Dc-dc converter and control method thereof

Abstract

The application discloses a DC-DC converter and a control method thereof, and belongs to the technical field of power electronics. The DC-DC converter comprises a primary side hybrid bridge rectifier module, the primary side hybrid bridge rectifier module contains three groups of bridge arms and a bidirectional switch, the bidirectional switch is connected in series by two field effect transistors in a common source mode, the left and right bridge arms are field effect transistors, and the middle bridge arm is a field effect transistor connected in series with a diode. Current can only flow in one direction, and the problem of being clamped by a parasitic diode of a field effect transistor is eliminated through the unidirectional bridge arm, and further combination of three kinds of gain modes is used to realize a very wide gain range.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and in particular to a DC-DC converter and its control method. Background Technology

[0002] With the development of new energy technologies, photovoltaic power generation, electric vehicles, and other applications place increasingly higher demands on the gain range and efficiency of DC-DC converters. Resonant converters have become a research hotspot due to their high efficiency, high power density, and electrical isolation characteristics. Among them, series resonant (LLC) converters are particularly popular due to their simple structure and excellent soft-switching performance. However, when traditional series resonant converters using pulse frequency modulation (PFM) are applied to wide-range voltage regulation applications, the voltage gain range is limited, the circulating current is large, and the wide switching frequency range when using PFM for voltage regulation is unfavorable for magnetic component design.

[0003] To address the problems of traditional series resonant converters in wide-range voltage regulation applications, researchers have proposed corresponding improvements in topology and control strategies in recent years. Existing technology one combines the operating modes of full-bridge and half-bridge topologies and employs pulse width modulation (PWM) to achieve a 2x gain range with high efficiency; however, it still cannot meet the application requirements of practical wide-range voltage applications. Existing technology two combines pulse frequency modulation and pulse width modulation control strategies, achieving approximately a 4x gain range by combining multiple gain modes; however, the hybrid modulation strategy of pulse frequency modulation and pulse width modulation is not conducive to the optimized design of resonant converters. Summary of the Invention

[0004] This application aims to provide a DC-DC converter and its control method, which is based on primary-side topology reconstruction circuit structure to meet the requirements of wide gain range, high efficiency and low device cost.

[0005] To achieve the above objectives, the technical solution of this application is as follows: A DC-DC converter, comprising, The primary-side filter module is used to filter the input DC power. The primary-side hybrid bridge rectifier module is used to receive the filtered input DC power. By switching the gain mode and changing the duty cycle of each gain mode, the gain range of the filtered DC power is expanded to obtain the first AC power. The secondary rectifier module is used to rectify the first AC power to obtain the output DC power.

[0006] The primary-side hybrid bridge rectifier module includes three bridge arms. The middle bridge arm includes: a first switch, the first end of which is connected to the first output terminal of the primary-side filter module; the second end of which is connected to the anode of a first diode; the cathode of the first diode is connected to the first end of a second switch; the second end of the second switch is connected to the anode of a second diode; and the cathode of the second diode is connected to the second terminal of the primary-side filter module. The first end of a third switch is connected to the third output terminal of the primary-side filter module; the second end of the third switch is connected to the second end of a fourth switch; the first end of the fourth switch is connected to the first end of a first inductor; and the second end of the first inductor is connected to the cathode of the first diode and the first end of the second switch.

[0007] Optionally, the primary-side hybrid bridge rectifier module further includes: a fifth switch, the first end of which is connected to the first output terminal of the primary-side filter module; the second end of which is connected to the first end of the sixth switch; the second end of the sixth switch is connected to the second output terminal of the primary-side filter module; the first end of the seventh switch is connected to the first output terminal of the primary-side filter module; the second end of the seventh switch is connected to the first end of the eighth switch; the second end of the eighth switch is connected to the second output terminal of the primary-side filter module; and the second end of the first inductor and the midpoint of the series connection of the seventh and eighth switches are connected to the secondary-side rectifier module. The unidirectional bridge arm eliminates the parasitic diode clamping problem of the N-type metal-oxide-semiconductor field-effect transistor in the primary-side hybrid bridge rectifier module, achieving higher gain. Linear charging of the first inductor through the conduction of the unidirectional bridge arm improves the gain capability compared to the series resonant topology in high-gain mode.

[0008] The DC-DC converter can use the hybrid bridge structure of the primary-side hybrid bridge rectifier module to enable the resonant inductor and resonant capacitor to simultaneously have multiple charging modes. By changing the duty cycle of each charging mode, the output DC power can be adjusted to expand the gain range. It only slightly increases the number of devices without increasing the number of resonant elements, resulting in low hardware cost.

[0009] Optionally, the primary-side filtering module includes: a first capacitor, a first terminal of which is connected to the positive terminal of the input DC power, a second terminal of which is connected to the first terminal of a second capacitor, and a second terminal of which is connected to the negative terminal of the input DC power; the first terminal of the first capacitor serves as the first output terminal of the primary-side filtering module, the second terminal of the second capacitor serves as the second output terminal of the primary-side filtering module, and the midpoint of the series connection between the first capacitor and the second capacitor serves as the third output terminal of the primary-side filtering module.

[0010] Optionally, the resonant converter module adopts a series resonant structure. Regarding the design of the excitation inductor, a larger inductance value can be designed to reduce circulating current losses.

[0011] Optionally, the secondary-side rectifier module adopts a full-wave rectifier structure or a full-bridge rectifier structure.

[0012] Optionally, the first switch, the second switch, the third switch, the fourth switch, the fifth switch, the sixth switch, the seventh switch, and the eighth switch are N-type metal-oxide-semiconductor field-effect transistors, with the first terminal of each of the following switches being a drain and the first terminal of each of the following switches being a source.

