Power switch tube conduction control method, control device and electromagnetic heating equipment

Abstract

The present invention discloses a power switch conduction control method, control device, and electromagnetic heating equipment, relating to the field of electrical equipment technology. In the power switch conduction control method, the voltage resonance slope of the resonant circuit during operation is first obtained; a preset resonant voltage value is then determined based on the voltage resonance slope; the power switch delay time is then adjusted based on the determined preset resonant voltage value, and the power switch is controlled to conduct with a delayed delay based on the delay time, so that the power switch conducts when the resonant voltage of the resonant circuit reaches the preset resonant voltage value. The present invention aims to reduce the conduction loss of the power switch, thereby reducing the risk of overheating or damage to the power switch, and extending the service life of the electromagnetic heating equipment.

Description

Technical Field

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

[0002] The core operating principle of electromagnetic heating equipment is eddy current heating generated by electromagnetic induction, and its power switching device plays a crucial role. The operating state of the power switching device directly affects the efficiency and reliability of the induction cooker. The turn-on timing of the power switching device is typically determined by the comparison signal between the bus voltage (i.e., the DC voltage after rectifier filtering of the input AC voltage) and the power switching device voltage. Turn-on is triggered after a certain delay to ensure that it turns on at the optimal time, thereby achieving zero voltage switching (ZVS), reducing conduction losses and heat generation. However, the delay time used to control the turn-on timing of the power switching device in most electromagnetic heating devices currently on the market is a fixed value set at the factory. Due to the variability in the resonant period of the LC resonant circuit under different load conditions, this fixed delay time may cause the power switching device to turn on prematurely under high voltage or heavy load conditions, resulting in significant conduction losses, which in turn may cause the power switching device to overheat or even damage, shortening the service life of the electromagnetic heating device. Summary of the Invention

[0003] The main purpose of the present invention is to propose a conduction control method, control device and electromagnetic heating equipment for a power switch tube, 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 equipment.

[0004] To achieve the above objectives, the present invention provides a conduction control method for a power switch tube, which is applied to an electromagnetic heating device. The electromagnetic heating device includes a power switch tube and a resonant circuit. The switch tube is electrically connected to the resonant circuit. The conduction control method for the power switch tube includes:

[0005] Obtaining a voltage resonance slope when the resonant circuit is operating;

[0006] Determining a preset resonant voltage value according to the voltage resonance slope;

[0007] The delay time of the power switch tube is adjusted according to the determined preset resonant voltage value, and the power switch tube is controlled to be delayed and turned on according to the delay time so as to be turned on when the resonant voltage of the resonant circuit is at the preset resonant voltage value.

[0008] In one embodiment, obtaining the voltage resonance slope of the resonant circuit when it is operating specifically includes:

[0009] Obtaining the resonant voltage at at least three different moments;

[0010] Performing nonlinear fitting on the resonance voltage and time according to the resonance voltage at at least three different moments to obtain a resonance voltage-time fitting curve;

[0011] The voltage resonance slope is determined according to the resonant voltage-time fitting curve.

[0012] In one embodiment, determining the voltage resonance slope according to the resonant voltage-time fitting curve specifically includes:

[0013] Derivatives of a preset number of resonance voltages on the resonance voltage-time fitting curve are determined according to the resonance voltage-time fitting curve, and the derivatives are determined as voltage resonance slopes.

[0014] In one embodiment, the voltage resonance slope includes at least a first voltage resonance slope and a second voltage resonance slope, and determining the preset resonance voltage value according to the voltage resonance slope specifically includes:

[0015] determining a difference between the first voltage resonance slope and the second voltage resonance slope;

[0016] When the difference is less than or equal to the preset slope difference, a preset resonant voltage value is determined.

[0017] In one embodiment, the conduction control method of the power switch tube further includes:

[0018] 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.

[0019] In one embodiment, adjusting the delay time of the power switch tube specifically includes:

[0020] The preset delay time is increased or decreased to the estimated delay time according to the estimated delay time, so as to adjust the delay time of the power switch tube.

