Quasi-monopole four-switch Buck-Boost converter and control method

Abstract

The invention relates to the technical field of power electronic conversion, and provides a quasi-monopole type four-switch Buck-Boost converter and a control method. The quasi-monopole four-switch Buck-Boost converter comprises a Buck-Boost circuit, an LC resonance circuit, a power supply, a load resistor and an output capacitor, and the Buck-Boost circuit comprises a first switch loop, a second switch loop, a preceding stage output capacitor and a first inductor. The LC resonant circuit comprises a third switch loop, a fourth switch loop, a fifth switch loop, a sixth switch loop, a resonant capacitor, an external leakage inductor and a transformer. According to the quasi-monopole type four-switch Buck-Boost converter provided by the invention, the electric energy conversion efficiency can be improved while electric isolation is realized.

Description

Technical Field

[0001] This application relates to the field of power electronic conversion technology, and in particular to a quasi-unipolar 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, and more and more researchers have conducted extensive research to pursue high power, high conversion efficiency, and high power density in converters. DC-DC converters, as a crucial component in power conversion, have also become a key focus of research.

[0003] To improve the power conversion efficiency and voltage regulation capability of the converter, the following solutions have been proposed: Option 1: Cascade a four-switch converter (Buck-Boost) and a resonant converter (LC, Inductor-Capacitor-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, and 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, but the two-pole structure leads to lower power conversion efficiency.

[0004] Option 2: Connect the resonant converter and the four-switch Buck-Boost 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.

[0005] This shows that there is currently a problem where the power conversion efficiency and electrical isolation of converters cannot be simultaneously achieved. Summary of the Invention

[0006] This application provides a quasi-unipolar four-switch Buck-Boost converter and its control method, which can solve the problem of the inability to simultaneously achieve power conversion efficiency and electrical isolation in the converter.

[0007] In a first aspect, embodiments of this application provide a quasi-unipolar four-switch Buck-Boost converter, including: a Buck-Boost circuit, an LC resonant circuit, a power supply, a load resistor, and an 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 first switching circuit and the first terminal of the fourth switching circuit, respectively. The negative terminal of the power supply is connected to the second terminal of the first switching circuit, the second terminal of the second switching circuit, the second terminal of the third switching circuit, the second terminal of the fourth switching circuit, and the second terminal of the pre-amplifier output capacitor, respectively. The first terminal of the first inductor is connected to the third terminal of the first switching circuit, and the second terminal of the first inductor is connected to the third terminal of the second switching circuit. The first terminal of the second switching circuit is connected to the first terminal of the pre-amplifier output capacitor and the first terminal of the third switching circuit, respectively. The first terminal of the resonant capacitor is connected to the third terminal of the third switching circuit. The second terminal of the resonant capacitor is connected to the first terminal of the external leakage inductor. The second terminal of the external leakage inductor is connected to the first terminal of the primary side of the transformer. The second terminal of the primary side of the transformer is connected to the third terminal of the fourth switching circuit. The first terminal of the secondary side of the transformer is connected to the third terminal of the fifth switching circuit. The first terminal of the fifth switching circuit is connected to the first terminal of the sixth switching circuit, the first terminal of the output capacitor, and the first terminal of the load resistor. The second terminal of the fifth switching circuit is connected to the second terminal of the sixth switching circuit, the second terminal of the output capacitor, and the second terminal of the load resistor. The second terminal of the secondary side of the transformer is connected to the third terminal of the sixth switching circuit.

[0008] Optionally, the first switching circuit includes a first switching transistor and a second switching transistor; The drain of the first switch is the first terminal of the first switch circuit, the source of the second switch is the second terminal of the first switch circuit, and the source of the first switch and the drain of the second switch are the third terminal of the first switch. The second switching circuit includes a third switching transistor and a fourth switching transistor; The drain of the third switch is the first terminal of the second switching circuit, the source of the fourth switch is the second terminal of the second switching circuit, and the source of the third switch and the drain of the fourth switch are the third terminal of the second switching circuit.

