Electromagnetic heating control method and electromagnetic heating system

Abstract

The invention discloses an electromagnetic heating control method and an electromagnetic heating system, and relates to the technical field of cooking household appliances. The method is applied to the electromagnetic heating system, the electromagnetic heating system comprises a power switch and a zero-cross detection unit, and the zero-cross detection unit is configured to detect a mains supply zero-cross signal; the electromagnetic heating control method comprises the steps that on the basis of a mains supply zero-crossing signal and the preset power of an induction cooker, a wave loss mode serves as a power control method, and each driving period of the wave loss mode is provided with a discharging stage and a heating stage; in the discharging stage, the first pulse signal drives the power switch to be switched on; in the heating stage, a second pulse signal is used for driving the power switch to be switched on; the frequency of the first pulse signal is greater than that of the second pulse signal. Therefore, the system has the advantages of reducing noise and explosion risks and improving the working stability of the system.

Description

Technical Field

[0001] The present application relates to the technical field of cooking appliances, and more particularly, to an electromagnetic heating control method and an electromagnetic heating system. Background Art

[0002] In the prior art, the electromagnetic heating system of an induction cooker usually adopts a method of cooperating an IGBT (Insulated Gate Bipolar Transistor, insulated gate bipolar transistor, also known as a power switch) with a resonant heating unit to complete the heating work of the induction cooker. Specifically, the power switch is turned off during the wave loss stage (the stop heating interval) and turned on during the non-wave loss stage (the heating interval); or, the power switch is micro-conducted with a small pulse width during a short transition interval before switching to the non-wave loss stage (i.e., a short time period near the starting point of the non-wave loss stage in the wave loss stage), is normally turned on after switching to the non-wave loss stage, and is turned off during the non-transition time period in the wave loss stage.

[0003] The above driving control method of the power switch still has obvious defects such as excessive noise when applied to the electromagnetic heating of an induction cooker. First, the electromagnetic heating system generates a magnetic field during the LC oscillation process, and the magnetic field generates a magnetic force acting on the cookware, thereby causing the cookware to vibrate. When switching from the wave loss stage to the non-wave loss stage, the bus voltage energy accumulated in the wave loss stage keeps the collector side of the power switch in a high voltage state, and the instantaneous large current caused by the high voltage at the moment when the power switch is turned on will make the vibration more intense, the noise volume larger, and the risk of explosion also increases; second, the changing magnetic field generated during the oscillation process causes the electrons inside the cookware to flow, thereby generating electromagnetic eddy currents. The electromagnetic eddy currents can heat the cookware, but at the same time, they will also cause the cookware to vibrate, thereby generating stronger noise. When a user places a cookware on the induction cooker, the increase in load will also cause part of the unconsumed bus voltage energy to be converted into sound, resulting in increased noise.

[0004] Therefore, there is an urgent need for a new electromagnetic heating control method for an induction cooker, so that the electromagnetic heating system can enter a state of normally and stably driving the power switch under a lower bus voltage state, thereby effectively reducing the noise and the risk of explosion. Summary of the Invention

[0005] The purpose of the present application is to provide an electromagnetic heating control method and an electromagnetic heating system. Each driving cycle of the wave-loss method is divided into a discharge stage and a heating stage. By driving the power switch to be slightly conductive throughout the discharge stage, the bus voltage at the collector terminal of the power switch can be reduced to below 310V during the discharge stage, and the envelope waveform follows the voltage waveform after the AC mains is rectified. Furthermore, the induction cooker can gradually switch between having power and no power, achieving a lower noise and smoother heating drive. Therefore, the present application has the advantages of reducing noise, strong working stability, high reliability, and improving the user experience.

[0006] The embodiments of the present application are implemented as follows:

[0007] In a first aspect of an embodiment of the present application, an electromagnetic heating control method is provided. This method is applied to an electromagnetic heating system, which includes a power switch and a zero-crossing detection unit. The zero-crossing detection unit is configured to detect the zero-crossing signal of the mains. The electromagnetic heating control method includes: Based on the zero-crossing signal of the mains and the preset power of the induction cooker, using the wave-loss method as the power control method, each driving cycle of the wave-loss method is provided with a discharge stage and a heating stage; during the discharge stage, driving the power switch to conduct with a first pulse signal; during the heating stage, driving the power switch to conduct with a second pulse signal; the frequency of the first pulse signal is greater than the frequency of the second pulse signal.

[0008] In one embodiment, the discharge stage includes a pre-discharge stage and a post-discharge stage. During the pre-discharge stage, driving the power switch to conduct with a first pulse signal includes: During the pre-discharge stage, driving the power switch with a first pulse signal, and the pulse width of the first pulse signal remains unchanged; during the post-discharge stage, driving the power switch with a transition pulse signal whose pulse width gradually increases; the pulse width of the transition pulse signal gradually increases from the pulse width of the first pulse signal to the pulse width of the second pulse signal.

[0009] In one embodiment, the discharge stage includes a pre-discharge stage and a post-discharge stage. During the discharge stage, driving the power switch to conduct with a first pulse signal includes: During the pre-discharge stage, driving the power switch with a first pulse signal, and the pulse width of the first pulse signal remains unchanged; during the post-discharge stage, driving the power switch with a transition pulse signal with an equal pulse width; the pulse width of the transition pulse signal is greater than the pulse width of the first pulse signal and less than the pulse width of the second pulse signal.

