Voltage conversion device, control method, and power supply device

Abstract

The application provides a voltage conversion device, a control method and a power supply device. The voltage conversion device comprises a three-phase half-bridge circuit, a three-phase resonance circuit, a three-phase transformer, a control circuit and a switching unit. The three-phase half-bridge circuit comprises three switching bridge arms. One end of each of the three primary windings in the three-phase transformer is used to receive the voltage output by the three-phase half-bridge circuit through the three-phase resonance circuit, and the other end of each of the three primary windings in the three-phase transformer is connected to form a tap. One end of the switching unit is connected to the tap, and the other end of the switching unit is connected to the ground or the bridge arm midpoint of any one of the three switching bridge arms. In response to the output power or the input power of the voltage conversion device being lower than a preset power value, the control circuit controls the first end of the switching unit and the second end of the switching unit to be conductive.

Description

Technical Field

[0001] This application relates to the field of power electronics, and in particular to a voltage conversion device, control method and power supply equipment. Background Technology

[0002] In existing three-phase interleaved parallel LLC resonant topologies, phase shielding is often used to allow the topology to operate in three-phase, two-phase, or single-phase mode depending on load variations.

[0003] When this topology operates in single-phase mode, although the number of switching transistors is single-phase, the resonant capacitor, resonant inductor, transformer, and secondary rectifier diodes still have the same number as in two-phase operation. Therefore, the power conversion efficiency of this topology is not optimal in single-phase mode, and consequently, it does not achieve high efficiency across the entire load range. Thus, reducing the losses of the three-phase interleaved parallel LLC resonant topology in single-phase mode to achieve improved efficiency across the entire load range has become a pressing technical problem to be solved. Summary of the Invention

[0004] In view of this, this application provides a voltage conversion device, control method and power supply equipment that can reduce the loss of a three-phase interleaved parallel LLC resonant topology in single-phase mode, so as to achieve high efficiency across the entire load range.

[0005] In a first aspect, this application provides a voltage conversion device, including a three-phase half-bridge circuit, a three-phase resonant circuit, a three-phase transformer, a control circuit, and a switching unit; the three-phase half-bridge circuit includes three switching arms; one end of each of the three primary windings of the three-phase transformer is used to receive the voltage output by the three-phase half-bridge circuit through the three-phase resonant circuit, and the other ends of the three primary windings of the three-phase transformer are connected to form a tap; one end of the switching unit is connected to the tap, and the other end of the switching unit is connected to ground or to the midpoint of any one of the three switching arms; in response to the output power or input power of the voltage conversion device being lower than a preset power value, the control circuit controls one end of the switching unit and the other end of the switching unit to conduct.

[0006] It is understandable that by setting a switching unit to connect the tap formed by the three primary windings to ground, or to connect the tap formed by the three primary windings to the midpoint of any one of the three switching bridge arms, the voltage converter can operate in single-phase mode with a half-bridge LLC or full-bridge LLC structure. In this way, the voltage converter can reduce the use of resonant capacitors, resonant inductors, and transformers, thereby reducing energy loss in single-phase mode and improving power conversion efficiency. This facilitates efficiency improvement of the voltage converter across the entire load range.

[0007] In conjunction with the first aspect, in one possible implementation, the voltage conversion device can operate in single-phase mode, two-phase mode, and three-phase mode; in response to the output power or input power of the voltage conversion device being within a first preset range, the voltage conversion device operates in three-phase mode, and the control circuit controls the three switching arms to operate normally; in response to the output power or input power of the voltage conversion device being within a second preset range, the voltage conversion device operates in two-phase mode, and the control circuit controls any two of the three switching arms to operate normally; in response to the output power or input power of the voltage conversion device being within a third preset range, the voltage conversion device operates in single-phase mode, and the control circuit controls any one of the three switching arms to operate normally, or the control circuit controls any two of the three switching arms to operate normally; wherein, the maximum value of the second preset range is less than the minimum value of the first preset range; the maximum value of the third preset range is less than the minimum value of the second preset range, and the minimum value of the second preset range is a preset power value.

[0008] It is understandable that the output power or input power of a voltage converter varies according to the load power. When the load power is within different ranges, the voltage converter can switch to different operating modes accordingly to improve its efficiency across the entire load range.

[0009] In conjunction with the first aspect, in one possible implementation, the switching unit is a switching transistor, the first end of the switching unit is connected to a tap, the second end of the switching unit is connected to ground, and the third end of the switching unit is connected to a control circuit; in response to the output power or input power of the voltage conversion device being lower than a preset power value, the control circuit controls one of the three switching arms to operate normally, controls the switching transistors in the other two of the three switching arms to turn off, and controls the first end of the switching unit to be connected to the second end of the switching unit.

[0010] It is understandable that by connecting one end of the three primary windings to ground through the switching unit, and controlling the switching unit to conduct, one normally functioning switch arm in the three-phase half-bridge circuit can be turned on. This allows the voltage conversion device to form a half-bridge LLC structure, reducing the use of resonant capacitors, resonant inductors, and transformers, thereby reducing energy loss in single-phase mode and improving power conversion efficiency.

[0011] In conjunction with the first aspect, in one possible implementation, the switching unit is a switching transistor. The first end of the switching unit is connected to a tap, the second end of the switching unit is connected to the midpoint of any one of the three switching bridge arms, and the third end of the switching unit is connected to a control circuit. In response to the output power or input power of the voltage conversion device being lower than a preset power value, the control circuit controls two of the three switching bridge arms to operate normally, controls the switching transistor in the other of the three switching bridge arms to turn off, and controls the first end of the switching unit to be connected to the second end of the switching unit, wherein the switching bridge arm connected to the second end of the switching unit is one of the two normally operating switching bridge arms.

[0012] It can be understood that by connecting a tap formed by one end of the three primary windings to the midpoint of any one of the three switching arms via a switching unit, and controlling the switching unit to conduct, two normally functioning switching arms in the three-phase half-bridge circuit can be switched on. This allows the voltage conversion device to form a full-bridge LLC structure, reducing the use of resonant capacitors, resonant inductors, and transformers, thereby reducing energy loss in single-phase mode and improving power conversion efficiency.

[0013] In conjunction with the first aspect, in one possible implementation, in response to the output power of the voltage conversion device being lower than a first preset power value, the control circuit controls one end of the switching unit and the other end of the switching unit to be turned on.

[0014] In conjunction with the first aspect, in one possible implementation, the voltage conversion device includes a detection circuit, which includes a sampling resistor and a signal amplification unit. The sampling resistor is located between the output terminal of the voltage conversion device and the rectifier circuit of the voltage conversion device. The signal amplification unit is used to acquire and amplify the voltage across the sampling resistor and obtain a sampling voltage. The control circuit is used to obtain an output current based on the sampling voltage and the resistance value of the sampling resistor, and to obtain an output power based on the output current and the sampling voltage.

[0015] In conjunction with the first aspect, in one possible implementation, the control circuit is used to obtain the switching frequency of the switching transistors in the three switching arms, and to obtain the output power based on the switching frequency and the correspondence between the switching frequency and the output power.

[0016] In conjunction with the first aspect, in one possible implementation, in response to the input power of the voltage conversion device being lower than a second preset power value, the control circuit controls one end of the switching unit and the other end of the switching unit to be turned on.

[0017] In conjunction with the first aspect, in one possible implementation, the voltage conversion device includes a detection circuit, which includes a sampling resistor and a signal amplification unit. The sampling resistor is located between the input voltage source of the voltage conversion device and the three-phase half-bridge circuit. The signal amplification unit is used to acquire and amplify the voltage across the sampling resistor and obtain the sampling voltage. The control circuit is used to obtain the output current based on the sampling voltage and the resistance value of the sampling resistor, and to obtain the input power based on the input current and the sampling voltage.

