Modular dual-frequency constant-current output type induction heating power supply

Abstract

The application relates to the technical field of induction heating devices, and discloses a modular double-frequency constant-current output type induction heating power supply which comprises a plurality of double-frequency constant-current output modules and a double-frequency resonant circuit connected with the plurality of double-frequency constant-current output modules, and the double-frequency resonant circuit is used for impedance matching of a heating coil; wherein one double-frequency constant-current output module comprises one double-frequency inverter circuit unit connected and used for outputting double-frequency voltage and one double-frequency synthetic constant-current resonant unit used for converting double-frequency constant voltage into double-frequency constant current. In the application, each module has double-frequency constant-current output characteristics irrelevant to equivalent resistance of a load, pure resistive input impedance, good double-frequency circulating current suppression effect, low cost, small switching tube loss, and the modules can be connected in parallel for power expansion; a hybrid control method of module number switching and double-frequency pulse density control is adopted to realize a wide power regulation range, and the application can adapt to heating of non-uniform workpieces of different sizes.

Description

Technical Field

[0001] This application relates to the field of induction heating device technology, specifically a modular dual-frequency constant current output induction heating power supply. Background Technology

[0002] Depending on the operating frequency, induction heating power supplies are divided into several frequency bands: low frequency (30Hz~150Hz), medium frequency (150Hz-10kHz), high frequency (10kHz-100kHz), high frequency (100kHz-1MHz), and ultra-high frequency (1MHz-5MHz). Among them, the medium frequency to high frequency range is more commonly used. The heating frequency directly determines the skin depth of the induction heating current, which affects the heating effect on metal objects.

[0003] However, traditional single-frequency induction heating is ill-suited for complex metal workpieces, easily leading to uneven heating and significant differences in mechanical strength between different heated areas, affecting workpiece quality and service life. Besides shape conditions, factors affecting the induction heating effect on complex metals include current frequency, heating power, and heating time. Taking gear induction hardening as an example, as the frequency of the induced current increases, the current density and temperature difference between the tooth tip and root gradually increase. If the heating power is low, the gear's heat can be naturally conducted over time, achieving uniform temperature, but this does not meet the demands of high efficiency and automation in industrial production. If the heating power is high, uneven temperature is likely to occur in a short time. Therefore, under conditions of high heating power and short heating time, using dual-frequency induction heating to achieve rapid temperature uniformity is currently a better implementation method. Furthermore, traditional voltage-source induction heating power supplies are prone to overcurrent or insufficient output power when the load changes, causing significant fluctuations in induced current and heating power. Therefore, in industrial production, constant current output characteristics independent of the load's equivalent resistance have advantages, enabling stable and reliable output power.

[0004] In summary, there is an urgent need for a modular dual-frequency constant current output induction heating power supply to perform dual-frequency induction heating on workpieces with complex shapes and achieve rapid temperature uniformity over a wide power range. Summary of the Invention

[0005] The purpose of this application is to provide a modular dual-frequency constant current output induction heating power supply, which aims to solve the problems in the prior art where the heating speed and temperature uniformity of traditional voltage source type single-frequency induction heating power supplies are mutually constrained and the power output is easily unstable due to load changes. The purpose is to perform dual-frequency induction heating on workpieces with different complex shapes and achieve rapid temperature uniformity over a wide power range.

[0006] To achieve the above objectives, this application provides a modular dual-frequency constant current output induction heating power supply, including several dual-frequency constant current output modules and a dual-frequency resonant circuit connected to all of the dual-frequency constant current output modules. The dual-frequency resonant circuit is used for impedance matching of the heating coil. Each dual-frequency constant current output module includes a connected dual-frequency inverter circuit unit and a dual-frequency synthesized constant current resonant unit. The dual-frequency inverter circuit unit is used to output a dual-frequency voltage, and the dual-frequency synthesized constant current resonant unit is used to convert the dual-frequency constant voltage into a dual-frequency constant current.

[0007] Several dual-frequency inverter circuit units have their corresponding first input terminals connected in parallel and then connected to the positive terminal of a preset output power supply. Several dual-frequency inverter circuit units have their corresponding second input terminals connected in parallel and then connected to the negative terminal of the output power supply. In a dual-frequency constant current output module, the first, second, and third output terminals of a dual-frequency inverter circuit unit are respectively connected to the first, second, and third input terminals of a corresponding dual-frequency synthesized constant current resonant unit. Several dual-frequency synthesized constant current resonant units have their first output terminals connected in parallel and then connected to the first terminal of a dual-frequency resonant circuit. Several dual-frequency synthesized constant current resonant units have their second output terminals connected in parallel and then connected to the second terminal of a dual-frequency resonant circuit.

[0008] Preferably, a dual-frequency inverter circuit unit includes an input capacitor, a low-frequency inverter circuit, and a high-frequency inverter circuit; wherein, the low-frequency inverter circuit includes a first IGBT and a second IGBT, and the high-frequency inverter circuit includes a first MOSFET and a second MOSFET.

[0009] For a dual-frequency inverter circuit unit, the connection method is as follows:

[0010] The first terminal of the input capacitor, the collector of the first IGBT, and the drain of the first MOSFET are connected to form the first input terminal of the dual-frequency inverter circuit unit; the second terminal of the input capacitor, the emitter of the second IGBT, and the source of the second MOSFET are connected to form the second input terminal of the dual-frequency inverter circuit unit; the emitter of the first IGBT and the collector of the second IGBT are connected to form the first output terminal of the dual-frequency inverter circuit unit; the source of the first MOSFET and the drain of the second MOSFET are connected to form the second output terminal of the dual-frequency inverter circuit unit; the second input terminal of the dual-frequency inverter circuit unit is also its third output terminal.