[0010] In one embodiment, after driving the power switch to conduct with the second pulse signal, the method further includes: Based on the oscillation frequency collected during the current heating stage, determining the initial pulse width of the first pulse signal in the next driving cycle.

[0011] In one embodiment, after determining the initial pulse width of the first pulse signal in the next driving period based on the oscillation frequency collected in the current heating stage, the electromagnetic heating control method further includes: correcting the initial pulse width based on the voltage parameters collected in the current heating stage to obtain the driving pulse width of the first pulse signal corresponding to the next discharging stage, where the voltage parameters include at least one of the current reverse voltage value, the current voltage value, and the current step value.

[0012] In one embodiment, the current reverse voltage value is: the voltage value at one end of the collector of the power switch during the off period; correcting the initial pulse width based on the voltage parameters collected in the current heating stage to obtain the driving pulse width of the first pulse signal corresponding to the next discharging stage includes: calculating a reverse voltage compensation value based on the current reverse voltage value and its corresponding reverse voltage compensation coefficient; calculating the driving pulse width of the first pulse signal corresponding to the next discharging stage based on the reverse voltage compensation value and the initial pulse width.

[0013] In one embodiment, the current step value is: the voltage value at one end of the collector of the power switch at the moment of conduction; correcting the initial pulse width based on the voltage parameters collected in the current heating stage to obtain the driving pulse width of the first pulse signal corresponding to the next discharging stage includes: calculating a step compensation value based on the current step value and its corresponding step compensation coefficient; calculating the driving pulse width of the first pulse signal corresponding to the next discharging stage based on the step compensation value and the initial pulse width before update.

[0014] In one embodiment, the current voltage value is the mains voltage value; correcting the initial pulse width based on the voltage parameters collected in the current heating stage to obtain the driving pulse width of the first pulse signal corresponding to the next discharging stage includes: calculating a voltage compensation value based on the current voltage value and its corresponding voltage compensation coefficient; calculating the driving pulse width of the first pulse signal corresponding to the next discharging stage based on the voltage compensation value and the initial pulse width before update.

[0015] In one embodiment, determining the initial pulse width of the first pulse signal in the next driving period based on the oscillation frequency collected in the current heating stage includes: if the oscillation frequency is greater than the first threshold, determining the initial pulse width as the first pulse width; if the oscillation frequency is less than or equal to the first threshold and greater than the second threshold, determining the initial pulse width as the second pulse width; if the oscillation frequency is less than or equal to the second threshold and greater than the third threshold, determining the initial pulse width as the third pulse width; if the oscillation frequency is less than or equal to the third threshold, determining the initial pulse width as the fourth pulse width.

[0016] In a second aspect of the embodiments of the present application, an electromagnetic heating system is provided. The system includes a rectifying and filtering unit, a zero-crossing voltage detection unit, a resonant heating unit, a synchronization circuit, a power switch, and a main control chip. Among them, two input terminals of the rectifying and filtering unit are connected to the live wire and the neutral wire of the AC mains; two input terminals of the zero-crossing voltage detection unit are respectively connected to the live wire and the neutral wire; one end of the resonant heating unit is connected to the output terminal of the rectifying and filtering unit; the synchronization circuit is arranged at both ends of the resonant heating unit and oscillates synchronously with the resonant heating unit; the collector of the power switch is connected to the other end of the resonant heating unit; one end of the main control chip is connected to the output terminal of the zero-crossing voltage detection unit, and the other end of the main control chip is connected to the base of the power switch through a power switch driving unit; the main control chip is configured to: based on the zero-crossing signal of the mains and the preset power of the induction cooker, divide each driving cycle of the power switch into a discharging stage and a heating stage; in the discharging stage, drive the power switch to conduct slightly at a high frequency with a first pulse signal; in the heating stage, drive the power switch to conduct normally with a second pulse signal; the frequency of the first pulse signal is greater than the frequency of the second pulse signal.

[0017] The beneficial effects of the present application compared with the prior art are as follows:

[0018] The present application can solve the problems of large vibration and large noise of the cookware caused by excessive voltage and current at the moment when the power switch of the existing induction cooker conducts. Based on the preset power of the induction cooker and the zero-crossing signal of the mains detected by the zero-crossing detection unit, the present application uses the wave-loss method as the power control method, and divides each driving cycle of the wave-loss method into a discharging stage and a heating stage. Thus, in the entire discharging stage, by driving the power switch to conduct slightly, the bus voltage at the collector end of the power switch can be reduced to below 310V in the discharging stage, and the envelope waveform fluctuates following the voltage waveform after the AC mains is rectified. The induction cooker can start with a low bus voltage when the alternating current passes through zero, thereby reducing noise and improving the stability and reliability of the electromagnetic heating system; the electromagnetic heating control method provided by the present application enables the induction cooker to gradually switch between having power and no power, realizing a smoother heating drive with lower noise, effectively reducing noise, and enhancing the user experience. Description of the Drawings

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0020] Figure 1 It is a schematic structural diagram of an electromagnetic heating system provided by an embodiment of the present application;

[0021] Figure 2 Schematic diagram of the structure of an electromagnetic heating circuit provided by an embodiment of the present application;

[0022] Figure 3 Schematic flowchart of an electromagnetic heating control method provided by an embodiment of the present application;

[0023] Figure 4 Schematic flowchart of an electromagnetic heating control method provided by an embodiment of the present application;

[0024] Figure 5 Schematic diagram of the comparison between multi - power drive signals and mains waveforms provided by an embodiment of the present application;

[0025] Figure 6 Schematic flowchart of the detailed process of step S240 provided by an embodiment of the present application;

[0026] Figure 7 Schematic diagram of the comparison between mains voltage, back - voltage and drive signals at 1 / 2 power provided by an embodiment of the present application.

