A method for voltage equalization control of a resonant converter circuit

Abstract

The application discloses a voltage equalization control method, a control device and a switching power supply. The voltage equalization control method comprises the following steps: obtaining a voltage difference between two ends of a first voltage division capacitor and a second voltage division capacitor; determining whether the voltage difference exceeds a set range; if yes, controlling the driving duty cycle of a first switch tube, a second switch tube, a third switch tube and a fourth switch tube, so that a capacitor with a larger voltage between two ends of the first voltage division capacitor and the second voltage division capacitor is discharged, and the other capacitor is charged, until the voltage difference returns to the set range; wherein, when the driving duty cycle of the first switch tube, the second switch tube, the third switch tube and the fourth switch tube is controlled, the driving of the second switch tube and the driving of the first switch tube are always complementary, and the driving of the fourth switch tube and the driving of the third switch tube are always complementary. The application requires less detection signals, does not need to distinguish the working mode of a transformer, has a simple control method and good robustness.

Description

Technical Field

[0001] This invention relates to the field of power supply technology, and in particular to a voltage equalization control method, control device, and switching power supply. Background Technology

[0002] Currently, commonly used resonant converters have advantages such as low voltage stress on the main power transistors and the ability of the switching transistors to achieve ZVS, making them suitable for high-voltage input power conversion applications, such as photovoltaic power supplies and three-phase power supplies. However, due to differences in the parameters of the drive circuit and the main circuit components, there is a risk of uneven voltage distribution in the voltage divider capacitors, which can easily affect the safe operation of the converter.

[0003] To achieve voltage equalization of the voltage divider capacitors and improve the reliability of the converter, Chinese Patent Application No. 202011051403.0 discloses a voltage equalization control method for a half-bridge three-level LLC converter circuit. This patent's voltage equalization control method includes six steps:

[0004] ① Set the operating mode of the half-bridge three-level LLC converter circuit: frequency conversion mode or duty cycle conversion mode; ②Detect the duty cycle of each switch in the half-bridge three-level LLC converter circuit under the set working mode; ③ Detect the capacitor voltage of each voltage divider capacitor in the half-bridge three-level LLC converter circuit under the set working mode; ④ Calculate the voltage difference between the voltage divider capacitors based on the capacitor voltage; ⑤ Calculate the early turn-off time of the switching transistor based on the voltage difference; ⑥ Control the switching transistor to turn off early based on the duty cycle, the capacitor voltage, and the early turn-off time, so as to increase or decrease the charging or discharging time of the voltage divider capacitor.

[0005] The aforementioned early shutdown time control will cause the switching transistor drives to be unable to complement each other.

[0006] The inventors of this application, through in-depth research, discovered that the control scheme provided by this patent has the following shortcomings: (1) By controlling the early turn-off of the switching transistor to achieve voltage equalization, the switching transistor drives are not complementary, the switching transistor will freewheel through the body diode, resulting in high losses. Furthermore, if the early turn-off time is too long, the switching transistor cannot achieve soft switching, resulting in high losses and poor EMI performance. (2) It is necessary to distinguish the working mode and determine the turn-off time based on the detected voltage difference. The control has many degrees of freedom and the system has poor robustness. Summary of the Invention

[0007] Therefore, the technical problem to be solved by the present invention is to provide a voltage equalization control method, control device and switching power supply, which to a certain extent solves the shortcomings of the above-mentioned prior art.

[0008] As a first aspect of the present invention, the technical solution of the provided pressure equalization control method is as follows: A voltage equalization control method is applied to a resonant converter. The primary circuit of the resonant converter includes a voltage divider circuit, a three-level switching network, and a resonant cavity network. The voltage divider circuit includes a first voltage divider capacitor and a second voltage divider capacitor. The three-level switching network includes a first switch, a second switch, a third switch, and a fourth switch. One end of the first voltage divider capacitor and one end of the first switch are connected together as the positive input terminal of the resonant converter. The other end of the first switch is connected to one end of the second switch and the first input terminal of the resonant cavity network. The other end of the first voltage divider capacitor is connected to one end of the second voltage divider capacitor and the other end of the second switch. The third switch is connected to one end of the first switch, and the other end of the third switch is connected to one end of the fourth switch and the second input terminal of the resonant cavity network. The other end of the second voltage divider capacitor and the other end of the fourth switch are connected together as the negative input terminal of the resonant converter. When the difference between the voltage across the first voltage divider capacitor and the voltage across the second voltage divider capacitor is within a set range, the driving of the second switch and the driving of the first switch are complementary. The driving of the third switch is phase-shifted by 180° relative to the driving of the first switch. The driving of the fourth switch and the driving of the third switch are complementary. The voltage equalization control method includes: Obtain the voltage difference across the first voltage divider capacitor and the second voltage divider capacitor; Determine whether the voltage difference exceeds the set range. If it does, control the duty cycle of the first switch, the second switch, the third switch, and the fourth switch so that the capacitor with the larger voltage at both ends of the first voltage divider capacitor and the second voltage divider capacitor discharges while the other capacitor charges, until the voltage difference returns to the set range. Specifically, when controlling the duty cycle of the first, second, third, and fourth switching transistors, the driving of the second and first switching transistors is always complementary, and the driving of the fourth and third switching transistors is also complementary.