[0011] Preferably, a dual-frequency synthesized constant current resonant unit includes a low-frequency constant current output resonant circuit and a high-frequency constant current output resonant circuit; wherein, the low-frequency constant current output resonant circuit includes a first low-frequency inductor, a second low-frequency inductor, and a low-frequency capacitor; and the high-frequency constant current output resonant circuit includes a first high-frequency capacitor, a second high-frequency capacitor, and a high-frequency inductor.

[0012] For a dual-frequency synthesized constant current resonant unit, the connection method is as follows:

[0013] The first terminal of the first low-frequency inductor serves as the first input terminal of the dual-frequency synthesized constant current resonant unit and is connected to the first output terminal of the corresponding dual-frequency inverter circuit unit. The first terminal of the first high-frequency capacitor serves as the second input terminal of the dual-frequency synthesized constant current resonant unit and is connected to the second output terminal of the corresponding dual-frequency inverter circuit unit. The second terminal of the first low-frequency inductor, the first terminal of the low-frequency capacitor, and the first terminal of the second low-frequency inductor are connected together. The second terminal of the first high-frequency capacitor, the first terminal of the high-frequency inductor, and the first terminal of the second high-frequency capacitor are connected together. The second terminal of the low-frequency capacitor and the second terminal of the high-frequency inductor are connected together as the third input terminal of the dual-frequency synthesized constant current resonant unit and are connected to the third output terminal of the corresponding dual-frequency inverter circuit unit. The second terminal of the second low-frequency inductor and the second terminal of the second high-frequency capacitor are connected together to form the first output terminal of the dual-frequency synthesized constant current resonant unit. The third input terminal of the dual-frequency synthesized constant current resonant unit is also its second output terminal.

[0014] Furthermore: each of the first output terminals corresponding to several dual-frequency synthesized constant current resonant units is connected in parallel as the first output terminal of several dual-frequency synthesized constant current resonant units; each of the second output terminals corresponding to several dual-frequency synthesized constant current resonant units is connected in parallel as the second output terminal of several dual-frequency synthesized constant current resonant units.

[0015] Preferably, the dual-frequency resonant circuit includes a parallel inductor, a parallel capacitor, a series capacitor, and a heating coil, wherein the heating coil is equivalent to a series inductor and a series resistor connected in series; and the heating coil operates at a low frequency. When the series inductance and series resistance are at a low frequency, they are equivalent to a low-frequency series inductance and a low-frequency series resistance; when the heating coil operates at a high frequency, the series inductance and series resistance are equivalent to a high-frequency series inductance and a high-frequency series resistance.

[0016] The first end of the parallel inductor is connected to the first end of the parallel capacitor as the first end of the dual-frequency resonant circuit, and is connected to the first output end of several dual-frequency synthesized constant current resonant units; the second end of the parallel inductor is connected to the second end of the parallel capacitor, and is then connected to the first end of the series capacitor. The second end of the series capacitor is connected to the first end of the heating coil. The second end of the heating coil serves as the second end of the dual-frequency resonant circuit and is connected to the second output end of several dual-frequency synthesized constant current resonant units.

[0017] Preferably, the modular dual-frequency constant current output induction heating power supply is equipped with a corresponding parameter design method, which includes the following steps:

[0018] Select appropriate dual-frequency resonant frequencies and dual-frequency current magnitudes based on the shape of the object to be heated. The dual-frequency resonant frequencies include the low-frequency resonant frequency. and high frequency resonant frequency Dual-frequency current magnitude Including the magnitude of low-frequency current and the magnitude of high-frequency current Dual-frequency current is composed of the superposition of low-frequency current and high-frequency current;

[0019] The parameters of the dual-frequency resonant circuit, as well as the number of modules, are obtained based on the dual-frequency resonant frequency and the magnitude of the dual-frequency current. And the magnitude of the dual-frequency current of each module, for the first Each module has a dual-frequency current. Including low-frequency current and high frequency current ;

[0020] Based on the dual-frequency resonant frequency and dual-frequency current magnitude of each module, the parameters of the dual-frequency synthesized constant current resonant unit are obtained.

[0021] Preferably, each module has the same parameters and the same dual-frequency voltage-current gain and low-frequency resonant angular frequency. Corresponding low-frequency resonant frequency High-frequency resonant angular frequency Corresponding high frequency resonant frequency .

[0022] As a preferred option, the following parameter constraints apply to the dual-frequency synthesized constant current resonant unit:

[0023] The first low-frequency inductor and the second low-frequency inductor are of equal magnitude, and both are in line with the low-frequency capacitor. resonance;

[0024] The first high-frequency capacitor and the second high-frequency capacitor are of equal size, and both are parallel to the high-frequency inductor. resonance;

[0025] The first low-frequency inductor, the second low-frequency inductor, the first high-frequency capacitor, and the second high-frequency capacitor at the low-frequency resonant angular frequency and high frequency resonant angular frequency When in series resonance, both exhibit high impedance;

[0026] The first low-frequency inductor, the second low-frequency inductor, the second high-frequency capacitor, and the high-frequency inductor at the low-frequency resonant angular frequency. and high frequency resonant angular frequency When in series resonance, both exhibit high impedance;

[0027] The first high-frequency capacitor, the second high-frequency capacitor, the second low-frequency inductor, and the low-frequency capacitor at the low-frequency resonant angular frequency. and high frequency resonant angular frequency When in series resonance, both exhibit high impedance.

[0028] As a preferred option, the following parameter constraints apply to the dual-frequency resonant circuit:

[0029] Dual-frequency resonant circuit at low frequency resonant angular frequency and high frequency resonant angular frequency All exhibit low impedance.