[0027] Reference numerals: 1 - electromagnetic heating system; 2 - electromagnetic heating circuit; 11 - mains power supply; 12 - zero - crossing voltage detection unit; 13 - main control chip; 14 - drive module; 141 - power switch drive unit; 142 - power switch; 15 - resonant heating unit; 16 - synchronization circuit; 17 - rectification and filtering unit. Detailed implementation manners

[0028] Next, the technical solutions in the embodiments of the present application will be described in conjunction with the accompanying drawings in the embodiments of the present application.

[0029] Similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. At the same time, in the description of the present application, terms such as "first", "second", etc. are only used for differential description and cannot be construed as indicating or implying relative importance.

[0030] Next, the technical solutions of the present application will be described clearly and completely in conjunction with the accompanying drawings.

[0031] Please refer to Figure 1 , Figure 1 Schematic diagram of the structure of the electromagnetic heating system 1 provided by an embodiment of the present application. As Figure 1As shown, the electromagnetic heating system 1 includes a mains power supply 11, a zero-crossing voltage detection unit 12, a main control chip 13, a drive module 14, a resonant heating unit 15 and a synchronization circuit 16. Among them, the zero-crossing voltage detection unit 12 is connected to the mains power supply 11, and the zero-crossing voltage detection unit 12 is configured to detect the zero-crossing voltage signal of the mains power supply 11, that is, the mains zero-crossing signal; the mains power supply 11 is connected to the resonant heating unit 15, and the mains power supply 11 is configured to supply power to the resonant heating unit 15; the synchronization circuit 16 is connected to the resonant heating unit 15, and the synchronization circuit 16 is configured to oscillate synchronously with the resonant heating unit 15; the main control chip 13 is connected to the drive module 14, the zero-crossing voltage detection unit 12 and the synchronization circuit 16, and the main control chip 13 is configured to obtain the mains zero-crossing signal and detect the oscillation frequency, and output a pulse control signal to the drive module 14; the drive module 14 is connected to the resonant heating unit 15, and the drive module 14 is configured to control the resonant heating unit 15 to perform resonant operation based on the pulse control signal.

[0032] Please refer to Figure 2 , Figure 2 which is a schematic structural diagram of the electromagnetic heating circuit 2 provided by an embodiment of the present application. As Figure 2 shown, each electrical component in the electromagnetic heating system 1 is connected to form an electromagnetic heating circuit 2. The electromagnetic heating system 1 further includes a rectification and filtering unit 17, and the rectification and filtering unit 17 is configured to: perform rectification and filtering on the AC mains output by the mains power supply 11 and output direct current to the resonant heating unit 15.

[0033] Specifically, the live wire (L wire) and the neutral wire (N wire) of the mains power supply 11 are respectively connected to two input ends of the rectification and filtering unit 17, the output end of the rectification and filtering unit 17 is connected to one end of the resonant heating unit 15, and the resonant heating unit 15 includes a resonant coil L2 and a resonant capacitor C1 connected in parallel. The drive module 14 includes a power switch drive unit 141 and a power switch 142. The power switch 142 can be an IGBT. The collector of the power switch 142 is connected to the other end of the resonant heating unit 15, the emitter of the power switch 142 is grounded, the gate of the power switch 142 is connected to the power switch drive unit 141, and the power switch 142 is used to control the resonant heating unit 15 to perform resonant operation; the synchronization circuit is arranged at both ends of the resonant heating unit 15 and oscillates synchronously with the resonant heating unit 15 ( Figure 2The synchronization circuit 16) is not shown; the live wire (L wire) and the neutral wire (N wire) of the mains power supply 11 are also respectively connected to the two input terminals of the zero-crossing voltage detection unit 12, and the output terminal of the zero-crossing voltage detection unit 12 is connected to the input terminal of the main control chip 13; the input terminal of the main control chip 13 is connected to the synchronization circuit 16, and the other end of the main control chip 13 is connected to the base of the power switch 142 through the power switch driving unit 141. The main control chip 13 can directly detect the oscillation frequency of the synchronization circuit 16 or detect the oscillation frequency of the synchronization circuit 16 through an externally connected frequency detection unit; the main control chip 13 can also output a pulse signal to control the power switch 142 to conduct according to different pulse widths and different frequencies, and the main control chip 13 is configured to execute the electromagnetic heating control method provided in any one of the following embodiments.

[0034] Please refer to Figure 3 , Figure 3 which is a schematic flow chart of the electromagnetic heating control method provided by an embodiment of the present application. The electromagnetic heating control method is applied to the electromagnetic heating system 1 and is executed by the main control chip 13. The electromagnetic heating system includes a zero-crossing voltage detection unit, a power switch, a resonant heating unit, and a main control chip. As Figure 3 shown, the electromagnetic heating control method includes the following steps S110 to S130.

