Load adaptive inductive heating power supply

Abstract

The application relates to the technical field of induction heating devices, and discloses a load-adaptive type induction heating power supply, which comprises a double-gain inverter circuit module for outputting two kinds of electric level grade voltages and a load-adaptive type resonance module capable of impedance matching for ferromagnetic loads and non-ferromagnetic loads. The application realizes constant voltage output mode and constant current output mode by changing the working frequency, is respectively used for heating ferromagnetic materials with low quality factors and non-ferromagnetic materials with high quality factors, realizes wide-range high-efficiency power regulation in half-gain mode and full-gain mode by changing the switching state, has the output characteristics of pure resistive input, zero input phase angle and load equivalent resistance independence, the switching tube has low loss, the power supply has a load-adaptive detection method, can identify the load type on line to work in a suitable heating mode, the power supply has few switching tubes, does not need a bidirectional switching matching circuit, and can better cope with the heating of different material loads.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of induction heating devices, and particularly relates to a load adaptive type induction heating power supply. BACKGROUND

[0002] As a green and controllable heating technology, induction heating is widely used in household cookers, metal quenching and other fields. Generally, the load of induction heating is divided into ferromagnetic materials and non-ferromagnetic materials. With the increase of frequency, the equivalent inductance of the ferromagnetic load slightly decreases, and the equivalent resistance gradually increases, while the equivalent inductance of the non-ferromagnetic material changes little, and the equivalent resistance slightly increases. Under similar shapes and similar frequencies, the equivalent inductance and equivalent resistance of the ferromagnetic load are significantly greater than those of the non-ferromagnetic material.

[0003] The existing induction heating power supply is designed for heating ferromagnetic materials. When heating non-ferromagnetic materials at the same time, due to the difference in equivalent inductance and equivalent resistance of the two materials, the power supply cannot achieve good impedance matching, and the low equivalent resistance of the non-ferromagnetic material easily leads to overcurrent of the power supply. Therefore, the existing technology cannot simultaneously heat the load of ferromagnetic materials and non-ferromagnetic materials.

[0004] To achieve simultaneous heating of ferromagnetic materials and non-ferromagnetic materials, the existing solution mostly uses a bidirectional switch to switch different resonant circuits for impedance matching of the load, but this increases the switching element, increases the cost and complexity of the system, and reduces the efficiency of the system. Moreover, due to the nature of different resonant circuits, the power supply cannot identify the load type online, which poses a challenge to the automation demand of induction heating.

[0005] In summary, there is an urgent need for a load adaptive type induction heating power supply that can simultaneously adapt to the heating of ferromagnetic materials and non-ferromagnetic materials with low cost and complexity. SUMMARY

[0006] The purpose of the present application is to provide a load adaptive type induction heating power supply to solve the technical problems in the prior art that the bidirectional switch structure results in high cost and complexity of the power supply, low efficiency, and difficulty in identifying the load type online.

[0007] To achieve the above-mentioned purpose, the present application provides a load adaptive type induction heating power supply, which comprises a dual-gain inverter circuit module and a load adaptive type resonant module; wherein: the dual-gain inverter circuit module is used to output two levels of voltage, and the output voltage level is determined based on the output power; the load adaptive type resonant module is used to adapt to the ferromagnetic load or the non-ferromagnetic load, and the adaptation at least includes impedance matching;

[0008] The first input end of the dual-gain inverter circuit module is connected with the positive pole of the preset output power supply, the second input end of the dual-gain inverter circuit module is connected with the negative pole of the output power supply, the first output end of the dual-gain inverter circuit module is connected with the first end of the load adaptive resonant module, and the second output end of the dual-gain inverter circuit module is connected with the second end of the load adaptive resonant module.

[0009] As preferred, the dual-gain inverter circuit module is a parallel dual-gain inverter circuit or a series dual-gain inverter circuit, and the parallel dual-gain inverter circuit and the series dual-gain inverter circuit each at least include a first switch tube, a second switch tube, a third switch tube and a fourth switch tube.

[0010] As preferred, when the dual-gain inverter circuit module is the parallel dual-gain inverter circuit, the parallel dual-gain inverter circuit further includes a first input capacitor; the first end of the first input capacitor, the drain of the first switch tube and the drain of the third switch tube are connected to form the first input end of the dual-gain inverter circuit module; the source of the first switch tube and the drain of the second switch tube are connected to form the first output end of the dual-gain inverter circuit module; the source of the third switch tube and the drain of the fourth switch tube are connected to form the second output end of the dual-gain inverter circuit module; the second end of the first input capacitor, the source of the second switch tube and the source of the fourth switch tube are connected to form the second input end of the dual-gain inverter circuit module.

[0011] When the dual-gain inverter circuit module is the series dual-gain inverter circuit, the series dual-gain inverter circuit further includes a second input capacitor and a third input capacitor; the first end of the second input capacitor and the drain of the first switch tube are connected to form the first input end of the dual-gain inverter circuit module, the source of the first switch tube and the drain of the second switch tube are connected to form the first output end of the dual-gain inverter circuit module, the second end of the second input capacitor, the first end of the third input capacitor, the source of the second switch tube and the drain of the third switch tube are connected, the source of the third switch tube and the drain of the fourth switch tube are connected to form the second output end of the dual-gain inverter circuit module, and the second end of the third input capacitor and the source of the fourth switch tube are connected to form the second input end of the dual-gain inverter circuit module.

[0012] As preferred, the load adaptive resonant module is an LCCLL series-parallel resonant circuit or an LCLCL series-parallel resonant circuit, and the LCCLL series-parallel resonant circuit and the LCLCL series-parallel resonant circuit each include a series inductor, a series capacitor, a parallel inductor, a parallel capacitor and a heating coil, and the heating coil is equivalent to the series connection of an output inductor and an output resistor.