[0009] Furthermore, when the voltage across the first voltage divider capacitor is less than the voltage across the second voltage divider capacitor, if the first switch and the third switch are the main control switches, the duty cycle of the first switch is reduced and / or the duty cycle of the third switch is increased, causing the second voltage divider capacitor to discharge and the first voltage divider capacitor to charge.

[0010] Furthermore, when the voltage across the first voltage divider capacitor is less than the voltage across the second voltage divider capacitor, if the second switch and the fourth switch are the main control switches, the duty cycle of the second switch is reduced and / or the duty cycle of the fourth switch is increased, causing the second voltage divider capacitor to discharge and the first voltage divider capacitor to charge.

[0011] Furthermore, when the voltage across the first voltage divider capacitor is greater than the voltage across the second voltage divider capacitor, if the first switch and the third switch are the main control switches, the duty cycle of the third switch is reduced and / or the duty cycle of the first switch is increased, so that the second voltage divider capacitor is charged and the first voltage divider capacitor is discharged.

[0012] Furthermore, when the voltage across the first voltage divider capacitor is greater than the voltage across the second voltage divider capacitor, if the second switch and the fourth switch are the main control switches, the duty cycle of the fourth switch is reduced and / or the duty cycle of the second switch is increased, so that the second voltage divider capacitor is charged and the first voltage divider capacitor is discharged.

[0013] Furthermore, the duty cycle of the first, second, third, and fourth switching transistors is controlled by directly assigning a certain value to the switching transistor whose duty cycle needs to be adjusted.

[0014] Furthermore, the duty cycle of the first, second, third, and fourth switching transistors is controlled by slowly adjusting the duty cycle of the transistors that require adjustment to a certain value.

[0015] Preferably, the voltage difference between the first voltage divider capacitor and the second voltage divider capacitor is obtained by detecting the voltage across each voltage divider capacitor, or by detecting the input voltage and the voltage of any voltage divider capacitor.

[0016] As a second aspect of the present invention, the technical solution of the provided pressure equalization control device is as follows: A voltage equalization control device is applied to a resonant converter. The primary circuit of the resonant converter includes a voltage divider circuit, a three-level switching network, and a resonant cavity network. The voltage divider circuit includes a first voltage divider capacitor and a second voltage divider capacitor. The three-level switching network includes a first switch transistor, a second switch transistor, a third switch transistor, and a fourth switch transistor. One end of the first voltage divider capacitor and one end of the first switch transistor are connected together as the positive input terminal of the resonant converter. The other end of the first switch transistor is connected to one end of the second switch transistor and the first input terminal of the resonant cavity network. The other end of the first voltage divider capacitor is connected to one end of the second voltage divider capacitor and the other end of the second switch transistor. The third switch is connected to one end of the first voltage divider capacitor, and the other end of the third switch is connected to one end of the fourth switch and the second input terminal of the resonant cavity network. The other end of the second voltage divider capacitor and the other end of the fourth switch are connected together as the negative input terminal of the resonant converter. When the difference between the voltage across the first voltage divider capacitor and the voltage across the second voltage divider capacitor is within a set range, the driving of the second switch and the driving of the first switch are complementary. The driving of the third switch is phase-shifted by 180° relative to the driving of the first switch. The driving of the fourth switch and the driving of the third switch are complementary. The voltage equalization control device includes: The acquisition module is used to acquire the voltage difference between the first voltage divider capacitor and the second voltage divider capacitor; The judgment module is used to determine whether the voltage difference exceeds the set range. If it does, it controls the duty cycle of the first switch, the second switch, the third switch and the fourth switch so that the capacitor with the larger voltage at both ends of the first voltage divider capacitor and the second voltage divider capacitor discharges and the other capacitor charges until the voltage difference returns to the set range. Specifically, when controlling the duty cycle of the first, second, third, and fourth switching transistors, the driving of the second switching transistor and the first switching transistor are always complementary, and the driving of the fourth switching transistor and the third switching transistor are also complementary.

[0017] As a third aspect of the present invention, the technical solution of the provided switching power supply embodiment is as follows: A switching power supply includes a resonant converter. The primary circuit of the resonant converter includes a voltage divider circuit, a three-level switching network, and a resonant cavity network. The voltage divider circuit includes a first voltage divider capacitor and a second voltage divider capacitor. The three-level switching network includes a first switch transistor, a second switch transistor, a third switch transistor, and a fourth switch transistor. One end of the first voltage divider capacitor and one end of the first switch transistor are connected together as the positive input terminal of the resonant converter. The other end of the first switch transistor is connected to one end of the second switch transistor and the first input terminal of the resonant cavity network. The other end of the first voltage divider capacitor is connected to one end of the second voltage divider capacitor, the other end of the second switch transistor, and one end of the third switch transistor. The other end of the third switch is connected to one end of the fourth switch and the second input terminal of the resonant cavity network. The other end of the second voltage divider capacitor and the other end of the fourth switch are connected together as the negative input terminal of the resonant converter. When the difference between the voltage across the first voltage divider capacitor and the voltage across the second voltage divider capacitor is within a set range, the driving of the second switch and the driving of the first switch are complementary. The driving of the third switch is phase-shifted by 180° relative to the driving of the first switch. The driving of the fourth switch and the driving of the third switch are complementary. The switching power supply further includes the voltage equalization control device described in any of the second aspects above.

