A DC converter topology with adjustable output voltage over a wide input range

Abstract

The present invention discloses a DC converter topology with adjustable output voltage within a wide input range, which belongs to the technical field of DC-DC converter topology structures, and specifically includes two transmission paths for transferring energy from an input port to an output port. The main channel is a DCX based on LLC. The auxiliary channel includes two stages, the first stage adopts a non-isolated PWM DC converter, and then a small DCX based on LLC is cascaded with it to achieve efficient isolation conversion, and the output voltage is adjusted by adjusting the PWM DC converter. The main channel and the auxiliary channel are connected in series at the input port and in parallel at the output port. The present invention performs triangular wave current mode (TCM) modulation on the PWM converter to achieve zero voltage opening of its switch tube, which significantly reduces the switching loss of the energy transmission auxiliary channel. Therefore, the proposed converter topology can achieve high transmission efficiency within a wide input voltage range.

Description

Technical Field

[0001] The present invention belongs to the technical field of DC-DC converter topology structures, and more specifically, relates to a DC converter topology structure with adjustable output voltage within a wide input range. Background Art

[0002] Information technology has flourished in recent decades. With the growing demand for large-scale information storage and computing, the size of data centers has also increased dramatically. As a result, more and more servers are installed in data centers. This leads to huge energy consumption and electricity costs. In order to reduce energy loss and improve space utilization, it is necessary to achieve high efficiency and high power density in the energy conversion stage.

[0003] In practical applications, no matter what kind of power distribution system, once the grid is disconnected, the battery voltage will float in a large range due to discharge, which causes the output voltage of the DCX (direct current converter) to no longer maintain a constant value. Therefore, a high-efficiency isolated DC-DC converter with wide input voltage range regulation capability is required.

[0004] In addition to efficiency and wide input regulation capability, high frequency and high power density are also development trends, because high switching frequency can improve electromagnetic interference performance and high power density can improve space utilization. In order to achieve high efficiency of isolated DC-DC converters, predecessors have done a lot of work. The traditional hard-switching pulse width modulation circuit has a simple structure and the control scheme is widely used in the industrial field, but for high switching frequencies, it will produce large switching losses. The phase-shifted full-bridge converter (PSFB) is very popular in medium-power applications due to its zero-voltage turn-on of the primary switch tube. However, due to the large turn-off current of the primary switch tube and the lack of zero-current turn-off of the secondary rectifier, the PSFB is not suitable for applications with high switching frequency and wide input range. The dual active bridge (DAB) converter has been widely used in energy storage systems due to its simple design and control. However, DAB has large turn-off losses and large circulating currents, so DAB is not suitable for applications with high switching frequency and wide input range.

[0005] Among various converters that provide zero voltage switching (ZVS), the LLC converter provides zero voltage turn-on of the primary switch tube and zero current turn-off of the secondary rectifier. It is widely used in applications that require electrical isolation and high efficiency, and is a potential candidate topology for achieving high efficiency at high switching frequencies. However, the LLC converter adjusts the output by adjusting the phase shift angle, switching frequency, or duty cycle. These methods require a large resonant inductor to adjust the output, which not only occupies a large volume, but also generates large losses. On the other hand, it is difficult to obtain an effective control strategy for high-frequency regulation LLC converters with phase shift modulation or frequency modulation. Synchronous rectification logic is also difficult to implement. These shortcomings are more obvious for an LLC resonant converter with a wide input range.

[0006] In order to expand the gain range of LLC resonant converters, different methods have been proposed in the literature. For example, researchers have proposed a dual-bridge LLC resonant converter with PWM control in which DCX works at a fixed switching frequency. However, since the output voltage is adjusted by the duty cycle, it is still difficult to implement synchronous rectification logic under high switching conditions. There are also documents that propose a dual half-bridge series LLC converter. In this topology, frequency adaptive phase shift modulation (FAPSM) control is implemented. A wide range of gain can be obtained by adjusting the phase shift angle of the primary and secondary switch tubes. However, the phase shift modulation method will generate circulating energy at high switching frequencies, resulting in reduced efficiency.

