Control method of wide-gain LLC resonant converter, computer equipment and storage medium

Abstract

The invention discloses a control method of a wide-gain LLC resonant converter, computer equipment and a storage medium, and the control method comprises the steps: carrying out the APWM (Asymmetric Pulse Width Modulation) mode control of a secondary side switching tube according to the gain change condition of an output voltage, and reducing the light no-load loss of a system; in addition, sufficient dead time is set, so that ZVS of primary and secondary side switch tubes is realized; on the premise of widening the voltage gain range of the converter, the high efficiency of the converter is ensured. The control method of the wide-gain LLC resonant converter provided by the invention has higher practicability and reliability, can meet the gain change requirement in a full-voltage range, and is flexible.

Description

Technical Field

[0001] The present invention relates to the technical field of switching converters, and in particular to a control method, a computer device and a storage medium for a wide-gain LLC resonant converter. Background Art

[0002] With the rapid development of power electronics, switching converters are increasingly widely used, and high power density and high efficiency have become the development trend of the industry. At the same time, people have put forward higher requirements for switching converters, such as wide input voltage range, small size, high reliability, etc. LLC resonant converters have occupied an important position in the power supply industry due to their many advantages such as low noise, low stress, and low switching loss.

[0003] Traditional LLC resonant converters generally need to adjust the output voltage by changing the switching frequency. When the input voltage range is wide, the switching frequency needs to change within a wide range. When the frequency is too low, it is difficult to achieve zero voltage turn-on. When the frequency is too high, it is difficult to achieve zero current turn-off. At the same time, the wide frequency brings great difficulties to the design of the transformer and the control of the circuit. Therefore, when the operating frequency changes in a wide range, the efficiency of the traditional LLC resonant converter decreases significantly.

[0004] In order to overcome the shortcomings of PFM control and narrow the frequency adjustment range, scholars in this field have studied a variety of hybrid control methods. Among them, Li Ju, Ruan Xinbo and other researchers from Nanjing University of Aeronautics and Astronautics published a paper in 2013 entitled "Hybrid Control Strategy for Full-Bridge LLC Resonant Converter", proposing a novel frequency conversion-phase shift hybrid control strategy to effectively narrow the frequency adjustment range. However, in order to ensure the soft switching and efficiency performance of the converter, the gain adjustment capability of the converter under control of this hybrid control strategy is limited.

[0005] In order to broaden the application scenarios of LLC resonant converters, utilize the advantages of LLC resonant converters as much as possible, and solve the contradiction between wide gain and high efficiency of traditional LLC resonant converters, patent application number CN202011174959 discloses a wide gain control method of LLC resonant converter and its resonant converter, but the patent only briefly describes the wide gain implementation method. In actual applications, when the converter switches from PFM mode to variable duty cycle mode in the early stage, the variable duty cycle mode has insufficient regulation ability, which is prone to output current spikes caused by input voltage fluctuations, and the actual use effect is not good. Summary of the invention

[0006] The present invention aims to overcome at least one defect in the above-mentioned prior art, and provides a control method, a computer device and a storage medium for a wide-gain LLC resonant converter, samples the output electrical parameters of the converter, and performs error processing with the reference electrical parameters to realize asymmetrical pulse width modulation (APWM, Asymmetrical Pulse Width Modulation) modal control of the secondary side switch tube, effectively widens the voltage gain range of the converter, reduces the light no-load loss of the system, and improves the efficiency and stability of the converter.

[0007] In a first aspect, a control method for a wide-gain LLC resonant converter is provided, wherein the resonant converter comprises a DC input source V in (I), a primary inverter switch circuit (II), a resonant cavity (III), a transformer (IV), a secondary rectifier circuit (V) and a filter output circuit (VI); the secondary rectifier circuit (V) includes a fifth secondary switch tube S5, a sixth secondary switch tube S6, a seventh power device and an eighth power device, the driving pulses of the fifth secondary switch tube S5 and the sixth secondary switch tube S6 are complementary, the duty cycle of the fifth secondary switch tube S5 is D, the duty cycle of the sixth secondary switch tube S6 is 1-D, the switching frequencies of all the switches of the secondary rectifier circuit (V) are higher than the series resonant frequency, and the control method includes:

[0008] Sampling the output electrical parameters of the resonant converter, and performing error processing on the collected output electrical parameters and reference electrical parameters to obtain error parameters;

[0009] A control signal is generated according to the error parameter, and a duty cycle D is controlled according to the control signal to adjust the output voltage gain of the resonant converter, wherein the control signal decreases as the output electrical parameter increases.

[0010] Preferably, controlling the duty cycle D according to the control signal to adjust the output voltage gain of the resonant converter specifically includes:

[0011] comparing the control signal with a preset first reference value;

[0012] When the control signal is lower than the first reference value, the duty cycle D of the fifth switch tube S5 on the secondary side is controlled to remain unchanged, and the internal phase shift angle of the switch tube of the primary inverter switch circuit (II) is adjusted according to the control signal, wherein the internal phase shift angle increases as the control signal decreases, and the output voltage gain decreases as the internal phase shift angle increases;

[0013] When the control signal is higher than the first reference value, the internal phase shift angle of the switch tube of the primary inverter switch circuit (II) is controlled to remain fixed, and the duty cycle D of the secondary fifth switch tube S5 is adjusted according to the control signal, wherein the duty cycle D increases with the increase of the control signal, and the output voltage gain increases with the increase of the duty cycle D.

