Voltage-sharing control method of resonant converter circuit

Abstract

The invention discloses a voltage-sharing control method, a control device and a switching power supply. The voltage-sharing control method comprises the following steps: acquiring a voltage difference between two ends of a first voltage-dividing capacitor and a second voltage-dividing capacitor; whether the voltage difference exceeds a set range or not is judged, if yes, the driving duty ratio of a first switch tube, a second switch tube, a third switch tube and a fourth switch tube is controlled, the capacitor with the large voltage at the two ends of the first voltage dividing capacitor and the second voltage dividing capacitor is discharged, the other capacitor is charged, and the voltage difference is controlled to be within the set range. Until the voltage difference value returns to the set range; wherein when the driving duty ratios of the first switch tube, the second switch tube, the third switch tube and the fourth switch tube are controlled, the driving of the second switch tube and the driving of the first switch tube are always kept to be complementary, and the driving of the fourth switch tube and the driving of the third switch tube are always kept to be complementary. According to the method, few detection signals are needed, the working modes of the converter do not need to be distinguished, the control method is simple, and robustness is good.

Description

Technical Field

[0001] The present invention relates to the technical field of power supply, and in particular to a voltage equalization control method, a control device and a switching power supply. Background Art

[0002] At present, the commonly used resonant converter has the advantages of low voltage stress of the main power tube and ZVS of the switching tube. It is suitable for use in power conversion occasions with high voltage input, such as photovoltaic power supply and three-phase power supply. However, due to the differences in parameters of the drive circuit and the main circuit components, there is a risk of uneven voltage in the voltage-dividing capacitor, which can easily affect the safe operation of the converter. In order to achieve voltage balancing of voltage-dividing capacitors and improve the reliability of the converter, Chinese patent application number 202011051403.0 discloses a voltage balancing control method for a half-bridge three-level LLC converter circuit. The voltage balancing control method of this patent includes 6 steps: ① Set the operating mode of the half-bridge three-level LLC converter circuit, variable frequency mode or variable duty cycle mode; ② Detect the duty cycle of each switch tube 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; ④Calculate the voltage difference between the voltage divider capacitors based on the capacitor voltage; ⑤ Calculate the early shutdown time of the switch tube according to the voltage difference; ⑥ Controlling the switch tube to be turned off early according to the duty cycle, the capacitor voltage and the early turn-off time to increase or decrease the charging or discharging time of the voltage-dividing capacitor.

[0003] The early turn-off time control may result in the switch tube driving not being able to complement each other.

[0004] After in-depth research, the inventor of this application found that the control solution provided by the patent has the following shortcomings: (1) Voltage balancing is achieved by controlling the switch tube to shut down in advance. The switch tube drives are not complementary, and the switch tube will continue to flow through the body diode, resulting in large losses. In addition, if the early shutdown time is too long, the switch tube cannot achieve soft switching, resulting in large losses and poor EMI performance. (2) It is necessary to distinguish the working modes and determine the shutdown time based on the detected voltage difference. This leads to many control degrees of freedom and poor system robustness. Summary of the invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a voltage equalization control method, a control device and a switching power supply, which can solve the deficiencies of the above-mentioned prior art problems to a certain extent.

[0006] As a first aspect of the present invention, the technical solution of the embodiment of the voltage equalization control method provided is as follows: A voltage-sharing control method is applied to a resonant converter, wherein the primary circuit of the resonant converter includes a voltage-sharing circuit, a three-level switch network and a resonant cavity network; the voltage-sharing circuit includes a first voltage-sharing capacitor and a second voltage-sharing capacitor; the three-level switch network includes a first switch tube, a second switch tube, a third switch tube and a fourth switch tube; one end of the first voltage-sharing capacitor and one end of the first switch tube are connected together as the positive input end of the resonant converter, the other end of the first switch tube is connected to one end of the second switch and the first input end of the resonant cavity network, the other end of the first voltage-sharing capacitor is connected to one end of the second voltage-sharing capacitor and the other end of the second switch end 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 end of the resonant cavity network, the other end of the second voltage-dividing capacitor and the other end of the fourth switch are connected together as the negative input end of the resonant converter; when the difference between the voltage across the first voltage-dividing capacitor and the voltage across the second voltage-dividing capacitor is within a set range, the driving of the second switch tube is complementary to the driving of the first switch tube, the driving of the third switch tube is phase-shifted by 180° relative to the driving of the first switch tube, and the driving of the fourth switch tube is complementary to the driving of the third switch tube; wherein the voltage balancing control method includes: Obtaining a voltage difference between the first voltage-dividing capacitor and the second voltage-dividing capacitor; determining whether the voltage difference exceeds the set range, and if so, controlling the driving duty ratios of the first switch tube, the second switch tube, the third switch tube, and the fourth switch tube so that the capacitor with a larger voltage across both ends of the first voltage-dividing capacitor and the second voltage-dividing capacitor is discharged and the other capacitor is charged until the voltage difference returns to the set range; When controlling the driving duty ratios of the first switch tube, the second switch tube, the third switch tube and the fourth switch tube, the driving of the second switch tube is always complementary to the driving of the first switch tube, and the driving of the fourth switch tube is always complementary to the driving of the third switch tube.

