Rectifying circuit and switching power supply

Abstract

The invention discloses a rectifier circuit and a switching power supply, the switching power supply comprises N secondary windings, N is a natural number greater than or equal to 2, the rectifier circuit comprises N rectifier bridges, the positive output end of each rectifier bridge is used for connecting the positive output end of the switching power supply, and the negative output end of each rectifier bridge is used for connecting the negative output end of the switching power supply. The negative output end of each rectifier bridge is used for connecting the negative output end of the switching power supply, the midpoint of the first bridge arm of each rectifier bridge is used for connecting one end of one secondary winding, and the midpoint of the second bridge arm is used for connecting the other end of the corresponding secondary winding; and (N-1) first-class switch tubes, wherein one first-class switch tube is connected in series between the midpoint of the second bridge arm of the previous rectifier bridge and the midpoint of the first bridge arm of the next rectifier bridge. The invention can realize the effects of reducing cost, reducing volume and increasing efficiency.

Description

Technical Field

[0001] The invention relates to output rectification of a switching power supply, and in particular to a rectification circuit and a switching power supply. Background Art

[0002] The 21st century is the era of electrical intelligence, and power electronics technology plays an important role in all aspects of life. Switching power supply is an indispensable branch of power electronics technology, and it plays an important role in various fields, including industrial control, intelligent transportation, smart grid, smart medical care, new energy, Internet of Things, communications, etc. At present, the application of switching power supply is increasingly inclined to high-power and wide-range (input / output) applications, such as charging piles. The industry's largest power charging pile has achieved a power of 900kW, and the charging power supply has also achieved a single module of 60kW. Existing charging piles need to match rechargeable batteries with different output voltage specifications. Therefore, the output voltage of the charging pile is generally wide, with 200-750Vdc, 200-1000Vdc and 50-1000Vdc, which poses a greater challenge to the charging power supply topology itself.

[0003] The switching power supply topology itself includes two parts: inverter and rectifier. If you want to achieve a wide range of input / output, the power supply must have a sufficiently large gain variation range. The existing rectifier circuits include: half-wave rectification, full-wave rectification, full-bridge rectification, three-phase half-bridge rectification, voltage doubler rectification, current doubler rectification, etc. The above rectifier circuits can only provide fixed gain rectification, and the rectifier module cannot achieve gain adjustment. Therefore, the existing switching power supply topology can only rely on the inverter part to achieve wide gain.

[0004] Figure 1 The schematic diagram of the scheme for realizing a wide gain range for an existing switching power supply including two DCDC circuits is shown in FIG. When K1 is closed and K2 and K3 are disconnected, the output rectifiers of the two DCDC circuits are connected in series; when K1 is disconnected and K2 and K3 are closed, the output rectifiers of the two DCDC circuits are connected in parallel, thereby achieving a 2-fold gain variation range of the rectifier circuit. The disadvantage of this scheme is that the three switches K1, K2, and K3 need to be made of high-current relays, and high-current relays have the following defects: high cost, large size, and limited number of switching times, which leads to the problems of high overall cost, large size, and reduced reliability of the charging power supply. Summary of the invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a rectifier circuit and a switching power supply, which can at least solve the deficiencies of the above-mentioned prior art to a certain extent.

[0006] As a first aspect of the present invention, the embodiment and technical solution of the rectifier circuit provided are as follows:

[0007] A rectifier circuit is applied to a switching power supply, the switching power supply comprising N secondary windings, wherein N is a natural number greater than or equal to 2, wherein the rectifier circuit comprises:

[0008] N rectifier bridges, the positive output end of each rectifier bridge is used to connect to the positive output end of the switching power supply, the negative output end of each rectifier bridge is used to connect to the negative output end of the switching power supply, the midpoint of the first bridge arm of each rectifier bridge is used to connect to one end of a secondary winding, and the midpoint of the second bridge arm is used to connect to the other end of the corresponding secondary winding;

[0009] (N-1) first-type switching tubes, one first-type switching tube is connected in series between the midpoint of the second bridge arm of the previous rectifier bridge and the midpoint of the first bridge arm of the next rectifier bridge.

[0010] Furthermore, according to the relationship between the midpoint potentials of the bridge arms in each rectifier bridge, the state of each first-type switch tube is configured so that the gain of the switching power supply remains unchanged or outputs an N-times gain voltage.