[0014] Preferably, controlling the duty cycle D according to the control signal to adjust the output voltage gain of the resonant converter specifically includes:

[0015] Comparing the control signal with a preset first reference value and a second reference value, wherein the first reference value is smaller than the second reference value;

[0016] When the control signal is lower than the first reference value, the switching frequency of the switch tube of the primary inverter switch circuit (II) and the duty cycle D of the fifth switch tube S5 of the secondary side are controlled to remain unchanged, and the internal phase shift angle of the switch tube of the primary inverter switch circuit (II) is adjusted according to the control signal, wherein the internal phase shift angle decreases as the control signal increases, and the output voltage gain increases as the internal phase shift angle decreases;

[0017] When the control signal is higher than the first reference value and lower than the second reference value, the internal phase shift angle of the switch tube of the primary inverter switch circuit (II) and the duty cycle D of the secondary fifth switch tube S5 are controlled to remain unchanged, and the switching frequency of the switch tube of the primary inverter switch circuit (II) is adjusted according to the control signal, wherein the switching frequency decreases as the control signal increases, and the output voltage gain increases as the switching frequency decreases;

[0018] When the control signal is higher than the second reference value, the switching frequency of the switch tube of the primary inverter switch circuit (II) and the internal phase shift angle of the switch tube of the primary inverter switch circuit (II) are controlled to remain unchanged, and the duty cycle D of the secondary side fifth switch tube S5 is adjusted according to the control signal, wherein the duty cycle D increases with the increase of the control signal, and the output voltage gain increases with the increase of the duty cycle D.

[0019] Preferably, controlling the duty cycle D according to the control signal to adjust the output voltage gain of the resonant converter specifically includes:

[0020] comparing the control signal with a preset second reference value;

[0021] When the control signal is lower than the second reference value, the external phase shift angle between the switch tube of the primary inverter switch circuit (II) and the switch tube of the secondary rectifier circuit (V) is controlled to remain unchanged, and the duty cycle D of the fifth switch tube S5 of the secondary side is adjusted according to the control signal, wherein the duty cycle D increases with the increase of the control signal, and the output voltage gain increases with the increase of the duty cycle;

[0022] When the control signal is higher than the second reference value, the duty cycle D of the fifth switch tube S5 on the secondary side is controlled to remain unchanged, and the external phase shift angle between the switch tube of the primary inverter switch circuit (II) and the switch tube of the secondary rectifier circuit (V) is adjusted according to the control signal, wherein the external phase shift angle increases with the increase of the control signal, and the output voltage gain increases with the increase of the external phase shift angle.

[0023] Preferably, controlling the duty cycle D according to the control signal to adjust the output voltage gain of the resonant converter specifically includes:

[0024] Comparing the control signal with a preset first reference value and a second reference value, wherein the first reference value is smaller than the second reference value;

[0025] When the control signal is lower than the first reference value, the external phase shift angle between the switch tube of the primary inverter switch circuit (II) and the switch tube of the secondary rectifier circuit (V) and the duty cycle D of the secondary fifth switch tube S5 are controlled to remain unchanged, and the switching frequency of the switch tube of the primary inverter switch circuit (II) is adjusted according to the control signal, wherein the switching frequency decreases as the control signal increases, and the output voltage gain increases as the switching frequency decreases;

[0026] When the control signal is higher than the first reference value and lower than the second reference value, the external phase shift angle between the switch tube of the primary inverter switch circuit (II) and the switch tube of the secondary rectifier circuit (V) and the switching frequency of the switch tube of the primary inverter switch circuit (II) are controlled to remain unchanged, and the duty cycle D of the secondary fifth switch tube S5 is adjusted according to the control signal, wherein the duty cycle D increases with the increase of the control signal, and the output voltage gain increases with the increase of the duty cycle D;

[0027] When the control signal is higher than the second reference value, the switching frequency of the switch tube of the primary inverter switch circuit (II) and the duty cycle D of the secondary fifth switch tube S5 are controlled to remain unchanged, and the external phase shift angle between the switch tube of the primary inverter switch circuit (II) and the switch tube of the secondary rectifier circuit (V) is adjusted according to the control signal, wherein the external phase shift angle increases with the increase of the control signal, and the output voltage gain increases with the increase of the external phase shift angle.

[0028] Preferably, controlling the duty cycle D according to the control signal to adjust the output voltage gain of the resonant converter specifically includes:

[0029] comparing the control signal with a preset first reference value;

[0030] When the control signal is lower than the first reference value, the duty cycle D of the fifth switch tube S5 on the secondary side is controlled to remain unchanged, and the duty cycle of the switch tube of the primary inverter switch circuit (II) is adjusted according to the control signal, wherein the duty cycle of the switch tube of the primary inverter switch circuit (II) decreases as the control signal decreases, and the output voltage gain decreases as the duty cycle of the switch tube of the primary inverter switch circuit (II) decreases;

[0031] When the control signal is higher than the first reference value, the duty cycle of the switch tube of the primary inverter switch circuit (II) is controlled to remain fixed, and the duty cycle D of the secondary fifth switch tube S5 is adjusted according to the control signal, wherein the duty cycle D of the secondary fifth switch tube S5 increases with the increase of the control signal, and the output voltage gain increases with the increase of the duty cycle D of the secondary fifth switch tube S5.

[0032] Preferably, the output electrical parameter is output voltage, output current or output power.

[0033] In a second aspect, a computer device is provided, comprising a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the above method when executing the computer program.

