A switching power supply circuit

Abstract

The present invention discloses a switching power supply circuit, which includes a transformer circuit, a rectifier circuit and an output circuit. The transformer circuit is electrically connected to the rectifier circuit, and the rectifier circuit is electrically connected to the output circuit. The transformer circuit includes at least two transformers, each transformer includes a primary winding and two secondary windings. In one transformer, the two secondary windings are electromagnetically induced with the primary winding. In multiple transformers, one secondary winding of all transformers is connected in series, and the other secondary windings of all transformers are connected in series. By setting in this way, when the primary winding voltages of the two transformers are not equal, or the primary winding voltage of the transformer is not equal to the secondary winding voltage, the input voltage of the rectifier circuit can be guaranteed to be equal, which solves the voltage balancing problem caused by the difference in semiconductor device or transformer manufacturing process that cannot be solved by the prior art, and can improve the applicability of the switching power supply circuit, and facilitate promotion and mass production.

Description

Technical Field

[0001] The present invention relates to the technical field of switching power supplies, and in particular to a switching power supply circuit. Background Art

[0002] When the output voltage of the switching power supply is high, the conventional rectifier diode voltage rating is insufficient to meet the technical requirements. In view of the insufficient voltage rating, the existing technology generally solves the problem of insufficient diode voltage rating by using two or more diodes in series to form a group instead of a single diode to form a rectifier bridge, or by connecting multiple rectifier bridges in series.

[0003] However, when two or more diodes are connected in series to form a group instead of a single diode to form a rectifier bridge, if the voltages borne by the two diodes are to be the same, the internal resistances of the two diodes must be the same or very close. Due to the manufacturing process of the diodes and other reasons, this method is difficult to achieve diode voltage balancing. When multiple rectifier bridge stacks are connected in series, due to the manufacturing process of the transformer and other reasons, there are the following two defects: one is that the voltages of the primary windings of the two transformers are unequal, which in turn causes uneven voltage on the secondary windings, and ultimately causes uneven voltage on the diodes of the two rectifier bridges; the other is that even if the voltages of the primary windings of the transformers are equal, when the coupling coefficients of the two transformers are different, the voltages of the secondary windings will also be unequal, which will cause uneven voltage on the diodes of the rectifier bridge.

[0004] Therefore, both methods cannot solve the voltage equalization problem when semiconductor rectifier devices are used in series. Summary of the invention

[0005] In order to solve the problem that the existing technology of using two or more diodes in series to form a group instead of a single diode to form a rectifier bridge or multiple rectifier bridge stacks in series cannot solve the voltage equalization problem when semiconductor rectifier devices are used in series due to differences in the manufacturing processes of semiconductor devices or transformers, the present invention provides a switching power supply circuit.

[0006] In order to solve the above technical problems, the present invention adopts a switching power supply circuit, the switching power supply circuit includes a transformer circuit, a rectifier circuit and an output circuit, the transformer circuit is electrically connected to the rectifier circuit, and the rectifier circuit is electrically connected to the output circuit; the transformer circuit includes at least two transformers, each of which includes a primary winding and two secondary windings; in one transformer, the two secondary windings are electromagnetically inductive with the primary winding; in a plurality of transformers, one of the secondary windings of all the transformers is connected in series, and the other secondary windings of all the transformers are connected in series;

[0007] The rectifier circuit includes two first rectifier bridges and a second rectifier bridge connected in series, the first rectifier bridge and the second rectifier bridge each include two parallel diode groups, and each diode group includes two diodes connected in series;

[0008] The output circuit includes two first output modules and second output modules connected in series, the first output module is electrically connected to the first rectifier bridge, the second output module is electrically connected to the second rectifier bridge, and the first output module and the second output module both include an inductor and a capacitor connected in series.

[0009] In one embodiment, the output circuit further includes an equivalent load resistor, and two ends of the equivalent load resistor are electrically connected to the first output module and the second output module respectively.

[0010] In one embodiment, the transformer circuit includes a transformer T1 and a transformer T2, each transformer includes a primary winding C, a secondary winding A and a secondary winding B, the secondary winding A of the transformer T1 is connected in series with the secondary winding B of the transformer T2, and the secondary winding B of the transformer T1 is connected in series with the secondary winding A of the transformer T2.

