Bridgeless three-level induction heating device and control method thereof

Abstract

The invention discloses a bridgeless three-level induction heating device and a control method thereof, and relates to the field of induction heating. The bridgeless three-level induction heating device comprises a filtering module, a bridgeless three-level inversion module, an LLC resonance module and a coil module. The filtering module is connected with a power grid to filter high-frequency noise of power grid signals; the bridgeless three-level inversion module is connected with the filtering module so as to receive the power grid signal cleaned by the filtering module, and the bridgeless three-level inversion module converts the power grid signal into high-frequency alternating current and outputs the high-frequency alternating current; the bridgeless three-level inversion module does not comprise a rectifier bridge; the LLC resonance module is connected with the bridgeless three-level module so as to receive the high-frequency alternating current, and the LLC resonance module generates a resonance effect based on the high-frequency alternating current so as to realize energy transmission; the coil module is connected with the LLC resonance module, and the coil module generates an alternating current electromagnetic field based on the high-frequency alternating current to realize induction heating. By omitting a rectifier bridge, the circuit structure is simplified, and the loss in the energy conversion process is reduced.

Description

Technical Field

[0001] The present invention relates to the field of induction heating, and in particular to a bridgeless three-level induction heating device and a control method thereof. Background Art

[0002] Induction heating technology is a heating method that uses an alternating electromagnetic field to generate eddy currents in metal or other conductive materials to cause the material to heat itself.

[0003] However, existing induction heating technologies all include a diode rectification link, but diode rectification will reduce energy transmission efficiency. Summary of the invention

[0004] In order to solve the above problems, the present application discloses a bridgeless three-level induction heating device, comprising: A filter module, wherein the filter module is connected to the power grid to filter out high-frequency noise of power grid signals; A bridgeless three-level inverter module, wherein the bridgeless three-level inverter module is connected to the filter module to receive the grid signal cleaned by the filter module, and the bridgeless three-level inverter module converts the grid signal into a high-frequency alternating current output; the bridgeless three-level inverter module does not include a rectifier bridge; An LLC resonance module, wherein the LLC resonance module is connected to the bridgeless three-level module to receive the high-frequency alternating current, and the LLC resonance module generates a resonance effect based on the high-frequency alternating current to achieve energy transmission; A coil module is connected to the LLC resonance module, and the coil module generates an alternating current electromagnetic field based on the high-frequency alternating current to achieve induction heating.

[0005] Among them, it also includes a control module, which is connected to the bridgeless three-level inverter module and the LLC resonance module; the control module can adjust the heating power by adjusting the frequency and phase output by the bridgeless three-level inverter module; the control module can achieve soft switching operation by adjusting the parameters of the LCC resonance module.

[0006] Wherein, the control module is an MCU unit, and the MCU controls the working mode of the bridgeless three-level inverter module, and the working mode includes frequency conversion control, phase shift control and hybrid control.

[0007] Among them, it also includes a sampling module; one end of the sampling module is connected to the coil module to obtain the induced current value and the temperature value, and the other end of the sampling module is connected to the control module to send the induced current value and the temperature value to the control module; the control module adjusts the working state of the bridgeless three-level inverter module and the LLC resonance module based on the induced current value and the temperature value to realize negative feedback control.

[0008] Wherein, the bridgeless three-level inverter module is a full-bridge inverter or a half-bridge inverter.

[0009] Among them, when the bridgeless three-level inverter module is a half-bridge inverter, the bridgeless three-level inverter module includes four driving units, the four driving units independently drive four switching tubes, and every two driving units control a pair of reverse switching tubes to achieve independent driving.

[0010] Wherein, the LLC resonant module includes a resonant inductor , coil induction equivalent inductance and resonant capacitor An LLC series resonance is formed; the operating frequency of the LLC resonance module is a first resonance frequency or a second resonance frequency, and the operating frequency of the LLC resonance module is selected based on the load of the coil module. The operating frequency is the first resonance frequency when the load is low, and the operating frequency is the second resonance frequency when the load is high.

[0011] Wherein, the coil module is a multi-coil structure, and the multi-coil structure is connected in series one by one or in parallel one by one.

[0012] The present application also provides a control method applied to any one of the above bridgeless three-level induction heating devices, comprising the following steps: The filter module filters out high-frequency noise of the power grid signal; The bridgeless three-level inverter module receives grid signals and directly converts them into high-frequency AC power; The LLC resonant module receives high-frequency AC power and generates a resonance effect to achieve energy transmission; The coil module receives high-frequency alternating current to generate a high-frequency alternating current induction magnetic field, which forms eddy current on the induction workpiece to achieve induction heating.

