, with the first end of the resonant circuit connected to the second end of the power switch tube, and the second end of the resonant circuit connected to the output terminal of the rectifying and filtering circuit; A resonant slope detection module, connected to the second end of the power switch tube, for detecting the voltage resonant slope when the resonant circuit is operating; A delay calculation module, connected to the output terminal of the resonant slope detection module, for determining a preset resonant voltage value according to the voltage resonant slope, and for adjusting the delay time of the power switch tube according to the determined preset resonant voltage value; A control circuit, respectively connected to the drive circuit and the delay calculation module, for controlling the drive circuit to drive the power switch tube to conduct with a delay according to the delay time, so as to conduct when the resonant voltage of the resonant circuit is at the preset resonant voltage value.

[0013] In practical applications, a preset resonant voltage value is determined according to the obtained voltage resonant slope, the delay time of the power switch tube is adjusted according to the preset resonant voltage value, and the power switch tube is controlled to conduct with a delay according to the delay time. In this way, it is realized that the electromagnetic heating device can dynamically adjust the conduction moment of the IGBT under different load conditions, ensuring that it conducts each time when the resonant voltage of the resonant circuit is at the preset resonant voltage value (for example, when the resonant voltage is close to 0V or equal to 0V), reducing the conduction loss of the power switch tube, thereby reducing the risk of overheating or damage of the power switch tube, prolonging the service life of the electromagnetic heating device, and improving the user experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following-described drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on the structures shown in these drawings without creative efforts.

[0015] Figure 1 It is a schematic flowchart of an embodiment of the method for controlling the conduction of the power switch tube of the present invention; Figure 2 It is a schematic flowchart of another embodiment of the method for controlling the conduction of the power switch tube of the present invention; Figure 3 It is a schematic flowchart of another embodiment of the method for controlling the conduction of the power switch tube of the present invention; Figure 4 Schematic diagram of a module of an electromagnetic heating device according to an embodiment of the present invention; Figure 5 Schematic diagram of a module of another embodiment of the electromagnetic heating device according to the present invention; Figure 6 Waveform diagram of the resonant voltage varying with time and schematic diagram of the square wave signal for controlling the on / off of the IGBT.

[0016] Explanation of the reference numerals in the drawings: 10. Power input terminal; 20. Rectifier and filter circuit; 30. Power switch tube; 40. Drive circuit; 50. Resonant circuit; 60. Resonant slope detection module; 70. Delay calculation module; 80. Control circuit.

[0017] The realization, functional features and advantages of the object of the present invention will be further described with reference to the embodiments and the accompanying drawings. Specific embodiments

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0019] It should be noted that in this article, step codes such as S100 and S200 are used. The purpose is to more clearly and briefly express the corresponding content and do not constitute a substantial limitation in sequence. Those skilled in the art may execute S200 first and then S100 during specific implementation, etc., but these should all be within the protection scope of this application.

[0020] The core working principle of electromagnetic heating equipment is to generate eddy current heating through electromagnetic induction, and its power switch device plays a crucial role. The working state of the power switch device directly affects the efficiency and reliability of the induction cooker. The conduction moment of the power switch device is usually determined by the comparison signal between the bus voltage (i.e., the DC voltage after rectifying and filtering the input AC voltage) and the voltage of the power switch device, and it is triggered to conduct after a certain delay time to ensure that it conducts at the optimal moment, thereby achieving zero voltage switching (ZVS), reducing conduction loss and heat generation. However, currently, the delay time used by most electromagnetic heating equipment on the market to control the conduction moment of the power switch device is a fixed value set at the factory. Due to the differences in the resonance periods of the LC resonance circuits under different load conditions, the fixed delay time may cause the power switch device to conduct in advance under high voltage or heavy load conditions, resulting in large conduction losses, and further leading to overheating or even damage of the power switch tube 30, affecting the service life of the electromagnetic heating equipment.

[0021] Therefore, referring to Figure 1 , the present invention proposes a conduction control method for the power switch tube 30, which is applied to electromagnetic heating equipment. The electromagnetic heating equipment includes a power switch tube 30 and a resonance circuit 50. The switch tube is electrically connected to the resonance circuit 50. The conduction control method for the power switch tube 30 includes: Step S100, obtaining the voltage resonance slope when the resonance circuit 50 works; Step S200, determining a preset resonance voltage value according to the voltage resonance slope; Step S300, adjusting the delay time of the power switch tube 30 according to the determined preset resonance voltage value, and controlling the power switch tube 30 to conduct with a delay according to the delay time, so as to conduct when the resonance voltage of the resonance circuit 50 is at the preset resonance voltage value.

