CN204130325U - A kind of transformer being applicable to Switching Power Supply - Google Patents

Abstract

The utility model discloses a transformer suitable for switching power supplies, which comprises a skeleton (1), an iron core (2) inserted in the central cavity of the skeleton and surrounded on the outside of the skeleton, the bottom layer of the skeleton is wound with a primary winding (N1 ), the power input pin and ground pin of the primary winding protrude from one side of the frame, the ground pin of the primary winding is connected to the iron core through a wire, and the outer side of the primary winding is covered with a shielding layer (E1), and the shielding layer is connected to the primary winding through a wire The grounding pin of the winding, the first secondary winding (N2) and the second secondary winding (N3) are sequentially wound on the outer side of the shielding layer, and the number of turns, winding direction and phase of the first and second secondary windings are the same. Compared with the prior art, the utility model has little interference noise, no leakage current, can remove the input common-mode filter inductance and Y capacitance in the circuit, and can meet relevant EMC regulations and customers' requirements for extremely low power supply leakage current.

Description

A Transformer Suitable for Switching Power Supply

technical field

The utility model relates to a transformer, in particular to a low-power transformer suitable for switching power supplies.

Background technique

Switching power supplies are widely used in power adapters, lighting equipment, and small-power motors. The core component of the switching power supply is the transformer. The performance and safety requirements of the transformer are getting higher and higher. At the same time, its cost is expected to be lower and lower. While the leakage current of the transformer is required to be smaller and smaller, it must meet the requirements of relevant laws and regulations such as EMC. There is common-mode interference inside the existing transformer, and the high-frequency noise of the primary is coupled to the secondary, thereby affecting the electronic equipment connected to the secondary. The existing solution is to connect the Y capacitor across the primary and secondary, and the common-mode interference noise can form a loop through the Y capacitor, effectively reducing the amplitude of the common-mode interference noise. The disadvantage of this solution is that it will produce a side effect of leakage current and increase the cost of the circuit at the same time.

Therefore, it is an urgent technical problem in the industry to develop a transformer with low interference noise, no leakage current, and the ability to remove the Y capacitor and reduce the circuit cost.

Utility model content

The utility model aims to solve the above-mentioned problems of the prior art, and proposes a low-power transformer suitable for switching power supplies with little interference noise and no leakage current.

In order to solve the above technical problems, the technical solution proposed by the utility model is to design a transformer suitable for switching power supplies, including a skeleton, an iron core inserted in the central cavity of the skeleton and surrounded on the outside of the skeleton, the bottom layer of the skeleton is wound The primary winding, the power input pin and the grounding pin of the primary winding protrude from one side of the frame, the grounding pin of the primary winding is connected to the iron core through a wire, and the outer side of the primary winding is covered with a shielding layer, and the shielding layer is connected to the primary winding through a wire The grounding pin, the first secondary winding and the second secondary winding are sequentially wound on the outer side of the shielding layer, and the number of turns, winding direction and phase of the first and second secondary windings are the same.

A layer of primary auxiliary winding is wound on the outside of the second secondary winding. The power output pin and grounding pin of the primary auxiliary winding protrude from one side of the frame, and the grounding pin of the primary auxiliary winding is connected to the iron core through a wire.

An insulating layer is provided between the primary winding and the shielding layer.

The insulating layer, the first secondary winding, the second secondary winding, the primary auxiliary winding, and the adjacent layers or windings are all provided with insulating layers.

The width of the primary winding is the same as the width of the bobbin window.

The shielding layer is copper foil, the width of the copper foil is the same as that of the skeleton window, and the thickness of the copper foil is 0.025 mm to 0.1 mm.

The shielding layer is a layer of tightly wound enameled wire, and the width of the shielding layer is the same as that of the skeleton window.

Compared with the prior art, the utility model has little interference noise, no leakage current, can remove the input common-mode filter inductance and Y capacitor in the circuit, and can meet relevant EMC regulations and customers' requirements for extremely low power supply leakage current.

Description of drawings

Fig. 1 is the circuit schematic diagram of the preferred embodiment of the present utility model;

Fig. 2 is the front view of the skeleton of the preferred embodiment of the utility model;

Fig. 3 is the front view of the preferred embodiment of the utility model;

Fig. 4 is a cross-sectional view of a preferred embodiment of the present invention.

Detailed ways

In order to make the purpose, technical solution and advantages of the utility model clearer, the utility model will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the utility model, and are not intended to limit the utility model.