[0007] The LLC resonant converter provides the best performance at the series resonant frequency. It can achieve zero voltage turn-on, low current turn-off and zero current turn-off of the secondary rectifier, which helps to achieve high efficiency and high power density. In addition, the rectifier on the secondary side can be driven using the drive signal of the primary switch tube, which greatly simplifies the synchronization logic. However, since the voltage ratio of DCX is fixed, auxiliary circuits are required to regulate the output. The traditional solution uses cascaded non-isolated PWM regulators for output regulation. However, since the PWM converter is subjected to full input or full output voltage and current, there is a problem of high switching losses. In addition, the full-load regulator is large in size, resulting in reduced power density.

[0008] Therefore, for the high-efficiency and high-power-density LLC resonant converter with DCX operating at a fixed switching frequency and having wide input voltage range regulation capability, it is necessary to further optimize its topology structure and the modulation method of the PWM converter therein to improve its power density and efficiency. Summary of the invention

[0009] In view of the defects of the prior art, the purpose of the present invention is to provide a DC converter topology with adjustable output voltage within a wide input range, aiming to solve the technical problems that urgently need to be solved, such as the LLC resonant converter under existing high-frequency working conditions having insufficient power density, insufficient efficiency, insufficient adjustment capability within a wide input voltage range, complex control strategy and difficult to implement synchronous rectification control logic due to its topological structure.

[0010] To achieve the above objectives, the present invention provides a DC converter topology with adjustable output voltage within a wide input range, including two transmission paths for transferring energy from an input port to an output port: a main channel and an auxiliary channel, wherein the input ports of the main channel and the auxiliary channel are connected in series, and the output ports are connected in parallel.

[0011] Among them, the main channel is an LLC-based DCX, which operates at a fixed switching frequency and transfers most of the input energy to the output port;

[0012] The auxiliary channel consists of two stages to process the regulated portion of the input energy. The first stage uses a non-isolated PWM DC-DC converter, and the second stage uses a small LLC-based DCX to achieve efficient isolated conversion. The non-isolated PWM DC-DC converter is cascaded with the small DCX on the primary side of the DCX transformer. The output voltage is regulated by adjusting the non-isolated PWM DC-DC converter of the auxiliary channel.

[0013] The beneficial effects of the present invention are as follows: since the output voltage of the topology is regulated by a non-isolated PWM converter, the LLC-based DCXs are only used for isolation and voltage reduction. Voltage regulation is achieved at a fixed switching frequency, so the structure simplifies the control strategy and synchronous rectification logic and is suitable for applications with a wide input range. In addition, the partial power regulation structure helps to reduce power loss.

[0014] Based on the above technical solution, the present invention can also be improved as follows.

[0015] Furthermore, the DCX used in the main energy transmission channel and the DCX used in the auxiliary energy transmission channel both operate at the series resonance frequency of their respective resonant cavities.

[0016] Furthermore, the switching frequency of the PWM converter used by the energy transfer auxiliary channel is independent of the two DCXs.

[0017] A further beneficial effect of the present invention is that the DCXs of the main energy transmission channel and the auxiliary channel can obtain a stable transformation ratio, retaining the advantages of high efficiency and high power density of the LLC resonant converter, and no additional control of the DCXs is required, and only the PWM converter needs to be controlled to adjust the output voltage.

[0018] Furthermore, the DCX used in the main energy transmission channel and the DCX used in the auxiliary energy transmission channel are designed with appropriate resonant cavity parameters to operate at the same series resonant frequency and duty cycle.

[0019] Furthermore, the main channel includes a PWM DC-DC converter, a first filter capacitor C in1 , the second filter capacitor C in2 , the first switch tube Q1, the second switch tube Q2, the first resonant inductor L r1 and the first resonant capacitor C r1 The first resonant cavity formed; the first filter capacitor C in1 Connected in parallel to the input of the PWM converter, the second filter capacitor C in2 The output of the PWM converter is connected in parallel to the output of the PWM converter, the output of the PWM converter is applied to the bridge arm formed by the first switch tube Q1 and the second switch tube Q2, and the output at the midpoint of the bridge arm is applied to the first resonant cavity;