[0018] Secondly, this application provides a control method for a voltage conversion device, the voltage conversion device including a three-phase half-bridge circuit, a three-phase resonant circuit, a three-phase transformer, a control circuit, and a switching unit; the three-phase half-bridge circuit includes three switching arms; one end of each of the three primary windings of the three-phase transformer is used to receive the voltage output by the three-phase half-bridge circuit through the three-phase resonant circuit, and the other ends of the three primary windings of the three-phase transformer are connected to form a tap; one end of the switching unit is connected to the tap, and the other end of the switching unit is connected to ground or to the midpoint of any one of the three switching arms; the method includes: obtaining the output power or input power of the voltage conversion device; and responding to the output power or input power being lower than a preset power value, controlling one end of the switching unit and the other end of the switching unit to conduct.

[0019] In conjunction with the second aspect, in one possible implementation, the control method for the voltage conversion device includes: controlling three switching arms to operate normally in response to the output power or input power of the voltage conversion device being within a first preset range; controlling any two of the three switching arms to operate normally in response to the output power or input power of the voltage conversion device being within a second preset range; controlling any one of the three switching arms to operate normally, or controlling any two of the three switching arms to operate normally in response to the output power or input power of the voltage conversion device being within a third preset range; wherein the maximum value of the second preset range is less than the minimum value of the first preset range; the maximum value of the third preset range is less than the minimum value of the second preset range, and the minimum value of the second preset range is a preset power value.

[0020] In conjunction with the second aspect, in one possible implementation, the first end of the switching unit is connected to a tap, the second end of the switching unit is connected to ground, and the third end of the switching unit is connected to a control circuit. The control method of the voltage conversion device includes: in response to the output power or input power of the voltage conversion device being lower than a preset power value, controlling one of the three switching arms to operate normally, controlling the switching transistors in the other two of the three switching arms to turn off, and controlling the first end of the switching unit to be connected to the second end of the switching unit.

[0021] In conjunction with the second aspect, in one possible implementation, the first end of the switching unit is connected to a tap, the second end of the switching unit is connected to the midpoint of any one of the three switching arms, and the third end of the switching unit is connected to a control circuit. The control method of the voltage conversion device includes: in response to the output power or input power of the voltage conversion device being lower than a preset power value, controlling two of the three switching arms to operate normally, controlling the switch in the other of the three switching arms to turn off, and controlling the first end of the switching unit to be connected to the second end of the switching unit, wherein the switching arm connected to the second end of the switching unit is one of the two normally operating switching arms.

[0022] Thirdly, this application provides a power supply device, comprising: an AC-DC voltage conversion unit and a voltage conversion device. The AC-DC voltage conversion unit converts AC voltage into DC input voltage, and the voltage conversion device receives the DC input voltage output by the AC-DC voltage conversion unit and outputs a DC output voltage after DC voltage conversion. The voltage conversion device includes a three-phase half-bridge circuit, a three-phase resonant circuit, a three-phase transformer, a control circuit, and a switching unit. The three-phase half-bridge circuit includes three switching arms. One end of each of the three primary windings of the three-phase transformer is used to receive the voltage output by the three-phase half-bridge circuit through the three-phase resonant circuit. The other ends of the three primary windings of the three-phase transformer are connected to form a tap. One end of the switching unit is connected to the tap, and the other end of the switching unit is connected to ground or to the midpoint of any one of the three switching arms. In response to the output power or input power of the voltage conversion device being lower than a preset power value, the control circuit controls one end of the switching unit and the other end of the switching unit to conduct.

[0023] Furthermore, the technical effects of any possible implementation in the second and third aspects can be found in the technical effects of different implementations in the first aspect, and will not be repeated here. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of an exemplary voltage conversion device.

[0025] Figure 2 for Figure 1 A schematic diagram of the equivalent circuit of a medium voltage converter in two-phase mode.

[0026] Figure 3 for Figure 1 A schematic diagram of the equivalent circuit of the medium voltage conversion device in single-phase mode.

[0027] Figure 4 This is a schematic diagram of a voltage conversion device provided in an embodiment of this application.

[0028] Figure 5 for Figure 4 A schematic diagram of the equivalent circuit of a medium voltage converter in two-phase mode.

[0029] Figure 6 for Figure 4 A schematic diagram of the equivalent circuit of the medium voltage conversion device in single-phase mode.

[0030] Figure 7 This is another schematic diagram of the voltage conversion device provided in the embodiments of this application.

[0031] Figure 8 for Figure 7 A schematic diagram of the equivalent circuit of the medium voltage conversion device in single-phase mode.

[0032] Figure 9 This is another schematic diagram of the voltage conversion device provided in the embodiments of this application.

[0033] Figure 10 This is another schematic diagram of the voltage conversion device provided in the embodiments of this application.

[0034] Figure 11 This is a flowchart illustrating the control method of the voltage conversion device provided in the embodiments of this application.

[0035] Figure 12 This is a schematic diagram of a power supply device provided in an embodiment of this application. Detailed Implementation

[0036] In the description of this application, the connection relationship described herein refers to a direct or indirect connection. For example, the connection between A and B can be a direct connection between A and B, or an indirect connection between A and B through one or more other electrical components. For example, A can be directly connected to C, and C can be directly connected to B, thus achieving a connection between A and B through C. It is also understood that the "A connects to B" described in this application can be a direct connection between A and B, or an indirect connection between A and B through one or more other electrical components.

[0037] In the description of this application, unless otherwise stated, " / " means "or". For example, A / B can mean A or B. The "and / or" in this document is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A exists alone, A and B exist simultaneously, and B exists alone.

[0038] In the description of this application, the words "first," "second," etc., are used only to distinguish different objects and do not limit the quantity or order of execution, nor do they imply that they must be different. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion.

[0039] To enable those skilled in the art to better understand the technical solutions provided in this application, the application scenarios of the technical solutions provided in this application will be introduced below.

[0040] Figure 1 This is a schematic diagram of an exemplary voltage conversion device 200.

[0041] The voltage conversion device 200 is used to convert a DC input voltage into a DC output voltage. The voltage conversion device 200 includes a three-phase half-bridge circuit 210, a three-phase resonant circuit 220, a three-phase transformer 230, a three-phase rectifier bridge circuit 240, and a control circuit 250.

[0042] The three-phase half-bridge circuit 210 is used to receive DC power. After voltage conversion, the DC input voltage is transmitted to the three-phase primary winding of the three-phase transformer 230 via the three-phase resonant circuit 220. The output voltage of the three-phase half-bridge circuit 210 can be, for example, a square wave voltage. AC power is transmitted from the three-phase primary winding of the three-phase transformer 230 to the three-phase secondary winding via magnetic core coupling. The three-phase rectifier bridge circuit 240 converts the AC power output from the three-phase secondary winding of the three-phase transformer 230 into DC power. The control circuit 250 outputs a drive signal G, which controls the switching transistors in the three-phase half-bridge circuit 210 to turn on or off.

[0043] The three-phase half-bridge circuit 210 includes three switch arms connected in parallel, namely the first switch arm, the second switch arm, and the third switch arm.

[0044] For example, the first switch bridge arm includes switch tube Mup1 and switch tube Mdn1. The connection point of switch tube Mup1 and switch tube Mdn1 serves as the midpoint of the first switch bridge arm. The second switch bridge arm includes switch tube Mup2 and switch tube Mdn2. The connection point of switch tube Mup2 and switch tube Mdn2 serves as the midpoint of the second switch bridge arm. The third switch bridge arm includes switch tube Mup3 and switch tube Mdn3. The connection point of switch tube Mup3 serves as the midpoint of the third switch bridge arm.

[0045] The three-phase transformer 230 includes transformer T1, transformer T2 and transformer T3.

[0046] The three-phase resonant circuit 220 is used to receive the voltage output from the three-phase half-bridge circuit 210 and output it to the three-phase primary winding of the three-phase transformer 230.

[0047] For example, the three-phase resonant circuit 220 includes a first resonant unit, a second resonant unit, and a third resonant unit. The first resonant unit includes resonant inductors Lr1 and Cr1, the second resonant unit includes resonant inductors Lr2 and Cr2, and the third resonant unit includes resonant inductors Lr3 and Cr3.

