A four-switch buck-boost converter and control method

Abstract

The application provides a four-switch Buck-Boost converter and a control method. The four-switch Buck-Boost converter including an LC circuit and a Buck-Boost circuit is designed to have the advantages of the four-switch Buck-Boost and the LC circuit. The duty cycle is calculated by using the collected power supply voltage, the actual voltage of the output capacitor of the previous stage and the actual output voltage of the LC circuit, the duty cycle is obtained, and the PWM driving signal of each switch tube is generated according to the duty cycle. The conduction time of each switch in the four-switch Buck-Boost converter is controlled by the PWM driving signal to adjust the voltage gain of the four-switch Buck-Boost converter, so that the LC circuit can work in the voltage matching mode in a wide voltage range, the efficient gain conversion is realized, and the electrical isolation is provided while the power conversion efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of power electronic conversion technology, and in particular to a four-switch Buck-Boost converter and its control method. Background Technology

[0002] In recent years, with the development of the new energy industry, power electronic conversion devices have encountered greater challenges. More and more researchers have carried out a lot of research in pursuit of high power, high conversion efficiency and high power density of converters. As an important part of power conversion, DC-DC converters have also become the focus of research.

[0003] To improve the power conversion efficiency and voltage regulation capability of the converter, the following solutions have been proposed:

[0004] Option 1: Cascade a four-switch converter (Buck-Boost) with a resonant converter. The converter operates under the condition of voltage matching between the primary and secondary sides of the transformer to achieve electrical isolation and high-efficiency power conversion. A Boost converter is used for voltage boosting. This option is a two-pole topology, which has the advantages of simple structure and flexible control. However, the two-pole structure is prone to low power conversion efficiency.

[0005] Option 2: Connect the resonant converter and the four-switch converter in a series input and parallel output configuration. The resonant converter operates under voltage matching conditions, and the Boost circuit adjusts the duty cycle to regulate the voltage. This option has improved efficiency compared to the two-pole option, but its topology does not have electrical isolation. Summary of the Invention

[0006] This invention provides a four-switch Buck-Boost converter and its control method, the purpose of which is to improve power conversion efficiency while providing electrical isolation.

[0007] To achieve the above objectives, the present invention provides a four-switch Buck-Boost converter, including a power supply, an input capacitor, a Buck-Boost circuit, an LC resonant circuit, a load resistor, a first output capacitor, and a second output capacitor;

[0008] The Buck-Boost circuit includes a first switching circuit, a second switching circuit, a pre-stage output capacitor, and a first inductor;

[0009] The LC resonant circuit includes a third switching circuit, a fourth switching circuit, a fifth switching circuit, a sixth switching circuit, a resonant capacitor, an external leakage inductor, and a transformer;

[0010] The positive terminal of the power supply is connected to the first terminal of the input capacitor, the first terminal of the first switching circuit, the first terminal of the first output capacitor, and the first terminal of the load resistor, respectively.

[0011] The negative terminal of the power supply is connected to the second terminal of the input capacitor, the second terminal of the first switching circuit, the first terminal of the second switching circuit, the second terminal of the pre-stage output capacitor, the first terminal of the fifth switching circuit, the first terminal of the sixth switching circuit, the second terminal of the first output capacitor, the first terminal of the second output capacitor, the second terminal of the third switching circuit, and the second terminal of the fourth switching circuit, respectively.

[0012] The third terminal of the first switching circuit is connected to the second terminal of the second switching circuit through the first inductor;

[0013] The third terminal of the second switching circuit is connected to the first terminal of the pre-amplifier output capacitor, the first terminal of the third switching circuit, and the first terminal of the fourth switching circuit, respectively.

[0014] The third terminal of the third switching circuit is connected to the first terminal of the resonant capacitor, the second terminal of the resonant capacitor is connected to the first terminal of the external leakage inductor, and the second terminal of the external leakage inductor is connected to the first terminal of the transformer.

[0015] The third terminal of the fourth switch circuit is connected to the second terminal of the transformer;

[0016] The third terminal of the transformer is connected to the second terminal of the fifth switching circuit, and the fourth terminal of the transformer is connected to the second terminal of the sixth switching circuit.

