LLC resonant converter and control method thereof

Abstract

The present invention discloses an LLC resonant converter and a control method thereof, which belongs to the field of electric energy conversion technology, and includes a capacitor module, a primary side conversion module, a charging module, a voltage conversion module and a secondary side conversion module, wherein the capacitor module, the primary side conversion module, the voltage conversion module and the secondary side conversion module are connected in sequence, and the charging module is connected between the capacitor module and the primary side conversion module. The LLC resonant converter of the present invention reduces the volume while ensuring a wide voltage gain range and improving the full range working efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of electric energy conversion, and in particular to an LLC resonant converter and a control method thereof. Background Art

[0002] Energy is the core driving force for production, development and progress in contemporary society. However, with the increasing prominence of environmental and resource issues, traditional fossil energy represented by coal and oil is gradually being replaced by new energy sources such as wind energy, solar energy and natural gas hydrates. In the application scenarios of new energy power generation and electricity consumption, such as photovoltaic power generation, electric vehicle charging, and power supply for on-board electrical equipment, higher requirements are placed on the gain range of DC / DC converters. At the same time, improving the working efficiency of the converter in the full range is of great significance to improving equipment performance and reducing power loss.

[0003] LLC resonant converter is widely used in the fields of renewable energy generation due to its simple structure, small number of components, zero voltage switch (ZVS) for primary switch tube, zero current switch (ZCS) for rectifier diode, high overall efficiency, low electromagnetic interference, magnetic integration technology can be used to improve power density, and frequency modulation control. However, the gain range of traditional LLC resonant converter is limited and greatly affected by load. The switching frequency varies greatly when adjusted over a wide range, which not only increases the difficulty of magnetic component design, but also causes the converter efficiency to drop rapidly when the switching frequency is far away from the resonant frequency. Therefore, broadening the gain range of LLC resonant converter and improving its full-range working efficiency are of great significance to improving equipment performance and reducing power loss. Summary of the invention

[0004] The present invention aims to provide an LLC resonant converter and a control method thereof.

[0005] To achieve the above object, the technical solution of the present invention is: An LLC resonant converter comprises a capacitor module, a primary conversion module, a charging module, a voltage transformation module and a secondary conversion module, wherein the capacitor module, the primary conversion module, the voltage transformation module and the secondary conversion module are connected in sequence, and the charging module is connected between the capacitor module and the primary conversion module.

[0006] In a specific embodiment, the capacitor module includes a first capacitor and a second capacitor, and the first capacitor and the second capacitor are connected in series.

[0007] In a specific embodiment, the primary side conversion module includes a first primary side bridge arm, a second primary side bridge arm, and a third primary side bridge arm. The two ends of the first primary side bridge arm, the two ends of the second primary side bridge arm, and the two ends of the third primary side bridge arm are connected in parallel, and the two ends after parallel connection are connected in parallel with the two ends of the capacitor module.

[0008] In a specific embodiment, the charging module includes a first inductor and a third capacitor, one end of the first inductor and the third capacitor connected in series is connected to the midpoint of the series connection of the first capacitor and the second capacitor, and the other end is connected to the midpoint of the bridge arm of the second primary bridge arm.

[0009] In a specific embodiment, the transformer module includes a first transformer and a second transformer, the first end of the primary winding of the first transformer is connected to the midpoint of the third primary bridge arm, the second end of the primary winding of the first transformer is connected to the midpoint of the second primary bridge arm, the first end of the primary winding of the second transformer is connected to the midpoint of the first primary bridge arm, and the second end of the primary winding of the second transformer is connected to the midpoint of the second primary bridge arm.

[0010] In a specific embodiment, the secondary side conversion module includes a first secondary side bridge arm, a second secondary side bridge arm, and a third secondary side bridge arm, and the two ends of the first secondary side bridge arm, the two ends of the second secondary side bridge arm, and the two ends of the third secondary side bridge arm are connected in parallel; the first end of the secondary winding of the first transformer is connected to the midpoint of the first secondary side bridge arm, the second end of the secondary winding of the first transformer is connected to the first end of the secondary winding of the second transformer and the midpoint of the second secondary side bridge arm, and the second end of the secondary winding of the second transformer is connected to the midpoint of the third secondary side bridge arm.