[0048] In this circuit, one end of resonant inductor Lr1 is connected to the midpoint of the first switching bridge arm, and the other end of resonant inductor Lr1 is connected to one end of the primary winding of transformer T1. The other end of the primary winding of transformer T1 is connected to one end of resonant capacitor Cr1. One end of resonant inductor Lr2 is connected to the midpoint of the second switching bridge arm, and the other end of resonant inductor Lr2 is connected to one end of the primary winding of transformer T2. The other end of the primary winding of transformer T2 is connected to one end of resonant capacitor Cr2. One end of resonant inductor Lr3 is connected to the midpoint of the third switching bridge arm, and the other end of resonant inductor Lr3 is connected to one end of the primary winding of transformer T3. The other end of resonant capacitor Cr1, one end of resonant capacitor Cr2, and one end of resonant capacitor Cr3 are connected together.

[0049] The three-phase rectifier bridge circuit 240 includes a first rectifier unit, a second rectifier unit, and a third rectifier unit. The first rectifier unit includes rectifier diodes D11 and D12, the second rectifier unit includes rectifier diodes D21 and D22, and the third rectifier unit includes rectifier diodes D31 and D32.

[0050] One end of one secondary winding of transformer T1 is connected to one end of the other secondary winding, and the node between them is connected to ground. The other end of one secondary winding is connected to the anode of rectifier tube D11, and the other end of the other secondary winding is connected to the anode of rectifier tube D12. The cathodes of rectifier tube D11 and rectifier tube D12 are connected. One end of one secondary winding of transformer T2 is connected to one end of the other secondary winding, and the node between them is connected to ground. The other end of one secondary winding of transformer T2 is connected to the anode of rectifier tube D21, and the other end of the other secondary winding is connected to the anode of rectifier tube D22. The cathodes of rectifier tube D21 and rectifier tube D22 are connected. One end of one secondary winding of transformer T3 is connected to one end of the other secondary winding, and the node between them is connected to ground. One end of the secondary winding of transformer T3 is connected to the anode of rectifier diode D31, and the other end of the secondary winding is connected to the anode of rectifier diode D32. The cathodes of rectifier diodes D31 and D32 are connected. The nodes between the cathodes of rectifier diodes D11 and D12, D21 and D22, and D31 and D32 are connected, and these nodes are also connected to the positive terminal of the output capacitor Cout. The negative terminal of the output capacitor Cout is connected to ground. The voltage across the output capacitor Cout is the output voltage Vout of the voltage converter 200.

[0051] The voltage conversion device 200 includes three operating modes: three-phase mode, two-phase mode, and single-phase mode.

[0052] like Figure 1 As shown, the control circuit 250 controls all three switching arms in the three-phase half-bridge circuit 210 to operate normally, so the voltage conversion device 200 operates in three-phase mode. It can be understood that when the switching arms are operating normally, the upper and lower switching transistors alternately conduct. Taking the first switching arm as an example, when the first switching arm is operating normally, switching transistors Mup1 and Mdn1 alternately conduct once in each switching cycle.

[0053] In three-phase mode, all components in the voltage conversion device 200 operate normally to meet the heavy load requirements of the output Vout.

[0054] In two-phase mode, the control circuit 250 controls one of the three switch arms to stop working, while controlling the other two switch arms to work normally.

[0055] Please refer to the following: Figure 2The diagram shows the equivalent circuit of the voltage conversion device 200 operating in two-phase mode. For example, in two-phase mode, the control circuit 250 controls the switching transistor in the third switching arm to remain off and controls the switching transistors in the first and second switching arms to operate normally. At this time, the voltage conversion device 200 operates in two-phase mode.

[0056] In two-phase mode, the switching transistors (Mup3, Mdn3) in the third switching bridge arm remain off. Thus, the resonant inductor Lr3, resonant capacitor Cr3, transformer T3 in the third resonant unit, and rectifier diodes D31 and D32 in the third rectifier unit are all in a non-operating state, meaning no current flows through them.

[0057] It is understandable that, compared to the three-phase mode, the voltage conversion device 100 can reduce the losses of a set of transformers T3, resonant inductor Lr3, resonant capacitor Cr3, and switching transistors (Mup3, Mdn3) in the two-phase mode, thus improving the power supply efficiency under light load.

[0058] In single-phase mode, the control circuit 250 controls two of the three bridge arm switches to stop working, while controlling the other bridge arm switch to work normally.

[0059] Please refer to the following: Figure 3 The diagram shows the voltage conversion device 200 operating in single-phase mode. For example, in single-phase mode, the control circuit 250 controls the switching transistors in the first switching bridge arm to operate normally, and controls the switching transistors in the second and third switching bridge arms to remain off. At this time, the voltage conversion device 200 operates in single-phase mode.

[0060] In the first switching bridge arm, switching transistors Mup1 and Mdn1 are alternately turned on. The resonant inductor Lr1, resonant capacitor Cr1, transformer T1, rectifier diode D11, rectifier diode D12, etc., corresponding to the first switching bridge arm are all in working state.

[0061] It is understandable that in single-phase mode, among the two switch arms that remain completely off, the resonant unit, transformer, and rectifier unit corresponding to one switch arm are all in operation, while the resonant unit and transformer corresponding to the other switch arm are completely short-circuited and stop working. For example, in the third switch arm, switches Mup3 and Mdn3 remain off, and the corresponding resonant inductor Lr3, resonant capacitor Cr3, and transformer T3 are completely short-circuited and thus stop working. In the second switch arm, switches Mup2 and Mdn2 remain off, but the corresponding resonant inductor Lr2, resonant capacitor Cr2, and transformer T2 remain in operation.

[0062] Obviously, when the voltage converter 200 is in single-phase mode, the resonant inductor, transformer, resonant capacitor, and secondary rectifier tubes are still in the same quantity as in two-phase mode, which does not achieve the optimal configuration for improving the conversion efficiency of the voltage converter 200.

[0063] To address the aforementioned technical problems, embodiments of this application provide a voltage conversion device. The voltage conversion device provided in this application includes a switching unit. When the voltage conversion device needs to operate in single-phase mode, this switching unit allows the voltage conversion device to operate in either half-bridge single-phase mode or full-bridge single-phase mode, thereby improving the conversion efficiency of the voltage conversion device under light load conditions.

[0064] This application provides a voltage conversion device. The voltage conversion device includes a three-phase half-bridge circuit, a three-phase resonant circuit, a three-phase transformer, a control circuit, and a switching unit. The three-phase half-bridge circuit includes three switching arms. One end of each of the three primary windings of the three-phase transformer is used to receive the voltage output from the three-phase half-bridge circuit through the three-phase resonant circuit. The other ends of the three primary windings of the three-phase transformer are connected to form a tap. One end of the switching unit is connected to the tap, and the other end of the switching unit is connected to ground or to the midpoint of any one of the three switching arms. In response to the output power or input power of the voltage conversion device being lower than a preset power value, the control circuit controls one end of the switching unit and the other end of the switching unit to conduct.

[0065] The circuit structure and working principle of the voltage conversion device are explained in detail below through Examples 1 to 5.

[0066] Example 1: In Embodiment 1, the voltage conversion device includes a three-phase half-bridge circuit, a three-phase resonant circuit, a three-phase transformer, a control circuit, and a switching unit. The three-phase half-bridge circuit includes three switching arms. One end of each of the three primary windings of the three-phase transformer is used to receive the voltage output from the three-phase half-bridge circuit through the three-phase resonant circuit, and the other ends of the three primary windings of the three-phase transformer are connected to form a tap. One end of the switching unit is connected to the tap, and the other end of the switching unit is connected to ground. In response to the output power of the voltage conversion device being lower than a preset power value, the control circuit controls one end of the switching unit and the other end of the switching unit to conduct.

[0067] Please see Figure 4 The image shows a voltage conversion device 100 provided in Embodiment 1 of this application. The voltage conversion device 100 includes a three-phase half-bridge circuit 10, a three-phase resonant circuit 20, a three-phase transformer 30, a three-phase rectifier bridge circuit 40, a control circuit 50, and a switching unit 60.