[0017] The third terminal of the fifth switching circuit is connected to the third terminal of the sixth switching circuit, the second terminal of the second output capacitor, and the second terminal of the load resistor, respectively.

[0018] Furthermore, the first switching circuit includes a first switching transistor and a second switching transistor;

[0019] The drain of the first switching transistor is connected to the positive terminal of the power supply, the first terminal of the input capacitor, the first terminal of the first output capacitor, and the first terminal of the load resistor, respectively.

[0020] The source of the first switching transistor is connected to the drain of the second switching transistor and the first terminal of the first inductor, respectively.

[0021] The source of the second switching transistor is connected to the negative terminal of the power supply, the second terminal of the input capacitor, the first terminal of the second switching transistor, the second terminal of the pre-stage output capacitor, the first terminal of the fifth switching circuit, the first terminal of the sixth switching circuit, the second terminal of the first output capacitor, and the first terminal of the second output capacitor.

[0022] Furthermore, the second switching circuit includes a third switch and a fourth switch;

[0023] The source of the third switch is connected to the second terminal of the first inductor and the drain of the fourth switch.

[0024] The drain of the third switch is connected to the first terminal of the output capacitor of the pre-amplifier, the second terminal of the third switch, and the second terminal of the fourth switch, respectively.

[0025] The source of the fourth switching transistor is connected to the source of the second switching transistor, the second terminal of the pre-stage output capacitor, the first terminal of the fifth switching circuit, the first terminal of the sixth switching circuit, the second terminal of the first output capacitor, and the first terminal of the second output capacitor, respectively.

[0026] Furthermore, the third switching circuit includes a fifth switch and a sixth switch;

[0027] The drain of the fifth switching transistor is connected to the drain of the third switching transistor and the first terminal of the fourth switching circuit, respectively.

[0028] The source of the fifth switch is connected to the drain of the sixth switch and the first terminal of the resonant capacitor, respectively.

[0029] The source of the sixth switch is connected to the negative terminal of the power supply and the second terminal of the fourth switch circuit.

[0030] Furthermore, the fourth switching circuit includes the seventh and eighth switching transistors;

[0031] The drain of the seventh switch is connected to the drain of the fifth switch and the drain of the third switch, respectively.

[0032] The source of the seventh switch is connected to the drain of the eighth switch and the second terminal of the transformer, respectively.

[0033] The source of the eighth switch is connected to the source of the sixth switch and the negative terminal of the power supply, respectively.

[0034] Furthermore, the fifth switching circuit includes the first diode and the ninth switching transistor;

[0035] The cathode of the first diode is connected to the negative terminal of the power supply, the first terminal of the sixth switching circuit, the second terminal of the first output capacitor, and the first terminal of the second output capacitor, respectively.

[0036] The anode of the first diode is connected to the drain of the ninth switch and the third terminal of the transformer, respectively.

[0037] The source of the ninth switch is connected to the second terminal of the sixth switch circuit, the second terminal of the second output capacitor, and the second terminal of the load resistor, respectively.

[0038] Furthermore, a filter capacitor is also installed between the transformer and the fifth switch circuit;

[0039] The first terminal of the filter capacitor is connected to the third terminal of the transformer, and the second terminal of the filter capacitor is connected to the anode of the first diode and the drain of the ninth switching transistor.

[0040] Furthermore, the sixth switching circuit includes the second diode and the tenth switching transistor;

[0041] The cathode of the second diode is connected to the source of the fourth switch, the cathode of the first diode, the second terminal of the first output capacitor, and the first terminal of the second output capacitor, respectively.

[0042] The anode of the second diode is connected to the drain of the tenth switching transistor and the fourth terminal of the transformer, respectively.

[0043] The source of the tenth switch is connected to the source of the ninth switch, the second terminal of the second output capacitor, and the second terminal of the load resistor.

