An LLC resonant converter and its control method

Abstract

The present invention discloses an LLC resonant converter and its control method, belonging to the technical field of power conversion. It includes a capacitor module, a primary conversion module, a charging module, a voltage conversion module, and a secondary conversion module. The capacitor module, the primary conversion module, the voltage conversion 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. An LLC resonant converter of the present invention ensures a wide voltage gain range and improves the full-range working efficiency while reducing the volume.

Description

Technical Field

[0001] The present invention relates to the technical field of power conversion, and particularly to an LLC resonant converter and its control method. Background Art

[0002] Energy is the core driving force for the production, development, and progress of contemporary society. However, with the increasingly prominent environmental and resource problems, traditional fossil fuels represented by coal and oil are gradually being replaced by new energy sources such as wind energy, solar energy, and natural gas hydrates. In new energy power generation and power consumption scenarios, such as photovoltaic power generation, electric vehicle charging, and on-vehicle electrical equipment power supply, higher requirements are imposed on the gain range of DC / DC converters. At the same time, improving the operating efficiency of the converter over the entire range is of great significance for improving equipment performance and reducing power loss.

[0003] LLC resonant converters are widely used in new energy power generation and other fields due to their simple structure, few components, zero-voltage switching (ZVS) of the primary switching tube, zero-current switching (ZCS) of the rectifier diode, high overall efficiency, low electromagnetic interference, the ability to improve power density using magnetic integration technology, and frequency modulation control. However, the traditional LLC resonant converter has a limited gain range and is greatly affected by the load. When adjusted over a wide range, the switching frequency changes significantly, which not only increases the design difficulty of magnetic components but also causes the efficiency of the converter to drop rapidly when the switching frequency is far from the resonant frequency. Therefore, broadening the gain range of the LLC resonant converter and improving its operating efficiency over the entire range are of great significance for improving equipment performance and reducing power loss. Summary of the Invention

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

[0005] To achieve the above object, the technical solution of the present invention is as follows:

[0006] An LLC resonant converter includes a capacitor module, a primary conversion module, a charging module, a voltage conversion module, and a secondary conversion module. The capacitor module, the primary conversion module, the voltage conversion 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.

[0007] In a specific embodiment, the above capacitor module includes a first capacitor and a second capacitor, and the first capacitor and the second capacitor are connected in series.

[0008] In a specific embodiment, the primary conversion module includes a first primary bridge arm, a second primary bridge arm, and a third primary bridge arm. The two ends of the first primary bridge arm, the two ends of the second primary bridge arm, and the two ends of the third primary bridge arm are connected in parallel. The two ends after parallel connection are connected in parallel with the two ends of the capacitor module.

[0009] In a specific embodiment, the charging module includes a first inductor and a third capacitor. One end of the series connection of the first inductor and the third capacitor is connected to the series midpoint of the first capacitor and the second capacitor, and the other end is connected to the midpoint of the second primary bridge arm.

[0010] In a specific embodiment, the voltage conversion 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.

[0011] In a specific embodiment, the secondary conversion module includes a first secondary bridge arm, a second secondary bridge arm, and a third secondary bridge arm. The two ends of the first secondary bridge arm, the two ends of the second secondary bridge arm, and the two ends of the third secondary 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 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 bridge arm, and the second end of the secondary winding of the second transformer is connected to the midpoint of the third secondary bridge arm.

[0012] In a specific embodiment, the first primary bridge arm includes a first switch and a second switch, and the first switch and the second switch are connected in series; the second primary bridge arm includes a fifth switch and a sixth switch, and the fifth switch and the sixth switch are connected in series; the third primary bridge arm includes a third switch and a fourth switch, and the third switch and the fourth switch are connected in series.

[0013] In a specific embodiment, each of the first secondary bridge arm, the second secondary bridge arm, and the third secondary bridge arm includes two switches connected in series.