[0034] According to a third aspect, a computer-readable storage medium is provided, on which a computer program is stored, and when the computer program is executed by a processor, the steps of the method described above are implemented.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1) The control method of the wide-gain LLC resonant converter proposed in the present invention can realize the secondary side APWM mode control, effectively broaden the voltage gain range of the converter, especially reduce the light no-load loss of the system, and realize the wide gain and high efficiency of the converter;

[0037] 2) The control method of the wide-gain LLC resonant converter proposed in the present invention has higher practicality and reliability, can meet the gain change requirements within the full voltage range, and is more flexible and can be extended to a modal control scheme under a wider voltage range. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 A circuit diagram of a wide-gain LLC resonant converter according to a preferred embodiment of the present invention;

[0039] Figure 2 It is the key working waveform of the disclosed PFM control;

[0040] Figure 3 The switch tube drive waveform and key working waveform of the primary side APWM control have been disclosed;

[0041] Figure 4 It is the published output gain curve of primary side APWM control;

[0042] Figure 5 The wide gain LLC resonant converter of the preferred embodiment of the present invention adopts the secondary side active switch tube APWM control secondary side switch tube driving waveform and key working waveform;

[0043] Figure 6 A schematic diagram of mode switching of a wide-gain LLC resonant converter in a preferred embodiment of the present invention using phase-shift control in a primary switch tube and APWM control in a secondary switch tube;

[0044] Figure 7 A schematic diagram of mode switching of a wide-gain LLC resonant converter in a preferred embodiment of the present invention using external phase-shift control of primary and secondary switch tubes and APWM control of secondary switch tubes;

[0045] Figure 8 A schematic diagram of mode switching of a wide-gain LLC resonant converter according to a preferred embodiment of the present invention, which adopts pulse frequency modulation of a primary switch tube, phase shift control within the primary switch tube, and APWM control of a secondary switch tube;

[0046] Fig. 9 A schematic diagram of mode switching of a wide-gain LLC resonant converter according to a preferred embodiment of the present invention, which adopts phase shift control in the primary switch tube, pulse frequency modulation of the primary switch tube, and APWM control of the secondary switch tube;

[0047] Fig.10 A schematic diagram of mode switching of a wide-gain LLC resonant converter according to a preferred embodiment of the present invention using pulse width modulation of a primary switch tube and APWM control of a secondary switch tube;

[0048] Fig.11 This is a schematic diagram of mode switching of a wide-gain LLC resonant converter according to a preferred embodiment of the present invention using APWM control of the primary switch tube and APWM control of the secondary switch tube. DETAILED DESCRIPTION

[0049] The technical solution of the present invention is described below in conjunction with the accompanying drawings and embodiments so that those skilled in the art can better understand the invention. However, the specific implementation of the technical solution of the present invention is not limited thereto.

[0050] In this embodiment, a control method for a wide-gain LLC resonant converter is provided, wherein the resonant converter includes a DC input source V inⅠ, primary inverter switch circuit Ⅱ, resonant cavity Ⅲ, transformer Ⅳ, secondary rectifier circuit Ⅴ and filter output circuit Ⅵ; the secondary rectifier circuit Ⅴ includes a secondary fifth switch tube S5, a secondary sixth switch tube S6, a seventh power device and an eighth power device, the driving pulses of the secondary fifth switch tube S5 and the secondary sixth switch tube S6 are complementary, the duty cycle of the secondary fifth switch tube S5 is D, the duty cycle of the secondary sixth switch tube S6 is 1-D, the switching frequency of all switches of the secondary rectifier circuit V is higher than the series resonant frequency, and the control method includes:

[0051] Sampling the output electrical parameters of the resonant converter, and performing error processing on the collected output electrical parameters and reference electrical parameters to obtain error parameters;

[0052] A control signal is generated according to the error parameter, and a duty cycle D is controlled according to the control signal to adjust the output voltage gain of the resonant converter, wherein the control signal decreases as the output electrical parameter increases.

[0053] Preferably, controlling the duty cycle D according to the control signal to adjust the output voltage gain of the resonant converter specifically includes:

[0054] comparing the control signal with a preset first reference value;

[0055] When the control signal is lower than the first reference value, the duty cycle D of the fifth switch tube S5 on the secondary side is controlled to remain unchanged, and the internal phase shift angle of the switch tube of the primary inverter switch circuit II is adjusted according to the control signal, wherein the internal phase shift angle increases as the control signal decreases, and the output voltage gain decreases as the internal phase shift angle increases;

[0056] When the control signal is higher than the first reference value, the internal phase shift angle of the switch tube of the primary inverter switch circuit II is controlled to remain fixed, and the duty cycle D of the secondary fifth switch tube S5 is adjusted according to the control signal, wherein the duty cycle D increases with the increase of the control signal, and the output voltage gain increases with the increase of the duty cycle D.

[0057] Specifically, the output electrical parameter is output voltage, output current or output power. In a specific implementation process, the output electrical parameter is output voltage.