[0011] In a specific embodiment, the first primary bridge arm includes a first switch and a second switch, and the first switch is connected in series with the second switch; the second primary bridge arm includes a fifth switch and a sixth switch, and the fifth switch is connected in series with the sixth switch; the third primary bridge arm includes a third switch and a fourth switch, and the third switch is connected in series with the fourth switch.

[0012] In a specific embodiment, the first secondary bridge arm, the second secondary bridge arm, and the third secondary bridge arm each include two switches connected in series.

[0013] The present invention also provides a control method for an LLC resonant converter, which is applied to the above-mentioned LLC resonant converter, including controlling the LLC resonant converter to operate in a single-module low-gain mode or a single-module high-gain mode or a dual-module low-gain mode or a dual-module high-gain mode.

[0014] When the LLC resonant converter operates in a single-module low-gain mode, the output voltage is regulated by changing the operating frequency of the LLC resonant converter, and the third switch and the fourth switch of the third primary bridge arm are controlled to be alternately turned on.

[0015] When the LLC resonant converter operates in a single-module high-gain mode, the switching frequency of the LLC resonant converter remains unchanged, and the output voltage is adjusted by changing the duty cycle of the fifth switch and the sixth switch of the second primary bridge arm; in each first half of the switching cycle, the fifth switch of the second primary bridge arm is controlled to be turned on first, and then the fifth switch is controlled to be turned off and the third switch is turned on; in each second half of the switching cycle, the sixth switch of the second primary bridge arm is controlled to be turned on first, and then the sixth switch is controlled to be turned off and the fourth switch is turned on.

[0016] When the LLC resonant converter operates in the dual-module low-gain mode, the output voltage is adjusted by changing the operating frequency of the LLC resonant converter, and the third switch and the fourth switch are controlled to be turned on alternately, the first switch and the third switch are turned on at the same time, and the second switch and the fourth switch are turned on at the same time.

[0017] When the LLC resonant converter operates in the dual-module high-gain mode, the switching frequency of the LLC resonant converter remains unchanged, and the output voltage is adjusted by changing the duty cycle of the fifth switch and the sixth switch of the second primary bridge arm; in each first half of the switching cycle, the fifth switch of the second primary bridge arm is controlled to be turned on first, and then the fifth switch is controlled to be turned off, and the first switch and the third switch are turned on; in each second half of the switching cycle, the sixth switch of the second primary bridge arm is controlled to be turned on first, and then the sixth switch is controlled to be turned off, and the second switch and the fourth switch are turned on.

[0018] Beneficial effect: The LLC resonant converter and control method of the present invention save a resonant inductor and a resonant capacitor by integrating the resonant cavity, which greatly reduces the circuit cost and volume. At the same time, a wide gain range can be achieved, which is more suitable for various occasions such as current new energy electricity consumption and power generation. In addition, since the switching frequency range of the LLC resonant converter of the present invention is very narrow and the soft switch is basically fully realized, the working efficiency of the whole range can be improved. Moreover, by adjusting the primary-secondary turns ratio of the transformer, a boost or buck function can be obtained, and at the same time, the secondary side of the transformer does not need a center tap structure, and the structure is simple.

[0019] In order to make the above features and advantages of the invention more obvious and easy to understand, embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The figure is a circuit diagram of an LLC resonant converter according to the present invention.

[0021] Figure 2 This is an equivalent circuit diagram of the LLC resonant converter of the present invention operating in a single-module low-gain mode.

[0022] Figure 3 This is a working waveform diagram of the LLC resonant converter of the present invention working in a single-module low-gain mode.