[0011] In one embodiment, one end of the secondary winding A of the transformer T1 is electrically connected between the two diodes of one of the diode groups of the first rectifier bridge, and the other end of the secondary winding A of the transformer T1 is electrically connected to one end of the secondary winding B of the transformer T2; one end of the secondary winding B of the transformer T1 is electrically connected between the two diodes of one of the diode groups of the second rectifier bridge, and the other end of the secondary winding B of the transformer T1 is electrically connected to one end of the secondary winding A of the transformer T2; the other end of the secondary winding A of the transformer T2 is electrically connected between the two diodes of another of the diode groups of the second rectifier bridge; the other end of the secondary winding B of the transformer T2 is electrically connected between the two diodes of another of the diode groups of the first rectifier bridge.

[0012] In one embodiment, the transformer circuit includes a transformer T3, a transformer T4, a transformer T5 and a transformer T6, each transformer including a primary winding C, a secondary winding A and a secondary winding B; the secondary winding A of the transformer T3, the secondary winding B of the transformer T4, the secondary winding A of the transformer T5 and the secondary winding B of the transformer T5 are connected in series, and the secondary winding B of the transformer T3, the secondary winding A of the transformer T4, the secondary winding B of the transformer T5 and the secondary winding A of the transformer T6 are connected in series.

[0013] In one embodiment, one end of the secondary winding A of the transformer T3 is electrically connected between the two diodes of one of the diode groups of the first rectifier bridge, and the other end of the secondary winding A of the transformer T3 is electrically connected to one end of the secondary winding B of the transformer T4; the other end of the secondary winding B of the transformer T4 is electrically connected to one end of the secondary winding A of the transformer T5; the other end of the secondary winding A of the transformer T5 is electrically connected to one end of the secondary winding B of the transformer T6, and the other end of the secondary winding B of the transformer T6 is electrically connected to the two diodes of another diode group of the first rectifier bridge. one end of the secondary winding B of the transformer T3 is electrically connected between the two diodes of one of the diode groups of the second rectifier bridge, and the other end of the secondary winding B of the transformer T3 is electrically connected to one end of the secondary winding A of the transformer T4; the other end of the secondary winding A of the transformer T4 is electrically connected to one end of the secondary winding B of the transformer T5; the other end of the secondary winding B of the transformer T5 is electrically connected to one end of the secondary winding A of the transformer T6, and the other end of the secondary winding A of the transformer T6 is electrically connected between the two diodes of another diode group of the second rectifier bridge.

[0014] In one embodiment, the two secondary windings of the transformer are wound in a bi-parallel manner.

[0015] In one embodiment, the two secondary windings of each transformer have the same number of turns and wire diameter.

[0016] 1. In the switching power supply circuit provided in the embodiment of the present invention, the switching power supply circuit includes a transformer circuit, a rectifier circuit and an output circuit. The transformer circuit is electrically connected to the rectifier circuit, and the rectifier circuit is electrically connected to the output circuit. The transformer circuit includes at least two transformers, each transformer includes a primary winding and two secondary windings. In one transformer, the two secondary windings are electromagnetically inductively coupled to the primary winding. In multiple transformers, one secondary winding of all transformers is connected in series, and the other secondary windings of all transformers are connected in series. Through such an arrangement, when the primary winding voltages of the two transformers are not equal, or the primary winding voltage and the secondary winding voltage of the transformer are not equal, the input voltages of the rectifier circuit can be guaranteed to be equal, which solves the problem that the existing technology cannot solve the voltage equalization problem when semiconductor rectifier devices are used in series due to differences in the manufacturing process of semiconductor devices or transformers by using two or more diodes in series as a group instead of a single diode to form a rectifier bridge or multiple rectifier bridge stacks in series. The differences in the manufacturing process of semiconductor devices or transformers can be ignored to a certain extent, thereby improving the applicability of the switching power supply circuit and facilitating promotion and mass production.