[0068] The three-phase half-bridge circuit 10 receives the DC input voltage. After voltage conversion, the DC input voltage is transmitted to one end of the three primary windings of the three-phase transformer 30 via the three-phase resonant circuit 20. The output voltage of the three-phase half-bridge circuit 10 can be, for example, a square wave voltage. The other ends of the three primary windings of the three-phase transformer 30 are connected to form a tap. AC power is transmitted from the three-phase primary windings of the three-phase transformer 30 to the three-phase secondary windings via magnetic core coupling. The three-phase rectifier bridge circuit 40 converts the AC power output from the three-phase secondary windings of the three-phase transformer 30 into DC power. One end of the switching unit 60 is connected to the tap, and the other end is connected to ground. The control circuit 50 outputs a drive signal Vg and a drive signal Vd. The drive signal Vg controls the switching transistors in the three-phase half-bridge circuit 10 to turn on or off, and the control signal Vd controls the connection between one end of the switching unit 60 and the other end of the switching unit 60.

[0069] The three-phase half-bridge circuit 10 includes three parallel switching arms: a first switching arm, a second switching arm, and a third switching arm. Exemplarily, the first switching arm includes switching transistors Q1 and Q2. The connection point P1 between switching transistors Q1 and Q2 serves as the midpoint of the first switching arm. The second switching arm includes switching transistors Q3 and Q4. The connection point P2 between switching transistors Q3 and Q4 serves as the midpoint of the second switching arm. The third switching arm includes switching transistors Q5 and Q6. The connection point P3 between switching transistors Q5 and Q6 serves as the midpoint of the third switching arm. The two ends of the three switching arms are used to connect to the positive and negative terminals of the input voltage source Vin, respectively. The control terminals of the switching transistors (Q1 to Q6) in the first, second, and third switching arms are used to receive a drive signal Vg. The drive signal Vg is used to control the switching transistors to alternately turn off and on, so that the three-phase half-bridge circuit 10 converts DC power into AC voltage.

[0070] In one embodiment, the switching transistor in the three-phase half-bridge circuit 10 can be a metal-oxide-semiconductor field-effect transistor (MOS) or a silicon carbide MOS transistor. Accordingly, the control terminal of the switching transistor is the gate of the MOS transistor.

[0071] The three-phase resonant circuit 20 is used to receive the voltage output from the three-phase half-bridge circuit 10 and output the three-phase primary winding of the three-phase transformer 30.

[0072] For example, the three-phase resonant circuit 20 includes a first resonant unit, a second resonant unit, and a third resonant unit. The first resonant unit includes a resonant capacitor Cr1 and a resonant inductor Lr1 connected in series. One end of the resonant capacitor Cr1 is connected to the midpoint P1 of the first switching bridge arm, and the other end of the resonant capacitor Cr1 is connected to one end of the resonant capacitor Cr1. The other end of the resonant inductor Lr1 is connected to the three-phase transformer 30. The second resonant unit includes a resonant capacitor Cr2 and a resonant inductor Lr2 connected in series. One end of the resonant capacitor Cr2 is connected to the midpoint P2 of the second switching bridge arm, and the other end of the resonant capacitor Cr2 is connected to one end of the resonant capacitor Cr2. The other end of the resonant inductor Lr3 is connected to the three-phase transformer 30. The third resonant unit includes a resonant capacitor Cr3 and a resonant inductor Lr3 connected in series. One end of the resonant capacitor Cr3 is connected to the midpoint P3 of the third switching bridge arm, and the other end of the resonant capacitor Cr3 is connected to one end of the resonant capacitor Cr3. The other end of the resonant inductor Lr3 is connected to the three-phase transformer 30.

[0073] The three-phase transformer 30 includes transformer T1, transformer T2, and transformer T3. Transformer T1 includes a primary winding Lm1, a first secondary winding Ls11, and a second secondary winding Ls12. Transformer T2 includes a primary winding Lm2, a first secondary winding Ls21, and a second secondary winding Ls22. Transformer T3 includes a primary winding Lm3, a first secondary winding Ls31, and a second secondary winding Ls32.

[0074] For example, one end of the primary winding Lm1 of transformer T1 is connected to the other end of the resonant inductor Lr1, one end of the primary winding Lm2 of transformer T2 is connected to the other end of the resonant inductor Lr2, and one end of the primary winding Lm13 of transformer T3 is connected to the other end of the resonant inductor Lr3. The other ends of the primary windings Lm1, Lm2, and Lm3 of transformer T1 are connected to form a tap P0.

[0075] One end of the first secondary winding Ls11 of transformer T1 is connected to one end of the second secondary winding Ls12. One end of the first secondary winding Ls21 of transformer T2 is connected to one end of the second secondary winding Ls22. One end of the first secondary winding Ls31 of transformer T3 is connected to one end of the second secondary winding Ls32.

[0076] The three-phase rectifier bridge circuit 40 includes a first rectifier unit, a second rectifier unit, and a third rectifier unit. The first rectifier unit includes rectifier diodes S1 and S2, the second rectifier unit includes rectifier diodes S3 and S4, and the third rectifier unit includes rectifier diodes S5 and S6.

[0077] One end of rectifier tube S1 is connected to the other end of the first secondary winding Ls11, and one end of rectifier tube S2 is connected to the other end of the second secondary winding Ls12. The other ends of rectifier tube S1 and rectifier tube S2 are connected together. One end of rectifier tube S3 is connected to the other end of the first secondary winding Ls21, and one end of rectifier tube S4 is connected to the other end of the second secondary winding Ls22. The other ends of rectifier tube S3 and rectifier tube S4 are connected together. One end of rectifier tube S5 is connected to the other end of the first secondary winding Ls31, and one end of rectifier tube S6 is connected to the other end of the second secondary winding Ls32. The other ends of rectifier tube S5 and rectifier tube S6 are connected together.

[0078] The nodes between the first secondary winding Ls11 and the second secondary winding Ls12, the nodes between the first secondary winding Ls21 and the second secondary winding Ls22, and the nodes between the first secondary winding Ls31 and the second secondary winding Ls32 are connected to form node P4. The nodes between rectifier tubes S1 and S2, the nodes between rectifier tubes S3 and S4, and the nodes between rectifier tubes S5 and S6 are connected to form node P5.

[0079] One end of the output capacitor Cout is connected to node P4, and the other end is connected to node P5. The voltage across the output capacitor Cout is the output voltage Vout of the voltage converter 100.

[0080] In this embodiment, one end of the switching unit 60 is connected to tap P0, and the other end of the switching unit 60 is connected to ground. It can be understood that the negative terminal of the input voltage source Vin is connected to ground. Therefore, the other end of the switching unit 60 can be connected to the negative terminal of the input voltage source Vin.

[0081] For example, the switching unit 60 is a switching transistor. The first terminal of the switching transistor is connected to tap P0, and the second terminal of the switching transistor is connected to ground. The third terminal of the switching transistor is connected to the control circuit 50, and the third terminal is the control terminal, used to receive the drive signal Vd output by the control circuit 50.

[0082] In this embodiment, the control circuit 50 outputs drive signals Vg and Vd. Drive signal Vg is used to turn the switching transistors (Q1 to Q6) in the three-phase half-bridge circuit 10 on and off. Drive signal Vd is used to turn the switching transistors in the switching unit on and off.

[0083] In some embodiments, the rectifier diodes in the three-phase rectifier bridge circuit 40 are all MOSFETs. The control circuit 50 is also used to output a drive signal Vs, which is used to drive the rectifier diodes (S1 to S6) in the three-phase rectifier bridge circuit 40 to turn on and off.

[0084] In this embodiment, the voltage conversion device 100 includes three operating modes: three-phase mode, two-phase mode, and single-phase mode. In response to the output power of the voltage conversion device 100 being within a first preset range, the voltage conversion device 100 operates in three-phase mode, and the control circuit 50 controls the three switching arms to operate normally. In response to the output power of the voltage conversion device 100 being within a second preset range, the voltage conversion device 100 operates in two-phase mode, and the control circuit 50 controls any two of the three switching arms to operate normally. In response to the output power of the voltage conversion device 100 being within a third preset range, the voltage conversion device 100 operates in single-phase mode, and the control circuit 50 controls any one of the three switching arms to operate normally. The maximum value of the second preset range is less than the minimum value of the first preset range; the maximum value of the third preset range is less than the minimum value of the second preset range, and the minimum value of the second preset range is a preset power value.

