Frequency tracking and regulation system and method for induction heating

Abstract

The embodiment of the present invention provides a frequency tracking and regulating system and method for induction heating, the system comprising: a voltage waveform collector, a current waveform collector, an FPGA module, a precise clock, a DSP processor, and a PWM control circuit; the voltage waveform collector is used to collect the voltage switching waveform of the induction heating circuit; the current waveform collector is used to collect the current waveform of the induction heating circuit; the FPGA module is used to receive the voltage switching waveform and the current waveform, when the T1 rising edge of the voltage switching waveform arrives, the FPGA module is provided with a counter, sends a new PWM control frequency ω to the PWM control circuit, the PWM control circuit controls the heating circuit to heat according to the new PWM control frequency ω, the DSP processor records the new PWM control frequency ω and continuously repeats the above steps, so as to realize real-time frequency tracking, solve the deviation from the resonance point caused by load changes, reduce the efficiency of induction heating, and realize efficient induction heating.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of digital heating technology, and in particular to a frequency tracking and regulating system and method for induction heating. Background Art

[0002] Modern induction heating basically uses the inductance in the resonant circuit to form an alternating electromagnetic field, which then forms eddy currents and hysteresis on the workpiece and then generates heat.

[0003] However, as heating progresses, the impedance changes, and providing a matching power frequency becomes a problem.

[0004] Therefore, how to provide a frequency tracking and adjustment solution for induction heating that can solve the impedance matching problem as heating proceeds and realize the power supply frequency acquisition and follow-up response tracking of induction heating is a technical problem that needs to be urgently solved by technical personnel in this field. Summary of the invention

[0005] To this end, an embodiment of the present invention provides a frequency tracking and adjustment system and method for induction heating, which can solve the impedance matching problem as heating proceeds, and realize the power supply frequency acquisition and follow-up response tracking of induction heating.

[0006] In order to achieve the above purpose, the embodiment of the present invention provides the following technical solutions:

[0007] In a first aspect, an embodiment of the present invention provides a frequency tracking and regulating system for induction heating, comprising:

[0008] Voltage waveform collector, current waveform collector, FPGA module, precision clock, DSP processor, PWM control circuit;

[0009] The voltage waveform collector is used to collect the voltage switching waveform of the induction heating circuit;

[0010] The current waveform collector is used to collect the current waveform of the induction heating circuit;

[0011] The FPGA module is used to receive the voltage switching waveform and the current waveform. When the rising edge T1 of the voltage switching waveform arrives, the FPGA module is provided with a counter connected to the precise clock, and starts counting pulses until the rising edge T3 ends. When the rising edge T2 arrives, the FPGA has a built-in counter, and starts inserting counting pulses until the rising edge T3 ends. The time from T1 to T3 is calculated according to the period of the counting pulse: t 1-3 =T counting pulse cycle time × n 1-3 , the time from the rising edge of T2 to the rising edge of T3: t 2-3 =T counting pulse cycle time × n 2-3;

[0012] The T1 rising edge is the moment when the first voltage of the voltage switching waveform changes from low to high when the device is powered on; the T2 rising edge is the moment when the second voltage of the voltage switching waveform changes from low to high when the device is powered on; the T3 rising edge is the moment when the first voltage of the current switching waveform changes from low to high when the device is powered on;

[0013] The DSP processor is used to receive the t calculated by the FPGA module 1-3 , the 2-3 If t 1-3 -t 桥臂死区时间 ≦t 2-3 , and t 1-3 ≧t 2-3 , then take t 2-3 time;

[0014] If 2-3 ≦T0 / 2, then the modified PWM control period T0 is: T new =T0+t 2-3 , giving the new PWM frequency: If 2-3 ≧T0 / 2, then the modified PWM control period T0 is: T new =t 2-3 , giving the new PWM frequency:

[0015] Give a new PWM operating frequency ω according to ω1 or ω2;

[0016] The new PWM control frequency ω is sent to the PWM control circuit, the PWM control circuit controls the heating circuit to perform heating according to the new PWM control frequency ω, and the DSP processor records the new PWM control frequency ω.

[0017] Preferably, the induction heating circuit comprises: a first thyristor, a second thyristor, a third thyristor, and a fourth thyristor;

[0018] The first thyristor and the second thyristor are connected in series at point A, and the third thyristor and the fourth thyristor are connected in series at point B.

[0019] Preferably, the point A is connected to the point B via a heater, a compensation capacitor, and an equivalent resistor in sequence;

[0020] The input end of the current waveform collector is connected to the connection point between the compensation capacitor and the equivalent capacitor.