[0018] The beneficial effects of the embodiments of the present invention are as follows: (1) The embodiment of the present invention achieves voltage equalization of the voltage divider capacitors by adjusting the duty cycle of the corresponding switch drive only by obtaining the voltage difference between the first voltage divider capacitor and the second voltage divider capacitor. It does not need to distinguish the working mode of the converter. Compared with the scheme of the prior art, the voltage equalization control is simpler and more robust. (2) In the embodiments of the present invention, when controlling the size of the duty cycle of the corresponding switching transistors, the driving of the second switching transistor and the driving of the first switching transistor are always complementary, the driving of the fourth switching transistor and the driving of the third switching transistor are complementary, and the driving is still complementary during voltage equalization control. Compared with the scheme of the prior art, it is beneficial to reduce losses, improve efficiency and improve EMI characteristics. Attached Figure Description

[0019] Figure 1 A specific schematic diagram of the resonant converter to which this invention is applicable; Figure 2 This is a flowchart of the pressure equalization control method according to the first embodiment of the present invention; Figure 3 This is a schematic diagram of the first type of pressure equalization control according to the first embodiment of the present invention; Figure 4 This is a schematic diagram of the second type of pressure equalization control according to the first embodiment of the present invention; Figure 5 This is a schematic diagram of the third type of pressure equalization control according to the first embodiment of the present invention; Figure 6 This is a schematic diagram of the fourth type of pressure equalization control according to the first embodiment of the present invention; Figure 7 This is a schematic diagram of the fifth type of pressure equalization control according to the first embodiment of the present invention; Figure 8 This is a schematic diagram of the sixth type of pressure equalization control according to the first embodiment of the present invention; Figure 9 This is a schematic diagram of the seventh type of pressure equalization control according to the first embodiment of the present invention; Figure 10 This is a schematic diagram of the eighth type of pressure equalization control according to the first embodiment of the present invention; Figure 11 This is a schematic diagram of the ninth type of pressure equalization control according to the first embodiment of the present invention; Figure 12 This is a schematic diagram of the tenth type of pressure equalization control according to the first embodiment of the present invention; Figure 13 This is a schematic diagram of the eleventh type of pressure equalization control according to the first embodiment of the present invention; Figure 14 This is a schematic diagram of the twelfth type of pressure equalization control according to the first embodiment of the present invention; Figure 15 This is a schematic diagram of the thirteenth pressure equalization control according to the first embodiment of the present invention; Figure 16 This is a schematic diagram of the fourteenth pressure equalization control according to the first embodiment of the present invention; Figure 17 This is a schematic diagram of the fifteenth type of pressure equalization control according to the first embodiment of the present invention; Figure 18 This is a schematic diagram of the sixteenth type of pressure equalization control according to the first embodiment of the present invention; Figure 19 This is a schematic diagram of the seventeenth type of pressure equalization control according to the first embodiment of the present invention; Figure 20 This is a schematic diagram of the eighteenth type of pressure equalization control according to the first embodiment of the present invention. Detailed Implementation

[0020] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0021] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0022] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be used interchangeably where appropriate for the purposes of describing embodiments of this application herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0023] It should be understood that in the specification, claims, and drawings, when a step is described as continuing into another step, the step may directly continue into that other step or be continued into that other step through a third step; when an element / unit is described as "continuing" into another element / unit, the element / unit may be "directly connected" to that other element / unit or "connected" to that other element / unit through a third element / unit.

[0024] Furthermore, the accompanying drawings are merely illustrative of this disclosure and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions thereof will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0025] Figure 1 This is a schematic diagram of a specific principle of the resonant converter to which this invention applies, such as... Figure 1 As shown, the primary circuit of the resonant converter located on the primary side of transformer 40 includes a voltage divider circuit 10, a three-level switch network 20, and a resonant cavity network 30, while the secondary rectifier circuit 50 and filter capacitor Co are located on the secondary side of transformer 40.

[0026] Specifically, such as Figure 1As shown, the voltage divider circuit 10 includes a first voltage divider capacitor C1 and a second voltage divider capacitor C2 connected in series. One end of the first voltage divider capacitor C1 is connected to the positive terminal of the power supply Vin, and one end of the second voltage divider capacitor C2 is connected to the negative terminal of the power supply Vin. The three-level switching network 20 includes a first switch transistor Q1, a second switch transistor Q2, a third switch transistor Q3, and a fourth switch transistor Q4 connected in series. The drain of the first switch transistor Q1 is connected to the positive terminal of the power supply Vin, and the source of the fourth switch transistor Q4 is connected to the negative terminal of the power supply Vin. The source of the first switch transistor Q1 and the drain of the second switch transistor Q2 are respectively connected to one input terminal of the resonant cavity network 30, that is, one end of the resonant inductor Lr in the resonant cavity network 30 is connected. The source of the third switch transistor Q3 and the drain of the fourth switch transistor Q4 are respectively connected to the other input terminal of the resonant cavity network 30, that is, one end of the resonant capacitor Cr in the resonant cavity network 30 is connected. The source of the second switch transistor Q2 is connected to the drain of the third switch transistor Q3 and is also connected to the other end of the first voltage divider capacitor C1 and the second voltage divider capacitor C2.