[0014] The present invention also provides a control method for an LLC resonant converter, which is applied to the above-mentioned LLC resonant converter, and includes 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.

[0015] When the LLC resonant converter operates in the 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 conduct alternately.

[0016] When the LLC resonant converter operates in the single-module high-gain mode, the switching frequency of the LLC resonant converter remains unchanged, and the output voltage is regulated by changing the duty cycles 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 conduct first, and then, the fifth switch is 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 conduct first, and then, the sixth switch is turned off and the fourth switch is turned on.

[0017] When the LLC resonant converter operates in the dual-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 are controlled to conduct alternately, the first switch and the third switch conduct simultaneously, and the second switch and the fourth switch conduct simultaneously.

[0018] 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 regulated by changing the duty cycles 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 conduct first, and then, the fifth switch is turned off and the first switch and the third switch conduct; in each second half of the switching cycle, the sixth switch of the second primary bridge arm is controlled to conduct first, and then, the sixth switch is turned off and the second switch and the fourth switch conduct.

[0019] Advantageous effects: In the LLC resonant converter and its control method of the present invention, by integrating the resonant cavity, a resonant inductor and a resonant capacitor are omitted, greatly reducing the circuit cost and volume. At the same time, a wide gain range can be achieved, making it more suitable for various occasions such as current new energy power consumption and power generation. In addition, since the switching frequency range of the LLC resonant converter of the present invention is very narrow and soft switching is basically fully realized, the operating efficiency in the full range can be improved. Moreover, by adjusting the turns ratio of the primary and secondary windings of the transformer, step-up or step-down functions can be obtained, and there is no need for a center-tapped structure on the secondary side of the transformer, with a simple structure.

[0020] To make the above features and advantages of the invention more obvious and understandable, specific embodiments are hereinafter given and described in detail in conjunction with the accompanying drawings as follows. Description of the Drawings

[0021] Figure 1 It is a circuit schematic diagram of an LLC resonant converter of the present invention.

[0022] Figure 2 This is the equivalent circuit diagram of the LLC resonant converter of the present invention operating in the single-module low-gain mode.

[0023] Figure 3 This is the operating waveform diagram of the LLC resonant converter of the present invention operating in the single-module low-gain mode.

[0024] Figure 4 This is the equivalent circuit diagram of the LLC resonant converter of the present invention operating in the single-module high-gain mode.

[0025] Figure 5 This is the operating waveform diagram of the LLC resonant converter of the present invention operating in the single-module high-gain mode.

[0026] Figure 6 This is the equivalent circuit diagram of the LLC resonant converter of the present invention operating in the dual-module low-gain mode.

[0027] Figure 7 This is the equivalent circuit diagram of the LLC resonant converter of the present invention operating in the dual-module high-gain mode.

[0028] Figure 8 In (a) of [], it is the steady-state waveform diagram when the output voltage is 90V in the single-module low-gain mode. Figure 8 In (b) of [], it is the steady-state waveform diagram when the output voltage is 100V in the single-module high-gain mode. Figure 8 In (c) of [], it is the steady-state waveform diagram when the output voltage is 180V in the single-module high-gain mode. Figure 8 In (d) of [], it is the steady-state waveform diagram when the output voltage is 180V in the dual-module low-gain mode. Figure 8 In (e) of [], it is the steady-state waveform diagram when the output voltage is 200V in the dual-module high-gain mode. Figure 8 In (f) of [], it is the steady-state waveform diagram when the output voltage is 360V in the dual-module high-gain mode. Detailed implementation manners

[0029] To make the objectives and technical solutions of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the described embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0030] Figure 1 This is the circuit schematic diagram of an LLC resonant converter of the present invention. As Figure 1As shown, an LLC resonant converter of the present invention includes a capacitor module 1, a primary conversion module 2, a charging module 3, a voltage conversion module 4, and a secondary conversion module 5. The input voltage V in , the capacitor module 1, the primary conversion module 2, the voltage conversion module 4, the secondary conversion module 5, and the output voltage V o are connected in sequence. The charging module 3 is connected between the capacitor module 1 and the primary conversion module 2.