[0035] S110: Based on the mains zero-crossing signal and the preset power of the induction cooker, the wave-drop method is used as the power control method, and each drive cycle of the wave-drop method is provided with a discharge stage and a heating stage;

[0036] The mains zero-crossing signal refers to the voltage signal detected by the zero-crossing voltage detection unit and output to the main control chip when the voltage value of the AC mains passes through 0; the preset power of the induction cooker refers to the parameter for controlling its intermittent heating after the electromagnetic heating system starts the resonant heating operation based on preset parameters or information such as the user's preselected heating gear. In this step, the main control chip uses the wave-drop method as the power control method, and based on the detected mains zero-crossing signal and the preset power of the induction cooker, determines the start time of each drive cycle in the wave-drop method and divides each drive cycle into two stages, namely the discharge stage and the heating stage. Among them, the duration ratio of the heating stage in the entire drive cycle corresponds to the preset power of the induction cooker. For example, when the preset power is 1 / 4 power, the duration ratio of the heating stage in the entire drive cycle is 1 / 4, and the duration ratio of the discharge stage in the entire drive cycle is 3 / 4.

[0037] S120: In the discharge stage, drive the power switch to conduct with the first pulse signal;

[0038] The first pulse signal refers to the driving signal for driving the power switch to conduct by the main control chip during the discharging stage. During the entire discharging stage, the main control chip continuously drives the power switch to conduct slightly with the first pulse signal having a relatively large frequency, so that the collector terminal of the power switch continuously consumes the energy of the bus voltage during the wave-loss period (i.e., the discharging stage), and the bus voltage at the collector terminal can fluctuate following the voltage waveform after the rectification of the AC mains.

[0039] S120: During the heating stage, drive the power switch to conduct with the second pulse signal.

[0040] After entering the heating stage, the main control chip continuously drives the power switch to conduct normally with the second pulse signal having a relatively small frequency. The frequency of the second pulse signal is less than that of the first pulse signal. The frequency of the second pulse signal is determined according to parameters such as the preset power of the induction cooker. The power switch conducts normally based on the second pulse signal during the heating stage, so that the oscillation frequency of the resonant heating unit is maintained within the normal operating frequency range, and the electromagnetic heating system can normally achieve the heating function.

[0041] Based on the above solution, the present application can solve the problems of large pot vibration and large noise caused by excessive voltage and current at the moment when the power switch of the existing induction cooker conducts. The present application divides each driving cycle of the wave-loss method into a discharging stage and a heating stage, so that during the entire discharging stage, in the way of driving the power switch to conduct slightly, the bus voltage at the collector terminal of the power switch can be reduced to below 310V during the discharging stage, and the envelope waveform follows the voltage waveform after the rectification of the AC mains. The voltage peak value after the power switch conducts slightly is between 310V and 0V. At the end of the discharging stage (i.e., the time when entering the heating stage), the bus voltage drops to near the mains voltage, making the starting effect of the power switch better when entering the heating stage. The induction cooker enters the heating stage at the zero-crossing of the alternating current, which can realize starting with a low bus voltage, thereby reducing noise and improving the stability and reliability of the electromagnetic heating system. Compared with the situation where the power switch does not conduct at all during the wave-loss period, the way that the power switch of the present application continuously conducts slightly during the entire discharging stage can effectively reduce the bus voltage at the collector terminal and make it change with the voltage waveform of the AC mains. Since the start time of the heating stage is also at the zero-crossing of the voltage of the alternating current, at the moment when the electromagnetic heating system enters the heating stage from the discharging stage, it can realize starting with a low bus voltage. When the main control chip drives the power switch to conduct normally, the instantaneous current flowing through the collector terminal of the power switch is small, the noise generated by the induction cooker is small, and the electromagnetic heating system can realize a more stable and smooth drive when switching between having and not having heating power.

[0042] Please refer to Figure 4 , Figure 4Schematic flow chart of an electromagnetic heating control method provided by an embodiment of the present application. The electromagnetic heating control method is applied to an electromagnetic heating system and executed by a main control chip. The electromagnetic heating system includes a zero-crossing voltage detection unit, a power switch, a resonant heating unit, and a main control chip. As Figure 4 shown, the electromagnetic heating control method includes the following steps S210 to S240.

[0043] S210: Based on the zero-crossing signal of the commercial power supply and the preset power of the induction cooker, the wave-loss method is used as the power control method. Each driving cycle of the wave-loss method has a discharge stage and a heating stage.

[0044] The zero-crossing signal of the commercial power supply refers to the voltage signal detected by the zero-crossing voltage detection unit and output to the main control chip when the voltage value of the AC commercial power supply passes through zero; the preset power of the induction cooker refers to the parameter that controls the intermittent heating of the induction cooker after the electromagnetic heating system starts the resonant heating operation based on preset parameters or information such as the user's preselected heating gear. In this step, the main control chip uses the wave-loss method as the power control method, determines the start time of each driving cycle in the wave-loss method based on the detected zero-crossing signal of the voltage and the preset power of the induction cooker, and divides each driving cycle into two stages, namely the discharge stage and the heating stage.