[0013] Beneficial effects of the present application: The present application discloses a bridgeless three-level induction heating device and a control method thereof, which relates to the field of induction heating; the bridgeless three-level induction heating device comprises a filter module, a bridgeless three-level inverter module, an LLC resonance module and a coil module; the filter module is connected to the power grid to filter out high-frequency noise of the power grid signal; the bridgeless three-level inverter module is connected to the filter module to receive the power grid signal cleaned by the filter module, and the bridgeless three-level inverter module converts the power grid signal into high-frequency alternating current output; the bridgeless three-level inverter module does not include a rectifier bridge; the LLC resonance module is connected to the bridgeless three-level module to receive high-frequency alternating current, and the LLC resonance module generates a resonance effect based on the high-frequency alternating current to realize energy transmission; the coil module is connected to the LLC resonance module, and the coil module generates an alternating electromagnetic field based on the high-frequency alternating current to realize induction heating. By eliminating the rectifier bridge, the circuit structure is simplified and the loss in the energy conversion process is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a structural schematic diagram of a first embodiment of a bridgeless three-level induction heating device of the present application; Figure 2 A schematic diagram showing a comparison between a power grid signal and high-frequency alternating current according to an embodiment of the present application; Figure 3 This is a structural schematic diagram of a second embodiment of a bridgeless three-level induction heating device of the present application; Figure 4 It is a structural schematic diagram of the third embodiment of the bridgeless three-level induction heating device of the present application; Figure 5 for Figure 4 The bridgeless three-level inverter module in FIG. 1 is a schematic diagram of a half-bridge inverter structure; Figure 6 for Figure 4 The bridgeless three-level inverter module in FIG. 1 is a structural schematic diagram of a full-bridge inverter; Figure 7 1 is a flow chart of an embodiment of a control method of a bridgeless three-level induction heating device of the present application. DETAILED DESCRIPTION

[0015] The following are specific embodiments of the present application and combined with the accompanying drawings to further describe the technical solution of the present application, but the present application is not limited to these embodiments.

[0016] Existing induction heating devices all include a rectifier structure, but the rectifier structure will cause certain losses; for example, if the rectifier structure is a rectifier diode, under high current working conditions, the conduction voltage drop of the rectifier diode will cause energy loss. In addition, the setting of the rectifier structure increases the number of components, increases the manufacturing cost and complexity, and makes the system more difficult to maintain and manage.

[0017] To solve the above problems, the present application provides a bridgeless three-level induction heating device, such as Figure 1 As shown, Figure 1 It is a structural schematic diagram of the first embodiment of the bridgeless three-level induction heating device of the present application; the bridgeless three-level induction heating device includes a filter module 11, a bridgeless three-level inverter module 12, an LLC resonance module 13 and a coil module 14.

[0018] The filter module 11 is connected to the power grid to filter out the high-frequency noise of the power grid signal; the filter module 11 can ensure the cleanliness of the input signal, reduce electromagnetic interference, and protect the subsequent circuit from the high-frequency noise in the power grid; the power grid signal is industrial frequency alternating current; the filter module can use a high-frequency differential mode filter, which can provide normal filtering function while reducing the space occupied by the filter module, which is conducive to miniaturization; in one embodiment, the filter module 11 includes a differential mode high-frequency filter inductor, which is used to filter out the high-frequency signal disturbance to the grid-side current generated by the high-frequency tube.

[0019] The bridgeless three-level inverter module 12 is connected to the filter module 11 to receive the grid signal cleaned by the filter module 11, and the bridgeless three-level inverter module 12 converts the grid signal into a high-frequency AC output; that is, the grid signal cleaned by the filter module 11 is directly input into the bridgeless three-level inverter module 12, and the bridgeless three-level inverter module 12 directly converts the grid signal into a high-frequency AC output; that is, the bridgeless three-level inverter module 12 directly converts the industrial frequency AC into high-frequency AC, and there is no DC side energy storage link in the middle; the bridgeless three-level inverter module 12 does not include a rectifier bridge, thereby avoiding the loss problem caused by a traditional rectifier diode, optimizing the topological structure, and improving efficiency.

[0020] like Figure 2 As shown, Figure 2 A schematic diagram showing the comparison between a grid signal and high-frequency alternating current according to an embodiment of the present application.

[0021] Curve 1 is the grid signal, and curve 2 is the high-frequency AC signal; the frequency of the high-frequency AC is higher than that of the grid signal, and the faster the magnetic field generated by the coil module 14 changes, the stronger the eddy current is; by adjusting the structure and parameters of the bridgeless three-level inverter module 12, the output high-frequency AC signal can be adjusted, thereby realizing the adjustment of the eddy current of the coil module 14.