[0020] The auxiliary channel includes a third filter capacitor C in3 , the third switch tube Q3, the fourth switch tube Q4, the second resonant inductor L r2 and the second resonant capacitor C r2 The second resonant cavity formed; the third filter capacitor C in3 It is connected in parallel to the bridge arm formed by the third switch tube Q3 and the fourth switch tube Q4, and the output at the midpoint of the bridge arm is applied to the second resonant cavity;

[0021] The main channel and the auxiliary channel share a common excitation inductor L m The center-tapped transformer T and the synchronous rectifier composed of the first synchronous rectifier switch tube S1 and the second rectifier switch tube S2; the outputs of the first resonant cavity and the second resonant cavity are applied to the input side of the center-tapped transformer T, and the output side of the transformer T is connected to the synchronous rectifier. That is, the transformers of the DCXs of the two energy transmission paths can be merged, that is, the secondary windings of the DCXs transformers are connected in parallel and share the same set of synchronous rectifier switches, thereby realizing the integration of the transformers of the two DCXs into a three-port transformer consisting of two input ports and one output port.

[0022] A further beneficial effect of the present invention is that the topological structure of the circuit is greatly simplified, and a single transformer helps to improve the power density.

[0023] Furthermore, the PWM converter of the topology structure adopts a triangle current mode (TCM) modulation method.

[0024] A further beneficial effect of the present invention is that the zero-voltage turn-on of the switch tube in the PWM converter is achieved. During the maintenance time, when the input voltage changes, the energy flowing through the auxiliary energy transmission channel where the PWM converter is located increases. Since the switching loss of the PWM converter is greatly reduced under TCM, the overall efficiency of the converter can be improved within a wide input voltage range.

[0025] Furthermore, the primary switch tube of the topological structure adopts a gallium nitride device.

[0026] A further beneficial effect of the present invention is that the turn-off loss of the primary switch tube is greatly reduced.

[0027] Furthermore, the synchronous rectifier of the topological structure adopts silicon devices.

[0028] A further beneficial effect of the present invention is that the conduction loss of the secondary rectifier bridge under high output current conditions is greatly reduced.

[0029] Furthermore, the driving signal of the synchronous rectifier of the topological structure is synchronized with the driving signal of the primary switch tube and has a fixed frequency and duty cycle.

[0030] Through the above technical solutions conceived by the present invention, compared with the prior art, the DCXs of the main channel and the auxiliary channel in the present invention always operate at the resonant frequency of their respective resonant cavities, ensuring the highest energy transmission efficiency of the DCXs, while simplifying the control logic of the synchronous rectification. The PWM converter in the auxiliary channel operates in the TCM mode, realizing the zero voltage turn-on of the switch tube, and when adjusting the working state of the PWM converter to adjust the output voltage, it is ensured that most of the energy is transmitted through the main channel with higher energy transmission efficiency, achieving higher efficiency. The main channel and the auxiliary channel share the secondary winding and synchronous rectifier of the transformer, saving a lot of space, reducing the size of the equipment, and improving the power density of the converter. Therefore, the proposed converter topology achieves high efficiency and high power density. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a brief schematic diagram of the original topological structure of the DC converter proposed in the present invention;

[0032] Figure 2 Schematic diagram of the circuit topology of the DC converter proposed in the present invention;

[0033] Figure 3 It is the main waveform of the topological structure of the DC converter proposed in the present invention under steady-state operation;

[0034] Figure 4 It is an equivalent circuit diagram of each stage in a cycle of the DC converter proposed in the present invention when in steady state;

[0035] Figure 5 Schematic diagram of the circuit topology of the DC converter provided by an embodiment of the present invention;

[0036] Figure 6 It is a schematic diagram of an equivalent circuit of a boost converter in a DC converter provided in an embodiment of the present invention and main waveforms in steady-state operation. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0038] The present invention provides a DC converter topology structure with adjustable output voltage within a wide input range, comprising two transmission paths for transferring energy from an input port to an output port: a main channel and an auxiliary channel, wherein the input ports of the main channel and the auxiliary channel are connected in series and the output ports are connected in parallel.

[0039] Among them, the main channel is an LLC-based DCX, which operates at a fixed switching frequency and transfers most of the input energy to the output port;

[0040] The auxiliary channel consists of two stages to process the regulated portion of the input energy. The first stage uses a non-isolated PWM DC-DC converter, and the second stage uses a small LLC-based DCX to achieve efficient isolated conversion. The non-isolated PWM DC-DC converter is cascaded with the small DCX on the primary side of the DCX transformer. The output voltage is regulated by adjusting the non-isolated PWM DC-DC converter of the auxiliary channel.