[0085] like Figure 4 As shown, in three-phase mode, the control circuit 50 controls the first terminal and the second terminal of the switching unit 60 to be de-conductive, and the control circuit 50 controls the three switching bridge arms to operate normally. Thus, all components of the voltage conversion device 100 operate normally.

[0086] In two-phase mode, the control circuit 50 controls the first end of the switching unit 60 and the second end of the switching unit to not conduct, and the control circuit 50 controls any two of the three switching arms to work normally.

[0087] It is understandable that when the output power of the voltage conversion device 100 is high, for example, within the first preset range, the voltage conversion device 100 needs to use three switching bridge arms, and thus use all components to work, in order to improve the power conversion efficiency of the voltage conversion device 100.

[0088] Please refer to the following: Figure 5 As shown Figure 4 A schematic diagram of the equivalent circuit of the medium voltage conversion device 100 in two-phase mode.

[0089] In response to the output power of the voltage converter 100 being within a second preset range, the control circuit 50 controls the voltage converter 100 to switch to two-phase mode. Specifically, the control circuit 50 controls the first and second switching bridge arms to operate normally, and controls the switching transistors (Q5, Q6) in the third switching bridge arm to remain off. Thus, the three-phase half-bridge circuit 10 of the voltage converter 100 forms a full-bridge structure.

[0090] It should be understood that normal operation of the first and second switching arms means that switching transistors Q1 and Q2 in the first switching arm are periodically and alternately turned on, and switching transistors Q3 and Q4 in the second switching arm are periodically and alternately turned on. When switching transistors Q5 and Q6 in the third switching arm are turned off, no current flows through the resonant capacitor Cr3 and resonant inductor Lr3 in the third resonant unit, the transformer T3, or the rectifier transistors S5 and S6 in the third rectifier unit.

[0091] It is understandable that when the output power of the voltage conversion device 100 is generally low, for example, within the second preset range, the voltage conversion device 100 can achieve the required output power using two switching bridge arms. This can reduce the use of some components and thus improve the power conversion efficiency of the voltage conversion device 100.

[0092] In single-phase mode, the control circuit 50 controls the first end of the switching unit 60 and the second end of the switching unit to conduct, and the control circuit 50 controls any one of the three switching arms to work normally.

[0093] Please refer to the following: Figure 6 As shown Figure 4 A schematic diagram of the equivalent circuit of the medium voltage conversion device 100 in single-phase mode.

[0094] In response to the output power of the voltage converter 100 being lower than a preset power value, i.e., the output power being within a third preset range, the control circuit 50 controls the voltage converter 100 to switch to single-phase mode. Specifically, the control circuit 50 controls one end of the switching unit 60 and the other end of the switching unit 60 to be turned on, controls the first switching bridge arm of the three switching bridge arms to operate normally, and controls the switching transistors (Q4, Q5) in the second switching bridge arm and the switching transistors (Q5, Q6) in the third switching bridge arm to remain off. In this way, the three-phase half-bridge circuit 10 of the voltage converter 100 forms a half-bridge structure.

[0095] like Figure 6 As shown, when switch Q1 is on and switch Q2 is off, a current path is formed between the positive terminal of the input voltage source Vin, the midpoint P1 of the first switching bridge arm, the resonant capacitor Cr1, the resonant inductor Lr1, the primary winding Lm1 of transformer T1, the switching unit 60, and the negative terminal of the output voltage source Vin. When switch Q1 is off and switch Q2 is on, a current path is formed between the midpoint P1 of the first switching bridge arm, the resonant capacitor Cr1, the resonant inductor Lr1, the primary winding Lm1 of transformer T1, the switching unit 60, and switch Q2.

[0096] It should be understood that normal operation of the first switching arm means that switching transistors Q1 and Q2 in the first switching arm periodically alternately conduct. When switching transistors Q5 and Q6 in the second switching arm remain off, no current flows through the resonant capacitor Cr2 and resonant inductor Lr2 in the second resonant unit, the transformer T2, or the rectifier diodes S3 and S5 in the second rectifier unit. When switching transistors Q5 and Q6 in the third switching arm remain off, no current flows through the resonant capacitor Cr3 and resonant inductor Lr3 in the third resonant unit, the transformer T3, or the rectifier diodes S5 and S6 in the third rectifier unit.

[0097] It is understandable that by setting the switching unit 60 to connect the taps formed by the three primary windings and ground, the voltage conversion device 100 can operate in single-phase mode with a half-bridge LLC structure. In this way, the voltage conversion device 100 can reduce the use of resonant capacitors, resonant inductors, and transformers, thereby reducing energy loss and improving power conversion efficiency. For example, compared to the voltage conversion device 200 in single-phase mode, the voltage conversion device 100 reduces the use of resonant capacitor Cr2, resonant inductor Lr2, transformer T2, rectifier S3, and rectifier S4.

[0098] In this embodiment, the voltage conversion device 100 further includes a detection circuit 70. The detection circuit 70 is used to detect the output power of the output terminal Vout of the voltage conversion device 100. It is understood that this embodiment does not limit the specific structure of the detection circuit 70.

[0099] In one possible implementation, the detection circuit 70 includes a sampling resistor Rs and a signal amplification unit 71. The sampling resistor Rs is located between the output terminal Vout and the rectifier circuit of the voltage conversion device 100.

[0100] For example, one end of the sampling resistor Rs is connected to the negative terminal of the output voltage Vout, and the other end is connected to node P5. The two input terminals of the signal amplification unit 71 are respectively connected to the two ends of the sampling resistor Rs. The output terminal of the signal amplification unit 71 is connected to the control circuit 50. The signal amplification unit 71 is used to amplify the voltage across the sampling resistor Rs to obtain the sampling voltage Vb. It can be understood that by acquiring the voltage across the sampling resistor Rs, and then amplifying it through the signal amplification unit 71, the sampling voltage Vb is obtained. The control circuit 50 acquires this sampling voltage Vb and, based on the sampling voltage Vb and the resistance value of the sampling resistor Rs, determines the current flowing through the sampling resistor Rs. This current is the current at the output terminal of the voltage conversion device 100. The output power of the voltage conversion device 100's output terminal Vout is then obtained by multiplying the current flowing through the sampling resistor Rs by the sampling voltage Vb.

[0101] It is understood that in some other embodiments, the voltage conversion device 100 may not include the detection circuit 70, that is, the detection circuit 70 may be omitted and the output power may be obtained through other means. For example, the voltage conversion device 100 can obtain the output power based on the switching frequency of the switching transistors in the three switching bridge arms. In one possible implementation, there is a certain correspondence between the switching frequency of the switching transistors in the three switching bridge arms and the output power of the voltage conversion device 100. The control circuit 50 can obtain the switching frequency of the switching transistors (Q1 to Q6), and the output power of the voltage conversion device 100 can be obtained through the switching frequency and the correspondence between the switching frequency and the output power.

[0102] It is understandable that the output power of the voltage converter 100 is related to the load connected to its output terminal. When the load connected to the output terminal Vout is heavy, the output power of the voltage converter 100 is higher, and correspondingly, more components within the voltage converter 100 need to operate to achieve the higher output power. When the load connected to the output terminal Vout is light, the output power of the voltage converter 100 is lower, and correspondingly, some components within the voltage converter 100 can be deactivated to achieve the required output power for the load. This allows for better energy conservation.

[0103] It is understandable that reducing the losses of the voltage conversion device 100 in single-phase mode can help improve the efficiency of the voltage conversion device 100 across the entire load range.

[0104] Example 2: In Embodiment 2, the voltage conversion device includes a three-phase half-bridge circuit, a three-phase resonant circuit, a three-phase transformer, a control circuit, and a switching unit. The three-phase half-bridge circuit includes three switching arms. One end of each of the three primary windings of the three-phase transformer is used to receive the voltage output from the three-phase half-bridge circuit through the three-phase resonant circuit, and the other ends of the three primary windings of the three-phase transformer are connected to form a tap. One end of the switching unit is connected to the tap, and the other end of the switching unit is connected to the midpoint of any one of the three switching arms. In response to the output power of the voltage conversion device being lower than a preset power value, the control circuit controls one end of the switching unit and the other end of the switching unit to conduct.