[0030] Preferably, the modular dual-frequency constant current output induction heating power supply is equipped with a corresponding hybrid control method, which includes:

[0031] All modules use the same driver for their switching transistors. For a dual-frequency inverter circuit unit, the first and second IGBTs operate at the low-frequency resonant frequency. The first MOSFET and the second MOSFET operate at a high frequency resonant frequency. .

[0032] As a preferred approach, the principle of the hybrid control method is as follows:

[0033] When controlling the dual-frequency output power, the dual-frequency pulse density is adjusted first without changing the number of modules. This ensures that the output power of each module is greater than (n-1) / n times the rated power, thereby reducing the non-integer harmonics of each module, achieving better dual-frequency constant current output characteristics and higher efficiency, and ultimately reaching the target dual-frequency output power. If this cannot be achieved, the following process is repeated: after increasing or decreasing the number of modules, the dual-frequency pulse density is adjusted again until the target dual-frequency output power is reached.

[0034] Beneficial effects: The modular dual-frequency constant current output induction heating power supply of this application achieves constant current dual-frequency power synthesis through the parallel connection of multiple dual-frequency constant current output modules, and there is no circulating current between the modules, which can meet the application scenarios of high-power and high-efficiency dual-frequency induction heating; several dual-frequency inverter circuit units use IGBTs operating at low frequency and MOSFETs operating at high frequency, achieving a good balance between cost and efficiency. IGBTs and MOSFETs can achieve ZVS turn-on and zero phase angle, with low losses; several dual-frequency synthesized constant current resonant units achieve dual-frequency constant current output and exhibit pure resistivity, with dual-frequency current magnitude, The low-frequency voltage-current gain and high-frequency voltage-current gain are both constant and independent of the equivalent resistance, achieving good dual-frequency circulating current suppression. In the dual-frequency resonant circuit, the dual-frequency current of the heating coil is synthesized from the dual-frequency currents of several modules, and its magnitude is related to the number of modules and the dual-frequency current output by each module, but independent of the equivalent resistance of the heating coil. Through a hybrid control method, by using an appropriate number of modules and dual-frequency pulse density, a wide power range can be adjusted. This solves the problems of mutual constraint between heating speed and temperature uniformity in traditional voltage source type single-frequency induction heating power supplies, and the instability of power output caused by load changes. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 A structural block diagram of a modular dual-frequency constant current output induction heating power supply provided in the embodiments of this application;

[0037] Figure 2 A circuit diagram of a modular dual-frequency constant current output induction heating power supply provided in an embodiment of this application;

[0038] Figure 3 A flowchart illustrating the parameter design method for a modular dual-frequency constant current output induction heating power supply provided in this application embodiment;

[0039] Figure 4 The first embodiment provided in this application Equivalent circuit diagram of a dual-frequency synthesized constant current resonant unit;

[0040] Figure 5 Equivalent circuit diagram of the dual-frequency resonant circuit provided in the embodiments of this application;

[0041] Figure 6 The first embodiment provided in this application The relationship between the low-frequency and high-frequency output currents of each module and the frequency and equivalent load resistance is shown in the graph.

[0042] Figure 7 The first embodiment provided in this application The graph shows the relationship between the input impedance angle and frequency, and the equivalent load resistance of the low-frequency inverter circuit and the high-frequency inverter circuit of each module.

[0043] Figure 8 A flowchart illustrating the hybrid control method for a modular dual-frequency constant current output induction heating power supply provided in this application embodiment;

[0044] Figure 9 This is a schematic diagram illustrating how the hybrid control method provided in this application adjusts power by adjusting the number of modules and the dual-frequency pulse density.

[0045] The implementation, functional features, and advantages of this invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0046] It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0047] The most widely used power supply structure in the current field of induction heating is the voltage source type single-frequency induction heating power supply. This structure is difficult to adapt to complex metal workpieces and is prone to uneven heating. It also suffers from the problem that heating speed and temperature uniformity are mutually constrained, and the power output is easily unstable due to load changes. Therefore, there is an urgent need to study a dual-frequency induction heating power supply with a wide power range and output current independent of the load equivalent resistance.

[0048] Reference Figure 1 , Figure 1 The structural block diagram of the modular dual-frequency constant current output induction heating power supply provided in the embodiments of this application is shown.

[0049] In response to the above requirements, such as Figure 1 As shown, this embodiment discloses a modular dual-frequency constant current output induction heating power supply, including several dual-frequency constant current output modules and a dual-frequency resonant circuit connected to all of the several dual-frequency constant current output modules. The dual-frequency resonant circuit is used for impedance matching of the heating coil. Among them, a dual-frequency constant current output module includes a dual-frequency inverter circuit unit and a dual-frequency synthesized constant current resonant unit connected to it. The dual-frequency inverter circuit unit is used to output dual-frequency voltage, and the dual-frequency synthesized constant current resonant unit is used to convert dual-frequency constant voltage into dual-frequency constant current.

[0050] Several dual-frequency inverter circuit units have their corresponding first input terminals connected in parallel and then connected to the positive terminal of a preset output power supply. Several dual-frequency inverter circuit units have their corresponding second input terminals connected in parallel and then connected to the negative terminal of the output power supply. In a dual-frequency constant current output module, the first, second, and third output terminals of a dual-frequency inverter circuit unit are respectively connected to the first, second, and third input terminals of a corresponding dual-frequency synthesized constant current resonant unit. Several dual-frequency synthesized constant current resonant units have their first output terminals connected in parallel and then connected to the first terminal of a dual-frequency resonant circuit. Several dual-frequency synthesized constant current resonant units have their second output terminals connected in parallel and then connected to the second terminal of a dual-frequency resonant circuit.