[0007] Further, when the voltage across the first voltage-dividing capacitor is less than the voltage across the second voltage-dividing capacitor, if the first switch tube and the third switch are main control switch tubes, the driving duty cycle of the first switch tube is reduced, and / or the driving duty cycle of the third switch tube is increased, so that the second voltage-dividing capacitor is discharged and the first voltage-dividing capacitor is charged.

[0008] Further, when the voltage across the first voltage-dividing capacitor is less than the voltage across the second voltage-dividing capacitor, if the second switch tube and the fourth switch are main control switch tubes, the driving duty cycle of the second switch tube is reduced, and / or the driving duty cycle of the fourth switch tube is increased, so that the second voltage-dividing capacitor is discharged and the first voltage-dividing capacitor is charged.

[0009] Further, when the voltage across the first voltage-dividing capacitor is greater than the voltage across the second voltage-dividing capacitor, if the first switch tube and the third switch are main control switch tubes, the driving duty cycle of the third switch tube is reduced, and / or the driving duty cycle of the first switch tube is increased, so that the second voltage-dividing capacitor is charged and the first voltage-dividing capacitor is discharged.

[0010] Further, when the voltage across the first voltage-dividing capacitor is greater than the voltage across the second voltage-dividing capacitor, if the second switch tube and the fourth switch are main control switch tubes, the driving duty cycle of the fourth switch tube is reduced, and / or the driving duty cycle of the second switch tube is increased, so that the second voltage-dividing capacitor is charged and the first voltage-dividing capacitor is discharged.

[0011] Furthermore, the driving duty cycles of the first switch tube, the second switch tube, the third switch tube and the fourth switch tube are controlled by directly giving a certain value to the switch tube whose driving duty cycle needs to be adjusted.

[0012] Furthermore, the driving duty cycles of the first switch tube, the second switch tube, the third switch tube and the fourth switch tube are controlled by slowly adjusting the driving duty cycles of the switch tubes whose driving duty cycles need to be adjusted to a certain value.

[0013] Preferably, the voltage difference between the first voltage-dividing capacitor and the second voltage-dividing capacitor is obtained by detecting the voltage between each voltage-dividing capacitor, or by detecting the input voltage and the voltage of any voltage-dividing capacitor.

[0014] As a second aspect of the present invention, the technical solution of the embodiment of the pressure equalization control device provided is as follows: A voltage-equalizing control device is applied to a resonant converter, wherein the primary circuit of the resonant converter includes a voltage-dividing circuit, a three-level switch network and a resonant cavity network; the voltage-dividing circuit includes a first voltage-dividing capacitor and a second voltage-dividing capacitor; the three-level switch network includes a first switch tube, a second switch tube, a third switch tube and a fourth switch tube; one end of the first voltage-dividing capacitor and one end of the first switch tube are connected together as the positive input end of the resonant converter, the other end of the first switch tube is connected to one end of the second switch and the first input end of the resonant cavity network, the other end of the first voltage-dividing capacitor is connected to one end of the second voltage-dividing capacitor and the other end of the second switch end 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 end of the resonant cavity network, the other end of the second voltage-dividing capacitor and the other end of the fourth switch are connected together as the negative input end of the resonant converter; when the difference between the voltage across the first voltage-dividing capacitor and the voltage across the second voltage-dividing capacitor is within a set range, the driving of the second switch tube is complementary to the driving of the first switch tube, the driving of the third switch tube is phase-shifted by 180° relative to the driving of the first switch tube, and the driving of the fourth switch tube is complementary to the driving of the third switch tube; wherein the voltage-sharing control device comprises: An acquisition module, used for acquiring a voltage difference between the first voltage-dividing capacitor and the second voltage-dividing capacitor; a judgment module, configured to judge whether the voltage difference exceeds the set range, and if so, control the driving duty ratios of the first switch tube, the second switch tube, the third switch tube, and the fourth switch tube, so that the capacitor with a larger voltage across both ends of the first voltage-dividing capacitor and the second voltage-dividing capacitor is discharged and the other capacitor is charged, until the voltage difference returns to the set range; When controlling the driving duty ratios of the first switch tube, the second switch tube, the third switch tube and the fourth switch tube, the driving of the second switch tube is always complementary to the driving of the first switch tube, and the driving of the fourth switch tube is always complementary to the driving of the third switch tube.