[0021] The present invention also proposes a control device, which includes a memory, a processor, and a conduction control program for a power switch tube stored in the memory and runnable on the processor, wherein the conduction control program for the power switch tube is configured to implement the steps of the conduction control method for the power switch tube described in any one of the above items.

[0022] The present invention also provides an electromagnetic heating device, which includes the control device described above.

[0023] In one embodiment, the electromagnetic heating device further comprises:

[0024] Power input terminal, used to access the power supply voltage;

[0025] a rectifier and filter circuit, wherein the input end of the rectifier and filter circuit is connected to the power input end, and is used to rectify and filter the power supply voltage before outputting it;

[0026] A power switch tube, wherein a first end of the power switch tube is interconnected with a ground end and an output end of the rectifier and filter circuit;

[0027] A driving circuit connected to the controlled end of the power switch tube;

[0028] A resonant circuit, wherein a first end of the resonant circuit is connected to the second end of the power switch tube, and a second end of the resonant circuit is connected to the output end of the rectifier and filter circuit;

[0029] a resonance slope detection module, connected to the second end of the power switch tube, and used to detect the voltage resonance slope when the resonant circuit is working;

[0030] a delay calculation module, connected to the output end of the resonance slope detection module, for determining a preset resonance voltage value according to the voltage resonance slope, and for adjusting the delay time of the power switch tube according to the determined preset resonance voltage value;

[0031] The control circuit is connected to the driving circuit and the delay calculation module respectively, and is used to control the driving circuit to drive the power switch tube to delay conduction according to the delay time, so as to turn on when the resonant voltage of the resonant circuit is at a preset resonant voltage value.

[0032] In practical applications, a preset resonant voltage value is determined based on the acquired voltage resonance slope, and the delay time of the power switch is adjusted based on the preset resonant voltage value. This delay time controls the power switch's delayed conduction. This allows the electromagnetic heating device to dynamically adjust the IGBT's turn-on timing under varying load conditions, ensuring that it always turns on when the resonant voltage of the resonant circuit is at the preset resonant voltage value (for example, when the resonant voltage is close to or equal to 0V). This reduces the conduction losses of the power switch, thereby reducing the risk of overheating or damage to the power switch, extending the life of the electromagnetic heating device, and improving the user experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0034] Figure 1 1. A flow chart of an embodiment of a method for controlling the conduction of a power switch tube according to the present invention;

[0035] Figure 2 1 is a flow chart of another embodiment of a conduction control method for a power switch tube according to the present invention;

[0036] Figure 3 1 is a flow chart of another embodiment of a conduction control method for a power switch tube according to the present invention;

[0037] Figure 4 This is a schematic diagram of a module of an electromagnetic heating device according to an embodiment of the present invention;

[0038] Figure 5 This is a schematic diagram of a module of another embodiment of the electromagnetic heating device of the present invention;

[0039] Figure 6 The waveform diagram of the resonant voltage changing with time and the schematic diagram of the square wave signal used to control the on / off of the IGBT.

[0040] Description of Figure Numbers:

[0041] 10. Power input terminal; 20. Rectification and filtering circuit; 30. Power switch tube; 40. Drive circuit; 50. Resonant circuit; 60. Resonant slope detection module; 70. Delay calculation module; 80. Control circuit.

[0042] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0043] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0044] It should be noted that in this article, step codes such as S100 and S200 are used for the purpose of expressing the corresponding content more clearly and concisely, and do not constitute a substantial limitation on the order. When implementing the step, those skilled in the art may execute S200 first and then S100, etc., but these should all be within the scope of protection of this application.

