DC Converter

Abstract

The embodiment of the present application provides a DC converter, including a first active switching inductor unit, a second active switching inductor unit, a voltage conversion unit, an output filter unit, a first clamping control unit, and a second clamping control unit. By connecting the negative end of the input side to point A of the output filter unit, the output filter unit is divided into a first output filter sub-unit and a second output filter sub-unit using point A, so that the voltage conversion unit is connected to the first output filter sub-unit through the first clamping control unit, and is connected to the second output filter sub-unit through the second clamping control unit. The voltage of the first active switching inductor unit and the second active switching inductor unit is clamped to prevent voltage oscillation and reduce EMI interference. Furthermore, compared with the prior art, the structural complexity and cost of the DC converter provided in this embodiment have not changed significantly, but it has higher gain and lower voltage and current stress, and the efficiency of DC conversion is higher.

Description

Technical Field

[0001] The embodiments of the present application relate to the technical field of energy storage systems, and in particular to a direct current converter. Background Art

[0002] For renewable energy systems, fuel cells, hybrid vehicles and other occasions, the output voltage of power modules such as photovoltaic cells, fuel cells and batteries is relatively low. For example, when energy storage batteries are connected to the grid, the voltage level of the energy storage batteries is usually 20-60V, while the voltage level of the DC bus is higher, generally 400V. Therefore, a high-gain and low-stress DC (DC-DC) converter is required to significantly increase the voltage level of new energy.

[0003] Among them, when the DC-DC converter is in use, resonance is easily formed between its internal inductance and the parasitic capacitance of the active switching element, causing the switching element voltage to oscillate; and it is also necessary to ensure that the potential difference between the input ground and the output ground is constant, otherwise leakage current will be generated from the converter end to the ground, which is equivalent to a capacitor in a charging and discharging state between the ground and the load end, resulting in a potential difference between the ground and the load end, thereby causing electromagnetic interference (EMI) problems.

[0004] In the prior art, for voltage oscillations that occur when the converter is in use, a clamping loop is set in the converter circuit to clamp the voltage of the parasitic capacitance of the active switching element to eliminate the voltage oscillations; for EMI problems, the input ground and the output ground are generally shared ground so that the voltage between the input ground and the output ground is equal, ensuring that the potential difference between the input ground and the output ground is 0 and constant.

[0005] Although such DC-DC converters in the prior art can achieve low voltage to high voltage conversion, as users' requirements for high gain and low stress of DC-DC converters increase, current DC-DC converters have been unable to meet user requirements. Summary of the invention

[0006] The embodiment of the present application provides a DC converter to solve the technical problems mentioned in the background technology.

[0007] The embodiment of the present application provides a DC converter, comprising: a first active switching inductor unit, a second active switching inductor unit, a voltage conversion unit, an output filter unit, a first clamping control unit, and a second clamping control unit; The first active switching inductor unit and the second active switching inductor unit are connected in parallel at two ends of the input side, the output filter unit is connected at two ends of the load side, the negative end of the input side is connected to the A end point of the output filter unit, the A end point is an internal end point of the output filter unit, and the A end point divides the output filter unit into a first output filter sub-unit and a second output filter sub-unit; The first active switch inductor unit and the second active switch inductor unit are both connected to the voltage conversion unit, the voltage conversion unit is connected to the first output filter subunit via the first clamp control unit, and the voltage conversion unit is connected to the second output filter subunit via the second clamp control unit; The first active switching inductor unit, the voltage conversion unit, the first clamping control unit and the first output filtering subunit constitute a first clamping loop, and the second active switching inductor unit, the voltage conversion unit, the second clamping control unit and the second output filtering subunit constitute a second clamping loop.

[0008] Optionally, the first clamping circuit is used to clamp the voltage of the first active switching inductor unit when it is in a preset state to prevent the first active switching inductor unit from resonating with other components in the DC converter, and the second clamping circuit is used to clamp the voltage of the second active switching inductor unit when it is in a preset state to prevent the second active switching inductor unit from resonating with other components in the DC converter.

[0009] Optionally, the first active switch inductor unit and the second active switch inductor unit both include: an active switch subunit and an inductor subunit; One end of the voltage conversion unit is connected between the active switch subunit and the inductor subunit in the first active switch inductor unit, and the other end of the voltage conversion unit is connected between the active switch subunit and the inductor subunit in the second active switch inductor unit.

[0010] Optionally, the preset state is a state in which an active switch subunit in the first active switch inductor unit and an active switch subunit in the second active switch inductor unit are disconnected.

[0011] Optionally, the first clamping circuit is used to perform voltage clamping on the active switch sub-unit when the active switch sub-unit in the first active switch inductor unit is disconnected; The second clamping loop is used to clamp the voltage of the active switch sub-unit when the active switch sub-unit in the second active switch inductor unit is disconnected.