[0011] Furthermore, when the potential of the midpoint of the second bridge arm of the previous rectifier bridge and the midpoint of the first bridge arm of the next rectifier bridge are the same, each first-type switch tube is configured to be disconnected, so that the gain of the switching power supply remains unchanged; when the potential of the midpoint of the second bridge arm of the previous rectifier bridge and the midpoint of the first bridge arm of the next rectifier bridge are opposite, each first-type switch tube is configured to be closed, so that the switching power supply outputs an N-fold gain voltage.

[0012] Preferably, the switch tube in each rectifier bridge is a diode, a MOS tube or an IGBT.

[0013] Preferably, each first-type switch tube is a MOS tube or a relay.

[0014] Further, when N is greater than or equal to 3, a second type of switching tube is arranged between the midpoint of the second bridge arm of the first rectifier bridge and the midpoint of the first bridge arm of the last (N-2) rectifier bridge, between the midpoint of the second bridge arm of the second rectifier bridge and the midpoint of the first bridge arm of the last (N-3) rectifier bridge, and so on, between the midpoint of the second bridge arm of the (N-2)th rectifier bridge and the midpoint of the first bridge arm of the last rectifier bridge.

[0015] Preferably, each second-type switch tube is a MOS tube or a relay.

[0016] Furthermore, according to the relationship between the midpoint potentials of each bridge arm in each rectifier bridge, the states of each first-type switch tube and each second-type switch tube are configured so that the switching power supply outputs any gain voltage from 1 times to N times.

[0017] Furthermore, when N is 3 and the midpoint potential of the second bridge arm in the first rectifier circuit is opposite to the midpoint potential of the first bridge arm in the second rectifier circuit, and the midpoint potential of the second bridge arm in the first rectifier circuit is opposite to the midpoint potential of the first bridge arm in the third rectifier circuit, the first type of switch tube between the midpoint of the second bridge arm in the first rectifier circuit and the midpoint of the first bridge arm in the second rectifier circuit, and the second type of switch tube between the midpoint of the second bridge arm in the first rectifier circuit and the midpoint of the first bridge arm in the third rectifier circuit are configured to be turned on, and the first type of switch tube between the midpoint of the second bridge arm in the second rectifier circuit and the midpoint of the first bridge arm in the third rectifier circuit is configured to be turned off, so as to achieve a 2x gain voltage output by the switching power supply.

[0018] As a second aspect of the present invention, the technical solution of the embodiment of the switching power supply provided is as follows:

[0019] A switching power supply comprises N secondary windings, wherein N is a natural number greater than or equal to 2, wherein: the switching power supply comprises the rectifier circuit described in any one of the above-mentioned first aspects.

[0020] Furthermore, the transformer specification parameters corresponding to each secondary winding are consistent.

[0021] The rectifier circuit of the embodiment of the present invention has a first-type switch tube connected in series between the midpoint of the second bridge arm of the previous rectifier bridge and the midpoint of the first bridge arm of the next rectifier bridge, and can broaden the gain of the entire power module by controlling the state of the first-type switch tube, thereby having the following beneficial effects:

[0022] (1) When the switching power supply includes two rectifier bridges, the number of switching switches required to widen the gain of the switching power supply is reduced from three in the prior art to one in the present invention, thereby reducing the product cost and the product volume;

[0023] (3) When the switching power supply includes three rectifier bridges, the number of switching switches required to widen the gain of the switching power supply is three. The number of switching switches required to widen the gain of the switching power supply is the same as that of the prior art, and the cost is not increased. However, 2 times the gain voltage and 3 times the gain voltage can be achieved at the same time, thereby expanding the application scenarios of the switching power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of a solution for achieving a wide gain range for an existing switching power supply including two DCDC circuits;

[0025] Figure 2 It is a schematic diagram of the application of the rectifier circuit of the first embodiment of the present invention when the switching power supply includes two rectifier bridges;

[0026] Figure 3 This is a schematic diagram of an application of the rectifier circuit of the first embodiment of the present invention when the switching power supply includes three rectifier bridges. DETAILED DESCRIPTION

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] First embodiment

[0033] This embodiment provides a rectifier circuit, which is applied to a switching power supply. The switching power supply includes N secondary windings, where N is a natural number greater than or equal to 2. The rectifier circuit includes:

[0034] N rectifier bridges, the positive output end of each rectifier bridge is used to connect to the positive output end of the switching power supply, the negative output end of each rectifier bridge is used to connect to the negative output end of the rectifier bridge, the midpoint of the first bridge arm of each rectifier bridge is used to connect to one end of a secondary winding, and the midpoint of the second bridge arm is used to connect to the other end of the corresponding secondary winding;

[0035] (N-1) first-type switching tubes, one first-type switching tube is connected in series between the midpoint of the second bridge arm of the previous rectifier bridge and the midpoint of the first bridge arm of the next rectifier bridge.

