Wide-gain ZVS hybrid DC converter based on double transformers

Abstract

The invention discloses a wide-gain ZVS hybrid direct-current converter based on double transformers, which belongs to the technical field of DC / DC direct-current converters and 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 primary side of the LLC resonant converter and the primary side of the PWM full-bridge converter share one inverter bridge arm, and the secondary side of the LLC resonant converter and the secondary side of the PWM full-bridge converter share one rectifier bridge arm. The hybrid direct-current converter provided by the invention can give full play to the advantages of high efficiency of the LLC resonant converter and wide output regulation capability of the PWM converter so as to realize advantage complementation of the two converters, so that when a converter system has a wide gain range, the loss of the system can be reduced, and the overall efficiency can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of DC / DC direct current converters, in particular to a wide-gain ZVS hybrid direct current converter based on dual transformers. Background Art

[0002] In recent years, LLC resonant converters with a wide gain range have become a hot topic in the research of DC / DC converters at home and abroad. When the traditional LLC resonant converter is in normal working state, the resonant current will lag the voltage, making the LLC work in the inductive area. The primary switch tube of the transformer can achieve zero voltage turn-on (ZVS) in the full range of load, and the secondary diode of the transformer can achieve zero current turn-off at low resonant frequency. The ZVS of the primary switch tube can reduce the switching loss of the system, so that the converter can have ideal efficiency at high switching frequency, thereby improving the power density of the overall converter.

[0003] Frequency conversion control (PFM) is one of the traditional control methods used by LLC resonant converters. By adjusting the switching frequency, the components of the resonant cavity present impedances of different values, and then the voltage division between the transformer excitation inductance and the load can be adjusted. When the input voltage and the transformer ratio are fixed, the load voltage can be changed. In traditional LLC resonant converters, in order to further widen the gain range, the ratio of the resonant inductance to the excitation inductance will be reduced. However, as the excitation inductance decreases, the circulating current on the primary side of the transformer will increase, which will increase the turn-off loss and conduction loss of the primary side switch tube, further affecting the overall efficiency of the system. Therefore, the wide gain range and high efficiency of LLC resonant converters are contradictory characteristics. Therefore, it is of great significance to study LLC resonant converters with both gain range and high efficiency.

[0004] In order to maintain the soft switching characteristics and high efficiency of LLC resonant converters while improving the gain range of the system, scholars have proposed many methods, one of which is to upgrade the topology structure, and the other is to optimize the control and modulation strategy. The existing technology can widen the wide gain range of LLC resonant converters, but it still brings problems such as high loss and low power density, which limits the application scope of the converter.

[0005] In general, the change of switching frequency in the traditional LLC resonant converter in variable frequency modulation (PFM) mode will cause the operating point to shift from the resonant point, causing the system to shift from the optimal working state of the converter. When the LLC resonant converter operates at a fixed frequency at the resonant frequency point, that is, it is in the DC transformer (DCX) state, although it can exert its optimal efficiency advantage, it does not have the output regulation capability and is difficult to meet the 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 converter based on dual transformers, which solves the problem of how to expand the wide gain range of the LLC resonant converter and reduce the circulating current, reduce the switching loss of the converter, and improve the system efficiency.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0008] A wide-gain ZVS hybrid DC converter based on dual transformers 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 an inverter bridge arm on the primary side and a rectifier bridge arm on the secondary side.

[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 switch tubes, namely, a first switch tube S1, a second switch tube S2, a third switch tube S3 and a fourth switch tube S4; the source of the first switch tube S1 and the drain of the second switch tube S2 are connected to form a first bridge arm, the source of the third switch tube S3 and the drain of the fourth switch tube S4 are connected to form a second bridge arm, and the input voltage is connected to the drain of the first switch tube S1, the drain of the third switch tube S3, the source of the second switch tube S2, and the source of the fourth switch tube 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, namely, a first diode D1, a second diode D2, a third diode D3, and a fourth diode D4; the midpoint of the bridge arm composed of the first diode D1 and the second diode D2 is connected to the secondary winding of the first transformer, and is connected to the midpoint of the bridge arm composed of the third diode D3 and the fourth diode D4 after passing through 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 tubes and a leakage inductor, and the four high-frequency switching tubes include a third switching tube S3, a fourth switching tube S4, a fifth switching tube S5 and a sixth switching tube S6; the source of the third switching tube S3 and the drain of the fourth switching tube S4 are connected to form a second bridge arm, the source of the fifth switching tube S5 and the drain of the sixth switching tube S6 are connected to form a third bridge arm, and the input voltage is connected to the drain of the third switching tube S3, the drain of the fifth switching tube S5, and the source of the fourth switching tube S4 and the source of the sixth switching tube S6; the leakage inductor is connected to the midpoint of the second bridge arm, and is connected to the midpoint of the third bridge arm after passing through 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, namely 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 is connected to the midpoint of the bridge arm formed by the fifth diode D5 and the sixth diode D6 through 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 converter is in working state, the resonant cavity of the LLC resonant converter causes the inductor current to lag behind the voltage, and the LLC resonant converter operates in the inductive region, which can achieve zero-voltage turn-on of the first switch tube S1, the second switch tube S2, the third switch tube S3 and the fourth switch tube S4 on the first bridge arm and the second bridge arm, and the PWM full-bridge converter achieves zero-voltage turn-on of the fifth switch tube S5 and the sixth switch tube S6 on the third bridge arm.