[0022] The LLC resonant module 13 is connected to the bridgeless three-level module 12 to receive high-frequency alternating current. The LLC resonant module 13 generates a resonance effect based on the high-frequency alternating current to achieve energy transmission. In one embodiment, the LLC resonant module 13 is composed of an inductor, a capacitor, and a coil to form a series resonant network, which can achieve full soft switching operation of the switch tube, reduce device losses, and improve efficiency. In other embodiments, the LLC resonant module 14 can also be composed of a parallel resonant network, which is not limited here.

[0023] The coil module 14 is connected to the LLC resonance module 13. The coil module 14 generates an AC electromagnetic field based on high-frequency AC power to achieve induction heating. The coil module 14 receives high-frequency AC power and generates a high-frequency induction magnetic field based on the electromagnetic effect, thereby forming an eddy current on the coil module 14 to achieve induction heating. The coil module 14 can be connected in parallel or in series with multiple coils to meet different heating requirements.

[0024] In summary, the bridgeless three-level induction heating device disclosed in the present application includes a filter module, a bridgeless three-level inverter module, an LLC resonant module and a coil module; the filter module is connected to the power grid to filter out the high-frequency noise of the power grid signal; the bridgeless three-level inverter module is connected to the filter module to receive the power grid signal cleaned by the filter module, and the bridgeless three-level inverter module converts the power grid signal into a high-frequency alternating current output; the bridgeless three-level inverter module does not include a rectifier bridge; the LLC resonant module is connected to the bridgeless three-level module to receive high-frequency alternating current, and the LLC resonant module generates a resonance effect based on high-frequency alternating current to achieve energy transmission; the coil module is connected to the LLC resonant module, and the coil module generates an alternating electromagnetic field based on high-frequency alternating current to achieve induction heating. By eliminating the rectifier bridge, the circuit structure is simplified and the loss in the energy conversion process is reduced.

[0025] In one embodiment, if Figure 3 As shown, Figure 3 It is a schematic structural diagram of a second embodiment of a bridgeless three-level induction heating device of the present application; the bridgeless three-level induction heating device further includes a control module 15 .

[0026] The control module 15 is connected to the bridgeless three-level inverter module 12 and the LLC resonant module 13; the control module 15 can adjust the heating power by adjusting the frequency and phase output by the bridgeless three-level inverter module 12; the control module 15 can realize soft switching operation by adjusting the parameters of the LCC resonant module 13; for example, the LLC resonant module 13 includes an inductor and a capacitor, and the inductor value and the capacitor value are adjusted based on the high-frequency alternating current received by the LLC resonant module 13 to realize soft switching operation, thereby ensuring that the voltage or current is close to zero during the switching process.

[0027] The control module 15 is an MCU unit. The MCU controls the working mode of the bridgeless three-level inverter module 12. The working modes include frequency conversion control, phase shift control and hybrid control. The working principles of the three working modes are described in detail below: The MCU unit changes the resonant frequency by adjusting the frequency output by the bridgeless three-level inverter module 12, and further adjusts the current applied to the coil module 14, thereby controlling the heating power.

[0028] The MCU unit changes the on-time ratio of the switch tube by adjusting the phase angle of the output of the bridgeless three-level inverter module 12, thereby changing the effective value of the output voltage; through phase shift control, the switch tube can be turned on or off under zero voltage or zero current state, reducing switching losses.

[0029] The MCU unit combines the advantages of frequency conversion control and phase shift control, flexibly adjusting the frequency and phase angle according to the actual load conditions to achieve more precise power regulation while maintaining high efficiency and reliability.

[0030] The MCU unit includes I / O, ADC, PWM, USART and CAN interfaces to facilitate data acquisition, communication and other control tasks; the MCU unit can be composed of chips such as DSP or FPGA, without any limitation.

[0031] In one embodiment, if Figure 4 As shown, Figure 4 Schematic diagram of the structure of the third embodiment of the bridgeless three-level induction heating device of the present application; the bridgeless three-level induction heating device also includes a sampling module 16 .

[0032] One end of the sampling module 16 is connected to the coil module 14 to obtain the induced current value and the temperature value, and the other end of the sampling module 16 is connected to the control module 15 to send the induced current value and the temperature value to the control module 15; the control module 15 adjusts the working state of the bridgeless three-level inverter module 12 and the LLC resonant module 13 based on the induced current value and the temperature value to realize negative feedback control.

