Planar transformer and switching power supply

Abstract

The application discloses a planar transformer and a switching power supply. The planar transformer comprises a primary coil, a plurality of groups of secondary coils, a PCB and a magnetic core. The primary coil comprises a first sub-primary coil and a second sub-primary coil. The PCB is provided with a through hole in the center. The magnetic core is arranged in the through hole. The PCB comprises sixteen sub-boards. Two sub-boards on the top layer of the PCB are used for winding the first sub-primary coil, two sub-boards on the bottom layer of the PCB are used for winding the second sub-primary coil, and twelve sub-boards in the middle of the PCB are used for winding the plurality of groups of secondary coils. The planar transformer provided by the application can reduce the volume of the transformer, thereby reducing the loss of the transformer.

Description

Technical Field

[0001] This invention relates to the field of transformer technology, and more particularly to a planar transformer and a switching power supply. Background Technology

[0002] In related technologies, transformers in switching power supplies are mainly cubic in shape. This type of transformer is limited by the volume of the magnetic core, which prevents the overall size of the transformer from being reduced, thereby increasing the transformer's losses. Summary of the Invention

[0003] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a planar transformer that can reduce the size of the transformer, thereby reducing transformer losses.

[0004] The present invention also proposes a switching power supply having the above-mentioned planar transformer.

[0005] According to a first aspect of the present invention, a planar transformer includes: a primary coil, the primary coil including a first sub-primary coil and a second sub-primary coil; multiple sets of secondary coils; a PCB, the PCB having a through hole at its center; a magnetic core, the magnetic core passing through the through hole; wherein the PCB includes sixteen layers of sub-boards; the top two layers of the PCB are used to wind the first sub-primary coil, the bottom two layers of the PCB are used to wind the second sub-primary coil, and the middle twelve layers of the PCB are used to wind the multiple sets of secondary coils.

[0006] The planar transformer according to the embodiments of the present invention has at least the following beneficial effects: the planar transformer uses a PCB to replace the transformer skeleton in the related technology, uses coils on the PCB to replace the winding wires in the related technology, and is matched with a magnetic core, which can reduce the height and volume of the transformer, thereby reducing the transformer loss.

[0007] According to some embodiments of the present invention, each set of secondary side coils is wound on two layers of the sub-plate.

[0008] According to some embodiments of the present invention, the plurality of secondary coils include a set of feedback coils; the feedback coils are wound on the seventh and eighth sub-plates, and the winding direction of the feedback coils is opposite to the winding direction of the primary coils.

[0009] According to some embodiments of the present invention, the winding directions of the multiple sets of secondary coils are the same.

[0010] According to some embodiments of the present invention, the primary coil and the plurality of secondary coils are flat.

[0011] A switching power supply according to a second aspect of the present invention includes: a planar transformer as described in the first aspect; a rectifier module for connection to mains power; a filter module, one end of which is connected to the rectifier module and the other end of which is connected to one end of the primary winding; a sampling module, one end of which is connected to a set of secondary windings and is used to sample the output voltage of the secondary windings; an isolation module, one end of which is connected to the other end of the sampling module; a control module, one end of which is connected to the other end of the isolation module; and a switching module, one end of which is connected to the other end of the control module and the other end of which is connected to the other end of the primary winding; wherein the control module is used to control the conduction state of the switching module according to the output voltage.

[0012] According to some embodiments of the present invention, the plurality of secondary coils include a set of feedback coils; the sampling module is connected to the feedback coils.

[0013] According to some embodiments of the present invention, the switching module includes a MOS transistor, the gate of which is connected to the control module, the source of which is grounded, and the drain of which is connected to the other end of the primary coil.

[0014] According to some embodiments of the present invention, the isolation module includes an optical coupler, the input end of which is connected to the sampling module, and the output end of which is connected to the control module.