[0031] Further, the capacitor module 1 includes a capacitor C 1 and a capacitor C 2 . The capacitor C 1 and the capacitor C 2 are in series, and the two ends after series connection are in parallel with the input voltage V in .

[0032] Further, the primary conversion module 2 includes a first primary bridge arm 21, a second primary bridge arm 22, and a third primary bridge arm 23. The two ends of the first primary bridge arm 21, the two ends of the second primary bridge arm 22, and the two ends of the third primary bridge arm 23 are in parallel, and the two ends after parallel connection are in parallel with the two ends of the capacitor module 1.

[0033] More specifically, the first primary bridge arm 21 includes a switch Q 1 and a switch Q 2 . The switch Q 1 and the switch Q 2 are in series, and the series midpoint is the bridge arm midpoint of the first primary bridge arm 21; the second primary bridge arm 22 includes a switch Q 5 and a switch Q 6 . The switch Q 5 and the switch Q 6 are in series, and the series midpoint is the bridge arm midpoint of the second primary bridge arm 22; the third primary bridge arm 23 includes a switch Q 3 and a switch Q 4 . The switch Q 3 and the switch Q 4 are in series, and the series midpoint is the bridge arm midpoint of the third primary bridge arm 23. Among them, the second primary bridge arm 22 is an auxiliary bridge arm.

[0034] 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 are MOSFETs.

[0035] Optionally, the switch Q1 and the switch Q 2 and the switch Q 3 and the switch Q 4 and the switch Q 5 and the switch Q 6 may also be other switching devices, and the present invention is not limited thereto.

[0036] Further, the voltage transformation module 4 includes a transformer T 1 and the transformer T 2 , the first end of the primary winding of the transformer T 1 is connected to the midpoint of the third primary bridge arm 23, and the second end of the primary winding of the transformer T 1 is connected to the midpoint of the second primary bridge arm 22, and the first end of the primary winding of the transformer T 2 is connected to the midpoint of the first primary bridge arm 21, and the second end of the primary winding of the transformer T 2 is connected to the midpoint of the second primary bridge arm 22. Among them, L m1 is the exciting inductance of the transformer T 1 , L m2 is the exciting inductance of the transformer T 2 .

[0037] Further, the secondary conversion module 5 includes a first secondary bridge arm 51, a second secondary bridge arm 52, and a third secondary bridge arm 53. The two ends of the first secondary bridge arm 51, the two ends of the second secondary bridge arm 52, and the two ends of the third secondary bridge arm 53 are connected in parallel, and the two ends after parallel connection are connected in parallel with the output voltage V o .

[0038] More specifically, the first secondary bridge arm 51 includes switches D 1 , switches D 2 , the switch D 1 is connected in series with the switch D 2 , and the series midpoint is the midpoint of the first secondary bridge arm 51; the second secondary bridge arm 52 includes switches D 3 , switches D 4 , the switch D 3 is connected in series with the switch D 4 , and the series midpoint is the midpoint of the second secondary bridge arm 52; the third secondary bridge arm 53 includes switches D 5 , switches D 6 , the switch D 5 is connected in series with the switch D 6 , and the series midpoint is the midpoint of the third secondary bridge arm 53.

[0039] In a specific embodiment, the switch D 1 and the switch D 2 and the switch D 3 and the switch D 4 and the switch D 5 and the switch D 6 are diodes.

[0040] Optionally, the switch D 1 and the switch D 2 and the switch D 3 and the switch D 4 and the switch D 5 and the switch D 6 may also be other switching devices, and the present invention is not limited thereto.