[0009] Optionally, the third switching circuit includes a fifth switch and a sixth switch; The drain of the fifth switch is the first terminal of the third switch circuit, the source of the sixth switch is the second terminal of the third switch circuit, and the source of the fifth switch and the drain of the sixth switch are the third terminal of the third switch circuit. The fourth switching circuit includes the seventh and eighth switching transistors; The drain of the seventh switch is the first terminal of the fourth switching circuit, the source of the eighth switch is the second terminal of the fourth switching circuit, and the source of the seventh switch and the drain of the eighth switch are the third terminals of the fourth switching circuit.

[0010] Optionally, the fifth switching circuit includes a first diode and a ninth switching transistor; The drain of the first diode is the first terminal of the fifth switching circuit, the source of the ninth switching transistor is the second terminal of the fifth switching circuit, and the source of the first diode and the drain of the ninth switching transistor are the third terminal of the fifth switching circuit. The sixth switching circuit includes the second diode and the tenth switching transistor; The drain of the second diode is the first terminal of the sixth switching circuit, the source of the tenth switching transistor is the second terminal of the sixth switching circuit, and the source of the second diode and the drain of the tenth switching transistor are the third terminal of the sixth switching circuit.

[0011] Optionally, the transformer may include an ideal transformer and stray capacitance; The first end of the primary side of the ideal transformer is the first end of the primary side of the transformer, the second end of the primary side of the ideal transformer is the second end of the primary side of the transformer, the second end of the stray capacitance is the first end of the secondary side of the transformer, and the second end of the secondary side of the ideal transformer is the second end of the secondary side of the transformer. The first terminal of the stray capacitor is connected to the first terminal of the secondary side of the ideal transformer.

[0012] Secondly, embodiments of this application provide a control method for a quasi-unipolar four-switch Buck-Boost converter, the control method comprising: Obtain the output voltage of the quasi-unipolar four-switch Buck-Boost converter and the transformer ratio in the quasi-unipolar four-switch Buck-Boost converter; Calculate the expected voltage of the front-stage output capacitor in a quasi-unipolar four-switch Buck-Boost converter based on the output voltage and the transformation ratio; The duty cycle of the first switch in the quasi-unipolar four-switch Buck-Boost converter is generated based on the desired voltage. The unipolar four-switch Buck-Boost converter is controlled based on the duty cycle of the first switch.

[0013] Optionally, the expected voltage of the front-stage output capacitor in the quasi-unipolar four-switch Buck-Boost converter is calculated based on the output voltage and the transformation ratio, including: Through the formula: ; Calculate the expected voltage of the preamp output capacitor. ; in, This represents the duty cycle of a given Buck-Boost circuit. Indicates the duty cycle of the transformer. This indicates the output voltage.

[0014] Optionally, the duty cycle of the first switch in the quasi-unipolar four-switch Buck-Boost converter is generated based on the desired voltage, including: Calculate the difference between the actual voltage and the desired voltage of the output from the previous stage, and generate the duty cycle of the first switching transistor based on the difference.

[0015] Optionally, the unipolar four-switch Buck-Boost converter can be controlled according to the duty cycle of the first switch, including: The PWM drive signal for each switch in the first and second switching circuits of the quasi-unipolar four-switch Buck-Boost converter is generated based on the duty cycle of the first switch. The switching transistors are controlled to turn on and off based on the PWM drive signal of each transistor.

[0016] The above-mentioned solution in this application has the following beneficial effects: In the embodiments of this application, the quasi-unipolar four-switch Buck-Boost converter includes: a Buck-Boost circuit, an LC resonant circuit, a power supply, a load resistor, and an 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. By acquiring the power supply voltage, the actual voltage of the pre-stage output capacitor, and the actual output voltage of the LC resonant circuit, the PWM drive signal for each switch is calculated. The conduction time of each switch in the control circuit is adjusted by using the PWM drive signal of each switch to regulate the voltage gain of the quasi-unipolar four-switch Buck-Boost converter. This ensures that the LC circuit can operate in a voltage-matched mode within a wide voltage range, achieving high-efficiency gain conversion and improving power conversion efficiency while providing electrical isolation.