[0105] Please see Figure 7 The image shows a voltage conversion device 100a provided in Embodiment 2. The voltage conversion device 100 includes a three-phase half-bridge circuit 10, a three-phase resonant circuit 20, a three-phase transformer 30, a three-phase rectifier bridge circuit 40, a control circuit 50, a switching unit 60a, and a detection circuit 70.

[0106] The structure of voltage conversion device 100a is basically the same as that of voltage conversion device 100, the only difference being that the location of switching unit 60a in embodiment two is different from that of switching unit 60 in embodiment one. The description of the structural parts in embodiment two that are the same as in embodiment one will not be repeated here.

[0107] In this second embodiment, one end of the switching unit 60a is connected to the tap P0, and the other end of the switching unit 60a is connected to the midpoint P2 of the second switch bridge arm.

[0108] In Embodiment 2, the voltage conversion device 100a includes three operating modes: three-phase mode, two-phase mode, and single-phase mode. In response to the output power of the voltage conversion device 100a being within a first preset range, the voltage conversion device 100a operates in three-phase mode, and the control circuit 50 controls the three switching arms to operate normally. In response to the output power of the voltage conversion device 100a being within a second preset range, the voltage conversion device 100a operates in two-phase mode, and the control circuit 50 controls any two of the three switching arms to operate normally. In response to the output power of the voltage conversion device 100a being within a third preset range, the voltage conversion device 100a operates in single-phase mode, and the control circuit 50 controls any two of the three switching arms to operate normally, while keeping the switch in the remaining arm off, and connecting the first terminal of the switching unit 60a to the second terminal of the switching unit 60a. The switching arm connected to the second terminal of the switching unit 60a is one of the two normally operating switching arms. The maximum value of the second preset range is less than the minimum value of the first preset range; the maximum value of the third preset range is less than the minimum value of the second preset range, and the minimum value of the second preset range is the preset power value.

[0109] It is understood that, compared with Embodiment 1, the voltage conversion device 100a still includes three operating modes. The difference is that, in single-phase mode, in Embodiment 1, the voltage conversion device 100 controls any one of the three switch bridge arms to work normally, while in Embodiment 2, the voltage conversion device 100a controls any two of the three switch bridge arms to work normally.

[0110] Obviously, the equivalent circuits of voltage converter 100a in three-phase and two-phase modes are the same as those of voltage converter 100 in three-phase and two-phase modes. Therefore, for the circuit structure and related descriptions of voltage converter 100a in three-phase and two-phase modes, please refer to the corresponding parts in Embodiment 1. Figure 5 and Figure 6 This will not be elaborated upon here.

[0111] In single-phase mode, the control circuit 50 controls the first end of the switching unit 60a and the second end of the switching unit to conduct, and the control circuit 50 controls any two of the three switching bridge arms to work normally.

[0112] Please refer to the following: Figure 8 As shown Figure 7 A schematic diagram of the equivalent circuit of the medium voltage conversion device 100a in single-phase mode.

[0113] In response to the output power of the voltage converter 100a being lower than a preset power value, i.e., the output power being within a third preset range, the control circuit 50 controls the voltage converter 100a to switch to single-phase mode. Specifically, the control circuit 50 controls one end of the switching unit 60a and the other end of the switching unit 60a to be turned on, controls the first and second switching arms of the three switching arms to operate normally, and controls the switching transistors (Q5, Q6) in the third switching arm to remain off.

[0114] It should be understood that normal operation of the first and second switch arms means that the switching transistors Q1 and Q2 in the first switch arm are periodically switched on alternately, and the switching transistors Q3 and Q4 in the second switch arm are periodically switched on alternately.

[0115] Because tap P0 is connected to the midpoint P2 of the second switch arm, the resonant capacitor Cr2 and resonant inductor Lr2 are short-circuited. Thus, the voltage conversion device 100 forms a full-bridge LLC topology. No current flows through the resonant capacitor Cr2 and resonant inductor Lr2 in the second resonant unit, the primary winding Lm2 of transformer T2, rectifier S3 and rectifier S4 in the second rectifier unit, the resonant capacitor Cr2 and resonant inductor Lr2 in the third resonant unit, the primary winding Lm2 of transformer T2, and rectifier S5 and rectifier S6 in the third rectifier unit.

[0116] It is understandable that by setting the switching unit 60a to connect the taps formed by the three primary windings and the midpoint of any one of the three switching bridge arms, the voltage conversion device 100a can operate in single-phase mode with a full-bridge LLC structure. In this way, the voltage conversion device 100a can reduce the use of resonant capacitors, resonant inductors, and transformers, thereby reducing energy loss and improving power conversion efficiency. For example, compared to the voltage conversion device 200 in single-phase mode, the voltage conversion device 100a reduces the use of resonant capacitor Cr2, resonant inductor Lr2, transformer T2, rectifier S3, and rectifier S4.

[0117] It is understandable that the output power of the voltage converter 100a is related to the load connected to its output terminal. When the load connected to the output terminal Vout is heavy, the output power of the voltage converter 100a is higher, and correspondingly, more components within the voltage converter 100a need to operate to achieve the higher output power. When the load connected to the output terminal Vout is light, the output power of the voltage converter 100a is lower, and correspondingly, some components within the voltage converter 100a can be deactivated to achieve the required output power for the load. This allows for better energy conservation.

[0118] It is understandable that reducing the losses of the voltage converter 100a in single-phase mode can help improve the efficiency of the voltage converter 100a across the entire load range.

[0119] Example 3: In Embodiment 3, the voltage conversion device includes a three-phase half-bridge circuit, a three-phase resonant circuit, a three-phase transformer, a control circuit, and a switching unit. The three-phase half-bridge circuit includes three switching arms. One end of each of the three primary windings of the three-phase transformer is used to receive the voltage output from the three-phase half-bridge circuit through the three-phase resonant circuit, and the other ends of the three primary windings of the three-phase transformer are connected to form a tap. One end of the switching unit is connected to the tap, and the other end of the switching unit is connected to ground. In response to the input power of the voltage conversion device being lower than a preset power value, the control circuit controls one end of the switching unit and the other end of the switching unit to conduct.

[0120] Please see Figure 9 The image shows a voltage conversion device 100b provided in Embodiment 3. The voltage conversion device 100b includes a three-phase half-bridge circuit 10, a three-phase resonant circuit 20, a three-phase transformer 30, a three-phase rectifier bridge circuit 40, a control circuit 50a, a switching unit 60, and a detection circuit 70a.

[0121] The structure of voltage conversion device 100b is basically the same as that of voltage conversion device 100 in Embodiment 1. The only difference is that the function of control circuit 50a is different in Embodiment 3, and the location of detection circuit 70a is different from that of detection circuit 70 in Embodiment 1. The description of the parts of Embodiment 3 that are the same as those in Embodiment 1 will not be repeated here.

[0122] In this third embodiment, in response to the input power of the voltage converter 100b being within a first preset range, the voltage converter 100b operates in three-phase mode, and the control circuit 50a controls the three switching arms to operate normally. In response to the input power of the voltage converter 100b being within a second preset range, the voltage converter 100b operates in two-phase mode, and the control circuit 50a controls any two of the three switching arms to operate normally. In response to the input power of the voltage converter 100b being within a third preset range, the voltage converter 100b operates in single-phase mode, and the control circuit 50a controls any one of the three switching arms to operate normally. The maximum value of the second preset range is less than the minimum value of the first preset range; the maximum value of the third preset range is less than the minimum value of the second preset range, and the minimum value of the second preset range is the preset power value.

[0123] In this third embodiment, the control circuit 50a responds to the input power of the voltage conversion device 100b being lower than the preset power value, and controls one end of the switching unit 60 and the other end of the switching unit 60 to be turned on.