[0013] Optionally, the DC-DC converter further includes a control unit for switching the gain modes, changing the duty cycle of each gain mode, and expanding the gain range.

[0014] A control method for a DC-DC converter, applied to a DC-DC converter as described above, includes: The gain mode is selected according to the gain requirement; wherein, the gain modes include: low gain mode, medium gain mode and high gain mode. In low gain mode and medium gain mode, the fifth switch, the sixth switch, the seventh switch, the eighth switch, the third switch and the fourth switch are active, and the first switch and the second switch are inactive; in high gain mode, the fifth switch, the sixth switch, the seventh switch, the eighth switch, the first switch and the second switch are active, and the third switch and the fourth switch are inactive. Calculate the duty cycle for each gain mode; Determine the driving logic of the switches in the primary-side hybrid bridge rectifier module.

[0015] Different modes are selected for the control power unit according to different gain requirements, and an appropriate duty cycle is selected to meet the output DC power requirements. A very wide gain range of DC-DC converter is achieved by connecting the three gain modes.

[0016] Optionally, the calculation of the duty cycle in each gain mode includes: In low-gain and medium-gain modes, the gain curves of duty cycle versus corresponding gain are obtained by solving the time-domain equations, as shown below:

[0017] Where Q represents the quality factor of the resonant converter module; The phase angle representing the resonant current; The phase angle representing the resonant voltage; This represents the normalized resonant capacitor voltage; This represents the normalized resonant current. The normalized resonant capacitor voltage at the initial moment is represented by M; the corresponding gain is represented by M. The time-domain equations are solved using numerical calculation methods to obtain the gain under different duty cycles and different loads. In high-gain mode, the duty cycle D is calculated by inversely based on the high gain. HG , means as follows:

[0018] Among them, D HG Indicates the duty cycle in high-gain mode; M HG Indicates high gain.

[0019] Optionally, the driving logic for determining the switches in the primary-side hybrid bridge rectifier module includes: in low-gain mode, during the positive half-cycle, using pulse width modulation to control the primary-side hybrid bridge rectifier module, operating in the following four switching modes: In the first switching mode, within the range [t0-t1], the system enters the first resonance stage, during which the fifth switch, the third switch, and the fourth switch are turned on. The conduction time of the third switch and the fourth switch is 0.5T. s D LG Among them, T s D represents the switching period. LG Indicates the duty cycle in low gain mode; In the second switching mode, within [t1-t2], the third and fourth switches are turned off; In the third switching mode, within [t2-t3], the second resonance stage is entered, the seventh switch is turned on, and the resonant current is equal to the excitation current at time [t3-t4]. In the fourth switching mode, within [t4-t5], the fifth and seventh switches are turned off; During the negative half-cycle, the operating states of the fifth and sixth switches are opposite to those during the positive half-cycle, as are the operating states of the seventh and eighth switches, while the operating states of the third and fourth switches are consistent with those during the positive half-cycle. Employing a pulse width modulation strategy is more beneficial for magnetic component design and improves electromagnetic compatibility.

[0020] Optionally, the step of determining the driving logic for the switches in the primary-side hybrid bridge rectifier module further includes: in medium-gain mode, during the positive half-cycle, using pulse width modulation to control the primary-side hybrid bridge rectifier module, operating in the following four switching modes: In the first switching mode, within the range [t0-t1], the system enters the first resonance stage, during which the fifth and eighth switches are turned on, and the on-time of the fifth and eighth switches is 0.5T. s D MG Among them, T s D represents the switching period. MG Indicates the duty cycle in medium gain mode; In the second switching mode, within [t1-t2], the eighth switch is turned off; In the third switching mode, within [t2-t3], the second resonance stage is entered, and the third switch and the fourth switch are turned on. At time [t3-t4], the resonant current is equal to the excitation current. In the fourth switching mode, within [t4-t5], the fifth switch, the third switch, and the fourth switch are turned off; During the negative half-cycle, the operating states of the fifth and sixth switches are opposite to those during the positive half-cycle, the operating states of the seventh and eighth switches are opposite to those during the positive half-cycle, and the operating states of the third and fourth switches are consistent with those during the positive half-cycle.

[0021] Optionally, the step of determining the driving logic for the switches in the primary-side hybrid bridge rectifier module further includes: in high-gain mode, during the positive half-cycle, using pulse width modulation to control the primary-side hybrid bridge rectifier module, operating in the following four switching modes: In the first switching mode, within the range [t0-t1], the system enters a linear phase, during which the eighth switch and the first switch are turned on, and the on-time of the eighth switch and the first switch is 0.5T. s D HG Among them, T s D represents the switching period. HG Indicates the duty cycle in high-gain mode; In the second switching mode, within [t1-t2], the first switch is off and the fifth switch is on; In the third switching mode, within [t2-t3], the resonant current is equal to the excitation current; In the fourth switching mode, within [t3-t4], the fifth and eighth switches are turned off; During the negative half-cycle, the operating states of the fifth and sixth switches are opposite to those during the positive half-cycle, the operating states of the seventh and eighth switches are opposite to those during the positive half-cycle, and the operating states of the first and second switches are opposite to those during the positive half-cycle.

[0022] The DC-DC converter and its control method proposed in this application use a unidirectional switch in the middle bridge arm to solve the problem of parasitic diode clamping, expand the gain range, and further combine three gain modes to achieve a very wide gain range. While achieving a wide voltage gain range, it can also maintain high efficiency, making it a better choice for wide-range DC-DC conversion in new energy power generation and power consumption applications.

