Power converter and its control method

Abstract

A power converter and its control method include primary sides of two transformers being connected in series to form a primary series assembly. An input switch assembly operating in a full-bridge mode or a half-bridge mode. In a first configuration, the primary series assembly and a capacitor are connected in series between two nodes of the input switch assembly, and a control module is electrically connected to the input switch assembly. Alternatively, in the second configuration, a node of the input switch assembly is electrically connected to a node formed in a series connection of two input capacitors through a back-to-back switch assembly, and the control module is electrically connected to the input switch assembly and the back-to-back switch assembly. In the half-bridge or full-bridge mode, the control module controls the input switch assembly in the first configuration or the input switch assembly in the second configuration and the back-to-back switch assembly to form a half-bridge or full-bridge architecture. In the full-bridge mode, there is a phase shift value between control signals of two switches. In this way, the situation of large voltage stress on the secondary side of the transformer is improved.

Description

Technical Field

[0001] This invention relates to a power conversion technology, and more particularly to a dual-transformer type power converter with a wide voltage range and its control method. Prior Technology

[0002] To meet wide voltage range input or output requirements, the secondary-side switches (such as MOSFETs) of a full-bridge converter must withstand greater voltage stress; two-transformer full-bridge converters also encounter voltage stress issues with their secondary-side switches. While some power conversion technologies have been developed, improvements are still needed. Summary of the Invention

[0003] One objective of this invention is to provide a power converter and its control method to improve the situation where the transformer secondary switch of a dual-transformer full-bridge converter is subjected to large voltage stress when used in applications with a wide range of input / output voltages.

[0004] To achieve the above objectives, one aspect of the present invention provides a power converter, comprising: two transformers, the primary sides of the two transformers being connected in series to form a primary series group; an input switch group, including a first bridge arm and a second bridge arm connected in parallel, the first bridge arm including a first switch and a second switch connected in series, the first switch and the second switch being connected to form a first node, the second bridge arm including a third switch and a fourth switch connected in series, the third switch and the fourth switch being connected to form a second node, the input switch group operating in a full-bridge mode or a half-bridge mode; wherein, the primary series group and an input capacitor are connected in series between the first node and the second node; and a control module electrically connected to the input switch group; the control module is configured to control the third switch and the fourth switch. The switches are turned on and off complementaryly. In response to the input switch group switching from full-bridge mode to half-bridge mode, the duty cycle of the control signal of the first switch, which is asynchronous with the control signal of the fourth switch, gradually decreases to 0, and the duty cycle of the control signal of the second switch, which is asynchronous with the control signal of the third switch, gradually increases to 1. In response to the input switch group switching from half-bridge mode to full-bridge mode, the duty cycle of the control signal of the first switch gradually increases from 0 to make the control signal of the first switch asynchronous with the control signal of the fourth switch, and the duty cycle of the control signal of the second switch gradually decreases from 1 to make the control signal of the second switch asynchronous with the control signal of the third switch. The first and second switches are turned on and off complementaryly.

[0005] To achieve the above objectives, another aspect of the present invention provides a power converter, comprising: two transformers, the primary sides of the two transformers being connected in series to form a primary series group; an input switch group, including a first bridge arm and a second bridge arm connected in parallel, the first bridge arm including a first switch and a second switch connected in series, the first switch and the second switch being connected to form a first node, the second bridge arm including a third switch and a fourth switch connected in series, the third switch and the fourth switch being connected to form a second node, the input switch group operating in a full-bridge mode or a half-bridge mode, the primary series group being connected between the first node and the second node; wherein the first node is electrically connected to a third node formed by two input capacitors connected in series via a back-to-back switch group; and a control module electrically connected to the input switch group and the back-to-back switch group; the control module is configured to control the third... The first and fourth switches are complementary in turning on and off; in response to the input switch group switching from full-bridge mode to half-bridge mode, the duty cycle of the control signal of the first switch, which is asynchronous with the control signal of the fourth switch, gradually decreases to 0, and the duty cycle of the control signal of the second switch, which is asynchronous with the control signal of the third switch, gradually decreases to 0, thus turning on the back-to-back switch group; in response to the input switch group switching from half-bridge mode to full-bridge mode, the duty cycle of the control signal of the first switch gradually increases from 0 to make the control signal of the first switch asynchronous with the control signal of the fourth switch, and the duty cycle of the control signal of the second switch gradually increases from 0 to make the control signal of the second switch asynchronous with the control signal of the third switch, thus turning on and off the first and second switches complementaryly, thus turning off the back-to-back switch group.

[0006] To achieve the above objectives, another aspect of the present invention provides a control method for a power converter, applied to a power converter including two transformers, an input switch group, and a control module; the primary sides of the two transformers are connected in series to form a primary series group; the input switch group includes a first bridge arm and a second bridge arm connected in parallel, the first bridge arm including a first switch and a second switch connected in series, the first switch and the second switch being connected to form a first node, the second bridge arm including a third switch and a fourth switch connected in series, the third switch and the fourth switch being connected to form a second node, the input switch group operating in a full-bridge mode or a half-bridge mode; wherein, in In a first configuration, a primary series group and an input capacitor are connected in series between a first node and a second node, and the control module is electrically connected to an input switch group; or, in a second configuration, the first node is electrically connected via a back-to-back switch group to a third node formed by two input capacitors connected in series, and the control module is electrically connected to the input switch group and the back-to-back switch group; the method includes: configuring the control module to: control the third switch and the fourth switch to complementaryly turn on and off; for the first configuration: in response to the input switch group switching from full-bridge mode to half-bridge mode, the duty cycle of the control signal of the first switch, whose control signals are asynchronous with those of the fourth switch, gradually decreases to 0, and the control signals of the third switch and the fourth switch are asynchronously turned on and off. The control signal of the second switch, whose control signal is asynchronous with the control signal of the fourth switch, gradually increases its operating cycle to 1. In response to the input switch group switching from half-bridge mode to full-bridge mode, the operating cycle of the control signal of the first switch gradually increases from 0 to make the control signal of the first switch asynchronous with the control signal of the fourth switch. The operating cycle of the control signal of the second switch gradually decreases from 1 to make the control signal of the second switch asynchronous with the control signal of the third switch. The first and second switches are controlled to complementaryly turn on and off. For the second configuration: In response to the input switch group switching from full-bridge mode to half-bridge mode, the first switch whose control signal is asynchronous with the control signal of the fourth switch... The duty cycle of the control signal of the switch gradually decreases to 0. The duty cycle of the control signal of the second switch, which is asynchronous with the control signal of the third switch, gradually decreases to 0, and the back-to-back switch group is turned on. In response to the input switch group switching from half-bridge mode to full-bridge mode, the duty cycle of the control signal of the first switch gradually increases from 0 to make the control signal of the first switch asynchronous with the control signal of the fourth switch. The duty cycle of the control signal of the second switch gradually increases from 0 to make the control signal of the second switch asynchronous with the control signal of the third switch. The first and second switches are turned on and off complementaryly, and the back-to-back switch group is turned off.