[0058] like Figure 1 As shown, it is a topological structure diagram of a full-bridge LLC resonant converter, wherein the resonant converter includes a DC input source V in Ⅰ, primary side inverter switch circuit Ⅱ, LLC resonant cavity Ⅲ, transformer Ⅳ, secondary side full-bridge rectifier circuit Ⅴ and filter output circuit Ⅵ;

[0059] In specific implementation, its structure is as follows:

[0060] The primary side inverter switch circuit II includes a primary side first switch tube S1, a primary side second switch tube S2, a primary side third switch tube S3, and a primary side fourth switch tube S4;

[0061] LLC resonant cavity III includes the resonant capacitor C r , resonant inductor L r , Excitation inductance L m ;

[0062] Transformer IV is a high-frequency isolation transformer with a transformation ratio of n, n = N p :N s ; N p Indicates the number of turns of the primary winding of the transformer, N s Indicates the number of turns of the secondary winding of the transformer;

[0063] The secondary side rectifier circuit V includes a fifth secondary side active switch tube S5, a sixth secondary side active switch tube S6, a seventh secondary side active switch tube S7, and an eighth secondary side active switch tube S8;

[0064] The secondary side filter output circuit VI includes an output filter capacitor C o and load R o ;

[0065] Specifically, when the duty cycle D of the fifth switch tube S5 of the secondary side is adjusted according to the control signal, the first switch tube S1 and the fourth switch tube S4 of the primary side inverter switch circuit II share the same driving pulse, and the duty cycle is 0.5 (ignoring the dead time); the second switch tube S2 and the third switch tube S3 of the primary side share the same driving pulse, and the duty cycle is 0.5 (ignoring the dead time); the driving pulse of the first switch tube S1 of the primary side is complementary to the driving pulse of the second switch tube S2 of the primary side, and the third switch tube S3 of the primary side is turned on. The driving pulse of the switch tube S3 is complementary to the driving pulse of the fourth switch tube S4 on the primary side and is turned on; the driving pulse duty ratio of the fifth switch tube S5 of the secondary side full-bridge rectifier circuit V and the eighth switch tube S8 on the secondary side is D (ignoring the dead time); the driving pulse duty ratio of the sixth switch tube S6 of the secondary side full-bridge rectifier circuit V and the seventh switch tube S7 on the secondary side is 1-D (ignoring the dead time); in addition, the driving pulse of the fifth switch tube S5 of the secondary side of the secondary full-bridge rectifier circuit V is complementary to the driving pulse of the sixth switch tube S6 on the secondary side.

[0066] It should be noted that the secondary rectifier circuit V can be a full-bridge rectifier circuit, and the secondary side can also be a semi-active bridge rectifier circuit composed of two uncontrolled rectifier devices and two switch tubes. The two switch tubes can be placed Figure 1The right bridge arm of the rectifier circuit shown can also be placed on the left bridge arm of the rectifier circuit, can also be placed on the two lower bridge arms of the rectifier circuit, and can also be placed on the two upper bridge arms of the rectifier circuit. The above circuits are all semi-active bridge rectifier circuits, and the circuit principles are completely equivalent. In addition, two back-to-back active switching tubes are connected to the secondary side of the transformer. The control method described in this embodiment is applicable to the above circuits. Next, the control method is applied to the secondary rectifier circuit V as a full-bridge rectifier circuit as an example for explanation.

[0067] In the published PFM control technology, Figure 2 As shown, when the current flows through the resonant inductor L r The resonant current i Lr and the current flowing through the magnetizing inductance L m The excitation current i Lm When the current i flowing through the fifth active switch tube S5 of the secondary side and the eighth active switch tube S8 of the secondary side is equal, D1 and the current i flowing through the sixth active switch tube S6 of the secondary side and the seventh active switch tube S7 of the secondary side D2 are all 0, which means that the resonant current does not transfer energy to the secondary side; in this stage, the resonant current i Lr A circulating current will be formed on the primary side of the transformer, resulting in circulating current loss, which significantly reduces the conversion efficiency of the resonant converter.

[0068] Figure 3 The switch tube drive waveform and key working waveform of the disclosed primary side APWM control; in the figure, V gs1 V represents the driving pulse of the first primary switch tube S1 and the fourth primary switch tube S4; gs2 represents the driving pulse of the second switch tube S2 of the primary lagging bridge arm and the third switch tube S3 of the primary side; i Lr Represents the current flowing through the resonant inductor L r The resonant current, i Lm Indicates the current flowing through the magnetizing inductance L m The excitation current i O Represents the current waveform flowing to the output port;

[0069] Figure 3It can be seen that in the disclosed primary APWM control technology, the control variable is a single variable: the duty cycle of the primary switch tube; the first primary switch tube S1, the second primary switch tube S2, the third primary switch tube S3, and the fourth primary switch tube S4 operate at a fixed switching frequency, and the first primary switch tube S1 and the fourth primary switch tube S4 share the same drive pulse, and the duty cycle is D (ignoring the dead time); the second primary switch tube S2 and the third primary switch tube S3 share the same drive pulse, and the duty cycle is 1-D (ignoring the dead time); the drive pulse of the first primary switch tube S1 and the drive pulse of the second primary switch tube S2 are complementary to each other, and the drive pulse of the third primary switch tube S3 and the drive pulse of the fourth primary switch tube S4 are complementary to each other; the output gain capability of the converter is broadened within the same switching frequency range, and the primary circulating current is eliminated, thereby further improving the converter efficiency.

[0070] In the disclosed primary side APWM control technology, such as Figure 4 As shown, it is a curve showing the relationship between the converter output gain and the primary switch duty cycle D. When the duty cycle is 0.5, the converter reaches the maximum output gain. The converter can only be buck-regulated through the primary APWM control, which is not suitable for resonant converters that require boost regulation.