[0013] As preferred, when the load adaptive resonant module is an LCCLL series-parallel resonant circuit, the first end of the series inductor is the first end of the load adaptive resonant module, the second end of the series inductor and the first end of the series capacitor are connected, the second end of the series capacitor, the first end of the parallel capacitor, the first end of the parallel inductor, and the first end of the output inductor are connected, the second end of the parallel capacitor, the second end of the parallel inductor, and the second end of the output resistor are connected to be the second end of the load adaptive resonant module, the second end of the output inductor and the first end of the output resistor are connected.

[0014] When the load adaptive resonant module is an LCLCL series-parallel resonant circuit, the first end of the series inductor is the first end of the load adaptive resonant module, the second end of the series inductor, the first end of the parallel capacitor, the first end of the parallel inductor, and the first end of the series capacitor are connected, the second end of the parallel capacitor, the second end of the parallel inductor, and the second end of the output resistor are connected to be the second end of the load adaptive resonant module, the second end of the series capacitor and the first end of the output inductor are connected, and the second end of the output inductor and the first end of the output resistor are connected.

[0015] As preferred, when the load adaptive resonant module is an LCCLL series-parallel resonant circuit, the first end of the series inductor is the first end of the load adaptive resonant module, the second end of the series inductor and the first end of the series capacitor are connected, the second end of the series capacitor, the first end of the parallel capacitor, the first end of the parallel inductor, and the first end of the output inductor are connected, the second end of the parallel capacitor, the second end of the parallel inductor, and the second end of the output resistor are connected to be the second end of the load adaptive resonant module, the second end of the output inductor and the first end of the output resistor are connected.

[0016] The double-gain control method specifically includes:

[0017] When the double-gain inverter circuit module is a parallel double-gain inverter circuit and the parallel double-gain inverter circuit module works in a half-gain mode, the double-gain inverter circuit works as a half-bridge inverter circuit, the third switch tube is always on, the fourth switch tube is always off, the first switch tube and the second switch tube work at a resonant frequency point , and the driving signals are complementary, and the output voltage is and 0; when the double-gain inverter circuit module is a parallel double-gain inverter circuit and the parallel double-gain inverter circuit module works in a full-gain mode, the double-gain inverter circuit module works as a full-bridge inverter circuit, the first switch tube, the second switch tube, the third switch tube, and the fourth switch tube work at a resonant frequency point , wherein the driving signals of the first switch tube and the fourth switch tube are the same, the driving signals of the second switch tube and the third switch tube are the same, and the driving signals of the two pairs of switch tubes are complementary, and the output voltage is .

[0018] When the double-gain inverter circuit module is a series double-gain inverter circuit and the series double-gain inverter circuit module works in a half-gain mode, the first switch tube, the second switch tube, the third switch tube, and the fourth switch tube work at a frequency point , the first switch tube and the fourth switch tube drive duty ratio of 25%, the second switch tube and the third switch tube drive duty ratio of 75%, the second switch tube, the third switch tube and the fourth switch tube phase lagging behind the first switch tube 25%, 75% and 50% respectively, the output voltage is And 0; series type dual gain inverter circuit module works in full gain mode, the first switch tube, the second switch tube, the third switch tube and the fourth switch tube work at the resonance frequency point , wherein: the first switch tube and the fourth switch tube drive signal is the same, the second switch tube and the third switch tube drive signal is the same, and the two pairs of switch tube drive signal is complementary, and the output voltage is And 0.

[0019] As preferred, the load of the heating coil is ferromagnetic material, and the output inductance and the output resistance are equivalent to the ferromagnetic output inductance and the ferromagnetic output resistance; when heating the ferromagnetic material, the load adaptive induction heating power works at the resonance frequency point , which is constant voltage output mode;

[0020] When the heating load of the heating coil is non-ferromagnetic material, the output inductance and the output resistance are equivalent to the non-ferromagnetic output inductance and the non-ferromagnetic output resistance; when heating the non-ferromagnetic material, the load adaptive induction heating power works at the resonance frequency point , which is constant current output mode.

[0021] As preferred, the load adaptive resonance module has the following parameter constraints:

[0022] The resonance frequency point Is less than the resonance frequency point ; parallel capacitor and parallel inductor are in parallel resonance at the resonance frequency point ; series inductance, series capacitance, ferromagnetic output inductance are in series resonance at the resonance frequency point ;

[0023] When the load adaptive resonance module is LCCLL series-parallel resonant circuit, at the resonance frequency point , the impedance of the series inductance and the series capacitance in series is equal to the impedance of the non-ferromagnetic output inductance, and the impedance of the parallel capacitor and the parallel inductor in parallel and then in series with the series inductance and the series capacitance is 0;

[0024] When the load adaptive resonance module is LCLCL series-parallel resonant circuit, at the resonance frequency point , the impedance of the non-ferromagnetic output inductance and the series capacitance in series is equal to the impedance of the series inductance, and the impedance of the parallel capacitor and the parallel inductor in parallel and then in series with the series inductance is 0.

[0025] As preferred, the load-adaptive induction heating power supply is provided with a corresponding load-adaptive detection method for online identifying the load type to work in the corresponding heating mode, the load-adaptive detection method comprises:

[0026] The power supply always works in the half-gain mode, and the phase relationship is judged by sampling the output voltage and output current of the double-gain inverter circuit module; the starting working frequency of the power supply is mathematically expressed as:

[0027]

[0028] Wherein, and are the resonance frequency points; based on the starting working frequency , a plurality of frequency points are selected by the dichotomy method, and the mathematical expressions corresponding to the plurality of frequency points are at least:

[0029]

[0030]

[0031]

[0032]

[0033] Wherein, ;

[0034] The power supply is made to work at the starting working frequency for a short time, and then the power supply is constantly approximated to the frequency points on both sides, and the following judgments are made when approximating:

[0035] If the phase relationship is not fixed, the coil is empty, and the power supply needs to be turned off immediately;

[0036] If the power supply is approximated to the frequency point on the left side, the current always leads the voltage, or the current first leads the voltage, and then the current always lags behind the voltage, which is a ferromagnetic load;

[0037] If the power supply is approximated to the frequency point on the right side, the current always lags behind the voltage, or the current first leads the voltage, and then the current always lags behind the voltage, which is a non-ferromagnetic load.