[0041] Wherein, the first end of the secondary winding of the transformer T 1 is connected to the midpoint of the bridge arm of the first secondary bridge arm 51, and the second end of the secondary winding of the transformer T 1 is connected to the first end of the secondary winding of the transformer T 2 and the midpoint of the bridge arm of the second secondary bridge arm 52, and the second end of the secondary winding of the transformer T 2 is connected to the midpoint of the bridge arm of the third secondary bridge arm 53.

[0042] Furthermore, the charging module 3 includes an inductor L r and a capacitor C r , one end of the series connection of the inductor L r and the capacitor C r is connected to the series midpoint of the capacitor C 1 and the capacitor C 2 , and the other end is connected to the midpoint of the bridge arm of the second primary bridge arm 22.

[0043] Optionally, both ends of the parallel connection of the first secondary bridge arm 51, the second secondary bridge arm 52, and the third secondary bridge arm 53 are also connected in parallel with a resistor R L , wherein the voltage across the resistor R L is the output voltage V o , and the resistor R L is the load.

[0044] Optionally, an LLC resonant converter of the present invention further includes a capacitor C o , the capacitor C o is connected in parallel with the output voltage V o , and the capacitor C o functions as output filtering.

[0045] Optionally, the input voltage Vin It includes a stable DC bus voltage in the power supply system, a DC power supply with a wide range of variations, etc., which can be determined according to the application scenario.

[0046] Next, the function of an LLC resonant converter of the present invention will be further introduced. The primary conversion module 2 functions as an inverter to invert the input voltage V in into an alternating current; the transformer module 4 includes two transformers, that is, two matching resonant cavities. In this application, the resonant inductors and resonant capacitors of the two resonant cavities are shared, and an integrated resonant inductor and resonant capacitor can be obtained, which is the inductor L r and the capacitor C r , the inductor L r and the capacitor C r are connected in series between the series midpoint of the capacitor and the midpoint of the second primary bridge arm to form a charging module. In order to ensure that the resonant frequencies of the two integrated resonant cavities remain unchanged when they work alone or simultaneously, the parameters of the two resonant cavities before integration are C r1 = C r2 , L r1 = L r2 When, then the parameters of the integrated resonant cavity C r = C r1 / 2= C r2 / 2, L r =2 L r1 =2 L r2 , where C r1 is the resonant capacitor of the first resonant cavity before integration, C r2 is the resonant capacitor of the second resonant cavity before integration, L r1 is the resonant inductor 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 require a center tap structure, and the turns ratios of the transformer T 1 and the transformer T 2 are both n :1. Two full-bridge rectifier structures form a three-bridge arm rectifier structure in the secondary conversion module 5 of this application by sharing a set of bridge arms, and rectify the voltage converted by the transformer module 4 to provide the output voltage V 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.

[0047] The following is an introduction to a control method of an LLC resonant converter according to the present invention.

[0048] 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.

[0049] 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 , the switch Q 3 conducts, and the switch Q 4 turns off; in the third stage t 2 , t 3 , the switch Q 3 and the switch Q 4 are both turned off.

[0050] The working principle of an LLC resonant converter of the present invention in the single-module low-gain mode is similar to that of a traditional half-bridge LLC resonant converter using frequency modulation control. The difference lies in the third stage t 2 , t 3 . In t 2 at the moment, the switch Q 3 turns off, and the resonant inductor current i Lr remains flowing in the original direction, that is, discharges the junction capacitors of the switch Q 6 and the switch Q 4 . When the discharge is completed, the resonant current freewheels through the switch Q 6 . Therefore, the resonant inductor current i Lr decreases non-linearly in this stage, and at the same time, this stage provides the condition for the zero-voltage turn-on of the switch Q 4 .

