A dual transformer-based wide gain ZVS hybrid dc-dc converter

Abstract

The application discloses a wide-gain ZVS hybrid DC converter based on double transformers, and belongs to the technical field of DC / DC DC converters. The wide-gain ZVS hybrid DC converter comprises an LLC resonant converter and a PWM full-bridge converter. The LLC resonant converter comprises a first full-bridge inverter, an LLC resonant cavity, a first transformer and a first full-bridge rectifier. The PWM full-bridge converter comprises a second full-bridge inverter, a second transformer and a second full-bridge rectifier. The LLC resonant converter and the PWM full-bridge converter share a common inverter bridge arm on the primary side and share a common rectifier bridge arm on the secondary side. The hybrid DC converter can fully exert the advantages of high efficiency of the LLC resonant converter and wide output regulation capability of the PWM converter, so as to realize complementary advantages of the two converters, reduce the system loss and improve the overall efficiency when the converter system has a wide gain range.

Description

Technical Field

[0001] This invention relates to the field of DC / DC converter technology, and in particular to a wide-gain ZVS hybrid DC / DC converter based on dual transformers. Background Technology

[0002] In recent years, wide-gain-range LLC resonant converters have become a hot topic in DC / DC converter research both domestically and internationally. In traditional LLC resonant converters, the resonant current lags the voltage during normal operation, causing the LLC to operate in the inductive region. The primary-side switch of the transformer can achieve zero-voltage turn-on (ZVS) across the entire load range, while the secondary-side diode can achieve zero-current turn-off at low resonant frequencies. The ZVS of the primary-side switch reduces system switching losses, enabling the converter to achieve ideal efficiency even at high switching frequencies, thereby improving the overall power density of the converter.

[0003] Frequency conversion control (PFM) is one of the traditional control methods used in LLC resonant converters. By adjusting the switching frequency, the components of the resonant cavity exhibit different impedance values, thereby adjusting the voltage division between the transformer's magnetizing inductance and the load. With a fixed input voltage and transformer turns ratio, this allows for variations in the load voltage. In traditional LLC resonant converters, to further widen the gain range, the ratio of resonant inductance to magnetizing inductance is reduced. However, as the magnetizing inductance decreases, the circulating current on the primary side of the transformer increases, exacerbating the turn-off and conduction losses of the primary-side switches, further affecting the overall system efficiency. Therefore, a wide gain range and high efficiency are somewhat contradictory characteristics of LLC resonant converters. Researching LLC resonant converters that simultaneously possess both wide gain range and high efficiency is of great significance.

[0004] To maintain the soft-switching characteristics and high efficiency of LLC resonant converters while improving the system's gain range, researchers have proposed many methods. One approach is to upgrade the topology, and another is to optimize the control and modulation strategies. While existing technologies can broaden the gain range of LLC resonant converters, they still introduce problems such as high losses and low power density, limiting the converter's application scope.

[0005] In general, the change in switching frequency of a traditional LLC resonant converter in frequency conversion modulation (PFM) mode will cause the operating point to deviate from the resonant point, causing the system to deviate from the converter's optimal operating state. Furthermore, when the LLC resonant converter operates at a fixed frequency at the resonant frequency point, it is in the state of a DC transformer (DCX). Although it can exert its best efficiency advantage, it does not have output regulation capability and is difficult to meet load requirements. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a wide-gain ZVS hybrid DC-DC converter based on dual transformers, which solves the problems of how to expand the wide gain range of LLC resonant converter, reduce circulating current, reduce the switching loss of converter, and improve system efficiency.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0008] A wide-gain ZVS hybrid DC-DC converter based on dual transformers includes an LLC resonant converter and a PWM full-bridge converter. The LLC resonant converter includes a first full-bridge inverter, an LLC resonant cavity, a first transformer, and a first full-bridge rectifier. The PWM full-bridge converter includes a second full-bridge inverter, a second transformer, and a second full-bridge rectifier. The primary side of the LLC resonant converter and the PWM full-bridge converter share one inverter bridge arm, and the secondary side shares one rectifier bridge arm.

