Bridgeless three-level induction heating device

Abstract

The utility model discloses a bridgeless three-level induction heating device, 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] This application relates to the field of induction heating, and in particular to a bridgeless three-level induction heating device. Background Technology

[0002] Induction heating technology is a heating method that uses alternating electromagnetic fields to generate eddy currents in metals or other conductive materials, causing the materials to heat up.

[0003] However, existing induction heating technologies all include diode rectification, which reduces energy transfer efficiency. Utility Model Content

[0004] To address the aforementioned problems, this application discloses a bridgeless three-level induction heating device, comprising:

[0005] A filtering module, which is connected to the power grid to filter out high-frequency noise in the power grid signal;

[0006] A 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 high-frequency AC output; the bridgeless three-level inverter module does not include a rectifier bridge;

[0007] LLC resonant module, the LLC resonant module is connected to the bridgeless three-level module to receive the high-frequency AC power, and the LLC resonant module generates a resonant effect based on the high-frequency AC power to realize energy transmission;

[0008] A coil module is connected to the LLC resonant module. The coil module generates an AC electromagnetic field based on the high-frequency AC current to achieve induction heating.

[0009] The system also includes a control module connected to the bridgeless three-level inverter module and the LLC resonant module. The control module can adjust the heating power by adjusting the frequency and phase output of the bridgeless three-level inverter module. The control module can also achieve soft-switching operation by adjusting the parameters of the LLC resonant module.

[0010] The control module is an MCU unit, which controls the working mode of the bridgeless three-level inverter module. The working mode includes frequency conversion control, phase shift control and hybrid control.

[0011] The system 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 resonant module based on the induced current value and the temperature value to achieve negative feedback control.

[0012] The bridgeless three-level inverter module is either a full-bridge inverter or a half-bridge inverter.

[0013] 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 transistors, and every two driving units control a pair of inverting switching transistors to achieve independent driving.

[0014] The LLC resonant module includes a resonant inductor. Equivalent inductance of coil and resonant capacitor An LLC series resonance is formed; the operating frequency of the LLC resonant module is either a first resonant frequency or a second resonant frequency. The operating frequency of the LLC resonant module is selected based on the load of the coil module. The operating frequency is the first resonant frequency when the load is low, and the operating frequency is the second resonant frequency when the load is high.

[0015] The coil module is a multi-coil structure, which can be connected in series or in parallel.

[0016] The beneficial effects of this application are as follows: This application discloses a bridgeless three-level induction heating device and its control method, relating to the field of induction heating. The bridgeless three-level induction heating device includes a filtering module, a bridgeless three-level inverter module, an LLC resonant module, and a coil module. The filtering module is connected to the power grid to filter out high-frequency noise from the power grid signal. The bridgeless three-level inverter module is connected to the filtering module to receive the power grid signal cleaned by the filtering module, and the bridgeless three-level inverter module converts the power grid signal into high-frequency AC 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 AC, and the LLC resonant module generates a resonant effect based on the high-frequency AC to achieve energy transfer. The coil module is connected to the LLC resonant module, and the coil module generates an AC electromagnetic field based on the high-frequency AC to achieve induction heating. By eliminating the rectifier bridge, the circuit structure is simplified, and the losses during the energy conversion process are reduced. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the first embodiment of the bridgeless three-level induction heating device of this application;

[0018] Figure 2 This is a schematic diagram comparing a power grid signal with high-frequency alternating current according to an embodiment of this application;

[0019] Figure 3 This is a schematic diagram of the structure of the second embodiment of the bridgeless three-level induction heating device of this application;

[0020] Figure 4 This is a schematic diagram of the third embodiment of the bridgeless three-level induction heating device of this application;

[0021] Figure 5 for Figure 4 The bridgeless three-level inverter module in the diagram is a structural schematic of a half-bridge inverter.

[0022] Figure 6 for Figure 4 The bridgeless three-level inverter module in the diagram is a structural schematic of a full-bridge inverter;

[0023] Figure 7 This is a schematic flowchart of an embodiment of the control method for the bridgeless three-level induction heating device of this application. Detailed Implementation

[0024] The following are specific embodiments of this application, which are described in conjunction with the accompanying drawings to further illustrate the technical solutions of this application. However, this application is not limited to these embodiments.