[0015] Due to the adoption of the above technical solution, the technical progress achieved by the present invention is:

[0016] 1. The wide-gain ZVS hybrid DC converter based on dual transformers proposed in the present invention is composed of three bridge arms formed by parallel connection of the LLC resonant converter and the primary side of the PWM full-bridge converter and the secondary side of the dual transformers connected in series with the rectifier bridge. Thanks to the soft switching characteristics of the LLC resonant converter and the PWM full-bridge converter, zero voltage switching can be achieved in the full range of loads.

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

[0018] 3. The hybrid DC converter proposed in the present invention can give full play to 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work.

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

[0021] Figure 2 1 is a circuit diagram of a wide-gain ZVS hybrid DC converter system based on dual transformers proposed in an embodiment of the present invention;

[0022] Figure 3 It is a circuit diagram of a wide-gain ZVS hybrid DC converter operating mode 1 based on dual transformers proposed in an embodiment of the present invention;

[0023] Figure 4 It is a circuit diagram of a wide-gain ZVS hybrid DC converter operating mode 2 based on dual transformers proposed in an embodiment of the present invention;

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

[0025] It should be noted that the terms "including" and "having" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or apparatus.

[0026] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0027] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "several" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0028] The present invention is 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 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 LLC resonant converter and the PWM full-bridge converter share an inverter bridge arm on the primary side and a rectifier bridge arm on the secondary side.

[0030] Specifically, Figure 2 As shown, the first full-bridge inverter in the LLC resonant converter includes four high-frequency switch tubes, namely, a first switch tube S1, a second switch tube S2, a third switch tube S3 and a fourth switch tube S4; the source of the first switch tube S1 and the drain of the second switch tube S2 are connected to form a first bridge arm, the source of the third switch tube S3 and the drain of the fourth switch tube S4 are connected to form a second bridge arm, and the input voltage is connected to the drain of the first switch tube S1, the drain of the third switch tube S3, the source of the second switch tube S2, and the source of the fourth switch tube 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 in the LLC resonant converter includes four uncontrolled diodes, namely, 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 is connected to the midpoint of the bridge arm formed by the third diode D3 and the fourth diode D4 through 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 tubes and a leakage inductor. The four high-frequency switching tubes include a third switching tube S3, a fourth switching tube S4, a fifth switching tube S5 and a sixth switching tube S6; the source of the third switching tube S3 and the drain of the fourth switching tube S4 are connected to form a second bridge arm, the source of the fifth switching tube S5 and the drain of the sixth switching tube S6 are connected to form a third bridge arm, and the input voltage is connected to the drain of the third switching tube S3, the drain of the fifth switching tube S5, the source of the fourth switching tube S4, and the source of the sixth switching tube S6; the leakage inductor is connected to the midpoint of the second bridge arm, and is connected to the midpoint of the third bridge arm after passing through the primary winding of the second transformer.

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

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

[0037] The first full-bridge rectifier in the LLC resonant converter and the second full-bridge rectifier in the PWM full-bridge converter in the present invention 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 in parallel with a filter capacitor, that is, the LLC resonant converter and the PWM full-bridge converter share a rectifier bridge arm.

[0038] The wide gain ZVS hybrid DC converter based on dual transformers provided by the present invention, under normal working conditions, the LLC resonant converter load is mainly for power transmission, and the PWM full-bridge converter is responsible for the transmission of the remaining power. Therefore, in this mode, the switching frequency of the LLC resonant converter remains unchanged, the switching frequency is approximately the resonant frequency, the gain of the LLC resonant converter is close to 1, and the PWM full-bridge converter is responsible for regulating the voltage, thereby expanding the wide gain range of the LLC resonant converter. Specifically, under working conditions, the LLC resonant converter resonant cavity causes the inductor current to lag behind the voltage, and the LLC resonant converter operates in the inductive region, which can realize the zero voltage switching (ZVS) of the first switch tube S1, the second switch tube S2, the third switch tube S3 and the fourth switch tube S4 on the first bridge arm and the second bridge arm, and the PWM full-bridge converter realizes the zero voltage switching (ZVS) of the fifth switch tube S5 and the sixth switch tube S6 on the third bridge arm.