[0022] In this embodiment, the conduction control method of the power switch tube 30 of the present invention can be applied to the control device of the electromagnetic heating equipment. The control device includes a memory, a processor, and a conduction control program of the power switch tube 30 stored on the memory and operable on the processor. The conduction control program of the power switch tube 30 is configured to implement the steps of the conduction control method of the power switch tube 30. The control device can be implemented by a main controller, such as an MCU, a DSP (Digital Signal Process, digital signal processing chip), an FPGA (Field Programmable Gate Array, programmable logic gate array chip), a PLC, a SOC (System On Chip, system-level chip), etc.

[0023] Such asFigure 4 As shown, an electromagnetic heating device (such as an induction cooker) includes a power input terminal 10 for connecting to a power supply voltage, a rectifying and filtering circuit 20, a power switching transistor 30, a driving circuit 40, a resonant circuit 50, and a control circuit 80. The input terminal of the rectifying and filtering circuit 20 is connected to the power input terminal 10 and is used to rectify and filter the power supply voltage and then output it. The first end of the power switching transistor 30 is interconnected with the ground terminal and the output terminal of the rectifying and filtering circuit 20. The driving circuit 40 is connected to the controlled terminal of the power switching transistor 30. The first end of the resonant circuit 50 is connected to the second end of the power switching transistor 30, and the second end of the resonant circuit 50 is connected to the output terminal of the rectifying and filtering circuit 20. The resonant circuit 50 can be implemented using an inductor and a capacitor to achieve efficient energy transfer and conversion at a specific frequency. The function of the resonant circuit 50 is to generate a high-frequency current in the heating coil (usually a copper coil located at the bottom of the induction cooker), thereby generating a changing magnetic field. Since the metal cookware placed on the induction cooker cuts this alternating magnetic field, eddy currents (i.e., circular currents) will be generated at the bottom of the pot. These eddy currents flow at the bottom of the pot, and because the bottom of the pot has resistance, heat will be generated, thus achieving the heating effect on the metal cookware. The electromagnetic heating device first connects to the power supply voltage through its power input terminal 10, such as mains alternating current. The rectifying and filtering circuit 20 converts the input alternating current into direct current, and the DC voltage is fed to the resonant circuit 50. After the electromagnetic heating device receives a working instruction, the control circuit 80 controls the driving circuit 40 to output a driving signal to the power switching transistor 30. When the power switching transistor 30 receives the driving signal, the resonant circuit 50 can resonate, thereby amplifying the current and generating a high-frequency current in the heating coil, and then generating a changing magnetic field around the heating coil. When a metal cookware is placed on the induction cooker, this magnetic field will induce eddy currents inside the cookware, which heat up due to the resistance effect, achieving the purpose of heating. Among them, the power switching transistor 30 can be implemented using an IGBT. The collector of the IGBT is connected to the output terminal of the resonant circuit 50, the emitter of the IGBT is grounded, and the gate of the IGBT is connected to the driving circuit 40.

[0024] In this embodiment, the electromagnetic heating device further includes a resonance slope detection module 60 and a delay calculation module 70. The resonance slope detection module 60 can be implemented by a voltage detection circuit and a main controller. The voltage detection circuit can be implemented by a voltage division resistor network, a Hall sensor, etc. The delay calculation module 70 can also be implemented by the main controller. The detection end of the voltage detection circuit is connected to the connection end of the resonance circuit 50 and the IGBT collector, and is used to detect the voltage of the IGBT collector and output the voltage detection result to the main controller. A timer can be integrated in the main controller. The main controller reads the collector voltage according to the voltage detection result and can use the timer to obtain the current timestamp. In this way, the main controller can determine the voltage resonance slope based on a plurality of consecutive voltage sampling values and the corresponding timestamps. Based on the calculated voltage resonance slope, the change trend of the IGBT collector voltage waveform can be predicted, and the delay time of the IGBT can be adjusted accordingly.