[0038] As preferred, based on the online identification of the load type, the load-adaptive induction heating power supply is provided with a corresponding power control method, the power control method comprises:

[0039] The preset output power is obtained, the preset output power is compared with the rated output power, and the following judgments are made:

[0040] When the preset output power is greater than one fourth of the rated output power, a full gain mode is adopted, and a phase-shift control is adopted to adjust the output power by adjusting the lagging phase angle of the third switch tube and the fourth switch tube to the first switch tube and the second switch tube;

[0041] When the preset output power is less than one fourth of the rated output power, a half gain mode is adopted to adjust the output power by changing the pulse density of the drive;

[0042] After the gain mode is determined, the output voltage and the output current of the dual-gain inverter circuit module are synchronously detected to obtain the real-time output power, and the preset output power is adjusted based on the requirement of the real-time output power to redetermine the gain mode.

[0043] Beneficial effects: The load adaptive induction heating power supply provided by the application realizes voltage output of two level grades through a dual-gain control method; the load adaptive resonance module realizes constant voltage output characteristics and constant current output characteristics irrelevant to the equivalent resistance of the load at two resonance frequency points through parameter constraint, and has a pure resistive input and a zero input phase angle; based on the characteristics of the load adaptive resonance module, a load adaptive detection method is adopted to identify the load type online to work in a suitable heating mode, and a corresponding wide-range high-efficiency power control method reduces the loss of the power supply; the overall cost and complexity of the power supply are low, the efficiency is high, the power supply can well adapt to the heating of ferromagnetic materials and non-ferromagnetic materials at the same time, and thus the technical solution of the existing bidirectional switch structure is optimized. BRIEF DESCRIPTION OF DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0045] Figure 1 The structural block diagram of the load adaptive induction heating power supply provided by the embodiments of the application is shown in the figure;

[0046] Figure 2 The circuit principle diagram of the dual-gain inverter circuit module provided by the embodiments of the application is a parallel type dual-gain inverter circuit;

[0047] Figure 3 The circuit principle diagram of the dual-gain inverter circuit module provided by the embodiments of the application is a series type dual-gain inverter circuit;

[0048] Figure 4The load adaptive resonant module provided by the embodiment of the application is a circuit schematic diagram of an LCCLL series-parallel resonant circuit.

[0049] Figure 5 The load adaptive resonant module provided by the embodiment of the application is a circuit schematic diagram of an LCLCL series-parallel resonant circuit.

[0050] Figure 6 The control timing of the half-gain mode and the full-gain mode of the parallel dual-gain inverter circuit provided by the embodiment of the application is shown in the following table.

[0051] Figure 7 The control timing of the half-gain mode and the full-gain mode of the series dual-gain inverter circuit provided by the embodiment of the application is shown in the following table.

[0052] Figure 8 The input impedance size and the input impedance angle curve of the load adaptive resonant module provided by the embodiment of the application when the load is empty, ferromagnetic material or non-ferromagnetic material are shown in the following table.

[0053] Figure 9 The relationship between the output voltage-input voltage gain and the output current-input voltage gain and the frequency of the load adaptive induction heating power supply provided by the embodiment of the application is shown in the following table.

[0054] Figure 10 The schematic diagram of the load adaptive detection method provided by the embodiment of the application to select several frequency points by dichotomy is shown in the following table.

[0055] Figure 11 The schematic diagram of the wide-range high-efficiency power control method provided by the embodiment of the application is shown in the following table, wherein (a) is the relationship between the output power and the pulse density in the half-gain mode, and (b) is the relationship between the output power and the phase-shifting angle in the full-gain mode.

[0056] The implementation, functional features and advantages of the application will be further described with reference to the embodiments and the accompanying drawings. DETAILED DESCRIPTION

[0057] The technical solutions in the embodiments of the application will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the application, but not all the embodiments of the application. Based on the embodiments in the application, all the other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0058] In this document, the terms "comprise" and "comprising" are used in the sense of "including" and alike, and allow for elements "not including", that is, being optional. In other words, the terms "comprise" and "comprising" should be interpreted as specifying the presence of stated features or components, but do not preclude the presence or addition of one or more other features, components, or steps.

[0059] Current induction heating as a clean heating method occupies a very important position in the field of household and industrial heating. However, with the development of society, the traditional power supply can only meet the needs of a single type of load, and different load types put forward higher demands on the induction heating power supply.

[0060] Reference Figure 1 , Figure 1 The structural block diagram of the load adaptive induction heating power supply provided by the embodiment of the present application is provided.

[0061] In response to the higher demands of different load types on the induction heating power supply, as shown in Figure 1 , the embodiment discloses a load adaptive induction heating power supply, comprising a dual-gain inverter circuit module and a load adaptive resonance module; wherein: the dual-gain inverter circuit module is used to output two level grade voltages, and the output level grade voltage is determined based on the output power; the load adaptive resonance module is used to adapt to ferromagnetic load or non-ferromagnetic load, and the adaptation at least includes impedance matching.

[0062] As shown in Figure 1 , the first input end of the dual-gain inverter circuit module is connected with the positive pole of the preset output power supply, the second input end of the dual-gain inverter circuit module is connected with the negative pole of the output power supply, the first output end of the dual-gain inverter circuit module is connected with the first end of the load adaptive resonance module, the second output end of the dual-gain inverter circuit module is connected with the second end of the load adaptive resonance module.

