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CN116844832A - Switching power supply and planar transformer thereof - Google Patents

Switching power supply and planar transformer thereof Download PDF

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Publication number
CN116844832A
CN116844832A CN202310849249.9A CN202310849249A CN116844832A CN 116844832 A CN116844832 A CN 116844832A CN 202310849249 A CN202310849249 A CN 202310849249A CN 116844832 A CN116844832 A CN 116844832A
Authority
CN
China
Prior art keywords
winding
pcb
board
planar transformer
power supply
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
CN202310849249.9A
Other languages
Chinese (zh)
Inventor
叶玮
隋晶
张彤
翟继金
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Qidong Lishengmei Integrated Circuit Co ltd
Original Assignee
Qidong Lishengmei Integrated Circuit Co ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Qidong Lishengmei Integrated Circuit Co ltd filed Critical Qidong Lishengmei Integrated Circuit Co ltd
Priority to CN202310849249.9A priority Critical patent/CN116844832A/en
Publication of CN116844832A publication Critical patent/CN116844832A/en
Pending legal-status Critical Current

Links

Classifications

    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01FMAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00Details of transformers or inductances, in general
    • H01F27/28Coils; Windings; Conductive connections
    • H01F27/29Terminals; Tapping arrangements for signal inductances
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01FMAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00Details of transformers or inductances, in general
    • H01F27/28Coils; Windings; Conductive connections
    • H01F27/2804Printed windings
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01FMAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00Details of transformers or inductances, in general
    • H01F27/28Coils; Windings; Conductive connections
    • H01F27/32Insulating of coils, windings, or parts thereof
    • H01F27/324Insulation between coil and core, between different winding sections, around the coil; Other insulation structures
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01FMAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00Details of transformers or inductances, in general
    • H01F27/33Arrangements for noise damping
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01FMAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00Details of transformers or inductances, in general
    • H01F27/34Special means for preventing or reducing unwanted electric or magnetic effects, e.g. no-load losses, reactive currents, harmonics, oscillations, leakage fields
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01FMAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00Details of transformers or inductances, in general
    • H01F27/34Special means for preventing or reducing unwanted electric or magnetic effects, e.g. no-load losses, reactive currents, harmonics, oscillations, leakage fields
    • H01F27/36Electric or magnetic shields or screens
    • HELECTRICITY
    • H05ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05KPRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K1/00Printed circuits
    • H05K1/02Details
    • HELECTRICITY
    • H05ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05KPRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K1/00Printed circuits
    • H05K1/02Details
    • H05K1/0296Conductive pattern lay-out details not covered by sub groups H05K1/02 - H05K1/0295
    • H05K1/0298Multilayer circuits
    • HELECTRICITY
    • H05ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05KPRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K1/00Printed circuits
    • H05K1/02Details
    • H05K1/11Printed elements for providing electric connections to or between printed circuits
    • H05K1/115Via connections; Lands around holes or via connections
    • HELECTRICITY
    • H05ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05KPRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K1/00Printed circuits
    • H05K1/16Printed circuits incorporating printed electric components, e.g. printed resistor, capacitor, inductor
    • H05K1/165Printed circuits incorporating printed electric components, e.g. printed resistor, capacitor, inductor incorporating printed inductors
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01FMAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00Details of transformers or inductances, in general
    • H01F27/28Coils; Windings; Conductive connections
    • H01F27/2804Printed windings
    • H01F2027/2809Printed windings on stacked layers
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01FMAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00Details of transformers or inductances, in general
    • H01F27/28Coils; Windings; Conductive connections
    • H01F27/2804Printed windings
    • H01F2027/2819Planar transformers with printed windings, e.g. surrounded by two cores and to be mounted on printed circuit

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Dc-Dc Converters (AREA)

Abstract

The present application provides a planar transformer comprising: the PCB winding board comprises at most four layers of PCB boards which are arranged in a stacked manner, each layer of PCB winding board is provided with a through hole, an opening penetrating through the PCB winding board is formed in the PCB winding board, and the opening is used for accommodating a center column of the magnetic core; the winding unit is arranged on the PCB winding board and comprises a primary winding and a secondary winding; the silk screen printing layer is arranged on the top surface and the bottom surface of the PCB winding board and covers the winding unit; wherein the center tap of the primary winding taps the first winding and the power supply winding connected in series, and the center tap of the secondary winding taps the second winding and the third winding connected in series. The planar transformer can meet the balance requirements of different common mode noises, has a good electromagnetic interference suppression effect, and reduces the use of peripheral EMI filter devices, thereby reducing the production cost and reducing the leakage current in a circuit.