[0007] The power converter and its control method of the present invention include a primary series connection of the primary sides of two transformers to form a primary series group, and an input switch group operating in full-bridge mode or half-bridge mode. In a first configuration, the primary series group and a capacitor are connected in series between two nodes of the input switch group, and a control module is electrically connected to the input switch group; or, in a second configuration, the nodes of the input switch group are electrically connected to the nodes formed by the series connection of two input capacitors via a back-to-back switch group, and the control module is electrically connected to the input switch group and the back-to-back switch group. In half-bridge or full-bridge mode, the control module controls the input switch group of the first configuration or the input switch group of the second configuration and the back-to-back switch group to form a half-bridge or full-bridge architecture. In full-bridge mode, the control signals of the two switches have a phase shift, thereby solving the application problem of the dual transformer power converter in a wide range of input / output voltages, especially when the input voltage is high, the voltage stress borne by the electronic switches on the secondary side of the transformer can be significantly reduced. Simple Explanation of the Diagram

[0008] Figure 1 is a circuit diagram of the dual-transformer full-bridge converter associated with the present invention. Figure 2 is a circuit diagram of the first embodiment of the power converter of the present invention. Figure 3 is a signal diagram of the circuit in Figure 2 operating in full-bridge mode. Figure 4 is a schematic diagram of the equivalent circuit of the circuit in Figure 2 operating in half-bridge mode. Figure 5 is a signal diagram of the circuit in Figure 2 operating in half-bridge mode. Figure 6 is a schematic diagram of the output signal waveform of the circuit in Figure 2. Figure 7 is a circuit diagram of a second embodiment of the power converter. Figure 8 is a signal diagram of the circuit in Figure 7 operating in full-bridge mode. Figure 9 is a schematic diagram of the equivalent circuit of the circuit in Figure 7 operating in half-bridge mode. Figure 10 is a signal diagram of the circuit in Figure 7 operating in half-bridge mode. Figure 11 is a schematic diagram of the output signal waveform of the circuit in Figure 7. Figure 12 is a schematic diagram of the control architecture of the power converter embodiment of the present invention operating in full-bridge mode. Figure 13 is a schematic diagram of the control architecture of the power converter embodiment of the present invention operating in half-bridge mode. Figure 14 is a schematic diagram of the control flow of the first embodiment of the power converter of the present invention. Figure 15 is a schematic diagram of the signal from full-bridge mode to half-bridge mode in the first embodiment of the power converter of the present invention. Figure 16 is a schematic diagram of the signal from half-bridge mode to full-bridge mode in the first embodiment of the power converter of the present invention. Figure 17 is a schematic diagram of the control flow of the second embodiment of the power converter of the present invention. Figure 18 is a schematic diagram of the signal from full-bridge mode to half-bridge mode in the second embodiment of the power converter of the present invention. Figure 19 is a schematic diagram of the signal from half-bridge mode to full-bridge mode in the second embodiment of the power converter of the present invention. Implementation

[0009] To make the above and other objects, features and advantages of the present invention more apparent and understandable, preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0010] With the rapid development of industries such as information technology and electric vehicles, charging modules have become indispensable key components. For example, as the range requirements of electric vehicles increase, the output power of charging modules also increases accordingly. In electric vehicles, battery voltage fluctuates with changes in the state of charging; therefore, auxiliary power modules (APMs) must be designed to cope with these variations. To this end, APMs typically need a wide input voltage range to accommodate different battery voltages. For instance, an APM may need to operate within the voltage range of high-voltage batteries (e.g., 200V to 500V or higher) and provide a stable voltage output within the voltage range of low-voltage batteries (e.g., 6V to 16V or higher). This wide-range input / output voltage design ensures that the APM can stably provide the necessary power to auxiliary equipment under various operating conditions, whether the battery is fully charged or nearly depleted.

[0011] Among related technologies, full-bridge converters offer significant advantages in APMs (Automatic Power Supply Systems), especially when dealing with wide-range input or output voltage applications. This is because full-bridge converters possess high efficiency and excellent voltage regulation capabilities, effectively handling varying input voltages from high-voltage battery packs while providing a stable output voltage. This is crucial for ensuring proper operation under different conditions. Furthermore, the full-bridge topology allows for a more even distribution of voltage and current stress, reducing component losses and improving system reliability and lifespan. Additionally, this design facilitates high power density, enabling full-bridge converters to provide efficient power conversion in space-constrained APMs, making them an ideal choice for electric vehicle auxiliary power systems.

[0012] It is worth noting that, in order to meet a wide range of input or output voltage requirements, the transformer coil turns of the full-bridge converter in an APM are lower than those of a full-bridge converter with a fixed output voltage. A lower coil turns count means that when the input voltage is higher, the electronic switches (such as MOSFETs) on the secondary side of the transformer must withstand greater voltage stress. Therefore, the voltage rating of the electronic switches needs to be selected higher than the specifications required for a full-bridge converter with a fixed output voltage.

[0013] For example, as shown in Figure 1, a two-transformer full bridge converter 10 includes a transformer module 11 and its coupled input switch group 12 and output switch group 13. The input switch group 12 is used to receive the input voltage Vin, and the output switch group 13 is coupled to the output capacitor Cout to provide the output voltage Vout. This architecture can achieve the advantage of soft-switch on the primary side under a wide range of load conditions and eliminates the need for components such as output inductors. However, this architecture still faces the voltage stress problem of the secondary side electronic switches when dealing with a wide range of input / output voltages.

[0014] To address the challenges of using dual-transformer full-bridge converters across a wide range of input / output voltages, particularly when the input voltage is high and the electronic switches on the secondary side of the transformer must withstand significant voltage stress, this paper proposes a power converter implementation scheme, illustrated with examples below, but not limited to these examples.

[0015] In a first embodiment, Figure 2 illustrates a bridge-type converter with blocking capacitors. A power converter 20 includes a transformer module 21, an input switch group 22, and a control module 2C. The transformer module 21 includes two transformers T1 and T2. The primary sides of the two transformers T1 and T2 are connected in series to form a primary series group, and the secondary sides of the two transformers T1 and T2 are connected in series to form a secondary series group, for example, their terminals are coupled to each other. The input switch group 22 can receive an input voltage Vin (e.g., 200~500Vdc). The input switch group 22 includes a first bridge arm and a second bridge arm connected in parallel. The first bridge arm includes a first switch Q1 and a second switch Q2 connected in series. The first switch Q1 and the second switch Q2 are connected to form a first node. The second bridge arm includes a third switch Q3 and a fourth switch Q4 connected in series. The third switch Q3 and the fourth switch Q4 are connected to form a second node. The first switch Q1, the second switch Q2, the third switch Q3 and the fourth switch Q4 are electronic switches. Here, only MOSFETs are used as an example, but this is not a limitation. The primary series group formed by the primary sides of the two transformers T1 and T2 connected in series and an input capacitor Cp are connected in series between the first node and the second node. In this example, the input capacitor Cp is placed between the first node and the transformer T1 to block unsuitable signal components from the input switch group 22 to the transformer module 21. The control module 2C can be a microprocessor (MCU), digital signal processor (DSP), or application-specific integrated circuit (ASIC), etc. The control module 2C is electrically connected to the first switch Q1, the second switch Q2, the third switch Q3, and the fourth switch Q4 of the input switch group 22, and outputs control signals SC1, SC2, SC3, and SC4 to control the first switch Q1, the second switch Q2, the third switch Q3, and the fourth switch Q4, so that the input switch group 22 operates in a full-bridge mode or a half-bridge mode.