[0012] Optionally, when the active switch subunit is disconnected, an equivalent capacitance is generated at the location of the active switch subunit; The first clamping loop is used to perform voltage clamping on an equivalent capacitor corresponding to the active switch subunit when the active switch subunit in the first active switch inductor unit is disconnected; The second clamping loop is used to perform voltage clamping on an equivalent capacitor corresponding to the active switch subunit when the active switch subunit in the second active switch inductor unit is disconnected.

[0013] Optionally, the A endpoint is the midpoint of the output filter unit, so that the first output filter subunit and the second output filter subunit have symmetrical structures.

[0014] Optionally, the voltage conversion unit includes: a first voltage conversion subunit, a second voltage conversion subunit, a third voltage conversion subunit and a first switch control subunit, a second switch control subunit, and a third switch control subunit; One end of the first switch control subunit, the second switch control subunit and the third voltage conversion subunit is connected to the first active switch inductor unit, the other end of the first switch control subunit is connected to one end of the first voltage conversion subunit and the second output filter subunit, the other end of the first voltage conversion subunit and one end of the second voltage conversion subunit are connected to the second active switch inductor unit, the other end of the second switch control subunit and one end of the third switch control subunit are connected to the other end of the second voltage conversion subunit, and the other end of the third switch control subunit is connected between the other end of the third voltage conversion subunit and the first output filter subunit; The first active switching inductor unit, the third voltage conversion subunit, the first clamping control unit and the first output filtering subunit constitute the first clamping loop, and the second active switching inductor unit, the input side, the first voltage conversion subunit, the second clamping control unit and the second output filtering subunit constitute the second clamping loop.

[0015] Optionally, the first voltage conversion subunit, the second voltage conversion subunit, and the third voltage conversion subunit all include capacitors.

[0016] Optionally, one end of the first voltage conversion subunit, one end of the second voltage conversion subunit, and one end of the third voltage conversion subunit are all positive ends, and the other end of the first voltage conversion subunit, the other end of the second voltage conversion subunit, and the other end of the third voltage conversion subunit are all negative ends.

[0017] Optionally, the first switch control subunit, the second switch control subunit, and the third switch control subunit all include a first semiconductor switch tube, and the first semiconductor switch tube includes at least one of the following: a diode, a MOS tube, an IGBT, and a SiC switch tube. 8. The DC converter according to claim 3, characterized in that the active switch subunit includes a second semiconductor switch tube, and the second semiconductor switch tube includes at least one of the following: a MOS tube, an IGBT, and a SiC switch tube.

[0018] Optionally, the first clamping control unit and the second clamping control unit each include at least one of the following: a diode, a MOS tube, and an IGBT.

[0019] Optionally, the gain of the DC converter is: in, represents the gain of the isolated DC converter; d represents the duty cycle of the DC converter.

[0020] The present application provides a DC converter, comprising a first active switching inductor unit, a second active switching inductor unit, a voltage conversion unit, an output filter unit, a first clamp control unit and a second clamp control unit. The first active switching inductor unit and the second active switching inductor unit are connected in parallel at two ends of an input side, and the output filter unit is connected at two ends of a load side. The first active switching inductor unit and the second active switching inductor unit are both connected to the voltage conversion unit. By connecting the negative end of the input side to point A of the output filter unit, the output filter unit is divided into a first output filter sub-unit and a second output filter sub-unit by using point A, so that the voltage conversion unit is connected to the first output filter sub-unit through the first clamp control unit and is connected to the second output filter sub-unit through the second clamp control unit, so that the first active switching inductor unit, the voltage conversion unit, the first clamp control unit and the first output filter sub-unit constitute a first clamp loop, and the second active switching inductor unit, the voltage conversion unit, the second clamp control unit and the second output filter sub-unit constitute a second clamp loop. Furthermore, the voltages of the voltage conversion unit, the first output filter subunit, and the second output filter subunit are all constant, so the voltages of the first active switch inductor unit and the second active switch inductor unit can be clamped to prevent voltage oscillation and reduce EMI interference. Furthermore, compared with the prior art, the structural complexity and cost of the DC converter provided in this embodiment do not change significantly, but it has higher gain and lower voltage and current stress, and the efficiency of DC conversion is higher, meeting user needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0022] Figure 1 A structural block diagram of a DC converter provided in one embodiment of the present application; Figure 2 A structural block diagram of a DC converter provided in another embodiment of the present application Figure 3 A circuit diagram of a DC converter provided in one embodiment of the present application; Figure 4 A circuit diagram of a clamping loop of S1 in a DC converter provided in an embodiment of the present application; Figure 5 A circuit diagram of a clamping loop of S2 in a DC converter provided in an embodiment of the present application; Figure 6 An equivalent circuit diagram of a DC converter in Mode I provided by an embodiment of the present application; Figure 7 An equivalent circuit diagram of a DC converter in Mode II provided in an embodiment of the present application; Figure 8 In one cycle provided by an embodiment of the present application Figure 3 The waveform diagram of the DC converter is shown. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, 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 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 are within the scope of protection of this application.

[0024] DC-DC converters are widely used in photovoltaic, energy storage, fuel cell and other new energy applications to convert low voltage DC power into high voltage DC power, thereby connecting the electric energy to the high voltage DC bus. Therefore, DC converters need to have the characteristics of high gain and low stress.