[0015] According to some embodiments of the present invention, it further includes: an auxiliary power supply module, the auxiliary power supply module being connected to the control module, the auxiliary power supply module being used to provide operating power to the control module.

[0016] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0018] Figure 1 This is a schematic diagram of a planar transformer according to an embodiment of the present invention;

[0019] Figure 2 This is a circuit diagram of a switching power supply according to an embodiment of the present invention;

[0020] Figure 3 This is another circuit diagram of the switching power supply according to an embodiment of the present invention.

[0021] Figure label:

[0022] Planar transformer 100, rectifier module 200, mains power 300, filter module 400, sampling module 500, isolation module 600, control module 700, switch module 800, auxiliary power supply module 900. Detailed Implementation

[0023] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0024] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0025] In the description of this invention, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0026] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0027] In the description of this invention, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0028] In related technologies, the transformers for switching power supplies are mainly cubic in shape. This type of transformer is limited by the volume of the magnetic core, thus preventing adjustments to the size of both the transformer and the switching power supply. Secondly, since the transformer is wound with enameled wire, high-voltage discharge and wire aging affect its insulation. Furthermore, due to the skin effect of current in the conductor, charge is distributed on the surface of the conductor, leading to an increase in the transformer's equivalent resistance, thereby reducing coil utilization and increasing coil losses.

[0029] Based on this, embodiments of this application provide a planar transformer and a switching power supply, which can reduce the size of the transformer and, to a certain extent, reduce the impact of the skin effect on the transformer, thereby reducing coil losses.

[0030] Reference Figure 1 This application provides a planar transformer 100. The planar transformer 100 includes a primary coil, multiple sets of secondary coils, a PCB, and a magnetic core. The primary coil includes a first sub-primary coil and a second sub-primary coil; the PCB includes sixteen layers; the top two layers of the PCB are used to wind the first sub-primary coil, the bottom two layers of the PCB are used to wind the second sub-primary coil, and the middle twelve layers of the PCB are used to wind the multiple sets of secondary coils.

[0031] Specifically, this application provides a PCB-based planar transformer 100, which includes a first primary coil (i.e., a coil composed of pins 1 and 2), a second primary coil (i.e., a coil composed of pins 2 and 3), and secondary coils. The PCB comprises multiple layers, with the outermost two layers (the top two layers and the bottom two layers) used to wind half of the primary coil, and the middle layers used to wind the secondary coil, thus forming a "sandwich" transformer where the primary coil sandwiches the secondary coil. This reduces leakage inductance and ensures the performance of the switching power supply using the planar transformer 100. For example, the PCB may include sixteen layers, each with a through-hole at its center, through which a magnetic core passes. The first and second layers are used to wind the first primary coil, the fifteenth and sixteenth layers to wind the second primary coil, and the third to fourteenth layers to wind multiple sets of secondary coils. It is understood that a PCB can be composed of a single sub-PCB comprising sixteen layers, or it can be composed of multiple sub-PCBs, such as two sub-PCBs, one of which comprises four layers and the other comprises twelve layers. This application does not specifically limit the specific composition of the PCB.

[0032] The planar transformer 100 provided in this application uses a PCB to replace the transformer skeleton in related technologies, and uses coils on the PCB to replace the winding wires in related technologies. With the help of a matching magnetic core, the height and volume of the transformer can be reduced, thereby reducing the transformer loss.

[0033] In some embodiments, each set of secondary coils is wound on two sub-boards. Specifically, the twelve sub-boards in the middle of the PCB are grouped, with two adjacent sub-boards forming a sub-board group, and each sub-board group is used to wind a set of secondary coils. That is, the planar transformer 100 provided in this application embodiment includes six sets of secondary coils (i.e., coils composed of pins 5 and 6, pins 7 and 8, pins 8 and 9, pins 16 and 15, pins 15 and 14, and pins 13 and 12), and one set of secondary coils is wound on two sub-boards in the middle of the PCB.