[0009] A further improvement of the technical solution of the present invention is that: the first full-bridge inverter in the LLC resonant converter includes four high-frequency switching transistors: a first switching transistor S1, a second switching transistor S2, a third switching transistor S3, and a fourth switching transistor S4; the source of the first switching transistor S1 and the drain of the second switching transistor S2 are connected to form the first bridge arm, the source of the third switching transistor S3 and the drain of the fourth switching transistor S4 are connected to form the second bridge arm, and the input voltage is connected to the drain of the first switching transistor S1, the drain of the third switching transistor S3, the source of the second switching transistor S2, and the source of the fourth switching transistor S4.

[0010] A further improvement of the technical solution of the present invention is that: the LLC resonant cavity includes a resonant capacitor, a resonant inductor and a first transformer, the resonant capacitor is connected to the midpoint of the first bridge arm, and is connected to the midpoint of the second bridge arm via the resonant inductor and the primary winding of the first transformer.

[0011] A further improvement of the technical solution of the present invention is that: the first full-bridge rectifier bridge in the LLC resonant converter includes four uncontrolled diodes: a first diode D1, a second diode D2, a third diode D3, and a fourth diode D4; the midpoint of the bridge arm formed by the first diode D1 and the second diode D2 is connected to the secondary winding of the first transformer, and then connected to the midpoint of the bridge arm formed by the third diode D3 and the fourth diode D4 via the secondary winding of the first transformer.

[0012] A further improvement of the technical solution of the present invention is that: the second full-bridge inverter in the PWM full-bridge converter includes four high-frequency switching transistors and one leakage inductor. The four high-frequency switching transistors include a third switching transistor S3, a fourth switching transistor S4, a fifth switching transistor S5, and a sixth switching transistor S6. The source of the third switching transistor S3 and the drain of the fourth switching transistor S4 are connected to form the second bridge arm, and the source of the fifth switching transistor S5 and the drain of the sixth switching transistor S6 are connected to form the third bridge arm. The input voltage is connected to the drain of the third switching transistor S3, the drain of the fifth switching transistor S5, the source of the fourth switching transistor S4, and the source of the sixth switching transistor S6. The leakage inductor is connected to the midpoint of the second bridge arm and then connected to the midpoint of the third bridge arm via the primary winding of the second transformer.

[0013] A further improvement of the technical solution of the present invention is that: the second full-bridge rectifier bridge in the PWM full-bridge converter includes four uncontrolled diodes: a third diode D3, a fourth diode D4, a fifth diode D5, and a sixth diode D6. The midpoint of the bridge arm formed by the third diode D3 and the fourth diode D4 is connected to the secondary winding of the second transformer, and then connected to the midpoint of the bridge arm formed by the fifth diode D5 and the sixth diode D6 via the secondary winding of the second transformer.

[0014] A further improvement of the technical solution of the present invention is that: when the hybrid DC-DC converter is in operation, the resonant cavity of the LLC resonant converter causes the inductor current to lag the voltage, and the LLC resonant converter operates in the inductive region, which enables the zero-voltage turn-on of the first switch S1, the second switch S2, the third switch S3 and the fourth switch S4 on the first and second bridge arms, and the PWM full-bridge converter enables the zero-voltage turn-on of the fifth switch S5 and the sixth switch S6 on the third bridge arm.

[0015] The technological advancements achieved by this invention due to the adoption of the above technical solutions are as follows:

[0016] 1. The present invention proposes a wide-gain ZVS hybrid DC-DC converter based on dual transformers, which consists of three bridge arms formed by parallel connection of the primary sides of LLC resonant converter and PWM full-bridge converter, and the secondary sides of dual transformers connected in series with the rectifier bridge. Thanks to the soft-switching characteristics of LLC resonant converter and PWM full-bridge converter, it can achieve zero-voltage turn-on across the entire load range.

