KR20180002363A - Snubber Circuit Integrated Planar Transformer - Google Patents

Abstract

The present invention provides a snubber circuit integrated type planar transformer which resolves an electromagnetic interference (EMI) and heating problems and is capable of improving efficiency. According to an embodiment of the present invention, the snubber circuit integrated type planar transformer comprises: a core part having a pair of cores magnetically coupled to each other; a plurality of substrates located between the pair of cores, and laminated on each other; and a pattern layer including a first winding and a second winding formed on the substrate. One side surface of the substrate can include a snubber circuit electrically connected to the pattern layer.

Description

A Snubber Circuit Integrated Planar Transformer (Snubber Circuit Integrated Planar Transformer)

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a planar transformer, and more particularly, to a snubber circuit integrated planar transformer.

The flyback converter can be driven by only one switch element, and is being applied in a small capacity SMPS area of industrial and home appliances. The flyback converter has a merit that the drive circuit is simple, but the circuit that recovers the energy stored in the leakage inductance at the time of the primary MOSFET switch off due to the leakage inductance of the transformer is a secondary circuit, .

In general, the circuit for recovering the energy stored in the leakage inductance is an RCD snubber circuit consisting of a diode, a capacitor and a resistor. This RCD snubber circuit dissipates the recovered energy through the resistor. This is a major cause of the heat loss due to high heat generation. The leakage inductance of the transformer is usually 1 to 3% of the excitation inductance.

Unlike a wire-wound transformer, a planar transformer consists of a multi-layer PCB, and two types of transformers are used in the form of parts common to the flyback converter substrate. Also, on the transformer secondary side, the metal thickness must be considered because of the skin effect on the converter switching frequency. The design of the secondary metal thickness according to the skin effect in the design of the transformer is usually based on the calculation formula. At this time, the transformer and the RCD snubber circuit should be arranged in the shortest path on the flyback converter substrate in order to prevent the efficiency decrease.

Flyback converters are typically used in microelectronics, such as smartphone chargers, with many built-in components making it difficult to make the transformer and snubber circuits the shortest path. In addition, only the increase of the metal thickness due to the skin effect of the secondary side of the transformer was considered, but the skin effect of this section was not considered.

Figure 1 shows a typical flyback converter circuit, and Figure 2 is a perspective view of a planar transformer used in the flyback converter.

Referring to FIG. 1, TX1 may be a wire-wound or planar transformer, and the snubber circuit 1 is composed of a diode SD1, a capacitor C7, and a resistor R13.

At this time, the elements (the diode SD1, the capacitor C7, and the resistor R13) constituting the snubber circuit are mounted on the PCB of the flyback converter.

The shorter the distance between the most current transformer (TX1) and the diode (SD1), the higher the efficiency and the lower the heat generation, and the EMI (Electro Magnetic Inference) due to the switching frequency of the flyback converter can be reduced.

However, the transformer (TX1) is usually configured in the form of a DIP (Dual Inline Package) with metal leads, mounted on the PCB of the flyback converter, and connected to the RCD snubber circuit in the form of a SMD (Surface Mount Device) . At this time, the via hole of the DIP device of the transformer is formed on the PCB of the flyback converter, and the snubber circuit is connected to the PCB pattern. This path connects the PCB via hole of the planar transformer with the metal lead of the planar transformer connected, which is reconnected to the flyback converter PCB via hole and connected to the RCD snubber circuit as a PCB pattern. The resistance component of this path pattern lowers efficiency, causes heat generation of the diode, and causes EMI in the flyback converter.

Therefore, it is necessary to develop a technology that can improve EMI and efficiency while using a snubber circuit.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a planar transformer integrated with a snubber circuit capable of solving EMI and heat generation problems and improving efficiency.

According to an aspect of the present invention, there is provided a planar transformer integrated with a snubber circuit, comprising: a core part having a pair of cores magnetically coupled to each other; A plurality of substrates disposed between the pair of cores and stacked on each other; And a pattern layer including a primary winding and a secondary winding formed on the substrate, and a snubber circuit electrically connected to the pattern layer may be formed on one side of the substrate.