[0034] Furthermore, the multiple sets of secondary coils include a set of feedback coils wound on the seventh and eighth sub-boards. The winding direction of the feedback coil is opposite to that of the primary coils, while the winding directions of the multiple sets of secondary coils are the same. Specifically, the six sets of secondary coils include a set of feedback coils, and the winding directions of all six sets of secondary coils are opposite to those of the primary coils.

[0035] For example, refer to Figure 1 The first and second sub-plates are used to wind the first primary coil (i.e., the coil consisting of pins 1 and 2). Pin 1 is wound clockwise from the outermost coil to the innermost coil on the first sub-plate, and then extends from the innermost through-hole of the first sub-plate to the second sub-plate. In the second sub-plate, pin 1 is wound clockwise from the innermost coil to the outermost coil until it reaches pin 2.

[0036] The fifteenth and sixteenth sub-boards are used to wind the second primary coil (i.e., the coil consisting of pins 2 and 3). Pin 2 is wound clockwise from the outermost coil inwards on the fifteenth sub-board, extending from the innermost coil through the inner hole of the fifteenth sub-board to the sixteenth sub-board. On the sixteenth sub-board, pin 2 is wound clockwise from the innermost coil to the outermost coil until pin 3 is reached. Thus, the first, second, fifteenth, and sixteenth sub-boards form a set of primary coils.

[0037] Reference Figure 1The seventh and eighth sub-boards are used to wind the feedback coil consisting of pins 15 and 16. Pins 16 and 1 are opposite terminals, so the winding direction of pin 16 is opposite to that of pin 1. Specifically, pin 16 is wound counterclockwise from the outermost coil to the innermost coil on the seventh sub-board, extending from the innermost through-hole of the seventh sub-board to the eighth sub-board. On the eighth sub-board, pin 16 is wound counterclockwise from the innermost coil to the outermost coil until it reaches pin 16. Since pins 15 and 16 are the feedback coil, the turns ratio of the feedback coil to the primary coil determines the output voltage of the secondary coil and the reflected voltage coupled to the primary coil. Furthermore, this feedback winding is coupled to the other five sets of secondary coils; therefore, placing the feedback coil on the middle sub-board of the PCB enhances the coupling effect between the secondary coils.

[0038] The third and fourth sub-boards are used to wind a set of secondary coils consisting of pins 12 and 13. The output power of this set of secondary coils depends on the turns ratio of this set of secondary coils to the feedback coil. Pins 13 and 16 are terminals of the same name, therefore the winding direction of pin 13 is the same as that of pin 16. Specifically, pin 13 is wound counterclockwise from the outermost coil inwards on the third sub-board, extending from the innermost coil through-hole on the third sub-board to the fourth sub-board. In the fourth sub-board, pin 13 is wound counterclockwise from the innermost coil to the outermost coil until it reaches pin 12.

[0039] The fifth and sixth sub-boards are used to wind a set of secondary coils consisting of pins 14 and 15. The output power of this set of secondary coils depends on the turns ratio of this set of secondary coils to the feedback coil. Pins 15 and 16 are terminals of the same name, therefore the winding direction of pin 15 is the same as that of pin 16. Specifically, pin 15 is wound counterclockwise from the outermost coil inwards on the fifth sub-board, extending from the innermost coil through-hole on the fifth sub-board to the sixth sub-board. In the sixth sub-board, pin 15 is wound counterclockwise from the innermost coil to the outermost coil until it reaches pin 14.

[0040] The ninth and tenth sub-boards are used to wind a set of secondary coils consisting of pins 5 and 6. The output power of this set of secondary coils depends on the turns ratio of this set of secondary coils to the feedback coil. Pins 6 and 16 are terminals of the same name, therefore the winding direction of pin 6 is the same as that of pin 16. Specifically, pin 6 is wound counterclockwise from the outermost coil inwards on the ninth sub-board, extending from the innermost coil through-hole on the ninth sub-board to the tenth sub-board. On the tenth sub-board, pin 6 is wound counterclockwise from the innermost coil to the outermost coil until it reaches pin 5.