[0063] Through the above, the load adaptive induction heating power supply of the embodiment outputs two level grade voltages through the dual-gain inverter circuit module, and the load adaptive resonance module performs impedance matching for different loads; the cost and complexity are low, the efficiency is high, and the heating of ferromagnetic materials and non-ferromagnetic materials can be well adapted at the same time.

[0064] Now we analyze the scenario of the load adaptive induction heating power supply of the embodiment in actual application.​​​​​​

[0065] Generally, the load types of induction heating include ferromagnetic loads and non-ferromagnetic loads. Different materials have different properties when they are heated by induction: as the frequency increases, the equivalent inductance of the ferromagnetic load decreases slightly, and the equivalent resistance gradually increases, while the equivalent inductance of the non-ferromagnetic material changes little, and the equivalent resistance increases slightly; under similar shapes and similar frequencies, the equivalent inductance and equivalent resistance of the ferromagnetic load are both significantly greater than those of the non-ferromagnetic material. Taking a household induction heating power supply as an example, current technical solutions are mostly oriented to ferromagnetic pots, and cannot heat non-ferromagnetic pots, because the equivalent inductance and equivalent resistance of ferromagnetic materials and non-ferromagnetic materials are significantly different, and the current matching circuit is difficult to adapt to both parameters. When a power supply designed for heating ferromagnetic pots is used to heat non-ferromagnetic pots, the power supply is difficult to normally output power, and is prone to overcurrent and even burnout.

[0066] To address this problem, current solutions mostly involve constructing two sets of resonant circuits with bidirectional switches, and controlling the circuit operation state with the closing of the bidirectional switches to heat the two types of loads. However, the key component in this solution, the bidirectional switch, increases the switching elements of the system, and increases the cost and complexity of the system, thereby reducing the efficiency of the system. Some technologies also use multiplexing of switching tubes to construct different matching networks, but still need to increase the number of switching tubes, and the corresponding cost also needs to be increased.

[0067] Further, because the quality factor Q of the ferromagnetic load is low, LC series resonance is often used for impedance matching, while the quality factor Q of the non-ferromagnetic load is high, and LLC is mostly used for current amplification for impedance matching, at which time the current stress of the power supply is small, and the heating current can be amplified to Q times of the input current. However, because the properties of the two sets of resonant circuits are quite different, the power supply is difficult to identify the load type online, and human intervention is often needed to switch the operation mode of the circuit, which undoubtedly poses a challenge to the modernization and automation of production.

[0068] In response to the above scenarios in actual applications, we further optimize the load-adaptive induction heating power supply as shown in Figure 1 .

[0069] Specifically, the dual-gain inverter circuit module is a parallel dual-gain inverter circuit or a series dual-gain inverter circuit, and both the parallel dual-gain inverter circuit and the series dual-gain inverter circuit at least include a first switching tube , a second switching tube , a third switching tube , and a fourth switching tube .

[0070] Referring to Figure 2 and Figure 3 , Figure 2The double-gain inverter circuit module provided by the embodiment of the present application is a circuit principle diagram when the double-gain inverter circuit module is a parallel double-gain inverter circuit, Figure 3 The double-gain inverter circuit module provided by the embodiment of the present application is a circuit principle diagram when the double-gain inverter circuit module is a series double-gain inverter circuit.

[0071] As shown in the figure, Figure 2 Specifically, when the double-gain inverter circuit module is a parallel double-gain inverter circuit, the parallel double-gain inverter circuit further comprises a first input capacitor , a first end of the first input capacitor , a drain of a first switch tube and a drain of a third switch tube are connected to form a first input end of the double-gain inverter circuit module , a source of the first switch tube and a drain of a second switch tube are connected to form a first output end of the double-gain inverter circuit module , a source of the third switch tube and a drain of a fourth switch tube are connected to form a second output end of the double-gain inverter circuit module , a second end of the first input capacitor , a source of the second switch tube and a source of the fourth switch tube are connected to form a second input end of the double-gain inverter circuit module .

[0072] As shown in the figure, Figure 3 Specifically, when the double-gain inverter circuit module is a series double-gain inverter circuit, the series double-gain inverter circuit further comprises a second input capacitor and a third input capacitor , a first end of the second input capacitor , a drain of a first switch tube are connected to form a first input end of the double-gain inverter circuit module , a source of the first switch tube and a drain of a second switch tube are connected to form a first output end of the double-gain inverter circuit module , a second end of the second input capacitor , a first end of the third input capacitor , a source of the second switch tube and a drain of a third switch tube are connected, a source of the third switch tube and a drain of a fourth switch tube are connected to form a second output end of the double-gain inverter circuit module , the third input capacitor The second terminal and the fourth switching transistor The second input terminal of the dual-gain inverter circuit module is formed by connecting the source terminals. .

[0073] It should be noted that when the dual-gain inverter circuit module in this embodiment is a parallel dual-gain inverter circuit or a series dual-gain inverter circuit, the first switching transistor... Second switching transistor Third switching transistor and the fourth switching transistor It remains unchanged. Furthermore, in a parallel-type dual-gain inverter circuit, the first input capacitor is selected. In the series-type double-gain inverter circuit, the second input capacitor is selected. and the third output capacitor And the second input capacitor and the third output capacitor The same materials were used.

[0074] Specifically, the load-adaptive resonant module is an LCCLL series-parallel resonant circuit or an LCLCL series-parallel resonant circuit, and both the LCCLL series-parallel resonant circuit and the LCLCL series-parallel resonant circuit include a series inductor. Series capacitor Parallel inductors Parallel capacitors A heating coil, which is equivalent to an output inductor. and output resistance Connected in series.