[0025] Among them, when the DC converter is in use, resonance is easily formed between its internal inductance and the parasitic capacitance of the active switching element, causing the switching element voltage to oscillate. In addition, it is also necessary to ensure that the potential difference between the input ground and the output ground is constant, otherwise leakage current will be generated to the ground, which is equivalent to a capacitor in a charging and discharging state between the ground and the load end, resulting in a potential difference between the ground and the load end, thereby causing EMI problems.

[0026] In the prior art, in order to solve the voltage oscillation problem, a clamping loop is set in the converter circuit to clamp the voltage of the parasitic capacitance of the active switching element to eliminate the voltage oscillation; for the EMI problem, the input ground and the output ground are generally grounded to make the voltage between the input ground and the output ground equal, ensuring that the potential difference between the input ground and the output ground is 0 and constant.

[0027] The DC converter in the prior art has certain high gain and low stress. However, as users' demands for high gain and low stress of DC converters increase, the current DC converters can hardly meet the users' demands.

[0028] Therefore, the present application provides a DC converter, including a first active switching inductor unit, a second active switching inductor unit, a voltage conversion unit, an output filter unit, a first clamping control unit and a second clamping control unit, wherein the number of components included in the DC converter provided by the present application can be equivalent to the number of components included in the disclosed DC converter, but the connection structure between the components is different, that is, in the present application, by splitting the output filter unit into two parts, a first output filter sub-unit and a second output filter sub-unit, the first output filter sub-unit constitutes a clamping loop of the first active switching inductor unit, and the second output filter sub-unit constitutes a clamping loop of the second active switching inductor unit, thereby changing the internal structure of the DC converter, so that the DC converter of the present application has higher gain and lower voltage and current stress than the disclosed DC converter on the basis of solving the voltage oscillation and EMI problems.

[0029] It is worth noting that the active switching inductor unit and the voltage conversion unit are combined to control the duty cycle through active switching devices, adjust the DC voltage, and then realize the basic function of DC conversion. The present application solves the voltage oscillation and EMI problems by setting a clamping circuit that reuses existing components on the original structure of the DC converter.

[0030] Figure 1 This is a structural block diagram of a DC converter provided in one embodiment of the present application. Figure 1As shown, the DC converter provided in this embodiment includes: a first active switching inductor unit 110, a second active switching inductor unit 120, a voltage conversion unit 130, an output filter unit 140, a first clamping control unit 150 and a second clamping control unit 160; The first active switching inductor unit 110 and the second active switching inductor unit 120 are connected in parallel at both ends of the input side 170, the output filter unit 140 is connected at both ends of the load side 180, the negative end of the input side 170 is connected to point A of the output filter unit 140, point A is an internal point of the output filter unit 140, and point A divides the output filter unit 140 into a first output filter sub-unit 141 and a second output filter sub-unit 142; The first active switch inductor unit 110 and the second active switch inductor unit 120 are both connected to the voltage conversion unit 130, the voltage conversion unit 130 is connected to the first output filter subunit 141 through the first clamp control unit 150, and the voltage conversion unit 130 is connected to the second output filter subunit 142 through the second clamp control unit 160; The first active switching inductor unit 110, the voltage conversion unit 130, the first clamping control unit 150 and the first output filtering subunit 141 constitute a first clamping loop, and the second active switching inductor unit 120, the voltage conversion unit 130, the second clamping control unit 160 and the second output filtering subunit 142 constitute a second clamping loop.

[0031] In this embodiment, the first active switch inductor unit 110 and the second active switch inductor unit 120 are used to control the on and off of the DC converter, wherein the first active switch inductor unit 110 and the second active switch inductor unit 120 operate in unison, i.e., they are turned on and off at the same time. Since the first active switch inductor unit 110 and the second active switch inductor unit 120 include inductors, the DC power input from the input side 170 can be filtered to eliminate interference.

[0032] The voltage conversion unit 130 is used to convert the voltage level. Generally, in a DC converter, the voltage conversion unit 130 is used to boost the voltage, that is, to boost the low voltage of the input side 170 to a high voltage to provide the high voltage to the load side 180. The voltage of the voltage conversion unit 130 is constant.

[0033] It should be noted that the constant voltage mentioned in the embodiments of the present application means that the voltage changes within a preset deviation range. For example, the voltage is considered to be constant within the range of ±5~15% of the preset voltage value.

[0034] The output filter unit 140 is used to filter the converted voltage and eliminate the AC voltage in the DC voltage to provide a more stable DC high voltage to the load side 180. The voltage of the output filter unit 140 is also constant.

[0035] The first clamp control unit 150 and the second clamp control unit 160 are used to control the flow direction of the current in the DC converter so that the DC converter can achieve voltage conversion and form a first clamp loop and a second clamp loop. The first clamp loop acts on the first active switch inductor unit 110, and the second clamp loop acts on the second active switch inductor unit 120. Optionally, the structures of the first clamp control unit 150 and the second clamp control unit 160 can be the same, and can include at least one of the following: a diode, a MOS tube, an IGBT, and a SiC switch tube.