[0023] To make the above-mentioned features and advantages of the application more apparent and understandable, specific embodiments are provided below, and detailed descriptions are given in conjunction with the accompanying drawings. Attached Figure Description

[0024] Figure 1 This is a structural diagram of the DC-DC converter provided in this application.

[0025] Figure 2 A circuit diagram of a first specific embodiment of the DC-DC converter provided in this application.

[0026] Figure 3 A flowchart of the control method for the DC-DC converter provided in this application.

[0027] Figure 4 Duty cycle D in gain mode MG With gain M MG A schematic diagram of the gain curve.

[0028] Figure 5 The equivalent circuit diagrams are for low-gain mode and medium-gain mode.

[0029] Figure 6 This is the modal waveform diagram for the low-gain mode.

[0030] Figure 7 This is the modal waveform diagram for the medium gain mode.

[0031] Figure 8 The equivalent circuit diagram is for high-gain mode.

[0032] Figure 9 This is the modal waveform diagram for the high-gain mode.

[0033] Figure 10 This is the steady-state waveform in low-gain mode.

[0034] Figure 11 This is the steady-state waveform diagram in medium gain mode.

[0035] Figure 12 This is the steady-state waveform in high-gain mode.

[0036] In the accompanying drawings, similar reference numerals refer to the same elements. Detailed Implementation

[0037] To make the objectives and technical solutions of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the described embodiments of this application without creative effort are within the scope of protection of this application.

[0038] This application provides a DC-DC converter; please refer to [link / reference]. Figure 1 , Figure 1 This is a structural diagram of the DC-DC converter provided in this application. The DC-DC converter includes: a power unit 1 and a control unit 2, which are connected. The control unit 2 provides switching drive signals to the power unit 1. The power unit 1 includes: Primary-side filter module 11 filters the input DC voltage V. in Perform filtering; Primary-side hybrid bridge rectifier module 12 is used to receive the filtered input DC voltage V. in By switching gain modes and changing the duty cycle of each gain mode, the gain range of the filtered DC power is expanded to obtain the first AC power v1. The resonance transformation module 13 is used to perform resonance transformation on the first AC current v1 to obtain the second AC current v2; Secondary rectifier module 14 is used to rectify the second AC current v2 to obtain the output DC current V. o .

[0039] As an example, the primary-side filtering module 11 includes: capacitor C in1 Capacitor C in1 The first terminal is connected to the input DC voltage V. in The positive terminal of the capacitor C in1 The second terminal is connected to capacitor C in2 The first terminal, capacitor C in2 The second terminal is connected to the input DC voltage V. in The negative terminal. Capacitor C in1 With capacitor C in2 Used to control the input DC voltage V in The filtered signal is fed into the primary-side hybrid bridge rectifier module 12. Capacitor C in1 The first terminal serves as the first output terminal of the primary-side filter module 11, and capacitor C in2 The second terminal serves as the second output terminal of the primary-side filter module 11, and capacitor C in1 With capacitor C in2 The midpoint of the series connection is used as the third output terminal of the primary-side filter module 11.

[0040] Specifically, the input DC voltage V in Depending on the application, for example, a stable DC bus voltage or a wide range of DC current in the power supply can be used as the input of this DC-DC converter.

[0041] Specifically, capacitor C in1 With capacitor C in2 This is a filter inductor. Capacitor C in1 With capacitor C in2 They have the same capacitance value.

[0042] As an example, the primary-side hybrid bridge rectifier module 12 includes: three bridge arms, a switch Q1, the first end of which is connected to the first output terminal of the primary-side filter module 11, the second end of which is connected to the first end of the switch Q2, and the second end of the switch Q2 is connected to the second output terminal of the primary-side filter module 11, forming the right bridge arm; the first end of the switch Q3 is connected to the first output terminal of the primary-side filter module 11, the second end of which is connected to the first end of the switch Q4, and the second end of the switch Q4 is connected to the second output terminal of the primary-side filter module 11, forming the left bridge arm; the switch Q... The first terminal of switch Q5 is connected to the first output terminal of the primary-side filter module 11. The second terminal of switch Q5 is connected to the anode of diode D3. The cathode of diode D3 is connected to the first terminal of switch Q6. The second terminal of switch Q6 is connected to the anode of diode D4. The cathode of diode D4 is connected to the second output terminal of the primary-side filter module 11, forming the intermediate bridge arm. The first terminal of switch Q7 is connected to the third output terminal of the primary-side filter module 11. The second terminal of switch Q7 is connected to the second terminal of switch Q8. The first terminal of switch Q8 is connected to the midpoint of the series connection of switches Q3 and Q4. Inductor L... r The first terminal is connected to the first terminal of switch Q8, and the inductor L r The second terminal is connected to the cathode of diode D3 and the first terminal of switch Q6.

[0043] Specifically, switches Q1, Q2, Q3, Q4, Q5, Q6, Q7, and Q8 are N-type metal-oxide-semiconductor field-effect transistors (MOSFETs). The first terminal of switches Q1, Q2, Q3, Q4, Q5, Q6, Q7, and Q8 is the drain, and the first terminal of switches Q1, Q2, Q3, Q4, Q5, Q6, Q7, and Q8 is the source.

[0044] Specifically, switches Q7 and Q8 constitute a bidirectional switch.

[0045] Specifically, bridge arms Q5-Q6 are formed by connecting switches Q5 and Q6 in series with diodes D3 and D4 respectively to form unidirectional bridge arms, and the current in bridge arms Q5-Q6 can only flow in one direction.