[0017] Other beneficial effects of this application will be described in detail in the following detailed description section. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a topology diagram of a quasi-unipolar four-switch Buck-Boost converter provided in an embodiment of this application; Figure 2 Waveform diagram of a quasi-unipolar four-switch Buck-Boost converter provided in an embodiment of this application; Figure 3 A flowchart of a control method for a quasi-unipolar four-switch Buck-Boost converter provided in an embodiment of this application; Figure 4 This is a schematic diagram of steady-state output provided in an embodiment of this application; Figure 5 This is a schematic diagram of the zero-voltage turn-on of the first switching transistor provided in an embodiment of this application. Detailed Implementation

[0020] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0021] It should be understood that, when used in this application specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.

[0022] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0023] As used in this application specification and the appended claims, the term "if" may be interpreted, depending on the context, as "when," "once," "in response to determination," or "in response to detection." Similarly, the phrase "if determined" or "if detected [the described condition or event]" may be interpreted, depending on the context, as meaning "once determined," "in response to determination," "once detected [the described condition or event]," or "in response to detection [the described condition or event]."

[0024] Furthermore, in the description of this application and the appended claims, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0025] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0026] To address the issue of existing converters failing to simultaneously achieve high power conversion efficiency and electrical isolation, this application provides a quasi-unipolar four-switch Buck-Boost converter and its control method. The quasi-unipolar four-switch Buck-Boost converter includes: a Buck-Boost circuit, an LC resonant circuit, a power supply, a load resistor, and an 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. By acquiring the power supply voltage, the actual voltage of the pre-stage output capacitor, and the actual output voltage of the LC resonant circuit, the PWM drive signal for each switch is calculated. The conduction time of each switch in the control circuit is adjusted using the PWM drive signal of each switch, thereby regulating the voltage gain of the quasi-unipolar four-switch Buck-Boost converter. This ensures that the LC circuit can operate in a voltage-matched mode over a wide voltage range, achieving high-efficiency gain conversion and improving power conversion efficiency while maintaining electrical isolation.

[0027] The structure of the quasi-unipolar four-switch Buck-Boost converter provided in this application will be described exemplarily below.

[0028] like Figure 1 As shown, the quasi-unipolar four-switch Buck-Boost converter includes a Buck-Boost circuit, an LC resonant circuit, and a power supply (…). Figure 1 In ), load resistor ( Figure 1 In ), output capacitor ( Figure 1 In ).

[0029] The Buck-Boost circuit includes a first switching circuit, a second switching circuit, and a pre-amplifier output capacitor. Figure 1In ), First Inductor ( Figure 1 In ).

[0030] 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. Figure 1 In ), external leakage inductor ( Figure 1 In ),transformer.

[0031] The positive terminal of the power supply is connected to the first terminal of the first switching circuit and the first terminal of the fourth switching circuit, respectively. The negative terminal of the power supply is connected to the second terminal of the first switching circuit, the second terminal of the second switching circuit, the second terminal of the third switching circuit, the second terminal of the fourth switching circuit, and the second terminal of the pre-amplifier output capacitor, respectively. The first terminal of the first inductor is connected to the third terminal of the first switching circuit, and the second terminal of the first inductor is connected to the third terminal of the second switching circuit. The first terminal of the second switching circuit is connected to the first terminal of the pre-amplifier output capacitor and the first terminal of the third switching circuit, respectively. The first terminal of the resonant capacitor is connected to the third terminal of the third switching circuit. The second terminal of the resonant capacitor is connected to the first terminal of the external leakage inductor. The second terminal of the external leakage inductor is connected to the first terminal of the primary side of the transformer. The second terminal of the primary side of the transformer is connected to the third terminal of the fourth switching circuit. The first terminal of the secondary side of the transformer is connected to the third terminal of the fifth switching circuit. The first terminal of the fifth switching circuit is connected to the first terminal of the sixth switching circuit, the first terminal of the output capacitor, and the first terminal of the load resistor. The second terminal of the fifth switching circuit is connected to the second terminal of the sixth switching circuit, the second terminal of the output capacitor, and the second terminal of the load resistor. The second terminal of the secondary side of the transformer is connected to the third terminal of the sixth switching circuit.