[0075] Reference Figure 4 and Figure 5 , Figure 4 The circuit diagram shown is for a load-adaptive resonant module provided in this application embodiment when it is an LCCLL series-parallel resonant circuit. Figure 5 The circuit diagram for the load-adaptive resonant module provided in the embodiments of this application is an LCLCL series-parallel resonant circuit.

[0076] like Figure 4 As shown, specifically, when the load-adaptive resonant module is an LCCLL series-parallel resonant circuit, the series inductor... The first end is the first end of the load-adaptive resonant module. Series inductor The second terminal is connected in series with a capacitor. The first end is connected in series with a capacitor. The second terminal, parallel capacitor First terminal, parallel inductor First terminal, output inductor the first end of the series inductance the second end of the series inductance the second end of the output resistance the second end of the parallel inductance the output inductance the second end of the output inductance the first end of the output resistance.

[0077] As shown in Figure 5 , specifically, when the load adaptive resonant module is an LCLCL series-parallel resonant circuit, the first end of the series inductance is the first end of the load adaptive resonant module the second end of the series inductance the first end of the parallel inductance the first end of the parallel inductance the first end of the series inductance the second end of the parallel inductance the second end of the parallel inductance the second end of the output resistance the second end of the output resistance the second end of the series inductance the first end of the output inductance the second end of the output inductance the first end of the output resistance.

[0078] Referring to Figure 6 and Figure 7 , Figure 6 the control timing of the half-gain mode and the full-gain mode of the parallel dual-gain inverter circuit provided by the embodiment of the application, Figure 7 the control timing of the half-gain mode and the full-gain mode of the series dual-gain inverter circuit provided by the embodiment of the application.

[0079] Based on the aforementioned dual-gain inverter circuit module for outputting two voltage levels, we need to control the parallel dual-gain inverter circuit and the series dual-gain inverter circuit correspondingly to realize the output of two voltage levels.

[0080] Specifically, the dual-gain inverter circuit module adopts a dual-gain control method when outputting two voltage levels.

[0081] In the specific application of the embodiment, the dual-gain control method is specifically:

[0082] As shown in Figure 6 ​As shown, when the dual-gain inverter circuit module is a parallel dual-gain inverter circuit and operates in half-gain mode, the dual-gain inverter circuit operates as a half-bridge inverter circuit, with the third switching transistor... Normally open, fourth switching transistor Normally closed, first switching transistor Second switching transistor Operating at the resonant frequency Furthermore, the drive signals are complementary, and their output voltage is And 0; When the dual-gain inverter circuit module is a parallel dual-gain inverter circuit, and the parallel dual-gain inverter circuit module operates in full-gain mode, the dual-gain inverter circuit module operates as a full-bridge inverter circuit, and the first switching transistor... Second switching transistor Third switching transistor and the fourth switching transistor Operating at the resonant frequency Among them: the first switching transistor and the fourth switching transistor The drive signals are the same, and the second switching transistor... and the third switching transistor The drive signals are the same, and the drive signals of the two pairs of switching transistors are complementary, so the output voltage is... .

[0083] like Figure 7 As shown, when the dual-gain inverter circuit module is a series-type dual-gain inverter circuit, and the series-type dual-gain inverter circuit module operates in half-gain mode, the first switching transistor... Second switching transistor Third switching transistor and the fourth switching transistor Operating at frequency point With the first switching transistor Based on the first switching transistor and the fourth switching transistor The drive duty cycle is 25%, and the second switching transistor... and the third switching transistor The drive duty cycle is 75%, and the second switching transistor... Third switching transistor and the fourth switching transistor The phase lags behind the first switch transistor. The output voltage is 25%, 75%, and 50%. And 0; When the series-type dual-gain inverter circuit module operates in full-gain mode, the first switching transistor Second switching transistor Third switching transistor and the fourth switching transistor Work at resonance frequency point Wherein: the first switch tube And the fourth switch tube The driving signal is the same, the second switch tube And the third switch tube The driving signal is the same, and the output voltage of the two pairs of switch tubes is And 0.

[0084] Specifically, when the load of the heating coil is a ferromagnetic material, the output inductance And the output resistance Equivalent to the ferromagnetic output inductance And the ferromagnetic output resistance When heating the ferromagnetic material, the load adaptive induction heating power works at the resonance frequency point , which is a constant voltage output mode;

[0085] Specifically, when the heating load of the heating coil is a non-ferromagnetic material, the output inductance And the output resistance Equivalent to the non-ferromagnetic output inductance And the non-ferromagnetic output resistance When heating the non-ferromagnetic material, the load adaptive induction heating power works at the resonance frequency point , which is a constant current output mode.

[0086] In the specific application of the embodiment, according to the output power requirement, the power works in the corresponding gain mode and has the corresponding power control method.

[0087] In order to realize the constant voltage output characteristic and the constant current output characteristic at the resonance frequency point And , it is necessary to make the output characteristic independent of the equivalent resistance of the load, and the input has pure resistance and zero phase angle, so it is necessary to further constrain the load adaptive resonance module.

[0088] Specifically, the load adaptive resonance module has the following parameter constraint conditions:

[0089] The resonance frequency point Is less than the resonance frequency point ; the parallel capacitor and the parallel inductor resonate at the resonance frequency point ; the series inductor, the series capacitor, and the ferromagnetic output inductance resonate at the resonance frequency point .

[0090] In the specific application of the embodiment, the resonance frequency point Is less than the resonance frequency point ; the resonance frequency point Corresponds to the resonance angular frequency point , resonance frequency point , corresponding resonance angular frequency point ; parallel capacitance and parallel inductance at resonance frequency point parallel resonance, i.e. ; series inductance , series capacitance , ferromagnetic output inductance at resonance frequency point series resonance, i.e. .