[0046] Specifically, inductor L r It is a resonant inductor, and current flows through inductor L r The current is the resonant current i Lr Inductor L r The voltage across the terminals is the resonant inductor voltage v. Lr The conduction of a single bridge arm affects the inductor L. r Linear charging is performed, and in high-gain mode (HG), the gain capability is improved compared to the series resonant structure.

[0047] The primary-side hybrid bridge rectifier module 12 includes three bridge arms and a bidirectional switch. The bidirectional switch consists of two N-type metal-oxide-semiconductor field-effect transistors connected in series from their common source. The left and right bridge arms are N-type metal-oxide-semiconductor field-effect transistors, and the middle bridge arm is an N-type metal-oxide-semiconductor field-effect transistor connected in series with a diode. Current can only flow in one direction. If a unidirectional bridge arm is not used, as the duty cycle further increases, the resonant inductor voltage v... Lr The parasitic diode of the field-effect transistor in the middle bridge arm will be clamped to -0.5. V in Resonant current i Lr The inductance L will decrease linearly. r Energy cannot be transferred to the secondary side through the transformer, resulting in increased circulating current losses and no improvement in gain. This application eliminates the parasitic diode clamping problem of the field-effect transistor when the primary-side hybrid bridge rectifier module 12 boosts voltage by using a unidirectional bridge arm, thereby achieving higher gain capability.

[0048] Specifically, the DC-DC converter can utilize the hybrid bridge structure of the primary-side hybrid bridge rectifier module 12 to enable the inductor... L r and capacitor C r It can simultaneously possess multiple charging modes, and the output DC voltage V can be adjusted by changing the duty cycle D of each charging mode. o This expands the gain range.

[0049] As an example, the resonant transformation module 13 adopts a series resonant structure, specifically including: capacitor C r Capacitor C r The first terminal and the inductor L r The second terminal is connected to capacitor C. r The second terminal is connected to the first terminal of the primary winding N1 of transformer T1, and the second terminal of the primary winding N1 of transformer T1 is connected to the midpoint of the series connection of switch Q1 and switch Q2. The inductor L... m The primary winding N1 of transformer T1 is connected in parallel with the secondary winding N2 of transformer T1, and the output DC voltage V is connected in parallel with the secondary winding N2 of transformer T1.o connect.

[0050] As an example, inductor L m For the magnetizing inductor, current flows through inductor L m The current is the excitation current i Lm In terms of magnetizing inductor design, a larger inductance value can be designed to reduce circulating current losses.

[0051] Specifically, capacitor C r The voltage across the terminals is the resonant capacitor voltage v. cr .

[0052] As an example, the DC-DC converter further includes: a resistor R L resistance R L As a load, it is connected in parallel to the output DC voltage V. o Both ends.

[0053] Please see Figure 2 , Figure 2 This is a circuit diagram of a first specific embodiment of the DC-DC converter provided in this application. In this specific embodiment, the secondary-side rectifier module 14 adopts a full-wave rectifier structure, including: diode D1, the anode of diode D1 being connected to the first terminal of the secondary winding N2 of transformer T1, the cathode of diode D1 being connected to the cathode of diode D2, the anode of diode D2 being connected to the first terminal of the secondary winding N2 of transformer T1, and capacitor C. o The first terminal is connected to the cathode of diode D1, and capacitor C o The second end is connected to the midpoint of the secondary winding N2 of transformer T1.

[0054] Specifically, the turns ratio of the primary winding of transformer T1 to the upper half of the secondary winding and the lower half of the secondary winding is: n :1:1.

[0055] Specifically, the current flowing through diode D1 is i D1 The current flowing through diode D2 is i D2 .

[0056] As an example, the secondary-side rectifier module 14 may include a full-wave rectifier structure or a full-bridge rectifier structure, etc., and is not limited to the cases proposed in this application.

[0057] As an example, the control unit 2 is used to switch the gain mode of the power unit 1, change the duty cycle of each gain mode, and expand the gain range.

[0058] Specifically, according to different gain requirements, control unit 2 controls power unit 1 to select different modes and selects an appropriate duty cycle D to meet the output DC voltage V. oThe requirement is to achieve a very wide gain range for the DC-DC converter by connecting three gain modes.

[0059] As an example, the three gain modes include: low-gain mode (LG), medium-gain mode (MG), and high-gain mode.

[0060] As an example, the control unit 2 may be a digital signal processing chip (DSP), which integrates a control method for a DC-DC converter provided in this application, for switching the gain mode of the power unit 1, changing the duty cycle of each gain mode, and expanding the gain range of the DC-DC converter.

[0061] As an example, the model of the digital signal processing chip includes: TMS320C6000.

[0062] This application also provides a control method for a DC-DC converter, applied to the control unit of the DC-DC converter proposed in this application. Please refer to... Figure 3 , Figure 3 The flowchart is for the control method of the DC-DC converter provided in this application. The control method of the DC-DC converter includes steps S1 to S3.

[0063] Step S1: Select the gain mode according to the gain requirement; Step S2: Calculate the duty cycle for each gain mode; Step S3: Determine the driving logic of the switches in the primary-side hybrid bridge rectifier module 12.

[0064] In step S1, please refer to Figure 3 In step S1, select the gain mode according to the gain requirement.

[0065] As an example, the gain mode is selected based on gain requirements, including: when the output DC voltage V o Gain requirement is input DC voltage V in When the gain is 0 to 0.5 times that of the output DC voltage, select low gain mode; when the output DC voltage V... o Gain requirement is input DC voltage V in When the gain is 0.5 to 1 times, select medium gain mode; when the output DC voltage V o The minimum gain requirement is the input DC voltage V. in When the gain is 1 times that of the target value, select the high gain mode.