[0041] Figure 1It is a brief schematic diagram of the original topological structure of the DC converter proposed in the present invention. In this topological structure, the process of transferring energy from the input port to the output port can be divided into two transmission paths, and these two paths are respectively called the main channel and the auxiliary channel as channels for energy transfer. Among them, the main channel transfers most of the input energy to the output port, and the main channel is composed of only one DC converter working at a fixed switching frequency to form DCX. Specifically, the main channel of energy transmission is composed of a single LLC resonant converter working at a fixed switching frequency, which converts the input DC voltage into the output DC voltage and undertakes most of the work of the converter to transmit energy. The auxiliary channel is only responsible for transferring most of the input energy to the output port in terms of energy transmission, but it also undertakes the task of regulating the output voltage. Specifically, the auxiliary channel includes two stages in total, and the first stage is a non-isolated PWM DC-DC converter, such as a Buck converter, a Boost converter, etc. The non-isolated PWM DC-DC converter also needs to cascade a small DCX in the auxiliary channel, specifically, it is also an LLC resonant converter working at a fixed switching frequency, and the non-isolated PWM DC-DC converter is used to process the regulated part of the input energy. In addition, the input ports of the main channel and the auxiliary channel are connected in series, and the output ports are connected in parallel.

[0042] exist Figure 1 In, V in is the input voltage of the proposed DC converter. Since the main path and the auxiliary path of energy transmission are connected in parallel to form the DC converter, the sum of the input voltages of the main path and the auxiliary path of energy transmission is V in ; Since the main path and the auxiliary path of energy transmission are connected in parallel at the output port, the output voltages of the main path and the auxiliary path of energy transmission are both V o DCX1 is a DC-DC converter based on LLC resonant converter on the auxiliary path of energy transmission. The transformer of DCX1 is T1, and its turn ratio is m:1. The primary side of transformer T1, DCX1 is cascaded with a non-isolated PWM converter, which can be a Buck converter or a Boost converter, etc.; DCX2 is a DC-DC converter based on LLC resonant converter on the main path of energy transmission. The transformer of DCX2 is T2, and its turn ratio is n:1. R L is the output voltage V o The load being powered.

[0043] When the resonant frequencies of DCX1 and DCX2 are the same, the rectifiers of the two DCXs and the secondary windings of the transformers can be combined into one: the secondary windings of the transformers T1 and T2 are connected in parallel. Therefore, the two transformers can be integrated into one transformer and can share the same set of synchronous rectification devices.

[0044] Figure 2The circuit topology diagram of the DC converter proposed in the present invention is shown in FIG. S1 and S2 are the secondary synchronous rectifier switch tubes of the proposed DC converter. Through the appropriate resonant cavity parameter design, the resonant frequency of DCX1 and DCX2 is made the same. The secondary synchronous rectifiers of the two DCXs are integrated into a set of rectifiers composed of S1 and S2. In the circuit topology of the proposed DC converter, the transformer T of DCX is integrated from T1 and T2, which greatly improves the power density of the proposed DC converter. The transformer T has three windings, N A is the primary winding of DCX1 in the three-winding transformer, N P is the primary winding of DCX2 in the three-winding transformer, and the secondary winding of transformer T has N turns. s The secondary winding of the center-tapped transformer has a turn ratio of m:n:1. Q1 and Q2 together form the bridge arm of the DCX1 transformer primary side to generate the input square wave voltage. Q1 is the upper switch tube of the bridge arm, Q2 is the lower switch tube of the bridge arm, and L r1 is the resonant inductance of DCX1, C r1 is the resonant capacitor of DCX1, L m is the magnetizing inductance of the three-winding transformer of the proposed converter; Q3 and Q4 together form the bridge arm of the transformer primary side in DCX2 to generate the input square wave voltage, Q3 is the upper switch tube of the bridge arm, Q 42 is the lower switch tube of the bridge arm, L r2 is the resonant inductance of DCX2, C r2 is the resonant capacitor of DCX2; V0 is the input voltage of the auxiliary path of energy transmission, V1 is the output voltage of the PWM converter of the auxiliary path of energy transmission, V2 is the input voltage of the main path of energy transmission, C in1 It is the capacitor used for input voltage regulation and filtering of the auxiliary path of energy transmission, C in2 It is the capacitor used for output voltage regulation and filtering of the PWM converter in the auxiliary path of energy transmission, C in3 It is the capacitor used for input voltage regulation and filtering in the main path of energy transmission, C o is the output voltage stabilization and filtering capacitor of the proposed DC converter; the output voltage of the main path and the auxiliary path of energy transmission are connected in parallel, which is the same as the output voltage of the proposed DC converter, both of which are V o , R L is the load resistance of the proposed converter.