[0051] like Figure 1 As shown, in a specific application of this embodiment, the modular dual-frequency constant current output induction heating power supply disclosed in this embodiment includes:

[0052] A dual-frequency inverter circuit unit for outputting dual-frequency voltage. A dual-frequency synthesized constant current resonant unit for converting dual-frequency constant voltage to dual-frequency constant current, and a dual-frequency resonant circuit for impedance matching of the heating coil. The first input terminals of each dual-frequency inverter circuit unit are connected in parallel and then connected to the positive terminal of a preset output power supply. The second input terminals of each dual-frequency inverter circuit unit are connected in parallel and then connected to the negative terminal of a preset output power supply; among several dual-frequency constant current output modules, the first... The first, second, and third output terminals of each dual-frequency inverter circuit unit are respectively connected to the corresponding... The first, second, and third input terminals of a dual-frequency synthesized constant current resonant unit are connected together; The first output terminals of each dual-frequency synthesized constant current resonant unit are connected in parallel and then connected to the first terminal of the dual-frequency resonant circuit. The second output terminal of each dual-frequency synthetic constant current resonant unit is connected in parallel to the second terminal of the dual-frequency resonant circuit.

[0053] Based on the above, this embodiment utilizes a dual-frequency inverter circuit unit to output dual-frequency voltage, a dual-frequency synthesized constant current resonant unit to convert dual-frequency constant voltage into dual-frequency constant current, and a dual-frequency resonant circuit to achieve impedance matching for the heating coil. Each module possesses dual-frequency constant current output characteristics independent of the load's equivalent resistance, good dual-frequency circulating current suppression, and purely resistive input impedance. It features low cost, low switching transistor losses, and the modules can be connected in parallel for power expansion. This power supply employs a hybrid control method combining module number switching and dual-frequency pulse density control to achieve a wide power adjustment range, adaptable to heating non-uniform objects of different sizes.

[0054] In practical applications, induction heating power supplies are classified into several frequency bands according to their operating frequency: low frequency (30Hz~150Hz), medium frequency (150Hz-10kHz), ultrasonic frequency (10kHz-100kHz), high frequency (100kHz-1MHz), and ultra-high frequency (1MHz-5MHz). Among these, the medium to high frequency range is the most commonly used. The heating frequency directly determines the skin depth of the induction heating current, thus affecting the heating effect on metal objects.

[0055] Currently, the most commonly used dual-frequency induction heating method in industrial production is asynchronous dual-frequency induction heating. This involves heating the workpiece at a low frequency using a low-frequency coil for a period of time, then immediately transferring the workpiece to a high-frequency coil for continued heating. This process requires two heating coils and a switching device, resulting in a complex overall structure and low production efficiency. Synchronous dual-frequency induction heating, on the other hand, uses only one heating coil, simultaneously heating the workpiece at both low and high frequencies, achieving uniform heating throughout the entire process, thus offering significant advantages. However, synchronous dual-frequency induction heating also presents some technical challenges, specifically:

[0056] Crosstalk exists between dual-frequency power supplies, affecting the independence of low-frequency and high-frequency outputs. Crosstalk causes circulating current between switching transistors, increasing conduction losses. In severe cases, it will affect the soft-switching effect of the switching transistors and the dual-frequency output characteristics.

[0057] Compared to single-frequency power combining, dual-frequency power combining is more prone to generating circulating currents between power modules. These circulating currents significantly affect the dual-frequency current output characteristics, limiting the power rating of synchronous dual-frequency power supplies. This is especially true in voltage-source type dual-frequency power supplies, where differences in switching transistors and drivers inevitably lead to variations in voltage sources. These voltage source output differences further affect the dual-frequency circulating currents, resulting in large circulating currents between the dual-frequency power modules and between the dual-frequency currents. In severe cases, the power supply may malfunction.

[0058] The equivalent resistance and equivalent inductance of the heating coil differ at low and high frequencies. During heating, the equivalent resistance changes, causing instability in the voltage source output power. The impedance matching of a synchronous dual-frequency power supply is insufficient to handle this complex operating condition. However, the constant current output characteristic, which is independent of the load's equivalent resistance, can better adapt to dual-frequency heating of complex workpieces.

[0059] Furthermore, single-module heating power is relatively low. As heating time progresses, heat on complex workpieces is naturally conducted, achieving uniform temperature overall, but this does not meet the demands of high efficiency and high automation in industrial production. If the heating power is high, uneven temperature can easily occur in a short time. Therefore, under conditions of high heating power and short heating time, using dual-frequency induction heating to achieve rapid temperature uniformity is currently a better implementation method.

[0060] Based on the specific shortcomings mentioned above, this embodiment further optimizes the disclosed modular dual-frequency constant current output induction heating power supply to perform dual-frequency induction heating on workpieces with complex shapes and achieve rapid temperature uniformity over a wide power range.

[0061] Reference Figure 2 , Figure 2 The circuit diagram of the modular dual-frequency constant current output induction heating power supply provided in the embodiments of this application is shown.

[0062] This embodiment addresses, for example... Figure 1 The block diagram of the modular dual-frequency constant current output induction heating power supply shown has been further designed, and based on... Figure 2 Please provide an explanation.

[0063] like Figure 2 As shown, a dual-frequency inverter circuit unit includes an input capacitor, a low-frequency inverter circuit, and a high-frequency inverter circuit; wherein, the low-frequency inverter circuit includes a first IGBT and a second IGBT, and the high-frequency inverter circuit includes a first MOSFET and a second MOSFET. For the first... The connection method of each dual-frequency inverter circuit unit is as follows:

[0064] Input capacitor The first end, the first IGBT collector and first MOSFET The drains are connected to form the first The first input terminal of a dual-frequency inverter circuit unit Input capacitor The second end, the second IGBT The emitter and the second MOSFET The source poles are connected to form the first The second input terminal of a dual-frequency inverter circuit unit First IGBT The emitter and the second IGBT The collectors are connected to form the first The first output terminal of a dual-frequency inverter circuit unit First MOSFET The source and the second MOSFET The drains are connected to form the first The second output terminal of each dual-frequency inverter circuit unit ;No. The second input terminal of a dual-frequency inverter circuit unit It is also its third output terminal .