[0015] As a third aspect of the present invention, the technical solution of the embodiment of the switching power supply provided is as follows: A switching power supply, comprising a resonant converter, wherein the primary circuit of the resonant converter comprises a voltage divider circuit, a three-level switch network and a resonant cavity network; the voltage divider circuit comprises a first voltage divider capacitor and a second voltage divider capacitor; the three-level switch network comprises a first switch tube, a second switch tube, a third switch tube and a fourth switch tube; one end of the first voltage divider capacitor and one end of the first switch tube are connected together as a positive input end of the resonant converter, the other end of the first switch tube is connected to one end of the second switch and the first input end 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 end of the resonant cavity network, and the other end of the second voltage-dividing capacitor and the other end of the fourth switch are connected together as the negative input end of the resonant converter; when the difference between the voltage across the first voltage-dividing capacitor and the voltage across the second voltage-dividing capacitor is within a set range, the drive of the second switch tube is complementary to the drive of the first switch tube, the drive of the third switch tube is phase-shifted by 180° relative to the drive of the first switch tube, and the drive of the fourth switch tube is complementary to the drive of the third switch tube; wherein: the switching power supply also includes the voltage equalization control device described in any one of the second aspects above.

[0016] The beneficial effects of the embodiments of the present invention are as follows: (1) The embodiment of the present invention only adjusts the duty cycle of the corresponding switch tube drive by obtaining the voltage difference between the first voltage-dividing capacitor and the second voltage-dividing capacitor to achieve voltage-dividing capacitor voltage balancing, without distinguishing the working mode of the converter. Compared with the background technology, the voltage-balancing control is simpler and more robust. (2) In the embodiment of the present invention, when controlling the size of the driving duty cycle of the corresponding switch tubes, 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 driving is still complementary during voltage equalization control. Compared with the background technology, it is beneficial to reduce losses, improve efficiency and improve EMI characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A specific schematic diagram of the principle of a resonant converter applicable to the present invention; Figure 2 This is a flow chart of a pressure equalization control method according to a first embodiment of the present invention; Figure 3 This is a schematic diagram of a first type of voltage equalization control according to a first embodiment of the present invention; Figure 4 This is a schematic diagram of a second voltage equalization control according to the first embodiment of the present invention; Figure 5 This is a schematic diagram of a third voltage equalization control according to the first embodiment of the present invention; Figure 6 This is a schematic diagram of a fourth voltage equalization control according to the first embodiment of the present invention; Figure 7 This is a schematic diagram of a fifth voltage-balanced control according to the first embodiment of the present invention; Figure 8 This is a schematic diagram of the sixth voltage equalization control according to the first embodiment of the present invention; Fig. 9 This is a seventh voltage equalization control schematic diagram of the first embodiment of the present invention; Fig.10 This is a schematic diagram of an eighth voltage-balanced control according to the first embodiment of the present invention; Fig.11 This is a ninth voltage-balanced control schematic diagram of the first embodiment of the present invention; Fig.12 This is a schematic diagram of the tenth voltage-balanced control according to the first embodiment of the present invention; Fig.13 This is a schematic diagram of the eleventh voltage-sharing control according to the first embodiment of the present invention; Fig.14 This is a schematic diagram of a twelfth type of voltage equalization control according to the first embodiment of the present invention; Fig.15 This is a thirteenth voltage-balanced control schematic diagram of the first embodiment of the present invention; Fig.16 This is the fourteenth voltage equalization control schematic diagram of the first embodiment of the present invention; Fig.17 This is a schematic diagram of the fifteenth type of voltage equalization control according to the first embodiment of the present invention; Fig.18 This is a schematic diagram of the sixteenth voltage-balanced control according to the first embodiment of the present invention; Fig.19 This is a schematic diagram of the seventeenth type of voltage equalization control according to the first embodiment of the present invention; Fig. 20 This is a schematic diagram of the eighteenth type of voltage equalization control according to the first embodiment of the present invention. DETAILED DESCRIPTION

[0018] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application may be combined with each other.

[0019] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0020] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application are described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, the process, method, system, product or equipment comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or equipment.

[0021] It should be understood that, in the specification, claims and drawings, when a step is described as being connected to another step, the step may be directly connected to the other step, or be connected to the other step through a third step; when an element / unit is described as being "connected" to another element / unit, the element / unit may be "directly connected" to the other element / unit, or be "connected" to the other element / unit through a third element / unit.

[0022] In addition, the drawings of the present disclosure are only schematic diagrams of the present disclosure and are not necessarily drawn to scale. The same symbols in the drawings represent the same or similar parts, and thus repeated descriptions thereof will be omitted. Some of the 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 using software, or implemented in one or more hardware modules or integrated circuits, or implemented in different networks and / or processor devices and / or microcontrollers.

[0023] Figure 1 A specific schematic diagram of the principle of a resonant converter applicable to the present invention is shown in FIG. Figure 1 As shown, the primary circuit of the resonant converter located on the primary side of the transformer 40 includes a voltage divider circuit 10, a three-level switch network 20 and a resonant cavity network 30, and the secondary rectifier circuit 50 and a filter capacitor Co located on the secondary side of the transformer 40.