[0025] Existing induction heating devices all include a rectifier structure, but this structure introduces certain losses. For example, if the rectifier structure is a rectifier diode, the forward voltage drop of the diode under high current operating conditions will lead to energy loss. Furthermore, the addition of a rectifier structure increases the number of components, raising manufacturing costs and complexity, and making the system more difficult to maintain and manage.

[0026] To address the aforementioned problems, this application provides a bridgeless three-level induction heating device, such as... Figure 1 As shown, Figure 1 This is a schematic diagram of the structure of the first embodiment of the bridgeless three-level induction heating device of this application; the bridgeless three-level induction heating device includes a filter module 11, a bridgeless three-level inverter module 12, an LLC resonant module 13, and a coil module 14.

[0027] The filter module 11 is connected to the power grid to filter out high-frequency noise from the power grid signal. The filter module 11 can ensure the cleanliness of the input signal, reduce electromagnetic interference, and protect subsequent circuits from high-frequency noise in the power grid. The power grid signal is industrial frequency AC. The filter module can be a high-frequency differential mode filter, which can provide normal filtering function while reducing the space occupied by the filter module, which is beneficial for miniaturization. In one embodiment, the filter module 11 includes a differential mode high-frequency filter inductor for filtering out high-frequency signal disturbances to the grid-side current generated by the high-frequency tube.

[0028] 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. The bridgeless three-level inverter module 12 converts the grid signal into 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 high-frequency AC output. In other words, the bridgeless three-level inverter module 12 directly converts the power frequency AC into high-frequency AC, without any DC-side energy storage stage. The bridgeless three-level inverter module 12 does not include a rectifier bridge, thus avoiding the loss problem caused by traditional rectifier diodes, optimizing the topology, and improving efficiency.

[0029] like Figure 2 As shown, Figure 2 This is a schematic diagram comparing a power grid signal with high-frequency alternating current according to an embodiment of this application.

[0030] Curve 1 represents the grid signal, and curve 2 represents the high-frequency AC signal. The frequency of the high-frequency AC signal is higher than that of the grid signal. The faster the magnetic field generated by the coil module 14 changes, the stronger the eddy current becomes. By adjusting the structure and parameters of the bridgeless three-level inverter module 12, the output high-frequency AC signal can be adjusted, thereby achieving the adjustment of the eddy current of the coil module 14.

[0031] The LLC resonant module 13 is connected to the bridgeless three-level module 12 to receive high-frequency AC power. The LLC resonant module 13 generates a resonant effect based on the high-frequency AC power to achieve energy transfer. In one embodiment, the LLC resonant module 13 consists of an inductor, a capacitor, and a coil, forming a series resonant network, which can realize full-range soft-switching operation of the switching transistor, reduce device losses, and improve efficiency. In other embodiments, the LLC resonant module 14 can also be composed of a parallel resonant network, without any limitation.

[0032] The coil module 14 is connected to the LLC resonant 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 induced magnetic field based on electromagnetic effects, thereby forming eddy currents 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 adapt to different heating requirements.

[0033] In summary, the bridgeless three-level induction heating device disclosed in this 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 high-frequency noise from 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 converts the power grid signal into high-frequency AC 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 AC, and generates a resonant effect based on the high-frequency AC to achieve energy transfer. The coil module is connected to the LLC resonant module, and generates an AC electromagnetic field based on the high-frequency AC to achieve induction heating. By eliminating the rectifier bridge, the circuit structure is simplified, and losses during the energy conversion process are reduced.

[0034] In one embodiment, such as Figure 3 As shown, Figure 3 This is a schematic diagram of the structure of the second embodiment of the bridgeless three-level induction heating device of this application; the bridgeless three-level induction heating device also includes a control module 15.

[0035] 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 of the bridgeless three-level inverter module 12. The control module 15 can realize soft switching operation by adjusting the parameters of the LLC resonant module 13. For example, the LLC resonant module 13 includes an inductor and a capacitor. Based on the high-frequency AC power received by the LLC resonant module 13, the inductor value and the capacitor value are adjusted to realize soft switching operation and ensure that the voltage or current is close to zero during the switching process.

[0036] Control module 15 is an MCU unit. The MCU controls the operating modes of bridgeless three-level inverter module 12. The operating modes include frequency conversion control, phase shift control, and hybrid control. The working principles of the three operating modes are described in detail below:

[0037] The MCU unit adjusts the frequency of the output of the bridgeless three-level inverter module 12 to change the resonant frequency, and then adjusts the current applied to the coil module 14 to control the heating power.