[0039] Specifically, in working mode 1, if Figure 3 As shown, when the gates of the first switch tube S1, the fourth switch tube S4, and the fifth switch tube S5 high-frequency switch tubes on 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 first switch tube S1, the fourth switch tube S4, and the fifth switch tube S5 are turned on, and the input voltage V s Through the first switch tube S1, the fourth switch tube S4 and the resonant capacitor C of the LLC resonant cavity r , resonant inductor L r connected, and then connected to the excitation inductor L in the first transformer m1 After the voltage is transformed by the first transformer, it is output 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 by the filter capacitor C1. At the same time, the input voltage V s The leakage inductance L in the PWM full-bridge converter is also connected through the fifth switch tube S5. k2 , and then with the excitation inductance L in the second transformer m2 The two sides of the LLC resonant converter and the PWM full-bridge converter are connected, and after the voltage is converted by the second transformer, the first diode D1 and the fourth diode D4 in the first full-bridge rectifier bridge convert the AC power into DC power, which is output to the load by the filter capacitor C1, thereby performing energy transmission. In this way, after forming a primary-secondary side integrated structure, the LLC resonant converter and the PWM full-bridge converter jointly realize the energy transmission between the primary input voltage and the output load.

[0040] Specifically, in working mode 2, if Figure 4As shown, when the gates of the second switch tube S2, the third switch tube S3, and the sixth switch tube 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 tube S2, the third switch tube S3, and the sixth switch tube S6 are turned on, and the input voltage V s Through the resonant capacitor C of the second switch tube S2, the third switch tube S3 and the LLC resonant cavity r , resonant inductor L r connected, and then connected to the excitation inductor L in the primary side of the first transformer m1 After the voltage is converted by the first transformer, it is output 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 converted by the second transformer to obtain a DC voltage, which is finally output to the load by the filter capacitor C1. At the same time, the input voltage is also connected to the leakage inductance L in the PWM full-bridge converter through the sixth switch tube S6. k2 , and then with the excitation inductance L in the primary side of the second transformer m2 The two sides of the LLC resonant converter and the PWM full-bridge converter are connected, and after the voltage is converted by the second transformer, the second diode D2 and the third diode D3 in the first full-bridge rectifier bridge convert the AC power into DC power, and finally output it to the load through the filter capacitor C1, so as to perform energy transmission. In this way, after forming a primary-secondary side integrated structure, the LLC resonant converter and the PWM full-bridge converter also jointly realize the energy transmission between the primary input voltage and the output load.

[0041] The advantages of the present invention are two major features:

[0042] (1) The advantage of the LLC resonant converter and the PWM full-bridge converter is that they can achieve zero-voltage turn-on of the first switch S1 to the sixth switch S6 on the first bridge arm, the second bridge arm and the third bridge arm over the entire load range. Zero-voltage turn-on of the switch means reduced turn-on loss, which can improve the overall efficiency of the system.

[0043] Specifically, in order to achieve zero voltage conduction of 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 inductor L r This will cause the parasitic capacitance C of the first switch tube S1 and the fourth switch tube S4 to s1 , C s4The discharge is zero, so that the voltage across the drain-source of the first switch tube S1 and the fourth switch tube S4 is zero. Under this condition, the gates of the first switch tube S1 and the fourth switch tube S4 receive the high-level signal from the driver and complete the zero-voltage turn-on. Similarly, after the first switch tube S1 and the fourth switch tube S4 are turned off and before the second switch tube S2 and the third switch tube S3 are turned on, the resonant capacitor C in the LLC resonant cavity r and resonant inductor L r This will cause the parasitic capacitance C of the second switch tube S2 and the third switch tube S3 to s2 , C s3 The discharge is zero, so that the voltage across the drain and source of the second switch tube S2 and the third switch tube S3 is zero. Under this condition, the gates of the second switch tube S2 and the third switch tube S3 receive the high-level signal from the driving device and complete zero-voltage switching.