[0033] The control module 15 adjusts the output frequency of the bridgeless three-level inverter module 12 according to the induced current value and the temperature value to adjust the heating power; the control module 15 changes the effective value of the output voltage by adjusting the output phase angle of the bridgeless three-level inverter module 12; the control module 15 can also adjust the parameters of the LLC resonant module 13, such as the inductance and capacitance values, to achieve soft switching operation to ensure that the voltage or current is close to zero during the switching process.

[0034] Through continuous sampling and adjustment, a closed-loop control system is formed, which enables the system to automatically adjust back to the predetermined state when it deviates from the set target. Based on the real-time collected data, the system can respond in time and adjust the heating power and frequency to ensure the stability and accuracy of the heating process.

[0035] In summary, by introducing the sampling module 16 and the control module 15 to realize negative feedback control, the bridgeless three-level induction heating device not only improves the accuracy and stability of the heating process, but also enhances the safety and adaptability of the system, making the device more intelligent and efficient.

[0036] In one embodiment, the bridgeless three-level inverter module is a full-bridge inverter or a half-bridge inverter; Figure 5 , Figure 6 As shown; Figure 5 for Figure 4 The bridgeless three-level inverter module in FIG. 1 is a schematic diagram of a half-bridge inverter structure; Figure 6 for Figure 4 The bridgeless three-level inverter module in FIG. 1 is a structural diagram of a full-bridge inverter.

[0037] When the bridgeless three-level inverter module is a half-bridge inverter, the bridgeless three-level inverter module includes four drive units, and the four drive units independently drive four switch tubes, and each drive unit is responsible for driving one switch tube; every two drive units control a pair of reverse switch tubes, that is, one drive unit is responsible for driving a forward switch tube, and the other drive unit is responsible for driving a reverse switch tube, so as to realize independent driving; this independent drive design can ensure that only one switch tube is turned on at any time, and the other switch tube is turned off, so as to avoid the occurrence of shoot-through phenomenon.

[0038] Through the design that four drive units independently drive four switch tubes, and every two drive units control a pair of reverse switch tubes, the half-bridge inverter realizes precise control of the switch tubes, improves the efficiency and reliability of the system, reduces electromagnetic interference, and facilitates the debugging and maintenance of the system. This design is particularly suitable for induction heating applications that require high-precision control and high efficiency.

[0039] In one embodiment, the LLC resonant module 13 includes a resonant inductor , coil induction equivalent inductance and resonant capacitor The LLC series resonance is formed; the operating frequency of the LLC resonance module 13 is the first resonance frequency or the second resonance frequency. The operating frequency of the LLC resonance module 13 is selected based on the load of the coil module 14. The operating frequency is the first resonance frequency when the load is low, and the operating frequency is the second resonance frequency when the load is high. By adjusting the resonant inductance , coil induction equivalent inductance and resonant capacitor parameters to ensure that the circuit reaches the optimal resonance state at the selected resonant frequency and realizes soft switching operation.

[0040]

[0041] Under light load conditions, using the first resonant frequency can reduce switching losses and improve efficiency; under heavy load conditions, using the second resonant frequency can better match the load and maintain efficient operation; by selecting the first resonant frequency or the second resonant frequency under different load conditions by the LLC resonant module 13, precise control of the system can be achieved, the efficiency and stability of the system can be improved, the loss can be reduced, and the device can be protected. This design is particularly suitable for induction heating applications that require efficient, stable and reliable operation.

[0042] The switch tube operates in the ZVS state, i.e., the zero voltage switching state, which can significantly reduce the switching loss and improve the efficiency and reliability of the system.

[0043] In one embodiment, the coil module 14 is a multi-coil structure, which is connected in series or in parallel one by one, and can form distributed multi-point heating to expand the heating area; through series connection, the voltage of multiple coils can be accumulated, and the series structure is easy to expand, and the total voltage can be increased by increasing the number of coils to adapt to greater load requirements. Parallel connection can increase the total current capacity. If a coil fails, other coils can still continue to work, which improves the redundancy and reliability of the system.

[0044] By adopting a multi-coil structure that is connected in series or in parallel one by one, it can be flexibly adapted to different heating needs. Series connection is suitable for applications that require high voltage, uniform current distribution and simplified control, while parallel connection is suitable for applications that require high current, independent control and high redundancy. This design makes the system more flexible, reliable and easy to maintain.

[0045] The present application also provides a control method that can be applied to the bridgeless three-level induction heating device in any of the above embodiments, such as Figure 7 As shown, Figure 7 This is a flow chart of an embodiment of a control method of a bridgeless three-level induction heating device of the present application, comprising the following steps: Step S11: The filtering module filters out high-frequency noise of the grid signal; by filtering, the subsequent bridgeless three-level inverter module can be protected from the influence of the grid noise and its service life can be extended.