[0045] The core operating principle of electromagnetic heating equipment is to generate eddy current heating through electromagnetic induction, and its power switching device plays a crucial role. The operating state of the power switching device directly affects the efficiency and reliability of the induction cooker. The turn-on timing of the power switching device is typically determined by the comparison signal between the bus voltage (i.e., the DC voltage after rectifier filtering of the input AC voltage) and the power switching device voltage. The turn-on trigger is triggered after a certain delay to ensure that it turns on at the optimal time, thereby achieving zero voltage switching (ZVS), reducing conduction losses and heat generation. However, the delay time used to control the turn-on timing of the power switching device in most electromagnetic heating devices currently on the market is a fixed value set at the factory. Due to the variability in the resonant period of the LC resonant circuit under different load conditions, this fixed delay time may cause the power switching device to turn on prematurely under high voltage or heavy load conditions, resulting in significant conduction losses, which in turn may cause the power switch 30 to overheat or even damage, shortening the service life of the electromagnetic heating device.

[0046] For this purpose, refer to Figure 1 The present invention proposes a conduction control method for a power switch tube 30, which is applied to an electromagnetic heating device. The electromagnetic heating device includes a power switch tube 30 and a resonant circuit 50. The switch tube is electrically connected to the resonant circuit 50. The conduction control method for the power switch tube 30 includes:

[0047] Step S100, obtaining the voltage resonance slope of the resonant circuit 50 when it is working;

[0048] Step S200: determining a preset resonant voltage value according to the voltage resonance slope;

[0049] Step S300: Adjust the delay time of the power switch tube 30 according to the determined preset resonant voltage value, and control the power switch tube 30 to delay conduction according to the delay time so as to be turned on when the resonant voltage of the resonant circuit 50 is at the preset resonant voltage value.

[0050] In this embodiment, the conduction control method for the power switch tube 30 of the present invention can be applied to a control device for electromagnetic heating equipment. The control device includes a memory, a processor, and a conduction control program for the power switch tube 30 stored in the memory and executable on the processor. The conduction control program for the power switch tube 30 is configured to implement the steps of the conduction control method for the power switch tube 30. The control device can be implemented using a main controller, such as an MCU, a DSP (Digital Signal Process), an FPGA (Field Programmable Gate Array), a PLC, a SOC (System on Chip), etc.

[0051] like Figure 4As shown, an electromagnetic heating device (such as an induction cooker) includes a power input terminal 10 for receiving a power supply voltage, a rectifier and filter circuit 20, a power switch 30, a drive circuit 40, a resonant circuit 50, and a control circuit 80. The input terminal of the rectifier and filter circuit 20 is connected to the power input terminal 10 and is used to rectify and filter the power supply voltage before outputting it. The first terminal of the power switch 30 is interconnected to the ground terminal and the output terminal of the rectifier and filter circuit 20. The drive circuit 40 is connected to the controlled terminal of the power switch 30. The first terminal of the resonant circuit 50 is connected to the second terminal of the power switch 30, and the second terminal of the resonant circuit 50 is connected to the output terminal of the rectifier and filter circuit 20. The resonant circuit 50 can be implemented using inductors and capacitors to achieve efficient energy transmission and conversion at a specific frequency. The function of the resonant circuit 50 is to generate high-frequency current in the heating coil (typically a copper coil located at the bottom of the induction cooker), thereby generating a changing magnetic field. Metal pots placed on the induction cooker cut through this alternating magnetic field, generating eddy currents (i.e., circular currents) at the bottom of the pot. These eddy currents flow at the bottom of the pot, and because the pot has resistance, they generate heat, thereby heating the metal pot. The electromagnetic heating device first receives a power supply voltage, such as AC power, through its power input terminal 10. The rectifier and filter circuit 20 converts the received AC power into DC power, and the DC voltage is fed to the resonant circuit 50. After the electromagnetic heating device receives the working instruction, the control circuit 80 controls the drive circuit 40 to output a drive signal to the power switch tube 30. When the power switch tube 30 receives the drive signal, the resonant circuit 50 can resonate, thereby amplifying the current and generating a high-frequency current in the heating coil, thereby generating a changing magnetic field around the heating coil. When a metal pot is placed on the induction cooker, this magnetic field induces eddy currents inside the pot, which generates heat due to the resistance effect, achieving the purpose of heating. Among them, the power switch tube 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 drive circuit 40.