[0024] Specifically, Figure 1As shown, the voltage divider circuit 10 includes a first voltage divider capacitor C1 and a second voltage divider capacitor C2 arranged in series, one end of the first voltage divider capacitor C1 is connected to the positive electrode of the power supply Vin, and one end of the second voltage divider capacitor C2 is connected to the negative electrode of the power supply Vin; the three-level switch network 20 includes a first switch tube Q1, a second switch tube Q2, a third switch tube Q3 and a fourth switch tube Q4 arranged in series, the drain of the first switch tube Q1 is connected to the positive electrode of the power supply Vin, the source of the fourth switch tube Q4 is connected to the negative electrode of the power supply Vin, the source of the first switch tube Q1 and the drain of the second switch tube Q2 are respectively connected to one input end of the resonant cavity network 30, that is, one end of the resonant inductor Lr in the resonant cavity network 30, the source of the third switch tube Q3 and the drain of the fourth switch tube Q4 are respectively connected to the other input end of the resonant cavity network 30, that is, one end of the resonant capacitor Cr in the resonant cavity network 30, the source of the second switch tube Q2 is connected to the drain of the third switch tube Q3 and is simultaneously connected to the other end of the first voltage divider capacitor C1 and the second voltage divider capacitor C2. It should be noted that Figure 1 The circuit located on the secondary side of the transformer 40 is only an example and should not be regarded as limiting the protection scope of the present invention. The specific design can be selected by those skilled in the art as needed.

[0025] First embodiment This embodiment provides a voltage equalization control method, using Figure 1 The three-level LLC resonant converter shown in the figure; and when the difference between the voltage across the first voltage-dividing capacitor and the voltage across the second voltage-dividing capacitor of the resonant converter is within the set range, there is no need to perform voltage equalization control, and the control strategy is: the drive of the second switch tube Q2 is complementary to the drive of the first switch tube Q1, the drive of the third switch tube Q3 is phase-shifted 180° relative to the drive of the first switch tube Q1, and the drive of the fourth switch tube Q4 is complementary to the drive of the third switch tube Q3.

[0026] Figure 2 This is a flow chart of the voltage equalization control method according to the first embodiment of the present invention. Figure 2 , the voltage equalization control method of this embodiment includes: S100, obtaining a voltage difference between the first voltage-dividing capacitor and the second voltage-dividing capacitor; S200, determining whether the voltage difference exceeds the set range, and if so, controlling the driving duty ratios of the first switch tube, the second switch tube, the third switch tube, and the fourth switch tube, so that the capacitor with a larger voltage across both ends of the first voltage-dividing capacitor and the second voltage-dividing capacitor is discharged and the other capacitor is charged, until the voltage difference returns to the set range; When controlling the driving duty ratios of the first switch tube, the second switch tube, the third switch tube and the fourth switch tube, the driving of the second switch tube is always complementary to the driving of the first switch tube, and the driving of the fourth switch tube is always complementary to the driving of the third switch tube.

[0027] The voltage balancing control method of this embodiment only adjusts the duty cycle of the corresponding switch tube drive to achieve voltage balancing of the voltage dividing capacitors by obtaining the voltage difference between the first and second voltage dividing capacitors, without distinguishing the working mode of the converter. Compared with the background technology, the voltage balancing control is simpler and has good robustness. When controlling the size of the corresponding switch tube drive duty cycle, the drive of the second switch tube is always complementary to the drive of the first switch tube, the drive of the fourth switch tube is complementary to the drive of the third switch tube, and the drives are still complementary during voltage balancing control. Compared with the background technology, it is beneficial to reduce the loss of the transformer, improve efficiency and improve EMI characteristics.

[0028] Figure 3 Schematic diagram of the first voltage equalization control of the first embodiment of the present invention. Figure 4 FIG. 1 is a schematic diagram of a second voltage-balanced control of the first embodiment of the present invention. In this embodiment, when the capacitor voltage VC1 of the first voltage-dividing capacitor is less than the capacitor voltage VC2 of the second voltage-dividing capacitor, but does not reach the hysteresis set by the designer, Figure 3 and Figure 4 As shown, the voltage balancing control signal EN1 is at a low level, the drive S1 of the switch tube Q1 and the drive S2 of the switch tube Q2 are complementary, the drive S3 of the switch tube Q3 is 180° phase-shifted relative to the drive S1 of the switch tube Q1, the drive S4 of the switch tube Q4 and the drive S3 of the switch tube Q3 are complementary, and no voltage balancing adjustment is performed.