[0017] 2. Compared with traditional LLC resonant converters or PWM full-bridge converters, the proposed wide-gain ZVS hybrid DC-DC converter based on dual transformers can simply and effectively achieve a wide range of converter gains due to the dual energy transmission channels of the LLC resonant converter and the PWM full-bridge converter.

[0018] 3. The hybrid DC-DC converter proposed in this invention can fully leverage the advantages of the high efficiency of the LLC resonant converter and the wide output regulation capability of the PWM converter, so as to achieve complementary advantages of the two converters. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of a wide-gain ZVS hybrid DC-DC converter system based on dual transformers proposed in an embodiment of the present invention;

[0021] Figure 2 This is a circuit diagram of a wide-gain ZVS hybrid DC-DC converter system based on dual transformers proposed in an embodiment of the present invention;

[0022] Figure 3 This is a circuit diagram of a wide-gain ZVS hybrid DC-DC converter based on dual transformers, according to an embodiment of the present invention.

[0023] Figure 4 This is a schematic diagram of the second working mode of a wide-gain ZVS hybrid DC-DC converter based on dual transformers proposed in an embodiment of the present invention.

[0024] Figure 5 This is a waveform diagram of a wide-gain ZVS hybrid DC-DC converter system based on dual transformers proposed in an embodiment of the present invention. Detailed Implementation

[0025] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification, claims and accompanying drawings of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such processes, methods, products or devices.

[0026] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0027] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0028] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments:

[0029] like Figure 1 , 2 As shown, a wide-gain ZVS hybrid DC-DC converter based on dual transformers includes an LLC resonant converter and a PWM full-bridge converter. The LLC resonant converter includes a first full-bridge inverter, an LLC resonant cavity, a first transformer, and a first full-bridge rectifier. The PWM full-bridge converter includes a second full-bridge inverter, a second transformer, and a second full-bridge rectifier. The primary side of the LLC resonant converter and the PWM full-bridge converter share one inverter bridge arm, and the secondary side shares one rectifier bridge arm.

[0030] Specifically, such as Figure 2 As shown, the first full-bridge inverter in the LLC resonant converter includes four high-frequency switching transistors: a first switching transistor S1, a second switching transistor S2, a third switching transistor S3, and a fourth switching transistor S4. The source of the first switching transistor S1 and the drain of the second switching transistor S2 are connected to form the first bridge arm, and the source of the third switching transistor S3 and the drain of the fourth switching transistor S4 are connected to form the second bridge arm. The input voltage is connected to the drain of the first switching transistor S1, the drain of the third switching transistor S3, the source of the second switching transistor S2, and the source of the fourth switching transistor S4.

[0031] The LLC resonant cavity includes a resonant capacitor, a resonant inductor, and a first transformer. The resonant capacitor is connected to the midpoint of the first bridge arm and is connected to the midpoint of the second bridge arm via the resonant inductor and the primary winding of the first transformer.

[0032] The first full-bridge rectifier bridge in the LLC resonant converter includes four uncontrolled diodes: first diode D1, second diode D2, third diode D3, and fourth diode D4. The midpoint of the bridge arm formed by the first diode D1 and the second diode D2 is connected to the secondary winding of the first transformer, and then connected to the midpoint of the bridge arm formed by the third diode D3 and the fourth diode D4 via the secondary winding of the first transformer.

[0033] The PWM full-bridge converter includes a second full-bridge inverter, a second transformer, and a second full-bridge rectifier.

[0034] The second full-bridge inverter of the PWM full-bridge converter includes four high-frequency switching transistors and one leakage inductor. The four high-frequency switching transistors are a third switch S3, a fourth switch S4, a fifth switch S5, and a sixth switch S6. The source of the third switch S3 and the drain of the fourth switch S4 are connected to form the second bridge arm, and the source of the fifth switch S5 and the drain of the sixth switch S6 are connected to form the third bridge arm. The input voltage is connected to the drain of the third switch S3, the drain of the fifth switch S5, the source of the fourth switch S4, and the source of the sixth switch S6. The leakage inductor is connected to the midpoint of the second bridge arm and then connected to the midpoint of the third bridge arm via the primary winding of the second transformer.