[0036] Furthermore, according to the relationship between the midpoint potentials of the bridge arms in each rectifier bridge, the state of each first-type switch tube is configured so that the gain of the switching power supply remains unchanged or outputs an N-times gain voltage.

[0037] Furthermore, when the potential of the midpoint of the second bridge arm of the previous rectifier bridge and the midpoint of the first bridge arm of the next rectifier bridge are the same, each first-type switch tube is configured to be disconnected, so that the gain of the switching power supply remains unchanged; when the potential of the midpoint of the second bridge arm of the previous rectifier bridge and the midpoint of the first bridge arm of the next rectifier bridge are opposite, each first-type switch tube is configured to be closed, so that the switching power supply outputs an N-fold gain voltage.

[0038] Figure 2 This is a schematic diagram of the application of the rectifier circuit of the first embodiment of the present invention when the switching power supply includes two rectifier bridges. Figure 2 , where: N is 2, that is, it includes two rectifier bridges and one first-class switching tube.

[0039] The two secondary windings are a first secondary winding 101 and a second secondary winding 102; the first bridge arm of the first rectifier bridge 110 includes a diode 111 and a diode 112, and the second bridge arm of the first rectifier bridge 110 includes a diode 113 and a diode 114; the first bridge arm of the second rectifier bridge 120 includes a diode 121 and a diode 122, and the second bridge arm of the second rectifier bridge 120 includes a diode 123 and a diode 124; the positive output end of the first rectifier bridge 110 and the positive output end of the second rectifier bridge 120 are used to connect to the positive output end Vout of the switching power supply, and the first rectifier bridge 110 is connected to the positive output end Vout of the switching power supply. The negative output end of the bridge 110 and the negative output end of the second rectifier bridge 120 are used to connect the negative output end of the switching power supply (i.e., the ground end), the midpoint of the first bridge arm of the first rectifier bridge 110 is used to connect one end of the first secondary winding 101, and the midpoint of the second bridge arm is used to connect the other end of the first secondary winding 101, the midpoint of the first bridge arm of the second rectifier bridge 120 is used to connect one end of the second secondary winding 102, and the midpoint of the second bridge arm is used to connect the other end of the second secondary winding 102, and the first type of switching tube 130 is connected between the midpoint of the second bridge arm of the first rectifier bridge 110 and the midpoint of the first bridge arm of the second rectifier bridge 120.

[0040] Figure 2 When the circuit is implemented:

[0041] When the potential of the midpoint of the second bridge arm of the first rectifier bridge 110 is the same as the potential of the midpoint of the first bridge arm of the second rectifier bridge 120, the first type switch 130 is controlled to be closed, and the first secondary winding 101 and the second secondary winding 102 are in a parallel structure. At this time, the voltage between the output terminal Vout and the output ground, the voltage of the first secondary winding 101 and the voltage of the second secondary winding 102 are equal, so that the gain of the switching power supply remains unchanged;

[0042] When the potential of the middle point of the second bridge arm of the first rectifier bridge 110 is opposite to the potential of the middle point of the first bridge arm of the second rectifier bridge 120, the first type of switch tube 130 is controlled to be closed, and the current flow path is: the upper end of the first secondary winding 101 → diode 111 → output capacitor → diode 124 → second secondary winding 102 → switch tube 130 → lower end of the first secondary winding 101; or the lower end of the first secondary winding 101 → switch tube 130 → second secondary winding 102 → diode 123 → output capacitor → diode 112 → upper end of the first secondary winding 101. The first secondary winding 101 and the second secondary winding 102 are in a series structure, and the voltage between the output terminal Vout and the output ground is the sum of the voltages at both ends of the first secondary winding 101 and the second secondary winding 102, so that the switching power supply outputs a 2-fold gain voltage, and the required switching switches are reduced from three in the prior art to one in the present invention, which reduces the product cost and the product volume.

[0043] Figure 2 The switch tubes in each rectifier bridge are diodes, and as a replacement, they can also be MOS tubes or IGBTs.