[0017] 2. In the switching power supply circuit provided in the embodiment of the present invention, the two secondary windings of the transformer are wound in a double-wire parallel winding manner. The number of turns and wire diameter of the two secondary windings of each transformer are the same, which can maximize the consistency of the coupling coefficient between the two secondary windings and the primary winding, thereby achieving voltage equalization for each diode. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying any creative work.

[0019] Figure 1 The circuit diagram of the switching power supply circuit of the prior art is shown in FIG. Figure 1 .

[0020] Figure 2 The circuit diagram of the switching power supply circuit of the prior art is shown in FIG. Figure 2 .

[0021] Figure 3 It is a schematic diagram of the structure of a switching power supply circuit provided by an embodiment of the present invention.

[0022] Figure 4 It is a schematic diagram of the structure of the transformer winding of the switching power supply circuit provided by an embodiment of the present invention.

[0023] Figure 5 Schematic diagram of a switching power supply circuit provided by an embodiment of the present invention Figure 1 .

[0024] Figure 6 Schematic diagram of a switching power supply circuit provided by an embodiment of the present invention Figure 2 .

[0025] Description of the label:

[0026] 1. Switching power supply circuit;

[0027] 11. Transformer circuit; 12. Rectifier circuit; 13. Output circuit;

[0028] 111, transformer; 121, first rectifier bridge; 122, second rectifier bridge; 131, first output module; 132, second output module; 133, equivalent load resistance. DETAILED DESCRIPTION

[0029] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. Embodiments of the present application are provided in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0031] It is understood that the terms "first", "second", "third" and "fourth" used in this application ... etc. can be used in this article to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish the first element from another element. When used here, the singular forms of "one", "an" and "said / the" may also include plural forms, unless the context clearly indicates another way. It should also be understood that the terms "include / comprise" or "have" etc. specify the existence of stated features, wholes, steps, operations, components, parts or combinations thereof, but do not exclude the possibility of the existence or addition of one or more other features, wholes, steps, operations, components, parts or combinations thereof.

[0032] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0033] In the present invention, the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inside", "outside", "middle", "vertical", "horizontal", "lateral", "longitudinal" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. These terms are mainly used to better describe the present invention and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation. Moreover, in addition to being used to indicate orientations or positional relationships, some of the above terms may also be used to express other meanings. For example, the term "upper" may also be used to indicate a certain dependency or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in the present invention can be understood according to specific circumstances.

[0034] In addition, the terms "installed", "set", "provided with", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection, or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, elements, or components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0035] See also Figure 1 and Figure 2 As shown, for ease of understanding, the embodiment of the present invention describes the switching power supply circuit in the prior art.

[0036] like Figure 1 As shown, in the prior art, two diodes are connected in series to form a diode group, and multiple diode groups are then combined into a rectifier bridge to form a switching power supply circuit. However, if the two diodes in each group are to withstand the same voltage, two diodes with the same or very close internal resistance must be selected to achieve voltage balancing. Due to the manufacturing process of the diodes and other reasons, it is difficult to achieve diode voltage balancing in the switching power supply circuit, which undoubtedly greatly increases the workload and is not convenient for promotion and mass production.

[0037] like Figure 2 As shown, the prior art connects two rectifier bridges in series to form a switching power supply circuit. Due to the manufacturing process of the transformer and other reasons, the switching power supply circuit has the following two defects: first, the voltages of the primary windings of the two transformers are not equal, which in turn causes the secondary windings to be unevenly voltageed, and ultimately causes the diodes of the two rectifier bridges to be unevenly voltageed. Second, even if the voltages of the primary windings of the transformers are equal, when the coupling coefficients of the two transformers are different, the voltages of the secondary windings will also be unequal, which in turn causes the diodes of the rectifier bridge to be unevenly voltageed.

[0038] See also Figure 3 As shown, an embodiment of the present invention provides a switching power supply circuit 1, which can solve the voltage balancing problem of the rectifier device. The switching power supply circuit 1 includes a transformer circuit 11, a rectifier circuit 12 and an output circuit 13, wherein the rectifier circuit 12 is electrically connected to the transformer circuit 11 and the output circuit 13.