Description

Switching power supply and planar transformer thereof
Technical Field
The application relates to the technical field of power supplies, in particular to a switching power supply and a planar transformer thereof.
Background
With the rapid development of power electronics technology, people put higher and higher requirements on the charging speed and the charging volume of a charger, namely, the charging speed is required to be higher and the charging volume is required to be smaller, wherein, increasing the working frequency of a switching power supply is an effective means for solving the charging speed and the charging volume, but the electromagnetic interference (EMI) of the switching power supply is aggravated.
The planar transformer is an indispensable basic component in the switching power supply, and the winding of the planar transformer is formed by overlapping and winding a plurality of layers of printed circuit boards, so that the planar transformer has the advantages of good consistency and low cost. The planar transformer has advantages in height and volume, and the thin structure of the conductor can reduce the influence caused by high-frequency effect so as to reduce power consumption; and the tight coupling of the primary winding and the secondary winding can reduce leakage inductance and thus loss, but can bring about larger interlayer capacitance so as to exacerbate electromagnetic interference.
In the prior art, a shielding layer is generally arranged between a primary winding layer and a secondary winding layer or is arranged between the primary winding layer or the secondary winding layer so as to reduce the influence of electromagnetic interference, but the effect of balancing conduction emission and radiation emission cannot be well achieved by adjusting the number of turns of the shielding winding on the shielding layer, so that the ideal effect of inhibiting the electromagnetic interference cannot be obtained, the development period of the back-to-back switching power supply is prolonged, and the development efficiency is reduced. When the primary winding layer or the secondary winding layer is provided with the shielding layer, more than 6 layers of PCB boards are needed, and the cost is high.
Disclosure of Invention
Therefore, the technical problem to be solved by the application is how to ensure that the planar transformer has good EMI consistency, has better electromagnetic interference inhibition effect, and reduces the cost of the planar transformer.
In order to achieve the above purpose, the present application provides the following technical solutions:
according to an aspect of the present application, there is provided a planar transformer including: the PCB winding board comprises at most four layers of PCB boards which are arranged in a stacked manner, each layer of PCB winding board is provided with a through hole, an opening penetrating through the PCB winding board is formed in the PCB winding board, and the opening is used for accommodating a center column of the magnetic core; the winding unit is arranged on the PCB winding board and comprises a primary winding and a secondary winding; the silk screen printing layer is arranged on the top surface and the bottom surface of the PCB winding board and covers the winding unit; wherein the center tap of the primary winding taps the first winding and the power supply winding connected in series, and the center tap of the secondary winding taps the second winding and the third winding connected in series.
Preferably, the number of turns of the coils of the first winding and the power supply winding is the same and the wire diameter is the same; the number of turns of the coils of the second winding and the third winding are the same and the wire diameters are the same.
Preferably, the second end of the first winding is connected to the primary ground via a first capacitor, and the first end is connected to the first end of the switching tube.
Preferably, the power supply winding includes a fourth winding and a fifth winding, the fifth winding and the first diode being connected in series.
Preferably, the first end of the fourth winding is connected to the primary ground, the second end of the fourth winding is connected to the first end of the fifth winding, and the first end of the fifth winding is connected to the second end of the fifth winding via a first diode and a second capacitor, and the second end of the fifth winding is connected to the chip ground.
Preferably, the first end of the second winding is a first end of a secondary winding, the second end of the third winding is a second end of the secondary winding, and the second end of the third winding is connected with a secondary ground.
Preferably, the first end of the third winding is connected to the second end of the second winding via a second switching tube, the positive electrode of the second switching tube is connected to the first end of the third winding, and the negative electrode of the second switching tube is connected to the second end of the second winding.
Preferably, the PCB board is made of glass fiber board or paper base material or ceramic base board or flexible board.
The application has the beneficial effects that:
according to the planar transformer provided by the embodiment of the application, the primary winding and the secondary winding are subjected to center tapping, so that the primary winding forms the first winding and the power supply winding which are connected in series, and the secondary winding forms the second winding and the third winding which are connected in series so as to mutually offset common mode noise currents from the secondary winding to the primary winding, the planar transformer can adapt to the balance requirements of different common mode noises, has a good electromagnetic interference suppression effect, and can reduce the use of peripheral EMI filter devices, thereby reducing the production cost and reducing leakage current in a circuit.