[0021] Preferably, the point A is connected to the point B via a first resistor R1 and a second resistor R2 in sequence;

[0022] The input end of the voltage waveform collector is connected to the connection point of the first resistor R1 and the second resistor R2.

[0023] Preferably, when the device is powered on, the inductance of the heater and the capacitance of the compensation capacitor are input to the DSP processor through the human-machine interface. Calculate the LC natural resonant frequency ω 设定 , the DSP processor gives the resonant frequency ω0=75%×ω through the PWM control circuit 设定 The frequency gives the PWM wave cycle frequency, the cycle time is T0, or a DSP processor records the original working frequency to make the inverter work.

[0024] In a second aspect, an embodiment of the present invention provides a frequency tracking and regulating method for induction heating, which is applied to the frequency tracking and regulating system as described in any one of the first aspects above, comprising:

[0025] Receive the voltage switching waveform and the current waveform. When the rising edge of T1 of the voltage switching waveform arrives, the FPGA module is provided with a counter connected to the precise clock, and starts counting pulses until the rising edge of T3 ends. When the rising edge of T2 arrives, the FPGA has a built-in counter, and starts inserting counting pulses until the rising edge of T3 ends. The time from T1 to T3 is calculated according to the period of the counting pulse: t 1-3 =T counting pulse cycle time × n 1-3 , the time from the rising edge of T2 to the rising edge of T3: t 2-3 =T counting pulse cycle time × n 2-3 ;

[0026] The T1 rising edge is the moment when the first voltage of the voltage switching waveform changes from low to high when the device is powered on; the T2 rising edge is the moment when the second voltage of the voltage switching waveform changes from low to high when the device is powered on; the T3 rising edge is the moment when the first voltage of the current switching waveform changes from low to high when the device is powered on;

[0027] The DSP processor is used to receive the t calculated by the FPGA module 1-3 , the 2-3 If t 1-3 -t 桥臂死区时间 ≦t 2-3 , and t 1-3 ≧t 2-3 , then take t 2-3 time;

[0028] If 2-3 ≦T0 / 2, then the modified PWM control period T0 is: T new =T0+t 2-3, giving the new PWM frequency: If 2-3 ≧T0 / 2, then the modified PWM control period T0 is: T new =t 2-3 , giving the new PWM frequency:

[0029] Give a new PWM operating frequency ω according to ω1 or ω2;

[0030] The new PWM control frequency ω is sent to the PWM control circuit, the PWM control circuit controls the heating circuit to perform heating according to the new PWM control frequency ω, and the DSP processor records the new PWM control frequency ω.

[0031] The embodiment of the present invention provides a frequency tracking and regulating system for induction heating, comprising: a voltage waveform collector, a current waveform collector, an FPGA module, a precision clock, a DSP processor, and a PWM control circuit; the voltage waveform collector is used to collect the voltage switching waveform of the induction heating circuit; the current waveform collector is used to collect the current waveform of the induction heating circuit; the FPGA module is used to receive the voltage switching waveform and the current waveform, and when the T1 rising edge of the voltage switching waveform arrives, the FPGA module is provided with a counter, connected to the precision clock, and starts counting pulses until the T3 rising edge ends; when the T2 rising edge arrives, the FPGA has a built-in counter, starts inserting counting pulses, and ends at the T3 rising edge; the time from T1 to T3 is calculated according to the period of the counting pulse: t 1-3 =T counting pulse cycle time × n 1-3 , the time from the rising edge of T2 to the rising edge of T3: t 2-3 =T counting pulse cycle time × n 2-3 ; wherein the T1 rising edge is the moment when the first voltage of the voltage switching waveform changes from low to high when the device is powered on; the T2 rising edge is the moment when the second voltage of the voltage switching waveform changes from low to high when the device is powered on; the T3 rising edge is the moment when the first voltage of the current switching waveform changes from low to high when the device is powered on; the DSP processor is used to receive the t 1-3 , the 2-3 If t 1-3 -t 桥臂死区时间 ≦t 2-3 , and t 1-3 ≧t 2-3 , then take t 2-3 time;

[0032] If 2-3 ≦T0 / 2, then the modified PWM control period T0 is: T new =T0+t2-3 , giving the new PWM frequency: If 2-3 ≧T0 / 2, then the modified PWM control period T0 is: T new =t 2-3 , giving the new PWM frequency: According to ω1 or ω2, a new PWM operating frequency ω is given; the new PWM control frequency ω is sent to the PWM control circuit, the PWM control circuit controls the heating circuit to heat according to the new PWM control frequency ω, and the DSP processor records the new PWM control frequency ω. 10. By continuously repeating the above steps, real-time frequency tracking can be achieved, the deviation from the resonance point caused by load changes can be solved, the efficiency of induction heating can be reduced, and efficient induction heating can be achieved.