[0045] exist Figure 2In the non-isolated PWM converter, the switching frequency and the two DCXs are independent. By changing the duty cycle of the PWM converter, the ability to adjust the output voltage within a wide input voltage range can be achieved. By making the two bridge arms work at the same switching frequency, and the switching frequency is the series resonant frequency of DCX1 and DCX2, the LLC resonant converter can make the primary switch tube turn on with zero voltage, turn off with low voltage, and the secondary rectifier turn off with zero current when the switching frequency and the series resonant frequency of the resonant cavity are equal. Therefore, DCX1 and DCX2 can obtain the best performance, that is, high efficiency and high power density, and the driving signals required by the primary switch tubes and secondary rectifiers of DCX1 and DCX2 are completely consistent, which greatly simplifies the control strategy and the control logic of synchronous rectification.

[0046] Figure 3 The main waveforms of the proposed DC converter topology under steady-state operation are: Figure 4 (a), (b), and (c) are Figure 3 The equivalent circuit diagram corresponding to the time periods t0~t1, t1~t2, and t2~t3 is as follows: Figure 4 Medium V gs_Q1 With V gs_Q2 are the driving signals of the primary switch tubes Q1 and Q2 of DCX1, V gs_Q3 With V gs_Q4 They are the driving signals of the primary switch tubes Q3 and Q4 of DCX2, and their frequencies are the series resonant frequencies of the DCX1 and DCX2 resonant cavities. ds_Q2 is the drain-source voltage of the primary switch tube Q2, V ds_Q4 is the drain-source voltage of the primary switch tube Q4. i′ r1 is the resonant current of DCX1, i′ r2 is the resonant current of DCX2. m1 is the excitation current of transformer T, i s1 、i s2 They are the currents of the secondary rectifier tube of transformer T respectively.

[0047] Figure 4 (a) is the proposed circuit topology. Figure 3 In the equivalent circuit diagram of the time period t0 to t1, the primary switch tubes Q1 and Q3 and the synchronous rectifier S1 are turned on at time t0. The transformer is equivalent to the output voltage mV o Therefore, the excitation current i m1 Linear increase. DC voltages V1 and V2 are added to the two resonant cavities respectively. In steady state, the DC bias of the two resonant capacitors is half of V1 and V2 respectively. Then, the sinusoidal currents of the two resonant cavities deviate from the excitation current, and the energy is transferred to the load through Q1, Q3 and S1. The amplitudes of the two resonant currents are determined by the power ratio adjusted by the PWM converter.

[0048] Figure 4 (b) shows the proposed circuit topology. Figure 3 In the equivalent circuit diagram of the time period t1 to t2, during the period t1 to t2, since the switching frequency is equal to the series resonance frequency of the resonant cavity, i r1 and The sum at time t1 is equal to the excitation current i m1 Q1 and Q3 are disconnected at t1. At the same time, the current flowing through S1 is equal to zero, and S1 is closed at zero current. After t1, all switches remain in the off state until t2. During this period, no energy is transferred from the input to the load, and the load is supplied by the output voltage stabilization filter capacitor C o Since all the switch tubes are turned off, the excitation inductance L m It will not be clamped by the output voltage, but will be added to the resonance. The body capacitance of the switch tubes Q1, Q3, and S1 is charged by the excitation current, and the body capacitance of the switch tubes Q2, Q4, and S2 is discharged by the excitation current. Until the moment t2, the drain-source voltage of the switch tubes Q2, Q4, and S2 is discharged to zero, and Q2, Q4, and S2 are turned on at zero voltage. After that, the converter begins to enter the next stage of operation.