[0052] In this embodiment, the electromagnetic heating device also includes a resonance slope detection module 60 and a delay calculation module 70. The resonance slope detection module 60 can be implemented using a voltage detection circuit and a main controller. The voltage detection circuit can be implemented using a voltage divider resistor network, a Hall sensor, etc. The delay calculation module 70 can also be implemented using a 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 multiple consecutive voltage sampling values ​​and corresponding timestamps. Based on the calculated voltage resonance slope, the changing trend of the IGBT collector voltage waveform can be predicted, and the delay time of the IGBT can be adjusted accordingly.

[0053] It should be noted that when the power switch tube 30 is driven by the driving circuit 40, the direct current in the rectifier filter circuit 20 will be applied to the resonant circuit 50 and converted into a half-wave voltage. The IGBT collector voltage change curve has a trough, and the voltage is 0V at this time. In this embodiment, when the voltage resonance slope is determined to be flat according to the voltage resonance slope at different times, it indicates that the collector voltage is close to or at a valley value, that is, the IGBT can be triggered to turn on when the collector voltage is at a preset resonant voltage value. Among them, the preset resonant voltage value is set in advance by the R&D personnel. In this embodiment, the preset resonant voltage value can be set to 0V. The delay calculation module 70 calculates the estimated delay time required to reach the preset resonant voltage value based on the voltage resonance slope output by the resonant 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, this means that if the power switch 30 is turned on according to the factory-set preset delay time, it will turn on prematurely, before the collector voltage reaches the minimum resonant voltage point. When the IGBT turns on at high voltage, the high voltage and current overlap region will result in large transient conduction losses. Specifically, at the turn-on instant, the collector-emitter voltage VCE is high, and a large current flows, resulting in a significant increase in energy loss (P = VCE × IC). The increased conduction losses convert into additional heat, causing the IGBT and its surrounding components to heat up. Prolonged exposure to high temperatures not only accelerates device aging but can also lead to thermal runaway, ultimately damaging the device. Therefore, it is necessary to delay the triggering of the power switch 30 to turn on, i.e., increase the delay time. Adjust the delay time to the estimated delay time of 6ms to ensure that the IGBT turns on when the collector voltage is close to or equal to 0V. Conversely, if the preset delay time is 5ms and the estimated delay time is 4ms, if the power switch 30 is turned on according to the preset delay time set at the factory, it will be turned on after the collector voltage exceeds the minimum resonant voltage point. At this time, the IGBT turns on after the collector voltage waveform has passed the trough, which means that the voltage has begun to rise, rather than the ideal zero voltage state. At the moment of turn-on, there is still a high voltage and current overlap area, resulting in large transient conduction losses. Therefore, it is necessary to trigger the power switch 30 to turn on earlier, that is, to 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 delayed turn-on based on the adjusted delay time (estimated delay time).

[0054] In actual applications, a preset resonant voltage value is determined based on the acquired voltage resonance slope, and the delay time of the power switch 30 is adjusted based on the preset resonant voltage value. The power switch 30 is then controlled to conduct at a delayed time based on the delay time. This allows the electromagnetic heating device to dynamically adjust the IGBT's conduction timing under varying load conditions, ensuring that it always conducts when the resonant voltage of the resonant circuit 50 is at the preset resonant voltage value (typically, a voltage close to or equal to 0V). This reduces the conduction losses 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.

[0055] In one embodiment, reference Figure 2 , step S100 specifically includes:

[0056] Step S110, obtaining the resonant voltage at at least three different moments;

[0057] Step S120: performing nonlinear fitting on the resonance voltage and time according to the resonance voltage at at least three different moments to obtain a fitting curve of the resonance voltage-time;

[0058] Step S130: Determine the voltage resonance slope according to the resonant voltage-time fitting curve.

[0059] Step S130 specifically includes:

[0060] Derivatives of a preset number of resonance voltages on the resonance voltage-time fitting curve are determined according to the resonance voltage-time fitting curve, and the derivatives are determined as voltage resonance slopes.