Furthermore, the planar transformer has no independent shielding or balance windings, so that the PCB winding board can be provided with four layers or less than four layers of PCB boards, and the through hole technology is adopted to connect and conduct all the board layers.
Further, the top layer and the bottom layer of the PCB winding board are respectively provided with a silk-screen printing layer to cover the winding unit so as to achieve the insulation and voltage-resistant effects.
The foregoing description is only an overview of the present application, and is intended to provide a better understanding of the present application, as it is embodied in the following description, with reference to the preferred embodiments of the present application and the accompanying drawings.
Drawings
Fig. 1 to fig. 4 are schematic top views respectively showing layers of a planar transformer according to an embodiment of the present application;
fig. 5 shows a schematic structural diagram of a planar transformer according to an embodiment of the present application;
fig. 6 shows a schematic circuit structure of a planar transformer according to an embodiment of the present application.
Detailed Description
The following describes in further detail the embodiments of the present application with reference to the drawings and examples. The following examples are illustrative of the application and are not intended to limit the scope of the application.
Fig. 1 to fig. 4 are schematic top views respectively showing layers of a planar transformer according to an embodiment of the present application; fig. 5 shows a schematic structural diagram of a planar transformer according to an embodiment of the present application. As shown in fig. 1-5, the planar transformer includes a PCB winding board, a winding unit, a silk-screen layer (not shown) and a compensation capacitor 2. In this embodiment, the PCB board 10 may be made of a glass fiber board, a paper substrate, a ceramic substrate, or a flexible board, which are conventionally known materials used in the art for manufacturing the PCB board 10, and may be selected in combination with design requirements, which is not limited in the present application.
Specifically, the PCB winding board includes at most four layers of PCB boards 10 that are stacked, each layer of PCB board 10 is provided with a through hole (not numbered), and the through hole is used for electrical conduction of the copper foil circuit on the two adjacent layers of PCB boards 10, and is a conventional arrangement, and details are not described herein. The PCB winding board is provided with an opening 1 therethrough, the opening 1 being for receiving a center post of a magnetic core (not shown).
The magnetic core includes a top magnetic core and a bottom magnetic core, and the top magnetic core and the bottom magnetic core may be configured as EE-type magnetic cores, EC-type magnetic cores, or EI-type magnetic cores, which are conventional, and the present application is not limited thereto.
In this embodiment, an EI-type core is used as an example for the top core and the bottom core, and specifically, the center pillar and the side pillar of the top core are in an E-type structure, and the side pillar of the bottom core is in an I-type structure. During installation, the center post of the E-shaped top magnetic core penetrates through the opening 1 on the PCB winding board, the side post of the E-shaped top magnetic core is arranged on the periphery of the PCB winding board in a surrounding mode, and the I-shaped bottom magnetic core is connected with the E-shaped top magnetic core to form a complete magnetic core.
The winding unit is arranged on the PCB winding board, and the planar transformer comprises a primary winding Pri and a secondary winding Sec. The silk screen printing layer sets up on the top layer and the bottom of PCB winding board, and the winding unit is covered to the silk screen printing layer. The primary winding Pri and the secondary winding Sec are enclosed on the outer periphery of the center post of the magnetic core, and in this embodiment, the winding unit is rectangular or approximately rectangular in shape on the PCB winding board.
From the foregoing, it can be seen that the PCB winding board includes at most four layers of PCB boards 10, and the number of layers of PCB boards 10 can be adjusted in combination with the arrangement structure of the winding units. The primary winding Pri and the secondary winding Sec are both arranged on one PCB board 10, or the primary winding Pri and the secondary winding are respectively arranged on different PCB boards, the arrangement mode of the winding unit is not limited to the above mode, and the winding unit can be adjusted in combination with the design requirement, and the description is omitted here.
In this embodiment, the primary winding Pri includes a first winding N1 and a power supply winding, the first winding N1 and the power supply winding are connected in series, and a first end of a switching tube Q1 is connected to a node between the first winding N1 and the power supply winding; the secondary winding Sec includes a second winding N2 and a third winding N3, wherein the third winding N3 and the second winding N2 are connected in series via a diode.
In the present embodiment, the first winding N1 is arranged on the first PCB 10a, the second winding N2 is arranged on the second PCB 10b, the third winding N3 is arranged on the fourth PCB 10c, and the power supply winding is arranged on the fourth PCB 10d, but the present application is not limited thereto.