[0016] For example, as shown in Figure 2, the control module 2C is configured to switch the input switch group 22 from full-bridge mode to half-bridge mode in response to the determination that the value of an input voltage Vin associated with the input switch group 22 is greater than a voltage threshold (e.g., Vin>350Vdc); and to switch the input switch group 22 from half-bridge mode to full-bridge mode in response to the determination that the value of the input voltage Vin is less than or equal to the voltage threshold (e.g., Vin<=350Vdc).

[0017] As shown in Figures 2 and 3, control signal SC1 is, for example, the voltage difference between the gate (G) and source (S) of the first switch Q1, signal VGS_Q1; control signal SC2 is, for example, the voltage difference between the gate and source of the second switch Q2, signal VGS_Q2; control signal SC3 is, for example, the voltage difference between the gate and source of the third switch Q3, signal VGS_Q3; control signal SC4 is, for example, the voltage difference between the gate and source of the fourth switch Q4, signal VGS_Q4; the stress voltage of the fifth switch QR1 on the secondary side of the transformer is, for example, the voltage difference between the drain (D) and source (S) of the fifth switch QR1, signal VDS_SR1; the stress voltage of the sixth switch QR2 on the secondary side of the transformer is, for example, the voltage difference between the drain and source of the sixth switch QR2, signal VDS_SR2; and the output voltage Vout corresponds to the output current Iout.

[0018] As shown in Figures 2 and 3, when the input voltage Vin is low (e.g., Vin < 350Vdc), the input switch group 22 operates in full-bridge phase-shift mode. For example, the control module 2C is configured to gradually increase the duty cycle of the control signal SC1 of the first switch Q1 from 0 (i.e., 0%) to desynchronize the control signal SC1 of the first switch Q1 with the control signal SC4 of the fourth switch Q4, and gradually decrease the duty cycle of the control signal SC2 of the second switch Q2 from 1 (i.e., 100%) to desynchronize the control signal SC2 of the second switch Q2 with the control signal SC3 of the third switch Q3. The first switch Q1 and the second switch Q2 are controlled to complementaryly turn on and off. For example, the control signal SC1 of the first switch Q1 (VGS_Q1 as shown in Figure 3) and the control signal SC2 of the second switch Q2 (VGS_Q1 as shown in Figure 3) are controlled to complement each other. The duty cycle of GS_Q2 is 50% (i.e., 0.5) or based on its increment / decrement value, controlling the complementary on and off of the third switch Q3 and the fourth switch Q4. For example, the duty cycle of the control signal SC3 of the third switch Q3 (V GS_Q3 as shown in Figure 3) and the control signal SC4 of the fourth switch Q4 (V GS_Q4 as shown in Figure 3) can be 50% (i.e., 0.5) or based on its increment / decrement value. There is a phase shift P between the control signal SC1 of the first switch Q1 (V GS_Q1 as shown in Figure 3) and the control signal SC4 of the fourth switch Q4 (V GS_Q4 as shown in Figure 3). For example, the phase shift P is within a phase shift range, which is greater than 0 and not greater than 180 degrees, such as 45 degrees, 90 degrees, 135 degrees, etc.

[0019] As shown in Figures 4 and 5, when the input voltage Vin of the power converter 40 is high (e.g., Vin > 350Vdc), the input switch group 22 operates in half-bridge mode. For example, the control module 2C is configured to control the third switch Q3 and the fourth switch Q4 to complementaryly turn on and off in response to the input switch group 22 switching from full-bridge mode to half-bridge mode. The control signal SC4 of the first switch Q1 (VGS_Q1 shown in Figures 3 and 5), which is asynchronous with the control signal SC4 of the fourth switch Q4 (VGS_Q4 shown in Figures 3 and 5), gradually decreases its duty cycle (e.g., 50%, i.e., 0.5) to 0 (e.g., 0%, i.e., the low level of the PWM signal), so that the first switch Q1 gradually becomes equivalent to being always off. The control signal SC2 of the second switch Q2 (VGS_Q3 shown in Figures 3 and 5), which is asynchronous with the control signal SC3 of the third switch Q3 (VGS_Q3 shown in Figures 3 and 5), gradually decreases its duty cycle (e.g., 50%, i.e., 0.5) to 0, i.e., 0%, i.e., the low level of the PWM signal), gradually reducing the duty cycle (e.g., 50%, i.e., 0.5), which is asynchronous with the control signal SC3 of the third switch Q3 (VGS_Q3 shown in Figures 3 and 5), gradually reduces its duty cycle (e.g., 0.5), i.e., the low level of the PWM signal), i.e., 0%. The duty cycle of GS_Q2 (e.g., 50%, or 0.5) gradually increases to 1 (e.g., 100%, or the high level of the PWM signal), making the second switch Q2 gradually equivalent to being always on.

[0020] Furthermore, as shown in Figure 2, the power converter 20 also includes an output switch group 23. The output switch group 23 is connected in parallel to the secondary series connection of the transformer module 21. The control module 2C is electrically connected to the output switch group 23. For example, the secondary sides of two transformers T1 and T2 are connected to form a first contact. The output switch group 23 includes a fifth switch QR1 and a sixth switch QR2 connected in series. The fifth switch QR1 and the sixth switch QR2 are connected to form a second contact. An output capacitor Cout is electrically connected between the first contact and the second contact. The control module 2C is electrically connected to the second contact. The fifth switch QR1 and the sixth switch QR2 of the output switch group 23 are connected. The control module 2C outputs control signals SR1 and SR2 to control the fifth switch QR1 and the sixth switch QR2, so that the output capacitor Cout generates the output voltage Vout. As shown in Figure 6, in the first embodiment of the power converter, when switching from full-bridge mode (or full-bridge stage, as shown in F in Figure 6) to half-bridge mode (or half-bridge stage, as shown in H in Figure 6), the input voltage is 480Vdc, the output voltage is 12Vdc, and the output power is 3kW.

[0021] As shown in Figures 3 and 5, the voltage stress of the fifth switch connected to the secondary side of the transformer (e.g., VDS_SR1) decreases from 79.017Vdc (Figure 3) to 39.8721Vdc (Figure 5), and the voltage stress of the sixth switch connected to the secondary side of the transformer (e.g., VDS_SR2) decreases from 79.0379Vdc (Figure 3) to 39.8924Vdc (Figure 5). The ripple of the output current Iout corresponding to the output voltage Vout decreases from 62.483Adc (Figure 3) to 32.6985Adc (Figure 5), and the peak-to-peak output current (Iout_pp) decreases from 62.5Adc to 32.2Adc. Therefore, the voltage stress of the electronic switches on the secondary side of the transformer in the first embodiment of the power converter can be significantly reduced.