[0025] It should be noted that when the power switch tube 30 is driven by the drive circuit 40, the direct current in the rectifier filter circuit 20 will act on the resonant circuit 50 and be converted into a half-wave voltage. The IGBT collector voltage change curve has a trough, and the voltage at this time is 0V. In this embodiment, when it is determined that the voltage resonance slope tends to be flat according to the voltage resonance slope at different times, it indicates that the collector voltage is close to or at the valley value, that is, the IGBT can be triggered to conduct when the collector voltage is at the preset resonance voltage value. Among them, the preset resonance voltage value is set in advance by the R & D personnel. In this embodiment, the preset resonance voltage value can be set to 0V. The delay calculation module 70 calculates the estimated delay time required to reach the preset resonance voltage value according to the voltage resonance slope output by the resonance slope detection module 60, and the control circuit 80 adjusts the delay time of the power switch tube 30 based on the estimated delay time. If the preset delay time is 5ms and the estimated delay time is 6ms, it means that controlling the power switch tube 30 to conduct according to the preset delay time set at the factory will cause it to conduct in advance when the collector voltage has not reached the lowest resonance voltage point. When the IGBT conducts at a high voltage, since there is a high voltage and current overlap region at this time, this will result in a large transient conduction loss. Specifically, at the moment of conduction, the voltage VCE between the collector and emitter is relatively high, and at the same time, a large current flows through, resulting in a significant increase in the energy loss P = VCE × IC. The increased conduction loss will be converted into additional heat, causing the temperature of the IGBT and its surrounding components to rise. Being in a high-temperature state for a long time will not only accelerate the aging process of the device but also may lead to thermal runaway and ultimately damage the device. Therefore, it is necessary to delay the triggering of the power switch tube 30 to conduct, that is, increase the delay time, and adjust the delay time to the estimated delay time of 6ms to ensure that the IGBT conducts when the collector voltage is close to 0V or equal to 0V. On the contrary, if the preset delay time is 5ms and the estimated delay time is 4ms, if the power switch tube 30 is controlled to conduct according to the preset delay time set at the factory, it will conduct laggingly when the collector voltage exceeds the lowest resonance voltage point. At this time, the IGBT conducts after the collector voltage waveform has passed the trough, which means that the voltage has started to rise at this time, rather than the ideal zero-voltage state. There is still a high voltage and current overlap region at the moment of conduction, resulting in a large transient conduction loss. Therefore, it is necessary to trigger the power switch tube 30 to conduct in advance, that is, reduce the delay time, and adjust the preset delay time to the estimated delay time of 4ms. Finally, the IGBT is controlled to conduct with a delay according to the adjusted delay time (estimated delay time).

[0026] In practical applications, a preset resonant voltage value is determined according to the obtained voltage resonant slope, and the delay time of the power switch tube 30 is adjusted according to the preset resonant voltage value, and the power switch tube 30 is controlled to conduct with a delay according to the delay time. In this way, it is realized that the electromagnetic heating device can dynamically adjust the conduction moment of the IGBT under different load conditions, ensuring that it conducts each time when the resonant voltage of the resonant circuit 50 is at the preset resonant voltage value (usually when the voltage is close to 0V or equal to 0V), reducing the conduction loss of the power switch tube 30, thereby reducing the risk of overheating or damage of the power switch tube 30, prolonging the service life of the electromagnetic heating device, and improving the user experience.

[0027] In one embodiment, referring to Figure 2 , step S100 specifically includes: Step S110, obtaining the resonant voltages at at least three different times; Step S120, performing non-linear fitting on the resonant voltage and time according to the resonant voltages at at least three different times to obtain a fitting curve of the resonant voltage - time; Step S130, determining the voltage resonant slope according to the resonant voltage - time fitting curve.

[0028] Among them, step S130 specifically includes: Determining the derivatives of the resonant voltages at a preset number of points on the resonant voltage - time fitting curve according to the resonant voltage - time fitting curve, and determining the derivatives as the voltage resonant slope.

[0029] It can be understood that in the resonant circuit 50, the resonant voltage waveform is usually in the form of a periodic sine half-wave or close to a sine half-wave, which is non-linear in nature. Only using two data points can only determine a straight line and cannot well fit its characteristics. While three or more data points can construct a model that can better match these non-linear characteristics. Therefore, in order to accurately describe the change trend of the resonant voltage (IGBT collector voltage) with time, in this embodiment, at least three IGBT collector voltage values need to be collected at different time points.