[0061] It will be appreciated that in resonant circuit 50, the resonant voltage waveform is typically a periodic half-sine wave or a near-half-sine wave, which is inherently nonlinear. Using only two data points can only determine a straight line, which cannot accurately fit its characteristics. However, three or more data points can construct a model that better matches these nonlinear characteristics. Therefore, to accurately describe the temporal variation trend of the resonant voltage (IGBT collector voltage), in this embodiment, at least three IGBT collector voltage values ​​are collected at different time points.

[0062] In combination with the above embodiments, the resonant slope detection module 60 includes a voltage detection circuit and a main controller to implement. 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 the resonant voltage at at least three different moments according to the voltage detection result, and obtain the different moments corresponding to the resonant voltage according to the timestamp. In this way, a polynomial fitting method (such as a quadratic or cubic polynomial) is used to fit the collected data points to obtain a nonlinear fitting curve of the resonant voltage-time, and then a formula that can describe the relationship between the resonant voltage and time is obtained. For example, a polynomial fitting function can be used to obtain a resonant voltage-time relationship curve (fitting curve). In this embodiment, the quadratic polynomial fitting formula is used. Take the example of . Then get the polynomial coefficients a, b, c through multiple resonant voltages and corresponding timestamp data points. Calculate the voltage resonance slope, that is, find the derivative This derivative represents the rate of change of the resonant voltage at different moments. In this way, the voltage resonance slope corresponding to a preset number of resonant voltages at the same moment can be calculated. The two preceding and following voltage resonance slopes at different moments can be used to determine whether the voltage resonance slope has stabilized. The estimated delay time during which the voltage resonance slope remains stable is then recorded. The preset number is set in advance by the R&D personnel. When the preset number is sufficiently large, it accurately reflects the changing trend of the voltage resonance slope corresponding to the resonant voltage at different moments. Thus, when both the preceding and following voltage resonance slopes are within the preset slope range, the collector voltage is determined to be at a 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 from 0-n to 0+n, where n is a natural number and should be a smaller 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 point, the IGBT collector voltage is at the lowest point of resonance, close to or equal to 0V. The control circuit 80 can calculate the estimated delay time required to reach the preset resonant 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 is turned on when the resonant voltage is at the preset resonant voltage value.

[0063] By determining the lowest point of the resonant voltage waveform and turning on the IGBT at that point, zero voltage switching (ZVS) is achieved, reducing switching losses and improving the energy conversion efficiency of the electromagnetic heating device. Furthermore, turning on the IGBT when the collector voltage is close to or equal to 0V avoids sudden current changes at high voltages, thereby reducing losses and heating risks in the IGBT and other related electronic components, thereby extending the device's service life and improving the user experience.

[0064] In another embodiment, reference Figure 3 The voltage resonance slope includes at least a first voltage resonance slope and a second voltage resonance slope. Step S200 specifically includes:

[0065] Step S210: determining a difference between the first voltage resonance slope and the second voltage resonance slope;

[0066] Step S220: When the difference is less than or equal to the preset slope difference, determine a preset resonant voltage value.

[0067] The conduction control method of the power switch tube 30 further includes:

[0068] 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.

[0069] In this embodiment, the resonance voltage data at three different moments are used as an example for explanation. That is, V1, V2 and V3, corresponding to time points t1, t2 and t3 respectively. Then the first voltage resonance slope is: , the second voltage resonance slope is: The main controller 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 R&D personnel. For example, if the preset slope difference is 0.01 and Δk is 0.0.05, the voltage resonant slope is stable. At this point, the IGBT collector voltage is near or at the valley, or at the lowest point of resonance. The main controller calculates the estimated delay time required to reach the preset resonant voltage value (0V) and adjusts the actual IGBT turn-on time, controlling the IGBT's delayed turn-on time to ensure that the IGBT turns on when the collector voltage reaches the lowest point of resonance.