[0022] In the second embodiment, Figure 7 illustrates a bridge-type converter with back-to-back switch groups. A power converter 70 includes a transformer module 71, an input switch group 72, and a control module 7C. The transformer module 71, input switch group 72, and control module 7C are substantially the same as those of transformer module 21, input switch group 22, and control module 2C. For example, transformer module 71 includes two transformers T1 and T2, with the primary sides of the two transformers T1 and T2 connected in series to form a primary series group, and the secondary sides of the two transformers T1 and T2 connected in series to form a secondary series group. Input switch group 72 can receive an input voltage Vin (e.g., 200~500Vdc). Input switch group 72 includes a first bridge arm and a second bridge arm connected in parallel. The first bridge arm includes a first switch Q1 and a second switch Q2 connected in series, forming a first node. The second bridge arm includes a third switch Q3 and a fourth switch Q4 connected in series, forming a third node. The first node is connected to a second node via a back-to-back switch group QB, which is electrically connected to a third node formed by two input capacitors Cin1 and Cin2 connected in series. In this example, the two input capacitors Cin1 and Cin2 are connected in series to form an input capacitor group 73 to receive the input voltage Vin. The input capacitor group 73 is connected in parallel to the input switch group 72. The control module 7C is electrically connected to the first switch Q1, the second switch Q2, the third switch Q3, the fourth switch Q4 and the back-to-back switch group QB of the input switch group 72, and outputs control signals SC1, SC2, SC3, SC4 and SCB to control the first switch Q1, the second switch Q2, the third switch Q3, the fourth switch Q4 and the back-to-back switch group QB, so that the input switch group 72 operates in a full-bridge mode or a half-bridge mode.

[0023] For example, as shown in Figure 7, the control module 7C is configured to switch the input switch group 72 from full-bridge mode to half-bridge mode in response to the determination that the value of the input voltage Vin associated with the input switch group 72 is greater than a voltage threshold (e.g., Vin>350Vdc); the control module 7C is configured to switch the input switch group 72 from half-bridge mode to full-bridge mode in response to the determination that the value of the input voltage Vin is less than or equal to a voltage threshold (e.g., Vin<=350Vdc).

[0024] As shown in Figures 7 and 8, when the input voltage Vin is low (e.g., Vin <= 350Vdc), the input switch group 72 operates in full-bridge phase-shift mode. For example, the control module 7C is configured to, in response to the input switch group 72 switching from half-bridge mode to full-bridge mode, gradually increase the duty cycle of the control signal SC1 of the first switch Q1 from 0 to make the control signal SC1 of the first switch Q1 and the control signal SC4 of the fourth switch Q4 asynchronous. Similarly, gradually increase the duty cycle of the control signal SC2 of the second switch Q2 from 0 to make the control signal SC2 of the second switch Q2 and the control signal SC3 of the third switch Q3 asynchronous. This allows the first switch Q1 and the second switch Q2 to be turned on and off complementaryly. For example, the control signal SC1 of the first switch Q1 (VGS_Q1 as shown in Figure 8) and the control signal SC2 of the second switch Q2 (VGS_Q1 as shown in Figure 8) are used to control the first switch Q1 and the second switch Q2 to be turned off complementaryly. The duty cycle of GS_Q2 is 50% (i.e., 0.5) or based on its increment / decrement value, controlling the complementary conduction and cutoff of the third switch Q3 and the fourth switch Q4. For example, the duty cycle of the control signal SC3 of the third switch Q3 (V GS_Q3 as shown in Figure 8) and the control signal SC4 of the fourth switch Q4 (V GS_Q4 as shown in Figure 8) can be 50% (i.e., 0.5) or based on its increment / decrement value, controlling the cutoff of the back-to-back switch group QB. For example, the duty cycle of the control signal SCB of the back-to-back switch group QB is 0, making the back-to-back switch group QB equivalent to being always off. There is a phase shift P between the control signal SC1 of the first switch Q1 (V GS_Q1 as shown in Figure 8) and the control signal SC4 of the fourth switch Q4 (V GS_Q4 as shown in Figure 8). For example, the phase shift P is within a phase shift range, which is greater than 0 and not greater than 180 degrees, such as 45 degrees, 90 degrees, 135 degrees, etc.

[0025] As shown in Figures 9 and 10, the control signal SCB is, for example, the voltage difference between the gate and source of the back-to-back switch group QB, signal VGS_QBB. When the input voltage Vin of the power converter 90 is high (e.g., Vin > 350Vdc), the input switch group 72 operates in half-bridge mode. For example, the control module 7C is configured to control the third switch Q3 and the fourth switch Q4 to complementary turn on and off in response to the switching of the input switch group 72 from full-bridge mode to half-bridge mode. The duty cycle of the control signal SC1 of the first switch Q1, which is asynchronous with the control signal SC4 of the fourth switch Q4, gradually decreases from 0 (e.g., 0.5%) to 0 (e.g., 0%). The low level of the M signal gradually makes the first switch Q1 equivalent to being always off. The duty cycle of the control signal SC2 of the second switch Q2, which is asynchronous with the control signal SC3 of the third switch Q3, gradually decreases to 0, making the second switch Q2 equivalent to being always on. This controls the back-to-back switch group QB to be on. For example, the duty cycle of the control signal SCB of the back-to-back switch group QB is 100% (i.e., 1, which is the high level of the PWM signal), making the back-to-back switch group QB equivalent to being always on.

[0026] Furthermore, as shown in Figure 7, the power converter 70 also includes an output switch group 74 and an output capacitor Cout. The output switch group 74 is connected in parallel to the secondary winding of the transformer module 71. The control module 7C is electrically connected to the output switch group 74. For example, the secondary windings of two transformers T1 and T2 are connected to form a first contact. The output switch group 74 includes a fifth switch QR1 and a sixth switch QR2 connected in series. The fifth switch QR1 and the sixth switch QR2 are connected to form a second contact. The output capacitor Cout is electrically connected between the first contact and the second contact. The control module 7C is electrically connected to the fifth switch QR1 and the sixth switch QR2 of the output switch group 74. It outputs control signals SR1 and SR2 to control the fifth switch QR1 and the sixth switch QR2, so that the output capacitor Cout generates the output voltage Vout, as shown in Figure 11. In the second embodiment of the power converter, when switching from full-bridge mode (or full-bridge stage, as shown in F in Figure 11) to half-bridge mode (or half-bridge stage, as shown in H in Figure 11), the input voltage is 480Vdc, the output voltage is 12Vdc, and the output power is 3kW.

[0027] As shown in Figures 8 and 10, the voltage stress of the fifth switch connected to the secondary side of the transformer (e.g., VDS_SR1) decreases from 79.0172Vdc (Figure 8) to 39.072Vdc (Figure 10), and the voltage stress of the sixth switch connected to the secondary side of the transformer (e.g., VDS_SR2) decreases from 79.0379Vdc (Figure 8) to 39.082Vdc (Figure 10). The ripple of the output current Iout corresponding to the output voltage Vout decreases from 62.488Adc (Figure 8) to 32.188Adc (Figure 10), and the output ripple current (Iout_pp) decreases from 62.5Adc to 32.2Adc. Therefore, the voltage stress of the electronic switches on the secondary side of the transformer in the first embodiment of the power converter can be significantly reduced.