[0065] like Figure 2 As shown, a dual-frequency synthesized constant current resonant unit includes a low-frequency constant current output resonant circuit and a high-frequency constant current output resonant circuit. The low-frequency constant current output resonant circuit includes a first low-frequency inductor, a second low-frequency inductor, and a low-frequency capacitor. The high-frequency constant current output resonant circuit includes a first high-frequency capacitor, a second high-frequency capacitor, and a high-frequency inductor. For the first... The connection method of the dual-frequency synthesized constant current resonant unit is as follows:

[0066] First low-frequency inductor The first end as the The first input terminal of a dual-frequency synthesized constant current resonant unit , and the The first output terminal of a dual-frequency inverter circuit unit Connected; First high-frequency capacitor The first end as the The second input terminal of a dual-frequency synthetic constant current resonant unit , and the The second output terminal of each dual-frequency inverter circuit unit Connected; First low-frequency inductor The second terminal, low-frequency capacitor First terminal, second low-frequency inductor The first end is connected to the first high-frequency capacitor. The second end, high-frequency inductor First terminal, second high-frequency capacitor The first terminal is connected to the low-frequency capacitor. The second end, high-frequency inductor The second end is connected as the first The third input terminal of a dual-frequency synthesized constant current resonant unit , and the The third output terminal of a dual-frequency inverter circuit unit Connected; second low-frequency inductor The second terminal and the second high-frequency capacitor The second end is connected to form the first The first output terminal of a dual-frequency synthetic constant current resonant unit , No. The third input terminal of a dual-frequency synthesized constant current resonant unit It is also its second output terminal .

[0067] and: Each first output terminal of a dual-frequency synthetic constant current resonant unit is connected in parallel as... The first output terminal of a dual-frequency synthetic constant current resonant unit ; Each second output terminal of a dual-frequency synthetic constant current resonant unit is connected in parallel as... The second output terminal of a dual-frequency synthetic constant current resonant unit .

[0068] like Figure 2 As shown, the dual-frequency resonant circuit includes a parallel inductor. Parallel capacitors Series capacitor And a heating coil, wherein the heating coil is equivalent to a series inductor. and series resistor They are connected in series. The heating coil operates at a low frequency. At that time, series inductor and series resistor Equivalent to a low-frequency series inductor and low-frequency series resistor The heating coil operates at a high frequency. At that time, series inductor and series resistor Equivalent to a high-frequency series inductor and high frequency series resistor Parallel inductors The first terminal and the parallel capacitor The first terminal is connected as the first terminal of the dual-frequency resonant circuit. ,and The first output terminal of a dual-frequency synthetic constant current resonant unit Connected; parallel inductors The second terminal and the parallel capacitor After connecting the second end, it is connected in series with the capacitor. The first end is connected in series with a capacitor. The second end is connected to the first end of the heating coil, and the second end of the heating coil serves as the second end of the dual-frequency resonant circuit. ,and The second output terminal of a dual-frequency synthetic constant current resonant unit Connected.

[0069] Based on the circuit design described above, this embodiment fully discloses a modular dual-frequency constant current output induction heating power supply.

[0070] Reference Figure 3 , Figure 3 A flowchart illustrating the parameter design method for a modular dual-frequency constant current output induction heating power supply provided in this application embodiment.

[0071] Applicable to, for example Figure 2 The modular dual-frequency constant current output induction heating power supply shown is as follows: Figure 3 As shown in the figure, this embodiment discloses a parameter design method for a modular dual-frequency constant current output induction heating power supply. The parameter design method includes the following steps:

[0072] Select appropriate dual-frequency resonant frequencies and dual-frequency current magnitudes based on the shape of the object to be heated. The dual-frequency resonant frequencies include the low-frequency resonant frequency. and high frequency resonant frequency Dual-frequency current magnitude Including the magnitude of low-frequency current and the magnitude of high-frequency current Dual-frequency current is composed of the superposition of low-frequency current and high-frequency current;

[0073] The parameters of the dual-frequency resonant circuit, as well as the number of modules, are obtained based on the dual-frequency resonant frequency and the magnitude of the dual-frequency current. And the magnitude of the dual-frequency current of each module, for the first Each module has a dual-frequency current. Including low-frequency current and high frequency current ;

[0074] Based on the dual-frequency resonant frequency and dual-frequency current magnitude of each module, the parameters of the dual-frequency synthesized constant current resonant unit are obtained.

[0075] In this specific application, each module has the same parameters and the same dual-frequency voltage-current gain and low-frequency resonant angular frequency. Corresponding low-frequency resonant frequency High-frequency resonant angular frequency Corresponding high frequency resonant frequency .

[0076] Reference Figure 4 , Figure 4 The first embodiment provided in this application Equivalent circuit diagram of a dual-frequency synthesized constant current resonant unit.

[0077] like Figure 4 As shown, for the first A dual-frequency synthesized constant current resonant unit has the following parameter constraints:

[0078] To achieve constant current output with low-frequency resonance and for the low-frequency resonant cavity to exhibit purely resistive behavior, the following must be satisfied: First low-frequency inductor With the second low-frequency inductor They are of equal size and both match the low-frequency capacitor. exist Resonance, that is , .