[0023] Figure 4 This is an equivalent circuit diagram of the LLC resonant converter of the present invention operating in a single-module high-gain mode.

[0024] Figure 5 This is a working waveform diagram of the LLC resonant converter of the present invention working in a single-module high-gain mode.

[0025] Figure 6 It is an equivalent circuit diagram of the LLC resonant converter of the present invention working in the dual-module low-gain mode.

[0026] Figure 7 This is an equivalent circuit diagram of the LLC resonant converter of the present invention operating in a dual-module high-gain mode.

[0027] Figure 8 (a) is the steady-state waveform of the output voltage of 90V in the low-gain mode of a single module. Figure 8 (b) is the steady-state waveform of the output voltage of 100V in the high-gain mode of a single module. Figure 8 (c) is the steady-state waveform of the output voltage of 180V in the single module high gain mode. Figure 8 (d) is the steady-state waveform of the dual-module low-gain mode when the output voltage is 180V. Figure 8 (e) is the steady-state waveform of the dual-module high-gain mode when the output voltage is 200V. Figure 8 (f) in the figure is the steady-state waveform diagram when the output voltage is 360V in the dual-module high-gain mode. DETAILED DESCRIPTION

[0028] In order to make the purpose and technical solution of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] Figure 1 FIG. 1 is a circuit diagram of an LLC resonant converter according to the present invention. Figure 1As shown, the LLC resonant converter of the present invention includes a capacitor module 1, a primary side conversion module 2, a charging module 3, a voltage transformation module 4 and a secondary side conversion module 5, and an input voltage V in , the capacitor module 1, the primary side conversion module 2, the voltage transformation module 4, the secondary side conversion module 5, the output voltage V o The charging module 3 is connected in sequence between the capacitor module 1 and the primary side conversion module 2 .

[0030] Furthermore, the capacitor module 1 includes a capacitor C 1 With capacitor C 2 , the capacitor C 1 With the capacitor C 2 The two ends of the series connection are connected to the input voltage V in in parallel.

[0031] Furthermore, the primary side conversion module 2 includes a first primary side bridge arm 21, a second primary side bridge arm 22, and a third primary side bridge arm 23. The two ends of the first primary side bridge arm 21, the two ends of the second primary side bridge arm 22, and the two ends of the third primary side bridge arm 23 are connected in parallel, and the two ends after parallel connection are connected in parallel with the two ends of the capacitor module 1.

[0032] More specifically, the first primary bridge arm 21 includes a switch Q 1 With switch Q 2 , the switch Q 1 With the switch Q 2 The middle point of the series connection is the middle point of the bridge arm of the first primary bridge arm 21; the second primary bridge arm 22 includes a switch Q 5 With switch Q 6 , the switch Q 5 With the switch Q 6 The third primary bridge arm 23 includes a switch Q 3 With switch Q 4 , the switch Q 3 With the switch Q 4 The series connection is carried out, and the series connection midpoint is the bridge arm midpoint of the third primary bridge arm 23. The second primary bridge arm 22 is an auxiliary bridge arm.

[0033] In a specific embodiment, the switch Q 1 , the switch Q 2 , the switch Q 3 , the switch Q 4 , the switch Q 5 , the switch Q 6 For MOSFET.

[0034] Optionally, the switch Q1 , the switch Q 2 , the switch Q 3 , the switch Q 4 , the switch Q 5 , the switch Q 6 Other switch devices may also be used, and the present invention is not limited thereto.

[0035] Furthermore, the transformer module 4 includes a transformer T 1 With transformer T 2 , the transformer T 1 The first end of the primary winding is connected to the midpoint of the third primary bridge arm 23, and the transformer T 1 The second end of the primary winding is connected to the midpoint of the second primary bridge arm 22, and the transformer T 2 The first end of the primary winding is connected to the midpoint of the first primary bridge arm 21, and the transformer T 2 The second end of the primary winding is connected to the midpoint of the bridge arm of the second primary bridge arm 22. L m1 For transformer T 1 The magnetizing inductance, L m2 For transformer T 2 The magnetizing inductance.