[0028] The following examples illustrate the control architecture of the first and second embodiments of the power converter.

[0029] On one hand, in response to the input switch group being in full-bridge mode, as shown in Figure 12, the control architecture example 120 includes a subtractor 121, a voltage controller 122, a PWM generator 123, a phase shift generator 124, a complementary signal generator 125, a drive circuit 126, and a DC / DC converter 127. The DC / DC converter 127 can be, for example, the power converter 20 in Figure 2 or the power converter 70 in Figure 7. Taking the power converter 20 as an example, the DC / DC converter 127 can receive the input voltage Vin and generate the output voltage Vout by the output capacitor Cout. The output voltage Vout can be captured as a feedback voltage value Vout_fb. Subtractor 121 can subtract the feedback voltage value Vout_fb from a voltage reference value Vout_ref to calculate a voltage error value E. The voltage error value E can generate a control quantity through voltage controller 122 (such as a PI controller). The control quantity can generate a pulse width modulation (PWM) signal with a specific duty cycle through PWM generator 123. The PWM signal can generate a phase shift quantity through phase shift generator 124. The PWM signal and the phase shift quantity are based on a reference value of 0.5 (i.e., 50%) and are used by complementary signal generator 125 to generate control signals SC1, SC2, SC3 and SC4, respectively, as input signals to drive circuit 126 to generate drive signals to DC-DC converter 127, so that DC-DC converter 127 operates in full-bridge mode.

[0030] On the other hand, in response to the half-bridge mode of the input switch group, as shown in Figure 13, the control architecture example 130 includes a subtractor 131, a voltage controller 132, a PWM generator 133, a drive circuit 134, and a DC / DC converter 135. The DC / DC converter 135 can be, for example, the power converter 20 in Figure 2 or the power converter 70 in Figure 7. Taking the power converter 20 as an example, the DC / DC converter 135 can receive the input voltage Vin and generate the output voltage Vout by the output capacitor Cout. The output voltage Vout can be captured as a feedback voltage value Vout_fb. The subtractor 131 can subtract the feedback voltage value Vout_fb from a voltage reference value Vout_ref to calculate a voltage error value E. The voltage error value E can be used by the voltage controller 132 (such as a PI controller) to generate a control quantity. The control quantity can be used by the PWM generator 133 to generate pulse width modulation (PWM) signals with a specific working cycle as control signals SC3 and SC4, which are used as input signals to the drive circuit 134 to generate drive signals to the DC-DC converter 135, so that the DC-DC converter 135 operates in half-bridge mode.

[0031] The following example illustrates the control flow of the first embodiment of the power converter, as shown in Figures 2 and 12 to 14. Flow example 140 includes: Step 141, the control module 2C reads the output voltage Vout as the feedback voltage value Vout_fb, subtracts the feedback voltage value Vout_fb from the voltage reference value Vout_ref, and calculates the voltage error value E; Step 142, the voltage controller generates a control quantity based on the voltage error value E, followed by step 143; Step 143, it is determined whether the input voltage Vin is greater than the preset maximum input value Vin_max. (e.g., voltage threshold) If the judgment is yes, the power converter switches from full-bridge mode to half-bridge mode, proceeding to step 144; if the judgment is no, the power converter switches from half-bridge mode to full-bridge mode, proceeding to step 145; Step 144: Determine whether the switching time (e.g., TS1) is less than or equal to the maximum switching time (e.g., Tmax). If the judgment is yes, proceed to step 146; if the judgment is no, the switching time (e.g., TS1) has reached its maximum value, the switching time (e.g., TS1) remains unchanged, and the control flow ends; Step 146: The switching time (e.g., TS1) gradually increases, the duty cycle of the first switch Q1 (e.g., Q1_duty) gradually decreases to 0% (as shown in Figure 15, control signal SC1 moves from full-bridge stage F through switching stage T to half-bridge stage H, and the duty cycle gradually decreases to 0%), and the duty cycle of the second switch Q2 (e.g., Q2_duty) gradually increases to 100% (as shown in Figure 15, control signal SC2 moves from full-bridge stage F through switching stage T to half-bridge stage H, and the duty cycle gradually increases to 100%); then, proceed to step... Step 147: Determine if the duty cycle (Q1_duty) of the first switch Q1 is less than 0%. If yes, proceed to step 148; if no, proceed to step 149. Step 148: Set the duty cycle (Q1_duty) of the first switch Q1 to 0%. Step 149: Determine if the duty cycle (Q1_duty) of the first switch Q1 is greater than 100%. If yes, proceed to step 14a; if no, proceed to step 14b. Step 14a: Set the second switch... The duty cycle (Q2_duty) of Q2 is equal to 100%; Step 14b: Control the duty cycle so that the third switch Q3 and the fourth switch Q4 are turned on and off complementaryly (as shown in Figure 15, the control signals SC3 and SC4 move from the full-bridge stage F through the switching stage T to the half-bridge stage H, and their duty cycles are complementary); Step 145: Determine whether the switching time (e.g., TS1) is greater than or equal to 0 (milliseconds, ms or msec). If the determination is yes, proceed to step 14c; if the determination is no, proceed to step 14d.Step 14c: The switching time (e.g., TS1) gradually decreases, and the duty cycle (Q1_duty) of the first switch Q1 gradually increases to 50% (as shown in Figure 16, control signal SC1 moves from half-bridge stage H through switching stage T to full-bridge stage F, and the duty cycle gradually increases to 50%). The duty cycle (Q2_duty) of the second switch Q2 gradually decreases to 50% (as shown in Figure 16, control signal SC2 moves from half-bridge stage H through switching stage T to full-bridge stage F, and the duty cycle gradually decreases to 50%). Then, proceed to step 14e. Step 14d: The first switch Q1, the second switch Q2, the third switch Q3, and the fourth switch Q4 switch to phase-shift control mode. For example, there is a phase shift between the control signals of the first switch Q1 and the fourth switch Q4 (as shown in Figure 16, control signals SC1, SC2, SC3, and SC4 move from half-bridge stage H through switching stage T to full-bridge stage F, and there is a phase shift between control signals SC1 and SC4). Step 14e: Determine the duty cycle of the first switch Q1. If the duty cycle (Q1_duty) is greater than or equal to 50%, proceed to step 14f; if not, proceed to step 14g. In step 14f, set the duty cycle (Q1_duty) of the first switch Q1 to 50%. In step 14g, determine if the duty cycle (Q2_duty) of the second switch Q2 is less than or equal to 50%. If yes, proceed to step 14h; if no, proceed to step 14i. In step 14h, set the duty cycle (Q2_duty) of the second switch Q2 to 50%. In step 14i, control the duty cycle so that the first switch Q1 and the second switch Q2 are complementary in turning on and off, and the third switch Q3 and the fourth switch Q4 are complementary in turning on and off (as shown in Figure 16, control signals SC1, SC2, SC3, and SC4 move from the half-bridge stage H through the switching stage T to the full-bridge stage F. The duty cycles of control signals SC1 and SC4 are complementary, and the duty cycles of control signals SC2 and SC3 are complementary). In the graphs presented in this paper, t represents time and V represents the voltage signal. It should be understood that the control module can also appropriately control the fifth and sixth switches on the secondary side of the transformer to provide output rectification functionality. For example, the fifth and sixth switches can be switches with rectification functions or diodes (this is not limited), so that the output capacitor generates an output voltage.