[0032] The first switching circuit includes the first switching transistor ( Figure 1 In ) and second switching transistor ( Figure 1 In The drain of the first switch is the first terminal of the first switching circuit, the source of the second switch is the second terminal of the first switching circuit, and the source of the first switch and the drain of the second switch are the third terminal of the first switch.

[0033] The second switching circuit includes a third switching transistor ( Figure 1 In ) and the fourth switch ( Figure 1 In The drain of the third switch is the first terminal of the second switching circuit, the source of the fourth switch is the second terminal of the second switching circuit, and the source of the third switch and the drain of the fourth switch are the third terminal of the second switching circuit.

[0034] The third switching circuit includes the fifth switching transistor ( Figure 1 In ) and the sixth switch ( Figure 1 In The drain of the fifth switch is the first terminal of the third switching circuit, the source of the sixth switch is the second terminal of the third switching circuit, and the source of the fifth switch and the drain of the sixth switch are the third terminal of the third switching circuit.

[0035] The fourth switching circuit includes the seventh switching transistor ( Figure 1 In ) and the eighth switch ( Figure 1 In The drain of the seventh switch is the first terminal of the fourth switching circuit, the source of the eighth switch is the second terminal of the fourth switching circuit, and the source of the seventh switch and the drain of the eighth switch are the third terminals of the fourth switching circuit.

[0036] The fifth switching circuit includes the first diode ( Figure 1 In ) and the ninth switch ( Figure 1 In The drain of the first diode is the first terminal of the fifth switching circuit, the source of the ninth switching transistor is the second terminal of the fifth switching circuit, and the source of the first diode and the drain of the ninth switching transistor are the third terminal of the fifth switching circuit.

[0037] The sixth switching circuit includes the second diode ( Figure 1 In ) and the tenth switch ( Figure 1 In The drain of the second diode is the first terminal of the sixth switching circuit, the source of the tenth switching transistor is the second terminal of the sixth switching circuit, and the source of the second diode and the drain of the tenth switching transistor are the third terminal of the sixth switching circuit.

[0038] Transformers include ideal transformers ( Figure 1 In The ratio of the number of turns on the primary side to the number of turns on the secondary side is ) and stray capacitance ( Figure 1 In The first end of the primary side of the ideal transformer is the first end of the primary side of the transformer, the second end of the primary side of the ideal transformer is the second end of the primary side of the transformer, the second end of the stray capacitor is the first end of the secondary side of the transformer, and the second end of the secondary side of the ideal transformer is the second end of the secondary side of the transformer; the first end of the stray capacitor is connected to the first end of the secondary side of the ideal transformer.

[0039] For example, the ideal transformer and stray capacitance described above can be considered as a single transformer.

[0040] Figure 1 middle, The current of the first inductor, For the current of the external leakage inductor, This refers to the current at the second terminal on the secondary side of the transformer. The voltage between point A at the third terminal of the third switch circuit and point B at the second terminal on the primary side of the transformer is given. Let be the voltage between point C at the first end of the secondary side of the transformer and point D at the second end of the secondary side of the transformer. The fourth switching circuit is connected to the positive terminal of the power supply as a direct power connection circuit for the output voltage.

[0041] It should be noted that the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, and tenth switching transistors are all MOSFETs.

[0042] The working principle of the quasi-unipolar four-switch Buck-Boost converter in this application is as follows: The gate of the first switching transistor is used to receive an adjustment signal sent by the controller. This adjustment signal is used to adjust the ratio of the on-time to the switching period of the first switching transistor, thereby controlling the voltage across the output capacitor of the preceding stage and changing the voltage across it. The amplitude can be adjusted to regulate the voltage gain, thereby increasing the efficiency of current waveform transformation.

[0043] Combination such as Figure 2 The waveform diagrams shown illustrate the working principle of the quasi-unipolar four-switch Buck-Boost converter of this application: The markings in the diagram are: First switching transistor Second switching transistor Third switching transistor Fourth switching transistor Fifth switch tube Sixth switch tube Seventh switch tube Eighth switch tube Ninth switch tube and the tenth switch In the upper part of the diagram, the rectangle represents the switching transistor being turned on, as indicated by the marking. The rectangle represents the corresponding time period. and On, marked as The rectangle represents the corresponding time period. and On, marked as The rectangle represents the corresponding time period. and On, marked as The rectangle represents the corresponding time period. and On, marked as The rectangle represents the corresponding time period. On, marked as The rectangle represents the corresponding time period. Conduction.