[0049] Figure 4 (c) is the proposed circuit topology. Figure 3 In the equivalent circuit diagram of the time period t2 to t3, at time t2, the switches Q2, Q4 and S2 are turned on. The bias voltage on the resonant capacitor is added to the corresponding resonant tank. The excitation inductance is clamped to -mV by the equivalent output voltage. o , excitation current i m1 The resonant current deviates from the excitation current according to the sinusoidal function, and the energy is transferred to the load. Until t3, i r1 and The sum is again equal to the excitation current i m1 , Q2 and Q4 are turned off at the same time. When the primary current is equal to the excitation current, the current through S2 is equal to zero, and S2 completes zero current shutdown at the same time.

[0050] exist Figure 3 In the time period t3 to t4, since the circuit enters another dead time at t3, the equivalent circuit at this time and Figure 4 (b) is similar to the figure. Since all the switches are turned off, the magnetizing inductance participates in the resonance again, and the body capacitance of the switches Q1, Q3, and S1 is discharged by the magnetizing current. Until t4, the drain-to-source voltage of Q1, Q3, and S1 is zero, and Q1, Q3, and S1 are turned on at zero voltage at the same time.

[0051] Figure 5 A schematic diagram of a circuit topology structure of a DC converter provided in an embodiment of the present invention. Figure 1 ,2 The auxiliary energy transmission channel of the circuit topology structure proposed in 3 and 5 requires DCX1 to be cascaded in the primary PWM converter such as Buck converter and Boost converter. In this embodiment, the non-isolated PWM converter adopts Boost converter. The Boost converter consists of a pair of bridge arms composed of switch tubes Q5 and Q6, an inductor L ave , capacitor C in2 The switch tube Q5 is the upper switch tube of the bridge arm, and the switch tube Q6 is the lower switch tube of the bridge arm. In addition, the primary switch tube of the DCXs and the switch tube of the PWM converter use gallium nitride (GaN) devices to reduce turn-off losses, and the secondary rectifier uses silicon (Si) devices to reduce conduction losses.

[0052] Figure 6 (a) is an equivalent circuit of a half-bridge in a Boost converter in a DC converter provided in an embodiment of the present invention, V L is the voltage of the low voltage port, V H is the voltage of the high voltage port. In the traditional continuous conduction mode (CCM), the upper switch tube Q H Natural zero voltage turn-on can be achieved within an appropriate dead time. L Since the forward inductor current i L In critical conduction mode (CRM), when the input voltage V L Lower than the output voltage V H When the lower switch tube Q L Zero voltage turn-on can be achieved. However, when the input voltage V L Higher than the output voltage V H When the voltage is half of the value of the inductor, the effective energy in the inductor is not enough to discharge the node voltage of the bridge arm to zero. In order to achieve zero voltage turn-on, an appropriate negative current flowing through the inductor is required. Therefore, the triangle current mode (TCM) is used to make the upper switch tube Q H When the inductor current passes zero, it remains on, providing enough negative current to realize the lower switch Q L Zero voltage turn-on.

[0053] Figure 6 (b) is a Boost converter in a DC converter provided by an embodiment of the present invention. Schematic diagram of the typical input inductor current and switch bridge node voltage waveform. In the time period from t0 to t1, Q L At t0, V L Applied to the inductor L, the inductor current i L Increase linearly. Once the given T is reached at time t1 on or I s WhenL Turn off; in the time period of t1 to t2, due to Q H and Q L are both in the off state, the inductor L and the two switch tubes Q H and Q L The output capacitor C oss_H and C oss_L Resonance occurs between them. oss_L Charged by the inductor current, C oss_H The inductor current discharges. Once C oss_H The voltage across the two ends discharges to zero at time t2, Q H Immediately turn on, achieving zero voltage turn-on; during the time period t2 to t3, Q H It is turned on at time t2, V H and V L The voltage difference between the two is applied to the inductor L, and the current in the inductor L decreases linearly. L At t3, it drops to zero. In the traditional CRM case, Q H It turns off at t3 and then resonates. However, when V L Greater than V H When the zero voltage is lost in CRM, C oss_L The voltage on the L Higher than V H The disadvantage of zero voltage switching is lost when the voltage is half of the value. During the period of t3 to t4, Q H in i L After crossing zero, it remains in the on state until t4, when the given reverse current or T R When H During the period from t4 to t5, due to the H At t4, the inductor L and C oss Resonance occurs, and the output capacitor is charged or discharged by the negative inductor current. Due to the addition of an additional reverse current, at t5, C oss_L The voltage across the two ends can be reduced to zero. At this time, Q L Turn on both at the same time to achieve Q L Zero voltage turn-on.