[0027] It should be noted that, Figure 1 The circuit located on the secondary side of transformer 40 is merely an example and should not be considered as limiting the scope of protection of this invention. Those skilled in the art can choose the specific design as needed.

[0028] First Embodiment This embodiment provides a pressure equalization control method, which is applied... Figure 1 The three-level LLC resonant converter shown is as follows: when the difference between the voltage across the first voltage divider capacitor and the voltage across the second voltage divider capacitor is within a set range, no voltage equalization control is required. The control strategy is as follows: the driving of the second switch Q2 is complementary to the driving of the first switch Q1, the driving of the third switch Q3 is phase-shifted by 180° relative to the driving of the first switch Q1, and the driving of the fourth switch Q4 is complementary to the driving of the third switch Q3.

[0029] Figure 2 For a flowchart of the pressure equalization control method according to the first embodiment of the present invention, please refer to [link / reference]. Figure 2 The pressure equalization control method in this embodiment includes: S100, obtain the voltage difference between the first voltage divider capacitor and the second voltage divider capacitor; S200, determine whether the voltage difference exceeds the set range. If yes, control the duty cycle of the first switch, the second switch, the third switch and the fourth switch so that the capacitor with the larger voltage at both ends of the first voltage divider capacitor and the second voltage divider capacitor discharges and the other capacitor charges until the voltage difference returns to the set range. Specifically, when controlling the duty cycle of the first, second, third, and fourth switching transistors, the driving of the second and first switching transistors is always complementary, and the driving of the fourth and third switching transistors is also complementary.

[0030] The voltage equalization control method in this embodiment achieves voltage equalization of the voltage-dividing capacitors by adjusting the duty cycle of the corresponding switching transistors based on the voltage difference between the first and second voltage-dividing capacitors. It does not require distinguishing the converter's operating mode, making the voltage equalization control simpler and more robust than the prior art solution. Furthermore, when controlling the duty cycle of the corresponding switching transistors, the driving of the second and first switching transistors is always complementary, as are the driving of the fourth and third switching transistors. The driving is still complementary during voltage equalization control, which is beneficial for reducing transformer losses, improving efficiency, and enhancing EMI characteristics compared to the prior art solution.

[0031] Figure 3 This is a schematic diagram of the first type of pressure equalization control according to the first embodiment of the present invention. Figure 4 This is a schematic diagram of the second voltage equalization control according to the first embodiment of the present invention. In this embodiment, when the capacitor voltage VC1 of the first voltage divider capacitor is less than the capacitor voltage VC2 of the second voltage divider capacitor, but the hysteresis set by the designer is not reached, such as... Figure 3 and Figure 4 As shown, when the voltage equalization control signal EN1 is low, the drive S1 of switch Q1 and the drive S2 of switch Q2 are complementary, the drive S3 of switch Q3 is phase-shifted by 180° relative to the drive S1 of switch Q1, and the drive S4 of switch Q4 and the drive S3 of switch Q3 are complementary, and no voltage equalization adjustment is performed.

[0032] When the voltage across the first voltage divider capacitor VC1 is less than the voltage across the second voltage divider capacitor VC2, and the hysteresis between VC1 and VC2 is greater than the hysteresis set by the designer, if switching transistors Q1 and Q3 are used as the main control switching transistors: Please continue to refer to the diagram. Figure 3 and Figure 4 The equalization control signal EN1 flips from low level to high level, reducing the driving duty cycle of switch Q1. Switches Q2 and Q1 maintain complementary driving, while the driving duty cycles of switches Q3 and Q4 remain unchanged. This allows the second voltage divider capacitor C2 to discharge through the second switch Q2, resonant inductor Lr, transformer T, resonant capacitor Cr, and fourth switch Q4. Conversely, the first voltage divider capacitor C1 is charged through the second switch Q2, resonant inductor Lr, transformer T, resonant capacitor Cr, fourth switch Q4, the negative terminal of power supply Vin, and the positive terminal of power supply Vin. Or such as Figure 5 and Figure 6As shown, the duty cycle of switch Q3 is increased, switch Q4 is complementary to switch Q3, and the duty cycles of switch Q1 and switch Q2 are kept constant. This allows the second voltage divider capacitor C2 to be discharged through the third switch Q3, resonant capacitor Cr, transformer T, resonant inductor Lr, first switch Q1, positive terminal of power supply Vin, and negative terminal of power supply Vin. This allows the first voltage divider capacitor C1 to be charged through the third switch Q3, resonant capacitor Cr, transformer T, resonant inductor Lr, and first switch Q1. Both of the above methods can bring the voltage difference between the first and second voltage divider capacitors back to the set range. Alternatively, the two methods can be combined, i.e., simultaneously reducing the duty cycle of the switch Q1 and increasing the duty cycle of the switch Q3. The second voltage divider capacitor C2 discharges and the first voltage divider capacitor C1 charges, both of which have two paths, which can speed up the process of bringing the voltage difference between the first and second voltage divider capacitors back to the set range.