[0045] Among them, the duration ratio of the heating stage in the entire driving cycle corresponds to the preset power of the induction cooker. Please refer to Figure 5 , Figure 5 Schematic diagram of the multi-power drive signal - commercial power waveform comparison provided by an embodiment of the present application. As Figure 5 shown, the induction cooker enters the heating stage when the AC commercial power supply passes through zero, and can achieve low bus voltage startup. The main control chip divides the entire driving cycle into four time periods T1 to T4 according to the zero-crossing signal of the voltage, and then determines the duration ratio of the wave-loss time period (i.e., the discharge stage) in the entire driving cycle based on the preset power of the induction cooker, so that the main control chip can perform segmented control on the conduction and cutoff of the power switch according to the power demand of the induction cooker.

[0046] Taking the preset power as 3 / 4 power as an example, the duration ratio of the heating stage in the entire driving cycle is 3 / 4, and the duration ratio of the discharge stage in the entire driving cycle is 1 / 4, that is Figure 5 as shown, the T1 time period is the discharge stage (wave-loss time period), the T2 to T4 time periods are the heating stage, and then enter the next driving cycle; taking the preset power as 1 / 2 power as an example, the duration ratio of the heating stage in the entire driving cycle is 1 / 2, and the duration ratio of the discharge stage in the entire driving cycle is 1 / 2, that is Figure 5The time period from T1 to T2 shown is the discharge stage (wave loss period), and the time period from T3 to T4 is the heating stage. Taking the preset power as 1 / 4 power as an example, the duration ratio of the heating stage in the entire driving cycle is 1 / 4, and the duration ratio of the discharge stage in the entire driving cycle is 3 / 4, that is Figure 5 The time period from T1 to T3 shown is the discharge stage (wave loss period), and the time period T4 is the heating stage.

[0047] Among them, during the discharge stage of each driving cycle of the main control chip, the pulse signal output to the power switch is usually a high-frequency pulse of 0 to 5 us, and the frequency is between 32 KHz and 60 KHz. The pulse width and frequency of the pulse signal output by the main control chip are fine-tuned in real time based on the cookware parameters or voltage and current, so that during the discharge stage of the electromagnetic heating system, while being able to consume the bus voltage energy at the collector terminal of the power switch, it maintains a very low power output state; during the heating stage of each driving cycle of the main control chip, the pulse signal output to the power switch is usually a pulse greater than 5 us, and the frequency is between 18 KHz and 30 KHz. The pulse width and frequency of the pulse signal output by the main control chip are determined based on the cookware parameters or voltage and current, and the target power (preset power) of the induction cooker, so that the electromagnetic heating system controls the power switch and the resonant heating unit to enter the normal working state during the heating stage. Optionally, the frequency of the first pulse signal is about twice as high as that of the second pulse signal.

[0048] S220: During the discharge stage, drive the power switch to conduct with the first pulse signal.

[0049] During the entire discharge stage, the main control chip continuously drives the power switch to conduct slightly with the first pulse signal with a larger frequency, so that the collector terminal of the power switch continuously consumes the bus voltage energy during the wave loss period (i.e., the discharge stage). Since the start moment of the heating stage is also at the moment when the alternating current voltage passes through zero, when the electromagnetic heating system enters the heating stage from the discharge stage, it can achieve low bus voltage startup. When the main control chip drives the power switch to conduct normally, the instantaneous current flowing through the collector terminal of the power switch is small, and the noise generated by the induction cooker is small.

[0050] In one embodiment, the discharge stage includes a pre-discharge stage and a post-discharge stage. During the pre-discharge stage, the main control chip drives the power switch to conduct slightly with the first pulse signal, and the pulse width of the first pulse signal remains unchanged; during the post-discharge stage, the main control chip drives the power switch to conduct with a transition pulse signal whose pulse width gradually increases. Among them, the pulse width of the transition pulse signal gradually increases from the pulse width of the first pulse signal to the pulse width of the second pulse signal. From the discharge stage to the heating stage, the electromagnetic heating system can achieve a more stable and smooth conversion when switching between having and not having heating power (actually, the process of the electromagnetic heating system adjusting from a very low power output to a normal power output).

[0051] As Figure 5 shown, taking the preset power as 1 / 4 power as an example, the T5 stage in T1, T2 and T3 is the pre-discharge stage, and the main control chip drives the power switch to be slightly conductive with the first pulse signal; the T6 stage in T3 is the post-discharge stage, and the main control chip drives the power switch to be conductive with a transition pulse signal whose pulse width gradually increases. In the T6 stage in T3, the pulse width of the transition pulse signal gradually increases from the pulse width of the first pulse signal to the pulse width of the second pulse signal. Specifically, the pulse width of the transition pulse signal at the starting point of the T6 stage (the start time of the T6 stage) is greater than or equal to the pulse width of the first pulse signal, and the pulse width of the transition pulse signal at the end point of the T6 stage (the end time of the T6 stage) is less than or equal to the pulse width of the second pulse signal; in the T4 stage, the main control chip drives the power switch to be normally conductive with the second pulse signal. For the waveform changes of the pulse signals (drive signals) corresponding to other preset powers, please refer to the above details and will not be elaborated here.

[0052] In another embodiment, the discharge stage includes a pre-discharge stage and a post-discharge stage. In the pre-discharge stage, the main control chip drives the power switch to be slightly conductive with the first pulse signal, and the pulse width of the first pulse signal remains unchanged; in the post-discharge stage, the main control chip drives the power switch with a transition pulse signal having an equal pulse width; the pulse width of the transition pulse signal is greater than the pulse width of the first pulse signal and less than the pulse width of the second pulse signal.