[0079] To achieve constant current output with high-frequency resonance and for the high-frequency resonant cavity to exhibit purely resistive behavior, the following must be satisfied: First high-frequency capacitor... With the second high-frequency capacitor They are of equal size and both are similar to high-frequency inductors. exist Resonance, that is , .

[0080] To achieve good dual-frequency circulating current suppression, the following must be met: First low-frequency inductor Second low-frequency inductor First high-frequency capacitor Second high-frequency capacitor At low frequency resonant angular frequency and high frequency resonant angular frequency At series resonance, both exhibit high impedance, that is:

[0081]

[0082]

[0083] First low-frequency inductor Second low-frequency inductor Second high-frequency capacitor High-frequency inductors At low frequency resonant angular frequency and high frequency resonant angular frequency At series resonance, both exhibit high impedance, that is:

[0084]

[0085]

[0086] First high-frequency capacitor Second high-frequency capacitor Second low-frequency inductor Low-frequency capacitors At low frequency resonant angular frequency and high frequency resonant angular frequency At series resonance, both exhibit high impedance, that is:

[0087]

[0088]

[0089] Reference Figure 5 , Figure 5 The equivalent circuit diagram of the dual-frequency resonant circuit provided in the embodiments of this application is shown.

[0090] like Figure 5 As shown, for a dual-frequency resonant circuit, the following parameter constraints exist:

[0091] Dual-frequency resonant circuit at low frequency resonant angular frequency and high frequency resonant angular frequency All exhibit low impedance, i.e. , .

[0092] After meeting the above parameter constraints, the modular dual-frequency constant current output induction heating power supply has the following characteristics: the dual-frequency circulating current of each module is well suppressed, the low-frequency current and high-frequency current operate independently, and high efficiency is achieved.

[0093] Reference Figure 6 , Figure 6 The first embodiment provided in this application The graph shows the relationship between the low-frequency and high-frequency output currents of each module and the frequency and the equivalent resistance of the load.

[0094] like Figure 6 As shown, at the low-frequency resonant frequency The magnitude of the low-frequency output current is independent of the magnitude of the low-frequency equivalent resistance, and the magnitude of the low-frequency voltage-current gain is fixed. At high frequency resonant frequency The magnitude of the high-frequency output current is independent of the magnitude of the high-frequency equivalent resistance, and the magnitude of the high-frequency voltage-current gain is independent of the high-frequency equivalent resistance; its gain is fixed. .

[0095] Reference Figure 7 , Figure 7The first embodiment provided in this application The graph shows the relationship between the input impedance angle and frequency, and the equivalent resistance of the load for the low-frequency inverter circuit and the high-frequency inverter circuit of each module.

[0096] like Figure 7 As shown, at the low-frequency resonant frequency The input impedance angle of the low-frequency inverter circuit is independent of the low-frequency equivalent resistance and is fixed at 0. The input impedance angle of the high-frequency inverter circuit is independent of the magnitude of the high-frequency equivalent resistance and is fixed at 0; all IGBTs and MOSFETs can achieve soft switching and have zero phase angle, resulting in low switching losses.

[0097] The dual-frequency current of the heating coil is the superposition of the low-frequency current and the high-frequency current of each module, wherein the magnitudes of the low-frequency and high-frequency current components are... , Through the switching module, a wide power range can be adjusted.

[0098] Reference Figure 8 , Figure 8 A flowchart illustrating the hybrid control method for a modular dual-frequency constant current output induction heating power supply provided in this application embodiment.

[0099] like Figure 8 As shown, this embodiment discloses a hybrid control method for a modular dual-frequency constant current output induction heating power supply. This hybrid control method includes:

[0100] All modules use the same driver for their switching transistors. For the first... Each dual-frequency inverter circuit unit has its first and second IGBTs operating at a low-frequency resonant frequency. The first MOSFET and the second MOSFET operate at a high frequency resonant frequency. The principle of the hybrid control method is as follows: when controlling the dual-frequency output power, the dual-frequency pulse density is adjusted first without changing the number of modules, so as to ensure that the output power of each module is greater than (n-1) / n times the rated power, in order to reduce the non-integer harmonics of each module, achieve better dual-frequency constant current output characteristics and higher efficiency, and finally achieve the target dual-frequency output power. If this cannot be achieved, the following process is repeated: after increasing or decreasing the number of modules, the dual-frequency pulse density is adjusted again until the target dual-frequency output power is achieved.

[0101] Reference Figure 9 , Figure 9 This is a schematic diagram illustrating how the hybrid control method provided in this application adjusts power by adjusting the number of modules and the dual-frequency pulse density.

[0102] like Figure 9As shown in the figure, the relationship between dual-frequency pulse density, number of modules, and dual-frequency output power is illustrated, along with the initial rated number of modules. Initial rated dual-frequency pulse density To achieve the target dual-frequency power, the dual-frequency pulse density is first reduced. When the total output power is reduced to 4 / 5 of the initial operating condition, the output power of each module is also reduced to 4 / 5, making it difficult to achieve the target output power. At this point, the dual-frequency pulse density is increased. Number of modules ; and then continue to reduce the dual-frequency pulse density until the output power reaches , At 3 / 4 of the time, the target output power was not reached, resulting in a decrease in dual-frequency pulse density. Number of modules Continue reducing the dual-frequency pulse density and repeat the process until... The dual-frequency pulse density is The target output dual-frequency power can be achieved. This hybrid control method can reduce the non-integer harmonics of each module's output under pulse density control, thereby achieving better dual-frequency constant current output characteristics, better soft-switching effect, and higher efficiency.