[0044] This invention also provides a control method for a four-switch Buck-Boost converter, applied to a four-switch Buck-Boost converter, the control method comprising:

[0045] Step 1: Collect the power supply voltage, the actual voltage of the pre-amplifier output capacitor, and the actual output voltage of the LC circuit;

[0046] Step 2: Adjust the initial duty cycle of the four-switch Buck-Boost converter using the power supply voltage, actual voltage, and actual output voltage, and generate a PWM drive signal for each switch based on the adjusted duty cycle.

[0047] Step 3: Control the on-time of each switch in the four-switch Buck-Boost converter using a PWM drive signal to adjust the voltage gain of the four-switch Buck-Boost converter.

[0048] Furthermore, step 2 includes:

[0049] The initial duty cycle is calculated based on the power supply voltage, the actual output voltage, and the transformer's turns ratio.

[0050] The desired voltage of the front-end output capacitor is obtained by calculating using the actual output voltage, the transformer's turns ratio, and the initial duty cycle.

[0051] The initial duty cycle is adjusted by inputting the difference between the desired voltage and the actual voltage into the first digital PI regulator to obtain the adjusted duty cycle.

[0052] The adjusted duty cycle is input into the PWM generation unit for processing to obtain the PWM drive signals for the first and second switching circuits.

[0053] The above-described solution of the present invention has the following beneficial effects:

[0054] This invention designs a four-switch Buck-Boost converter including an LC circuit and a Buck-Boost circuit, combining the advantages of both. Compared to existing technologies, this invention utilizes the acquired power supply voltage, the actual voltage of the front-stage output capacitor, and the actual output voltage of the LC circuit to adjust the initial duty cycle of the four-switch Buck-Boost converter, and generates a PWM drive signal for each switch based on the adjusted duty cycle. The PWM drive signal controls the on-time of each switch in the four-switch Buck-Boost converter to adjust the voltage gain, ensuring that the LC circuit can operate in voltage-matched mode over a wide voltage range, achieving high-efficiency gain conversion and improving power conversion efficiency while maintaining electrical isolation.

[0055] Other beneficial effects of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0056] Figure 1 This is a topology diagram of the four-switch Buck-Boost converter in an embodiment of the present invention;

[0057] Figure 2 This is a current waveform diagram of the converter in an embodiment of the present invention;

[0058] Figure 3 This is a flowchart of the control method for a four-switch Buck-Boost converter in an embodiment of the present invention. Detailed Implementation

[0059] To make the technical problems, solutions, and advantages of this invention clearer, a detailed description will be provided below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0060] In the description of this invention, it should be noted that the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0061] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a locking connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0062] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0063] This invention addresses existing problems by providing a four-switch Buck-Boost converter and its control method.

[0064] like Figure 1 As shown, an embodiment of the present invention provides a four-switch Buck-Boost converter, including a power supply V in Input capacitor C in Buck-Boost circuit, LC resonant circuit, load resistor R L First output capacitor C1, second output capacitor C2;

[0065] The Buck-Boost circuit includes a first switching circuit, a second switching circuit, and a pre-stage output capacitor C. B First inductor L f ;

[0066] The LC resonant circuit includes a third switching circuit, a fourth switching circuit, a fifth switching circuit, a sixth switching circuit, and a resonant capacitor C. r External leakage inductor L r Transformer T;

[0067] Power supply V in The positive terminals are respectively connected to the input capacitor C. in The first terminal, the first terminal of the first switching circuit, the first terminal of the first output capacitor C1, and the load resistor R L The first end is connected;

[0068] Power supply V in The negative terminals are respectively connected to the input capacitor C. in The second terminal, the second terminal of the first switching circuit, the first terminal of the second switching circuit, and the output capacitor C of the pre-amplifier. B The second terminal, the first terminal of the fifth switch circuit, the first terminal of the sixth switch circuit, the second terminal of the first output capacitor C1, the first terminal of the second output capacitor C2, the second terminal of the third switch circuit, and the second terminal of the fourth switch circuit are connected.