[0044] Preferably, Figure 2 The first type of switch tubes are MOS pairs or relays. The reason why the first type of switch tubes are MOS pairs instead of MOS tubes is that when the first type of switch tubes are selected as MOS tubes, if the midpoint potential of the second bridge arm of the first rectifier bridge 110 is not equal to the midpoint potential of the first bridge arm of the second rectifier bridge 120, the body diode in the MOS tube may be forward-biased, resulting in the inability to achieve the application scenario where the switching power supply gain is 1. The first type of switch tube is selected as a MOS pair. Since the cathodes of the two body diodes of the MOS pair are connected together, the MOS pair completely blocks the circuit conduction in the absence of a driving voltage. Therefore, the MOS pair will only be turned on under a given driving voltage, thereby effectively avoiding this deficiency.

[0045] Further, when N is greater than or equal to 3, a second type of switching tube is arranged between the midpoint of the second bridge arm of the first rectifier bridge and the midpoint of the first bridge arm of the last (N-2) rectifier bridge, between the midpoint of the second bridge arm of the second rectifier bridge and the midpoint of the first bridge arm of the last (N-3) rectifier bridge, and so on, between the midpoint of the second bridge arm of the (N-2)th rectifier bridge and the midpoint of the first bridge arm of the last rectifier bridge.

[0046] Preferably, each second-type switch tube is a MOS tube or a relay.

[0047] Furthermore, according to the relationship between the midpoint potentials of each bridge arm in each rectifier bridge, the states of each first-type switch tube and each second-type switch tube are configured so that the switching power supply outputs any gain voltage from 1 times to N times.

[0048] Specifically, when N is 3, and the potential of the midpoint of the second bridge arm in the first rectifier circuit is opposite to the potential of the midpoint of the first bridge arm in the second rectifier circuit, the first type of switch tube between the midpoint of the second bridge arm in the first rectifier circuit and the midpoint of the first bridge arm in the second rectifier circuit, and the second type of switch tube between the midpoint of the second bridge arm in the first rectifier circuit and the midpoint of the first bridge arm in the third rectifier circuit are configured to be turned on, and the first type of switch tube between the midpoint of the second bridge arm in the second rectifier circuit and the midpoint of the first bridge arm in the third rectifier circuit is configured to be turned off, so as to realize that the switching power supply outputs a 2 times gain voltage.

[0049] Figure 3 This is a schematic diagram of an application of the rectifier circuit of the first embodiment of the present invention when the switching power supply includes three rectifier bridges. Figure 2 , wherein: N is 3, namely, it includes three rectifier bridges, and also includes two first-type switch tubes 240 and 250 , and one second-type switch tube 260 .

[0050] The three secondary windings are a first secondary winding 201, a second secondary winding 202 and a third secondary winding 203; the first bridge arm of the first rectifier bridge 210 includes a diode 211 and a diode 212, and the second bridge arm of the first rectifier bridge 210 includes a diode 213 and a diode 214; the first bridge arm of the second rectifier bridge 220 includes a diode 221 and a diode 222, and the second bridge arm of the second rectifier bridge 220 includes a diode 223 and a diode 224; the first bridge arm of the third rectifier bridge 230 includes a diode 231 and a diode 232, and the second bridge arm of the second rectifier bridge 230 includes a diode 233 and a diode 234; the positive output end of the first rectifier bridge 210, the positive output end of the second rectifier bridge 220 and the positive output end of the third rectifier bridge 230 are used to connect to the positive output end Vout of the switching power supply, and the negative output end of the first rectifier bridge 210, the negative output end of the second rectifier bridge 220 and the negative output end of the third rectifier bridge 230 are used to connect to the positive output end Vout of the switching power supply, and the negative output end of the first rectifier bridge 210, the negative output end of the second rectifier bridge 220 and the negative output end of the third rectifier bridge 230 The midpoint of the first bridge arm of the first rectifier bridge 210 is used to connect one end of the first secondary winding 201, and the midpoint of the second bridge arm is used to connect the other end of the first secondary winding 201. The midpoint of the first bridge arm of the second rectifier bridge 220 is used to connect one end of the second secondary winding 202, and the midpoint of the second bridge arm is used to connect the other end of the second secondary winding 202. The midpoint of the first bridge arm of the third rectifier bridge 230 is used to connect one end of the third secondary winding 203. The first end and the midpoint of the second bridge arm are used to connect the other end of the third secondary winding 203, the first type of switch tube 240 is connected between the midpoint of the second bridge arm of the first rectifier bridge 210 and the midpoint of the first bridge arm of the second rectifier bridge 220, the first type of switch tube 250 is connected between the midpoint of the second bridge arm of the second rectifier bridge 220 and the midpoint of the first bridge arm of the third rectifier bridge 230, and the second type of switch tube 260 is connected between the midpoint of the second bridge arm of the first rectifier bridge 210 and the midpoint of the first bridge arm of the third rectifier bridge 230.