[0030] Combined with the content of the above embodiments, the resonance slope detection module 60 is implemented by including a voltage detection circuit and a main controller. The voltage detection circuit is used to detect the voltage of the IGBT collector and output the voltage detection result to the main controller. The main controller reads the collector voltage data according to the voltage detection result and uses a timer to obtain the current timestamp. In this way, the main controller can obtain at least three resonance voltages at different times according to the voltage detection result, and obtain different times corresponding to the resonance voltages according to the timestamp. In this way, the polynomial fitting method (such as quadratic or cubic polynomial) is used to fit the collected data points to obtain a non-linear fitting curve of resonance voltage-time, and then a formula that can describe the relationship between resonance voltage and time change is obtained. For example, a polynomial fitting function can be used to obtain the relationship curve (fitting curve) of resonance voltage-time. In this embodiment, the quadratic polynomial fitting formula is taken as an example for illustration. Then, the polynomial coefficients a, b, and c are obtained through multiple resonance voltages and corresponding timestamp data points. Calculate the voltage resonance slope, that is, find the derivative . This derivative represents the change rate of the resonance voltage at different times. In this way, the voltage resonance slopes corresponding to the same time for a preset number of resonance voltages can be calculated, and it is determined whether they tend to be stable according to the two voltage resonance slopes before and after different times, and then the estimated delay time when the voltage resonance slope is in the stable stage is recorded. Among them, the preset number is set in advance by the R & D personnel. When the preset number takes a large enough value, the change trend of the voltage resonance slopes corresponding to the resonance voltages at different times can be accurately reflected. In this way, when both the two voltage resonance slopes before and after are within the preset slope range, it is determined that the collector voltage is at the trough, and the estimated delay time is calculated. The preset slope range is set in advance by the R & D personnel. In this embodiment, the preset slope range can be set to 0 - n to 0 + n, where n is a natural number and n should take a relatively small value. When the voltage resonance slope is within the preset slope range of 0 - n to 0 + n, the voltage resonance slope is close to or equal to 0. At this time, the IGBT collector voltage is at the lowest point of resonance, close to 0V or equal to 0V. The control circuit 80 can calculate the estimated delay time required to reach the preset resonance voltage value (0V), adjust the delay time of the power switch tube 30, and control the conduction of the IGBT according to the adjusted delay time (estimated delay time) to ensure that the IGBT conducts when the resonance voltage is at the preset resonance voltage value.

[0031] By determining the lowest point of the resonance voltage waveform and turning on the IGBT at this time, zero voltage switching (ZVS) is achieved, reducing the switching loss and improving the energy conversion efficiency of the electromagnetic heating device. At the same time, turning on the IGBT when the collector voltage is close to or equal to 0V avoids the current mutation under high voltage, thereby reducing the loss and heat generation risk of the IGBT and other related electronic components, prolonging the service life of the device, and improving the user experience.

[0032] In another embodiment, referring to Figure 3 , the voltage resonance slope at least includes a first voltage resonance slope and a second voltage resonance slope. Step S200 specifically includes: Step S210: Determine the difference between the first voltage resonance slope and the second voltage resonance slope; Step S220: When the difference is less than or equal to a preset slope difference, determine a preset resonance voltage value.

[0033] Wherein, the on-control method of the power switch tube 30 further includes: When the difference is less than or equal to the preset slope difference, it is determined that the change trend of the voltage resonance slope is in a stable stage, and the estimated delay time is determined according to the voltage resonance slope in the stable stage.

[0034] In this embodiment, taking the resonance voltage data at three different moments as an example for illustration. That is, V1, V2, and V3, and the corresponding time points are t1, t2, and t3 respectively. Then the first voltage resonance slope is: , and the second voltage resonance slope is: . The main controller then determines the difference △k between the first voltage resonance slope and the second voltage resonance slope, that is . The preset slope difference is set in advance by the R & D personnel. Assuming the preset slope difference is 0.01, if △k is 0.005, it means that the change of the voltage resonance slope tends to be stable. At this time, the IGBT collector voltage is close to or at the trough, that is, at the resonance lowest point. The main controller can calculate the estimated delay time required to reach the preset resonance voltage value (0V) and adjust the actual on-time of the IGBT, that is, control the IGBT to conduct with a delay to ensure that the IGBT conducts when the collector voltage is at the resonance lowest point.