[0103] Based on the above design, the modular dual-frequency constant current output induction heating power supply of this embodiment achieves at least the following technical effects:

[0104] 1. The dual-frequency inverter circuit unit generates a dual-frequency voltage source by using a hybrid device of IGBT and MOSFET. Both IGBT and MOSFET can achieve soft switching, resulting in low cost, low switching loss and high efficiency.

[0105] 2. The dual-frequency synthesized constant current resonant unit achieves the conversion of dual-frequency constant voltage input into dual-frequency constant current output through resonant parameter design. The output current of each module is constant and independent of the load size. Each module has a purely resistive input impedance, which enables the switching transistor to have a zero phase angle, achieving low loss. In addition, the dual-frequency circulating current of each module is well suppressed, improving the reliability and efficiency of the power supply.

[0106] 3. The heating coil achieves dual-frequency power selection through a dual-frequency resonant circuit. Its dual-frequency current is directly superimposed through the dual-frequency current output by n dual-frequency synthesized constant current resonant units. The total output dual-frequency current is only related to the number of modules, and multiple modules can be directly connected in parallel to expand the power capacity.

[0107] 4. By adopting a hybrid control method that adjusts the number of modules and the dual-frequency pulse density, the non-integer harmonics of each module output are reduced, achieving better dual-frequency constant current output characteristics and reaching the target dual-frequency output power with higher efficiency.

[0108] In summary, the modular dual-frequency constant current output induction heating power supply of this embodiment solves the problems of mutual constraint between heating speed and temperature uniformity effect and unstable power output caused by load changes in traditional voltage source type single-frequency induction heating power supplies. It can perform dual-frequency induction heating on workpieces with different complex shapes and achieve rapid temperature uniformity over a wide power range.

[0109] It should be understood that the above are merely illustrative examples and do not constitute any limitation on the technical solutions of the present invention. In specific applications, those skilled in the art can make settings as needed, and the present invention does not impose any restrictions on this.

[0110] It should be noted that the workflow described above is merely illustrative and does not limit the scope of protection of this invention. In practical applications, those skilled in the art can select some or all of the workflow to achieve the purpose of this embodiment according to actual needs, and no restrictions are imposed here.

[0111] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or system that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or system. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or system that includes that element.

[0112] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. Any equivalent structural or procedural transformations made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

Claims

1. A modular dual-frequency constant-current output type induction heating power supply, characterized by, The module includes a plurality of double-frequency constant-current output modules and a double-frequency resonant circuit connected with the plurality of double-frequency constant-current output modules, and the double-frequency resonant circuit is used for impedance matching of a heating coil; wherein one double-frequency constant-current output module includes a double-frequency inverter circuit unit and a double-frequency synthetic constant-current resonant unit connected with each other, the double-frequency inverter circuit unit is used for outputting double-frequency voltage, and the double-frequency synthetic constant-current resonant unit is used for converting double-frequency constant voltage into double-frequency constant current. The first input ends of the plurality of double-frequency inverter circuit units are connected with a positive electrode of a preset output power supply in parallel, and the second input ends of the plurality of double-frequency inverter circuit units are connected with a negative electrode of the output power supply in parallel; in one double-frequency constant-current output module, the first output end, the second output end and the third output end of one double-frequency inverter circuit unit are connected with the first input end, the second input end and the third input end of a corresponding double-frequency synthetic constant-current resonant unit respectively; the first output ends of the plurality of double-frequency synthetic constant-current resonant units are connected with a first end of the double-frequency resonant circuit in parallel, and the second output ends of the plurality of double-frequency synthetic constant-current resonant units are connected with a second end of the double-frequency resonant circuit in parallel. For one double-frequency inverter circuit unit, the double-frequency inverter circuit unit includes an input capacitor, a low-frequency inverter circuit and a high-frequency inverter circuit; wherein the low-frequency inverter circuit includes a first IGBT and a second IGBT, and the high-frequency inverter circuit includes a first MOSFET and a second MOSFET. For one double-frequency synthetic constant-current resonant unit, the double-frequency synthetic constant-current resonant unit includes a low-frequency constant-current output type resonant circuit and a high-frequency constant-current output type resonant circuit; wherein the low-frequency constant-current output type resonant circuit includes a first low-frequency inductor, a second low-frequency inductor and a low-frequency capacitor; and the high-frequency constant-current output type resonant circuit includes a first high-frequency capacitor, a second high-frequency capacitor and a high-frequency inductor. The modular double-frequency constant-current output type induction heating power supply is provided with a corresponding hybrid control method, and the hybrid control method includes the following steps: The switching tubes of all modules are driven by the same drive, for a dual-frequency inverter circuit unit, the first IGBT and the second IGBT work at a low-frequency resonance frequency , and the first MOSFET and the second MOSFET work at a high-frequency resonance frequency .

2. The modular dual-frequency constant-current output type induction heating power supply according to claim 1, characterized by, For one double-frequency inverter circuit unit, the connection mode is as follows: The first end of the input capacitor, the collector of the first IGBT and the drain of the first MOSFET are connected to form the first input end of the double-frequency inverter circuit unit; the second end of the input capacitor, the emitter of the second IGBT and the source of the second MOSFET are connected to form the second input end of the double-frequency inverter circuit unit; the emitter of the first IGBT and the collector of the second IGBT are connected to form the first output end of the double-frequency inverter circuit unit; the source of the first MOSFET and the drain of the second MOSFET are connected to form the second output end of the double-frequency inverter circuit unit; and the second input end of the double-frequency inverter circuit unit is also the third output end thereof.