[0039] Specifically, the transformer circuit 11 includes at least two transformers 111, each transformer 111 includes a primary winding and two secondary windings. In one transformer 111, the two secondary windings are electromagnetically inductively coupled to the primary winding. In multiple transformers 111, one secondary winding of all transformers is connected in series, and the other secondary windings of all transformers are connected in series.

[0040] Specifically, the rectifier circuit 12 includes two first rectifier bridges 121 and second rectifier bridges 122 connected in series. The first rectifier bridge 121 and the second rectifier bridge 122 each include two parallel diode groups, and each diode group includes two diodes connected in series.

[0041] Specifically, the output circuit 13 includes two first output modules 131 and second output modules 132 connected in series. The first output module 131 is electrically connected to the first rectifier bridge 121, and the second output module 132 is electrically connected to the second rectifier bridge 122. The first output module 131 and the second output module 132 both include inductors and capacitors connected in series.

[0042] Furthermore, the output circuit 13 further includes an equivalent load resistor 133 , and two ends of the equivalent load resistor 133 are electrically connected to the first output module 131 and the second output module 132 , respectively.

[0043] In the embodiment of the present invention, by providing an equivalent load resistor 133 on the output circuit 13 and electrically connecting the first output module 131 and the second output module 132 , the equivalent load resistor 133 can discharge the residual electricity when the power is off.

[0044] See also Figure 4 As shown, specifically, the two secondary windings of the transformer 111 are wound in a bi-parallel manner. Figure 4 As shown in the figure, the two secondary windings are defined as secondary winding A and secondary winding B, respectively, wherein the winding with diagonal lines in the figure represents the secondary winding A, and the winding with dot matrix in the figure represents the secondary winding. It can be seen that the two secondary windings are wound side by side, thereby solving the problem of inconsistent coupling coefficients of the two secondary windings to the greatest extent.

[0045] More specifically, the two secondary windings of each transformer 111 have the same number of turns and wire diameter.

[0046] In the embodiment of the present invention, the two secondary windings are wound in a biparallel manner to maximize the consistency of the coupling coefficients of the two secondary windings with the primary winding, thereby achieving voltage balancing for each diode.

[0047] In the embodiment of the present invention, through the above-mentioned setting, when the primary winding voltages of the two transformers 111 are not equal, or the primary winding voltage and the secondary winding voltage of the transformer 111 are not equal, it can ensure that the input voltages of the rectifier circuit 12 are equal, which solves the problem that the existing technology uses two or more diodes in series as a group instead of a single diode to form a rectifier bridge or multiple rectifier bridge stacks in series to solve the voltage equalization problem when semiconductor rectifier devices are used in series due to differences in the manufacturing process of semiconductor devices or transformers. To a certain extent, the differences in the manufacturing process of semiconductor devices or transformers can be ignored, thereby improving the applicability of the switching power supply circuit 1 and facilitating promotion and mass production.

[0048] See also Figure 5 As shown, as an optional implementation, the transformer circuit 11 includes a transformer T1 and a transformer T2, each transformer includes a primary winding C, a secondary winding A and a secondary winding B, the secondary winding A of the transformer T1 is connected in series with the secondary winding B of the transformer T2, and the secondary winding B of the transformer T1 is connected in series with the secondary winding A of the transformer T2.

[0049] The present invention describes the circuit principle of this embodiment.

[0050] The first rectifier bridge 121 includes a diode D1, a diode D2, a diode D3 and a diode D4, wherein the diode D1 and the diode D2 are connected in series to form a diode group, the diode D3 and the diode D4 are connected in series to form a diode group, and the two diode groups are connected in parallel. The second rectifier bridge 122 includes a diode D5, a diode D6, a diode D7 and a diode D8, wherein the diode D5 and the diode D6 are connected in series to form a diode group, the diode D7 and the diode D8 are connected in series to form a diode group, and the two diode groups are connected in parallel.