[0070] Optionally, adjusting the delay time of the power switch tube 30 specifically includes:

[0071] The preset delay time is increased or decreased to the estimated delay time according to the estimated delay time, so as to adjust the delay time of the power switch tube 30 .

[0072] It should be noted that Figure 6 Figure (a) shows the waveform of the resonant voltage (IGBT collector voltage) changing with time. It shows a periodic change, with the collector voltage rising from 0 to the peak value and then falling back to 0 in each cycle. Figure 6(b) is a schematic diagram of a square wave signal for controlling the on / off of the IGBT. In this embodiment, the IGBT is turned on when the voltage level is high and is turned off when the voltage level is low.

[0073] Combined with the above embodiment, after calculating the estimated delay time, it is assumed that the factory-set preset delay time is 5 milliseconds (default value), and the delay time estimated based on the current load condition is 6 milliseconds. Figure 6 In the advanced turn-on phase of (a), it is shown that the preset delay time is too short, and the IGBT will turn on when its collector voltage is in the resonant drop phase, resulting in conduction loss. The delay time needs to be increased 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 delay turn-on according to 6ms. Similarly, if the estimated delay time is 4 milliseconds, refer to Figure 6 The delayed turn-on phase in (a) indicates that the preset delay time is too long. The IGBT will turn on when the collector voltage is in the resonant rising phase, which will also cause conduction losses. In this case, the delay time needs to be reduced. The control circuit 80 will reduce the delay time from 5 milliseconds to 4 milliseconds. That is, the default preset delay time is added or subtracted based on the estimated delay time to ensure that the IGBT turns on at the lowest point of the collector voltage, thereby reducing conduction losses. Figure 6 The optimal opening stage is shown in (a).

[0074] In practical applications, a nonlinear fit is performed on the resonant voltage and time based on three or more collected IGBT collector voltage values. The derivative of the nonlinear fitting curve of the resonant voltage-time relationship is determined as the voltage resonance slope. The estimated delay time is recorded when the voltage resonance slope approaches a plateau at two different moments in time. This allows the IGBT to conduct when the collector voltage reaches the lowest point of the resonant voltage. This reduces the conduction losses of the power switch 30, thereby reducing the risk of overheating or damage to the power switch 30. Furthermore, by employing algorithms such as polynomial fitting, the accuracy of delay adjustment is improved, further enhancing the reliability and stability of the electromagnetic heating device.

[0075] The present invention proposes a control device, which includes a memory, a processor, and a conduction control program for a power switch tube 30 stored in the memory and executable on the processor. The conduction control program for the power switch tube 30 is configured to implement the steps of any of the above-described conduction control methods for the power switch tube 30.

[0076] It is worth noting that since the control device of the present invention is based on the above-mentioned conduction control method of the power switch tube 30, the embodiments of the control device of the present invention include all technical solutions of all embodiments of the above-mentioned conduction control method of the power switch tube 30, and the technical effects achieved are also exactly the same, which will not be repeated here.

[0077] The present invention also provides an electromagnetic heating device, which includes the control device described above.

[0078] In this embodiment, the electromagnetic heating device may specifically be an induction cooker, a cooking utensil, or other application equipment requiring efficient electromagnetic heating.

[0079] Optionally, refer to Figure 4 , the electromagnetic heating device also includes:

[0080] A power input terminal 10 is used to connect to the power supply voltage;

[0081] a rectifier and filter circuit 20, the input end of which is connected to the power input end 10, and is used to rectify and filter the power supply voltage before outputting it;

[0082] A power switch tube 30, wherein a first end of the power switch tube 30 is interconnected with a ground end and an output end of the rectifier and filter circuit 20;

[0083] A driving circuit 40 connected to the controlled end of the power switch tube 30;

[0084] A resonant circuit 50 , wherein a first end of the resonant circuit 50 is connected to a second end of the power switch tube 30 , and a second end of the resonant circuit 50 is connected to an output end of the rectifier and filter circuit 20 ;

[0085] A resonance slope detection module 60 is connected to the second end of the power switch tube 30 and is used to detect the voltage resonance slope of the resonant circuit 50 when it is working;