[0033] The frequency tracking and regulating method of induction heating provided by the embodiment of the present invention also has the above-mentioned beneficial effects, which will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the implementation methods or the description of the prior art. Obviously, the drawings in the following description are only exemplary, and for ordinary technicians in this field, other implementation drawings can be derived from the provided drawings without creative work.

[0035] The structures, proportions, sizes, etc. illustrated in this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with the technology. They are not used to limit the conditions under which the present invention can be implemented, and therefore have no substantial technical significance. Any structural modification, change in proportion or adjustment of size shall still fall within the scope of the technical contents disclosed in the present invention without affecting the effects and purposes that can be achieved by the present invention.

[0036] Figure 1 A schematic diagram of the structure of a frequency tracking and regulating system for induction heating is provided for an embodiment of the present invention;

[0037] Figure 2 A schematic diagram of voltage rise of a frequency tracking and regulating system for induction heating is provided for an embodiment of the present invention;

[0038] Figure 3 A schematic diagram of current rise of a frequency tracking and regulating system for induction heating is provided in accordance with an embodiment of the present invention;

[0039] Figure 4 A waveform analysis schematic diagram of a frequency tracking and regulation system for induction heating is provided for an embodiment of the present invention. DETAILED DESCRIPTION

[0040] The following is a description of the implementation of the present invention by specific embodiments. People familiar with the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Obviously, the described embodiments are 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 creative work are within the scope of protection of the present invention.

[0041] Please refer to Figure 1 , Figure 1 A schematic diagram of the structure of a frequency tracking and regulating system for induction heating is provided for an embodiment of the present invention; Figure 2 A schematic diagram of voltage rise of a frequency tracking and regulating system for induction heating is provided for an embodiment of the present invention; Figure 3 A schematic diagram of current rise of a frequency tracking and regulating system for induction heating is provided in accordance with an embodiment of the present invention; Figure 4 A waveform analysis schematic diagram of a frequency tracking and regulation system for induction heating is provided for an embodiment of the present invention.

[0042] In one embodiment of the present invention, the present invention provides a frequency tracking and regulating system for induction heating, comprising:

[0043] Voltage waveform collector, current waveform collector, FPGA module, precision clock, DSP processor, PWM control circuit;

[0044] The voltage waveform collector is used to collect the voltage switching waveform of the induction heating circuit;

[0045] The current waveform collector is used to collect the current waveform of the induction heating circuit;

[0046] The FPGA module is used to receive the voltage switching waveform and the current waveform. When the rising edge T1 of the voltage switching waveform arrives, the FPGA module is provided with a counter connected to the precise clock, and starts counting pulses until the rising edge T3 ends. When the rising edge T2 arrives, the FPGA has a built-in counter, and starts inserting counting pulses until the rising edge T3 ends. The time from T1 to T3 is calculated according to the period of the counting pulse: t 1-3 =T counting pulse cycle time × n 1-3 , the time from the rising edge of T2 to the rising edge of T3: t 2-3 =T counting pulse cycle time × n 2-3 ;

[0047] The T1 rising edge is the moment when the first voltage of the voltage switching waveform changes from low to high when the device is powered on; the T2 rising edge is the moment when the second voltage of the voltage switching waveform changes from low to high when the device is powered on; the T3 rising edge is the moment when the first voltage of the current switching waveform changes from low to high when the device is powered on;

[0048] The DSP processor is used to receive the t calculated by the FPGA module 1-3 , the 2-3 If t 1-3 -t 桥臂死区时间 ≦t 2-3 , and t 1-3 ≧t 2-3 , then take t 2-3 time;

[0049] If 2-3 ≦T0 / 2, then the modified PWM control period T0 is: T new =T0+t 2-3 , giving the new PWM frequency: If 2-3 ≧T0 / 2, then the modified PWM control period T0 is: T new =t 2-3 , giving the new PWM frequency:

[0050] Give a new PWM operating frequency ω according to ω1 or ω2;

[0051] The new PWM control frequency ω is sent to the PWM control circuit, the PWM control circuit controls the heating circuit to perform heating according to the new PWM control frequency ω, and the DSP processor records the new PWM control frequency ω.