[0036] In terms of circuit structure, the negative end of the input side 170 is connected to the point A of the output filter unit 140, and the output filter unit 140 is divided into a first output filter subunit 141 and a second output filter subunit 142 through the point A, so that the voltage conversion unit 130 is connected to the first output filter subunit 141 through the first clamp control unit 150, and is connected to the second output filter subunit 142 through the second clamp control unit 160. Optionally, the point A is the midpoint of the output filter unit 140, so that the first output filter subunit 141 and the second output filter subunit 142 have the same structure.

[0037] The voltages of the first output filter subunit 141 and the second output filter subunit 142 are both constant. Figure 1 It can be seen that the second output filter sub-unit 142 is between the negative end of the input side 170 and the negative end of the load side 180. Therefore, the voltage between the negative end of the input side 170 and the negative end of the load side 180 is constant, that is, the second output filter sub-unit 142 plays a role in maintaining the voltage between the negative end of the input side 170 and the negative end of the load side 180 constant. Therefore, the DC converter provided in this embodiment can reduce EMI interference.

[0038] In this way, under the control of the first clamp control unit 150 and the second clamp control unit 160, the first active switching inductor unit 110, the voltage conversion unit 130, the first clamp control unit 150 and the first output filter subunit 141 form a first clamp loop, and the second active switching inductor unit 120, the voltage conversion unit 130, the second clamp control unit 160 and the second output filter subunit 142 form a second clamp loop. Among them, the voltage of the voltage conversion unit 130 and the first output filter subunit 141 is constant, so the voltage of the first active switching inductor unit 110 is constant, and similarly, the voltage of the second active switching inductor unit 120 is constant, thereby effectively suppressing the voltage oscillation of the first active switching inductor unit 110 and the second active switching inductor unit 120.

[0039] Among them, the output filter unit 140 not only plays a filtering role, but also constitutes a part of the clamping loop, that is, the first output filter subunit 141 constitutes a first clamping loop for clamping the voltage of the first active switching inductor unit 110, and the second output filter subunit 142 constitutes a second clamping loop for clamping the voltage of the second active switching inductor unit 120. Moreover, compared with the prior art, when constituting the clamping loop, the first clamping loop and the second clamping loop do not include the entire output filter unit 140, but respectively include a part of the output filter unit 140. Optionally, the output filter unit 140 in this embodiment can be the output filter unit 140 of the DC converter in the prior art, and this application does not limit this.

[0040] It should be noted that the first active switch inductor unit 110 and the second active switch inductor unit 120 in this embodiment can also be active switch inductor units with the same function in the prior art; the components included in the voltage conversion unit 130 can also be components included in the voltage conversion unit 130 with the same function in the prior art, and the first clamp control unit 150 and the second clamp control unit 160 can also refer to the clamp control unit with the same function in the prior art, but their connection relationship and position in the circuit are changed. In other words, the types and quantities of components included in the DC converter in this embodiment are not very different from the types and quantities of components included in the DC converter in the prior art, and the main difference is their structure.

[0041] The working process is that when the first active switch inductor unit 110 and the second active switch inductor unit 120 are turned on, the voltage of the input side 170 is boosted by the voltage conversion unit 130, and the boosted voltage is filtered by the output filter unit 140 and then transmitted to the load side 180. Among them, based on the structure of the DC converter provided in this embodiment, it has a higher gain and lower current and voltage stress when boosting the voltage, and the specific principle is referred to below.

[0042] In this embodiment, the DC converter includes a first active switching inductor unit 110, a second active switching inductor unit 120, a voltage conversion unit 130, an output filter unit 140, a first clamp control unit 150, and a second clamp control unit 160. The first active switching inductor unit 110 and the second active switching inductor unit 120 are connected in parallel at both ends of the input side 170, and the output filter unit 140 is connected to both ends of the load side 180. The first active switching inductor unit 110 and the second active switching inductor unit 120 are both connected to the voltage conversion unit 130. By connecting the negative end of the input side 170 to the point A of the output filter unit 140, the output filter unit 150 is connected to the load side 180 by using the point A. The wave unit 140 is divided into a first output filter subunit 141 and a second output filter subunit 142, so that the voltage conversion unit 130 is connected to the first output filter subunit 141 through the first clamp control unit 150, and is connected to the second output filter subunit 142 through the second clamp control unit 160, so that the first active switch inductor unit 110, the voltage conversion unit 130, the first clamp control unit 150 and the first output filter subunit 141 constitute a first clamp loop, and the second active switch inductor unit 120, the voltage conversion unit 130, the second clamp control unit 160 and the second output filter subunit 142 constitute a second clamp loop. In addition, the voltages of the voltage conversion unit 130, the first output filter subunit 141 and the second output filter subunit 142 are all constant, so the voltages of the first active switch inductor unit 110 and the second active switch inductor unit 120 can be clamped to prevent voltage oscillation and reduce EMI interference. Furthermore, compared with the prior art, the structural complexity and cost of the DC converter provided in this embodiment have not changed significantly, but have higher gain and lower voltage and current stress, and the efficiency of DC conversion is higher, meeting user needs.