Also, in the snubber circuit integrated type planar transformer according to an embodiment of the present invention, the snubber circuit may include a resistor, a capacitor, and a diode.

Further, in the snubber circuit integrated type flat transformer according to an embodiment of the present invention, the snubber circuit may be electrically connected to the secondary winding.

In the planar transformer integrated with a snubber circuit according to an embodiment of the present invention, a connection end of a conductive material for mounting the snubber circuit is formed on the substrate, and the snubber circuit is formed on the connection end .

In the planar transformer integrated with a snubber circuit according to an embodiment of the present invention, the connection end may include a resistance connection terminal to which a resistance element is mounted, a capacitor connection terminal to which the capacitor element is mounted, and a diode connection terminal . ≪ / RTI >

In the planar transformer integrated with a snubber circuit according to an embodiment of the present invention, a heat dissipation via hole may be formed in the diode connection end.

Further, in the planar transformer integrated with a snubber circuit according to an embodiment of the present invention, a heat dissipation via hole and inner metal layer patterns may be formed at the diode connection end.

According to the embodiment of the present invention, the efficiency of the flyback converter can be improved to solve the EMI and heat generation shape.

Further, according to the embodiment of the present invention, since the snubber circuit is incorporated in the transformer, the number of components of the charger can be reduced, contributing to miniaturization.

1 shows a circuit diagram of a flyback converter according to the prior art.
2 is a perspective view illustrating a planar transformer according to an embodiment of the present invention.
3 is an exploded perspective view of a planar transformer according to an embodiment of the present invention.
4 is an exploded perspective view of a pattern layer of a planar transformer according to an embodiment of the present invention.
FIG. 5 shows an example in which a plane transformer to which the present invention is applied is applied.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

In the drawings, embodiments of the present invention are not limited to the specific forms shown and are exaggerated for clarity. Although specific terms are used herein, It is to be understood that the same is by way of illustration and example only and is not to be taken by way of limitation of the scope of the appended claims.

The expression " and / or " is used herein to mean including at least one of the elements listed before and after. Also, the expression " coupled / connected " is used to mean either directly connected to another component or indirectly connected through another component. The singular forms herein include plural forms unless the context clearly dictates otherwise. Also, as used herein, "comprising" or "comprising" means to refer to the presence or addition of one or more other components, steps, operations and elements.

Also, the expressions such as 'first, second', etc. are used only to distinguish between plural configurations, and do not limit the order or other features among the configurations.

In the description of the embodiments, it is to be understood that each layer (film), area, pattern or structure may be referred to as being "on" or "under / under" Quot; includes all that is formed directly or through another layer. The criteria for top / bottom or bottom / bottom of each layer are described with reference to the drawings.

Hereinafter, a snubber circuit integrated type planar transformer and a determination method according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a perspective view of a planar transformer according to an embodiment of the present invention, FIG. 3 is an exploded perspective view of FIG. 2, and FIG. 4 is an exploded view of a metal layer inside a transformer.

(B) is a shape in which the core is removed in (a), (c) is a shape obtained by removing the solder mask and the silk pattern, and (d) is a cross- The substrate is removed, and only the metal pattern layer structure is shown.

Referring to FIGS. 2 to 4, a planar transformer according to an embodiment of the present invention includes a core portion 10, a substrate 20, and a metal pattern 30.

The core portion 10 may be composed of a pair of ferrite cores 11 and 12 which are magnetically coupled to each other. That is, the upper core 11 and the lower core 12 are coupled to each other. The lower core 12 is formed with a rectangular protrusion 13. Although the upper core and the lower core are illustrated as rectangular in the present embodiment, the upper core and the lower core are not limited thereto but may be circular or other shapes.

Layer substrate in which a plurality of substrates of the substrate 20 are laminated. A through hole (H) is formed in the central portion, and the metal pattern layer (30) may be formed as a spiral around the through hole.

A solder mask 27 and a silk pattern 28 may be formed on the substrate 20. The solder mask 27 protects the circuit by coating the copper foil circuit and prevents a solder bridging phenomenon from occurring in a process such as component mounting.