[0033] When the voltage across the first voltage divider capacitor VC1 is less than the voltage across the second voltage divider capacitor VC2, and the hysteresis between VC1 and VC2 is greater than the hysteresis set by the designer, if switching transistors Q2 and Q4 are used as the main control switching transistors: like Figure 7 and Figure 8 As shown, the driving duty cycle of switch Q2 is reduced, while switches Q1 and Q2 maintain complementary driving. The driving duty cycles of switches Q3 and Q4 remain unchanged. This allows the second voltage divider capacitor C2 to discharge through the third switch Q3, resonant capacitor Cr, transformer T, resonant inductor Lr, first switch Q1, positive terminal of power supply Vin, and negative terminal of power supply Vin. This allows the first voltage divider capacitor C1 to be charged through the third switch Q3, resonant capacitor Cr, transformer T, resonant inductor Lr, and first switch Q1. Or such as Figure 9 and Figure 10 As shown, the duty cycle of switch Q4 is increased, and the driving of switch Q3 and switch Q4 is complementary. The duty cycles of switch Q1 and switch Q2 are kept constant. This allows the second voltage divider capacitor C2 to be discharged through the second switch Q2, resonant inductor Lr, transformer T, resonant capacitor Cr, and fourth switch Q4. This allows the first voltage divider capacitor C1 to be charged through the second switch Q2, resonant inductor Lr, transformer T, resonant capacitor Cr, fourth switch Q4, negative terminal of power supply Vin, and positive terminal of power supply Vin. Both of the above methods can bring the voltage difference between the first and second voltage divider capacitors back to the set range. The two methods can also be combined, that is, simultaneously reducing the duty cycle of the switch Q2 and increasing the duty cycle of the switch Q4. The second voltage divider capacitor C2 discharges and the first voltage divider capacitor C1 charges, which can speed up the process of bringing the voltage difference between the first and second voltage divider capacitors back to the set range.

[0034] When the voltage equalization control makes the hysteresis between VC1 and VC2 less than the hysteresis set by the designer, the voltage equalization control signal EN1 flips from high level to low level. The driving of switching transistors Q1 and Q2 is complementary. The driving of transistor Q3 is phase-shifted by 180° relative to the driving of transistor Q1. The driving of transistor Q4 is complementary to the driving of transistor Q3. No voltage equalization adjustment is performed.

[0035] The drive duty cycle can be decreased or increased slowly, or a certain value can be given directly, but the maximum adjustable value must be limited.

[0036] The equalization control signal can be processed externally to the controller or by a comparator inside the controller; this invention does not impose any limitations.

[0037] When the voltage across the first voltage divider capacitor VC1 is greater than the voltage across the second voltage divider capacitor VC2, and the hysteresis between VC1 and VC2 is greater than the set hysteresis value, if switching transistors Q1 and Q3 are used as the main control switching transistors: like Figure 11 and Figure 12 As shown, the equalization control signal EN1 flips from low level to high level, reducing the duty cycle of the switch Q3. Switches Q4 and Q3 maintain complementary driving, while the duty cycles of switches Q1 and Q2 remain unchanged. This allows the second voltage divider capacitor C2 to be charged through the fourth switch Q4, resonant capacitor Cr, transformer T, resonant inductor Lr, and second switch Q2. Conversely, the first voltage divider capacitor C1 is discharged through the positive terminal of power supply Vin, the negative terminal of power supply Vin, the fourth switch Q4, resonant capacitor Cr, transformer T, resonant inductor Lr, and second switch Q2. Or such as Figure 13 and Figure 14 As shown, the duty cycle of switch Q1 is increased, and the drive of switch Q2 is complementary to that of switch Q1. The duty cycles of switch Q1 and switch Q2 are kept constant. This allows the second voltage divider capacitor C2 to be charged through the negative terminal of power supply Vin, the positive terminal of power supply Vin, the first switch Q1, the resonant inductor Lr, the transformer T, the resonant capacitor Cr, and the third switch Q3. This allows the first voltage divider capacitor C1 to be discharged through the first switch Q1, the resonant inductor Lr, the transformer T, the resonant capacitor Cr, and the third switch Q3. Both of the above methods can bring the voltage difference between the first and second voltage divider capacitors back to the set range. The two methods can also be combined, that is, simultaneously reducing the duty cycle of the switch Q3 and increasing the duty cycle of the switch Q1. The second voltage divider capacitor C2 is charged and the first voltage divider capacitor C1 is discharged, which can speed up the process of bringing the voltage difference between the first and second voltage divider capacitors back to the set range.