[0124] In this third embodiment, the detection circuit 70a includes a sampling resistor Rs and a signal amplification unit 71. The sampling resistor Rs is positioned between the input voltage source Vin of the voltage conversion device 100b and the three-phase half-bridge circuit 10. The signal amplification unit 71 is used to acquire and amplify the voltage across the sampling resistor Rs to obtain a sampling voltage Vb. The control circuit 50a is used to obtain the input current based on the sampling voltage Vb and the resistance value of the sampling resistor Rs, and to obtain the input power based on the input current and the sampling voltage Vb.

[0125] It is understandable that the input power of the voltage converter 100b is related to the load connected to its output terminal. When the load connected to the output terminal Vout is heavy, the input power of the voltage converter 100b is higher, and correspondingly, more components within the voltage converter 100b need to operate to achieve the higher input power. When the load connected to the output terminal Vout is light, the input power of the voltage converter 100b is lower, and correspondingly, some components within the voltage converter 100b can be deactivated to achieve the output power required by the load. This allows for better energy conservation.

[0126] Example 4: In Embodiment 4, the voltage conversion device includes a three-phase half-bridge circuit, a three-phase resonant circuit, a three-phase transformer, a control circuit, and a switching unit. The three-phase half-bridge circuit includes three switching arms. One end of each of the three primary windings of the three-phase transformer is used to receive the voltage output from the three-phase half-bridge circuit through the three-phase resonant circuit. The other end of each of the three primary windings of the three-phase transformer is connected to the midpoint of any one of the three switching arms. One end of the switching unit is connected to a tap, and the other end is connected to ground. In response to the input power of the voltage conversion device being lower than a preset power value, the control circuit controls one end of the switching unit and the other end of the switching unit to conduct.

[0127] Please see Figure 10 The image shows a voltage conversion device 100c provided in Embodiment 4. The voltage conversion device 100c includes a three-phase half-bridge circuit 10, a three-phase resonant circuit 20, a three-phase transformer 30, a three-phase rectifier bridge circuit 40, a control circuit 50a, a switching unit 60a, and a detection circuit 70a.

[0128] Compared with Embodiment 2, the only difference between the structure of voltage conversion device 100c and the structure of voltage conversion device 100a in Embodiment 2 is that the function of control circuit 50a is different in Embodiment 4, and the location of detection circuit 70a is different from that of detection circuit 70 in Embodiment 2. The descriptions of the structural parts in Embodiment 4 that are the same as those in Embodiment 2 will not be repeated here.

[0129] In this fourth embodiment, in response to the output power of the voltage conversion device 100c being within a first preset range, the voltage conversion device 100c operates in three-phase mode, and the control circuit 50a controls the three switching arms to operate normally. In response to the output power of the voltage conversion device 100c being within a second preset range, the voltage conversion device 100c operates in two-phase mode, and the control circuit 50a controls any two of the three switching arms to operate normally. In response to the output power of the voltage conversion device 100c being within a third preset range, the voltage conversion device 100c operates in single-phase mode, and the control circuit 50a controls any two of the three switching arms to operate normally, while keeping the switch in the other of the three switching arms off, and controlling the first terminal of the switching unit 60a to be connected to the second terminal of the switching unit 60a. The switching arm connected to the second terminal of the switching unit 60a is one of the two normally operating switching arms. The maximum value of the second preset range is less than the minimum value of the first preset range; the maximum value of the third preset range is less than the minimum value of the second preset range, and the minimum value of the second preset range is the preset power value.

[0130] In this fourth embodiment, the control circuit 50a controls one end of the switching unit 60a and the other end of the switching unit 60a to conduct in response to the input power of the voltage conversion device 100c being lower than the preset power value.

[0131] Compared with Embodiment 3, the only difference between the structure of voltage conversion device 100c and the structure of voltage conversion device 100b in Embodiment 3 is that the location of switching unit 60a in Embodiment 4 is different from that of switching unit 60 in Embodiment 3. The descriptions of the structural parts in Embodiment 4 that are identical to those in Embodiment 3 will not be repeated here.

[0132] In this fourth embodiment, one end of the switching unit 60a is connected to the tap P0, and the other end of the switching unit 60a is connected to the midpoint P2 of the second switch bridge arm.

[0133] It is understood that the beneficial effects of Example 3 are described in the corresponding parts of Example 2 and Example 3, and will not be repeated here.

[0134] Example 5: Please see Figure 11 This application also provides a control method for a voltage conversion device, applicable to the voltage conversion device 100 / 100a described above. For example... Figure 11 As shown, the control method for the voltage conversion device includes: Step S101: Obtain the output power of the voltage conversion device 100 / 100a.

[0135] It is understandable that this step is executed by control circuit 50. For example... Figure 4 , Figure 7 As shown, the control circuit 50 can obtain the output power of the voltage conversion device 100 / 100a, for example, through the detection circuit 70. Its specific working principle can be found in [reference needed]. Figure 4 , Figure 7 The details and related descriptions will not be repeated here.

[0136] In step S102, in response to the output power being lower than the preset power value, the first terminal and the second terminal of the switching unit 60 / 60a are turned on.

[0137] It is understood that this step is performed by the control circuit 50. When the output power is lower than the preset power value, the control circuit 50 controls the first and second terminals of the switching unit 60 / 60a to conduct, thereby causing the voltage conversion device 100 / 100a to switch to single-phase mode. For a detailed description, please refer to [link to relevant documentation]. Figure 4 , Figure 7 The details and related descriptions will not be repeated here.

[0138] It is understandable that by setting the switching unit 60 / 60a to connect the tap formed by the three primary windings to ground, or to connect the tap formed by the three primary windings to the midpoint of any one of the three switching bridge arms, the voltage converter 100 / 100a can operate in single-phase mode with either a half-bridge LLC structure or a full-bridge LLC structure. In this way, the voltage converter 100 can reduce the use of resonant capacitors, resonant inductors, and transformers, thereby reducing energy loss in single-phase mode and improving power conversion efficiency. This facilitates efficiency improvement of the voltage converter 100 / 100a across the entire load range.

[0139] It is understandable that the output power of the voltage converter 100 is related to the load connected to its output terminal. When the load connected to the output terminal Vout is heavy, the output power of the voltage converter 100 is higher, and correspondingly, more components within the voltage converter 100 need to operate to achieve the higher output power. When the load connected to the output terminal Vout is light, the output power of the voltage converter 100 is lower, and correspondingly, some components within the voltage converter 100 can be deactivated to achieve the required output power for the load. This allows for better energy conservation.

[0140] Example 6: Please see Figure 12 The diagram shows a schematic of the power supply device 300 provided in Embodiment 4 of this application. The power supply device 300 can supply power to the load 400. The load 400 may include, but is not limited to, a baseband unit (BBU) in a base station, a personal computer, a mobile phone, a computer, a television screen, etc.

[0141] In one possible implementation, the power supply device 300 is an AC-DC (alternating current to direct current) conversion system. The power supply device 300 includes an AC-DC conversion unit 310 and a DC-DC voltage conversion device 320. The AC-DC conversion unit 310 converts AC voltage to DC voltage and outputs it to the voltage conversion device 320. It is understood that the voltage conversion device 320 in this embodiment can be any one of the voltage conversion devices 100 / 100a / 100b / 100c in the above embodiments, and will not be described further here.

[0142] In another possible implementation, the power supply device 300 can also be a DC-DC conversion system. Correspondingly, the power supply device 300 includes a DC-DC voltage converter 320 for converting a DC input voltage into a DC output voltage.

[0143] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A voltage conversion device for converting a DC input voltage into a DC output voltage, characterized in that, The voltage conversion device includes a three-phase half-bridge circuit, a three-phase resonant circuit, a three-phase transformer, a control circuit, and a switching unit; The three-phase half-bridge circuit includes three switching bridge arms; One end of each of the three primary windings in the three-phase transformer is used to receive the voltage output by the three-phase half-bridge circuit through the three-phase resonant circuit, and the other ends of the three primary windings in the three-phase transformer are connected to form a tap. The voltage conversion device can operate in single-phase mode, and one end of the switching unit is connected to the tap. The other end of the switching unit is connected to ground. In response to the output power or input power of the voltage conversion device being lower than a preset power value, the control circuit controls one of the three switching arms to operate normally, controls the switching transistors in the other two switching arms to turn off, and controls one end of the switching unit to be connected to the other end of the switching unit; or... The other end of the switching unit is connected to the midpoint of any one of the three switching arms. In response to the output power or input power of the voltage conversion device being lower than the preset power value, the control circuit controls two of the three switching arms to operate normally, controls the switch in the other of the three switching arms to turn off, and controls one end of the switching unit and the other end of the switching unit to be connected, wherein the switching arm connected to the other end of the switching unit is one of the two normally operating switching arms.