[0032] As described above, this article also proposes an embodiment of the control method for a power converter, illustrated below, but not limited thereto. A control method for a power converter is applied to a power converter, which includes two transformers, an input switch group, and a control module; the primary sides of the two transformers are connected in series to form a primary series group; the input switch group includes a first bridge arm and a second bridge arm connected in parallel, the first bridge arm including a first switch and a second switch connected in series, the first switch and the second switch being connected to form a first node, the second bridge arm including a third switch and a fourth switch connected in series, the third switch and the fourth switch being connected to form a second node, the input switch group operating in a full-bridge mode or a half-bridge mode; wherein, the primary series group and an input capacitor are connected in series between the first node and the second node, and the control module is electrically connected to the input switch group; the method includes: configuring the control module to: control The third and fourth switches are complementary in their on / off states. In response to the input switch group switching from full-bridge mode to half-bridge mode, the duty cycle of the control signal of the first switch, whose control signal is asynchronous with that of the fourth switch, gradually decreases to 0, while the duty cycle of the control signal of the second switch, whose control signal is asynchronous with that of the third switch, gradually increases to 1. Similarly, in response to the input switch group switching from half-bridge mode to full-bridge mode, the duty cycle of the control signal of the first switch gradually increases from 0 to desynchronize its control signal with that of the fourth switch, while the duty cycle of the control signal of the second switch gradually decreases from 1 to desynchronize its control signal with that of the third switch. This allows the first and second switches to complementaryly turn on and off. This method embodiment is related to the content of the first embodiment of the power converter described above and will not be repeated here.

[0033] The following example illustrates the control flow of the second embodiment of the power converter, as shown in Figures 7, 12, 13, and 17. Flow example 170 includes: Step 171, the control module 7C reads the output voltage Vout as the feedback voltage value Vout_fb, subtracts the feedback voltage value Vout_fb from the voltage reference value Vout_ref, and calculates the voltage error value E; Step 172, the voltage controller generates a control quantity based on the voltage error value E, followed by step 173; Step 173, the input voltage Vin is determined. If the input value is greater than the preset maximum value Vin_max (e.g., voltage threshold), and the power converter switches from full-bridge mode to half-bridge mode, proceeding to step 174; if the input value is not greater, and the power converter switches from half-bridge mode to full-bridge mode, proceeding to step 175; in step 174, a control signal is generated to turn off the first switch Q1 and the second switch Q2, and to turn on the back-to-back switch group QB (as shown in Figure 18, control signals SC1 and SC2 change from full-bridge stage F to half-bridge stage H, and the duty cycle is set to 0). Next, proceed to step 176; in step 176, control the duty cycle so that the third switch Q3 and the fourth switch Q4 are turned on and off complementaryly (as shown in Figure 18, control signals SC3 and SC4 move from the full-bridge stage F through the switching stage T to the half-bridge stage H, with complementary duty cycles); in step 175, generate control signals to turn on the first switch Q1 and the second switch Q2, and to turn off the back-to-back switch group QB (as shown in Figure 19, control signals SC1 and SC2 move from the half-bridge stage H to the full-bridge stage F, with complementary duty cycles). The operating cycle of the control signal SCB of the back-to-back switch group QB is 0. Then, proceed to step 177. In step 177, the first switch Q1, the second switch Q2, the third switch Q3, and the fourth switch Q4 switch to phase-shift control mode. For example, there is a phase shift between the control signal of the first switch Q1 and the control signal of the fourth switch Q4 (as shown in Figure 19, control signals SC1, SC2, SC3, and SC4 move from the half-bridge stage H through the switching stage T to the full-bridge stage F, and there is a phase shift between control signals SC1 and SC4). It should be understood that the control module can also appropriately control the fifth and sixth switches on the secondary side of the transformer to provide output rectification functionality. For example, the fifth and sixth switches can be switches with rectification functions or diodes (not limited here) to enable the output capacitor to generate an output voltage.

[0034] As described above, this article also proposes a control method embodiment for a second embodiment of a power converter, illustrated below, but not limited thereto. A control method for a power converter is applied to a power converter, which includes two transformers, an input switch group, and a control module; the primary sides of the two transformers are connected in series to form a primary series group; the input switch group includes a first bridge arm and a second bridge arm connected in parallel, the first bridge arm including a first switch and a second switch connected in series, the first switch and the second switch being connected to form a first node, the second bridge arm including a third switch and a fourth switch connected in series, the third switch and the fourth switch being connected to form a second node, the input switch group operating in a full-bridge mode or a half-bridge mode; wherein, the first node is electrically connected to a third node formed by two input capacitors connected in series via a back-to-back switch group, and the control module is electrically connected to the input switch group and the back-to-back switch group; the method includes: configuring the control module to: control the third switch... The first and second switches are complementary in their on / off states. In response to the input switch group switching from full-bridge mode to half-bridge mode, the duty cycle of the control signal of the first switch, whose control signal is asynchronous with that of the fourth switch, gradually decreases to 0. The duty cycle of the control signal of the second switch, whose control signal is asynchronous with that of the third switch, gradually decreases to 0, thus controlling the back-to-back switch group to turn on. In response to the input switch group switching from half-bridge mode to full-bridge mode, the duty cycle of the control signal of the first switch gradually increases from 0 to make the control signal of the first switch asynchronous with that of the fourth switch. The duty cycle of the control signal of the second switch gradually increases from 0 to make the control signal of the second switch asynchronous with that of the third switch. The first and second switches are complementary in their on / off states, thus controlling the back-to-back switch group to turn off. This method embodiment is related to the relevant content of the second embodiment of the power converter described above, and will not be repeated here.