[0053] Based on the above scheme, the main control chip further divides the discharge stage into a pre-discharge stage and a post-discharge stage based on the preset duration corresponding to the post-discharge stage. The main control chip drives the power switch to be slightly conductive with the first pulse signal having a constant pulse width in the pre-discharge stage to continuously release the bus voltage energy at the collector terminal of the power switch, so that the envelope waveform of the bus voltage at the collector terminal follows the voltage waveform after the AC mains is rectified. The starting point of the bus voltage in the post-discharge stage (the start time of the T6 stage) is the smaller value; in the post-discharge stage, the main control chip drives the power switch to be conductive with a transition pulse signal whose pulse width is between the width of the first pulse signal and the width of the second pulse signal and whose pulse width gradually increases or is constant, so that the power switch realizes a soft start from the wave-loss period (discharge stage) to the non-wave-loss period (heating stage), that is, gradually switches from the slightly conductive state to the normal conductive state, and the pulse current (inrush current) flowing through the power switch is always small, thereby realizing a lower-noise and smoother drive of the electromagnetic heating system.

[0054] S230: In the heating stage, drive the power switch to be conductive with the second pulse signal.

[0055] After entering the heating stage, the main control chip continuously drives the power switch to conduct normally with a second pulse signal having a relatively small frequency. The frequency of the second pulse signal is less than that of the first pulse signal. The frequency of the second pulse signal is determined according to parameters such as the preset power of the induction cooker. The power switch conducts normally based on the second pulse signal in the heating stage, enabling the electromagnetic heating system to output normal power for normal heating.

[0056] S240: Based on the oscillation frequency and voltage parameters collected in the current heating stage, determine the driving pulse width of the first pulse signal in the next driving cycle.

[0057] After entering the heating stage within the current driving cycle, in order to obtain a more stable and reliable first pulse signal for the discharging stage in the next driving cycle, the main control chip needs to collect the working state parameters of the electromagnetic heating system in the current heating stage to update the driving pulse width of the first pulse signal in the next driving cycle in real time.

[0058] Please refer to Figure 6 , Figure 6 which is a detailed flowchart of step S240 provided in an embodiment of the present application. The working state parameters include the oscillation frequency, the current voltage value, the current step value, and the current back pressure value. Among them, the current back pressure value is the voltage value at one end of the collector of the power switch during the off period; the current step value is the voltage value at one end of the collector of the power switch at the moment of conduction; the current voltage value is the mains voltage value. As Figure 6 shown, step S240 includes the following sub-steps S241 to step S245.

[0059] S241: Based on the oscillation frequency collected in the current heating stage, determine the initial pulse width of the first pulse signal in the next driving cycle.

[0060] In this step, if the oscillation frequency is greater than the first threshold, the main control chip determines the initial pulse width as the first pulse width; if the oscillation frequency is less than or equal to the first threshold and greater than the second threshold, the main control chip determines the initial pulse width as the second pulse width; if the oscillation frequency is less than or equal to the second threshold and greater than the third threshold, the main control chip determines the initial pulse width as the third pulse width; if the oscillation frequency is less than or equal to the third threshold, the main control chip determines the initial pulse width as the fourth pulse width.

[0061] In steps S242 to step S244, the main control chip calculates the compensation values corresponding to each voltage parameter based on the current voltage value, the current step value, and the current back pressure value respectively. Specifically:

[0062] S242: Calculate the back pressure compensation value based on the current back pressure value and its corresponding back pressure compensation coefficient;

[0063] In this step, multiply the current back pressure value by the back pressure compensation coefficient to obtain the back pressure compensation value.

[0064] S243: Calculate the step compensation value based on the current step value and its corresponding step compensation coefficient;

[0065] In this step, multiply the current step value by the step compensation coefficient to obtain the step compensation value.

[0066] S244: Calculate the voltage compensation value based on the current voltage value and its corresponding voltage compensation coefficient;

[0067] In this step, multiply the current voltage value by the voltage compensation coefficient to obtain the voltage compensation value.

[0068] Finally, in step S245, the main control chip adds the back pressure compensation value, the step compensation value, the voltage compensation value and the initial pulse width, and calculates the driving pulse width of the first pulse signal corresponding to the next discharge stage.

[0069] In other embodiments of the present application, the specific calculation method of the driving pulse width further includes: determining the initial pulse width of the first pulse signal in the next driving cycle based on the oscillation frequency collected in the current heating stage; correcting the initial pulse width based on the voltage parameters collected in the current heating stage to obtain the driving pulse width of the first pulse signal corresponding to the next discharge stage, and the voltage parameters include at least one of the current back pressure value, the current voltage value and the current step value. Among them, the specific details of determining the initial pulse width based on the oscillation frequency have been introduced in detail in Figure 6 the corresponding embodiment and will not be elaborated here.

[0070] When the voltage parameter is only the current back pressure value, the main control chip calculates the back pressure compensation value based on the current back pressure value and its corresponding back pressure compensation coefficient; then, the main control chip calculates the driving pulse width of the first pulse signal corresponding to the next discharge stage based on the back pressure compensation value and the initial pulse width.