[0035] The second full-bridge rectifier bridge in the PWM full-bridge converter includes four uncontrolled diodes: the third diode D3, the fourth diode D4, the fifth diode D5, and the sixth diode D6. The midpoint of the bridge arm formed by the third diode D3 and the fourth diode D4 is connected to the secondary winding of the second transformer, and then connected to the midpoint of the bridge arm formed by the fifth diode D5 and the sixth diode D6 via the secondary winding of the second transformer.

[0036] In this invention, both the first full-bridge inverter in the LLC resonant converter and the second full-bridge inverter in the PWM full-bridge converter are connected to the midpoint of the second bridge arm. The LLC resonant converter and the PWM full-bridge converter share one inverter bridge arm. That is, the second bridge arm formed by connecting the source of the third switch S3 and the drain of the fourth switch S4 is a shared inverter bridge arm for the LLC resonant converter and the PWM full-bridge converter.

[0037] In this invention, the first full-bridge rectifier in the LLC resonant converter and the second full-bridge rectifier in the PWM full-bridge converter are both connected to the midpoint of the bridge arm formed by the third diode D3 and the fourth diode D4. The second full-bridge rectifier is connected to the load after a filter capacitor is connected in parallel. That is, the LLC resonant converter and the PWM full-bridge converter share a rectifier bridge arm.

[0038] The present invention provides a wide-gain ZVS hybrid DC-DC converter based on dual transformers. Under normal operating conditions, the LLC resonant converter primarily transmits power to the load, while the PWM full-bridge converter handles the remaining power transmission. Therefore, in this mode, the switching frequency of the LLC resonant converter remains constant, approximating its resonant frequency. The LLC resonant converter gain is close to 1, and the PWM full-bridge converter regulates the voltage, thus extending the wide gain range of the LLC resonant converter. Specifically, under operating conditions, the resonant cavity of the LLC resonant converter causes the inductor current to lag the voltage, allowing the LLC resonant converter to operate in the inductive region. This enables zero-voltage turn-on (ZVS) of the first, second, third, and fourth switches (S1, S2, S3, and S4) on the first and second bridge arms. The PWM full-bridge converter enables zero-voltage turn-on (ZVS) of the fifth and sixth switches (S5 and S6) on the third bridge arm.

[0039] Specifically, in working mode 1, such as Figure 3 As shown, when the gates of the first switch S1, fourth switch S4, and fifth switch S5 on the first bridge arm, second bridge arm, and third bridge arm receive a high-level signal from the driving device, the drains and sources of the first switch S1, fourth switch S4, and fifth switch S5 are turned on, and the input voltage V s The resonant capacitance C of the LLC resonant cavity is connected through the first switch S1, the fourth switch S4, and the first switch S4. r Resonant inductor L r Connected in phase, and then connected to the magnetizing inductor L in the first transformer. m1 After voltage transformation by the first transformer, the output is sent to the first full-bridge rectifier bridge. The first diode D1 and the fourth diode D4 in the first full-bridge rectifier bridge rectify the AC voltage transformed by the second transformer to obtain a DC voltage, which is finally output to the load via the filter capacitor C1. Simultaneously, the input voltage V... s It is also connected to the leakage inductor L in the PWM full-bridge converter via the fifth switch S5. k2 Then, it connects with the magnetizing inductance L in the second transformer. m2 The AC power is converted to DC power by the first diode D1 and the fourth diode D4 in the first full-bridge rectifier bridge after being connected to the second transformer. The DC power is then output to the load by the filter capacitor C1, thus transferring energy. In this operation, the LLC resonant converter and the PWM full-bridge converter, after forming an integrated primary and secondary structure, jointly realize the energy transfer between the primary input voltage and the output load.