[0038] The MCU unit adjusts the phase angle of the output of the bridgeless three-level inverter module 12 to change the on-time ratio of the switching transistor, thereby changing the effective value of the output voltage. Through phase shift control, the switching transistor can be turned on or off in a zero-voltage or zero-current state, reducing switching losses.

[0039] The MCU unit combines the advantages of frequency conversion control and phase shift control, and flexibly adjusts the frequency and phase angle according to the actual load conditions to achieve more precise power regulation while maintaining high efficiency and reliability.

[0040] The MCU unit includes I / O, ADC, PWM, USART and CAN interfaces, which facilitate data acquisition, communication and other control tasks; the MCU unit can be composed of chips such as DSP or FPGA, and there is no limitation here.

[0041] In one embodiment, such as Figure 4 As shown, Figure 4 This is a schematic diagram of the third embodiment of the bridgeless three-level induction heating device of this application; the bridgeless three-level induction heating device also includes a sampling module 16.

[0042] One end of the sampling module 16 is connected to the coil module 14 to obtain the induced current value and 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 temperature value to the control module 15; the control module 15 adjusts the working state of the bridgeless three-level inverter module 12 and LLC resonant module 13 based on the induced current value and temperature value to realize negative feedback control.

[0043] 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 regulate 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 achieve soft switching operation by adjusting the parameters of the LLC resonant module 13, such as the inductance and capacitance values, to ensure that the voltage or current is close to zero during the switching process.

[0044] Through continuous sampling and adjustment, a closed-loop control system is formed, enabling the system to automatically adjust back to the predetermined state when it deviates from the set target. Based on real-time data acquisition, the system can respond promptly, adjusting heating power and frequency to ensure the stability and accuracy of the heating process.

[0045] In summary, by introducing sampling module 16 and control module 15 to achieve 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 equipment more intelligent and efficient.

[0046] In one embodiment, the bridgeless three-level inverter module is a full-bridge inverter or a half-bridge inverter; such as Figure 5 , Figure 6 As shown; Figure 5 for Figure 4 The bridgeless three-level inverter module in the diagram is a structural schematic of a half-bridge inverter. Figure 6 for Figure 4 The bridgeless three-level inverter module in the diagram is a structural schematic of a full-bridge inverter.

[0047] When the bridgeless three-level inverter module is a half-bridge inverter, it includes four drive units. Each drive unit independently drives one switch transistor. Every two drive units control a pair of inverting switches, that is, one drive unit drives one forward switch transistor and the other drive one inverting switch transistor, thus achieving independent drive. This independent drive design ensures that only one switch transistor is turned on at any given time, while the other switch transistor is turned off, thereby avoiding shoot-through.

[0048] By using four drive units to independently drive four switching transistors, and with every two drive units controlling a pair of inverting switching transistors, the half-bridge inverter achieves precise control of the switching transistors, improving system efficiency and reliability, reducing electromagnetic interference, and facilitating system debugging and maintenance. This design is particularly suitable for induction heating applications requiring high-precision control and high efficiency.

[0049] In one embodiment, the LLC resonant module 13 includes a resonant inductor. Equivalent inductance of coil and resonant capacitor An LLC series resonance is formed; the operating frequency of the LLC resonant module 13 is either the first resonant frequency or the second resonant frequency. The operating frequency of the LLC resonant module 13 is selected based on the load of the coil module 14. The operating frequency is the first resonant frequency when the load is low, and the operating frequency is the second resonant frequency when the load is high. The resonant inductance is adjusted... Equivalent inductance of coil and resonant capacitor The parameters are set to ensure that the circuit reaches the optimal resonant state at the selected resonant frequency, thus achieving soft-switching operation.

[0050] First resonant frequency =

[0051] Second resonant frequency =

[0052] 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 or second resonant frequency under different load conditions through the LLC resonant module 13, precise control of the system can be achieved, improving system efficiency and stability, reducing losses, and protecting devices. This design is particularly suitable for induction heating applications that require efficient, stable, and reliable operation.

[0053] Operating the switching transistor in ZVS (zero voltage switching) mode can significantly reduce switching losses and improve system efficiency and reliability.