[0044] exist At any given moment, the first switch turns on with zero voltage, the third switch turns on with zero voltage, and the fifth, seventh, and tenth switches turn on with zero current. The current in the first inductor... The current rises linearly, while the current in the external leakage inductor increases. Decreases sinusoidally in the negative direction; exist At that moment, the seventh and tenth switches are turned off with zero current, and the current in the first inductor... Maintaining a linear increase in the positive direction, the current of the external leakage inductor Keep it at zero; exist At any given moment, when the first and fourth switching transistors are turned off, the current through the auxiliary inductor will charge the capacitors of the first and fourth switching transistors and discharge the capacitors of the second and third switching transistors. exist At that moment, the second and third switches were turned on with zero voltage, and the sixth switch... The seventh and ninth switches are turned on with zero current, and the current in the first inductor... Linear decrease, current of external leakage inductor It rises sinusoidally in the positive direction; exist At any given moment, the current of the external leakage inductor When the current is zero, the sixth, seventh, and ninth switches are turned off with zero current, and the current in the first inductor... Linear decrease.

[0045] Among them, such as Figure 2 The waveform of the current during the working process is shown in the figure. The horizontal axis contains... Indicates a unit of time. Indicates the on-time of the switching transistor. For the current of the external leakage inductor, This refers to the current at the second terminal on the secondary side of the transformer. The voltage between point A at the third terminal of the third switch circuit and point B at the second terminal on the primary side of the transformer is given. Let be the voltage between point C at the first end of the secondary side of the transformer and point D at the second end of the secondary side of the transformer. For output voltage, The voltage across the resonant capacitor. This is the output voltage.

[0046] The control method of the quasi-unipolar four-switch Buck-Boost converter provided in this application is illustrated below.

[0047] like Figure 3 As shown, the control method for the quasi-unipolar four-switch Buck-Boost converter provided in this application includes the following steps: Step 31: Obtain the output voltage of the quasi-unipolar four-switch Buck-Boost converter and the transformer ratio in the quasi-unipolar four-switch Buck-Boost converter.

[0048] For example, the output voltage can be obtained using devices such as a voltmeter, and the transformer ratio can be obtained by analyzing the turns ratio on the primary and secondary sides of the transformer.

[0049] Step 32: Calculate the expected voltage of the front-stage output capacitor in the quasi-unipolar four-switch Buck-Boost converter based on the output voltage and the transformation ratio.

[0050] Specifically, through the formula: ; Calculate the expected voltage of the preamp output capacitor. .

[0051] in, This represents the duty cycle of a given Buck-Boost circuit. Indicates the duty cycle of the transformer. This indicates the output voltage.

[0052] Step 33: Generate the duty cycle of the first switch in the quasi-unipolar four-switch Buck-Boost converter based on the desired voltage.

[0053] Specifically, the difference between the actual output voltage and the desired voltage of the preceding stage is calculated, and the duty cycle of the first switching transistor is generated based on the difference.

[0054] For example, the difference can be input into a digital PI regulator for adjustment to obtain the duty cycle of the first switching transistor.

[0055] Step 34: Control the unipolar four-switch Buck-Boost converter according to the duty cycle of the first switch.

[0056] Specifically, based on the duty cycle of the first switching transistor, PWM drive signals for each switching transistor in the first and second switching circuits of the quasi-unipolar four-switch Buck-Boost converter are generated, and then the switching transistors are controlled to turn on and off according to the PWM drive signals of each switching transistor.

[0057] For example, the duty cycle is input into the PWM generation unit to obtain the PWM drive signal for each switch, and the PWM drive signal is input into the gate of the switch to control the switch on and off.