Specifically, the center tap of the primary winding Pri taps the first winding N1 and the power supply winding connected in series, and the center tap of the secondary winding Sec taps the second winding N2 and the third winding N3 connected in series. The number of turns of the coils of the first winding N1 and the power supply winding is the same and the wire diameter is the same; the second winding N2 and the third winding N3 have the same number of turns and the same wire diameter.
In this embodiment, the second end of the first winding N1 is the second end of the primary winding Pri, and the first end of the power supply winding is the first end of the primary winding Pri. The first ends of the windings are homonymous ends and the second ends are synonym ends, but the winding is not limited to the homonymous ends.
The second end of the first winding N1 is connected to the primary ground GND via a first capacitor C1, and the first end is connected to the first end of the switching tube Q. A second terminal of the switching tube Q is connected to the current sampling terminal CS of the control circuit 220.
In this embodiment, the power supply winding includes a fourth winding N4 and a fifth winding N5, and the number of coil turns of the fourth winding N4 and the fifth winding N5 may be the same or different according to the magnitude of the voltage. The fifth winding N5 and the first diode D1 are connected in series. Specifically, the first end of the fourth winding N4 is connected to the primary ground GND, the second end of the fourth winding N4 is connected to the first end of the fifth winding N5, the first end of the fifth winding N5 is connected to the second end of the fifth winding N5 via the first diode D1 and the second capacitor C2, and the second end of the fifth winding N5 is connected to the chip ground.
The first end of the second winding N2 is used as the first end of the secondary winding Sec, the second end of the third winding N3 is used as the second end of the secondary winding Sec, and the second end of the third winding N3 is connected with the secondary ground SGND. The first end of the third winding N3 is connected with the second end of the second winding N2 through a second switching tube, the positive electrode of the second switching tube is connected with the first end of the third winding N3, and the negative electrode of the second switching tube is connected with the second end of the second winding N2. In this embodiment, the second switching tube is, for example, a second diode D2.
The control circuit 220 includes a driving terminal Gate, a current sampling terminal CS, a power terminal VDD, and a ground terminal GND.
In this embodiment, the switching tube Q is connected in series between the first end of the first winding N1 and the current sampling end CS of the control circuit 220; the control end of the switching tube Q is connected to the driving end Gate of the control circuit 220, and the power supply winding is connected to the power supply end VDD of the control circuit via the first diode D1 to supply power to the control circuit 220.
At least one of the fourth winding N4 and the fifth winding N5 serves as a power supply winding to supply power to the control circuit 220. The number of turns of the fourth winding N4 and the fifth winding N5 may be different, and different turns ratios are set according to the magnitude of the supplied power voltage.
Conventionally, the name of the PCB 10 is printed circuit board, also called printed circuit board, which is an important electronic component, is a support for electronic components, and is a carrier for electrically interconnecting the electronic components. The PCB board 10 is formed by laminating a core board, a prepreg and an outer copper foil. Wherein the copper foil is a thin, continuous metal foil deposited on the base layer of the PCB board 10, which serves as an electrical conductor of the PCB board 10, is easily adhered to the insulating layer, and forms a circuit pattern after corrosion.
According to the planar transformer provided by the embodiment of the application, the primary winding and the secondary winding are subjected to center tapping, so that the primary winding forms the first winding and the power supply winding which are connected in series, and the secondary winding forms the second winding and the third winding which are connected in series so as to mutually offset common mode noise currents from the secondary winding to the primary winding, the planar transformer can adapt to the balance requirements of different common mode noises, has a good electromagnetic interference suppression effect, and can reduce the use of peripheral EMI filter devices, thereby reducing the production cost and reducing leakage current in a circuit.
Furthermore, the planar transformer has no independent shielding or balance windings, so that the PCB winding board can be provided with four layers or less than four layers of PCB boards, and the through hole technology is adopted to connect and conduct all the board layers.
Further, the top layer and the bottom layer of the PCB winding board are respectively provided with a silk-screen printing layer to cover the winding unit so as to achieve the insulation and voltage-resistant effects.
The technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples illustrate only a few embodiments of the application, which are described in detail and are not to be construed as limiting the scope of the application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of protection of the present application is to be determined by the appended claims.