[0046] Step S12: The bridgeless three-level inverter module receives the grid signal and directly converts the grid signal into high-frequency alternating current; the rectifier bridge is omitted, the loss problem caused by the rectifier diode is avoided, and the efficiency is improved.

[0047] Step S13: The LLC resonant module receives high-frequency alternating current and generates a resonance effect to achieve energy transmission. By selecting appropriate resonance parameters, the circuit can present ideal impedance characteristics at the resonance frequency, thereby maximizing energy transmission to the coil and improving heating efficiency. Through the resonance effect, soft switching operation can be achieved, switching losses can be reduced, and energy transmission efficiency can be improved.

[0048] Step S14: The coil module receives high-frequency alternating current to generate a high-frequency alternating current induction magnetic field, forming eddy current on the induction workpiece to achieve induction heating; the sampling module monitors the current and temperature in real time, and transmits the data to the control module for adjustment to achieve precise control.

[0049] The above description is only an implementation method of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly used in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A bridgeless three-level induction heating device, characterized in that: include: A filter module, wherein the filter module is connected to the power grid to filter out high-frequency noise of power grid signals; A bridgeless three-level inverter module, wherein the bridgeless three-level inverter module is connected to the filter module to receive the grid signal cleaned by the filter module, and the bridgeless three-level inverter module converts the grid signal into a high-frequency alternating current output; the bridgeless three-level inverter module does not include a rectifier bridge; An LLC resonance module, wherein the LLC resonance module is connected to the bridgeless three-level module to receive the high-frequency alternating current, and the LLC resonance module generates a resonance effect based on the high-frequency alternating current to achieve energy transmission; A coil module is connected to the LLC resonance module, and the coil module generates an alternating current electromagnetic field based on the high-frequency alternating current to achieve induction heating.

2. The bridgeless three-level induction heating device according to claim 1, characterized in that: It also includes a control module, which is connected to the bridgeless three-level inverter module and the LLC resonance module; the control module can adjust the heating power by adjusting the frequency and phase output by the bridgeless three-level inverter module; the control module can achieve soft switching operation by adjusting the parameters of the LCC resonance module.

3. The bridgeless three-level induction heating device according to claim 2, characterized in that: The control module is an MCU unit, and the MCU controls the working mode of the bridgeless three-level inverter module, and the working mode includes frequency conversion control, phase shift control and hybrid control.

4. The bridgeless three-level induction heating device according to claim 3, characterized in that: It also includes a sampling module; one end of the sampling module is connected to the coil module to obtain the induced current value and the temperature value, and the other end of the sampling module is connected to the control module to send the induced current value and the temperature value to the control module; the control module adjusts the working state of the bridgeless three-level inverter module and the LLC resonance module based on the induced current value and the temperature value to realize negative feedback control.

5. The bridgeless three-level induction heating device according to claim 4, characterized in that: The bridgeless three-level inverter module is a full-bridge inverter or a half-bridge inverter.

6. The bridgeless three-level induction heating device according to claim 5, characterized in that: When the bridgeless three-level inverter module is a half-bridge inverter, the bridgeless three-level inverter module includes four driving units, the four driving units independently drive four switch tubes, and every two driving units control a pair of reverse switch tubes to achieve independent driving.

7. The bridgeless three-level induction heating device according to claim 5, characterized in that: The LLC resonant module includes a resonant inductor , coil induction equivalent inductance and resonant capacitor An LLC series resonance is formed; the operating frequency of the LLC resonance module is a first resonance frequency or a second resonance frequency, and the operating frequency of the LLC resonance module is selected based on the load of the coil module. The operating frequency is the first resonance frequency when the load is low, and the operating frequency is the second resonance frequency when the load is high.

8. The bridgeless three-level induction heating device according to claim 7, characterized in that: The coil module is a multi-coil structure, and the multi-coil structure is connected in series one by one or in parallel one by one.

9. A control method applied to the bridgeless three-level induction heating device according to any one of claims 1 to 8, characterized in that: The steps include: The filter module filters out high-frequency noise of the power grid signal; The bridgeless three-level inverter module receives grid signals and directly converts them into high-frequency AC power; The LLC resonant module receives high-frequency AC power and generates a resonance effect to achieve energy transmission; The coil module receives high-frequency alternating current to generate a high-frequency alternating current induction magnetic field, which forms eddy current on the induction workpiece to achieve induction heating.

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