[0036] Furthermore, the secondary side conversion module 5 includes a first secondary side bridge arm 51, a second secondary side bridge arm 52, and a third secondary side bridge arm 53. The two ends of the first secondary side bridge arm 51, the two ends of the second secondary side bridge arm 52, and the two ends of the third secondary side bridge arm 53 are connected in parallel, and the two ends after parallel connection are connected to the output voltage V o in parallel.

[0037] More specifically, the first secondary bridge arm 51 includes a switch D 1 , switch D 2 , the switch D 1 With the switch D 2 The middle point of the series connection is the middle point of the bridge arm of the first secondary side bridge arm 51; the second secondary side bridge arm 52 includes a switch D 3 , switch D 4 , the switch D 3 With the switch D 4 The third secondary bridge arm 53 includes a switch D 5 , switch D 6 , the switch D 5 With the switch D 6 The series connection is carried out, and the series connection midpoint is the bridge arm midpoint of the third secondary bridge arm 53 .

[0038] In a specific embodiment, the switch D 1 , the switch D 2 , the switch D 3 , the switch D 4 , the switch D 5 , the switch D 6 For the diode.

[0039] Optionally, the switch D 1 , the switch D 2 , the switch D 3 , the switch D 4 , the switch D 5 , the switch D 6 Other switch devices may also be used, and the present invention is not limited thereto.

[0040] Among them, the transformer T 1 The first end of the secondary winding of the transformer is connected to the midpoint of the bridge arm of the first secondary bridge arm 51. 1 The second end of the secondary winding is connected to the transformer T 2 The transformer T 2 The second end of the secondary winding is connected to the bridge arm midpoint of the third secondary bridge arm 53.

[0041] Furthermore, the charging module 3 includes an inductor L r With capacitor C r , the inductance L r With the capacitor C r One end of the series connection is connected to the capacitor C 1 With the capacitor C 2 The other end is connected to the midpoint of the bridge arm of the second primary bridge arm 22.

[0042] Optionally, two ends of the first secondary bridge arm 51, the second secondary bridge arm 52, and the third secondary bridge arm 53 connected in parallel are further connected to a resistor R L In parallel, the resistor R L The voltage across the two ends is the output voltage V o , resistor R L For load.

[0043] Optionally, the LLC resonant converter of the present invention further includes a capacitor C o , the capacitor C o With the output voltage V o In parallel, the capacitor C o It plays the role of output filtering.

[0044] Optionally, the input voltage Vin This includes stable DC bus voltage in the power supply system, DC power with a wide range of variations, etc., depending on the application.

[0045] Next, the functions of an LLC resonant converter of the present invention are described. The primary conversion module 2 plays the role of inversion, converting the input voltage V in Inverted into alternating current; the transformer module 4 includes two transformers, that is, two matching resonant cavities. In this application, the resonant inductance and resonant capacitance of the two resonant cavities are shared to obtain an integrated resonant inductance and resonant capacitance, that is, the inductance L r With capacitor C r , inductance L r With capacitor C r After being connected in series, they are connected between the series midpoint of the capacitor and the midpoint of the bridge arm of the second primary side to form a charging module. In order to ensure that the resonant frequency of the two resonant cavities after integration remains unchanged when working alone or simultaneously, the parameters of the two resonant cavities before integration are: C r1 = C r2 , L r1 = L r2 When , the integrated resonant cavity parameters are C r = C r1 / 2= C r2 / 2, L r =2 L r1 =2 L r2 ,in, C r1 is the resonant capacitance of the first resonant cavity before integration, C r2 is the resonant capacitance of the second resonant cavity before integration, L r1 is the resonant inductance of the first resonant cavity before integration, L r2 is the resonant inductor of the second resonant cavity before integration. In addition, the secondary side of the transformer module 4 does not need a center tap structure. 1 、Transformer T 2 The turns ratio is n :1. The two full-bridge rectifier structures share a set of bridge arms to form a three-bridge rectifier structure in the secondary conversion module 5 of the present application, and provide an output voltage V after rectifying the voltage converted by the transformer module 4. oBased on the rectifier of this structure, an LLC resonant converter of the present invention can work with a single resonant cavity or with two resonant cavities working simultaneously, thereby achieving a widened gain range.