[0054] Figure 6 (c) is the Boost converter in the DC converter provided by the embodiment of the present invention. Schematic diagram of the typical input inductor current and switch bridge node voltage waveform. At this time, there is no need to increase the upper switch tube Q H The reverse conduction time of the lower switch tube Q can be obtained L The zero voltage is turned on. Since the capacitance of the switch node is completely discharged, the body diode commutation time TR In order to reduce the conduction loss of the body diode, when the node voltage is zero, Q L Zero voltage switching is possible immediately.

[0055] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A DC converter topology with adjustable output voltage within a wide input range, characterized in that: It includes two transmission paths for transferring energy from an input port to an output port: the input ports of a main channel and an auxiliary channel are connected in series, and the output ports are connected in parallel; The main channel is a DCX based on LLC, which operates at a fixed switching frequency; the main channel includes a PWM DC-DC converter, a first filter capacitor , the second filter capacitor , the first switch tube , the second switch tube , the first resonant inductor and the first resonant capacitor The first resonant cavity formed; the first filter capacitor Connected in parallel to the input of the PWM converter, the second filter capacitor The output of the PWM converter is connected in parallel to the output of the PWM converter, and the output of the PWM converter is applied to the first switch tube. And the second switch On the bridge arm formed together, the output at the midpoint of the bridge arm is applied to the first resonant cavity; The auxiliary channel comprises two stages, the first stage adopts a non-isolated PWM DC-DC converter, the second stage adopts a DCX based on LLC, the first stage and the second stage are cascaded on the input side of the DCX of the auxiliary channel, and the output voltage is adjusted by adjusting the non-isolated PWM DC-DC converter of the auxiliary channel; the auxiliary channel comprises a third filter capacitor , the third switch tube , the fourth switch tube , the second resonant inductor and the second resonant capacitor The second resonant cavity formed; the third filter capacitor Connected in parallel to the third switch And the fourth switch On the bridge arm formed together, the output at the midpoint of the bridge arm is applied to the second resonant cavity; The main channel and the auxiliary channel share a common excitation inductor Center-tapped transformer and by the first synchronous rectifier switch And the second rectifier switch tube The outputs of the first resonant cavity and the second resonant cavity are applied to the center-tapped transformer On the input side, the transformer The output side of the device is connected with a synchronous rectifier; The DCX used in the main channel and the DCX used in the auxiliary channel both operate at the series resonant frequency of their respective resonant cavities.

2. The DC converter topology structure with adjustable output voltage within a wide input range according to claim 1, characterized in that: The switching frequency of the PWM converter used by the auxiliary channel is independent of the two DCXs.

3. The DC converter topology structure with adjustable output voltage within a wide input range according to claim 1, characterized in that: The DCX used by the main channel and the DCX used by the auxiliary channel operate at the same series resonant frequency and duty cycle.

4. The DC converter topology structure with adjustable output voltage within a wide input range according to claim 1, characterized in that: The PWM converter of the auxiliary channel adopts a triangle wave current mode modulation method.

5. The DC converter topology structure with adjustable output voltage within a wide input range according to claim 1, characterized in that: The switch tube in the PWM converter of the auxiliary channel and the primary switch tube of the DCX are gallium nitride devices.

6. The DC converter topology structure with adjustable output voltage within a wide input range according to claim 1, characterized in that: The synchronous rectifier of the topology structure adopts silicon devices.

7. The DC converter topology structure with adjustable output voltage within a wide input range according to claim 1, characterized in that: The driving signal of the synchronous rectifier of the topological structure is synchronized with the driving signal of the primary switch tube, and has the same and fixed frequency and duty cycle.

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