[0035] Optionally, the adjustment of the delay time of the power switch tube 30 specifically includes: Increase or decrease the preset delay time to the estimated delay time according to the estimated delay time to adjust the delay time of the power switch tube 30.

[0036] It should be noted that Figure 6 Figure (a) in Figure 6 is a waveform diagram of the resonance voltage (IGBT collector voltage) changing with time. It shows a periodic change. Within each period, the collector voltage rises from 0 to the peak maximum value and then drops to 0.

[0037] Combined with the content of the above embodiments, after calculating the estimated delay time. Assume that the preset delay time set at the factory is 5 milliseconds (default value), and the delay time estimated based on the current load condition is 6 milliseconds. Refer to Figure 6 In the leading turn-on stage of (a) in Figure 6 , this indicates that the set preset delay time is short, and the IGBT will turn on during the resonant decline stage of its collector voltage, resulting in conduction loss. It is necessary to increase the delay time according to the estimated delay time. At this time, the control circuit 80 will automatically increase the delay time from 5 milliseconds to 6 milliseconds and control the IGBT to turn on with a delay according to 6 ms. Similarly, if the estimated delay time is 4 milliseconds, refer to Figure 6 In the lagging turn-on stage of (a) in

[0038] , this indicates that the set preset delay time is long, and the IGBT will turn on when the collector voltage is in the resonant rise stage, and there will also be conduction loss. At this time, it is necessary to reduce the delay time, and the control circuit 80 will reduce the delay time from 5 milliseconds to 4 milliseconds. That is, add / subtract based on the default preset delay time according to the estimated delay time to ensure that the IGBT turns on at the lowest point of the collector voltage, thereby reducing the conduction loss, as shown in the optimal turn-on stage of (a) in

[0039] The present invention provides a control device, which includes a memory, a processor, and a conduction control program of the power switch tube 30 stored on the memory and executable on the processor. The conduction control program of the power switch tube 30 is configured to implement the steps of the conduction control method of the power switch tube 30 described in any one of the above.

[0040] It should be noted that since the control device of the present invention is based on the above conduction control method of the power switch tube 30, therefore, the embodiments of the control device of the present invention include all the technical solutions of all the embodiments of the above conduction control method of the power switch tube 30, and the achieved technical effects are also exactly the same, which will not be elaborated here.

[0041] The present invention also provides an electromagnetic heating device, which includes the above-mentioned control device.

[0042] In this embodiment, the electromagnetic heating device may specifically be an induction cooker, a cooking appliance, or other application devices that require efficient electromagnetic heating.

[0043] Optionally, referring to Figure 4 , the electromagnetic heating device further includes: A power input terminal 10 for connecting to a power supply voltage; A rectifier filter circuit 20, the input terminal of the rectifier filter circuit 20 is connected to the power input terminal 10, and is used for rectifying and filtering the power supply voltage and then outputting; A power switch tube 30, the first end of the power switch tube 30 is interconnected with the ground terminal and the output terminal of the rectifier filter circuit 20; A drive circuit 40, the drive circuit 40 is connected to the controlled terminal of the power switch tube 30; A resonant circuit 50, the first end of the resonant circuit 50 is connected to the second end of the power switch tube 30, and the second end of the resonant circuit 50 is connected to the output terminal of the rectifier filter circuit 20; A resonant slope detection module 60, connected to the second end of the power switch tube 30, and is used for detecting the voltage resonant slope when the resonant circuit 50 works; A delay calculation module 70, connected to the output terminal of the resonant slope detection module 60, and is used for determining a preset resonant voltage value according to the voltage resonant slope, and for adjusting the delay time of the power switch tube 30 according to the determined preset resonant voltage value; A control circuit 80, respectively connected to the drive circuit 40 and the delay calculation module 70, and is used for controlling the drive circuit 40 to drive the power switch tube 30 to conduct with a delay according to the delay time, so as to conduct when the resonant voltage of the resonant circuit 50 is at the preset resonant voltage value.