[0046] The following is an introduction to a control method of an LLC resonant converter according to the present invention.

[0047] The present invention provides a control method for an LLC resonant converter, comprising: controlling the LLC resonant converter to operate in a single-module low-gain (SMLG) mode, a single-module high-gain (SMHG) mode, a dual-module low-gain (DMLG) mode, or a dual-module high-gain (DMHG) mode.

[0048] Please refer to Figure 2 When the LLC resonant converter operates in a single-module low-gain mode, the output voltage V is achieved by changing the operating frequency of the LLC resonant converter. o In this mode, the switch Q of the first primary bridge arm 21 is 1 With switch Q 2 , the switch Q of the second primary bridge arm 22 5 With switch Q 6 、Transformer T 2 , the third secondary bridge arm 53 does not participate in the work, and controls the switch Q of the third primary bridge arm 23 3 With switch Q 4 Alternate conduction. The working waveform is as follows Figure 3 As shown, Q g3 Q is the switch 3 The driving waveform, Q g4 Q is the switch 4 The driving waveform, i Lr is the resonant inductor current, i Q5 is the current flowing through the switch Q 5 The current, i Q6 is the current flowing through the switch Q 6 The current, v Cr is the capacitance C r The voltage across the two ends, t is the time, T s For each cycle duration, D R is the duty cycle in the resonance stage, D d is the duty cycle of the dead time. In the first stage [ t0 , t 1 ] and the second stage [ t 1 , t 2 ], switch Q 3 Turn on, switch Q 4 Shutdown; In the third stage [ t 2 , t 3 ], switch Q 3 With switch Q 4 All turned off.

[0049] The working principle of the LLC resonant converter in the single-module low-gain mode of the present invention is similar to that of the conventional half-bridge LLC resonant converter using frequency modulation control, except that the third stage [ t 2 , t 3 ].exist t 2 Moment, switch Q 3 Turn off, resonant inductor current i Lr Keep the original direction of flow, that is, switch Q 6 With switch Q 4 The junction capacitance is discharged. When the discharge is completed, the resonant current flows through the switch Q 6 The resonant inductor current is i Lr Nonlinear decrease, at the same time this stage is the switch Q 4 It provides the conditions for zero voltage switching. Please refer to Figure 4 When the LLC resonant converter operates in the single-module high-gain mode, the switching frequency of the LLC resonant converter remains unchanged. By changing the switch Q of the second primary bridge arm 22 5 , switch Q 6 The duty cycle of the output voltage V o In this mode, the switch Q of the first primary bridge arm 21 1 With switch Q 2 、Transformer T 2 , the third secondary bridge arm 53 does not participate in the work. In each first half of the switching cycle, the upper switch of the second primary bridge arm 22, i.e., switch Q 5 First, the conduction time is 0.5 T s D L , at this time, all other switches are turned off, and the input voltage V in Half of V in / 2 is directly added to the inductor L r With capacitor C r Both ends, so the flow through the switch Q 5 、Inductance L r , capacitor C r , capacitor C 2 The resonant inductor current i Lr The nonlinear rise completes the nonlinear charging of the charging module 3, wherein: D L is the duty cycle of the linear charging stage. Then, the switch Q 5 Turn off, and at the same time control the third primary bridge arm 23 and the switch Q 5 The switch on the same side is switch Q 3 The LLC resonant converter performs the normal resonant process, and the resonant inductor current i Lr The input voltage V in Together with the charging module 3, it transfers energy to the transformer and the secondary side. In each second half of the switching cycle, the lower switch of the second primary bridge arm 22, i.e., switch Q 6 First, the switch Q is turned on, and the other switches are turned off, so that the charging module 3 is nonlinearly charged; then, the control switch Q 6 Turn off, and at the same time control the third primary bridge arm 23 and the switch Q 6 The switch on the same side is switch Q 4 The other switches are turned off, and the LLC resonant converter performs the normal resonant process. 5 , switch Q 6 Capable of achieving zero current switching (ZCS), switch Q 3 , switch Q 4 Can achieve zero voltage switch-on (ZVS). The working waveform is as follows Figure 5 As shown, Q g5 Q is the switch 5 The driving waveform, Q g6 Q is the switch 6 The driving waveform, Q g3 Q is the switch 3 The driving waveform, Q g4 Q is the switch 4 The driving waveform, i Lr is the resonant inductor current, i Q5 is the current flowing through the switch Q 5 The current, i Q6 is the current flowing through the switch Q 6 The current, v Cr is the capacitance C r The voltage across the two ends, t is the time,T s For each cycle duration, D L is the duty cycle of the linear charging stage, D d is the duty cycle of the dead time. In the first stage [ t 0 , t 1 ], switch Q 5 is turned on, and the rest of the switches are turned off; in the second stage [ t 1 , t 2 ] and the third stage[ t 2 , t 3 ], switch Q 3 The remaining switches are turned off; in the fourth stage [ t 3 , t 4 ], all switches are turned off.