[0038] When the capacitor voltage VC1 of the first voltage divider capacitor is greater than the capacitor voltage VC2 of the second voltage divider capacitor, and the hysteresis between VC1 and VC2 is greater than the set hysteresis value, if switching transistors Q2 and Q4 are used as the main control switching transistors: like Figure 15 and 16 As shown, the duty cycle of switch Q4 is reduced, while switch Q3 and switch Q4 maintain complementary driving. The duty cycles of switch Q1 and switch Q2 remain unchanged. This allows the second voltage divider capacitor C2 to be charged through the negative and positive terminals of power supply Vin, the first switch Q1, the resonant inductor Lr, the transformer T, the resonant capacitor Cr, and the third switch Q3. This allows the first voltage divider capacitor C1 to be discharged through the first switch Q1, the resonant inductor Lr, the transformer T, the resonant capacitor Cr, and the third switch Q3. Or such as Figure 17 and 18 As shown, the duty cycle of switch Q2 is increased, and the driving of switch Q1 and switch Q2 is complementary. The duty cycles of switch Q3 and switch Q4 are kept constant. This allows the second voltage divider capacitor C2 to be charged through the fourth switch Q4, resonant capacitor Cr, transformer T, resonant inductor Lr, and second switch Q2. This allows the first voltage divider capacitor C1 to be discharged through the positive terminal of power supply Vin, the negative terminal of power supply Vin, the fourth switch Q4, resonant capacitor Cr, transformer T, resonant inductor Lr, and second switch Q2. Both of the above methods can bring the voltage difference between the first and second voltage divider capacitors back to the set range. Alternatively, the two methods can be combined, i.e., simultaneously reducing the duty cycle of the switch Q4 and increasing the duty cycle of the switch Q2. This provides two paths for both the charging of the second voltage divider capacitor C2 and the discharging of the first voltage divider capacitor C1, which can speed up the process of bringing the voltage difference between the first and second voltage divider capacitors back to the set range.

[0039] Figure 19 and Figure 20The diagram illustrates a specific control scenario where the charging and discharging capacitors have two paths. It addresses the situation where the voltage across the first voltage divider capacitor (VC1) is less than the voltage across the second voltage divider capacitor (VC2), and the hysteresis between VC1 and VC2 is greater than the designer-defined hysteresis. In this scenario, the voltage equalization control signal EN1 flips from low to high, and the switching transistors Q1 and Q3 act as the main control transistors. Please refer to [link to relevant documentation]. Figure 19 and Figure 20 Simultaneously, the duty cycle of switch Q1 is reduced, and the duty cycle of switch Q3 is increased. Switches Q2 and Q1 drive each other complementaryly, and switches Q4 and Q3 drive each other complementaryly. The second voltage divider capacitor C2 discharges through two paths: one is through the second switch Q2, resonant inductor Lr, transformer T, resonant capacitor Cr, and fourth switch Q4; the other is through the third switch Q3, resonant capacitor Cr, transformer T, resonant inductor Lr, first switch Q1, positive terminal of power supply Vin, and negative terminal of power supply Vin. The first voltage divider capacitor C1 is charged through two paths: one is through the second switch Q2, resonant inductor Lr, transformer T, resonant capacitor Cr, fourth switch Q4, negative terminal of power supply Vin, and positive terminal of power supply Vin; the other is through the third switch Q3, resonant capacitor Cr, transformer T, resonant inductor Lr, and first switch Q1.

[0040] When the capacitor voltage VC1 of the first voltage divider capacitor is less than the capacitor voltage VC2 of the second voltage divider capacitor, and the hysteresis between VC1 and VC2 is less than the hysteresis set by the designer, the control signal EN1 reverses from high level to low level, and voltage equalization adjustment is no longer performed.

[0041] Second Embodiment This embodiment discloses a voltage equalization control device applied to a resonant converter. The primary circuit of the resonant converter includes a voltage divider circuit, a three-level switching network, and a resonant cavity network. The voltage divider circuit includes a first voltage divider capacitor and a second voltage divider capacitor. The three-level switching network includes a first switch, a second switch, a third switch, and a fourth switch. One end of the first voltage divider capacitor and one end of the first switch are connected together as the positive input terminal of the resonant converter. The other end of the first switch is connected to one end of the second switch and the first input terminal of the resonant cavity network. The other end of the first voltage divider capacitor is connected to one end of the second voltage divider capacitor, the other end of the second switch, and one end of the third switch. The other end of the third switch is connected to one end of the fourth switch and the second input terminal of the resonant cavity network. The other end of the second voltage divider capacitor and the other end of the fourth switch are connected together as the negative input terminal of the resonant converter. When the voltage difference between the first and second voltage divider capacitors is within a set range, the driving of the second switch and the driving of the first switch are complementary. The driving of the third switch is phase-shifted by 180° relative to the driving of the first switch. The driving of the fourth switch and the driving of the third switch are complementary. The voltage equalization control device includes: The acquisition module is used to acquire the voltage difference between the first voltage divider capacitor and the second voltage divider capacitor. The judgment module is used to determine whether the voltage difference exceeds the set range. If it does, it controls the duty cycle of the first, second, third, and fourth switching transistors so that the capacitor with the larger voltage at both ends of the first and second voltage divider capacitors discharges and the other capacitor charges until the voltage difference returns to the set range. Specifically, when controlling the duty cycle of the first, second, third, and fourth switching transistors, the driving of the second switching transistor and the first switching transistor are always complementary, and the driving of the fourth switching transistor and the third switching transistor are also complementary.