[0041] The eleventh and twelfth sub-boards are used to wind a set of secondary coils consisting of pins 7 and 8. The output power of this set of secondary coils depends on the turns ratio of this set of secondary coils to the feedback coil. Pins 8 and 16 are terminals of the same name, therefore the winding direction of pin 8 is the same as that of pin 16. Specifically, pin 8 is wound counterclockwise from the outermost coil inwards on the eleventh sub-board, extending from the innermost coil through-hole on the eleventh sub-board to the twelfth sub-board. On the twelfth sub-board, pin 8 is wound counterclockwise from the innermost coil to the outermost coil until it reaches pin 7.

[0042] The thirteenth and fourteenth sub-boards are used to wind a set of secondary coils consisting of pins 8 and 9. The output power of this set of secondary coils depends on the turns ratio of this set of secondary coils to the feedback coil. Pins 9 and 16 are terminals of the same name, therefore the winding direction of pin 9 is the same as that of pin 16. Specifically, pin 9 is wound counterclockwise from the outermost coil inwards on the thirteenth sub-board, extending from the innermost coil through-hole on the thirteenth sub-board to the fourteenth sub-board. On the fourteenth sub-board, pin 9 is wound counterclockwise from the innermost coil to the outermost coil until it reaches pin 8.

[0043] In some embodiments, both the primary coil and multiple sets of secondary coils are flat copper wires to reduce the size of the transformer and, to some extent, weaken the skin effect of the conductor, thereby reducing transformer losses. Secondly, the planar transformer 100 of this application embodiment does not use enameled wire as in related technologies; therefore, the planar transformer 100 provided in this application embodiment improves the transformer's insulation performance and alleviates the line aging problem caused by enameled wire.

[0044] Reference Figure 2 This application also provides a switching power supply. The switching power supply includes a planar transformer 100, a rectifier module 200, a filter module 400, a sampling module 500, an isolation module 600, a control module 700, and a switching module 800 as described in any of the above embodiments. The rectifier module 200 is connected to the mains power 300; one end of the filter module 400 is connected to the rectifier module 200, and the other end of the filter module 400 is connected to one end of the primary winding; one end of the sampling module 500 is connected to a set of secondary windings, and the sampling module 500 is used to sample the output voltage of the secondary windings; one end of the isolation module 600 is connected to the other end of the sampling module 500; one end of the control module 700 is connected to the other end of the isolation module 600; one end of the switching module 800 is connected to the other end of the control module 700, and the other end of the switching module 800 is connected to the other end of the primary winding. The control module 700 is used to control the conduction state of the switching module 800 according to the output voltage.

[0045] Specifically, the rectifier module 200 rectifies the single-phase AC voltage provided by the mains power 300 to form a pulsating DC voltage. Then, the filter module 400 filters this pulsating DC voltage to form a stable DC voltage. This stable DC voltage is input to the primary winding of the planar transformer 100, where the primary winding serves as the high-voltage input terminal, and the six sets of secondary windings of the planar transformer 100 serve as the isolated low-voltage output terminals. The sampling module 500 samples the output voltage of one set of secondary windings as the main output. This output voltage flows through the isolation module 600 and is then input to the control module 700. The control module 700 controls the switching module 800 to turn on or off based on the magnitude of this output voltage, thereby forming a closed-loop control of the planar transformer 100 and ensuring the stability of the output voltage of the planar transformer 100.

[0046] In some embodiments, the secondary coil connected to the sampling module 500 is a feedback coil disposed on the seventh and eighth layers of the PCB.