[0071] When the voltage parameter is only the current step value, the main control chip calculates the step compensation value based on the current step value and its corresponding step compensation coefficient; then, the main control chip calculates the driving pulse width of the first pulse signal corresponding to the next discharge stage based on the step compensation value and the initial pulse width before updating.

[0072] When the voltage parameter is only the current voltage value, the main control chip calculates the voltage compensation value based on the current voltage value and its corresponding voltage compensation coefficient; then, the main control chip calculates the driving pulse width of the first pulse signal corresponding to the next discharge stage based on the voltage compensation value and the initial pulse width before updating.

[0073] The main control chip can also calculate the driving pulse width based on two voltage parameters and the initial pulse width. Taking the voltage parameters as the current reverse voltage value and the current voltage value, the main control chip calculates the voltage compensation value based on the current voltage value and its corresponding voltage compensation coefficient; the main control chip calculates the reverse voltage compensation value based on the current reverse voltage value and its corresponding reverse voltage compensation coefficient; finally, the main control chip calculates the driving pulse width of the first pulse signal corresponding to the next discharge stage based on the voltage compensation value, the reverse voltage compensation value and the initial pulse width before update. More combination methods for the main control chip to calculate the driving pulse width based on multiple voltage parameters will not be elaborated here. For specific details, please refer to the above embodiments.

[0074] After calculating the driving pulse width of the first pulse signal corresponding to the next discharge stage, at the end of the heating stage of the current driving cycle, the main control chip performs the heating control work of the next driving cycle, that is, enters step S220 again, enters the discharge stage of the next driving cycle, and drives the power switch to conduct with the first pulse signal. The pulse width of the first pulse signal is the driving pulse width calculated by the main control chip in the most recent heating stage.

[0075] Please refer to Figure 7 , Figure 7 is a schematic diagram of the comparison of the mains - reverse voltage - driving signal waveforms at 1 / 2 power provided by an embodiment of the present application. As Figure 7 shown, under the action of the continuous micro - conduction pulses during the entire discharge stage (wave - loss stage), the bus voltage at the collector terminal of the power switch will drop from the relatively high and stable 310V, and the envelope waveform fluctuates following the voltage waveform after the rectification of the AC mains. The bus voltage has dropped to near the mains voltage at the start moment of the post - discharge stage. Further, if the electromagnetic heating system starts heating (enters the heating stage) at the zero - crossing of the AC mains, the effect of a low bus voltage at the collector terminal at the moment of heating start can be achieved, thereby reducing noise and improving the stability and reliability of the operation of the electromagnetic heating system.

[0076] Based on the above solution, in the present application, during the entire discharge stage, the power switch is continuously driven to be slightly conductive with high-frequency short pulses, so as to reduce the bus voltage at the collector terminal of the power switch. And when the AC mains voltage passes through zero, the heating stage is entered, so as to achieve the effect of low bus voltage at the collector terminal at the moment of heating startup, thereby reducing the noise and the risk of explosion. In the present application, by collecting the oscillation frequency and voltage parameters during the heating stage, the driving pulse width of the first pulse signal corresponding to the next discharge stage is accurately calculated and updated, so as to improve the stability and reliability of the electromagnetic heating system. In the present application, the discharge stage is divided into a pre-discharge stage and a post-discharge stage, and during the post-discharge stage, the power switch is driven to conduct with a transition pulse signal whose pulse width gradually increases, so that when the output power of the induction cooker is gradually switched from zero to a certain value, a lower noise and smoother drive are achieved, effectively improving the stability of the electromagnetic heating system and enhancing the user experience.

[0077] The methods disclosed in several embodiments provided in the present application can also be implemented in other ways. The method embodiments described above are merely illustrative. For example, the flowcharts and block diagrams in the accompanying drawings show the possible architectures, functions, and operations of methods and computer program products according to multiple embodiments of the present application. In this regard, each block in the flowchart or block diagram may represent a module, a program segment, or a part of code, and the module, program segment, or part of code contains one or more executable instructions for implementing the specified logical function. In some alternative implementations, the functions marked in the blocks may occur in a different order than marked in the accompanying drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in the reverse order, depending on the functions involved. It should also be noted that each block in the block diagram and / or flowchart, as well as the combination of blocks in the block diagram and / or flowchart, can be implemented by a dedicated hardware-based system for performing the specified functions or actions, or can be implemented by a combination of dedicated hardware and computer instructions.

[0078] An embodiment of the present application provides a computer-readable storage medium, and the storage medium stores a computer program. The computer program can be executed by a main control chip to complete the electromagnetic heating control method.

[0079] If the functions are implemented in the form of software function modules and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a part of this technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods in various embodiments of this application. The foregoing storage medium includes: various media that can store program codes, such as USB flash drives, mobile hard disks, read-only memories (ROM, Read-Only Memory), random access memories (RAM, Random Access Memory), magnetic disks, or optical discs.

[0080] The foregoing are only the preferred embodiments of this application and are not used to limit this application. For those skilled in the art, this application may have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this application shall be included within the protection scope of this application.

Claims

1. An electromagnetic heating control method, characterized in that, The method is applied to an electromagnetic heating system, which includes a power switch and a zero-crossing detection unit configured to detect the zero-crossing signal of the mains power; the electromagnetic heating control method includes: Based on the zero-crossing signal of the mains power and the preset power of the induction cooker, using the wave-loss method as the power control method, and each driving cycle of the wave-loss method has a discharge stage and a heating stage; In the discharge stage, drive the power switch to conduct with a first pulse signal; In the heating stage, drive the power switch to conduct with a second pulse signal; the frequency of the first pulse signal is greater than that of the second pulse signal.