[0040] Specifically, in working mode 2, such as Figure 4As shown, when the gates of the second switch S2, the third switch S3, and the sixth switch S6 of the first bridge arm, the second bridge arm, and the third bridge arm receive a high-level signal from the driving device, the drain and source of the second switch S2, the third switch S3, and the sixth switch S6 are turned on, and the input voltage V s The resonant capacitance C of the LLC resonant cavity is connected through the second switch S2, the third switch S3, and the second switch S2. r Resonant inductor L r Connected in phase, and then connected to the magnetizing inductor L in the primary winding of the first transformer. m1 After voltage transformation by the first transformer, the output is sent to the first full-bridge rectifier bridge. The second diode D2 and the third diode D3 in the first full-bridge rectifier bridge rectify the AC voltage transformed by the second transformer to obtain a DC voltage, which is finally output to the load via the filter capacitor C1. Simultaneously, the input voltage is also connected to the leakage inductor L in the PWM full-bridge converter via the sixth switch S6. k2 Then, it connects with the magnetizing inductance L in the primary winding of the second transformer. m2 The AC power is converted to DC power by the second diode D2 and the third diode D3 in the first full-bridge rectifier bridge after being connected to the second transformer. Finally, the DC power is output to the load through the filter capacitor C1, thus transferring energy. In this operation, the LLC resonant converter and the PWM full-bridge converter, after forming a primary and secondary integrated structure, also jointly realize the energy transfer between the input voltage and the output load.

[0041] The invention has two main advantages:

[0042] (1) The advantage of LLC resonant converter and PWM full-bridge converter is that the first switch S1 to the sixth switch S6 on the first bridge arm, the second bridge arm and the third bridge arm can be turned on with zero voltage across the entire load range. Zero voltage turn-on of the switch means a reduction in turn-on losses, which can improve the overall efficiency of the system.

[0043] Specifically, in order to achieve zero-voltage turn-on for all high-frequency switches, after the second switch S2 and the third switch S3 are turned off, and before the first switch S1 and the fourth switch S4 are turned on, the resonant capacitor C in the LLC resonant cavity... r and resonant inductance L r This will cause the parasitic capacitance C of the first switch S1 and the fourth switch S4 to increase. s1 C s4With zero discharge, the drain-source voltages of the first switch S1 and the fourth switch S4 are zero. Under this condition, the gates of the first switch S1 and the fourth switch S4 receive a high-level driving signal, completing zero-voltage turn-on. Similarly, after the first switch S1 and the fourth switch S4 are turned off and before the second switch S2 and the third switch S3 are turned on, the resonant capacitor C in the LLC resonant cavity... r and resonant inductance L r This will cause the parasitic capacitance C of the second switch S2 and the third switch S3 to increase. s2 C s3 When the discharge is zero, the drain-source voltages of the second switch S2 and the third switch S3 are zero. Under this condition, the gates of the second switch S2 and the third switch S3 receive a high-level signal from the driving device, thus completing zero-voltage turn-on.

[0044] Meanwhile, after the sixth switch S6 is turned off and before the fifth switch S5 is turned on, the leakage inductance L of the second transformer in the PWM full-bridge converter... k2 This will cause the parasitic capacitance C of the fifth switch S5 to... s5 Discharge causes the voltage between the drain and source of the fifth switch S5 to be zero. When the gate of the fifth switch S5 receives a high-level signal from the driver, the fifth switch S5 meets the condition for zero-voltage turn-on and can successfully achieve zero-voltage turn-on. Similarly, after the fifth switch S5 is turned off and before the sixth switch S6 is turned on, the leakage inductance L in the PWM full-bridge converter... k2 This will cause the parasitic capacitance C of the sixth switch S6 to... s6 Discharge makes the voltage between the drain and source of the sixth switch S6 zero. When the gate of the sixth switch S6 receives a high-level signal from the driving device, the sixth switch S6 reaches the condition for zero-voltage turn-on and can successfully achieve zero-voltage turn-on.