[0047] In some embodiments, refer to Figure 3 The switching module 800 includes a MOSFET Q1, whose gate is connected to the control module 700, whose source is grounded, and whose drain is connected to the other end of the primary winding. Specifically, the filtering module 400 includes a capacitor C1, which and the gate of the MOSFET Q1 are respectively connected to the two ends of the primary winding. The control module 700 compares the output voltage of the feedback coil with a preset voltage, and controls the conduction state of the MOSFET Q1 based on the comparison deviation, thereby controlling the input voltage of the planar transformer 100, and thus achieving closed-loop control of the output voltage of the planar transformer 100.

[0048] In some embodiments, the isolation module 600 includes an optical coupler, the input of which is connected to the sampling module 500, and the output of which is connected to the control module 700. The optical coupler isolates the output voltage sampled by the sampling module 500 to prevent interference from external signals.

[0049] In some embodiments, the switching power supply further includes an auxiliary power supply module 900, which is connected to the control module 700 and provides operating power to the control module 700. Specifically, the auxiliary power supply module 900 can implement remote soft start to protect the circuit of the control module 700 and provide the operating power required by the control module 700.

[0050] The switching power supply provided in this application embodiment can achieve multiple outputs. In multiple outputs, each output affects the other outputs, thus worsening the load regulation of the switching power supply. In related technologies, the transformer of a multi-output switching power supply is a bobbin winding type. This type of switching power supply is affected by transformer winding defects, resulting in poor cross-regulation. However, the switching power supply in this application embodiment uses a planar transformer 100, which makes the coupling between the outputs tighter, thereby achieving a better load cross-regulation and improving the overall performance of the switching power supply.

[0051] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A planar transformer, characterized in that, include: The primary coil includes a first sub-primary coil and a second sub-primary coil; Multiple sets of secondary coils, wherein the winding direction of the multiple sets of secondary coils is the same; PCB, wherein a through hole is provided in the center of the PCB; A magnetic core, which passes through the through hole; The PCB includes sixteen sub-boards. The top two sub-boards of the PCB are used to wind the first primary side coil, the bottom two sub-boards of the PCB are used to wind the second primary side coil, and the middle twelve sub-boards of the PCB are used to wind multiple sets of secondary side coils. The twelve sub-boards in the middle of the PCB are grouped together, and two adjacent sub-boards are divided into a sub-board group. Each sub-board group is used to wind a set of secondary side coils. The multiple sets of secondary coils include a set of feedback coils, which are wound on the seventh and eighth sub-boards, and the winding direction of the feedback coils is opposite to that of the primary coils.

2. The planar transformer according to claim 1, characterized in that, Each set of secondary side coils is wound on two layers of the sub-plate.

3. The planar transformer according to claim 1, characterized in that, The primary coil and the multiple sets of secondary coils are flat.

4. A switching power supply, characterized in that, include: The planar transformer as described in any one of claims 1 to 3; The rectifier module is used to connect to the mains power supply; A filtering module, one end of which is connected to the rectifier module, and the other end of which is connected to one end of the primary coil; A sampling module, one end of which is connected to a set of secondary coils, is used to sample the output voltage of the secondary coils; An isolation module, one end of which is connected to the other end of the sampling module; A control module, one end of which is connected to the other end of the isolation module; A switching module, one end of which is connected to the other end of the control module, and the other end of which is connected to the other end of the primary coil; The control module is used to control the conduction state of the switching module according to the output voltage.

5. The switching power supply according to claim 4, characterized in that, The multiple sets of secondary coils include a set of feedback coils; the sampling module is connected to the feedback coil.

6. The switching power supply according to claim 5, characterized in that, The switching module includes a MOSFET, the gate of which is connected to the control module, the source of which is grounded, and the drain of which is connected to the other end of the primary coil.

7. The switching power supply according to claim 6, characterized in that, The isolation module includes an optical coupler, the input of which is connected to the sampling module, and the output of which is connected to the control module.

8. The switching power supply according to any one of claims 4 to 7, characterized in that, Also includes: An auxiliary power supply module is connected to the control module and is used to provide operating power to the control module.

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