[0050] Please refer to Figure 6 When the LLC resonant converter operates in the dual-module low-gain mode, the output voltage V is achieved by changing the operating frequency of the LLC resonant converter. o The switch Q of the second primary bridge arm 22 is regulated, that is, the LLC resonant converter is subjected to PFM control. 5 With switch Q 6 Turn off and do not participate in work, control switch Q 3 With switch Q 4 Alternating conduction, switch Q 1 With switch Q 3 At the same time, switch Q 2 With switch Q 4 In each half switching cycle, after the normal resonance process is completed, the resonant inductor currents of the two resonant cavities are discharged nonlinearly through the body diode of the switch.

[0051] Please refer to Figure 7 When the LLC resonant converter operates in the dual-module high-gain mode, the switching frequency of the LLC resonant converter remains unchanged. By changing the switch Q of the second primary bridge arm 22 5 , switch Q 6 The duty cycle of the output voltage V o In each first half of the switching cycle, the upper switch of the second primary bridge arm 22, i.e., switch Q 5 First, the conduction time is 0.5 T sD L , at this time, all other switches are turned off, and the input voltage V in Half of V in / 2 is directly added to the inductor L r With capacitor C r Both ends, so the flow through the switch Q 5 、Inductance L r , capacitor C r , capacitor C 2 The resonant inductor current i Lr The nonlinear rise completes the nonlinear charging of the charging module 3. Then, the control switch Q 5 Turn off and control switch Q 1 , switch Q 3 The other switches are turned on, and the two resonant cavities simultaneously perform normal resonance. In each second half of the switching cycle, the lower switch of the second primary bridge arm 22, i.e., switch Q 6 First, the switch Q is turned on to perform nonlinear charging on the charging module 3, while the other switches are turned off. 6 Turn off and control switch Q 2 , switch Q 4 The other switches are turned off, and the two resonant cavities are in normal resonant process at the same time. 5 , switch Q 6 Capable of achieving zero current switching (ZCS), switch Q 1 , switch Q 2 , switch Q 3 , switch Q 4 Capable of achieving zero voltage switch-on (ZVS).

[0052] An LLC resonant converter of the present invention is simulated in the circuit simulation software PLECS, and the simulation parameters are shown in Table 1.