[0066] As an example, in low-gain mode, bridge arms Q1-Q2, bridge arms Q3-Q4 and bidirectional switches Q7-Q8 are working, while bridge arms Q5-Q6 are not working.

[0067] In medium gain mode, bridge arms Q1-Q2, bridge arms Q3-Q4 and bidirectional switches Q7-Q8 are working, while bridge arms Q5-Q6 are not working.

[0068] In high-gain mode, bridge arms Q1-Q2, Q3-Q4, and Q5-Q6 are operational, while bidirectional switches Q7-Q8 are inactive.

[0069] In step S2, please refer to Figure 3 In step S2, the duty cycle D of each gain mode is calculated.

[0070] As an example, in medium-gain mode, due to the low fundamental component, the fundamental analysis method has a large error. The accurate gain is obtained by solving the time-domain equation to obtain the duty cycle D. MG With medium gain M MG The gain curve is shown below:

[0071] Where Q represents the quality factor of the resonant converter module 13; The phase angle representing the resonant current. The phase angle representing the resonant capacitor voltage; This represents the normalized resonant capacitor voltage; This represents the normalized resonant current. This represents the normalized resonant capacitor voltage at the initial moment. The time-domain equations are solved using numerical methods to obtain the voltages with different duty cycles, D. MG and the gain M under different loads MG Furthermore, it was obtained that different duty cycles D MG Gain curves for different loads and corresponding quality factors Q.

[0072] For example, in medium gain mode, please refer to [link / reference]. Figure 4 , Figure 4 Duty cycle D in medium gain mode MG With gain M MG The gain curve diagram is shown. A larger quality factor Q indicates lower resonant converter losses or a larger load, resulting in a higher output DC voltage V. o The weaker the lift capability, the less effective the same duty cycle D will be in the medium gain mode with a gain range of [0.5,1]. MG Below, medium gain M MG It decreases as the quality factor Q increases.

[0073] As an example, in low-gain mode, the duty cycle D is obtained by solving the time-domain equation. LG With gain M LG The gain curve is calculated in the same way as the medium gain mode, and will not be repeated here.

[0074] As an example, in high-gain mode, by controlling the duty cycle D... HG Adjust the output DC voltage V o That is, it can also be based on high gain M HG Back-calculation of duty cycle D HG , means as follows: .

[0075] In step S3, please refer to Figure 3 In step S3, the driving logic of the switches in the primary-side hybrid bridge rectifier module 12 is determined.

[0076] For example, please refer to Figure 5 , Figure 5 This is the equivalent circuit diagram for low-gain mode and medium-gain mode. In low-gain mode, pulse width modulation is used to control the switches in the primary-side hybrid bridge rectifier module 12. At this time, bridge arms Q1-Q2, bridge arms Q3-Q4, and bidirectional switches Q7-Q8 are active, while bridge arms Q5-Q6 remain off. Please refer to [link / reference]. Figure 6 , Figure 6 The waveform diagram is for the low-gain mode. During the positive half-cycle, the primary-side hybrid bridge rectifier module 12 operates in the following four switching modes: In the first switching mode, within [t0-t1], the system enters the first resonance stage. Switches Q1, Q7, and Q8 are initially turned on, and the voltage applied to the resonance converter module 13 is the input DC voltage V. in Half of the inductance L r With capacitor C r Resonance occurs, and the conduction time of switches Q7 and Q8 is 0.5T. s D LG Inductor L r Energy is transferred to the load side through transformer T1. Wherein, T... s Indicates the switching cycle.

[0077] In the second switching mode, within [t1-t2], after the first resonance stage ends, the dead zone stage begins, and switches Q7 and Q8 are turned off.

[0078] In the third switching mode, within [t2-t3], the second resonance stage begins, and switch Q3 is turned on. At this time, the voltage drop across the resonant tank is 0, and the inductor L... r Still related to capacitor C r Resonance, inductance L r The energy is still transferred to the load side through transformer T1 until the resonant current i at time t3. Lr Reduce to excitation current i Lm Because of the excitation inductance L m It can be designed to have a larger excitation current i Lm The value is approximately 0. The resonant current i at time [t3-t4] is approximately 0.Lr Equal to excitation current i Lm Resonant capacitor voltage v cr The value remains essentially unchanged. At this point, the circulating current of the DC-DC converter is approximately zero, thus avoiding the circulating current loss during the non-energy transfer stage.

[0079] In the fourth switching mode, within [t4-t5], after the second resonance stage ends, the dead zone stage begins, and switches Q1 and Q3 are turned off.

[0080] Specifically, similar to the positive half-cycle, the operating states of switches Q1 and Q2 are opposite to those of the positive half-cycle, as are those of switches Q3 and Q4, while the operating states of switches Q7 and Q8 are the same as those of the positive half-cycle. Inductor L r and capacitor C r There are two resonant stages, and the input voltage applied to the resonant converter module 13 is different in the two resonant stages. The duty cycle D of the first resonant stage [t0-t1] is... LG Adjust the output DC voltage V o At this time, the switching frequency of the DC-DC converter is equal to the resonant frequency.

[0081] Specifically, in the primary-side hybrid bridge rectifier module 12, switches Q3 and Q4 achieve zero-voltage turn-on (ZVS), and switches Q1, Q2, Q7, and Q8 achieve zero-current turn-on (ZCS). In the secondary-side rectifier module 14, diodes D1 and D2 achieve zero-voltage turn-off.