[0052] Preferably, the induction heating circuit comprises: a first thyristor, a second thyristor, a third thyristor, and a fourth thyristor;

[0053] The first thyristor and the second thyristor are connected in series at point A, and the third thyristor and the fourth thyristor are connected in series at point B.

[0054] Preferably, the point A is connected to the point B via a heater, a compensation capacitor, and an equivalent resistor in sequence;

[0055] The input end of the current waveform collector is connected to the connection point between the compensation capacitor and the equivalent capacitor.

[0056] Preferably, the point A is connected to the point B via a first resistor R1 and a second resistor R2 in sequence;

[0057] The input end of the voltage waveform collector is connected to the connection point of the first resistor R1 and the second resistor R2.

[0058] Preferably, when the device is powered on, the inductance of the heater and the capacitance of the compensation capacitor are input to the DSP processor through the human-machine interface. Calculate the LC natural resonant frequency ω 设定 , the DSP processor gives the resonant frequency ω0=75%×ω through the PWM control circuit 设定 The frequency gives the PWM wave cycle frequency, the cycle time is T0, or a DSP processor records the original working frequency to make the inverter work.

[0059] That is to say, the inductance of the heater and the capacitance of the compensation capacitor are predicted and input into the DSP digital processor through the human-machine interface. Calculate the approximate LC inherent resonant frequency ω setting, and DSP gives the resonant frequency ω0=75%×ω setting frequency through the control circuit to give the PWM wave period frequency, and the period time is T0, or DSP records the original working frequency to make the inverter work; the voltage waveform collector collects the UAB voltage switching waveform through the R1 and R2 resistors via the high-speed optocoupler-voltage, and collects the rising edge waveform at T1 and T2; the current waveform collector collects the IAB current waveform flowing through the LC circuit through the high-frequency current sensor via the high-speed optocoupler-current, and collects the rising edge waveform at T3; and inputs them into the FPGA together.

[0060] In another embodiment of the present invention, the embodiment of the present invention provides a frequency tracking and adjustment method for induction heating, which is applied to the frequency tracking and adjustment system as described in any embodiment of the first aspect above, including:

[0061] Receive the voltage switching waveform and the current waveform. When the rising edge of T1 of the voltage switching waveform arrives, the FPGA module is provided with a counter connected to the precise clock, and starts counting pulses until the rising edge of T3 ends. When the rising edge of T2 arrives, the FPGA has a built-in counter, and starts inserting counting pulses until the rising edge of T3 ends. The time from T1 to T3 is calculated according to the period of the counting pulse: t 1-3 =T counting pulse cycle time × n 1-3 , the time from the rising edge of T2 to the rising edge of T3: t 2-3 =T counting pulse cycle time × n 2-3 ;

[0062] The T1 rising edge is the moment when the first voltage of the voltage switching waveform changes from low to high when the device is powered on; the T2 rising edge is the moment when the second voltage of the voltage switching waveform changes from low to high when the device is powered on; the T3 rising edge is the moment when the first voltage of the current switching waveform changes from low to high when the device is powered on;

[0063] The DSP processor is used to receive the t calculated by the FPGA module 1-3 , the 2-3 If t 1-3 -t 桥臂死区时间 ≦t 2-3 , and t 1-3 ≧t 2-3 , then take t 2-3 time;

[0064] If 2-3 ≦T0 / 2, then the modified PWM control period T0 is: T new =T0+t 2-3 , giving the new PWM frequency: If 2-3 ≧T0 / 2, then the modified PWM control period T0 is: T new =t 2-3 , giving the new PWM frequency:

[0065] Give a new PWM operating frequency ω according to ω1 or ω2;

[0066] The new PWM control frequency ω is sent to the PWM control circuit, the PWM control circuit controls the heating circuit to perform heating according to the new PWM control frequency ω, and the DSP processor records the new PWM control frequency ω.