[0045] (2) To achieve high efficiency and a wide gain range for the overall converter, the converter can operate in the following two modes: The main power transfer of the converter is accomplished by the input power supply, the first switch S1, second switch S2, third switch S3, and fourth switch S4 on the first and second bridge arms (high-frequency switches), the LLC resonant cavity, the first transformer, and the first full-bridge rectifier bridge, with a base value for the load output voltage. The secondary power transfer of the converter is accomplished by the input power supply, the third switch S3, fourth switch S4, fifth switch S5, and sixth switch S6 on the second and third bridge arms, the PWM full-bridge structure, the second transformer, and the second full-bridge rectifier bridge, with the load output voltage range being able to be superimposed on the base voltage provided by the LLC resonant converter, with the voltage transferred by the PWM full-bridge converter superimposed on the base voltage provided by the LLC resonant converter. The PWM full-bridge converter adjusts the voltage gain by changing the phase shift angle or duty cycle, thereby expanding the overall gain range of the converter.

[0046] Specifically, in working mode 1, such as Figure 3 As shown, when the drains of the first switch S1 and the fourth switch S4 on the first and second bridge arms receive a high-level signal from the driving device, the drains and sources of the first switch S1 and the fourth switch S4 are turned on, the duty cycle of the first switch S1 and the fourth switch S4 is D1, and the input voltage V s The resonant capacitance C of the LLC resonant cavity is connected through the first switch S1, the fourth switch S4, and the first switch S4. r Resonant inductor L r Connected in phase, and then connected to the magnetizing inductor L in the primary winding of the first transformer. m1 After voltage transformation by the first transformer, the output is sent to the first full-bridge rectifier bridge. The first diode D1 and the fourth diode D4 in the first full-bridge rectifier bridge rectify the AC voltage transformed by the second transformer to obtain a DC voltage. Finally, the DC voltage is output to the load through the filter capacitor C1. The LLC resonant converter can adjust the switching frequency, causing the components of the resonant cavity to exhibit different impedance values. This allows adjustment of the voltage division between the magnetizing inductor in the first transformer and the load, thus achieving load voltage variation with a fixed input voltage and transformer turns ratio. Simultaneously, the gate of the fifth switch S5 on the third bridge arm receives a high-level signal from the driving device, and the drain and source of the fifth switch S5 are turned on, resulting in an input voltage V... s The leakage inductor L in the PWM full-bridge converter is connected via the fifth switch S5. k2 Then, it connects with the magnetizing inductance L in the primary winding of the second transformer. m2Connected to the first full-bridge rectifier bridge, after voltage transformation by the second transformer, the AC power is also converted to DC power by the first diode D1 and the fourth diode D4. Finally, it is output to the load via the filter capacitor C1. At this time, the output voltage is jointly affected by the LLC resonant converter and the PWM full-bridge converter. The PWM full-bridge converter changes the phase shift angle... Alternatively, the duty cycle D2 can be used to adjust the output voltage, thereby further expanding the overall gain range of the system compared to the LLC resonant converter. With the first transformer turns ratio N1 and the second transformer turns ratio N2, the output voltage V... o for:

[0047] V o =2D1N1V s +2D2N2V s (1)