[0071] Under the same output voltage, Figure 5 The secondary side switch tube driving waveform of the control method described in this embodiment; Figure 5 In, V gs5 、V gs6 Respectively represent the driving pulses of the fifth switch tube S5 of the secondary side and the sixth switch tube S6 of the secondary side; i Lr Represents the current flowing through the resonant inductor L r The resonant current;

[0072] This embodiment adopts the secondary side APWM control method, and there is a control variable: the duty cycle D of the secondary side fifth switch tube S5. The duty cycle D of the secondary side fifth switch tube S5 is adjusted by a closed-loop control system, and the switching frequency is always higher than the series resonant frequency. Figure 5 At the middle stable moment, the switching frequency of the fifth switch tube S5 and the sixth switch tube S6 on the secondary side is greater than the series resonant frequency; the driving pulse duty ratio of the fifth switch tube S5 and the eighth switch tube S8 on the secondary side of the secondary full-bridge rectifier circuit V is D (ignoring the dead time); the driving pulse duty ratio of the sixth switch tube S6 and the seventh switch tube S7 on the secondary side of the secondary full-bridge rectifier circuit V is 1-D (ignoring the dead time);

[0073] like Figure 5 As shown, the current flowing through the resonant inductor L r The resonant current i Lr There is no primary loop circulation process, which significantly reduces Figure 2The circulating current loss caused by the circulating current is beneficial to improving the conversion efficiency of the resonant converter; at the same time, the secondary side switch tube adopts APWM control, which avoids the increase of gate drive loss caused by excessively high switching tube frequency under light no-load, and improves the light no-load efficiency.

[0074] As a preferred embodiment of this embodiment, in this embodiment, controlling the duty cycle D according to the control signal to adjust the output voltage gain of the resonant converter specifically includes:

[0075] comparing the control signal with a preset first reference value;

[0076] When the control signal is lower than the first reference value (reference value 1 in the figure), the duty cycle D of the fifth switch tube S5 on the secondary side is controlled to remain unchanged, and the internal phase shift angle of the switch tube of the primary inverter switch circuit II is adjusted according to the control signal, wherein the internal phase shift angle increases as the control signal decreases, and the output voltage gain decreases as the internal phase shift angle increases;

[0077] When the control signal is higher than the first reference value, the internal phase shift angle of the switch tube of the primary inverter switch circuit II is controlled to remain fixed, and the duty cycle D of the secondary fifth switch tube S5 is adjusted according to the control signal, wherein the duty cycle D increases with the increase of the control signal, and the output voltage gain increases with the increase of the duty cycle D.

[0078] Specifically, Figure 6 Shown Figure 1 The schematic diagram of mode switching based on the circuit topology shown in the figure adopts the internal phase shift control of the primary switch tube and the APWM control of the secondary switch tube, that is, adjusting the internal phase shift angle of the primary switch tube and the duty cycle of the secondary switch tube, among which the internal phase shift angle of the primary switch tube ( Figure 6 The θ) in the figure refers to the phase angle difference between the rising edges of the driving pulses of the first switch tube S1 on the primary side and the fourth switch tube S4 on the primary side. In this embodiment, there are two control variables: the output electrical parameters of the converter are sampled, and the error control is performed with the reference electrical parameters to generate a control signal. The larger the output electrical parameter value, the smaller the control signal. When the control signal is lower than the first reference value, the duty cycle of the fifth switch tube S5 on the secondary side is fixed, the internal phase shift angle of the primary switch tube increases as the control signal decreases, and the converter gain decreases; when the control signal is higher than the first reference value, the internal phase shift angle of the primary switch tube is fixed, the duty cycle of the fifth switch tube S5 on the secondary side increases as the control signal increases, and the converter gain increases.

[0079] As a preferred embodiment of this embodiment, in this embodiment, controlling the duty cycle D according to the control signal to adjust the output voltage gain of the resonant converter specifically includes:

[0080] Comparing the control signal with a preset second reference value (reference value 2 in the figure);

[0081] When the control signal is lower than the second reference value, the external phase shift angle between the switch tube of the primary inverter switch circuit II and the switch tube of the secondary rectifier circuit V is controlled to remain unchanged, and the duty cycle D of the fifth switch tube S5 of the secondary side is adjusted according to the control signal, wherein the duty cycle D increases with the increase of the control signal, and the output voltage gain increases with the increase of the duty cycle;

[0082] When the control signal is higher than the second reference value, the duty cycle D of the fifth switch tube S5 on the secondary side is controlled to remain unchanged, and the external phase shift angle between the switch tube of the primary inverter switch circuit II and the switch tube of the secondary rectifier circuit V is adjusted according to the control signal, wherein the external phase shift angle increases with the increase of the control signal, and the output voltage gain increases with the increase of the external phase shift angle.

[0083] Specifically, Figure 7 Shown Figure 1 The schematic diagram of mode switching of the primary and secondary switch tube external phase shift control and the secondary switch tube APWM control based on the circuit topology shown in the figure, that is, adjusting the external phase shift angle of the primary and secondary switch tube and the duty cycle of the secondary switch tube, wherein the external phase shift angle of the primary and secondary switch tube ( Figure 7 θ1) in the figure refers to the phase angle difference between the rising edge of the driving pulse of the first switch tube S1 on the primary side and the fifth switch tube S5 on the secondary side. In this embodiment, there are two control variables: the output electrical parameters of the converter are sampled, and the error control is performed with the reference electrical parameters to generate a control signal. The larger the output electrical parameter value, the smaller the control signal. When the control signal is lower than the second reference value, the outward phase angle of the primary and secondary switch tubes is fixed, and the duty cycle of the fifth switch tube S5 on the secondary side increases with the increase of the control signal, and the converter gain is improved; when the control signal is higher than the second reference value, the duty cycle of the fifth switch tube S5 on the secondary side is fixed, and the outward phase angle of the primary and secondary switch tubes increases with the increase of the control signal, and the converter gain is improved.