A metal pattern layer is formed around the through hole H of the substrate 20 and the elements R, C, and D constituting the snubber circuit are formed on one side of the substrate on which the metal pattern layer 30 is not formed Is mounted. In addition, winding terminals 21, 22, 23, 24, 25, 26 connected to the windings can be formed on both outer sides of the substrate 20.

That is, the resistor R, the capacitor C, and the diode D constituting the snubber circuit can be formed on one side of the outer side of the upper portion of the substrate.

A connection end 34 to which elements can be connected is connected to the metal pattern layer 30 under the resistor R, the capacitor C, and the diode D.

The connection end 34 may have a rectangular shape and may include a plurality of holes 39 to dissipate heat generated from the transformer.

The metal pattern layer 30 includes an auxiliary winding 31, a primary winding 32 and a secondary winding 33. The auxiliary winding 31 is connected to auxiliary winding terminals 21 and 22 The primary winding 32 is connected to the primary winding terminals 23 and 24 and the secondary winding 33 is connected to the secondary winding terminals 25 and 26. [

The connection end (34) is connected to the secondary winding (33) of the metal pattern layer (30).

4, the connection end 34 may include a resistor connection end 35, a capacitor connection end 36, and a diode connection end 37, 38.

A resistor R is formed on top of the resistor connection 35 and a capacitor C is formed on top of the capacitor connection end 36 and a diode D is formed on top of the diode connection end 37, As shown in FIG. The diode connection end is composed of a diode input terminal 37 and a diode output terminal 38 and a plurality of via holes 39 are formed in the diode output terminal 38 to dissipate heat generated from the transformer.

As described above, by forming the resistor, the capacitor, and the diode, which are the elements constituting the snubber circuit, on one side of the multilayer substrate, the distance between the snubber circuit and the substrate can be reduced and various problems caused by the conventional snubber circuit can be solved .

For example, when mounting the elements (resistors, capacitors, diodes) that constitute the snubber circuit on the circuit board of the flyback converter, the distance between the diode and the transformer output is at least 10 mm. This is caused by the narrow area of the flyback converter's main board and the placement of components, which results in efficiency degradation and heat generation at high currents and EMI.

However, when the elements constituting the snubber circuit are mounted on one side of the substrate of the planar transformer as in the present invention, the diode D is connected to the output terminal of the secondary winding at the shortest distance, Does not occur. In addition, the resulting heat generation and EMI are significantly reduced.

In addition, since a plurality of via holes are provided at the diode output terminal, heat generation can be efficiently solved. Therefore, the output of the RCD snubber circuit is connected to the planar transformer secondary winding terminal and connected to the output of the flyback converter main board. This allows the charger to be implemented without degrading efficiency.

Further, the transformer according to the present invention can be applied to both a DIP (Dual In Line Package) type and a SMD (Surface Mount Device) type.

While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined by the appended claims. Accordingly, the true scope of the present invention should be determined by the following claims.

10: Core
20: substrate
30: pattern layer
31: auxiliary winding
32: primary winding
33: Secondary winding
34: Connection end
35: Resistor connection terminal
36: Capacitor connection terminal
37, 38: Diode connection terminal
39: Via hole

Claims (7)

A core portion having a pair of cores magnetically coupled to each other;
A plurality of substrates disposed between the pair of cores and stacked on each other; And
And a pattern layer including a primary winding and a secondary winding formed on the substrate,
And a snubber circuit electrically connected to the pattern layer on one side surface of the substrate.
The method according to claim 1,
The snubber circuit includes a resistor, a capacitor, and a diode.
The method according to claim 1,
Wherein the snubber circuit is electrically connected to the secondary winding.
The method according to claim 1,
Wherein a connecting end of a conductive material for mounting the snubber circuit is formed on the substrate, and the snubber circuit is formed on the connecting end of the snubber circuit integrated type flat transformer.
6. The apparatus according to claim 5,
A snubber circuit integrated flat transformer including a resistor connection terminal to which a resistance element is mounted, a capacitor connection terminal to which a capacitor element is mounted, and a diode connection terminal to which a diode element is mounted.
6. The method of claim 5,
And a diode connection end is provided with a heat dissipation via hole.
6. The method of claim 5,
Wherein the diode connection end has a heat dissipation via hole and inner metal layer patterns formed thereon.

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