[0029] When the capacitor voltage VC1 of the first voltage-dividing capacitor is less than the capacitor voltage VC2 of the second voltage-dividing capacitor, and the hysteresis between VC1 and VC2 is greater than the hysteresis set by the designer, if the switch tubes Q1 and Q3 are used as the main control switch tubes: Please continue to see the picture Figure 3 and Figure 4 , the voltage-equalizing control signal EN1 is flipped from a low level to a high level, the driving duty cycle of the switch tube Q1 is reduced, the switch tubes Q2 and Q1 are maintained to be driven in a complementary manner, and the driving duty cycles of the switch tubes Q3 and Q4 are maintained unchanged, so as to discharge to the second voltage-dividing capacitor C2 through the second switch tube Q2, the resonant inductor Lr, the transformer T, the resonant capacitor Cr, and the fourth switch tube Q4, and to charge the first voltage-dividing capacitor C1 through the second switch tube Q2, the resonant inductor Lr, the transformer T, the resonant capacitor Cr, the fourth switch tube Q4, the negative electrode of the power supply Vin, and the positive electrode of the power supply Vin; Or Figure 5 and Figure 6As shown, the driving duty cycle of the switch tube Q3 is increased, the switch tube Q4 is driven complementary to the switch tube Q3, and the driving duty cycles of the switch tubes Q1 and Q2 remain unchanged, so as to discharge the second voltage-dividing capacitor C2 through the third switch tube Q3, the resonant capacitor Cr, the transformer T, the resonant inductor Lr, the first switch tube Q1, the positive electrode of the power supply Vin, and the negative electrode of the power supply Vin, so as to charge the first voltage-dividing capacitor C1 through the third switch tube Q3, the resonant capacitor Cr, the transformer T, the resonant inductor Lr, and the first switch tube Q1; Both of the above methods can make the voltage difference between the first voltage-dividing capacitor and the second voltage-dividing capacitor return to the set range. The above two methods can also be used in combination, that is, the duty cycle of the switch tube Q1 is reduced and the duty cycle of the switch tube Q3 is increased at the same time. There are two paths for discharging the second voltage-dividing capacitor C2 and charging the first voltage-dividing capacitor C1, which can speed up the return of the voltage difference between the first voltage-dividing capacitor and the second voltage-dividing capacitor to the set range.

[0030] When the capacitor voltage VC1 of the first voltage-dividing capacitor is less than the capacitor voltage VC2 of the second voltage-dividing capacitor, and the hysteresis between VC1 and VC2 is greater than the hysteresis set by the designer, if the switch tubes Q2 and Q4 are used as the main control switch tubes: like Figure 7 and Figure 8 As shown, the driving duty cycle of the switch tube Q2 is reduced, the switch tubes Q1 and Q2 are maintained to be driven in a complementary manner, and the driving duty cycles of the switch tubes Q3 and Q4 are maintained unchanged, so as to discharge the second voltage-dividing capacitor C2 through the third switch tube Q3, the resonant capacitor Cr, the transformer T, the resonant inductor Lr, the first switch tube Q1, the positive electrode of the power supply Vin, and the negative electrode of the power supply Vin, so as to charge the first voltage-dividing capacitor C1 through the third switch tube Q3, the resonant capacitor Cr, the transformer T, the resonant inductor Lr, and the first switch tube Q1; Or Fig. 9 and Fig.10 As shown, the driving duty cycle of the switch tube Q4 is increased, the driving of the switch tube Q3 and the switch tube Q4 are complementary, and the driving duty cycles of the switch tubes Q1 and Q2 remain unchanged, so as to discharge to the second voltage-dividing capacitor C2 through the second switch tube Q2, the resonant inductor Lr, the transformer T, the resonant capacitor Cr, and the fourth switch tube Q4, and to charge the first voltage-dividing capacitor C1 through the second switch tube Q2, the resonant inductor Lr, the transformer T, the resonant capacitor Cr, the fourth switch tube Q4, the negative electrode of the power supply Vin, and the positive electrode of the power supply Vin; Both of the above methods can make the voltage difference between the first voltage-dividing capacitor and the second voltage-dividing capacitor return to the set range. The above two methods can also be used in combination, that is, the duty cycle of the switch tube Q2 is reduced and the duty cycle of the switch tube Q4 is increased at the same time. There are two paths for discharging the second voltage-dividing capacitor C2 and charging the first voltage-dividing capacitor C1, which can speed up the return of the voltage difference between the first voltage-dividing capacitor and the second voltage-dividing capacitor to the set range.

[0031] When the voltage balancing control makes the hysteresis of VC1 and VC2 smaller than the hysteresis set by the designer, the voltage balancing control signal EN1 flips from a high level to a low level, the switching tubes Q1 and Q2 are driven complementary, the Q3 tube drive is 180° phase-shifted relative to the Q1 tube drive, the Q4 tube drive is complementary to the Q3 drive, and the voltage balancing adjustment is not performed.

[0032] The driving duty cycle can be reduced or increased slowly, or directly given a certain value, but the maximum adjustable value needs to be limited.

[0033] The voltage-balanced control signal may be processed outside the controller or by a comparator inside the controller, and the present invention does not impose any limitation thereto.