[0043] Optionally, in the DC converter, since the first active switching inductor unit 110 and the second active switching inductor unit 120 operate in unison, when the first active switching inductor unit 110 and the second active switching inductor unit 120 are in the same preset state, the first clamping loop clamps the voltage of the first active switching inductor unit 110 to prevent the first active switching inductor unit 110 from resonating with other components in the DC converter, such as components with inductance characteristics. Similarly, the second clamping loop clamps the voltage of the second active switching inductor unit 120 to prevent the second active switching inductor unit 120 from resonating with other components in the DC converter.

[0044] Among them, the first active switching inductor unit 110 and the second active switching inductor unit 120 have a voltage oscillation problem, which is mainly due to the presence of an active switch part and an inductor part in the first active switching inductor unit 110 and the second active switching inductor unit 120, namely, the active switch sub-unit 210 and the inductor sub-unit 220 in the present application, and when the active switch sub-unit 210 is converted from an on state to an off state, the active switch sub-unit 210 and the inductor sub-unit 220 will form a resonance, resulting in a voltage oscillation of the active switch sub-unit 210.

[0045] For Figure 2 In the DC converter shown, one end of the voltage conversion unit 130 is connected between the active switch subunit 210 and the inductor subunit 220 in the first active switch inductor unit 110, and the other end of the voltage conversion unit 130 is connected between the active switch subunit 210 and the inductor subunit 220 in the second active switch inductor unit 120. Therefore, the first clamping loop is composed of the active switch subunit 210 in the first active switch inductor unit 110, the voltage conversion unit 130, the first clamping control unit 150 and the first output filter subunit 141, so as to clamp the voltage of the active switch subunit 210 when it is in the disconnected state; the second clamping loop is composed of the active switch subunit 210 in the second active switch inductor unit 120, the voltage conversion unit 130, the second clamping control unit 160 and the second output filter subunit 142, so as to clamp the voltage of the active switch subunit 210 when it is in the disconnected state to avoid voltage oscillation.

[0046] Further, when the active switch subunit 210 is converted from the on state to the off state, the reason why the active switch subunit 210 and the inductor subunit 220 form resonance is that the active switch subunit 210 contains a semiconductor switch tube, such as a MOS tube, an IGBT, and a SiC switch tube, which are active switch devices, so that the active switch subunit 210 has parasitic capacitance, that is, the equivalent capacitance in this application. In this way, when the active switch subunit 210 is disconnected, the equivalent capacitance and the inductance in the inductor subunit 220 form an oscillation. Therefore, it is necessary to perform voltage clamping on the equivalent capacitance corresponding to the first active switch inductor unit 110 through the first clamping loop, and to perform voltage clamping on the equivalent capacitance corresponding to the second active switch inductor unit 120 through the second clamping loop to prevent voltage oscillation.

[0047] Optional, such as Figure 2 As shown, the voltage conversion unit 130 includes: a first voltage conversion subunit 131, a second voltage conversion subunit 132, a third voltage conversion subunit 133 and a first switch control subunit 134, a second switch control subunit 135, and a third switch control subunit 136; One end of the first switch control subunit 134, the second switch control subunit 135 and the third voltage conversion subunit 133 is connected to the first active switch inductor unit 110, the other end of the first switch control subunit 134 is connected to one end of the first voltage conversion subunit 131 and the second output filter subunit 142, the other end of the first voltage conversion subunit 131 and one end of the second voltage conversion subunit 132 are connected to the second active switch inductor unit 120, the other end of the second switch control subunit 135 and one end of the third switch control subunit 136 are connected to the other end of the second voltage conversion subunit 132, and the other end of the third switch control subunit 136 is connected between the other end of the third voltage conversion subunit 133 and the first output filter subunit 141; The first active switching inductor unit 110, the third voltage conversion subunit 133, the first clamping control unit 150 and the first output filtering subunit 141 constitute a first clamping loop, and the second active switching inductor unit 120, the input side 170, the first voltage conversion subunit 131, the second clamping control unit 160 and the second output filtering subunit 142 constitute a second clamping loop.

[0048] In this embodiment, the first voltage conversion subunit 131, the second voltage conversion subunit 132, and the third voltage conversion subunit 133 can have the same structure and constant voltage. Since the capacitor has the function of charging and discharging, the voltage can be boosted through the charging and discharging process. Therefore, the first voltage conversion subunit 131, the second voltage conversion subunit 132, and the third voltage conversion subunit 133 can all include capacitors.

[0049] The structures of the first switch control subunit 134, the second switch control subunit 135, and the third switch control subunit 136 may also be the same, and the first switch control subunit 134, the second switch control subunit 135, and the third switch control subunit 136 may all be switch-controlled by semiconductor switch tubes, wherein the semiconductor switch tubes may include at least one of the following: diodes, MOS tubes, IGBTs, and SiC switch tubes.