[0091] When the load adaptive resonance module is an LCCLL series-parallel resonance circuit, at the resonance frequency point , the impedance size of the series inductance and the series capacitance in series is equal to the impedance size of the non-ferromagnetic output inductance, and the impedance size of the parallel capacitance and the parallel inductance in parallel, and then in series with the series inductance and the series capacitance is 0.

[0092] In the specific application of the embodiment, when the load adaptive resonance module is an LCCLL series-parallel resonance circuit, at the resonance frequency point , the impedance size of the series inductance and the series capacitance in series is equal to the impedance size of the non-ferromagnetic output inductance , i.e. , the impedance size of the parallel capacitance and the parallel inductance in parallel, and then in series with the series inductance and the series capacitance is 0, i.e. ; after meeting the above constraint conditions, the parameter values of the LCCLL series-parallel resonance circuit are:

[0093]

[0094]

[0095]

[0096]

[0097] When the load adaptive resonance module is an LCLCL series-parallel resonance circuit, at the resonance frequency point , the impedance size of the non-ferromagnetic output inductance and the series capacitance in series is equal to the impedance size of the series inductance, and the impedance size of the parallel capacitance and the parallel inductance in parallel, and then in series with the series inductance is 0.

[0098] In a specific application of this embodiment, when the load-adaptive resonant module is an LCLCL series-parallel resonant circuit, at the resonant frequency point... Non-ferromagnetic output inductor With series capacitor The impedance after series connection and the series inductance The impedances are equal in magnitude, that is Parallel capacitors with parallel inductor After being connected in parallel, it is then connected in series with an inductor. The impedance after series connection is 0, that is... After satisfying the above constraints, the parameter values ​​of the LCLCL series-parallel resonant circuit are:

[0099]

[0100]

[0101]

[0102]

[0103] Reference Figure 8 , Figure 8 The input impedance magnitude and input impedance angle curves of the load-adaptive resonant module provided in the embodiments of this application when the load is unloaded, ferromagnetic material, or non-ferromagnetic material.

[0104] When the load-adaptive resonant module is either an LCCLL series-parallel resonant circuit or an LCCLL series-parallel resonant circuit, such as Figure 8 As shown: When the load is a ferromagnetic material, the load-adaptive resonant module at the resonant frequency point The input impedance angle is 0; when the load is a non-ferromagnetic material, the load-adaptive resonant module reaches the resonant frequency point. The input impedance angle is 0. The switching transistor can achieve zero-voltage turn-on and low-current turn-off in both modes, resulting in low losses.

[0105] Figure 9 The relationship between the output voltage-input voltage gain, output current-input voltage gain, and frequency of the load-adaptive induction heating power supply provided in the embodiments of this application is shown.

[0106] like Figure 9As shown: when the load is ferromagnetic material, its equivalent resistance changes, while the output voltage-input voltage gain of the power supply is constant, the power supply has constant voltage characteristic; when the load is non-ferromagnetic material, its equivalent resistance changes, while the output current-input voltage gain of the power supply is constant, the power supply has constant current characteristic. Therefore, the power supply has good output characteristics independent of the equivalent resistance of the load when facing varying loads.

[0107] In response to the different load types mentioned above, higher demands are put forward for the induction heating power supply. In order to realize online identification of the load type without artificial intervention, we set up a corresponding load adaptive detection method for the load adaptive induction heating power supply.

[0108] Specifically, the load adaptive induction heating power supply is provided with a corresponding load adaptive detection method for online identification of the load type to work in the corresponding heating mode, which comprises:

[0109] The power supply always works in the half-gain mode, and the phase relationship is judged by sampling the output voltage and output current of the double-gain inverter circuit module; the starting working frequency of the power supply The mathematical expression is:

[0110]

[0111] Among them, and are both resonance frequency points.

[0112] Referring to Figure 10 , Figure 10 the load adaptive detection method provided by the embodiment of the present application is a schematic diagram of selecting a plurality of frequency points by dichotomy.

[0113] As shown in Figure 10 , based on the starting working frequency , a plurality of frequency points are selected by dichotomy, and the mathematical expression corresponding to the plurality of frequency points is at least:

[0114]

[0115]

[0116]

[0117]

[0118] Among them, ;

[0119] Make the power supply work at the starting working frequency for a short time, and then make the power supply constantly approach the frequency points on both sides, and make the following judgments when approaching:

[0120] If the phase relationship is not fixed, the coil is unloaded, and the power supply needs to be turned off immediately;

[0121] If the power supply is to the left side frequency point In the process of approaching, the current always leads the voltage, or the current first leads the voltage, and then the current always lags behind the voltage, which is a ferromagnetic load;

[0122] If the power supply is to the right side frequency point In the process of approaching, the current always lags behind the voltage, or the current first leads the voltage, and then the current always lags behind the voltage, which is a non-ferromagnetic load.

[0123] In the specific application of the embodiment, after confirming the load type, based on the dual-gain inverter circuit module and the load adaptive resonance module, we set a wide range high efficiency power control method for the load adaptive induction heating power supply.

[0124] Specifically, based on the online identification of the load type, the load adaptive induction heating power supply is provided with a corresponding power control method, which includes:

[0125] The preset output power is obtained, the preset output power is compared with the rated output power, and the following judgment is made:

[0126] When the preset output power is greater than one fourth of the rated output power, the full gain mode is adopted, and the phase shift control is adopted, and the output power is adjusted by adjusting the lagging phase angle of the first switch tube , the fourth switch tube to the first switch tube , the second switch tube ;

[0127] When the preset output power is less than one fourth of the rated output power, the half gain mode is adopted, and the output power is adjusted by changing the pulse density of the drive;

[0128] After determining the gain mode, the output voltage and the output current of the dual-gain inverter circuit module are detected synchronously to obtain the real-time output power, and the preset output power is adjusted based on the requirement of the real-time output power to redetermine the gain mode.