[0048] Specifically, in working mode 2, such as Figure 4 As shown, when the drains of the second switch S2 and the third switch S3 on the first and second bridge arms receive a high-level signal from the driving device, the drains and sources of the second switch S2 and the third switch S3 are turned on, the duty cycle of the second switch S2 and the third switch S3 is D1, and the input voltage V s The resonant capacitance C of the LLC resonant cavity is connected through the second switch S2, the third switch S3, and the second switch S2. r Resonant inductor L r Connected in phase, and then connected to the magnetizing inductor L in the primary winding of the first transformer. m1 After voltage transformation by the first transformer, the output is sent to the first full-bridge rectifier bridge. The second diode D2 and the third diode D3 in the first full-bridge rectifier bridge rectify the AC voltage transformed by the second transformer to obtain a DC voltage. Finally, the DC voltage is output to the load via the filter capacitor C1. The LLC resonant converter can adjust the switching frequency, causing the components of the resonant cavity to present different impedance values. This allows adjustment of the voltage division between the first transformer's magnetizing inductance and the load, thus achieving load voltage variation with a fixed input voltage and transformer turns ratio. Simultaneously, the gate of the sixth switch S6 on the third bridge arm receives a high-level signal from the driving device, and the drain and source of the sixth switch S6 are turned on, resulting in an input voltage V. s The leakage inductor L in the PWM full-bridge converter is connected via the sixth switch S6. k2 Then, it connects with the magnetizing inductance L in the primary winding of the second transformer. m2Connected to the first full-bridge rectifier bridge, the AC power is converted to DC power by the second diode D2 and the third diode D3 after voltage transformation by the second transformer. Finally, the DC power is output to the load via the filter capacitor C1. At this time, the output voltage is jointly affected by the LLC resonant converter and the PWM full-bridge converter. The PWM full-bridge converter changes the phase shift angle... Alternatively, the output voltage can be adjusted by changing the duty cycle D2, thereby further expanding the overall gain range of the system compared to the LLC resonant converter. The output voltage in this case remains the same:

[0049] V o =2D1N1V s +2D2N2V s (2)

[0050] In summary, the wide-gain ZVS hybrid DC-DC converter based on dual transformers provided by this invention, under normal operating conditions, such as Figure 5 As shown, the first switch S1, fourth switch S4, and fifth switch S5 on the first, second, and third bridge arms alternately conduct with the second switch S2, third switch S3, and sixth switch S6, completing energy transfer from the input side to the output side. Under the action of the LLC resonant cavity and the PWM full-bridge converter, the six high-frequency switches on the wide-gain ZVS hybrid DC-DC converter based on dual transformers can achieve zero-voltage conduction across the entire range, reducing system switching losses and further improving system efficiency. With the combined action of the dual transmission channels of the LLC resonant converter and the PWM full-bridge converter, the system maintains high efficiency while expanding its wide gain range, overcoming the difficulty of selecting between high efficiency and wide gain in traditional LLC resonant converters.

[0051] This invention proposes a wide-gain ZVS hybrid DC-DC converter based on dual transformers, comprising an LLC resonant converter and a PWM full-bridge converter. This novel hybrid DC-DC converter is formed by the primary side of the LLC resonant converter and the secondary side of the PWM full-bridge converter sharing a single inverter arm and the secondary side sharing a single rectifier arm. Benefiting from the soft-switching characteristics of the LLC resonant converter and the PWM full-bridge converter, it can achieve zero-voltage turn-on across the entire load range. Compared to traditional LLC resonant converters or PWM full-bridge converters, the proposed wide-gain ZVS hybrid DC-DC converter based on dual transformers, due to the dual energy transmission channels of the LLC resonant converter and the PWM full-bridge converter, can simply and effectively achieve a wide-range gain for the converter. Furthermore, the soft-switching of the switching transistors across the entire load range improves system efficiency. Simultaneously, while ensuring high efficiency, the converter can also achieve a wide gain range. In summary, the hybrid DC-DC converter proposed in this invention can fully leverage the high efficiency of the LLC resonant converter and the wide output regulation capability of the PWM converter, achieving complementary advantages between the two converters.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A wide-gain ZVS hybrid DC-DC converter based on dual transformers, characterized in that, The system includes an LLC resonant converter and a PWM full-bridge converter. The LLC resonant converter includes a first full-bridge inverter, an LLC resonant cavity, a first transformer, and a first full-bridge rectifier. The PWM full-bridge converter includes a second full-bridge inverter, a second transformer, and a second full-bridge rectifier. The primary side of the LLC resonant converter and the PWM full-bridge converter share one inverter bridge arm, and the secondary side shares one rectifier bridge arm. In operation, the resonant cavity of the LLC resonant converter causes the inductor current to lag behind the voltage. The converter operates in the inductive region, enabling zero-voltage turn-on of the first switch S1, second switch S2, third switch S3, and fourth switch S4 on the first and second bridge arms. The PWM full-bridge converter enables zero-voltage turn-on of the fifth switch S5 and sixth switch S6 on the third bridge arm. The LLC resonant converter and the PWM full-bridge converter form a dual energy transmission channel. The LLC resonant converter is responsible for main power transmission, while the PWM full-bridge converter extends the wide gain range of the LLC resonant converter by adjusting the phase shift angle or duty cycle to control the voltage.