[0058] In this embodiment of the invention, the conduction of the two switches on the same bridge arm of the Buck-Boost circuit is complementary. The drive signals for the primary-side full-bridge switches S1 and S3, and S2 and S4 of the LC circuit are the same. The duty cycles of the control signals for Q1 to Q2 in the secondary-side full-bridge are all half of the resonant period. Therefore, for the control of the switches in the secondary-side full-bridge, a control signal with a duty cycle of half the resonant period is used. In this embodiment of the invention, the expression for the voltage gain of the quasi-unipolar four-switch Buck-Boost converter is: ; The steady-state output waveform of the quasi-unipolar four-switch Buck-Boost converter of this application is shown in the figure below. Figure 4 As shown, Figure 4 middle The waveform of the input voltage. The waveform of the output voltage. This is the gate drive voltage of the first switching transistor. The waveform of the current at the first terminal on the primary side of the transformer is shown. The vertical axis is marked as follows: At midnight, At midnight, Gate drive voltage At midnight, Zero point.

[0059] The waveform diagram of the zero-voltage turn-on of the first switching transistor in this application is as follows: Figure 5 As shown, Figure 5 middle The waveform of the input voltage. This is the gate drive voltage of the second switch. This is the drain-source voltage of the second switching transistor. The waveform represents the current of the first inductor. ZVS represents a zero-voltage switch. The vertical axis is marked as follows: At midnight, back pressure At midnight, Gate drive voltage At midnight, Zero point.

[0060] To verify its feasibility, the embodiments of this application refer to, for example, Figure 1 The topology shown illustrates the construction of a 400W quasi-unipolar four-switch Buck-Boost converter with an input voltage of 20V~120V and an output voltage of 48V. The drive signals for the LC circuit and the four-switch Buck-Boost circuit are generated by a TI TMS320F28377S digital signal processor. Under these experimental conditions, the quasi-unipolar four-switch Buck-Boost converter can operate normally in a closed loop under its control method, achieving both electrical isolation and efficient power conversion. Furthermore, the converter prototype can operate normally under different input voltages and loads, demonstrating that the quasi-unipolar four-switch Buck-Boost converter provided in this application can overcome the shortcomings of existing technologies and is applicable under diverse operating conditions.

[0061] It is worth mentioning that by collecting the power supply voltage, the actual voltage of the front-stage output capacitor, and the actual output voltage of the LC resonant circuit, the PWM drive signal of each switch is calculated. The conduction time of each switch in the control circuit is adjusted by using the PWM drive signal of each switch to regulate the voltage gain of the quasi-unipolar four-switch Buck-Boost converter. This ensures 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 providing electrical isolation.

[0062] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0063] The above description is the preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principles described in this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A quasi-unipolar four-switch Buck-Boost converter, characterized in that, include: Buck-Boost circuit, LC resonant circuit, power supply, load resistor, 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 first switching circuit and the first terminal of the fourth switching circuit, respectively. The negative terminal of the power supply is connected to the second terminal of the first switching circuit, the second terminal of the second switching circuit, the second terminal of the third switching circuit, the second terminal of the fourth switching circuit, and the second terminal of the pre-amplifier output capacitor, respectively. The first terminal of the first inductor is connected to the third terminal of the first switching circuit, and the second terminal of the first inductor is connected to the third terminal of the second switching circuit. The first terminal of the second switching circuit is connected to the first terminal of the pre-amplifier output capacitor and the first terminal of the third switching circuit, respectively. The first terminal of the resonant capacitor is connected to the third terminal of the third switching circuit, and the resonant capacitor... The second terminal of the capacitor is connected to the first terminal of the external leakage inductor. The second terminal of the external leakage inductor is connected to the first terminal of the primary side of the transformer. The second terminal of the primary side of the transformer is connected to the third terminal of the fourth switching circuit. The first terminal of the secondary side of the transformer is connected to the third terminal of the fifth switching circuit. The first terminal of the fifth switching circuit is connected to the first terminal of the sixth switching circuit, the first terminal of the output capacitor, and the first terminal of the load resistor. The second terminal of the fifth switching circuit is connected to the second terminal of the sixth switching circuit, the second terminal of the output capacitor, and the second terminal of the load resistor. The second terminal of the secondary side of the transformer is connected to the third terminal of the sixth switching circuit.