[0129] Referring to Figure 11 , Figure 11 The schematic diagram of the wide range high efficiency power control method provided by the embodiment of the application; in the figure, (a) is the relationship between the output power and the pulse density in the half gain mode, and (b) is the relationship between the output power and the phase shift angle in the full gain mode.

[0130] As Figure 11The power control method adopts different gain modes and control variables at different output powers, maintains small switching loss and conduction loss of the switching tube, and enables the circuit to achieve better constant voltage and constant current output characteristics and zero voltage switching effect, and has high efficiency.

[0131] Based on the above design, the load adaptive induction heating power supply disclosed in the embodiment at least achieves the following technical effects:

[0132] 1. The inverter part adopts a double-gain inverter circuit module, and through a double-gain control method, two different voltage outputs of different levels are realized at two gains, and the output power can be flexibly adjusted.

[0133] 2. The load adaptive resonance module realizes constant voltage output characteristics and constant current output characteristics independent of the equivalent resistance of the load at two resonance frequency points through parameter constraints, and has pure resistive input and zero input phase angle, and the switching tube has low loss.

[0134] 3. Based on the characteristics of the double-gain inverter circuit module and the load adaptive resonance module, a load adaptive detection method is adopted, which can identify whether the load is empty, ferromagnetic material or non-ferromagnetic material online.

[0135] 4. The load adaptive induction heating power supply can realize high efficiency, flexible heating power, and compatible heating of ferromagnetic and non-ferromagnetic loads with a wide range of high efficiency power control method, and has low overall complexity and cost.

[0136] In summary, the load adaptive induction heating power supply of the embodiment solves the technical problems of high cost and complexity and low efficiency of the bidirectional switch in the prior art.

[0137] Finally, it should be noted that: the above only for the preferred embodiments of the present application, and not for limiting the present application, although the present application has been described in detail with reference to the foregoing embodiments, for those skilled in the art, it still can modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features, any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application, should be included in the protection scope of the present application.

Claims

1. A load adaptive inductive heating power supply, characterized by, The double-gain inverter circuit module and the load adaptive resonance module are included, wherein the double-gain inverter circuit module is used to output two levels of voltage, and the output voltage level is determined based on the output power; the load adaptive resonance module is used to adapt to the ferromagnetic load or the non-ferromagnetic load, and the adaptation at least includes impedance matching. The first input end of the double-gain inverter circuit module is connected with the positive pole of the preset output power supply, the second input end of the double-gain inverter circuit module is connected with the negative pole of the output power supply, the first output end of the double-gain inverter circuit module is connected with the first end of the load adaptive resonance module, and the second output end of the double-gain inverter circuit module is connected with the second end of the load adaptive resonance module. The double-gain inverter circuit module is a parallel double-gain inverter circuit or a series double-gain inverter circuit, and the parallel double-gain inverter circuit and the series double-gain inverter circuit at least include a first switch tube, a second switch tube, a third switch tube and a fourth switch tube. When the double-gain inverter circuit module is the parallel double-gain inverter circuit, the parallel double-gain inverter circuit further includes a first input capacitor; the first end of the first input capacitor, the drain of the first switch tube and the drain of the third switch tube are connected to form the first input end of the double-gain inverter circuit module; the source of the first switch tube and the drain of the second switch tube are connected to form the first output end of the double-gain inverter circuit module; the source of the third switch tube and the drain of the fourth switch tube are connected to form the second output end of the double-gain inverter circuit module; the second end of the first input capacitor, the source of the second switch tube and the source of the fourth switch tube are connected to form the second input end of the double-gain inverter circuit module. When the double-gain inverter circuit module is the series double-gain inverter circuit, the series double-gain inverter circuit further includes a second input capacitor and a third input capacitor; the first end of the second input capacitor and the drain of the first switch tube are connected to form the first input end of the double-gain inverter circuit module, the source of the first switch tube and the drain of the second switch tube are connected to form the first output end of the double-gain inverter circuit module, the second end of the second input capacitor, the first end of the third input capacitor, the source of the second switch tube and the drain of the third switch tube are connected, the source of the third switch tube and the drain of the fourth switch tube are connected to form the second output end of the double-gain inverter circuit module, and the second end of the third input capacitor and the source of the fourth switch tube are connected to form the second input end of the double-gain inverter circuit module.

2. The load adaptive inductive heating power supply of claim 1, wherein, The load adaptive resonance module is an LCCLL series-parallel resonance circuit or an LCLCL series-parallel resonance circuit, and the LCCLL series-parallel resonance circuit and the LCLCL series-parallel resonance circuit at least include a series inductor, a series capacitor, a parallel inductor, a parallel capacitor and a heating coil, and the heating coil is equivalent to the series connection of an output inductor and an output resistor.

3. The load adaptive inductive heating power supply of claim 2, wherein, When the load adaptive resonant module is an LCCLL series-parallel resonant circuit, the first end of the series inductor is the first end of the load adaptive resonant module, the second end of the series inductor and the first end of the series capacitor are connected, the second end of the series capacitor, the first end of the parallel capacitor, the first end of the parallel inductor, and the first end of the output inductor are connected, the second end of the parallel capacitor, the second end of the parallel inductor, and the second end of the output resistor are connected to be the second end of the load adaptive resonant module, the second end of the output inductor and the first end of the output resistor are connected; When the load adaptive resonant module is an LCLCL series-parallel resonant circuit, the first end of the series inductor is the first end of the load adaptive resonant module, the second end of the series inductor, the first end of the parallel capacitor, the first end of the parallel inductor, and the first end of the series capacitor are connected, the second end of the parallel capacitor, the second end of the parallel inductor, and the second end of the output resistor are connected to be the second end of the load adaptive resonant module, the second end of the series capacitor and the first end of the output inductor are connected, and the second end of the output inductor and the first end of the output resistor are connected.