[0053] Table 1 LLC resonant converter simulation parameters The steady-state simulation waveforms of an LLC resonant converter in four working modes are as follows: Figure 8 (a) to 8(f), wherein, Figure 8 (a) is the steady-state waveform of the output voltage of 90V in the low-gain mode of a single module. Figure 8 (b) is the steady-state waveform when the output voltage is 100V at the critical point between the single-module high-gain mode and the single-module low-gain mode. Figure 8 (c) is the steady-state waveform of the output voltage of 180V in the single module high gain mode. Figure 8(d) is the steady-state waveform when the output voltage is 180V in the dual-module low-gain mode. Figure 8 (e) is the steady-state waveform when the output voltage is 200V at the critical point between the dual-module high-gain mode and the dual-module low-gain mode. Figure 8 (f) is the steady-state waveform of the output voltage of 360V in the dual-module high-gain mode, where: i Lr1 For transformer T 1 The resonant inductor current, i Lr2 For transformer T 2 The resonant inductor current, I o is the output current, Q g1 Q is the switch 1 As can be seen from the figure, under the condition of constant output current of 4A, the LLC resonant converter of the present invention can achieve a wide range of output voltage variation from 85V to 380V under the condition of input voltage of 400V. At the same time, the switching frequency of the LLC resonant converter varies from 90kHz to 135kHz, so when designing the LLC resonant converter, the excitation inductance L m1 , Excitation inductance L m2 Can be designed to be very large, so the excitation inductance L m1 The magnetizing inductor current i Lm1 , Excitation inductance L m2 The magnetizing inductor current i Lm2 With transformer T 1 The resonant inductor current i Lr1 、Transformer T 2 The resonant inductor current i Lr2 The primary side conduction loss and turn-off loss are greatly reduced, so the working efficiency of the LLC resonant converter in the full range is greatly improved.

[0054] The LLC resonant converter and control method of the present invention save a resonant inductor and a resonant capacitor by integrating the resonant cavity, which greatly reduces the circuit cost and volume. At the same time, a wide gain range can be achieved, which is more suitable for various occasions such as current new energy electricity consumption and power generation. In addition, since the switching frequency range of the LLC resonant converter of the present invention is very narrow and the soft switch is basically fully realized, the full range of working efficiency can be improved. Moreover, by adjusting the primary and secondary turns ratio of the transformer, a boost or buck function can be obtained, and at the same time, the secondary side of the transformer does not need a center tap structure, and the structure is simple. In summary, the LLC resonant converter of the present invention ensures a wide voltage gain range and improves the full range of working efficiency while reducing the volume, and is a better choice for a wide range DC / DC converter in new energy power generation and electricity consumption occasions.

[0055] Although the present invention has been disclosed as above by way of embodiments, it is not intended to limit the present invention. Any person having ordinary knowledge in the technical field may make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the scope of the attached patent application.

Claims

1. An LLC resonant converter, characterized in that: It includes a capacitor module, a primary side conversion module, a charging module, a transformer module and a secondary side conversion module. The capacitor module, the primary side conversion module, the transformer module and the secondary side conversion module are connected in sequence, and the charging module is connected between the capacitor module and the primary side conversion module.

2. An LLC resonant converter as claimed in claim 1, characterized in that: The capacitor module includes a first capacitor and a second capacitor, and the first capacitor and the second capacitor are connected in series.

3. An LLC resonant converter as claimed in claim 2, characterized in that: The primary side conversion module includes a first primary side bridge arm, a second primary side bridge arm, and a third primary side bridge arm. Two ends of the first primary side bridge arm, two ends of the second primary side bridge arm, and two ends of the third primary side bridge arm are connected in parallel, and the two ends after parallel connection are connected in parallel with two ends of the capacitor module.

4. An LLC resonant converter as claimed in claim 3, characterized in that: The charging module includes a first inductor and a third capacitor, wherein one end of the first inductor and the third capacitor connected in series is connected to a midpoint of the series connection of the first capacitor and the second capacitor, and the other end is connected to a midpoint of the bridge arm of the second primary bridge arm.