2. The quasi-unipolar 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 switch is the first terminal of the first switch circuit, the source of the second switch is the second terminal of the first switch circuit, and the source of the first switch and the drain of the second switch are the third terminals of the first switch. The second switching circuit includes a third switch and a fourth switch; The drain of the third switch is the first terminal of the second switch circuit, the source of the fourth switch is the second terminal of the second switch circuit, and the source of the third switch and the drain of the fourth switch are the third terminals of the second switch circuit.

3. The quasi-unipolar four-switch Buck-Boost converter according to claim 2, characterized in that, The third switching circuit includes a fifth switching transistor and a sixth switching transistor; The drain of the fifth switch is the first terminal of the third switch circuit, the source of the sixth switch is the second terminal of the third switch circuit, and the source of the fifth switch and the drain of the sixth switch are the third terminal of the third switch circuit. The fourth switching circuit includes a seventh switching transistor and an eighth switching transistor; The drain of the seventh switch is the first terminal of the fourth switch circuit, the source of the eighth switch is the second terminal of the fourth switch circuit, and the source of the seventh switch and the drain of the eighth switch are the third terminals of the fourth switch circuit.

4. The quasi-unipolar four-switch Buck-Boost converter according to claim 3, characterized in that, The fifth switching circuit includes a first diode and a ninth switching transistor; The drain of the first diode is the first terminal of the fifth switching circuit, the source of the ninth switching transistor is the second terminal of the fifth switching circuit, and the source of the first diode and the drain of the ninth switching transistor are the third terminals of the fifth switching circuit. The sixth switching circuit includes a second diode and a tenth switching transistor; The drain of the second diode is the first terminal of the sixth switching circuit, the source of the tenth switching transistor is the second terminal of the sixth switching circuit, and the source of the second diode and the drain of the tenth switching transistor are the third terminal of the sixth switching circuit.

5. The quasi-unipolar four-switch Buck-Boost converter according to claim 4, characterized in that, The transformer includes an ideal transformer and stray capacitance; The first end of the primary side of the ideal transformer is the first end of the primary side of the transformer, the second end of the primary side of the ideal transformer is the second end of the primary side of the transformer, the second end of the stray capacitor is the first end of the secondary side of the transformer, and the second end of the secondary side of the ideal transformer is the second end of the secondary side of the transformer. The first terminal of the stray capacitor is connected to the first terminal on the secondary side of the ideal transformer.

6. A control method for a quasi-unipolar four-switch Buck-Boost converter, characterized in that, The control method, applied to the quasi-unipolar four-switch Buck-Boost converter as described in any one of claims 1 to 5, comprises: Obtain the output voltage of the quasi-unipolar four-switch Buck-Boost converter and the transformer ratio in the quasi-unipolar four-switch Buck-Boost converter; Calculate the expected voltage of the front-stage output capacitor in the quasi-unipolar four-switch Buck-Boost converter based on the output voltage and the transformation ratio; The duty cycle of the first switch in the quasi-unipolar four-switch Buck-Boost converter is generated based on the desired voltage. The quasi-unipolar four-switch Buck-Boost converter is controlled according to the duty cycle of the first switch.

7. The control method according to claim 6, characterized in that, The calculation of the expected voltage of the front-stage output capacitor in the quasi-unipolar four-switch Buck-Boost converter based on the output voltage and the transformation ratio includes: Through the formula: Calculate the expected voltage of the preamp output capacitor. ; in, This represents the duty cycle of a given Buck-Boost circuit. Indicates the duty cycle of the transformer. This indicates the output voltage.

8. The control method according to claim 7, characterized in that, The step of generating the duty cycle of the first switch in the quasi-unipolar four-switch Buck-Boost converter based on the desired voltage includes: Calculate the difference between the actual voltage and the desired voltage output from the preceding stage, and generate the duty cycle of the first switching transistor based on the difference.

9. The control method according to claim 8, characterized in that, The control of the quasi-unipolar four-switch Buck-Boost converter based on the duty cycle of the first switch includes: The PWM drive signal for each switch in the first and second switching circuits of the quasi-unipolar four-switch Buck-Boost converter is generated based on the duty cycle of the first switch. The switching transistors are controlled to turn on and off based on the PWM drive signal of each transistor.

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