[0035] Combining the two methods described above, this paper also proposes a control method for a power converter, illustrated below, but not limited to this. A control method for a power converter is applied to a power converter comprising two transformers, an input switch group, and a control module; the primary sides of the two transformers are connected in series to form a primary series group; the input switch group includes a first bridge arm and a second bridge arm connected in parallel, the first bridge arm including a first switch and a second switch connected in series, the first switch and the second switch being connected to form a first node, the second bridge arm including a third switch and a fourth switch connected in series, the third switch and the fourth switch being connected to form a second node, the input switch group operating in a full-bridge mode or a half-bridge mode; wherein, in a first configuration, the primary series group... An input capacitor is connected in series between the first node and the second node, and the control module is electrically connected to the input switch group; or, in a second configuration, the first node is electrically connected via a back-to-back switch group to a third node formed by two input capacitors connected in series, and the control module is electrically connected to the input switch group and the back-to-back switch group; the method includes: configuring the control module to: control the third switch and the fourth switch to be complementaryly turned on and off; for the first configuration: in response to the input switch group switching from full-bridge mode to half-bridge mode, the duty cycle of the control signal of the first switch, whose control signal is asynchronous with the control signal of the fourth switch, gradually decreases to 0, and the duty cycle of the control signal of the third switch is asynchronous with the control signal of the fourth switch. The operating cycle of the control signal of the synchronized second switch gradually increases to 1; in response to the input switch group switching from half-bridge mode to full-bridge mode, the operating cycle of the control signal of the first switch gradually increases from 0 to desynchronize the control signal of the first switch with the control signal of the fourth switch, and the operating cycle of the control signal of the second switch gradually decreases from 1 to desynchronize the control signal of the second switch with the control signal of the third switch, thus controlling the first and second switches to be turned on and off complementaryly; for the second configuration: in response to the input switch group switching from full-bridge mode to half-bridge mode, the control signal of the first switch, which is desynchronized with the control signal of the fourth switch, is controlled... The operating cycle of the control signal gradually decreases to 0, and the operating cycle of the control signal of the second switch, which is asynchronous with the control signal of the third switch, gradually decreases to 0, controlling the back-to-back switch group to conduct. In response to the input switch group switching from half-bridge mode to full-bridge mode, the operating cycle of the control signal of the first switch gradually increases from 0 to make the control signal of the first switch asynchronous with the control signal of the fourth switch, and the operating cycle of the control signal of the second switch gradually increases from 0 to make the control signal of the second switch asynchronous with the control signal of the third switch, controlling the first and second switches to conduct and turn off complementaryly, controlling the back-to-back switch group to turn off. In this embodiment, the control module is configured to receive at least one command to instruct the power converter to be configured as a first configuration or a second configuration.In some applications, the power converter may have a first configuration and / or a second configuration. Switching between the first and second configurations can be achieved through various switches to different input switch groups and their preceding circuitry (such as back-to-back switch groups and input capacitors). The implementation of this method is understandable to those skilled in the art. This method embodiment is related to the first and second embodiments of the power converter described above, and will not be repeated here.

[0036] The power converter and its control method according to the above embodiments of the present invention include two transformers connected in series on their primary sides to form a primary series group, and an input switch group operating in full-bridge or half-bridge mode. In a first configuration, the primary series group and a capacitor are connected in series between two nodes of the input switch group, and a control module is electrically connected to the input switch group; or, in a second configuration, the nodes of the input switch group are electrically connected to the nodes formed by the two input capacitors connected in series via a back-to-back switch group, and the control module is electrically connected to the input switch group and the back-to-back switch group. In half-bridge or full-bridge mode, the control module controls the input switch group of the first configuration or the input switch group of the second configuration and the back-to-back switch group to form a half-bridge or full-bridge architecture. In full-bridge mode, the control signals of the two switches have a phase shift, thereby solving the application problem of the dual transformer power converter in a wide range of input / output voltages, especially when the input voltage is high, the voltage stress borne by the electronic switches on the secondary side of the transformer can be significantly reduced.

[0037] Although the present invention has been disclosed with reference to preferred embodiments, any person skilled in the art may make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

[0038] 10: Dual Transformer Full-Bridge Converter 11, 21, 71: Transformer Module 12, 22, 72: Input switch groups 13, 23, 74: Output switch group 73: Input capacitor bank 20, 40, 70, 90: Power converters 2C, 7C: Control Module 120, 130: Control Architecture Examples 121, 131: Subtractors 122, 132: Voltage controller 123, 133: PWM generator 124: Phase Shift Generator 125: Complementary Signal Generator 126, 134: Drive circuit 127, 135: DC-DC converters 140, 170: Process Examples 141, 142, 143, 144, 145, 146, 147, 148, 149, 14a, 14b, 14c, 14d, 14e, 14f, 14g, 14h, 14i, 171, 172, 173, 174, 175, 176, 177: Steps Cp, Cin1, Cin2: Input capacitors Cout: Output capacitor E: Voltage error value F: Full Bridge Stage H: Half-bridge stage T: Switching Phase P: Phase shift Q1: First switch Q2: Second switch Q3: Third switch Q4: Fourth Switch QR1: Fifth Switch QR2: Sixth Switch QB: Back-to-back switch assembly Q1_duty: The working cycle of the first switch Q2_duty: The working cycle of the second switch SC1, SC2, SC3, SC4, SR1, SR2, SCB: Control signals V GS_Q1, V GS_Q2, V GS_Q3, V GS_Q4, V DS_SR1, V DS_SR2, V GS_QBB: signal T1, T2: Transformers TS1: Switching Time Tmax: Maximum switching time Vin: Input voltage Vin_max: Input maximum value Vout: Output voltage Iout: Output current Vout_fb: Feedback voltage value Vout_ref: Voltage reference value V: Voltage signal t: time

Claims

1. A power converter, comprising: Two transformers, the primary sides of which are connected in series to form a primary series group; an input switch group, including a first bridge arm and a second bridge arm connected in parallel, the first bridge arm including a first switch and a second switch connected in series, the first switch and the second switch being connected to form a first node, the second bridge arm including a third switch and a fourth switch connected in series, the third switch and the fourth switch being connected to form a second node, the input switch group operating in a full-bridge mode or a half-bridge mode; wherein, the primary series group and an input capacitor are connected in series between the first node and the second node; and a control module electrically connected to the input switch group; the control module is configured to: control the third switch and the fourth switch to be complementaryly turned on and off; in response to the input switch group switching from the full-bridge mode to the half-bridge mode, the duty cycle of the control signal of the first switch, which is asynchronous with the control signal of the fourth switch, gradually decreases to 0, and the duty cycle of the control signal of the second switch, which is asynchronous with the control signal of the third switch, gradually increases to 1; In response to the input switch group switching from the half-bridge mode to the full-bridge mode, the duty cycle of the control signal controlling the first switch gradually increases from 0 to make the control signal of the first switch asynchronous with the control signal of the fourth switch, and the duty cycle of the control signal controlling the second switch gradually decreases from 1 to make the control signal of the second switch asynchronous with the control signal of the third switch, thereby controlling the first switch and the second switch to be turned on and off complementaryly.

2. The power converter as claimed in claim 1, wherein in response to the input switch group switching from the half-bridge mode to the full-bridge mode, there is a phase shift between the control signal of the first switch and the control signal of the fourth switch, the phase shift being within a phase shift range greater than 0 and not greater than 180 degrees.

3. The power converter as claimed in claim 1 or 2, wherein the input capacitor is electrically connected between the first node and the primary series group.

4. The power converter as claimed in claim 1 or 2, wherein the secondary sides of the two transformers are connected in series to form a primary series group, the secondary series group is connected in parallel to an output switch group, and the control module is electrically connected to the output switch group.

5. The power converter as claimed in claim 4, wherein the secondary sides of the two transformers are connected to form a first contact, the output switch group includes a fifth switch and a sixth switch connected in series, the fifth switch and the sixth switch are connected to form a second contact, and an output capacitor is electrically connected between the first contact and the second contact.