[0051] Figure 3 When the circuit is implemented:

[0052] When the potential of the second bridge arm midpoint of the first rectifier bridge 210 is the same as the potential of the first bridge arm midpoint of the second rectifier bridge 220, and the potential of the second bridge arm midpoint of the second rectifier bridge 220 is the same as the potential of the first bridge arm midpoint of the third rectifier bridge 230, the first switch 240 and the second switch 250 are controlled to be closed, and the third switch 260 is disconnected. At this time, the first secondary winding 201, the second secondary winding 202 and the third secondary winding 203 are in a parallel structure, and the gain does not change;

[0053] When the potential of the midpoint of the second bridge arm of the first rectifier bridge 210 is opposite to the potential of the midpoint of the first bridge arm of the second rectifier bridge 220, and the potential of the midpoint of the second bridge arm of the second rectifier bridge 220 is opposite to the potential of the midpoint of the first bridge arm of the third rectifier bridge 230, the first switch 240 and the second switch 250 are controlled to be closed and the third switch 260 is opened. At this time, the current flow path is: the upper end of the first secondary winding 201 → diode 211 → output capacitor → diode 234 → third secondary winding 203 → switch tube 250 → second secondary winding 202 → switch tube 240 → lower end of the first secondary winding 201; or the lower end of the first secondary winding 201 → switch tube 240 → second secondary winding 202 → switch tube 250 → third secondary winding 203 → diode 233 → output capacitor → diode 212 → upper end of the first secondary winding 201. The first secondary winding 201, the second secondary winding 202 and the third secondary winding 203 are connected in series to achieve a 3-fold output gain change;

[0054] When the potential of the second bridge arm midpoint of the first rectifier bridge 210 is opposite to the potential of the first bridge arm midpoint of the second rectifier bridge 220, and the potential of the second bridge arm midpoint of the first rectifier bridge 210 is opposite to the potential of the first bridge arm midpoint of the third rectifier bridge 230, the first switch 240 and the third switch 260 are controlled to be closed, and the second switch 250 is disconnected. At this time, the current flow path is: the upper end of the first secondary winding 201 → diode 211 → output capacitor → diode 234 → third secondary winding 203 → switch tube 260 → lower end of the first secondary winding 201; or the lower end of the first secondary winding 201 → switch tube 260 → third secondary winding 203 → diode 233 → output capacitor → diode 212 → upper end of the first secondary winding 201. The first secondary winding 201 and the second secondary winding 202 are in a series structure, and the first secondary winding 201 and the third secondary winding 203 are in a series structure, so as to achieve a 2-fold output gain change;

[0055] In this way, through the relationship between the midpoint potentials of each bridge arm in each rectifier bridge, the states of each first-type switching tube and the second-type switching tube are configured, so that the switching power supply can output any gain voltage from 1 to 3 times, thereby broadening the gain range of the converter, being more conducive to the design of the transformer, and improving the performance of the product. Compared with the existing technology, when the number of switching switches required is the same, the application scenarios of the switching power supply can be expanded.

[0056] Second embodiment

[0057] The present embodiment provides a switching power supply, including N secondary windings, N is a natural number greater than or equal to 2, wherein: the switching power supply includes any rectifier circuit of the first embodiment. Since the switching power supply of the present embodiment includes any rectifier circuit of the first embodiment, by controlling the conduction state of the additional switch, the series-parallel state of the transformer can be switched, and the output gain of the transformer can be widened: when the switching power supply includes two rectifier bridges, the switches required for series-parallel switching are reduced from three to one, which reduces the product cost while also reducing the product volume, but achieves the effect of widening the 2-fold gain range, and ultimately achieves the effect of reducing cost, reducing volume, and increasing efficiency; when the switching power supply includes three rectifier bridges, the gain of the power supply module is wider without increasing the cost of series-parallel switching, and the change of 2-fold and 3-fold gain is achieved, and ultimately the effect of increasing efficiency with the same cost is achieved.

[0058] Furthermore, the transformer specifications and parameters corresponding to each secondary winding are consistent, ensuring gain consistency when switching between series and parallel between different windings, and preventing abnormal operation of the power supply due to inconsistent transformer specifications and parameters.