[0050] exist Figure 2 In the structure shown, the active switch subunit 210 in the first active switch inductor unit 110, the third voltage conversion subunit 133, the first clamping control unit 150 and the first output filter subunit 141 constitute a first clamping loop. Since the voltages of the third voltage conversion subunit 133 and the first output filter subunit 141 are constant, the first clamping loop can achieve voltage clamping of the active switch subunit 210 in the first active switch inductor unit 110.

[0051] Similarly, the active switch subunit 210 in the second active switch inductor unit 120, the input side 170, the first voltage conversion subunit 131, the second clamp control unit 160, and the second output filter subunit 142 form a second clamp loop. Since the voltages of the input side 170, the first voltage conversion subunit 131, and the second output filter subunit 142 are all constant, the second clamp loop can achieve voltage clamping of the active switch subunit 210 in the second active switch inductor unit 120.

[0052] Among them, Figure 2 As shown, in terms of connection sequence, the positive end of the first voltage conversion subunit 131 and the negative end of the second voltage conversion subunit 132 are connected between the active switch subunit 210 and the inductor subunit 220 of the second active switch inductor unit 120, the negative end of the first voltage conversion subunit 131 and the positive end of the second voltage conversion subunit 132 are connected to the negative end of the third voltage conversion subunit 133 and connected between the active switch subunit 210 and the inductor subunit 220 of the first active switch inductor unit 110, the positive end of the third voltage conversion subunit 133 is connected to the positive end of the first output filter subunit 141, the negative end of the first output filter subunit 141 is connected to the positive end of the second output filter subunit 142, and the negative end of the second output filter subunit 142 is connected between the negative end of the first voltage conversion subunit 131 and the first switch control subunit 134.

[0053] In this embodiment, the connection sequence between the positive and negative terminals of each unit and each sub-unit can be determined through simulation.

[0054] Below, taking a specific circuit diagram as an example, the principle of preventing voltage oscillation and reducing EMI problems of the DC converter of the present application is explained. At the same time, it is proved that the DC converter of the present application has higher gain and lower voltage and current stress.

[0055] like Figure 3 As shown, Vin represents the input side 170, Vo represents the load side 180, S1 represents the active switch subunit 210 of the first active switch inductor unit 110, L1 represents the inductor subunit 220 of the first active switch inductor unit 110, S2 represents the active switch subunit 210 of the second active switch inductor unit 120, L2 represents the inductor subunit 220 of the second active switch inductor unit 120, C1, C2, C3 represent the first voltage conversion subunit 131, the second voltage conversion subunit 132, and the third voltage conversion subunit 133, respectively, D1, D2, D3 represent the first switch control subunit 134, the second switch control subunit 135, and the third switch control subunit 136, respectively, D o1 , D o2 They represent the first clamping control unit 150 and the second clamping control unit 160, respectively.o1 and C o2 They represent the first output filtering subunit 141 and the second output filtering subunit 142 respectively.

[0056] It should be noted that for Vin, Vo, S1, L1, S2, L2, C1, C2, C3, D1, D2, D3, D o1 , D o2 , C o1 and C o2 , taking C1 as an example, C1 Figure 3 However, the first voltage conversion subunit 131 is not limited to only include one capacitor. The first voltage conversion subunit 131 may include multiple capacitors, or a circuit module or integrated unit including other components, which can realize the voltage conversion function.

[0057] Figure 4 For Figure 3 The corresponding clamping circuit of S1, Figure 5 is with Figure 3 The corresponding clamping circuit of S2. Figure 4 and Figure 5 It proves that the DC converter provided in this application has the function of solving voltage oscillation.

[0058] Figure 4 In, C dS1 represents the parasitic capacitance of S1, Figure 5 Middle C dS2 represents the parasitic capacitance of S2. According to Kirchhoff Voltage Laws (KVL), Figure 4 and Figure 5 It can be seen that the parasitic capacitance voltage of S1 and S2 can be expressed as: Formula 1 And, according to KVL, whether L1 and L2 are equal or not, when S1 and S2 are turned on and off, the voltage on L1 and L2 is: Formula 2 Among them, V L1,ModeI It indicates the voltage of L1 when S1 and S2 are turned on; V L1,ModeII It indicates the voltage of L1 when S1 and S2 are turned off; V L2,ModeI It indicates the voltage of L2 when S1 and S2 are turned on; V L2,ModeII It represents the voltage of L2 when S1 and S2 are turned off.

[0059] According to the volt-second balance principle, we can further deduce formula 3: Formula 3 Where d represents the duty cycle of the DC converter.

[0060] According to formula 3, we get formula 4: Formula 4 because Figure 3 C1, C2, C3, C o1 and C o2 The voltage on S1 is constant, so, combining Formula 1 and Formula 4, we can see that the voltages of S1 and S2 are equal and constant. In addition, the voltages of L1 and L2 can be expressed as: Formula 5 It can be seen from Formula 5 that the voltages of L1 and L2 are equal and constant, so no resonance occurs between S1 and L1, and between S2 and L2, and the actual voltage stress of S1 and S2 is equal to the theoretical voltage stress value.