[0082] As an example, in medium-gain mode, pulse width modulation is used to control the switches in the primary-side hybrid bridge rectifier module 12. In this mode, bridge arms Q1-Q2, bridge arms Q3-Q4, and bidirectional switches Q7-Q8 are operational, while bridge arms Q5-Q6 remain off. (See also...) Figure 7 , Figure 7 The waveform diagram is for the medium-gain mode. During the positive half-cycle, the primary-side hybrid bridge rectifier module 12 operates in the following four switching modes: In the first switching mode, within [t0-t1], the first resonance stage is entered. Switches Q1 and Q4 are initially turned on, and the voltage applied to the resonant converter module 13 is the input DC voltage V. in Inductor L r With capacitor C r Resonance occurs, and the conduction time of switches Q1 and Q4 is 0.5T. s D MG At this time, energy is transferred to the load side through transformer T1.

[0083] In the second switching mode, within [t1-t2], after the first resonance stage ends, it enters the dead zone stage, and switch Q4 is turned off.

[0084] In the third switching mode, within [t2-t3], the second resonance stage begins, and switches Q7 and Q8 are turned on. At this time, the voltage drop applied to the resonant converter module 13 is the input DC voltage V. in Half of the inductance L r Still related to capacitor C r Resonant energy transfer continues until the resonant current i at time t3. Lr Reduce to excitation current i Lm And the excitation current i Lm The value is approximately 0. The resonant current i at time [t3-t4] is approximately 0. Lr Equal to excitation current i Lm Similar to the low-gain mode principle, the resonant capacitor voltage v cr The value remains essentially unchanged. At this point, the circulating current of the DC-DC converter is approximately zero, thus avoiding the circulating current loss during the non-energy transfer stage.

[0085] In the fourth switching mode, within [t4-t5], after the second resonance stage ends, the dead zone stage begins, and switches Q1, Q7, and Q8 are turned off.

[0086] Specifically, similar to the positive half-cycle, the operating states of switches Q1 and Q2 are opposite to those in the positive half-cycle, as are those of switches Q3 and Q4, while the operating states of switches Q7 and Q8 are the same as in the positive half-cycle. Within half a cycle, the inductor L... r and capacitor C r There are two resonant modes. By controlling the duty cycle D of the first resonant phase [t0-t1]... MG Adjust the output DC voltage V o The switching frequency remains constant at the resonant frequency.

[0087] Specifically, in the primary-side hybrid bridge rectifier module 12, switches Q7 and Q8 can achieve zero-voltage turn-on, and switches Q1, Q2, Q3, and Q4 can achieve zero-current turn-on. In the secondary-side rectifier module 14, diodes D1 and D2 achieve zero-voltage turn-off.

[0088] For example, please refer to Figure 8 , Figure 8 This is the equivalent circuit diagram for high-gain mode. In high-gain mode, pulse width modulation is used to control the switches in the primary-side hybrid bridge rectifier module 12. At this time, bridge arms Q1-Q2, Q3-Q4, and Q5-Q6 are active, while bidirectional switches Q7-Q8 remain off. Please refer to [link / reference]. Figure 9 , Figure 9 The waveform diagram is for the high-gain mode. During the positive half-cycle, the primary-side hybrid bridge rectifier module 12 operates in the following four switching modes: In the first switching mode, within [t0-t1], the linear phase begins, and the switch...Q 4. Switch Q 5 is turned on, input DC voltage V in Give inductor L r Linear charging, charging time is 0.5T. s D HG At this time, the resonant capacitor voltage v cr constant.

[0089] In the second switching mode, within [t1-t2], after the linear phase ends, switch Q5 is turned off and switch Q1 is turned on. At this time, the inductor L... r With capacitor C r Resonance, inductance L r The energy is transferred to the load side through transformer T1 until the resonant current i at time t2. Lr Reduce to excitation current i Lm And the excitation current i Lm It is approximately 0.

[0090] In the third switching mode, within [t2-t3], the resonant current i Lr Equal to excitation current i Lm Resonant capacitor voltage v cr The value remains essentially unchanged, and the circulating current of the DC-DC converter is approximately zero, thereby reducing the circulating current loss.

[0091] In the fourth switching mode, within [t3-t4], after the resonance stage ends, the dead zone stage begins, and switches Q1 and Q4 are turned off.

[0092] Specifically, similar to the positive half-cycle, the operating states of switches Q1 and Q2 are opposite to those of the positive half-cycle, the operating states of switches Q3 and Q4 are opposite to those of the positive half-cycle, and the operating states of switches Q5 and Q6 are the same as those of the positive half-cycle. The high-gain mode is achieved by first supplying inductor L during the linear phase. r Linear charging, and then during the resonant phase, the inductor L... r Energy is transferred to the load, thereby expanding the gain range.

[0093] Specifically, in the primary-side hybrid bridge rectifier module 12, switches Q3, Q4, Q5, and Q6 achieve zero-voltage turn-on, while in the secondary-side rectifier module 14, diodes D1 and D2 achieve zero-voltage turn-off.

[0094] In a specific embodiment of this application, the proposed wide-gain DC-DC converter based on multi-mode composite charging was simulated using PLECS, and the simulation parameters are shown in Table 1.