[0069] The third terminal of the first switching circuit is connected to the first inductor L. f Connect to the second terminal of the second switching circuit;

[0070] The third terminal of the second switching circuit is connected to the output capacitor C of the previous stage. B The first end of the first terminal of the third switch circuit and the first end of the fourth switch circuit are connected;

[0071] The third terminal of the third switching circuit is connected to the resonant capacitor C. r The first terminal is connected to the resonant capacitor C. r The second terminal is connected to the external leakage inductor L r The first connection is an external leakage inductor L. r The second end is connected to the first end of transformer T;

[0072] The third terminal of the fourth switch circuit is connected to the second terminal of transformer T;

[0073] The third terminal of transformer T is connected to the second terminal of the fifth switching circuit, and the fourth terminal of transformer T is connected to the second terminal of the sixth switching circuit.

[0074] The third terminal of the fifth switching circuit is connected to the third terminal of the sixth switching circuit, the second terminal of the second output capacitor C2, and the load resistor R, respectively. L The second end is connected.

[0075] In this embodiment of the invention, the transformer T includes a primary winding and a secondary winding. The ratio of the primary winding to the secondary winding is the transformer ratio of the transformer T, that is, the transformer ratio = number of turns of the primary winding / number of turns of the secondary winding.

[0076] In this embodiment of the invention, the LC resonant circuit undertakes all the energy transfer tasks, and the primary side is composed of a third switching circuit and a fourth switching circuit. The first terminals of both of these switching circuits are connected to the power supply V. in The negative terminal is directly connected, and the first switching loop in the Buck-Boost circuit is directly connected to the power supply V. in Since they are connected, from the perspective of energy transmission, the total energy is divided into two parts during transmission. The Buck-Boost circuit only undertakes part of the power. Therefore, the Buck-Boost circuit has the characteristic of partial power transmission, which can transmit only a part of the system output power, which is beneficial to improving the energy conversion efficiency of the converter.

[0077] Specifically, the first switching circuit includes a first switching transistor S1 and a second switching transistor S2;

[0078] The drain of the first switching transistor S1 is connected to the power supply V. in Positive terminal, input capacitor C inThe first terminal, the first terminal of the first output capacitor C1, and the load resistor R L The first end is connected;

[0079] The source of the first switch S1 is connected to the drain of the second switch S2 and the first inductor L, respectively. f The first end is connected;

[0080] The source of the second switch S2 is connected to the power supply V. in negative terminal, input capacitor C in The second terminal, the first terminal of the second switch S2, and the output capacitor C of the pre-amplifier stage. B The second terminal, the first terminal of the fifth switch circuit, the first terminal of the sixth switch circuit, the second terminal of the first output capacitor C1, and the first terminal of the second output capacitor C2 are connected.

[0081] Specifically, the second switching circuit includes a third switch S3 and a fourth switch S4;

[0082] The source of the third switch S3 is connected to the first inductor L. f The second terminal and the drain of the fourth switching transistor S4 are connected;

[0083] The drain of the third switch S3 is connected to the output capacitor C of the previous stage. B The first end of the third switch S3 and the second end of the fourth switch S4 are connected;

[0084] The source of the fourth switch S4 is connected to the source of the second switch S2 and the output capacitor C of the preceding stage, respectively. B The second terminal, the first terminal of the fifth switch circuit, the first terminal of the sixth switch circuit, the second terminal of the first output capacitor C1, and the first terminal of the second output capacitor C2 are connected.

[0085] Specifically, the third switching circuit includes the fifth switch S5 and the sixth switch S6;

[0086] The drain of the fifth switch S5 is connected to the drain of the third switch S3 and the first terminal of the fourth switch circuit, respectively.

[0087] The source of the fifth switch S5 is connected to the drain of the sixth switch S6 and the resonant capacitor C, respectively. r The first end is connected;

[0088] The source of the sixth switch S6 is connected to the power supply V. in The negative terminal is connected to the second terminal of the fourth switching circuit.

[0089] In this embodiment of the invention, the intermediate potential between the fifth switch S5 and the sixth switch S6 is the first intermediate potential, and the first center potential is defined as point a.

[0090] Specifically, the fourth switching circuit includes the seventh switch S7 and the eighth switch S8;

[0091] The drain of the seventh switch S7 is connected to the drain of the fifth switch S5 and the drain of the third switch S3, respectively.

[0092] The source of the seventh switch S7 is connected to the drain of the eighth switch S8 and the second terminal of the transformer T, respectively.