[0084] As a preferred embodiment of this embodiment, in this embodiment, controlling the duty cycle D according to the control signal to adjust the output voltage gain of the resonant converter specifically includes:

[0085] Comparing the control signal with a preset first reference value and a second reference value, wherein the first reference value is smaller than the second reference value;

[0086] When the control signal is lower than the first reference value, the external phase shift angle between the switch tube of the primary inverter switch circuit II and the switch tube of the secondary rectifier circuit V and the duty cycle D of the secondary fifth switch tube S5 are controlled to remain unchanged, and the switching frequency of the switch tube of the primary inverter switch circuit II is adjusted according to the control signal, wherein the switching frequency decreases as the control signal increases, and the output voltage gain increases as the switching frequency decreases;

[0087] When the control signal is higher than the first reference value and lower than the second reference value, the external phase shift angle between the switch tube of the primary inverter switch circuit II and the switch tube of the secondary rectifier circuit V and the switching frequency of the switch tube of the primary inverter switch circuit II are controlled to remain unchanged, and the duty cycle D of the secondary fifth switch tube S5 is adjusted according to the control signal, wherein the duty cycle D increases with the increase of the control signal, and the output voltage gain increases with the increase of the duty cycle D;

[0088] When the control signal is higher than the second reference value, the switching frequency of the switch tube of the primary inverter switch circuit II and the duty cycle D of the secondary fifth switch tube S5 are controlled to remain unchanged, and the external phase shift angle between the switch tube of the primary inverter switch circuit II and the switch tube of the secondary rectifier circuit V is adjusted according to the control signal, wherein the external phase shift angle increases with the increase of the control signal, and the output voltage gain increases with the increase of the external phase shift angle.

[0089] Specifically, Figure 8 Shown Figure 1 The circuit topology shown in the figure adopts the mode switching diagram of primary switch tube pulse frequency modulation, primary switch tube internal phase shift control, and secondary switch tube APWM control. The output electrical parameters of the converter are sampled, and the error is controlled with the reference electrical parameters to generate a control signal. The larger the output electrical parameter value, the smaller the control signal. When the control signal is lower than the first reference value, the primary and secondary switch tube external phase shift angle ( Figure 8 θ2 in the figure), the duty cycle of the fifth switch tube S5 on the secondary side is fixed, and the pulse frequency of the primary switch tube (also called the switching frequency, ( Figure 8 f)) in the figure decreases as the control signal increases, and the converter gain increases; when the control signal is higher than the first reference value and lower than the second reference value, the pulse frequency of the primary switch tube and the external phase angle of the primary and secondary switch tubes are fixed, and the duty cycle of the secondary fifth switch tube S5 increases as the control signal increases, and the converter gain increases; when the control signal is higher than the second reference value, the pulse frequency of the primary switch tube and the duty cycle of the secondary fifth switch tube S5 are fixed, and the external phase angle of the primary and secondary switch tubes increases as the control signal increases, and the converter gain increases.

[0090] As a preferred embodiment of this embodiment, in this embodiment, controlling the duty cycle D according to the control signal to adjust the output voltage gain of the resonant converter specifically includes:

[0091] Comparing the control signal with a preset first reference value and a second reference value, wherein the first reference value is smaller than the second reference value;

[0092] When the control signal is lower than the first reference value, the switching frequency of the switch tube of the primary inverter switch circuit II and the duty cycle D of the secondary fifth switch tube S5 are controlled to remain unchanged, and the internal phase shift angle of the switch tube of the primary inverter switch circuit (II) is adjusted according to the control signal, wherein the internal phase shift angle decreases as the control signal increases, and the output voltage gain increases as the internal phase shift angle decreases;

[0093] When the control signal is higher than the first reference value and lower than the second reference value, the internal phase shift angle of the switch tube of the primary inverter switch circuit II and the duty cycle D of the secondary fifth switch tube S5 are controlled to remain unchanged, and the switching frequency of the switch tube of the primary inverter switch circuit II is adjusted according to the control signal, wherein the switching frequency decreases as the control signal increases, and the output voltage gain increases as the switching frequency decreases;

[0094] When the control signal is higher than the second reference value, the switching frequency of the switch tube of the primary inverter switch circuit II and the internal phase shift angle of the switch tube of the primary inverter switch circuit II are controlled to remain unchanged, and the duty cycle D of the secondary side fifth switch tube S5 is adjusted according to the control signal, wherein the duty cycle D increases with the increase of the control signal, and the output voltage gain increases with the increase of the duty cycle D.

[0095] Fig. 9 Shown Figure 1 The circuit topology shown in the figure adopts the mode switching diagram of the primary switch tube internal phase shift control, the primary switch tube pulse frequency modulation, and the secondary switch tube APWM control. The output electrical parameters of the converter are sampled, and the error is controlled with the reference electrical parameters to generate a control signal. The larger the output electrical parameter value, the smaller the control signal. When the control signal is lower than the first reference value, the primary switch tube pulse frequency ( Fig. 9 f), the secondary duty cycle is fixed, the primary switch tube phase shift angle ( Fig. 9 θ3) in the control signal increases as the control signal decreases, and the converter gain decreases; when the control signal is higher than the first reference value and lower than the second reference value, the duty cycle of the fifth switch tube S5 on the secondary side and the phase shift angle in the primary switch tube are fixed, the pulse frequency of the primary switch tube decreases as the control signal increases, and the converter gain increases; when the control signal is higher than the second reference value, the pulse frequency of the primary switch tube and the phase shift angle in the primary switch tube are fixed, the duty cycle of the fifth switch tube S5 on the secondary side increases as the control signal increases, and the converter gain increases.