[0051] 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 duty cycles of the switches Q 5 and the switch Q 6 of the second primary bridge arm 22, the output voltage V o is regulated. In this mode, the switches Q 1 and the switch Q 2 of the first primary bridge arm 21, the transformer T 2 , and the third secondary bridge arm 53 do not participate in the operation. In each first half of the switching cycle, the upper switch of the second primary bridge arm 22, that is, the switch Q 5 , is first turned on, and the conduction time is 0.5 T s D L . At this time, the other switches are all turned off, and half of the input voltage V in , Vin is directly added to the inductor L r and the capacitor C r at both ends, so the current flowing through the switch Q 5 and the inductor L r and the capacitor C r and the capacitor C 2 is the resonant inductor current i Lr rises non-linearly, completing the non-linear charging of the charging module 3, where D L is the duty cycle of the linear charging stage. Subsequently, the control switch Q 5 is turned off, and at the same time, the switch on the same side as the switch Q 5 in the third primary bridge arm 23, that is, the switch Q 3 is turned on. At this time, all other switches are turned off, and the LLC resonant converter performs a normal resonant process. The resonant inductor current i Lr decreases in a sinusoidal form. During this period, the input voltage V in transfers energy to the transformer and the secondary side together with the charging module 3. In each subsequent half-switching period, the lower switch of the second primary bridge arm 22, that is, the switch Q 6 is first turned on. At this time, all other switches are turned off, and the charging module 3 is non-linearly charged; subsequently, the control switch Q 6 is turned off, and at the same time, the switch on the same side as the switch Q 6 in the third primary bridge arm 23, that is, the switch Q 4 is turned on. At this time, all other switches are turned off, and the LLC resonant converter performs a normal resonant process. Among them, the switch Q 5 and the switch Q 6 can achieve zero-current switching (ZCS), and the switch Q 3 and the switch Q 4 can achieve zero-voltage switching (ZVS). The working waveforms are as Figure 5 shown, Q g5 is the driving waveform of the switch Q 5 , Q g6 is the driving waveform of the switch Q 6 , Q g3 is the driving waveform of the switch Q 3 , Q g4 is the driving waveform of the switch Q 4 , i Lr is the resonant inductor current, i Q5 is the current flowing through the switch Q 5 , i Q6 is the current flowing through the switch Q 6 , v Cr is the capacitor C rThe 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.

[0052] 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.

[0053] 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 Ts D L , at this time, other switches are all turned off, and the input voltage V in half of which, V in / 2, is directly applied across the inductor L r and the capacitor C r . Therefore, the resonant inductor current flowing through the switch Q 5 , the inductor L r , the capacitor C r , the capacitor C 2 rises non-linearly, completing the non-linear charging of the charging module 3. Subsequently, control the switch Q i Lr to turn off, and at the same time control the switch Q 5 to turn on, and the switch Q 1 , the switch Q 3 to turn on. At this time, other switches are all turned off, and the two resonant cavities simultaneously carry out the normal resonance process. In each subsequent half-switching period, control the lower switch of the second primary bridge arm 22, that is, the switch Q 6 to turn on first to perform non-linear charging on the charging module 3. At this time, other switches are all turned off; subsequently, control the switch Q 6 to turn off, and at the same time control the switch Q 2 , the switch Q 4 to turn on. At this time, other switches are all turned off, and the two resonant cavities simultaneously carry out the normal resonance process. Among them, the switch Q 5 , the switch Q 6 can achieve zero-current switching (ZCS), and the switch Q 1 , the switch Q 2 , the switch Q 3 , the switch Q 4 can achieve zero-voltage switching (ZVS).

[0054] The LLC resonant converter of the present invention is simulated in the circuit simulation software PLECS, and the simulation parameters are shown in Table 1.