[0034] When the capacitor voltage VC1 of the first voltage-dividing capacitor is greater than the capacitor voltage VC2 of the second voltage-dividing capacitor and the hysteresis between VC1 and VC2 is greater than the hysteresis set by the set value, if the switch tube Q1 and the switch tube Q3 are used as the main control switch tube: like Fig.11 and Fig.12 As shown, the voltage-equalizing control signal EN1 is flipped from a low level to a high level, the driving duty cycle of the switch tube Q3 is reduced, the switch tubes Q4 and Q3 are maintained to be driven in a complementary manner, and the driving duty cycles of the switch tubes Q1 and Q2 are maintained unchanged, so as to charge the second voltage-dividing capacitor C2 through the fourth switch tube Q4, the resonant capacitor Cr, the transformer T, the resonant inductor Lr, and the second switch tube Q2, and discharge the first voltage-dividing capacitor C1 through the positive electrode of the power supply Vin, the negative electrode of the power supply Vin, the fourth switch tube Q4, the resonant capacitor Cr, the transformer T, the resonant inductor Lr, the second switch tube Q2; Or Fig.13 and Fig.14 As shown, the driving duty cycle of the switch tube Q1 is increased, the driving of the switch tube Q2 is complementary to that of the switch tube Q1, and the driving duty cycles of the switch tubes Q1 and Q2 remain unchanged, so as to charge the second voltage-dividing capacitor C2 through the negative electrode of the power supply Vin, the positive electrode of the power supply Vin, the first switch tube Q1, the resonant inductor Lr, the transformer T, the resonant capacitor Cr, and the third switch tube Q3, and discharge the first voltage-dividing capacitor C1 through the first switch tube Q1, the resonant inductor Lr, the transformer T, the resonant capacitor Cr, and the third switch tube Q3; Both of the above methods can make the voltage difference between the first voltage-dividing capacitor and the second voltage-dividing capacitor return to the set range. The above two methods can also be used in combination, that is, the duty cycle of the switch tube Q3 is reduced and the duty cycle of the switch tube Q1 is increased at the same time. There are two paths for charging the second voltage-dividing capacitor C2 and discharging the first voltage-dividing capacitor C1, which can speed up the return of the voltage difference between the first voltage-dividing capacitor and the second voltage-dividing capacitor to the set range.

[0035] When the capacitor voltage VC1 of the first voltage-dividing capacitor is greater than the capacitor voltage VC2 of the second voltage-dividing capacitor and the hysteresis between VC1 and VC2 is greater than the hysteresis set by the set value, if the switch tube Q2 and the switch tube Q4 are used as the main control switch tube: like Fig.15 and 16 As shown, the driving duty cycle of the switch tube Q4 is reduced, the switch tubes Q3 and Q4 are maintained to be driven in a complementary manner, and the driving duty cycles of the switch tubes Q1 and Q2 are maintained unchanged, so that the second voltage-dividing capacitor C2 is charged through the negative electrode of the power supply Vin, the positive electrode of the power supply Vin, the first switch tube Q1, the resonant inductor Lr, the transformer T, the resonant capacitor Cr, and the third switch tube Q3, so that the first voltage-dividing capacitor C1 is discharged through the first switch tube Q1, the resonant inductor Lr, the transformer T, the resonant capacitor Cr, and the third switch tube Q3; Or Fig.17 and 18 As shown, the driving duty cycle of the switch tube Q2 is increased, the driving of the switch tube Q1 and the switch tube Q2 is complementary, and the driving duty cycles of the switch tubes Q3 and Q4 remain unchanged, so as to charge the second voltage-dividing capacitor C2 through the fourth switch tube Q4, the resonant capacitor Cr, the transformer T, the resonant inductor Lr, and the second switch tube Q2, and discharge the first voltage-dividing capacitor C1 through the positive electrode of the power supply Vin, the negative electrode of the power supply Vin, the fourth switch tube Q4, the resonant capacitor Cr, the transformer T, the resonant inductor Lr, the second switch tube Q2; Both of the above methods can make the voltage difference between the first voltage-dividing capacitor and the second voltage-dividing capacitor return to the set range. The above two methods can also be used in combination, that is, the duty cycle of the switch tube Q4 is reduced and the duty cycle of the switch tube Q2 is increased at the same time. There are two paths for charging the second voltage-dividing capacitor C2 and discharging the first voltage-dividing capacitor C1, which can speed up the return of the voltage difference between the first voltage-dividing capacitor and the second voltage-dividing capacitor to the set range.

[0036] Fig.19 and Fig. 20The figure shows a specific control schematic diagram of two paths for charging and discharging capacitors. It is for the case when the capacitor voltage VC1 of the first voltage-dividing capacitor is less than the capacitor voltage VC2 of the second voltage-dividing capacitor and the hysteresis between VC1 and VC2 is greater than the hysteresis set by the designer, the voltage-equalizing control signal EN1 is flipped from a low level to a high level, and when the switch tubes Q1 and Q3 are driven as the main control tubes, please refer to Fig.19 and Fig. 20 At the same time, the duty cycle of the switch tube Q1 is reduced and the duty cycle of the switch tube Q3 is increased. The switch tube Q2 is driven complementary to the switch tube Q1, and the switch tube Q4 is driven complementary to the switch tube Q3. There are two paths for discharging the second voltage-dividing capacitor C2. One is to discharge to the second voltage-dividing capacitor C2 through the second switch tube Q2, the resonant inductor Lr, the transformer T, the resonant capacitor Cr, and the fourth switch tube Q4. The second is to discharge the second voltage-dividing capacitor C2 through the third switch tube Q3, the resonant capacitor Cr, the transformer T, the resonant inductor Lr, the first switch tube Q1, the positive electrode of the power supply Vin, and the negative electrode of the power supply Vin. There are two paths for charging the first voltage-dividing capacitor C1. One is to charge the first voltage-dividing capacitor C1 through the second switch tube Q2, the resonant inductor Lr, the transformer T, the resonant capacitor Cr, the fourth switch tube Q4, the negative electrode of the power supply Vin, and the positive electrode of the power supply Vin. The second is to charge the first voltage-dividing capacitor C1 through the third switch tube Q3, the resonant capacitor Cr, the transformer T, the resonant inductor Lr, and the first switch tube Q1.