[0086] a delay calculation module 70 connected to the output end of the resonance slope detection module 60, for determining a preset resonance voltage value according to the voltage resonance slope, and for adjusting the delay time of the power switch tube 30 according to the determined preset resonance voltage value;

[0087] The control circuit 80 is connected to the driving circuit 40 and the delay calculation module 70 respectively, and is used to control the driving circuit 40 to drive the power switch tube 30 to delay conduction according to the delay time, so as to turn on when the resonant voltage of the resonant circuit 50 is at a preset resonant voltage value.

[0088] In this embodiment, the control circuit 80 can be implemented using the above-mentioned main controller. The power input terminal 10 can be implemented using an AC socket for connecting to the mains. The rectifier and filter circuit 20 can use a bridge rectifier to convert AC power into DC power, and then use a filter composed of resistors, inductors, capacitors, etc. to perform filtering. The power switch tube 30 can be implemented using an IGBT (insulated gate bipolar transistor), wherein: Figure 5 Q in the figure is the power switch tube 30. The driving circuit 40 can be implemented by using a dedicated driving chip, a driving circuit 40 composed of basic components such as transistors, etc. Figure 5 As 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 using a voltage detection circuit and a main controller, wherein 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 is in resonant operation, 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 using a main controller, which can be integrated with at least one of the main controller and the control circuit 80 in the resonant slope detection module 60 or set separately. The delay calculation module 70 is used to determine the estimated delay time when the resonant voltage is at a preset resonant voltage value based on 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 the preset delay time, controlling the drive circuit 40 to drive the IGBT to delay conduction.

[0089] 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 based on the voltage resonance slope output by the resonant slope detection module 60. The control circuit 80 then adjusts the delay time of the power switch 30 based on the estimated delay time. For example, if the preset delay time is 5ms and the estimated delay time is 6ms, this indicates that the power switch 30 is turned on according to the factory-set preset delay time. The power switch 30 will be turned on prematurely, before the collector voltage reaches the minimum resonant voltage point. When the power switch 30 is turned on at a high voltage, the presence of a high voltage and current overlap region will result in significant transient conduction losses. For example, using an IGBT as the power switch 30, at the moment the IGBT turns on, the collector-emitter voltage VCE is high, and a large current flows, resulting in a significant increase in energy loss (P = VCE × IC). Furthermore, the increased conduction losses convert into additional heat, causing the temperature of the IGBT and its surrounding components to rise. Long-term exposure to high temperatures not only accelerates the aging process of electronic components but can also lead to thermal runaway, ultimately damaging the electromagnetic heating equipment. Therefore, it is necessary to delay the triggering of the power switch 30 to conduct when the voltage is close to or equal to 0V. This means increasing the delay time and adjusting the delay time to an estimated 6ms. This allows the power switch 30 to conduct when the voltage is close to or equal to 0V. Conversely, if the preset delay time is 5ms and the estimated delay time is 4ms, if the power switch 30 is controlled to conduct according to the factory-set preset delay time, it will conduct after the collector voltage exceeds the minimum resonant voltage point. In this case, the IGBT will not conduct until the collector voltage waveform has passed the trough, meaning that the voltage has begun to rise, rather than the ideal zero voltage state. At the moment of conduction, there is still a high voltage and current overlap region, resulting in large transient conduction losses. Therefore, it is necessary to trigger the power switch 30 to conduct in advance and reduce the delay time. Specifically, the preset delay time is adjusted from 5ms to 4ms. Finally, the IGBT's delayed turn-on is controlled based on the adjusted delay time (estimated delay time).

[0090] In practical applications, a preset resonant voltage value is determined based on the voltage resonance slope, and the delay time of the power switch 30 is adjusted based on the preset resonant voltage value, so that the control circuit 80 controls the power switch 30 to delay conduction based on the delay time. This allows the electromagnetic heating device to dynamically adjust the IGBT's turn-on timing under different load conditions, ensuring that the device always turns on when the resonant voltage of the resonant circuit 50 is at the preset resonant voltage value (for example, when the IGBT collector voltage is close to or equal to 0V). This reduces the conduction 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.