[0061] Figure 3 S1 and S2 are turned on and off at the same time. Figure 6 is with Figure 3 The corresponding equivalent circuit diagram when both S1 and S2 are turned on (i.e. Mode I) is: Figure 7 is with Figure 3 The corresponding equivalent circuit diagram when both S1 and S2 are turned off (i.e. Mode II) is: Figure 8 In one cycle provided by an embodiment of the present application Figure 3 The waveform diagram of the DC converter is shown.

[0062] according to Figure 6 and Figure 7 It is proved that the DC converter provided by the present application has higher gain and lower voltage and current stress than some DC converters in the technology.

[0063] refer to Figure 8 , in a cycle T (0-t2), at t0, S1 and S2 are turned on at the same time, and we get Figure 6 ; At t1, S1 and S2 are turned off at the same time, and we get Figure 7 , that is, t0-t1 is ModeI, and t1-t2 is ModeII.

[0064] For Mode I, at t0, S1 and S2 are turned on at the same time, and Vin charges L1 and L2. At this time, according to the simulation, D2 and D o1 and D o2 is in reverse bias, while D1 and D3 are in forward bias. Vin charges C1 through S1, S2, and D1. In addition, Vin and C2 charge C3 through S1, S2, and D3.O1 and C O2 The energy stored in is released to the load Ro. According to KVL, the following relationship can be obtained: Formula 6 For Mode II, at t1, S1 and S2 are turned off at the same time. According to the simulation, D1 and D3 are in the reverse bias state, and D2, D o1 and D o2 In the forward bias state. At this time, Vin, L1 and L2 charge C2 through D2. o1 and D o2 C o1 and C o2 Charging, C1 and C3 discharge, while releasing part of the energy to the load Ro. According to KVL, the following relationship can be obtained: Formula 7 According to formula 6 and formula 7, formula 8 can be obtained: Formula 8 For the DC converter provided in the present application, it is deduced by the volt-second balance principle of L1 and L2, that is, according to Formula 6-Formula 8, in Mode I and Mode II, the voltages of L1 and L2 are equal, both of which are: Formula 9 According to the volt-second balance principle, we can get: Formula 10 Therefore, the gain of the DC converter provided in this application can be expressed as: Formula 11 The gain of the DC converter in the prior art is generally: Formula 12 Comparing Formula 11 and Formula 12, the gain of the DC converter provided in the present application is higher.

[0065] Regarding voltage stress, it should be noted first that when comparing the voltage stress of the DC converter provided in the present application with that of some DC converters in the prior art, the comparison needs to be made under the same conditions.

[0066] According to formula 8 and formula 12, C1, C2, C3, C o1 and C o2 Voltage stress: Formula 13 and S1, S2, D1, D2, D3, D o1 , Do2 Voltage stress: Formula 14 The voltage stress of some DC converters in the prior art is: Formula 15 It can be seen from Formula 13 to Formula 15 that, under the condition of the same gain, the DC converter provided in the present application has lower voltage stress.

[0067] For current stress, according to the charge balance principle of capacitors, the integral of the current of all capacitors in one cycle is equal to zero. According to Kirchhoff's Current Law (KCL), Figure 3 D1, D2, D3, D o1 and D o2 The average current Io is: Formula 16 In Mode I, D2, D o1 and D o2 In the reverse bias state, in each cycle T, only D1 and D3 are turned on during the dT time. Therefore, in Mode I, according to KCL, D1, D3 and C1, C2, C3, C o1 , C o2 The average current can be derived as follows: Formula 17 In Mode II, D1 and D3 are in reverse bias state, while D2, D o1 and D o2 In the forward bias state, the conduction time is (1-dT). Therefore, in Mode II, D2, D o1 , D o2 and C1, C2, C3, C o1 , C o2 The average current is: Formula 18 The average current of L1 and L2 can be expressed as: Formula 19 The average current of S1 and S2 can be expressed as: Formula 20 Figure 3 The current stress I of each device RMS It can be obtained by adding the square sum of the average current in Mode I and Mode II and integrating them. The calculation formula is: Formula 21 Therefore, the expressions for the current stress of S1 and S2 are: Formula 22 The expression of the current stress of D1 and D3 is: Formula 23 D2, D O1 , D O2 The current stress expression is: Formula 24 In order to compare the current stress, the current stress, Io and M can be established. CCM According to the average current expression and RMS current expression of each device in the two modes, it can be observed that the average current of the device is positively correlated with its RMS value. Therefore, for the convenience of comparison, the average current value can be used instead of the RMS value to evaluate the current stress of the device. Therefore, the average current, Io and M of the device CCM The relationship between them is: Formula 25 The current stress of some DC converters in the prior art is: Formula 26 It can be seen from Formula 25 and Formula 26 that, under the same gain condition, the DC converter provided in the present application has lower current stress.