[0037] When the capacitor voltage VC1 of the first voltage-dividing capacitor is less than the capacitor voltage VC2 of the second voltage-dividing capacitor and the hysteresis between VC1 and VC2 is less than the hysteresis set by the designer, the control signal EN1 is inverted from a high level to a low level, and voltage equalization adjustment is no longer performed.

[0038] Second embodiment The present embodiment discloses a voltage-sharing control device, which is applied to a resonant converter. The primary circuit of the resonant converter includes a voltage-sharing circuit, a three-level switch network and a resonant cavity network; the voltage-sharing circuit includes a first voltage-sharing capacitor and a second voltage-sharing capacitor; the three-level switch network includes a first switch tube, a second switch tube, a third switch tube and a fourth switch tube; one end of the first voltage-sharing capacitor and one end of the first switch tube are connected together as a positive input end of the resonant converter, the other end of the first switch tube is connected to one end of the second switch and the first input end of the resonant cavity network, the other end of the first voltage-sharing capacitor is connected to one end of the second voltage-sharing 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 end of the resonant cavity network, and the other end of the second voltage-sharing capacitor and the other end of the fourth switch are connected together as a negative input end of the resonant converter; when the difference between the voltage across the first voltage-sharing capacitor and the voltage across the second voltage-sharing capacitor is within a set range, the driving of the second switch tube is complementary to the driving of the first switch tube, the driving of the third switch tube is phase-shifted by 180° relative to the driving of the first switch tube, and the driving of the fourth switch tube is complementary to the driving of the third switch tube; the voltage-sharing control device includes: An acquisition module, used for acquiring a voltage difference between the first voltage-dividing capacitor and the second voltage-dividing capacitor; a judgment module, used to judge whether the voltage difference exceeds the set range, and if so, control the driving duty ratios of the first switch tube, the second switch tube, the third switch tube and the fourth switch tube, so that the capacitor with the larger voltage across the first and second voltage-dividing capacitors is discharged and the other capacitor is charged, until the voltage difference returns to the set range; When controlling the driving duty ratios of the first switch tube, the second switch tube, the third switch tube and the fourth switch tube, the driving of the second switch tube is always complementary to the driving of the first switch tube, and the driving of the fourth switch tube is always complementary to the driving of the third switch tube.

[0039] The technical means adopted by the control device of this embodiment correspond to and are consistent with the control method of the first embodiment, and have the same beneficial effects, so they will not be described in detail. In addition, the preferred technical means or further improved means of each step in the control method of the first embodiment can be extended to the corresponding units of this embodiment, and this embodiment will not describe them one by one.

[0040] Third embodiment The present embodiment provides a switching power supply, including a resonant converter, wherein the primary circuit of the resonant converter includes a voltage divider circuit, a three-level switch 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 switch network includes a first switch tube, a second switch tube, a third switch tube and a fourth switch tube; one end of the first voltage divider capacitor and one end of the first switch tube are connected together as the positive input end of the resonant converter, the other end of the first switch tube is connected to one end of the second switch and the first input end 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 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 end of the resonant cavity network, the other end of the second voltage-dividing capacitor and the other end of the fourth switch are connected together as the negative input end of the resonant converter; when the difference between the voltage across the first voltage-dividing capacitor and the voltage across the second voltage-dividing capacitor is within a set range, the drive of the second switch tube is complementary to the drive of the first switch tube, the drive of the third switch tube is phase-shifted by 180° relative to the drive of the first switch tube, and the drive of the fourth switch tube is complementary to the drive of the third switch tube; wherein: the switching power supply also includes any one of the voltage-equalizing control devices in the second embodiment above.

[0041] Since the switching power supply of this embodiment includes any one of the voltage equalization control devices in the second embodiment above, when achieving voltage equalization between the voltage-dividing capacitors, fewer detection signals are required, the control method is simple, and the resonant converter can be effectively prevented from entering hard switching, which is beneficial to improving the efficiency of the switching power supply and reducing the EMI interference of the converter.