Claims (8)

1. A planar transformer, comprising:
the PCB winding board comprises at most four layers of PCB boards which are arranged in a stacked manner, each layer of PCB winding board is provided with a through hole, an opening penetrating through the PCB winding board is formed in the PCB winding board, and the opening is used for accommodating a center column of the magnetic core;
the winding unit is arranged on the PCB winding board and comprises a primary winding and a secondary winding;
the silk screen printing layer is arranged on the top surface and the bottom surface of the PCB winding board and covers the winding unit;
wherein the center tap of the primary winding taps the first winding and the power supply winding connected in series, and the center tap of the secondary winding taps the second winding and the third winding connected in series.
2. The planar transformer of claim 1, wherein the first winding and the power supply winding have the same number of turns and the same wire diameter; the number of turns of the coils of the second winding and the third winding are the same and the wire diameters are the same.
3. The planar transformer of claim 1, wherein the second end of the first winding is connected to the primary ground via a first capacitor, and the first end is connected to the first end of the switching tube.
4. The planar transformer of claim 1, wherein the power supply winding comprises a fourth winding and a fifth winding, the fifth winding and the first diode being connected in series.
5. The planar transformer of claim 4, wherein a first end of the fourth winding is connected to a primary ground, a second end of the fourth winding is connected to a first end of the fifth winding, and the first end of the fifth winding is connected to the second end of the fifth winding via a first diode and a second capacitor, and the second end of the fifth winding is connected to a chip ground.
6. The planar transformer of claim 1, wherein the first end of the second winding is a first end of a secondary winding, the second end of the third winding is a second end of the secondary winding, and the second end of the third winding is connected to a secondary ground.
7. The planar transformer of claim 6, wherein the first end of the third winding is connected to the second end of the second winding via a second switching tube, the positive electrode of the second switching tube is connected to the first end of the third winding, and the negative electrode of the second switching tube is connected to the second end of the second winding.
8. The planar transformer of claim 1, wherein the PCB board is made of glass fiber board or paper substrate or ceramic substrate or flexible board.
CN202310849249.9A 2023-07-11 2023-07-11 Switching power supply and planar transformer thereof Pending CN116844832A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202310849249.9A CN116844832A (en) 2023-07-11 2023-07-11 Switching power supply and planar transformer thereof

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202310849249.9A CN116844832A (en) 2023-07-11 2023-07-11 Switching power supply and planar transformer thereof

Publications (1)

Publication Number Publication Date
CN116844832A true CN116844832A (en) 2023-10-03

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ID=88164948

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202310849249.9A Pending CN116844832A (en) 2023-07-11 2023-07-11 Switching power supply and planar transformer thereof

Country Status (1)

Country Link
CN (1) CN116844832A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN119170389A (en) * 2024-09-26 2024-12-20 东科半导体(安徽)股份有限公司 Two-winding planar transformer and printed circuit board for the two-winding planar transformer

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN119170389A (en) * 2024-09-26 2024-12-20 东科半导体(安徽)股份有限公司 Two-winding planar transformer and printed circuit board for the two-winding planar transformer
CN119170389B (en) * 2024-09-26 2025-09-26 东科半导体(安徽)股份有限公司 Two-winding planar transformer and printed circuit board for the same

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