[0095] Table 1. Simulation Parameter Table

[0096] The steady-state waveforms of the DC-DC converter in the three gain modes are as follows: Figures 10 to 12 As shown, Figure 10 This is the steady-state waveform in low-gain mode. Figure 11 This is the steady-state waveform in medium gain mode. Figure 12 This is the steady-state waveform in high-gain mode. The voltage adjustment range in low-gain mode is 50-100V, and the duty cycle D... LG The voltage regulation range in medium gain mode is 100-200V, and the duty cycle D is 0.4. MG The voltage regulation range in high-gain mode is 200-420V, with a duty cycle of 0.3. HG The value is 0.32. It can be seen that, with a constant output current of 5A, by combining three gain modes, this DC-DC converter can achieve a wide output voltage range of 50~420V with an input voltage of 400V. Simultaneously, the switching frequency of the DC-DC converter remains constant at 140kHz, and unlike traditional LLC converters, the magnetizing inductor... L m It can be designed to be larger, reducing conduction and turn-off losses, which helps to improve the operating efficiency of DC-DC converters.

[0097] Furthermore, the DC-DC converter proposed in this application is qualitatively and quantitatively compared with similar existing solutions, as shown in Table 2.

[0098] Table 2. Comparison of the proposed structure with existing similar solutions

[0099] As shown in Table 2, the proposed DC-DC converter utilizes the multi-mode composite charging theory, adding a set of unidirectional bridge arms composed of N-type metal-oxide-semiconductor field-effect transistors and diodes, along with a bidirectional switch, to the full-bridge LLC, thereby enabling the inductor L... r It can simultaneously possess multiple charging modes, including linear charging mode and resonant energy transfer mode, and combine multiple gain modes to achieve the effect of expanding the gain range, realizing a wide gain range of [1-8.4], and achieving a full-load power of 2.1kW in simulation.

[0100] The DC-DC converter and its control method provided in this application solve the parasitic diode clamping problem by using a unidirectional switch in the middle bridge arm, thus expanding the gain range. Furthermore, by combining three gain modes, a very wide gain range is achieved. This only slightly increases the number of primary-side components without increasing the number of resonant components, resulting in low hardware cost. Compared to existing methods, it offers higher full-load power and is more suitable for various applications such as new energy power consumption and power generation. Moreover, the DC-DC converter maintains a constant switching frequency and employs a pulse width modulation strategy, which is more conducive to magnetic component design and improves electromagnetic compatibility. The magnetizing inductor L... mThe design allows for larger values ​​to reduce circulating current losses, and almost all soft-switching features with zero-voltage turn-on are implemented. Overall, the proposed DC-DC converter achieves a wide voltage gain range while maintaining high efficiency, making it a superior choice for wide-range DC-DC conversion in new energy power generation and consumption applications.

[0101] Although this application has been disclosed above with reference to embodiments, it is not intended to limit this application. Anyone skilled in the art may make some modifications and refinements without departing from the spirit and scope of this application. Therefore, the scope of protection of this application shall be determined by the appended claims.

Claims

1. A DC-DC converter, characterized in that, include, The primary-side filter module filters the input DC power. The primary-side hybrid bridge rectifier module receives the filtered input DC power and expands the gain range of the filtered DC power by switching the gain mode to change the duty cycle of each gain mode, thus obtaining the first AC power. The secondary rectifier module is used to rectify the first AC power to obtain the output DC power; The control unit switches the gain modes and changes the duty cycle of each gain mode to expand the gain range. The primary-side hybrid bridge rectifier module includes three bridge arms and a bidirectional switch. The three bridge arms are a left bridge arm, a right bridge arm, and a middle bridge arm, which are connected in parallel. The middle bridge arm includes a first switch, the first end of which is connected to the first output terminal of the primary-side filter module, the second end of which is connected to the anode of a first diode, the cathode of the first diode is connected to the first end of a second switch, the second end of which is connected to the anode of a second diode, and the cathode of the second diode is connected to the second terminal of the primary-side filter module. The bidirectional switch includes a third switch, the first end of which is connected to the third output terminal of the primary-side filter module, and the second end of which is connected to the second end of a fourth switch. The first end of the fourth switch is connected to the first end of a first inductor, and the second end of the first inductor is connected to the cathode of the first diode and the first end of the second switch. The gain modes include: low gain mode, medium gain mode and high gain mode. In the low gain mode and the medium gain mode, the left bridge arm, the right bridge arm and the bidirectional switch are working, and the middle bridge arm is not working. In the high gain mode, the left bridge arm, the right bridge arm and the middle bridge arm are working, and the bidirectional switch is not working.

2. The DC-DC converter as described in claim 1, characterized in that, The primary-side hybrid bridge rectifier module further includes: a fifth switch, the first end of which is connected to the first output terminal of the primary-side filter module; the second end of which is connected to the first end of a sixth switch; the second end of which is connected to the second output terminal of the primary-side filter module; the first end of a seventh switch is connected to the first output terminal of the primary-side filter module; the second end of the seventh switch is connected to the first end of an eighth switch; the second end of the eighth switch is connected to the second output terminal of the primary-side filter module; and the second end of the first inductor and the midpoint of the series connection of the seventh and eighth switches are connected to the secondary-side rectifier module.

3. The DC-DC converter as described in claim 2, characterized in that, The primary-side filtering module includes: a first capacitor, a first terminal of which is connected to the positive terminal of the input DC power, a second terminal of which is connected to the first terminal of a second capacitor, and a second terminal of which is connected to the negative terminal of the input DC power; the first terminal of the first capacitor serves as the first output terminal of the primary-side filtering module, the second terminal of the second capacitor serves as the second output terminal of the primary-side filtering module, and the midpoint of the series connection between the first capacitor and the second capacitor serves as the third output terminal of the primary-side filtering module.