[0054] In one embodiment, the coil module 14 has a multi-coil structure, which can be connected in series or in parallel to form distributed multi-point heating and expand the heating area. Through series connection, the voltages of multiple coils can be accumulated. The series structure is easily expandable; the total voltage can be increased by increasing the number of coils to accommodate larger load demands. Parallel connection increases the total current capacity. If one coil fails, the other coils can continue to operate, improving the redundancy and reliability of the system.

[0055] By employing a multi-coil structure with coils connected in series or parallel, different heating requirements can be flexibly adapted. Series connections are suitable for applications requiring high voltage, uniform current distribution, and simplified control, while parallel connections are suitable for applications requiring high current, independent control, and high redundancy. This design makes the system more flexible, reliable, and easy to maintain.

[0056] This application also provides a control method applicable to the bridgeless three-level induction heating device as described in any of the above embodiments, such as... Figure 7 As shown, Figure 7 This is a schematic flowchart of an embodiment of the control method for the bridgeless three-level induction heating device of this application, including the following steps:

[0057] Step S11: The filtering module filters out high-frequency noise from the power grid signal; through filtering, the subsequent bridgeless three-level inverter module can be protected from the influence of power grid noise, thus extending its service life.

[0058] Step S12: The bridgeless three-level inverter module receives the grid signal and directly converts the grid signal into high-frequency AC power; the rectifier bridge is eliminated, avoiding the loss problem caused by the rectifier diode and improving efficiency.

[0059] Step S13: The LLC resonant module receives high-frequency AC power and achieves energy transfer through resonance. By selecting appropriate resonance parameters, the circuit can exhibit ideal impedance characteristics at the resonant frequency, thereby maximizing the transfer of energy to the coil and improving heating efficiency. Through the resonance effect, soft switching operation can be achieved, reducing switching losses and improving energy transfer efficiency.

[0060] Step S14: The coil module receives high-frequency alternating current to generate a high-frequency alternating induced magnetic field, which forms eddy currents on the 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.

[0061] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A bridgeless three-level inductive heating device, characterized in that, include: A filtering module, which is connected to the power grid to filter out high-frequency noise in the power grid signal; A 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 high-frequency AC output; the bridgeless three-level inverter module does not include a rectifier bridge; LLC resonant module, the LLC resonant module is connected to the bridgeless three-level module to receive the high-frequency AC power, and the LLC resonant module generates a resonant effect based on the high-frequency AC power to realize energy transmission; A coil module is connected to the LLC resonant module. The coil module generates an AC electromagnetic field based on the high-frequency AC current to achieve induction heating.

2. The bridgeless three-level inductive heating apparatus of claim 1, wherein, It also includes a control module, which is connected to the bridgeless three-level inverter module and the LLC resonant module; the control module can adjust the heating power by adjusting the frequency and phase output of the bridgeless three-level inverter module; the control module can achieve soft switching operation by adjusting the parameters of the LLC resonant module.

3. The bridgeless three-level inductive heating apparatus of claim 2, wherein, The control module is an MCU unit, which controls the working mode of the bridgeless three-level inverter module. The working mode includes frequency conversion control, phase shift control and hybrid control.

4. The bridgeless three-level inductive heating apparatus of claim 3, wherein, 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 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 resonant module based on the induced current value and the temperature value to achieve negative feedback control.

5. The bridgeless three-level inductive heating apparatus of claim 4, wherein, The bridgeless three-level inverter module is either a full-bridge inverter or a half-bridge inverter.

6. The bridgeless three-level inductive heating apparatus of claim 5, wherein, 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 transistors, and every two driving units control a pair of inverting switching transistors to achieve independent driving.

7. The bridgeless three-level inductive heating apparatus of claim 5, wherein, The LLC resonant module includes a resonant inductor. Equivalent inductance of coil and resonant capacitor An LLC series resonance is formed; the operating frequency of the LLC resonant module is either a first resonant frequency or a second resonant frequency. The operating frequency of the LLC resonant module is selected based on the load of the coil module. The operating frequency is the first resonant frequency when the load is low, and the operating frequency is the second resonant frequency when the load is high.

8. The bridgeless three-level inductive heating apparatus of claim 7, wherein, The coil module has a multi-coil structure, which can be connected in series or in parallel.

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