[0051] The first output module 131 includes an inductor L1 and a capacitor C1, and the inductor L1 is electrically connected to the first rectifier bridge 121 and the capacitor C1. The second output module 132 includes an inductor L2 and a capacitor C2, and the inductor L2 is electrically connected to the second rectifier bridge 122 and the capacitor C2. The capacitor C1 and the capacitor C2 are electrically connected. The equivalent load resistor 133 is a resistor R1, one end of the resistor R1 is electrically connected between the inductor L1 and the capacitor C1, and the other end of the resistor R1 is electrically connected between the inductor L2 and the capacitor C2.

[0052] One end of the secondary winding A of the transformer T1 is electrically connected between the diode D1 and the diode D2, and the other end of the secondary winding A of the transformer T1 is electrically connected to one end of the secondary winding B of the transformer T2. One end of the secondary winding B of the transformer T1 is electrically connected between the diode D5 and the diode D6, and the other end of the secondary winding B of the transformer T1 is electrically connected to one end of the secondary winding A of the transformer T2. The other end of the secondary winding A of the transformer T2 is electrically connected between the diode D7 and the diode D8. The other end of the secondary winding B of the transformer T2 is electrically connected between the diode D3 and the diode D4.

[0053] By implementing this embodiment, it is assumed that the primary winding voltages of transformer T1 and transformer T2 are not equal, namely Vp1 and Vp2, and the turns ratio is N. For the convenience of description, the coupling coefficient of transformer T1 and transformer T2 is set to 1, then the secondary winding voltage of transformer T1 is Vp1 / N, and the secondary winding voltage of transformer T2 is Vp2 / N. Therefore, in this embodiment, the input voltages of the two rectifier bridges are both (Vp1+Vp2) / N, and diode voltage balancing can obviously be achieved. It can be understood that when the coupling coefficient of transformer T1 and transformer T2 is less than 1, due to the existence of leakage inductance, the actual equivalent turns ratio will not be equal to N. Assuming that the actual turns ratios under this coupling coefficient are equivalent to N1 and N2, respectively, the input voltages of the two rectifier bridges in this embodiment are both Vp1 / N1+Vp2 / N2, and diode voltage balancing can obviously be achieved.

[0054] See also Figure 6 As shown, as another optional implementation, the transformer circuit includes a transformer T3, a transformer T4, a transformer T5 and a transformer T6, each transformer including a primary winding C, a secondary winding A and a secondary winding B. The secondary winding A of the transformer T3, the secondary winding B of the transformer T4, the secondary winding A of the transformer T5 and the secondary winding B of the transformer T5 are connected in series. The secondary winding B of the transformer T3, the secondary winding A of the transformer T4, the secondary winding B of the transformer T5 and the secondary winding A of the transformer T6 are connected in series.

[0055] The present invention describes the circuit principle of this embodiment.

[0056] The first rectifier bridge 121 includes a diode D9, a diode D10, a diode D11 and a diode D12, wherein the diode D9 and the diode D10 are connected in series to form a diode group, the diode D11 and the diode D12 are connected in series to form a diode group, and the two diode groups are connected in parallel. The second rectifier bridge 122 includes a diode D13, a diode D14, a diode D15 and a diode D16, wherein the diode D13 and the diode D14 are connected in series to form a diode group, the diode D15 and the diode D16 are connected in series to form a diode group, and the two diode groups are connected in parallel.

[0057] The first output module 131 includes an inductor L3 and a capacitor C3, and the inductor L3 is electrically connected to the first rectifier bridge 121 and the capacitor C3. The second output module 132 includes an inductor L4 and a capacitor C4, and the inductor L4 is electrically connected to the second rectifier bridge 122 and the capacitor C4. The capacitor C3 and the capacitor C4 are electrically connected again. The equivalent load resistor 133 is a resistor R2, one end of the resistor R2 is electrically connected between the inductor L3 and the capacitor C3, and the other end of the resistor R2 is electrically connected between the inductor L4 and the capacitor C4.