2. The electromagnetic heating control method according to claim 1, characterized in that The discharge stage includes a pre-discharge stage and a post-discharge stage. Driving the power switch to conduct with a first pulse signal in the pre-discharge stage includes: In the pre-discharge stage, drive the power switch with a first pulse signal, and the pulse width of the first pulse signal remains unchanged; In the post-discharge stage, drive the power switch with a transition pulse signal whose pulse width gradually increases; the pulse width of the transition pulse signal gradually increases from the pulse width of the first pulse signal to the pulse width of the second pulse signal.

3. The electromagnetic heating control method according to claim 1, wherein The discharge stage includes a pre-discharge stage and a post-discharge stage. Driving the power switch to conduct with a first pulse signal in the discharge stage includes: In the pre-discharge stage, drive the power switch with a first pulse signal, and the pulse width of the first pulse signal remains unchanged; In the post-discharge stage, drive the power switch with a transition pulse signal having an equal pulse width; the pulse width of the transition pulse signal is greater than the pulse width of the first pulse signal and less than the pulse width of the second pulse signal.

4. The electromagnetic heating control method according to any one of claims 1 to 3, characterized in that, After driving the power switch to conduct with the second pulse signal, the method further includes: Determine the initial pulse width of the first pulse signal in the next driving cycle based on the oscillation frequency collected in the current heating stage.

5. The electromagnetic heating control method according to claim 4, wherein After determining the initial pulse width of the first pulse signal in the next driving cycle based on the oscillation frequency collected in the current heating stage, the method further includes: Based on the voltage parameters collected in the current heating stage, correct the initial pulse width to obtain the driving pulse width of the first pulse signal corresponding to the next discharge stage, where the voltage parameters include at least one of the current reverse voltage value, the current voltage value, and the current step value.

6. The electromagnetic heating control method according to claim 5, characterized in that, The current reverse voltage value is: the voltage value at one end of the collector of the power switch during the off period; based on the voltage parameters collected in the current heating stage, correcting the initial pulse width to obtain the driving pulse width of the first pulse signal corresponding to the next discharge stage includes: Calculate the reverse voltage compensation value based on the current reverse voltage value and its corresponding reverse voltage compensation coefficient; Calculate the driving pulse width of the first pulse signal corresponding to the next discharge stage based on the reverse voltage compensation value and the initial pulse width.

7. The electromagnetic heating control method according to claim 5, wherein The current step value is: the voltage value at one end of the collector of the power switch at the moment of conduction; the correction of the initial pulse width based on the voltage parameters collected in the current heating stage to obtain the driving pulse width of the first pulse signal corresponding to the next discharge stage includes: Calculating a step compensation value based on the current step value and its corresponding step compensation coefficient; Calculating the driving pulse width of the first pulse signal corresponding to the next discharge stage based on the step compensation value and the initial pulse width before update.

8. The electromagnetic heating control method according to claim 5, characterized in that, The current voltage value is the mains voltage value; the correction of the initial pulse width based on the voltage parameters collected in the current heating stage to obtain the driving pulse width of the first pulse signal corresponding to the next discharge stage includes: Calculating a voltage compensation value based on the current voltage value and its corresponding voltage compensation coefficient; Calculating the driving pulse width of the first pulse signal corresponding to the next discharge stage based on the voltage compensation value and the initial pulse width before update.

9. The electromagnetic heating control method according to claim 4, wherein, The determination of the initial pulse width of the first pulse signal within the next driving cycle based on the oscillation frequency collected in the current heating stage includes: If the oscillation frequency is greater than a first threshold, determining the initial pulse width as a first pulse width; If the oscillation frequency is less than or equal to the first threshold and greater than a second threshold, determining the initial pulse width as a second pulse width; If the oscillation frequency is less than or equal to the second threshold and greater than a third threshold, determining the initial pulse width as a third pulse width; If the oscillation frequency is less than or equal to the third threshold, determining the initial pulse width as a fourth pulse width.

10. An electromagnetic heating system, characterized in that, Including: A rectification and filtering unit, the two input ends of which are connected to the live wire and the neutral wire of the AC mains; A voltage zero-crossing detection unit, the two input ends of which are respectively connected to the live wire and the neutral wire; A resonant heating unit, one end of which is connected to the output end of the rectification and filtering unit; A synchronization circuit, which is arranged at both ends of the resonant heating unit and oscillates synchronously with the resonant heating unit; A power switch, the collector of which is connected to the other end of the resonant heating unit; and, A main control chip, one end of which is connected to the output end of the voltage zero-crossing detection unit, and the other end of which is connected to the base of the power switch through a power switch driving unit; The main control chip is configured to: divide each driving cycle of the power switch into a discharge stage and a heating stage based on the mains zero-crossing signal and the preset power of the induction cooker; in the discharge stage, driving the power switch to conduct microscopically at a high frequency with a first pulse signal; In the heating stage, driving the power switch to conduct normally with a second pulse signal; The frequency of the first pulse signal is greater than the frequency of the second pulse signal.

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