[0093] The source of the eighth switch S8 is connected to the source of the sixth switch S6 and the power supply V, respectively. in The negative terminal connection.

[0094] In this embodiment of the invention, the intermediate potential between the seventh switch S7 and the eighth switch S8 is the second intermediate potential, which is defined as point b in this embodiment of the invention.

[0095] Specifically, the fifth switching circuit includes the first diode D1 and the ninth switching transistor S9;

[0096] The cathode of the first diode D1 is connected to the power supply V. in The negative terminal, the first terminal of the sixth switching circuit, the second terminal of the first output capacitor C1, and the first terminal of the second output capacitor C2 are connected;

[0097] The anode of the first diode D1 is connected to the drain of the ninth switch S9 and the third terminal of the transformer T, respectively.

[0098] The source of the ninth switch S9 is connected to the second terminal of the sixth switch circuit, the second terminal of the second output capacitor C2, and the load resistor R, respectively. L The second end is connected.

[0099] In this embodiment of the invention, the intermediate potential between the first diode D1 and the ninth switch S9 is the third intermediate potential, which is defined as point c in this embodiment of the invention.

[0100] Specifically, a filter capacitor C is also installed between the transformer T and the fifth switch circuit. s ;

[0101] Filter capacitor C s The first terminal is connected to the third terminal of transformer T, and the filter capacitor C... s The second end is connected to the anode of the first diode D1 and the drain of the ninth switch S9, respectively.

[0102] Furthermore, the sixth switching circuit includes the second diode D2 and the tenth switching transistor S. 10 ;

[0103] The cathode of the second diode D2 is connected to the source of the fourth switch S4, the cathode of the first diode D1, the second terminal of the first output capacitor C1, and the first terminal of the second output capacitor C2, respectively.

[0104] The anode of the second diode D2 is connected to the tenth switch S. 10 The drain of the transformer is connected to the fourth terminal of the transformer T.

[0105] Tenth switch S 10 The source of each transistor is connected to the source of the ninth switch, the second terminal of the second output capacitor C2, and the load resistor R, respectively. L The second end is connected.

[0106] In this embodiment of the invention, the second diode D2 and the tenth switch S 10 The intermediate potential is the fourth intermediate potential, and in this embodiment of the invention, the fourth intermediate potential is defined as point d.

[0107] Specifically, the gates of the first switch S1, the second switch S2, the third switch S3, the fourth switch S4, the fifth switch S5, the sixth switch S6, the seventh switch S7, the eighth switch S8, the ninth switch S9, and the tenth switch S... 10 The gates of all transistors are connected to an external controller, which controls the on / off state of each transistor. The gate of the first transistor S1 receives a first adjustment signal from the external controller. This first adjustment signal adjusts the ratio of the on-time to the switching period of the first transistor S1, controlling the output capacitor C of the preceding stage. B The voltage at both ends changes the voltage between the first intermediate potential point a and the second intermediate potential point b. The amplitude can be adjusted to regulate the voltage gain, thereby increasing the efficiency of current waveform transformation.

[0108] Specifically, the first switch S1, the second switch S2, the third switch S3, the fourth switch S4, the fifth switch S5, the sixth switch S6, the seventh switch S7, the eighth switch S8, the ninth switch S9, and the tenth switch S1... 10 All use N-type MOS transistors with anti-parallel diodes and parasitic capacitance.

[0109] like Figure 2 As shown, the operation of the four-switch Buck-Boost converter provided in this embodiment of the invention is as follows:

[0110] At time t0, the first switch S1 turns on with zero voltage, the third switch S3 turns on with zero voltage, and the fifth switch S5, the seventh switch S7, and the tenth switch S8 turn on with zero voltage. 10 Zero-current turn-on, first inductor L fcurrent Linear increase, while external leakage inductance L r current Decreases sinusoidally in the negative direction;

[0111] At time t1, the seventh switch S7 and the tenth switch S 10 Zero-current turn-off, first inductor L f current Maintaining linear growth in the positive direction, external leakage inductance L r current Keep it at zero;

[0112] At time t2, when the first switch S1 and the fourth switch S4 are turned off, the first inductor L... f The current will charge the capacitors of the first switch S1 and the fourth switch S4, and discharge the parasitic capacitances in the second switch S2 and the third switch S3.