[0067] Although the present invention has been described in detail above by general description and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements can be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. A frequency tracking and regulation system for induction heating, characterized in that: include: Voltage waveform collector, current waveform collector, FPGA module, precision clock, DSP processor, PWM control circuit; The voltage waveform collector is used to collect the voltage switching waveform of the induction heating circuit; The current waveform collector is used to collect the current waveform of the induction heating circuit; The FPGA module is used to receive the voltage switching waveform and the current waveform. When the rising edge T1 of the voltage switching waveform arrives, the FPGA module is provided with a counter connected to the precise clock and starts counting pulses until the rising edge T3 ends. When the rising edge of T2 arrives, the built-in counter of FPGA starts to insert counting pulses, which ends at the rising edge of T3. The time from T1 to T3 is calculated based on the period of the counting pulse: t 1-3 =T counting pulse cycle time × n 1-3 , the time from the rising edge of T2 to the rising edge of T3: t 2-3 =T counting pulse cycle time × n 2-3 ; The T1 rising edge is the moment when the first voltage of the voltage switching waveform changes from low to high when the device is powered on; the T2 rising edge is the moment when the second voltage of the voltage switching waveform changes from low to high when the device is powered on; the T3 rising edge is the moment when the first voltage of the current switching waveform changes from low to high when the device is powered on; The DSP processor is used to receive the t calculated by the FPGA module 1-3 , the 2-3 If t 1-3 -t 桥臂死区时间 ≦t 2-3 , and t 1-3 ≧t 2-3 , then take t 2-3 time; If 2-3 ≦T0 / 2, then the modified PWM control period T0 is: T new =T0+t 2-3 , giving the new PWM frequency: If 2-3 ≧T0 / 2, then the modified PWM control period T0 is: T new =t 2-3 , giving the new PWM frequency: Give a new PWM operating frequency ω according to ω1 or ω2; Sending a new PWM control frequency ω to the PWM control circuit, the PWM control circuit controls the heating circuit to perform heating according to the new PWM control frequency ω, and the DSP processor records the new PWM control frequency ω; When the device is powered on, the inductance of the heater and the capacitance of the compensation capacitor are input into the DSP processor through the human-machine interface. Calculate the LC natural resonant frequency ω 设定 , the DSP processor gives the resonant frequency ω0=75%×ω through the PWM control circuit 设定 The frequency gives the PWM wave cycle frequency, the cycle time is T0, or a DSP processor records the original working frequency to make the inverter work.

2. The frequency tracking and adjustment system according to claim 1, characterized in that: The induction heating circuit comprises: a first thyristor, a second thyristor, a third thyristor, and a fourth thyristor; The first thyristor and the second thyristor are connected in series at point A, and the third thyristor and the fourth thyristor are connected in series at point B.

3. The frequency tracking and adjustment system according to claim 2, characterized in that: The point A is connected to the point B via a heater, a compensation capacitor, and an equivalent resistor in sequence; The input end of the current waveform collector is connected to the connection point of the compensation capacitor and the equivalent capacitor.

4. The frequency tracking and adjustment system according to claim 2, characterized in that: The point A is connected to the point B via a first resistor R1 and a second resistor R2 in sequence; The input end of the voltage waveform collector is connected to the connection point of the first resistor R1 and the second resistor R2.

5. A frequency tracking and regulating method for induction heating, applied to the frequency tracking and regulating system according to any one of claims 1 to 4, characterized in that: include: The voltage switching waveform and the current waveform are received. When the rising edge T1 of the voltage switching waveform arrives, the FPGA module is provided with a counter connected to the precise clock and starts counting pulses until the rising edge T3 ends. When the rising edge of T2 arrives, the built-in counter of FPGA starts to insert counting pulses, which ends at the rising edge of T3. The time from T1 to T3 is calculated based on the period of the counting pulse: t 1-3 =T counting pulse cycle time × n 1-3 , the time from the rising edge of T2 to the rising edge of T3: t 2-3 =T counting pulse cycle time × n 2-3 ; The T1 rising edge is the moment when the first voltage of the voltage switching waveform changes from low to high when the device is powered on; the T2 rising edge is the moment when the second voltage of the voltage switching waveform changes from low to high when the device is powered on; the T3 rising edge is the moment when the first voltage of the current switching waveform changes from low to high when the device is powered on; The DSP processor is used to receive the t calculated by the FPGA module 1-3 , the 2-3 If t 1-3 -t 桥臂死区时间 ≦t 2-3 , and t 1-3 ≧t 2-3 , then take t 2-3 time; If 2-3 ≦T0 / 2, then the modified PWM control period T0 is: T new =T0+t 2-3 , giving the new PWM frequency: If 2-3 ≧T0 / 2, then the modified PWM control period T0 is: T new =t 2-3 , giving the new PWM frequency: Give a new PWM operating frequency ω according to ω1 or ω2; The new PWM control frequency ω is sent to the PWM control circuit, the PWM control circuit controls the heating circuit to perform heating according to the new PWM control frequency ω, and the DSP processor records the new PWM control frequency ω.

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