5. An LLC resonant converter as claimed in claim 4, characterized in that: The transformer module includes a first transformer and a second transformer, the first end of the primary winding of the first transformer is connected to the midpoint of the third primary bridge arm, the second end of the primary winding of the first transformer is connected to the midpoint of the second primary bridge arm, the first end of the primary winding of the second transformer is connected to the midpoint of the first primary bridge arm, and the second end of the primary winding of the second transformer is connected to the midpoint of the second primary bridge arm.

6. An LLC resonant converter as claimed in claim 5, characterized in that: The secondary side conversion module includes a first secondary side bridge arm, a second secondary side bridge arm, and a third secondary side bridge arm. The two ends of the first secondary side bridge arm, the two ends of the second secondary side bridge arm, and the two ends of the third secondary side bridge arm are connected in parallel; the first end of the secondary winding of the first transformer is connected to the midpoint of the first secondary side bridge arm, the second end of the secondary winding of the first transformer is connected to the first end of the secondary winding of the second transformer and the midpoint of the second secondary side bridge arm, and the second end of the secondary winding of the second transformer is connected to the midpoint of the third secondary side bridge arm.

7. An LLC resonant converter as claimed in claim 3, characterized in that: The first primary bridge arm includes a first switch and a second switch, and the first switch is connected in series with the second switch; the second primary bridge arm includes a fifth switch and a sixth switch, and the fifth switch is connected in series with the sixth switch; the third primary bridge arm includes a third switch and a fourth switch, and the third switch is connected in series with the fourth switch.

8. An LLC resonant converter as claimed in claim 6, characterized in that: The first secondary bridge arm, the second secondary bridge arm, and the third secondary bridge arm each include two switches connected in series.

9. A control method for an LLC resonant converter, characterized in that: Applied to an LLC resonant converter as described in any one of claims 1-8, including controlling the LLC resonant converter to operate in a single-module low-gain mode, a single-module high-gain mode, a dual-module low-gain mode, or a dual-module high-gain mode.

10. A control method for an LLC resonant converter as claimed in claim 9, characterized in that: When the LLC resonant converter operates in a single-module low-gain mode, the output voltage is regulated by changing the operating frequency of the LLC resonant converter, and the third switch and the fourth switch of the third primary bridge arm are controlled to be alternately turned on.

11. A control method for an LLC resonant converter as claimed in claim 9, characterized in that: When the LLC resonant converter operates in a single-module high-gain mode, the switching frequency of the LLC resonant converter remains unchanged, and the output voltage is adjusted by changing the duty cycle of the fifth switch and the sixth switch of the second primary bridge arm; in each first half of the switching cycle, the fifth switch of the second primary bridge arm is controlled to be turned on first, and then the fifth switch is controlled to be turned off and the third switch is turned on; in each second half of the switching cycle, the sixth switch of the second primary bridge arm is controlled to be turned on first, and then the sixth switch is controlled to be turned off and the fourth switch is turned on.

12. A control method for an LLC resonant converter as claimed in claim 9, characterized in that: When the LLC resonant converter operates in the dual-module low-gain mode, the output voltage is adjusted by changing the operating frequency of the LLC resonant converter, and the third switch and the fourth switch are controlled to be turned on alternately, the first switch and the third switch are turned on at the same time, and the second switch and the fourth switch are turned on at the same time.

13. A control method for an LLC resonant converter as claimed in claim 9, characterized in that: When the LLC resonant converter operates in the dual-module high-gain mode, the switching frequency of the LLC resonant converter remains unchanged, and the output voltage is adjusted by changing the duty cycle of the fifth switch and the sixth switch of the second primary bridge arm; in each first half of the switching cycle, the fifth switch of the second primary bridge arm is controlled to be turned on first, and then the fifth switch is controlled to be turned off, and the first switch and the third switch are turned on; in each second half of the switching cycle, the sixth switch of the second primary bridge arm is controlled to be turned on first, and then the sixth switch is controlled to be turned off, and the second switch and the fourth switch are turned on.

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