2. The voltage conversion device as described in claim 1, characterized in that, The voltage conversion device can operate in two-phase mode and three-phase mode; In response to the output power or input power of the voltage conversion device being within a first preset range, the voltage conversion device operates in the three-phase mode, and the control circuit controls the three switching bridge arms to operate normally, and controls one end of the switching unit and the other end of the switching unit to be non-conductive; In response to the output power or input power of the voltage conversion device being within a second preset range, the voltage conversion device operates in the two-phase mode, and the control circuit controls any two of the three switching bridge arms to operate normally, and controls one end of the switching unit and the other end of the switching unit to be non-conductive; In response to the output power or input power of the voltage conversion device being within a third preset range, the voltage conversion device operates in the single-phase mode; Wherein, the maximum value of the second preset range is less than the minimum value of the first preset range; The maximum value of the third preset range is less than the minimum value of the second preset range, and the minimum value of the second preset range is the preset power value.

3. The voltage conversion device as described in claim 1 or 2, characterized in that, The switching unit is a switching transistor. The first end of the switching unit is connected to the tap, the second end of the switching unit is connected to ground or the midpoint of any one of the three switching arms, and the third end of the switching unit is connected to the control circuit.

4. The voltage conversion device as described in claim 1, characterized in that, In response to the output power of the voltage conversion device being lower than a first preset power value, the control circuit controls one end of the switching unit and the other end of the switching unit to be turned on.

5. The voltage conversion device as described in claim 4, characterized in that, The voltage conversion device includes a detection circuit, which includes a sampling resistor and a signal amplification unit. The sampling resistor is disposed between the output terminal of the voltage conversion device and the rectifier circuit of the voltage conversion device. The signal amplification unit is used to acquire and amplify the voltage across the sampling resistor and obtain a sampled voltage. The control circuit is used to obtain the output current based on the sampling voltage and the resistance value of the sampling resistor, and to obtain the output power based on the output current and the sampling voltage.

6. The voltage conversion device as described in claim 1, characterized in that, The control circuit is used to obtain the switching frequency of the switching transistors in the three switching bridge arms, and to obtain the output power according to the switching frequency and the correspondence between the switching frequency and the output power.

7. The voltage conversion device as described in claim 1, characterized in that, In response to the input power of the voltage conversion device being lower than a second preset power value, the control circuit controls one end of the switching unit and the other end of the switching unit to be turned on.

8. The voltage conversion device as described in claim 6, characterized in that, The voltage conversion device includes a detection circuit, which includes a sampling resistor and a signal amplification unit. The sampling resistor is disposed between the input voltage source of the voltage conversion device and the three-phase half-bridge circuit. The signal amplification unit is used to acquire and amplify the voltage across the sampling resistor and obtain the sampled voltage. The control circuit is used to obtain the input current based on the sampling voltage and the resistance value of the sampling resistor, and to obtain the input power based on the input current and the sampling voltage.

9. A control method for a voltage conversion device, the voltage conversion device being used to convert a DC input voltage into a DC output voltage, characterized in that, The voltage conversion device includes a three-phase half-bridge circuit, a three-phase resonant circuit, a three-phase transformer, a control circuit, and a switching unit; the three-phase half-bridge circuit includes three switching arms; one end of each of the three primary windings of the three-phase transformer is used to receive the voltage output by the three-phase half-bridge circuit through the three-phase resonant circuit, and the other ends of the three primary windings of the three-phase transformer are connected to form a tap; the voltage conversion device can operate in single-phase mode; one end of the switching unit is connected to the tap, and the other end of the switching unit is connected to ground or to the midpoint of any one of the three switching arms; the method includes: Obtain the output power or input power of the voltage conversion device; and In response to the output power or the input power being lower than a preset power value, control one of the three switch arms to operate normally, control the switching transistors in the other two of the three switch arms to turn off, and control one end of the switching unit to be connected to the other end of the switching unit. Alternatively, in response to the output power or the input power being lower than a preset power value, two of the three switch arms are controlled to operate normally, the switch in the other of the three switch arms is controlled to turn off, and one end of the switching unit and the other end of the switching unit are controlled to be connected, wherein the switch arm connected to the other end of the switching unit is one of the two normally operating switch arms.

10. The method as described in claim 9, characterized in that, The method includes: In response to the output power or input power of the voltage conversion device being within a first preset range, the three switching bridge arms are controlled to operate normally, and one end of the switching unit and the other end of the switching unit are controlled to be de-conductive; In response to the output power or input power of the voltage conversion device being within a second preset range, control any two of the three switching bridge arms to operate normally, and control one end of the switching unit and the other end of the switching unit to be de-conductive; In response to the output power or input power of the voltage conversion device being within a third preset range, control any one of the three switching bridge arms to operate normally and control one end of the switching unit and the other end of the switching unit to be connected, or control any two of the three switching bridge arms to operate normally and control one end of the switching unit and the other end of the switching unit to be connected; Wherein, the maximum value of the second preset range is less than the minimum value of the first preset range; the maximum value of the third preset range is less than the minimum value of the second preset range, and the minimum value of the second preset range is the preset power value.

11. The method as described in claim 9 or 10, wherein the first end of the switching unit is connected to the tap, the second end of the switching unit is connected to ground, and the third end of the switching unit is connected to the control circuit, characterized in that, The method includes: In response to the output power or input power of the voltage conversion device being lower than the preset power value, one of the three switching bridge arms is controlled to operate normally, the switching transistors in the other two of the three switching bridge arms are controlled to turn off, and the first terminal of the switching unit is controlled to be connected to the second terminal of the switching unit.

12. The method as described in claim 9 or 10, wherein the first end of the switching unit is connected to the tap, the second end of the switching unit is connected to the midpoint of any one of the three switch arms, and the third end of the switching unit is connected to the control circuit, characterized in that, The method includes: In response to the output power or input power of the voltage conversion device being lower than the preset power value, the system controls two of the three switching bridge arms to operate normally, controls the switch tube in the other of the three switching bridge arms to turn off, and controls the first end of the switching unit to be connected to the second end of the switching unit, wherein the switching bridge arm connected to the second end of the switching unit is one of the two normally operating switching bridge arms.

13. A power supply device, characterized in that, The power supply equipment includes: An AC-DC voltage conversion unit is used to convert AC voltage into DC input voltage; and A voltage conversion device is used to receive the DC input voltage output by the AC-DC voltage conversion unit, and output a DC output voltage after DC voltage conversion; The voltage conversion device includes a three-phase half-bridge circuit, a three-phase resonant circuit, a three-phase transformer, a control circuit, and a switching unit. The three-phase half-bridge circuit includes three switching bridge arms; One end of each of the three primary windings in the three-phase transformer is used to receive the voltage output by the three-phase half-bridge circuit through the three-phase resonant circuit, and the other ends of the three primary windings in the three-phase transformer are connected to form a tap. The voltage conversion device can operate in single-phase mode, and one end of the switching unit is connected to the tap. The other end of the switching unit is connected to ground. In response to the output power or input power of the voltage conversion device being lower than a preset power value, the control circuit controls one of the three switching arms to operate normally, controls the switching transistors in the other two switching arms to turn off, and controls one end of the switching unit to be connected to the other end of the switching unit; or... The other end of the switching unit is connected to the midpoint of any one of the three switching arms; in response to the output power or input power of the voltage conversion device being lower than the preset power value, the control circuit controls two of the three switching arms to operate normally, controls the switch in the other of the three switching arms to turn off, and controls one end of the switching unit and the other end of the switching unit to be connected, wherein the switching arm connected to the other end of the switching unit is one of the two normally operating switching arms.

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