[0055] Table 1 LLC resonant converter simulation parameters

[0056]

[0057] The steady-state simulation waveforms of the LLC resonant converter of the present invention in four operating modes are respectively as shown in Figure 8 (a) to 8(f), where Figure 8 (a) is the steady-state waveform when the output voltage is 90V in the single-module low-gain mode, 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 when the output voltage is 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 when the output voltage is 360V in the dual-module high-gain mode, where, i Lr1 is the resonant inductor current of transformer T 1 ; i Lr2 is the resonant inductor current of transformer T 2 , I o is the output current, Q g1 is the driving waveform of switch Q 1 . It can be seen from the figure that in the case of a constant output current of 4A, an LLC resonant converter of the present invention can achieve a wide range of output voltage variations from 85V to 380V at an input voltage of 400V. At the same time, the variation range of the switch frequency of the LLC resonant converter is 90kHz to 135kHz. Therefore, when designing the LLC resonant converter, the magnetizing inductance L m1 , the magnetizing inductance L m2 can be designed to be very large. Therefore, the magnetizing inductance current L m1 of the magnetizing inductance i Lm1 , the magnetizing inductance current L m2 of the magnetizing inductance i Lm2 and the resonant inductor current 1 of transformer T i Lr1 , the resonant inductor current 2 of transformer T i Lr2 are small, and the conduction loss and turn-off loss of the primary side are greatly reduced. Therefore, the operating efficiency of the LLC resonant converter is greatly improved in the full range.

[0058] 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.

[0059] 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 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 capacitor module includes a first capacitor and a second capacitor, and the first capacitor is connected in series with the second capacitor; the primary conversion module includes a first primary bridge arm, a second primary bridge arm, and a third primary bridge arm, and the two ends of the first primary bridge arm, the two ends of the second primary bridge arm, and the two ends of the third primary 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; the charging module includes a first inductor and a third capacitor, and 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; 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 bridge arm of the third primary bridge arm, the second end of the primary winding of the first transformer is connected to the midpoint of the bridge arm of the second primary bridge arm, the first end of the primary winding of the second transformer is connected to the midpoint of the bridge arm 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 bridge arm of the second primary bridge arm; LLC resonant converter has four operating modes, namely single module low gain mode, single module high gain mode, dual module low gain mode, and dual module high gain mode; When the LLC resonant converter operates in a single-module low-gain mode, the third switch and the fourth switch of the third primary bridge arm are controlled to be alternately turned on; When the LLC resonant converter operates in a single-module high-gain mode, 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; When the LLC resonant converter operates in the dual-module low-gain mode, 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; When the LLC resonant converter operates in the dual-module high-gain mode, 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.

2. An LLC resonant converter as claimed in claim 1, 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.

3. An LLC resonant converter as claimed in claim 1, 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.

4. An LLC resonant converter as claimed in claim 2, 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.

5. A control method for an LLC resonant converter, characterized in that: Applicable to an LLC resonant converter as claimed in any one of claims 1 to 4, comprising: the LLC resonant converter has four operating modes, namely, a single-module low-gain mode, a single-module high-gain mode, a dual-module low-gain mode, and a dual-module high-gain mode; When the LLC resonant converter operates in a single-module low-gain mode, the third switch and the fourth switch of the third primary bridge arm are controlled to be alternately turned on; When the LLC resonant converter operates in a single-module high-gain mode, 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; When the LLC resonant converter operates in the dual-module low-gain mode, 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; When the LLC resonant converter operates in the dual-module high-gain mode, 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.

6. A control method for an LLC resonant converter as claimed in claim 5, characterized in that: When the LLC resonant converter operates in a single-module low-gain mode, the output voltage is adjusted by changing the operating frequency of the LLC resonant converter.

7. A control method for an LLC resonant converter as claimed in claim 5, 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 regulated by changing the duty ratio of the fifth switch and the sixth switch of the second primary bridge arm.

8. A control method for an LLC resonant converter as claimed in claim 5, characterized in that: When the LLC resonant converter operates in a dual-module low-gain mode, the output voltage is regulated by changing the operating frequency of the LLC resonant converter.

9. A control method for an LLC resonant converter as claimed in claim 5, 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 regulated by changing the duty cycle of the fifth switch and the sixth switch of the second primary bridge arm.

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