3. The modular dual-frequency constant-current output type induction heating power supply according to claim 1, characterized by For one double-frequency synthetic constant-current resonant unit, the connection mode is as follows: The first end of the first low-frequency inductor is connected to the first output end of the corresponding dual-frequency inversion circuit unit as the first input end of the dual-frequency synthetic constant-current resonance unit; the first end of the first high-frequency capacitor is connected to the second output end of the corresponding dual-frequency inversion circuit unit as the second input end of the dual-frequency synthetic constant-current resonance unit; the second end of the first low-frequency inductor, the first end of the low-frequency capacitor and the first end of the second low-frequency inductor are connected, the second end of the first high-frequency capacitor, the first end of the high-frequency inductor and the first end of the second high-frequency capacitor are connected, and the second end of the low-frequency capacitor and the second end of the high-frequency inductor are connected as the third input end of the dual-frequency synthetic constant-current resonance unit, which is connected to the third output end of the corresponding dual-frequency inversion circuit unit; the second end of the second low-frequency inductor and the second end of the second high-frequency capacitor are connected to form the first output end of the dual-frequency synthetic constant-current resonance unit, and the third input end of the dual-frequency synthetic constant-current resonance unit is also the second output end thereof. Furthermore, each first output end of the plurality of dual-frequency synthetic constant-current resonance units is connected in parallel as the first output end of the plurality of dual-frequency synthetic constant-current resonance units, and each second output end of the plurality of dual-frequency synthetic constant-current resonance units is connected in parallel as the second output end of the plurality of dual-frequency synthetic constant-current resonance units.

4. The modular dual-frequency constant-current output type induction heating power supply according to claim 1, characterized by The dual-frequency resonant circuit includes a parallel inductor, a parallel capacitor, a series capacitor, and a heating coil, wherein the heating coil is equivalent to a series inductor and a series resistor connected in series; and the heating coil operates at a low frequency. When the series inductance and series resistance are at a low frequency, they are equivalent to a low-frequency series inductance and a low-frequency series resistance; when the heating coil operates at a high frequency, the series inductance and series resistance are equivalent to a high-frequency series inductance and a high-frequency series resistance. The first end of the parallel inductor is connected to the first end of the parallel capacitor as the first end of the dual-frequency resonance circuit, which is connected to the first output end of the plurality of dual-frequency synthetic constant-current resonance units; the second end of the parallel inductor is connected to the second end of the parallel capacitor, which is then connected to the first end of the series capacitor, the second end of the series capacitor is connected to the first end of the heating coil, and the second end of the heating coil is connected to the second end of the dual-frequency resonance circuit, which is connected to the second output end of the plurality of dual-frequency synthetic constant-current resonance units.

5. The modular dual-frequency constant-current output type induction heating power supply according to claim 1, characterized by The modular dual-frequency constant-current output type induction heating power supply is provided with a corresponding parameter design method, which comprises the following steps: The corresponding dual-frequency resonant frequency and dual-frequency current magnitude are selected based on the shape of the object to be heated. The dual-frequency resonant frequency includes the low-frequency resonant frequency. and high frequency resonant frequency Dual-frequency current magnitude Including the magnitude of low-frequency current and the magnitude of high-frequency current Dual-frequency current is composed of the superposition of low-frequency current and high-frequency current; Based on the double-frequency resonance frequency and the double-frequency current size, the parameters of the double-frequency resonance circuit and the number of modules are obtained and the double-frequency current size of each module, for the first module, the double-frequency current includes a low-frequency current and a high-frequency current ; Based on the dual-frequency resonance frequency and the dual-frequency current size of each module, the parameters of the dual-frequency synthetic constant-current resonance unit are obtained.

6. The modular dual-frequency constant-current output type induction heating power supply according to claim 5, characterized by The parameters of each module are identical and have the same dual frequency voltage-current gain, low frequency resonant angular frequency corresponding low frequency resonant frequency high frequency resonant angular frequency corresponding high frequency resonant frequency .

7. The modular dual-frequency constant-current output type induction heating power supply according to claim 3, characterized by For the dual-frequency synthetic constant-current resonance unit, the following parameter constraint conditions exist: The first low-frequency inductor and the second low-frequency inductor are equal in size, and are both connected with the low-frequency capacitor in parallel resonance; The first high-frequency capacitor and the second high-frequency capacitor are equal in size, and are connected in parallel with the high-frequency inductor Resonance; The first low-frequency inductor, the second low-frequency inductor, the first high-frequency capacitor, and the second high-frequency capacitor are at a low-frequency resonance angular frequency and a high-frequency resonance angular frequency Both present high impedance in series resonance; The first low-frequency inductor, the second low-frequency inductor, the second high-frequency capacitor, and the high-frequency inductor are at a low-frequency resonance angular frequency and a high-frequency resonance angular frequency Both present high impedance in series resonance; The first high-frequency capacitor, the second high-frequency capacitor, the second low-frequency inductor, and the low-frequency capacitor are at a low-frequency resonance angular frequency and a high-frequency resonance angular frequency Both present high impedance at series resonance.

8. The modular dual-frequency constant-current output type induction heating power supply according to claim 5, characterized by, For the dual-frequency resonance circuit, the following parameter constraint conditions exist: The dual frequency resonant circuit presents a low impedance at both the low frequency resonant angular frequency and the high frequency resonant angular frequency .

9. The modular dual-frequency constant-current output type induction heating power supply according to claim 1, characterized by, The principle of the hybrid control method is as follows: When controlling the dual-frequency output power, the dual-frequency pulse density is preferentially adjusted without changing the number of modules, so that the output power of each module is greater than (n-1) / n times of the rated power, so as to reduce the non-integer harmonic of each module, realize dual-frequency constant-current output, and finally reach the target dual-frequency output power. If it cannot be met, the following process is repeated: increase or decrease one module number, then adjust the dual-frequency pulse density, and continue until the target dual-frequency output power is reached.

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