[0059] The implementation methods of the present invention are not limited to this. According to the above content, in accordance with the common technical knowledge and customary means in the field, without departing from the above basic technical ideas of the present invention, the control method of the present invention has other implementation methods; therefore, the present invention can also make other various forms of modification, replacement or change, all of which fall within the scope of protection of the present invention.

Claims

1. A rectifier circuit, applied to a switching power supply, the switching power supply comprising N secondary windings, wherein N is a natural number greater than or equal to 2, characterized in that: The rectifier circuit comprises: N rectifier bridges, the positive output end of each rectifier bridge is used to connect to the positive output end of the switching power supply, the negative output end of each rectifier bridge is used to connect to the negative output end of the switching power supply, the midpoint of the first bridge arm of each rectifier bridge is used to connect to one end of a secondary winding, and the midpoint of the second bridge arm is used to connect to the other end of the corresponding secondary winding; (N-1) first-type switching tubes, one first-type switching tube is connected in series between the midpoint of the second bridge arm of the previous rectifier bridge and the midpoint of the first bridge arm of the next rectifier bridge.

2. The rectifier circuit according to claim 1, characterized in that: According to the relationship between the midpoint potentials of the bridge arms in each rectifier bridge, the state of each first-type switch tube is configured so that the gain of the switching power supply remains unchanged or outputs an N-fold gain voltage.

3. The rectifier circuit according to claim 2, characterized in that: When the potential of the midpoint of the second bridge arm of the previous rectifier bridge and the midpoint of the first bridge arm of the next rectifier bridge are the same, each of the first-type switch tubes is configured to be disconnected, so that the gain of the switching power supply remains unchanged; When the potentials of the midpoint of the second bridge arm of the previous rectifier bridge and the midpoint of the first bridge arm of the next rectifier bridge are opposite, each of the first-type switching tubes is configured to be closed, so that the switching power supply outputs an N-fold gain voltage.

4. The rectifier circuit according to any one of claims 1 to 3, characterized in that: The switch tube in each rectifier bridge is a diode, a MOS tube or an IGBT.

5. The rectifier circuit according to any one of claims 1 to 3, characterized in that: Each of the first-type switch tubes is a MOS pair tube or a relay.

6. The rectifier circuit according to any one of claims 1 to 3, characterized in that: When N is greater than or equal to 3, a second type of switching tube is arranged between the midpoint of the second bridge arm of the first rectifier bridge and the midpoint of the first bridge arm of the last (N-2) rectifier bridge, between the midpoint of the second bridge arm of the second rectifier bridge and the midpoint of the first bridge arm of the last (N-3) rectifier bridge, ..., between the midpoint of the second bridge arm of the (N-2)th rectifier bridge and the midpoint of the first bridge arm of the last rectifier bridge, or between all or any parts thereof.

7. The rectifier circuit according to claim 6, characterized in that: Each second type of switch tube is a MOS pair tube or a relay.

8. The rectifier circuit according to claim 6, characterized in that: According to the relationship between the midpoint potentials of the bridge arms in each rectifier bridge, the states of the first-type switching tubes and the second-type switching tubes are configured so that the switching power supply outputs any gain voltage from 1 times to N times.

9. The rectifier circuit according to claim 7, characterized in that: When N is 3, the potential of the midpoint of the second bridge arm in the first rectifier circuit is opposite to the potential of the midpoint of the first bridge arm in the second rectifier circuit, and the potential of the midpoint of the second bridge arm in the first rectifier circuit is opposite to the potential of the midpoint of the first bridge arm in the third rectifier circuit, the first type of switch tube between the midpoint of the second bridge arm in the first rectifier circuit and the midpoint of the first bridge arm in the second rectifier circuit, and the second type of switch tube between the midpoint of the second bridge arm in the first rectifier circuit and the midpoint of the first bridge arm in the third rectifier circuit are configured to be turned on, and the first type of switch tube between the midpoint of the second bridge arm in the second rectifier circuit and the midpoint of the first bridge arm in the third rectifier circuit is configured to be turned off, so as to realize that the switching power supply outputs a 2 times gain voltage.

10. A switching power supply, comprising N secondary windings, wherein N is a natural number greater than or equal to 2, characterized in that: The switching power supply comprises the rectifier circuit according to any one of claims 1 to 9.

11. The switching power supply according to claim 10, characterized in that: The transformer specification parameters corresponding to each secondary winding are consistent.

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