[0042] The control device in this embodiment uses the same technical means as the control method in the first embodiment, and has the same beneficial effects, so it will not be described in detail. Furthermore, the preferred technical means or further improved means in each step of the control method in the first embodiment can be extended to the corresponding unit in this embodiment, and will not be described in detail in this embodiment.

[0043] Third Embodiment This embodiment provides a switching power supply, including a resonant converter. The primary circuit of the resonant converter includes a voltage divider circuit, a three-level switching network, and a resonant cavity network. The voltage divider circuit includes a first voltage divider capacitor and a second voltage divider capacitor. The three-level switching network includes a first switch transistor, a second switch transistor, a third switch transistor, and a fourth switch transistor. One end of the first voltage divider capacitor and one end of the first switch transistor are connected together as the positive input terminal of the resonant converter. The other end of the first switch transistor is connected to one end of the second switch transistor and the first input terminal of the resonant cavity network. The other end of the first voltage divider capacitor is connected to one end of the second voltage divider capacitor and the other end of the second switch transistor. One end of the third switch is connected to the third switch, and the other end of the third switch is connected to one end of the fourth switch and the second input terminal of the resonant cavity network. The other end of the second voltage divider capacitor and the other end of the fourth switch are connected together as the negative input terminal of the resonant converter. When the difference between the voltage across the first voltage divider capacitor and the voltage across the second voltage divider capacitor is within a set range, the driving of the second switch and the driving of the first switch are complementary. The driving of the third switch is phase-shifted by 180° relative to the driving of the first switch. The driving of the fourth switch and the driving of the third switch are complementary. The switching power supply also includes any one of the voltage equalization control devices in the second embodiment described above.

[0044] Since the switching power supply in this embodiment includes any of the voltage equalization control devices in the second embodiment above, it requires fewer detection signals and has a simpler control method when achieving voltage equalization between the voltage divider capacitors. It can also effectively prevent the resonant converter from entering hard switching, which is beneficial to improving the efficiency of the switching power supply and reducing the EMI interference of the converter.

[0045] The above description of the embodiments is only for the purpose of helping to understand the concept of the present invention and is not intended to limit the present invention. For those skilled in the art, any modifications, equivalent substitutions, improvements, etc., made without departing from the principle of the present invention should be included within the protection scope of the present invention.

Claims

1. A voltage equalization control method applied to a resonant converter, wherein the primary circuit of the resonant converter includes a voltage divider circuit, a three-level switching network, and a resonant cavity network; the voltage divider circuit includes a first voltage divider capacitor and a second voltage divider capacitor; the three-level switching network includes a first switch transistor, a second switch transistor, a third switch transistor, and a fourth switch transistor; one end of the first voltage divider capacitor and one end of the first switch transistor are connected together as the positive input terminal of the resonant converter, the other end of the first switch transistor is connected to one end of the second switch transistor and the first input terminal of the resonant cavity network, and the other end of the first voltage divider capacitor is connected to one end of the second voltage divider capacitor and the first switch transistor. The other end of the second switch and one end of the third switch are connected, the other end of the third switch is connected to one end of the fourth switch and the second input terminal of the resonant cavity network, the other end of the second voltage divider capacitor and the other end of the fourth switch are connected together as the negative input terminal of the resonant converter; when the difference between the voltage across the first voltage divider capacitor and the voltage across the second voltage divider capacitor is within a set range, the driving of the second switch and the driving of the first switch are complementary, the driving of the third switch is phase-shifted by 180° relative to the driving of the first switch, and the driving of the fourth switch and the driving of the third switch are complementary; characterized in that, The pressure equalization control method includes: Obtain the voltage difference across the first voltage divider capacitor and the second voltage divider capacitor; Determine whether the voltage difference exceeds the set range. If it does, control the duty cycle of the first switch, the second switch, the third switch, and the fourth switch so that the capacitor with the larger voltage at both ends of the first voltage divider capacitor and the second voltage divider capacitor discharges while the other capacitor charges, until the voltage difference returns to the set range. Specifically, when controlling the duty cycle of the first, second, third, and fourth switching transistors, the driving of the second and first switching transistors is always complementary and the dead time remains unchanged, as are the driving of the fourth and third switching transistors.

2. The pressure equalization control method according to claim 1, characterized in that: When the voltage across the first voltage divider capacitor is less than the voltage across the second voltage divider capacitor, if the first switch and the third switch are the main control switches, the duty cycle of the first switch is reduced and / or the duty cycle of the third switch is increased, causing the second voltage divider capacitor to discharge and the first voltage divider capacitor to charge.