A transformer suitable for switching power supplies (mainly suitable for transformers with an output power of less than 18W), which includes a skeleton 1. The picture of the skeleton is shown in Figure 2, and the core 2 is surrounded in the central cavity of the skeleton and outside. Fig. 3 is the front view of the preferred embodiment, the iron core is assembled after the coil is wound in the window of the skeleton. Referring to the schematic diagram of the circuit shown in Figure 1, the transformer has a primary winding N1, a first secondary winding N2 and a second secondary winding N3, referring to the cross-sectional view shown in Figure 4, the bottom layer of the skeleton is wound with the primary winding N1, The power input pin and ground pin of the primary winding protrude from one side of the frame, the ground pin 5 of the primary winding is connected to the iron core 2 through a wire 6, and the outer side of the primary winding is covered with a layer of shielding layer E1, and the shielding layer is connected to the primary winding through a wire The first secondary winding N2 and the second secondary winding N3 are sequentially wound on the outside of the shielding layer, and the number of turns and the winding direction of the first and second secondary windings are the same (both are forward winding or both are reverse winding) , and the same phase. The shielding layer shields the interference noise from the primary winding, guides these interference noises to the ground, and eliminates the leakage current. After using the transformer, the switching power supply can remove the Y capacitance, thereby reducing the circuit cost. It should be pointed out that the first secondary winding N2 and the second secondary winding N3 can supply power to different loads separately, and can also be used in parallel to solve the problem that a single wire is too thick and hard to wind. After parallel connection, the wire area is doubled, and a larger current can be passed through, and the EMC effect is better.

In a preferred embodiment, a layer of primary auxiliary winding N4 is wound outside the second secondary winding N3, the power output pin and ground pin of the primary auxiliary winding protrude from one side of the frame, and the ground pin of the primary auxiliary winding Connect the cores with wires. The second secondary winding N3 is mainly used to provide working power for chips in the switching power supply.

In a preferred embodiment, an insulating layer 3 is provided between the primary winding N1 and the shielding layer E1. In order to achieve a better insulation effect, an insulating layer 3 is provided between adjacent layers or windings of the insulating layer 3 , the first secondary winding N2 , the second secondary winding N3 , and the primary auxiliary winding N4 .

In a preferred embodiment, the width of the primary winding N1 is the same as the width of the skeleton window.

In some embodiments, the shielding layer E1 is copper foil, the width of the copper foil is the same as that of the skeleton window, and the thickness of the copper foil is 0.025 mm to 0.1 mm.

In some other embodiments, the shielding layer E1 is a layer of tightly wound enameled wire, and the width of the shielding layer is the same as that of the skeleton window.

This new type solves the contradiction between the performance and cost of switching power supply products, and has the advantages of simple production process, high reliability, easy operation, etc., especially when used on low-power power adapters, it has obvious cost-effective advantages. Experiments have proved that the primary and secondary leakage current of the power supply products using this transformer is extremely low, and there is almost no interference to consumers. Experiments have proved that the power supply products using this new type of Y-capacitor-free switching power supply transformer have a margin of more than 6dB when meeting the electromagnetic interference regulations EN55022 Class B/FCC part15 classB.

The above examples are illustrative only and not limiting. Any equivalent modification or change made without departing from the spirit and scope of the present application shall be included in the scope of the claims of the present application.

Claims (7)

1. A transformer suitable for switching power supplies, including a skeleton (1), an iron core (2) inserted in the central cavity of the skeleton and surrounding the outside of the skeleton, characterized in that: the bottom layer of the skeleton is wound with a primary winding ( N1), the power input pin and ground pin of the primary winding protrude from one side of the frame, the ground pin of the primary winding is connected to the iron core through a wire, and the outer side of the primary winding is covered with a shielding layer (E1), which is connected through a wire The grounding pin of the primary winding, the first secondary winding (N2) and the second secondary winding (N3) are sequentially wound outside the shielding layer, and the number of turns, winding direction and phase of the first and second secondary windings are the same. 2. The transformer suitable for switching power supply according to claim 1, characterized in that: a layer of primary auxiliary winding (N4) is wound on the outside of the second secondary winding (N3), and the power output pin of the primary auxiliary winding And the grounding pin protrudes from one side of the skeleton, and the grounding pin of the primary auxiliary winding is connected to the iron core through a wire. 3. The transformer suitable for switching power supplies according to claim 2, characterized in that: an insulating layer (3) is provided between the primary winding (N1) and the shielding layer (E1). 4. The transformer suitable for switching power supply according to claim 3, characterized in that: the insulating layer (3), the first secondary winding (N2), the second secondary winding (N3), the primary auxiliary winding ( N4), insulating layers (3) are provided between adjacent layers or windings. 5. The transformer suitable for switching power supply according to claim 4, characterized in that: the width of the primary winding (N1) is the same as the width of the frame window. 6. The transformer suitable for switching power supply according to any one of claims 1 to 5, characterized in that: the shielding layer (E1) is copper foil, the width of the copper foil is the same as the width of the skeleton window, and the copper foil The thickness is 0.025 mm to 0.1 mm. 7. The transformer suitable for switching power supplies according to any one of claims 1 to 5, characterized in that: the shielding layer (E1) is a layer of tightly wound enameled wire, and the width of the shielding layer is the same as the width of the skeleton window .