4. The DC-DC converter as described in claim 2, characterized in that, The DC-DC converter also includes a resonant converter module, which adopts a series resonant structure.

5. The DC-DC converter as described in claim 2, characterized in that, The first switch, the second switch, the third switch, the fourth switch, the fifth switch, the sixth switch, the seventh switch, and the eighth switch are N-type metal-oxide-semiconductor field-effect transistors. The first terminal of the first switch, the second switch, the third switch, the fourth switch, the fifth switch, the sixth switch, the seventh switch, and the eighth switch is the drain, and the first terminal of the first switch, the second switch, the third switch, the fourth switch, the fifth switch, the sixth switch, the seventh switch, and the eighth switch is the source.

6. A control method for a DC-DC converter, applied to a DC-DC converter as described in any one of claims 2 to 5, characterized in that, include: The gain mode is selected according to the gain requirement; wherein, the gain modes include: low gain mode, medium gain mode and high gain mode. In low gain mode and medium gain mode, the fifth switch, the sixth switch, the seventh switch, the eighth switch, the third switch and the fourth switch are active, and the first switch and the second switch are inactive; in high gain mode, the fifth switch, the sixth switch, the seventh switch, the eighth switch, the first switch and the second switch are active, and the third switch and the fourth switch are inactive. Calculate the duty cycle for each gain mode; Determine the driving logic of the switches in the primary-side hybrid bridge rectifier module.

7. The control method for a DC-DC converter as described in claim 6, characterized in that, The calculation of the duty cycle in each gain mode includes: In low-gain and medium-gain modes, the gain curves of duty cycle versus corresponding gain are obtained by solving the time-domain equations, as shown below: Where Q represents the quality factor of the resonant converter module; The phase angle representing the resonant current; The phase angle representing the resonant voltage; This represents the normalized resonant capacitor voltage; This represents the normalized resonant current; The normalized resonant capacitor voltage at the initial moment is represented by M; the corresponding gain is represented by M. The time-domain equations are solved using numerical calculation methods to obtain the gain under different duty cycles and different loads. In high-gain mode, the duty cycle D is calculated by inversely based on the high gain. HG , means as follows: Among them, D HG Indicates the duty cycle in high-gain mode; M HG Indicates high gain.

8. The control method for a DC-DC converter as described in claim 6, characterized in that, The driving logic for determining the switches in the primary-side hybrid bridge rectifier module includes: in low-gain mode, during the positive half-cycle, pulse width modulation is used to control the primary-side hybrid bridge rectifier module, operating in the following four switching modes: In the first switching mode, within the range [t0-t1], the system enters the first resonance stage, during which the fifth switch, the third switch, and the fourth switch are turned on. The conduction time of the third switch and the fourth switch is 0.5T. s D LG Among them, T s D represents the switching period. LG Indicates the duty cycle in low gain mode; In the second switching mode, within [t1-t2], the third and fourth switches are turned off; In the third switching mode, within [t2-t3], the second resonance stage is entered, the seventh switch is turned on, and the resonant current is equal to the excitation current at time [t3-t4]. In the fourth switching mode, within [t4-t5], the fifth and seventh switches are turned off; During the negative half-cycle, the operating states of the fifth and sixth switches are opposite to those during the positive half-cycle, the operating states of the seventh and eighth switches are opposite to those during the positive half-cycle, and the operating states of the third and fourth switches are consistent with those during the positive half-cycle.

9. The control method for a DC-DC converter as described in claim 6, characterized in that, The determination of the driving logic for the switches in the primary-side hybrid bridge rectifier module further includes: in medium-gain mode, during the positive half-cycle, using pulse width modulation to control the primary-side hybrid bridge rectifier module, operating in the following four switching modes: In the first switching mode, within the range [t0-t1], the system enters the first resonance stage, during which the fifth and eighth switches are turned on, and the on-time of the fifth and eighth switches is 0.5T. s D MG Among them, T s D represents the switching period. MG Indicates the duty cycle in medium gain mode; In the second switching mode, within [t1-t2], the eighth switch is turned off; In the third switching mode, within [t2-t3], the second resonance stage is entered, and the third switch and the fourth switch are turned on. At time [t3-t4], the resonant current is equal to the excitation current. In the fourth switching mode, within [t4-t5], the fifth switch, the third switch, and the fourth switch are turned off; During the negative half-cycle, the operating states of the fifth and sixth switches are opposite to those during the positive half-cycle, the operating states of the seventh and eighth switches are opposite to those during the positive half-cycle, and the operating states of the third and fourth switches are consistent with those during the positive half-cycle.

10. The control method for a DC-DC converter as described in claim 6, characterized in that, The determination of the driving logic for the switches in the primary-side hybrid bridge rectifier module further includes: in high-gain mode, during the positive half-cycle, using pulse width modulation to control the primary-side hybrid bridge rectifier module, operating in the following four switching modes: In the first switching mode, within the range [t0-t1], the system enters a linear phase, during which the eighth switch and the first switch are turned on, and the on-time of the eighth switch and the first switch is 0.5T. s D HG Among them, T s D represents the switching period. HG Indicates the duty cycle in high-gain mode; In the second switching mode, within [t1-t2], the first switch is off and the fifth switch is on; In the third switching mode, within [t2-t3], the resonant current is equal to the excitation current; In the fourth switching mode, within [t3-t4], the fifth and eighth switches are turned off; During the negative half-cycle, the operating states of the fifth and sixth switches are opposite to those during the positive half-cycle, the operating states of the seventh and eighth switches are opposite to those during the positive half-cycle, and the operating states of the first and second switches are opposite to those during the positive half-cycle.

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