4. The load adaptive inductive heating power supply of claim 2, wherein, The dual-gain inverter circuit module adopts a dual-gain control method when outputting two levels of voltage; The dual-gain control method specifically includes: When the double-gain inverter circuit module is a parallel double-gain inverter circuit, and the parallel double-gain inverter circuit module works in a half-gain mode, the operation of the double-gain inverter circuit is a half-bridge inverter circuit, the third switch tube is always on, the fourth switch tube is always off, and the first switch tube and the second switch tube work at a resonant frequency point , and the driving signals are complementary, and the output voltage is and 0; when the double-gain inverter circuit module is a parallel double-gain inverter circuit, and the parallel double-gain inverter circuit module works in a full-gain mode, the operation of the double-gain inverter circuit module is a full-bridge inverter circuit, the first switch tube, the second switch tube, the third switch tube and the fourth switch tube work at a resonant frequency point , wherein: the first switch tube and the fourth switch tube have the same driving signal, the second switch tube and the third switch tube have the same driving signal, and the two pairs of switch tubes have complementary driving signals, and the output voltage is ; When the dual-gain inverter circuit module is a series dual-gain inverter circuit, and the series dual-gain inverter circuit module works in a half-gain mode, the first switch tube, the second switch tube, the third switch tube and the fourth switch tube work at a frequency point , the first switch tube and the fourth switch tube have a drive duty ratio of 25%, the second switch tube and the third switch tube have a drive duty ratio of 75%, the second switch tube, the third switch tube and the fourth switch tube have a phase lag of 25%, 75% and 50% respectively, and the output voltage is and 0; when the series dual-gain inverter circuit module works in a full-gain mode, the first switch tube, the second switch tube, the third switch tube and the fourth switch tube work at a resonant frequency point , the first switch tube and the fourth switch tube have the same drive signal, the second switch tube and the third switch tube have the same drive signal, and the two pairs of switch tubes have complementary drive signals, and the output voltage is and 0.

5. The load adaptive inductive heating power supply of claim 4, wherein, When the load of the heating coil is ferromagnetic material, the output inductance and output resistance are equivalent to ferromagnetic output inductance and ferromagnetic output resistance; when the ferromagnetic material is heated, the load adaptive induction heating power works at the resonance frequency point is a constant voltage output mode; When the heating load of the heating coil is a non-ferromagnetic material, the output inductance and output resistance are equivalent to non-ferromagnetic output inductance and non-ferromagnetic output resistance; when the non-ferromagnetic material is heated, the load adaptive induction heating power supply works at the resonance frequency point It is constant current output mode.

6. The load adaptive inductive heating power supply of claim 5, wherein, The load adaptive resonant module has the following parameter constraint conditions: resonance frequency point sub-resonance frequency point parallel capacitor and parallel inductor at resonance frequency point parallel resonance; series inductor, series capacitor, ferromagnetic output inductor at resonance frequency point series resonance; When the load adaptive resonant module is an LCCLL series-parallel resonant circuit, at a resonant frequency point , the impedance of the series inductor and the series capacitor connected in series is equal to the impedance of the non-ferromagnetic output inductor, and the impedance of the parallel capacitor and the parallel inductor connected in parallel is 0. When the load adaptive resonant module is an LCLCL series-parallel resonant circuit, at a resonant frequency point , the impedance of the non-ferromagnetic output inductor and the series capacitor in series is equal to the impedance of the series inductor, and the impedance of the parallel capacitor and the parallel inductor in parallel and then in series with the series inductor is 0.

7. The load adaptive inductive heating power supply of claim 1, wherein, The load adaptive induction heating power supply is provided with a corresponding load adaptive detection method for online identification of the load type to work in the corresponding heating mode, and the load adaptive detection method includes: The power supply always works in half gain mode, and the phase relation is judged by sampling the output voltage and output current of the double gain inverter circuit module; the starting working frequency of the power supply is expressed by the following mathematical expression: wherein, and are resonance frequency points; based on the initial operating frequency a number of frequency points are selected by bisection, the mathematical expression corresponding to the number of frequency points is at least: wherein ; Operating the power supply at a starting operating frequency In a short time, the power supply is constantly approaching the frequency points on both sides, and the following judgments are made when approaching: If the phase relationship is not fixed, the coil is unloaded, and the power supply needs to be turned off immediately; If the power supply is to the left of the frequency point If the current always leads the voltage, or first leads and then always lags the voltage, the load is ferromagnetic. If the power supply is to the right of the frequency point In the process of approaching, the current always lags behind the voltage, or the current leads the voltage first, and then the current always lags behind the voltage, which is a non-ferromagnetic load.

8. The load adaptive inductive heating power supply of claim 7, wherein, Based on the online identification of the load type, the load adaptive induction heating power supply is provided with a corresponding power control method, and the power control method includes: The preset output power is obtained, the preset output power is compared with the rated output power, and the following judgment is made: When the preset output power is greater than one-fourth of the rated output power, a full-gain mode is adopted, and a phase shift control is adopted to adjust the lagging phase angle of the third switch tube and the fourth switch tube to the first switch tube and the second switch tube, and to adjust the output power; When the preset output power is less than one-fourth of the rated output power, a half-gain mode is adopted, and the output power is adjusted by changing the pulse density of the drive; After the gain mode is determined, the output voltage and the output current of the dual-gain inverter circuit module are detected synchronously to obtain the real-time output power, and the preset output power is adjusted based on the requirement of the real-time output power to redetermine the gain mode.

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