[0068] The DC converter provided in the present application is generally used in situations where the gain is greater than 10. When the duty cycle d of the DC converter is 0.85-0.9, that is, when the gain is 40, the devices in the DC converter (for example, active switching tubes, diodes) have lower voltage and current stress and smaller inductor current stress. For example, in photovoltaic power generation, a low voltage of 10V is boosted to a high voltage of 400V and incorporated into the bus.

[0069] For L1 and L2, the selection method is: According to the above, the ripple expression of the inductance corresponding to L1 and L2 is: Formula 27 in, f s Indicates the switching frequency of the DC converter.

[0070] The inductor current ripple ratio is defined as δ iL ,in δ iL =Δ i L / IL According to Formula 6, the expression for selecting the inductance values ​​of L1 and L2 can be expressed as: Formula 28 For C1, C2, C3, C o1 and C o2 , and the corresponding capacitance ripples are: Formula 29 Wherein, the voltage ripple ratio of the capacitor is defined as δ vc =Δ v c / V c , then the corresponding capacitance value selection expression can be expressed as: Formula 30 Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A DC converter, characterized in that: include: A first active switching inductor unit, a second active switching inductor unit, a voltage conversion unit, an output filtering unit, a first clamping control unit, and a second clamping control unit; The first active switching inductor unit and the second active switching inductor unit are connected in parallel at two ends of the input side, the output filter unit is connected at two ends of the load side, the negative end of the input side is connected to point A of the output filter unit, the point A is an internal point of the output filter unit, and the point A divides the output filter unit into a first output filter sub-unit and a second output filter sub-unit; The first active switch inductor unit and the second active switch inductor unit are both connected to the voltage conversion unit, the voltage conversion unit is connected to the first output filter subunit through the first clamp control unit, and the voltage conversion unit is also connected to the second output filter subunit through the second clamp control unit; The first active switching inductor unit, the voltage conversion unit, the first clamping control unit and the first output filtering subunit constitute a first clamping loop, and the second active switching inductor unit, the voltage conversion unit, the second clamping control unit and the second output filtering subunit constitute a second clamping loop.

2. The DC converter according to claim 1, characterized in that: The first active switch inductor unit and the second active switch inductor unit both include: an active switch sub-unit and an inductor sub-unit; One end of the voltage conversion unit is connected between the active switch subunit and the inductor subunit in the first active switch inductor unit, and the other end of the voltage conversion unit is connected between the active switch subunit and the inductor subunit in the second active switch inductor unit.

3. The DC converter according to claim 1, characterized in that: The point A is the midpoint of the output filter unit, so that the first output filter subunit and the second output filter subunit have the same structure.

4. The DC converter according to any one of claims 1 to 3, characterized in that: The voltage conversion unit comprises: a first voltage conversion subunit, a second voltage conversion subunit, a third voltage conversion subunit and a first switch control subunit, a second switch control subunit, and a third switch control subunit; One end of the first switch control subunit, the second switch control subunit and the third voltage conversion subunit is connected to the first active switch inductor unit, the other end of the first switch control subunit is connected to one end of the first voltage conversion subunit and the second output filter subunit, the other end of the first voltage conversion subunit and one end of the second voltage conversion subunit are connected to the second active switch inductor unit, the other end of the second switch control subunit and one end of the third switch control subunit are connected to the other end of the second voltage conversion subunit, and the other end of the third switch control subunit is connected between the other end of the third voltage conversion subunit and the first output filter subunit; The first active switching inductor unit, the third voltage conversion subunit, the first clamping control unit and the first output filtering subunit constitute the first clamping loop, and the second active switching inductor unit, the input side, the first voltage conversion subunit, the second clamping control unit and the second output filtering subunit constitute the second clamping loop.

5. The DC converter according to claim 4, characterized in that: The first voltage conversion subunit, the second voltage conversion subunit, and the third voltage conversion subunit all include capacitors.

6. The DC converter according to claim 4, characterized in that: One end of the first voltage conversion subunit, one end of the second voltage conversion subunit, and one end of the third voltage conversion subunit are all positive ends; The other end of the first voltage conversion subunit, the other end of the second voltage conversion subunit, and the other end of the third voltage conversion subunit are all negative ends.

7. The DC converter according to claim 4, characterized in that: The first switch control subunit, the second switch control subunit, and the third switch control subunit all include a first semiconductor switch tube, and the first semiconductor switch tube includes at least one of the following: a diode, a MOS tube, an IGBT, and a SiC switch tube.

8. The DC converter according to claim 2, characterized in that: The active switch subunit includes a second semiconductor switch tube, and the second semiconductor switch tube includes at least one of the following: a MOS tube, an IGBT, and a SiC switch tube.

9. The DC converter according to claim 1, characterized in that: The first clamping control unit and the second clamping control unit each include at least one of the following: a diode, a MOS tube, an IGBT, and a SiC switch tube.

10. The DC converter according to any one of claims 1 to 9, characterized in that: The gain of the DC converter is: in, represents the gain of the DC converter; d represents the duty cycle of the DC converter.

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