[0044] At the same time, after the sixth switch tube S6 is turned off and before the fifth switch tube S5 is turned on, the leakage inductance L of the second transformer in the PWM full-bridge converter k2 The parasitic capacitance C of the fifth switch tube S5 will be s5 The discharge makes the voltage between the drain and source of the fifth switch tube S5 zero. When the gate of the fifth switch tube S5 receives a high-level signal from the driving device, the fifth switch tube S5 reaches the zero-voltage turn-on condition and can successfully achieve zero-voltage turn-on. Similarly, after the fifth switch tube S5 is turned off and before the sixth switch tube S6 is turned on, the leakage inductance L in the PWM full-bridge converter k2 The parasitic capacitance C of the sixth switch tube S6 will be s6 Discharging makes the voltage between the drain and source of the sixth switch tube S6 zero. When the gate of the sixth switch tube S6 receives a high level signal from the driving device, the sixth switch tube S6 reaches the zero voltage turn-on condition and can successfully achieve zero voltage turn-on.

[0045] (2) In order to achieve high efficiency of the overall converter and a wide gain range, the converter can perform the following two working modes: the main power transmission of the converter is completed by the input power supply, the first switch tube S1, the second switch tube S2, the third switch tube S3 and the fourth switch tube S4 high-frequency switch tubes on the first bridge arm and the second bridge arm, the LLC resonant cavity, the first transformer and the first full-bridge rectifier bridge, and the load output voltage has a basic value. The auxiliary power transmission of the converter is completed by the input power supply, the third switch tube S3, the fourth switch tube S4, the fifth switch tube S5 and the sixth switch tube S6 on the second bridge arm and the third bridge arm, the PWM full-bridge structure, the second transformer and the second full-bridge rectifier bridge, and the load output voltage range can be superimposed on the basic voltage brought by the LLC resonant converter. The PWM full-bridge converter adjusts the voltage gain by changing the phase shift angle or duty cycle, so that the overall gain range of the converter is expanded.

[0046] Specifically, in working mode 1, if Figure 3 As shown, when the drains of the first switch tube S1 and the fourth switch tube S4 on the first bridge arm and the second bridge arm receive a high level signal from the driving device, the drain and source of the first switch tube S1 and the fourth switch tube S4 are turned on, the duty cycle of the first switch tube S1 and the fourth switch tube S4 is D1, and the input voltage V s Through the first switch tube S1, the fourth switch tube S4 and the resonant capacitor C of the LLC resonant cavity r , resonant inductor L r connected, and then connected to the excitation inductor L in the primary side of the first transformer m1 , after voltage conversion by the first transformer, it is output to the first full-bridge rectifier bridge, and the first diode D1 and the fourth diode D4 in the first full-bridge rectifier bridge rectify the AC voltage converted by the second transformer to obtain a DC voltage, which is finally output to the load by the filter capacitor C1. The LLC resonant converter can adjust the switching frequency so that the components of the resonant cavity present impedances of different values, thereby adjusting the voltage division between the excitation inductance in the first transformer and the load, and realizing the change of the load voltage when the input voltage and the transformer ratio are fixed. At the same time, the gate of the fifth switch tube S5 on the third bridge arm receives a high-level signal from the driving device, and the drain and source of the fifth switch tube S5 are turned on, and the input voltage V s The fifth switch tube S5 is connected to the leakage inductance L in the PWM full-bridge converter. k2 , and then with the excitation inductance L in the primary side of the second transformer m2After the voltage is converted by the second transformer, the first diode D1 and the fourth diode D4 in the first full-bridge rectifier bridge convert the AC power into DC power, and finally output it to the load through 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 Or duty cycle D2 to adjust the output voltage, so that the overall gain range of the system is further expanded on the basis of LLC resonant converter. When the first transformer ratio is N1 and the second transformer ratio is N2, the output voltage V o for:

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

[0048] Specifically, in working mode 2, if Figure 4 As shown, when the drains of the second switch tube S2 and the third switch tube S3 on the first bridge arm and the second bridge arm receive a high level signal from the driving device, the drain and source of the second switch tube S2 and the third switch tube S3 are turned on, the duty cycle of the second switch tube S2 and the third switch tube S3 is D1, and the input voltage V s Through the resonant capacitor C of the second switch tube S2, the third switch tube S3 and the LLC resonant cavity r , resonant inductor L r connected, and then connected to the excitation inductor L in the primary side of the first transformer m1 , after voltage conversion by the first transformer, it is output to the first full-bridge rectifier bridge, and the second diode D2 and the third diode D3 in the first full-bridge rectifier bridge rectify the AC voltage converted by the second transformer to obtain a DC voltage, which is finally output to the load via the filter capacitor C1. The LLC resonant converter can adjust the switching frequency so that the components of the resonant cavity present impedances of different values, thereby adjusting the voltage division between the excitation inductance of the first transformer and the load, and realizing the change of the load voltage when the input voltage and the transformer ratio are fixed. At the same time, the gate of the sixth switch tube S6 on the third bridge arm receives a high-level signal from the driving device, and the drain and source of the sixth switch tube S6 are turned on, and the input voltage V s The leakage inductance L in the PWM full-bridge converter is connected through the sixth switch tube S6. k2 , and then with the excitation inductance L in the primary side of the second transformer m2After the voltage is converted by the second transformer, the second diode D2 and the third diode D3 in the first full-bridge rectifier bridge convert the AC power into DC power, and finally output it to the load through 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 Or the duty cycle D2 is used to adjust the output voltage, so that the overall gain range of the system is further expanded on the basis of the LLC resonant converter. At this time, the output voltage is also:

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

[0050] In summary, the wide gain ZVS hybrid DC converter based on dual transformers provided by the present invention, in normal operation, Figure 5 As shown, the first switch tube S1, the fourth switch tube S4 and the fifth switch tube S5 on the first bridge arm, the second bridge arm and the third bridge arm are alternately turned on with the second switch tube S2, the third switch tube S3 and the sixth switch tube S6 to complete the energy transmission 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 switch tubes on the wide-gain ZVS hybrid DC converter based on the dual transformer can achieve zero voltage conduction in the full range, reduce the switching loss of the system, and further improve the efficiency of the system. Under the joint action of the LLC resonant converter and the PWM full-bridge converter dual transmission channels, the system can maintain a high efficiency while expanding the wide gain range of the system, overcoming the difficulty of the traditional LLC resonant converter in choosing between high efficiency and wide range gain.

[0051] A wide-gain ZVS hybrid DC converter based on dual transformers proposed in the present invention includes an LLC resonant converter and a PWM full-bridge converter. The novel hybrid DC converter is formed by mixing the LLC resonant converter and the PWM full-bridge converter, which share an inverter bridge arm on the primary side and a rectifier bridge arm on the secondary side. Thanks to the soft switching characteristics of the LLC resonant converter and the PWM full-bridge converter, zero voltage switching in the full load range can be achieved. Compared with the traditional LLC resonant converter or PWM full-bridge converter, the proposed wide-gain ZVS hybrid DC converter based on dual transformers can simply and effectively achieve a wide range of converter gain due to the dual energy transmission channels of the LLC resonant converter and the PWM full-bridge converter. In addition, the soft switching of the switch tube in the full load range can improve the efficiency of the system. At the same time, while ensuring high efficiency, the converter can also achieve a wide gain range. In general, the hybrid DC converter proposed in the present invention can give full play to the advantages of the high efficiency of the LLC resonant converter and the wide output regulation capability of the PWM converter to achieve complementary advantages of 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, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements 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 converter based on dual transformers, characterized in that: It 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 an inverter bridge arm on the primary side and a rectifier bridge arm on the secondary side.

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

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

5. The wide gain ZVS hybrid 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 tubes and a leakage inductor. The four high-frequency switching tubes include a third switching tube S3, a fourth switching tube S4, a fifth switching tube S5 and a sixth switching tube S6; the source of the third switching tube S3 and the drain of the fourth switching tube S4 are connected to form a second bridge arm, the source of the fifth switching tube S5 and the drain of the sixth switching tube S6 are connected to form a third bridge arm, and the input voltage is connected to the drain of the third switching tube S3, the drain of the fifth switching tube S5, the source of the fourth switching tube S4, and the source of the sixth switching tube S6; the leakage inductor is connected to the midpoint of the second bridge arm, and is connected to the midpoint of the third bridge arm after passing through the primary winding of the second transformer.

6. The wide gain ZVS hybrid 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, namely 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 is connected to the midpoint of the bridge arm formed by the fifth diode D5 and the sixth diode D6 after passing through the secondary winding of the second transformer.

7. A dual-transformer based wide gain ZVS hybrid DC converter according to any one of claims 1 to 6, characterized in that: When the hybrid DC converter is in working state, the LLC resonant converter resonant cavity causes the inductor current to lag behind the voltage, and the LLC resonant converter operates in the inductive region, and can achieve zero-voltage switching of the first switch tube S1, the second switch tube S2, the third switch tube S3 and the fourth switch tube S4 on the first bridge arm and the second bridge arm, and the PWM full-bridge converter achieves zero-voltage switching of the fifth switch tube S5 and the sixth switch tube S6 on the third bridge arm.

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