[0042] The description of the above embodiments is only used to help 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 principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A voltage-sharing control method, applied to a resonant converter, wherein the primary circuit of the resonant converter comprises a voltage-sharing circuit, a three-level switch network and a resonant cavity network; the voltage-sharing circuit comprises a first voltage-sharing capacitor and a second voltage-sharing capacitor; the three-level switch network comprises a first switch tube, a second switch tube, a third switch tube and a fourth switch tube; one end of the first voltage-sharing capacitor and one end of the first switch tube are connected together as a positive input end of the resonant converter, the other end of the first switch tube is connected to one end of the second switch and a first input end of the resonant cavity network, the other end of the first voltage-sharing capacitor is connected to one end of the second voltage-sharing capacitor, the third switch tube and a fourth switch tube; The other end of the second switch is connected to 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 end of the resonant cavity network, the other end of the second voltage-dividing capacitor and the other end of the fourth switch are connected together as the negative input end of the resonant converter; when the difference between the voltage across the first voltage-dividing capacitor and the voltage across the second voltage-dividing capacitor is within a set range, the drive of the second switch tube is complementary to the drive of the first switch tube, the drive of the third switch tube is phase-shifted by 180° relative to the drive of the first switch tube, and the drive of the fourth switch tube is complementary to the drive of the third switch tube; characterized in that, The voltage equalization control method comprises: Obtaining a voltage difference between the first voltage-dividing capacitor and the second voltage-dividing capacitor; determining whether the voltage difference exceeds the set range, and if so, controlling the driving duty ratios of the first switch tube, the second switch tube, the third switch tube, and the fourth switch tube so that the capacitor with a larger voltage across both ends of the first voltage-dividing capacitor and the second voltage-dividing capacitor is discharged and the other capacitor is charged until the voltage difference returns to the set range; When controlling the driving duty ratios of the first switch tube, the second switch tube, the third switch tube and the fourth switch tube, the driving of the second switch tube is always complementary to the driving of the first switch tube, and the driving of the fourth switch tube is always complementary to the driving of the third switch tube.

2. The voltage equalization control method according to claim 1, characterized in that: When the voltage across the first voltage-dividing capacitor is less than the voltage across the second voltage-dividing capacitor, if the first switch tube and the third switch are main control switch tubes, the driving duty cycle of the first switch tube is reduced, and / or the driving duty cycle of the third switch tube is increased, so that the second voltage-dividing capacitor is discharged and the first voltage-dividing capacitor is charged.

3. The voltage equalization control method according to claim 1, characterized in that: When the voltage across the first voltage-dividing capacitor is less than the voltage across the second voltage-dividing capacitor, if the second switch tube and the fourth switch are main control switch tubes, the driving duty cycle of the second switch tube is reduced, and / or the driving duty cycle of the fourth switch tube is increased, so that the second voltage-dividing capacitor is discharged and the first voltage-dividing capacitor is charged.

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

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

6. The voltage equalization control method according to claim 1, characterized in that: The driving duty cycles of the first switch tube, the second switch tube, the third switch tube and the fourth switch tube are controlled by directly giving a certain value to the switch tube whose driving duty cycle needs to be adjusted.

7. The voltage equalization control method according to claim 1, characterized in that: The driving duty ratios of the first switch tube, the second switch tube, the third switch tube and the fourth switch tube are controlled by slowly adjusting the switch tubes whose driving duty ratios need to be adjusted to a certain value.

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-dividing capacitor and the second voltage-dividing capacitor is obtained by detecting the voltage between the two ends of each voltage-dividing capacitor, or by detecting the input voltage and the voltage of any voltage-dividing capacitor.

9. A voltage-equalizing control device, applied to a resonant converter, wherein the primary circuit of the resonant converter comprises a voltage-dividing circuit, a three-level switch network and a resonant cavity network; the voltage-dividing circuit comprises a first voltage-dividing capacitor and a second voltage-dividing capacitor; the three-level switch network comprises a first switch tube, a second switch tube, a third switch tube and a fourth switch tube; one end of the first voltage-dividing capacitor and one end of the first switch tube are connected together as the positive input end of the resonant converter, the other end of the first switch tube is connected to one end of the second switch and the first input end of the resonant cavity network, the other end of the first voltage-dividing capacitor is connected to one end of the second voltage-dividing capacitor, the third switch tube and the fourth switch tube; The other end of the second switch is connected to 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 end of the resonant cavity network, the other end of the second voltage-dividing capacitor and the other end of the fourth switch are connected together as the negative input end of the resonant converter; when the difference between the voltage across the first voltage-dividing capacitor and the voltage across the second voltage-dividing capacitor is within a set range, the drive of the second switch tube is complementary to the drive of the first switch tube, the drive of the third switch tube is phase-shifted by 180° relative to the drive of the first switch tube, and the drive of the fourth switch tube is complementary to the drive of the third switch tube; characterized in that, The pressure equalizing control device comprises: An acquisition module, used for acquiring a voltage difference between the first voltage-dividing capacitor and the second voltage-dividing capacitor; a judgment module, configured to judge whether the voltage difference exceeds the set range, and if so, control the driving duty ratios of the first switch tube, the second switch tube, the third switch tube, and the fourth switch tube, so that the capacitor with a larger voltage across both ends of the first voltage-dividing capacitor and the second voltage-dividing capacitor is discharged and the other capacitor is charged, until the voltage difference returns to the set range; When controlling the driving duty ratios of the first switch tube, the second switch tube, the third switch tube and the fourth switch tube, the driving of the second switch tube is always complementary to the driving of the first switch tube, and the driving of the fourth switch tube is always complementary to the driving of the third switch tube.

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

Images