6. The power converter of claim 1, wherein the control module is configured to control the input switch group to switch from the full-bridge mode to the half-bridge mode in response to determining that an input voltage value associated with the input switch group is greater than a voltage threshold; and the control module is configured to control the input switch group to switch from the half-bridge mode to the full-bridge mode in response to determining that the input voltage value is less than or equal to the voltage threshold.

7. A power converter, comprising: Two transformers, the primary sides of which are connected in series to form a primary series group; an input switch group, including a first bridge arm and a second bridge arm connected in parallel, the first bridge arm including a first switch and a second switch connected in series, the first switch and the second switch being connected to form a first node, the second bridge arm including a third switch and a fourth switch connected in series, the third switch and the fourth switch being connected to form a second node, the input switch group operating in a full-bridge mode or a half-bridge mode, the primary series group being connected between the first node and the second node; wherein, the first node is electrically connected to a third node formed by two input capacitors connected in series via a back-to-back switch group; and a control module electrically connected to the input switch group and the back-to-back switch group; the control module is configured to: control the third switch and the fourth switch to complementary turn on and off; In response to the input switch group switching from the full-bridge mode to the half-bridge mode, the duty cycle of the control signal of the first switch, which is asynchronous with the control signal of the fourth switch, is gradually reduced to 0; the duty cycle of the control signal of the second switch, which is asynchronous with the control signal of the third switch, is gradually reduced to 0, thus controlling the back-to-back switch group to conduct; In response to the input switch group switching from the half-bridge mode to the full-bridge mode, the duty cycle of the control signal of the first switch is gradually increased from 0 to make the control signal of the first switch asynchronous with the control signal of the fourth switch; the duty cycle of the control signal of the second switch is gradually increased from 0 to make the control signal of the second switch asynchronous with the control signal of the third switch, thus controlling the first switch and the second switch to conduct and turn off complementaryly, thus controlling the back-to-back switch group to turn off.

8. The power converter as claimed in claim 7, wherein in response to the input switch group switching from the half-bridge mode to the full-bridge mode, there is a phase shift between the control signal of the first switch and the control signal of the fourth switch, the phase shift being within a phase shift range greater than 0 and not greater than 180 degrees.

9. The power converter as claimed in claim 7 or 8, wherein the secondary sides of the two transformers are connected in series to form a primary series group, the secondary series group is connected in parallel to an output switch group, and the control module is electrically connected to the output switch group.

10. The power converter as claimed in claim 9, wherein the secondary sides of the two transformers are connected to form a first contact, the output switch group includes a fifth switch and a sixth switch connected in series, the fifth switch and the sixth switch are connected to form a second contact, and an output capacitor is electrically connected between the first contact and the second contact.

11. The power converter of claim 7, wherein the control module is configured to control the input switch group to switch from the full-bridge mode to the half-bridge mode in response to determining that an input voltage value associated with the input switch group is greater than a voltage threshold; and the control module is configured to control the input switch group to switch from the half-bridge mode to the full-bridge mode in response to determining that the input voltage value is less than or equal to the voltage threshold.

12. The power converter as claimed in claim 7 or 8, wherein the two input capacitors are connected in series to form an input capacitor bank, and the input capacitor bank is connected in parallel to the input switch bank.

13. A control method for a power converter, applied to a power converter including two transformers, an input switch group, and a control module; the primary sides of the two transformers are connected in series to form a primary series group; the input switch group includes a first bridge arm and a second bridge arm connected in parallel, the first bridge arm including a first switch and a second switch connected in series, the first switch and the second switch being connected to form a first node, the second bridge arm including a third switch and a fourth switch connected in series, the third switch and the fourth switch being connected to form a second node, the input switch group operating in a full-bridge mode or a half-bridge mode; wherein... In a first configuration, the primary series group and an input capacitor are connected in series between the first node and the second node, and the control module is electrically connected to the input switch group; or, in a second configuration, the first node is electrically connected via a back-to-back switch group to a third node formed by two input capacitors connected in series, and the control module is electrically connected to the input switch group and the back-to-back switch group; the method includes: configuring the control module to: control the third switch and the fourth switch to be complementaryly turned on and off; for the first configuration: in response to the input switch group switching from the full-bridge mode to the half-bridge mode, the duty cycle of the control signal of the first switch, which is asynchronous with the control signal of the fourth switch, is gradually reduced to 0, and the duty cycle of the control signal of the second switch, which is asynchronous with the control signal of the third switch, is gradually increased to 1; In response to the input switch group switching from the half-bridge mode to the full-bridge mode, the duty cycle of the control signal of the first switch gradually increases from 0 to make the control signal of the first switch asynchronous with the control signal of the fourth switch, and the duty cycle of the control signal of the second switch gradually decreases from 1 to make the control signal of the second switch asynchronous with the control signal of the third switch, thereby controlling the first switch and the second switch to be turned on and off complementaryly; For the second configuration: In response to the input switch group switching from the full-bridge mode to the half-bridge mode, the duty cycle of the control signal of the first switch, which is asynchronous with the control signal of the fourth switch, gradually decreases to 0, and the duty cycle of the control signal of the second switch, which is asynchronous with the control signal of the third switch, gradually decreases to 0, thereby controlling the back-to-back switch group to be turned on; In response to the input switch group switching from the half-bridge mode to the full-bridge mode, the duty cycle of the control signal of the first switch is gradually increased from 0 to make the control signal of the first switch asynchronous with the control signal of the fourth switch, the duty cycle of the control signal of the second switch is gradually increased from 0 to make the control signal of the second switch asynchronous with the control signal of the third switch, the first switch and the second switch are controlled to be turned on and off complementaryly, and the back-to-back switch group is turned off.

14. The method as described in claim 13, wherein in response to the input switch group switching from the half-bridge mode to the full-bridge mode, there is a phase shift between the control signal of the first switch and the control signal of the fourth switch, the phase shift being within a phase shift range greater than 0 and not greater than 180 degrees.

15. The method of claim 13, wherein the control module is configured to control the input switch group to switch from the full-bridge mode to the half-bridge mode in response to determining that an input voltage value associated with the input switch group is greater than a voltage threshold; and the control module is configured to control the input switch group to switch from the half-bridge mode to the full-bridge mode in response to determining that the input voltage value is less than or equal to the voltage threshold.

16. The method of claim 13, wherein in the first configuration, the input capacitor is electrically connected between the first node and the primary cascade group.

17. The method as described in claim 13, wherein in the first configuration or the second configuration, the secondary sides of the two transformers are connected in series to form a primary series group, the secondary series group is connected in parallel to an output switch group, and the control module is electrically connected to the output switch group.

18. The method of claim 17, wherein the secondary side connection of the two transformers forms a first contact, the output switch group includes a fifth switch and a sixth switch connected in series, the fifth switch and the sixth switch are connected to form a second contact, and an output capacitor is electrically connected between the first contact and the second contact.

19. The method of claim 13, wherein in the second configuration, the two input capacitors are connected in series to form an input capacitor bank, and the input capacitor bank is connected in parallel to the input switch bank.

20. The method of claim 13, wherein the control module is configured to receive at least one command indicating that the power converter is configured to the first configuration or the second configuration.

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