[0058] One end of the secondary winding A of the transformer T3 is electrically connected between the diode D9 and the diode D10, and the other end of the secondary winding A of the transformer T3 is electrically connected to one end of the secondary winding B of the transformer T4. The other end of the secondary winding B of the transformer T4 is electrically connected to one end of the secondary winding A of the transformer T5, and the other end of the secondary winding A of the transformer T5 is electrically connected to one end of the secondary winding B of the transformer T6. The other end of the secondary winding B of the transformer T6 is electrically connected between the diode D11 and the diode D12. One end of the secondary winding B of the transformer T3 is electrically connected between the diode D15 and the diode D16, and the other end of the secondary winding B of the transformer T3 is electrically connected to one end of the secondary winding A of the transformer T4. The other end of the secondary winding A of the transformer T4 is electrically connected to one end of the secondary winding B of the transformer T5, and the other end of the secondary winding B of the transformer T5 is electrically connected to one end of the secondary winding A of the transformer T6. The other end of the secondary winding A of the transformer T6 is electrically connected between the diode D13 and the diode D14 .

[0059] By implementing this embodiment, the switching power supply circuit 1 adopts a working mode of 4 transformers connected in series and 8 diodes forming 2 rectifier bridges connected in series, which can adapt to the high-voltage switching power supply with an output of 1200V, solves the problem of high withstand voltage of diodes, and solves the problem of diode voltage balancing.

[0060] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0061] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A switching power supply circuit, characterized in that: The switching power supply circuit includes a transformer circuit, a rectifier circuit and an output circuit, wherein the transformer circuit is electrically connected to the rectifier circuit, and the rectifier circuit is electrically connected to the output circuit; The transformer circuit includes at least two transformers, each of which includes a primary winding and two secondary windings; in one transformer, the two secondary windings are electromagnetically inductively coupled to the primary winding; in a plurality of transformers, one of the secondary windings of all the transformers is connected in series, and another of the secondary windings of all the transformers is connected in series; The rectifier circuit includes two first rectifier bridges and a second rectifier bridge connected in series, the first rectifier bridge and the second rectifier bridge each include two parallel diode groups, and each diode group includes two diodes connected in series; The output circuit includes two first output modules and a second output module connected in series, the first output module is electrically connected to the first rectifier bridge, the second output module is electrically connected to the second rectifier bridge, and the first output module and the second output module both include an inductor and a capacitor connected in series; The two secondary windings of the transformer are wound in a bi-parallel manner; The two secondary windings of each transformer have the same number of turns and wire diameter; The transformer circuit includes a transformer T3, a transformer T4, a transformer T5 and a transformer T6, each transformer including a primary winding C, a secondary winding A and a secondary winding B, the secondary winding A of the transformer T3, the secondary winding B of the transformer T4, the secondary winding A of the transformer T5 and the secondary winding B of the transformer T5 are connected in series, and the secondary winding B of the transformer T3, the secondary winding A of the transformer T4, the secondary winding B of the transformer T5 and the secondary winding A of the transformer T6 are connected in series.

2. The switching power supply circuit according to claim 1, characterized in that: The output circuit further includes an equivalent load resistor, and two ends of the equivalent load resistor are electrically connected to the first output module and the second output module respectively.

3. The switching power supply circuit according to claim 1, wherein: One end of the secondary winding A of the transformer T3 is electrically connected between the two diodes of one of the diode groups of the first rectifier bridge, and the other end of the secondary winding A of the transformer T3 is electrically connected to one end of the secondary winding B of the transformer T4; the other end of the secondary winding B of the transformer T4 is electrically connected to one end of the secondary winding A of the transformer T5; the other end of the secondary winding A of the transformer T5 is electrically connected to one end of the secondary winding B of the transformer T6, and the other end of the secondary winding B of the transformer T6 is electrically connected between the two diodes of another diode group of the first rectifier bridge; One end of the secondary winding B of the transformer T3 is electrically connected between the two diodes of one of the diode groups of the second rectifier bridge, and the other end of the secondary winding B of the transformer T3 is electrically connected to one end of the secondary winding A of the transformer T4; the other end of the secondary winding A of the transformer T4 is electrically connected to one end of the secondary winding B of the transformer T5; the other end of the secondary winding B of the transformer T5 is electrically connected to one end of the secondary winding A of the transformer T6, and the other end of the secondary winding A of the transformer T6 is electrically connected between the two diodes of another diode group of the second rectifier bridge.

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