[0096] As a preferred embodiment of this embodiment, in this embodiment, controlling the duty cycle D according to the control signal to adjust the output voltage gain of the resonant converter specifically includes:

[0097] comparing the control signal with a preset first reference value;

[0098] When the control signal is lower than the first reference value, the duty cycle D of the fifth switch tube S5 on the secondary side is controlled to remain unchanged, and the duty cycle of the switch tube of the primary inverter switch circuit II is adjusted according to the control signal, wherein the duty cycle of the switch tube of the primary inverter switch circuit II decreases as the control signal decreases, and the output voltage gain decreases as the duty cycle of the switch tube of the primary inverter switch circuit II decreases;

[0099] When the control signal is higher than the first reference value, the duty cycle of the switch tube of the primary inverter switch circuit II is controlled to remain fixed, and the duty cycle D of the secondary fifth switch tube S5 is adjusted according to the control signal, wherein the duty cycle D of the secondary fifth switch tube S5 increases with the increase of the control signal, and the output voltage gain increases with the increase of the duty cycle D of the secondary fifth switch tube S5.

[0100] Specifically, Fig.10 Shown Figure 1 The schematic diagram of mode switching based on the circuit topology shown adopts pulse width modulation PWM of the primary switch tube and APWM control of the secondary switch tube. The output electrical parameters of the converter are sampled, and the error control is performed with the reference electrical parameters to generate a control signal. The larger the output electrical parameter value, the smaller the control signal. When the control signal is lower than the first reference value, the duty cycle D of the fifth switch tube S5 on the secondary side is fixed, the duty cycle of the primary switch tube decreases as the control signal decreases, and the converter gain decreases; when the control signal is higher than the first reference value, the duty cycle D0 of the primary switch tube is fixed, the duty cycle D of the fifth switch tube S5 on the secondary side increases as the control signal increases, and the converter gain increases.

[0101] Specifically, Fig.11 Shown Figure 1 The schematic diagram of mode switching using APWM control of the primary switch tube and APWM control of the secondary switch tube based on the circuit topology shown. The output electrical parameters of the converter are sampled, and error control is performed with the reference electrical parameters to generate a control signal. The larger the output electrical parameter value, the smaller the control signal. When the control signal is lower than the first reference value, the secondary duty cycle is fixed, the primary switch tube duty cycle decreases as the control signal decreases, and the converter gain decreases; when the control signal is higher than the first reference value, the primary switch tube duty cycle D1 is fixed, and the duty cycle D of the fifth secondary switch tube S5 increases as the control signal increases, and the converter gain increases.

[0102] In the description of the above embodiment, due to the use of the secondary side APWM control method, the resonant converter only operates within a frequency range higher than the series resonant frequency, which significantly reduces the frequency adjustment range of the traditional frequency conversion control, is conducive to the optimization design of the magnetic components of the resonant converter, reduces the volume of the transformer, and improves the power density. Compared with the disclosed PFM control technology, the control method described in this embodiment significantly reduces the circulating current appearing on the primary side of the transformer in the PFM control, thereby reducing the circulating current loss on the primary side, which is conducive to improving the conversion efficiency. The control method described in this embodiment enables the resonant converter to have a wider gain adjustment capability, so that the resonant converter has more application advantages in wide voltage applications, and improves the efficiency and power density of the resonant converter.

[0103] The description of the above embodiments is only used to help understand the inventive concept of the present application and is not intended to limit the present invention. For ordinary technicians in this technical field, any modifications, equivalent substitutions, improvements, etc. made without departing from the principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A control method for a wide-gain LLC resonant converter, the resonant converter comprising a DC input source V in (I), primary inverter switch circuit (II), resonant cavity (III), transformer (IV), secondary rectifier circuit (V) and filter output circuit (VI); characterized in that: The secondary rectifier circuit (V) includes a fifth secondary switch tube S5, a sixth secondary switch tube S6, a seventh power device and an eighth power device. The driving pulses of the fifth secondary switch tube S5 and the sixth secondary switch tube S6 are complementary to each other. The duty cycle of the fifth secondary switch tube S5 is D, and the duty cycle of the sixth secondary switch tube S6 is 1-D. The switching frequencies of all the switches of the secondary rectifier circuit (V) are higher than the series resonant frequency. The control method includes: Sampling the output electrical parameters of the resonant converter, and performing error processing on the collected output electrical parameters and reference electrical parameters to obtain error parameters; A control signal is generated according to the error parameter, and a duty cycle D is controlled according to the control signal to adjust the output voltage gain of the resonant converter, wherein the control signal decreases as the output electrical parameter increases.

2. The control method of the wide gain LLC resonant converter according to claim 1, characterized in that: Controlling the duty cycle D according to the control signal to adjust the output voltage gain of the resonant converter specifically includes: comparing the control signal with a preset first reference value; When the control signal is lower than the first reference value, the duty cycle D of the fifth switch tube S5 on the secondary side is controlled to remain unchanged, and the internal phase shift angle of the switch tube of the primary inverter switch circuit (II) is adjusted according to the control signal, wherein the internal phase shift angle increases as the control signal decreases, and the output voltage gain decreases as the internal phase shift angle increases; When the control signal is higher than the first reference value, the internal phase shift angle of the switch tube of the primary inverter switch circuit (II) is controlled to remain fixed, and the duty cycle D of the secondary fifth switch tube S5 is adjusted according to the control signal, wherein the duty cycle D increases with the increase of the control signal, and the output voltage gain increases with the increase of the duty cycle D.