3. The pressure equalization control method according to claim 1, characterized in that: When the voltage across the first voltage divider capacitor is less than the voltage across the second voltage divider capacitor, if the second switch and the fourth switch are the main control switches, the duty cycle of the second switch is reduced and / or the duty cycle of the fourth switch is increased, causing the second voltage divider capacitor to discharge and the first voltage divider capacitor to charge.

4. The pressure equalization control method according to claim 1, characterized in that: When the voltage across the first voltage divider capacitor is greater than the voltage across the second voltage divider capacitor, if the first switch and the third switch are the main control switches, the duty cycle of the third switch is reduced and / or the duty cycle of the first switch is increased, so that the second voltage divider capacitor is charged and the first voltage divider capacitor is discharged.

5. The pressure equalization control method according to claim 1, characterized in that: When the voltage across the first voltage divider capacitor is greater than the voltage across the second voltage divider capacitor, if the second switch and the fourth switch are the main control switches, the duty cycle of the fourth switch is reduced and / or the duty cycle of the second switch is increased, so that the second voltage divider capacitor is charged and the first voltage divider capacitor is discharged.

6. The pressure equalization control method according to claim 1, characterized in that, The duty cycle of the first, second, third, and fourth switching transistors is controlled by directly assigning a certain value to the switching transistor whose duty cycle needs to be adjusted.

7. The pressure equalization control method according to claim 1, characterized in that, The duty cycle of the first, second, third, and fourth switching transistors is controlled by slowly adjusting it to a certain value for the switching transistor whose duty cycle needs to be adjusted.

8. The pressure equalization control method according to any one of claims 1 to 7, characterized in that, The voltage difference between the first voltage divider capacitor and the second voltage divider capacitor is obtained by detecting the voltage across each voltage divider capacitor, or by detecting the input voltage and the voltage of any voltage divider capacitor.

9. A voltage equalization control device applied to a resonant converter, wherein the primary circuit of the resonant converter includes a voltage divider circuit, a three-level switching network, and a resonant cavity network; the voltage divider circuit includes a first voltage divider capacitor and a second voltage divider capacitor; the three-level switching network includes a first switch transistor, a second switch transistor, a third switch transistor, and a fourth switch transistor; one end of the first voltage divider capacitor and one end of the first switch transistor are connected together as the positive input terminal of the resonant converter, the other end of the first switch transistor is connected to one end of the second switch transistor and the first input terminal of the resonant cavity network, and the other end of the first voltage divider capacitor is connected to one end of the second voltage divider capacitor and the first voltage divider capacitor. The other end of the second switch and one end of the third switch are connected, the other end of the third switch is connected to one end of the fourth switch and the second input terminal of the resonant cavity network, the other end of the second voltage divider capacitor and the other end of the fourth switch are connected together as the negative input terminal of the resonant converter; when the difference between the voltage across the first voltage divider capacitor and the voltage across the second voltage divider capacitor is within a set range, the driving of the second switch and the driving of the first switch are complementary, the driving of the third switch is phase-shifted by 180° relative to the driving of the first switch, and the driving of the fourth switch and the driving of the third switch are complementary; characterized in that, The pressure equalization control device includes: The acquisition module is used to acquire the voltage difference between the first voltage divider capacitor and the second voltage divider capacitor; The judgment module is used to determine whether the voltage difference exceeds the set range. If it does, it controls the duty cycle of the first switch, the second switch, the third switch and the fourth switch so that the capacitor with the larger voltage at both ends of the first voltage divider capacitor and the second voltage divider capacitor discharges and the other capacitor charges until the voltage difference returns to the set range. Specifically, when controlling the duty cycle of the first, second, third, and fourth switching transistors, the driving of the second and first switching transistors is always complementary and the dead time remains unchanged, as are the driving of the fourth and third switching transistors.

10. A switching power supply, comprising a resonant converter, wherein the primary circuit of the resonant converter includes a voltage divider circuit, a three-level switching network, and a resonant cavity network; the voltage divider circuit includes a first voltage divider capacitor and a second voltage divider capacitor; the three-level switching network includes a first switch transistor, a second switch transistor, a third switch transistor, and a fourth switch transistor; one end of the first voltage divider capacitor and one end of the first switch transistor are connected together as the positive input terminal of the resonant converter, the other end of the first switch transistor is connected to one end of the second switch transistor and a first input terminal of the resonant cavity network, and the other end of the first voltage divider capacitor is connected to one end of the second voltage divider capacitor and the second... The other end of the switch and one end of the third switch are connected, the other end of the third switch is connected to one end of the fourth switch and the second input terminal of the resonant cavity network, the other end of the second voltage divider capacitor and the other end of the fourth switch are connected together as the negative input terminal of the resonant converter; when the difference between the voltage across the first voltage divider capacitor and the voltage across the second voltage divider capacitor is within a set range, the driving of the second switch and the driving of the first switch are complementary, the driving of the third switch is phase-shifted by 180° relative to the driving of the first switch, and the driving of the fourth switch and the driving of the third switch are complementary; characterized in that: The switching power supply also includes the voltage equalization control device as described in claim 9.

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