[0044] In this embodiment, the control circuit 80 can be implemented by using the above-mentioned main controller. The power input terminal 10 can be implemented by using an AC power socket for connecting to the commercial power. The rectifier filter circuit 20 can use a bridge rectifier to convert alternating current into direct current, and then use a filter composed of resistors, inductors, capacitors, etc. for filtering. The power switch tube 30 can be implemented by using an IGBT (Insulated Gate Bipolar Transistor), where Figure 5 Q in is the power switch tube 30. The drive circuit 40 can be implemented by using a dedicated drive chip, a drive circuit 40 composed of basic components such as transistors, etc. As Figure 5As shown, the resonant circuit 50 can be an LC resonant circuit 50 composed of an inductor L and a capacitor C, and its parameters are set according to the required resonant frequency. The resonant slope detection module 60 can be implemented by a voltage detection circuit and a main controller. Among them, the voltage detection circuit can be a differential amplifier or a Hall effect sensor, which is used to monitor the change in the IGBT collector voltage when the LC resonant circuit 50 operates in resonance, and perform data acquisition and analysis through the main controller MCU to determine the voltage resonant slope. The delay calculation module 70 can be implemented by a main controller, which can be integrally provided or separately provided with at least one of the main controller in the resonant slope detection module 60 and the control circuit 80. The delay calculation module 70 is used to determine the estimated delay time when the resonant voltage reaches the preset resonant voltage value according to the voltage resonant slope output by the resonant slope detection module 60, so that the control circuit 80 adjusts the preset delay time to the estimated delay time, and outputs a drive control signal to the drive circuit 40 after delaying the preset delay time, and controls the drive circuit 40 to drive the IGBT to conduct with a delay.

[0045] In this embodiment, the preset resonant voltage value can be set to 0V. The delay calculation module 70 can calculate the estimated delay time required to reach the preset resonant voltage value according to the voltage resonant slope output by the resonant slope detection module 60, and the control circuit 80 adjusts the delay time of the power switch 30 based on the estimated delay time. For example, the preset delay time is 5ms, and the estimated delay time is 6ms. This means that if the power switch 30 is controlled to turn on according to the preset delay time set at the factory, the power switch 30 will turn on prematurely before the collector voltage reaches the lowest resonant voltage point. When the power switch 30 turns on at a high voltage, since there is a high voltage and current overlap region at this time, this will result in a large transient turn-on loss. Taking the power switch 30 as an IGBT as an example, at the moment when the IGBT turns on, the voltage VCE between the collector and emitter is relatively large, and at the same time, a large current flows through, resulting in a significant increase in the energy loss P = VCE × IC. And the increased turn-on loss will be converted into additional heat, causing the temperature of the IGBT and its surrounding components to rise. Being in a high-temperature state for a long time will not only accelerate the aging process of electronic components, but may also lead to thermal runaway, ultimately damaging the electromagnetic heating device. Therefore, it is necessary to delay the triggering of the power switch 30 to turn on, that is, increase the delay time, and adjust the delay time to the estimated delay time of 6ms, so that it can turn on when the voltage is close to 0V or equal to 0V. On the contrary, if the preset delay time is 5ms and the estimated delay time is 4ms, if the power switch 30 is controlled to turn on according to the preset delay time set at the factory, it will turn on laggingly when the collector voltage exceeds the lowest resonant voltage point. At this time, the IGBT turns on after the trough of the collector voltage waveform has passed, which means that the voltage has already started to rise at this time, rather than the ideal zero-voltage state. There is still a high voltage and current overlap region at the moment of turning on, resulting in a large transient turn-on loss. Therefore, it is necessary to trigger the power switch 30 to turn on in advance and reduce the delay time, that is, adjust the preset delay time from the set 5ms to 4ms. Finally, the IGBT is controlled to turn on with a delay according to the adjusted delay time (estimated delay time).

[0046] In practical applications, the preset resonant voltage value is determined according to the voltage resonant slope, and the delay time of the power switch 30 is adjusted according to the preset resonant voltage value, so that the control circuit 80 controls the power switch 30 to turn on with a delay according to the delay time. In this way, it is realized that the electromagnetic heating device can dynamically adjust the turn-on moment of the IGBT under different load conditions, ensuring that it turns on each time when the resonant voltage of the resonant circuit 50 is at the preset resonant voltage value (for example, when the collector voltage of the IGBT is close to 0V or equal to 0V), reducing the turn-on loss of the power switch 30, thereby reducing the risk of overheating or damage to the power switch 30, extending the service life of the electromagnetic heating device, and improving the user experience.