[0113] At time t3, the second switch S2 and the third switch S3 are turned on with zero voltage, and the sixth switch S6, the seventh switch S7, and the ninth switch S9 are turned on with zero current. The first inductor L... f current Linear decrease, external leakage inductance L r current It rises sinusoidally in the positive direction;

[0114] At time t4, the external leakage inductance L r When the current is zero, the sixth switch S6, the seventh switch S7, and the ninth switch S9 are turned off with zero current, and the first inductor L... f current Linear decrease.

[0115] In such Figure 2 In the current waveform diagram shown, t on the horizontal axis represents unit time, and the value of t is t0, t1, ..., t4. DTs represents the conduction time of the switching transistor.

[0116] like Figure 3 As shown, the present invention also provides a control method for a four-switch Buck-Boost converter, applied to a four-switch Buck-Boost converter, the control method comprising:

[0117] Step 1: Collect the power supply voltage, the actual voltage of the pre-amplifier output capacitor, and the actual output voltage of the LC circuit;

[0118] Step 2: Adjust the initial duty cycle of the four-switch Buck-Boost converter using the power supply voltage, actual voltage, and actual output voltage, and generate a PWM drive signal for each switch based on the adjusted duty cycle.

[0119] Step 3: Control the on-time of each switch in the four-switch Buck-Boost converter using a PWM drive signal to adjust the voltage gain of the four-switch Buck-Boost converter.

[0120] It should be noted that in the embodiments of the present invention, the power supply voltage V1 and the actual voltage V of the front-end output capacitor are... B The actual output voltage V2 of the LC circuit is acquired by a voltage sensor and input to an external controller, which is a DSP controller, used to control the four-switch Buck-Boost converter.

[0121] Specifically, step 2 includes:

[0122] The initial duty cycle is calculated based on the power supply voltage, the actual output voltage, and the transformer's turns ratio.

[0123] The desired voltage of the front-end output capacitor is obtained by calculating using the actual output voltage, the transformer's turns ratio, and the initial duty cycle.

[0124] The initial duty cycle is adjusted by inputting the difference between the desired voltage and the actual voltage into the first digital PI regulator to obtain the adjusted duty cycle.

[0125] The adjusted duty cycle is input into the PWM generation unit for processing to obtain the PWM drive signals for the first and second switching circuits.

[0126] Specifically, the expression for calculating the initial duty cycle based on the power supply voltage, actual output voltage, and transformer turns ratio is as follows:

[0127] ;

[0128] in, Indicates the power supply voltage. Indicates the actual output voltage. This indicates the transformer's turns ratio. This indicates the initial duty cycle.

[0129] Specifically, using the actual output voltage, the transformer's turns ratio, and the initial duty cycle, the expression for calculating the desired voltage of the front-stage output capacitor is as follows:

[0130] ;

[0131] in, This represents the desired voltage of the output capacitor in the preceding stage.

[0132] In this embodiment of the invention, the external controller can directly output the generated PWM drive signal to the gate of the switching transistor in the four-switch Buck-Boost converter to control the switching transistor's on / off state.

[0133] In the embodiment of the present invention, the conduction of the two switches on the same bridge arm of the four-switch Buck-Boost circuit is complementary. The driving signals of the fifth and seventh switches, and the sixth and eighth switches in the LC resonant circuit are the same. The control signals of the ninth and tenth switches are both duty cycles, that is, half of the resonant period.

[0134] In this embodiment of the invention, the expression for the voltage gain of the four-switch Buck-Boost converter topology is:

[0135] ;

[0136] in, Indicates voltage gain. This indicates the duty cycle of the adjusted four-switch Buck-Boost circuit.