[0091] It is worth noting that since the electromagnetic heating equipment of the present invention is based on the above-mentioned control device, the embodiments of the electromagnetic heating equipment of the present invention include all technical solutions of all embodiments of the above-mentioned control device, and the technical effects achieved are also exactly the same, which will not be repeated here.

[0092] The above descriptions are merely optional embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present invention's description and drawings, or direct / indirect applications in other related technical fields within the scope of the present invention are 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 electromagnetic heating equipment, the electromagnetic heating equipment includes a power switch tube and a resonant circuit, the switch tube is electrically connected to the resonant circuit, and the conduction control method of the power switch tube includes: Obtaining a voltage resonance slope when the resonant circuit is operating; Determining a preset resonant voltage value according to the voltage resonance slope; The delay time of the power switch tube is adjusted according to the determined preset resonant voltage value, and the power switch tube is controlled to be delayed and turned on according to the delay time so as to be turned on when the resonant voltage of the resonant circuit is at the preset resonant voltage value.

2. The conduction control method of a power switch tube according to claim 1, wherein: The obtaining of the voltage resonance slope of the resonant circuit when it is operating specifically includes: Obtaining the resonant voltage at at least three different moments; Performing nonlinear fitting on the resonance voltage and time according to the resonance voltage at at least three different moments to obtain a resonance voltage-time fitting curve; The voltage resonance slope is determined according to the resonant voltage-time fitting curve.

3. The conduction control method of a power switch tube according to claim 2, wherein: Determining the voltage resonance slope according to the resonant voltage-time fitting curve specifically includes: Derivatives of a preset number of resonance voltages on the resonance voltage-time fitting curve are determined according to the resonance voltage-time fitting curve, and the derivatives are determined as voltage resonance slopes.

4. The conduction control method of a power switch tube according to claim 1, wherein: The voltage resonance slope includes at least a first voltage resonance slope and a second voltage resonance slope, and determining the preset resonance voltage value according to the voltage resonance slope specifically includes: determining a difference between the first voltage resonance slope and the second voltage resonance slope; When the difference is less than or equal to the preset slope difference, a preset resonant voltage value is determined.

5. The conduction control method of a power switch tube according to claim 4, wherein: The conduction control method of the power switch tube 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.

6. The conduction control method of a power switch tube according to claim 5, wherein: The adjusting the delay time of the power switch tube specifically includes: The preset delay time is increased or decreased to the estimated delay time according to the estimated delay time, so as to adjust the delay time of the power switch tube.

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

8. An electromagnetic heating device, characterized in that: The electromagnetic heating device comprises the control device according to claim 7.

9. The electromagnetic heating device according to claim 8, characterized in that The electromagnetic heating device also includes: Power input terminal, used to access the power supply voltage; a rectifier and filter circuit, the input end of which is connected to the power input end, and is used to rectify and filter the power supply voltage before outputting it; A power switch tube, wherein a first end of the power switch tube is interconnected with a ground end and an output end of the rectifier and filter circuit; A driving circuit connected to the controlled end of the power switch tube; A resonant circuit, wherein a first end of the resonant circuit is connected to the second end of the power switch tube, and a second end of the resonant circuit is connected to the output end of the rectifier and filter circuit; a resonance slope detection module, connected to the second end of the power switch tube, and used to detect the voltage resonance slope of the resonant circuit when it is working; a delay calculation module, connected to the output end of the resonance slope detection module, for determining a preset resonance voltage value according to the voltage resonance slope, and for adjusting the delay time of the power switch tube according to the determined preset resonance voltage value; The control circuit is connected to the driving circuit and the delay calculation module respectively, and is used to control the driving circuit to drive the power switch tube to delay conduction according to the delay time, so as to turn on when the resonant voltage of the resonant circuit is at a preset resonant voltage value.

Images