[0047] It should be noted that since the electromagnetic heating device of the present invention is based on the above control device, the embodiments of the electromagnetic heating device of the present invention include all the technical solutions of all the embodiments of the above control device, and the achieved technical effects are exactly the same, so they will not be elaborated here.

[0048] The above are only optional embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structural transformation made by using the content of the specification and drawings of the present invention under the inventive concept of the present invention, or any direct / indirect application in other related technical fields is included in the patent protection scope of the present invention.

Claims

1. A method for controlling the conduction of a power switch tube, characterized in that, Applied to an electromagnetic heating device, the electromagnetic heating device includes a power switching tube and a resonant circuit, the switching tube is electrically connected to the resonant circuit, and the conduction control method of the power switching tube includes: Obtain the voltage resonance slope when the resonant circuit is operating; Determine a preset resonance voltage value according to the voltage resonance slope; Adjust the delay time of the power switching tube according to the determined preset resonance voltage value, and control the power switching tube to conduct with a delay according to the delay time, so as to conduct when the resonance voltage of the resonant circuit is at the preset resonance voltage value.

2. The conduction control method of the power switch tube according to claim 1, characterized in that The specific step of obtaining the voltage resonance slope when the resonant circuit is operating includes: Obtain the resonance voltages at at least three different times; Perform non-linear fitting on the resonance voltage and time according to the resonance voltages at at least three different times to obtain a fitting curve of resonance voltage - time; Determine the voltage resonance slope according to the resonance voltage - time fitting curve.

3. The conduction control method of the power switching transistor according to claim 2, characterized in that, The specific step of determining the voltage resonance slope according to the resonance voltage - time fitting curve includes: Determine the derivatives of the resonance voltages at a preset number of points on the resonance voltage - time fitting curve according to the resonance voltage - time fitting curve, and determine the derivatives as the voltage resonance slope.

4. The method for controlling the conduction of the power switching transistor according to claim 1, wherein The voltage resonance slope at least includes a first voltage resonance slope and a second voltage resonance slope, and the specific step of determining the preset resonance voltage value according to the voltage resonance slope includes: Determine the difference between the first voltage resonance slope and the second voltage resonance slope; When the difference is less than or equal to a preset slope difference, determine the preset resonance voltage value.

5. The conduction control method of the power switching transistor according to claim 4, characterized in that, The conduction control method of the power switching tube further includes: When the difference is less than or equal to the preset slope difference, determine that the change trend of the voltage resonance slope is in a stable stage, and determine an estimated delay time according to the voltage resonance slope in the stable stage.

6. The method for controlling the conduction of the power switch tube according to claim 5, characterized in that, The specific step of adjusting the delay time of the power switching tube includes: Increase or decrease the preset delay time to the estimated delay time according to the estimated delay time, so as to adjust the delay time of the power switching tube.

7. A control device, characterized in that, The control device includes a memory, a processor, and a conduction control program of the power switching tube stored on the memory and executable on the processor. The conduction control program of the power switching tube is configured to implement the steps of the conduction control method of the power switching tube as described in any one of claims 1 to 6.

8. An electromagnetic heating device, characterized in that, The electromagnetic heating device includes the control device as described in claim 7.

9. The electromagnetic heating device according to claim 8, wherein, The electromagnetic heating device further includes: A power input terminal for connecting to a power supply voltage; A rectifier filter circuit, the input end of the rectifier filter circuit is connected to the power input terminal, and is used for rectifying and filtering the power supply voltage and then outputting; A power switching tube, the first end of the power switching tube is interconnected with the ground terminal and the output end of the rectifier filter circuit; A drive circuit, the drive circuit is connected to the controlled end of the power switching tube; A resonant circuit, the first end of the resonant circuit is connected to the second end of the power switching tube, and the second end of the resonant circuit is connected to the output end of the rectifier filter circuit; A resonant slope detection module, connected to the second end of the power switch tube, for detecting the voltage resonant slope when the resonant circuit operates; A delay calculation module, connected to the output end of the resonant slope detection module, for determining a preset resonant voltage value according to the voltage resonant slope, and for adjusting the delay time of the power switch tube according to the determined preset resonant voltage value; A control circuit, respectively connected to the drive circuit and the delay calculation module, for controlling the drive circuit to drive the power switch tube to conduct with a delay according to the delay time, so as to conduct when the resonant voltage of the resonant circuit is at the preset resonant voltage value.

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