[0137] To verify its feasibility, the embodiments of the present invention refer to, for example... Figure 1 The topology of the four-switch Buck-Boost converter shown was used to build a 400W prototype. The input voltage was 20V~120V and the output voltage was 48V. The drive signals for the LC resonant circuit and the Buck-Boost circuit were generated by an external controller, such as a DSP controller of model TMS320F28377S. Under these experimental conditions, the four-switch Buck-Boost converter could operate normally in a closed loop under its control method, achieving both electrical isolation and efficient power conversion. Furthermore, the converter prototype could operate normally under different input voltages and loads, indicating that the four-switch Buck-Boost converter provided by this invention can overcome the shortcomings of the prior art and has applicability under diverse operating conditions.

[0138] This invention, through the design of a four-switch Buck-Boost converter including an LC circuit and a Buck-Boost circuit, combines the advantages of both four-switch Buck-Boost and LC circuits. Compared with existing technologies, this invention calculates the duty cycle using the acquired power supply voltage, the actual voltage of the front-stage output capacitor, and the actual output voltage of the LC circuit. Based on the duty cycle, a PWM drive signal is generated for each switch. The PWM drive signal controls the on-time of each switch in the four-switch Buck-Boost converter to adjust the voltage gain, ensuring that the LC circuit can operate in voltage-matched mode over a wide voltage range, achieving high-efficiency gain conversion and improving power conversion efficiency while maintaining electrical isolation.

[0139] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A four-switch Buck-Boost converter, characterized in that, Includes power supply, input capacitor, Buck-Boost circuit, LC resonant circuit, load resistor, first output capacitor, and second output capacitor; The Buck-Boost circuit includes a first switching circuit, a second switching circuit, a pre-stage output capacitor, and a first inductor; The LC resonant circuit includes a third switching circuit, a fourth switching circuit, a fifth switching circuit, a sixth switching circuit, a resonant capacitor, an external leakage inductor, and a transformer; The positive terminal of the power supply is connected to the first terminal of the input capacitor, the first terminal of the first switching circuit, the first terminal of the first output capacitor, and the first terminal of the load resistor, respectively. The negative terminal of the power supply is connected to the second terminal of the input capacitor, the second terminal of the first switching circuit, the first terminal of the second switching circuit, the second terminal of the pre-stage output capacitor, the first terminal of the fifth switching circuit, the first terminal of the sixth switching circuit, the second terminal of the first output capacitor, the first terminal of the second output capacitor, the second terminal of the third switching circuit, and the second terminal of the fourth switching circuit, respectively. The third terminal of the first switching circuit is connected to the second terminal of the second switching circuit through the first inductor; The third terminal of the second switching circuit is connected to the first terminal of the pre-stage output capacitor, the first terminal of the third switching circuit, and the first terminal of the fourth switching circuit, respectively. The third terminal of the third switching circuit is connected to the first terminal of the resonant capacitor, the second terminal of the resonant capacitor is connected to the first terminal of the external leakage inductor, and the second terminal of the external leakage inductor is connected to the first terminal of the transformer. The third terminal of the fourth switch circuit is connected to the second terminal of the transformer; The third terminal of the transformer is connected to the second terminal of the fifth switching circuit, and the fourth terminal of the transformer is connected to the second terminal of the sixth switching circuit. The third terminal of the fifth switching circuit is connected to the third terminal of the sixth switching circuit, the second terminal of the second output capacitor, and the second terminal of the load resistor, respectively.

2. The four-switch Buck-Boost converter according to claim 1, characterized in that, The first switching circuit includes a first switching transistor and a second switching transistor; The drain of the first switching transistor is connected to the positive terminal of the power supply, the first terminal of the input capacitor, the first terminal of the first output capacitor, and the first terminal of the load resistor, respectively. The source of the first switching transistor is connected to the drain of the second switching transistor and the first terminal of the first inductor, respectively. The source of the second switching transistor is connected to the negative terminal of the power supply, the second terminal of the input capacitor, the first terminal of the second switching transistor, the second terminal of the pre-stage output capacitor, the first terminal of the fifth switching circuit, the first terminal of the sixth switching circuit, the second terminal of the first output capacitor, and the first terminal of the second output capacitor.