3. The control method of a wide-gain LLC resonant converter according to any one of claims 1 or 2, characterized in that: Controlling the duty cycle D according to the control signal to adjust the output voltage gain of the resonant converter specifically includes: Comparing the control signal with a preset first reference value and a second reference value, wherein the first reference value is smaller than the second reference value; When the control signal is lower than the first reference value, the switching frequency of the switch tube of the primary inverter switch circuit (II) and the duty cycle D of the fifth switch tube S5 of the secondary side are controlled to remain unchanged, and the internal phase shift angle of the switch tube of the primary inverter switch circuit (II) is adjusted according to the control signal, wherein the internal phase shift angle decreases as the control signal increases, and the output voltage gain increases as the internal phase shift angle decreases; When the control signal is higher than the first reference value and lower than the second reference value, the internal phase shift angle of the switch tube of the primary inverter switch circuit (II) and the duty cycle D of the secondary fifth switch tube S5 are controlled to remain unchanged, and the switching frequency of the switch tube of the primary inverter switch circuit (II) is adjusted according to the control signal, wherein the switching frequency decreases as the control signal increases, and the output voltage gain increases as the switching frequency decreases; When the control signal is higher than the second reference value, the switching frequency of the switch tube of the primary inverter switch circuit (II) and the internal phase shift angle of the switch tube of the primary inverter switch circuit (II) are controlled to remain unchanged, and the duty cycle D of the secondary side fifth switch tube S5 is adjusted according to the control signal, wherein the duty cycle D increases with the increase of the control signal, and the output voltage gain increases with the increase of the duty cycle D.

4. The control method of the wide gain LLC resonant converter according to claim 1, characterized in that: Controlling the duty cycle D according to the control signal to adjust the output voltage gain of the resonant converter specifically includes: comparing the control signal with a preset second reference value; When the control signal is lower than the second reference value, the external phase shift angle between the switch tube of the primary inverter switch circuit (II) and the switch tube of the secondary rectifier circuit (V) is controlled to remain unchanged, and the duty cycle D of the fifth switch tube S5 of the secondary side is adjusted according to the control signal, wherein the duty cycle D increases with the increase of the control signal, and the output voltage gain increases with the increase of the duty cycle; When the control signal is higher than the second reference value, the duty cycle D of the fifth switch tube S5 on the secondary side is controlled to remain unchanged, and the external phase shift angle between the switch tube of the primary inverter switch circuit (II) and the switch tube of the secondary rectifier circuit (V) is adjusted according to the control signal, wherein the external phase shift angle increases with the increase of the control signal, and the output voltage gain increases with the increase of the external phase shift angle.

5. The control method of a wide-gain LLC resonant converter according to any one of claims 1 or 4, characterized in that: Controlling the duty cycle D according to the control signal to adjust the output voltage gain of the resonant converter specifically includes: Comparing the control signal with a preset first reference value and a second reference value, wherein the first reference value is smaller than the second reference value; When the control signal is lower than the first reference value, the external phase shift angle between the switch tube of the primary inverter switch circuit (II) and the switch tube of the secondary rectifier circuit (V) and the duty cycle D of the secondary fifth switch tube S5 are controlled to remain unchanged, and the switching frequency of the switch tube of the primary inverter switch circuit (II) is adjusted according to the control signal, wherein the switching frequency decreases as the control signal increases, and the output voltage gain increases as the switching frequency decreases; When the control signal is higher than the first reference value and lower than the second reference value, the external phase shift angle between the switch tube of the primary inverter switch circuit (II) and the switch tube of the secondary rectifier circuit (V) and the switching frequency of the switch tube of the primary inverter switch circuit (II) are controlled to remain unchanged, and the duty cycle D of the secondary fifth switch tube S5 is adjusted according to the control signal, wherein the duty cycle D increases with the increase of the control signal, and the output voltage gain increases with the increase of the duty cycle D; When the control signal is higher than the second reference value, the switching frequency of the switch tube of the primary inverter switch circuit (II) and the duty cycle D of the secondary fifth switch tube S5 are controlled to remain unchanged, and the external phase shift angle between the switch tube of the primary inverter switch circuit (II) and the switch tube of the secondary rectifier circuit (V) is adjusted according to the control signal, wherein the external phase shift angle increases with the increase of the control signal, and the output voltage gain increases with the increase of the external phase shift angle.

6. The control method of the wide-gain LLC resonant converter according to claim 1, characterized in that: Controlling the duty cycle D according to the control signal to adjust the output voltage gain of the resonant converter specifically includes: comparing the control signal with a preset first reference value; When the control signal is lower than the first reference value, the duty cycle D of the fifth switch tube S5 on the secondary side is controlled to remain unchanged, and the duty cycle of the switch tube of the primary inverter switch circuit (II) is adjusted according to the control signal, wherein the duty cycle of the switch tube of the primary inverter switch circuit (II) decreases as the control signal decreases, and the output voltage gain decreases as the duty cycle of the switch tube of the primary inverter switch circuit (II) decreases; When the control signal is higher than the first reference value, the duty cycle of the switch tube of the primary inverter switch circuit (II) is controlled to remain fixed, and the duty cycle D of the secondary fifth switch tube S5 is adjusted according to the control signal, wherein the duty cycle D of the secondary fifth switch tube S5 increases with the increase of the control signal, and the output voltage gain increases with the increase of the duty cycle D of the secondary fifth switch tube S5.

7. The control method of the wide-gain LLC resonant converter according to claim 1, characterized in that: The output electrical parameter is output voltage, output current or output power.

8. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 7 are implemented.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

Images