2. The wide-gain ZVS hybrid DC-DC converter based on dual transformers according to claim 1, characterized in that, The first full-bridge inverter in the LLC resonant converter includes four high-frequency switching transistors: a first switching transistor S1, a second switching transistor S2, a third switching transistor S3, and a fourth switching transistor S4. The source of the first switching transistor S1 and the drain of the second switching transistor S2 are connected to form the first bridge arm, and the source of the third switching transistor S3 and the drain of the fourth switching transistor S4 are connected to form the second bridge arm. The input voltage is connected to the drain of the first switching transistor S1, the drain of the third switching transistor S3, the source of the second switching transistor S2, and the source of the fourth switching transistor S4.

3. A wide-gain ZVS hybrid DC-DC converter based on dual transformers according to claim 2, characterized in that, The LLC resonant cavity includes a resonant capacitor, a resonant inductor, and a first transformer. The resonant capacitor is connected to the midpoint of the first bridge arm, and is connected to the midpoint of the second bridge arm via the resonant inductor and the primary winding of the first transformer.

4. A wide-gain ZVS hybrid DC-DC converter based on dual transformers according to claim 1, characterized in that, The first full-bridge rectifier bridge in the LLC resonant converter includes four uncontrolled diodes: a first diode D1, a second diode D2, a third diode D3, and a fourth diode D4. The midpoint of the bridge arm formed by the first diode D1 and the second diode D2 is connected to the secondary winding of the first transformer, and then connected to the midpoint of the bridge arm formed by the third diode D3 and the fourth diode D4 via the secondary winding of the first transformer.

5. A wide-gain ZVS hybrid DC-DC converter based on dual transformers according to claim 1, characterized in that, The second full-bridge inverter in the PWM full-bridge converter includes four high-frequency switching transistors and one leakage inductor. The four high-frequency switching transistors include a third switching transistor S3, a fourth switching transistor S4, a fifth switching transistor S5, and a sixth switching transistor S6. The source of the third switching transistor S3 and the drain of the fourth switching transistor S4 are connected to form the second bridge arm, and the source of the fifth switching transistor S5 and the drain of the sixth switching transistor S6 are connected to form the third bridge arm. The input voltage is connected to the drain of the third switching transistor S3, the drain of the fifth switching transistor S5, the source of the fourth switching transistor S4, and the source of the sixth switching transistor S6. The leakage inductor is connected to the midpoint of the second bridge arm and then connected to the midpoint of the third bridge arm via the primary winding of the second transformer.

6. A wide-gain ZVS hybrid DC-DC converter based on dual transformers according to claim 1, characterized in that, The second full-bridge rectifier bridge in the PWM full-bridge converter includes four uncontrolled diodes: a third diode D3, a fourth diode D4, a fifth diode D5, and a sixth diode D6. The midpoint of the bridge arm formed by the third diode D3 and the fourth diode D4 is connected to the secondary winding of the second transformer, and then connected to the midpoint of the bridge arm formed by the fifth diode D5 and the sixth diode D6 via the secondary winding of the second transformer.

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