3. The four-switch Buck-Boost converter according to claim 2, characterized in that, The second switching circuit includes a third switch and a fourth switch; The source of the third switch is connected to the second terminal of the first inductor and the drain of the fourth switch. The drain of the third switching transistor is connected to the first terminal of the pre-stage output capacitor, the second terminal of the third switching transistor, and the second terminal of the fourth switching transistor, respectively. The source of the fourth switching transistor is connected to the source of the second switching transistor, the second terminal of the pre-stage output capacitor, the first terminal of the fifth switching circuit, the first terminal of the sixth switching circuit, the second terminal of the first output capacitor, and the first terminal of the second output capacitor.

4. The four-switch Buck-Boost converter according to claim 3, characterized in that, The third switching circuit includes a fifth switching transistor and a sixth switching transistor; The drain of the fifth switching transistor is connected to the drain of the third switching transistor and the first terminal of the fourth switching circuit, respectively. The source of the fifth switch is connected to the drain of the sixth switch and the first terminal of the resonant capacitor, respectively. The source of the sixth switch is connected to the negative terminal of the power supply and the second terminal of the fourth switch circuit, respectively.

5. The four-switch Buck-Boost converter according to claim 4, characterized in that, The fourth switching circuit includes a seventh switching transistor and an eighth switching transistor; The drain of the seventh switch is connected to the drain of the fifth switch and the drain of the third switch, respectively. The source of the seventh switch is connected to the drain of the eighth switch and the second terminal of the transformer, respectively. The source of the eighth switch is connected to the source of the sixth switch and the negative terminal of the power supply, respectively.

6. The four-switch Buck-Boost converter according to claim 5, characterized in that, The fifth switching circuit includes a first diode and a ninth switching transistor; The cathode of the first diode is connected to the negative terminal of the power supply, the first terminal of the sixth switching circuit, the second terminal of the first output capacitor, and the first terminal of the second output capacitor, respectively. The anode of the first diode is connected to the drain of the ninth switch and the third terminal of the transformer, respectively. The source of the ninth switch is connected to the second terminal of the sixth switch circuit, the second terminal of the second output capacitor, and the second terminal of the load resistor, respectively.

7. The four-switch Buck-Boost converter according to claim 6, characterized in that, A filter capacitor is also provided between the transformer and the fifth switch circuit; The first end of the filter capacitor is connected to the third end of the transformer, and the second end of the filter capacitor is connected to the anode of the first diode and the drain of the ninth switching transistor.

8. The four-switch Buck-Boost converter according to claim 6, characterized in that, The sixth switching circuit includes a second diode and a tenth switching transistor; The cathode of the second diode is connected to the source of the fourth switch, the cathode of the first diode, the second terminal of the first output capacitor, and the first terminal of the second output capacitor, respectively. The anode of the second diode is connected to the drain of the tenth switching transistor and the fourth terminal of the transformer, respectively. The source of the tenth switch is connected to the source of the ninth switch, the second terminal of the second output capacitor, and the second terminal of the load resistor.

9. A control method for a four-switch Buck-Boost converter, characterized in that, The control method, applied to the four-switch Buck-Boost converter as described in any one of claims 1-8, comprises: Step 1: Collect the power supply voltage, the actual voltage of the pre-amplifier output capacitor, and the actual output voltage of the LC circuit; Step 2: Adjust the initial duty cycle of the four-switch Buck-Boost converter using the power supply voltage, the actual voltage, and the actual output voltage, and generate a PWM drive signal for each switch based on the adjusted duty cycle; Step 3: Control the conduction time of each switch in the four-switch Buck-Boost converter using the PWM drive signal to adjust the voltage gain of the four-switch Buck-Boost converter.

10. The control method for a four-switch Buck-Boost converter according to claim 9, characterized in that, Step 2 includes: The initial duty cycle is calculated based on the power supply voltage, the actual output voltage, and the transformer's turns ratio. The desired voltage of the front-end output capacitor is obtained by calculating using the actual output voltage, the transformer's turns ratio, and the initial duty cycle. The difference between the desired voltage and the actual voltage is input into a first digital PI regulator to adjust the initial duty cycle, thereby obtaining the adjusted duty cycle. The adjusted duty cycle is input into the PWM generation unit for processing to obtain the PWM drive signals for the first switching circuit and the second switching circuit.

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