TWI382645B - Power supply apparatus - Google Patents

Description

Power supply unit

The present invention relates to a power supply device, and more particularly to a power supply device for powering an electronic device.

With the development of science and technology, more and more electronic products are on the market. Most of the power sources used in electronic products are DC power supplies, and the power supply network is generally AC. Therefore, most electronic devices are equipped with a power supply device to convert the AC power to a DC power source and convert the voltage required by the transformer into an electronic device.

As shown in FIG. 1, the power supply device of the electronic device generally includes an input rectification filter circuit 102, a power switch circuit 104, a transformer 106, an output rectification filter circuit 108, a comparison circuit 110, and a pulse width modulation (PWM) control circuit 112. The input rectification and filtering circuit 102 rectifies the alternating current in the power grid into a direct current, and then filters the processing to generate a relatively smooth direct current for the next level of transformation. Power switching circuit 104 converts the direct current into a varying pulse voltage. The pulse voltage is converted into alternating current by the transformer 106 and then converted into a smooth output direct current by the output rectifying and filtering circuit 108. The output DC power can be used to power the load, and part of the output DC power is fed back to the comparison circuit 110 as feedback. The comparison circuit 110 outputs the comparison result to the PWM control circuit 112, and the PWM control circuit 112 controls the power switch according to the comparison result, that is, adjusts the pulse width of the pulse voltage, thereby controlling the power of the output DC power.

The development trend of miniaturization and thinning of electronic equipment makes the above power switch circuit 104, transformer 106, output rectification and filtering circuit 108, and comparison The layout of the circuit 110 and the PWM control circuit 112 on the printed circuit board is more and more tight, and therefore electromagnetic interference is often generated between different components and circuits. For example, the transformer 106 is likely to have an influence on the power switch circuit 104 and the PWM control circuit 112 due to electromagnetic changes during operation, thereby affecting the stability of the output DC power.

Unstable output DC power is applied to the load, which may cause the electronic device to malfunction or shorten its working life. Taking a liquid crystal display as an example, when an unstable output DC power is applied to a control circuit and a driving circuit of the liquid crystal display, the screen may be shaken, and the liquid crystal display may be unusable.

In view of this, it is necessary to provide a power supply device that can provide stable output DC power.

A power supply device comprises: an input rectification filter circuit, a control circuit, a transformer circuit and an output rectification filter circuit, wherein the input rectification filter circuit, the transformer circuit and the output rectification filter circuit are mounted on the main circuit board; the input rectification filter circuit is used Converting the alternating current power into primary direct current; the control circuit is for controlling the primary direct current; the transformer circuit is for transforming the primary direct current controlled by the control circuit; the output rectifying and filtering circuit is used for transforming The primary direct current is converted into a load direct current; the control circuit is mounted on a separate circuit board and covered by a metal mask layer; the separate circuit board is electrically connected to the main circuit board, and the metal mask layer is used It shields the external electromagnetic wave from the interference caused by the control circuit.

The above power supply device is assembled on a separate circuit board by controlling the circuit The control circuit is covered by a metal mask layer to reduce the influence of external electromagnetic interference on the control circuit. Therefore, the influence of the electromagnetic interference of the power supply device can be reduced, and the stability of the output direct current can be improved.

As shown in FIG. 2, the power supply device 200 includes an input rectification and filtering circuit 210, a PFC (Power Factor Correction)/PWM (Pulse Width Modulation) control circuit 220, a transformer circuit 230, and an output rectification filter circuit. 240. As shown in FIG. 3, it is a circuit schematic diagram of a preferred embodiment of the power supply device 200. The AC power supply VAC is rectified and filtered by the input rectification and filtering circuit 210 (mainly including the rectifier bridge D1) to generate primary DC power. Under the control of the PFC/PWM control circuit 220 (mainly including the PFC/PWM controller U1), the primary direct current is transformed by the voltage. The circuit 230 (mainly including the transformer T1) is transformed and then outputs a load DC current to the load via the output rectification and filtering circuit 240 (mainly including D4 and C2). The controller U1 is a PFC/PWM combination controller, which can realize separate control of PFC and PWM, and saves wiring space required for control of multiple devices, so that the power supply device of the PFC/PWM controller U1 can be miniaturized.

In order to reduce the influence of AC power VAC fluctuation on the load, the input rectification filter circuit 210 and the PFC/PWM control circuit 220 of the AC power supply VAC are isolated from the output rectification and filtering circuit 240 by the transformer T1 and the optocoupler element U2, and are grounded separately. The output condition of the load DC is fed back to the PFC/PWM control circuit 220 by the optocoupler element U2, thereby realizing the regulation of the load DC power.

In order to reduce the power of the peripheral components of the transformer T1 to the PFC/PWM controller U1 Magnetically, the PFC/PWM control circuit 220 including the PFC/PWM controller U1 is mounted on a separate circuit board. As shown in FIG. 4, the PFC/PWM control circuit 220 is mounted on a separate circuit board 222 and connected to the main circuit board 202 of the power supply unit 200 via a connector 224. After the PFC/PWM control circuit 220 is mounted on the circuit board 222, the PFC/PWM control circuit 220 is covered with a metal mask layer, so that the influence of external electromagnetic interference on the PFC/PWM control circuit 220 can be reduced. In addition, by increasing the number of connectors 224 between the circuit board 222 and the main circuit board 202, the electrical connection area between the circuit board 222 and the main circuit board 202 can be increased, thereby reducing current density and improving PFC/PWM control. The operational stability of circuit 220. For example, the two connectors 224 shown in FIG. 4, of course, the number of connectors 224 can be set to three, four or more.

Since the power supply device 200 generally generates a large amount of heat, the layout of the PFC/PWM control circuit 220 on the circuit board 222 may be provided with a ring-shaped component isolation band, thereby facilitating heat dissipation of the components. In addition, a heat dissipation through hole 226 is provided on the circuit board 222 to facilitate air circulation, thereby improving the heat dissipation effect.

As shown in FIG. 5, in order to further reduce the electromagnetic influence of the peripheral components such as the transformer circuit 230 on the PFC/PWM controller U1 and the like, electromagnetic absorption is formed on the main circuit board 202 on which the transformer circuit 230 is placed, when the main circuit board is wired. Line 204. The electromagnetic absorption line 204 is on the insulating medium substrate of the printed circuit board, and a thin metal layer is attached as a ground plate on one side, and a metal foil of a certain shape is formed on the other surface by photolithography etching, for example, a spiral electromagnetic absorption as shown in FIG. Line 204. The center end 206 of the electromagnetic absorption line 204 is grounded and extends helically outwardly from the center end 206 to form a helical electromagnetic absorption line 204.

When the transformer circuit 230 is in operation, the electromagnetic wave generated by the changed electromagnetic field is absorbed by the electromagnetic absorption line 204, and an induced potential is generated on the electromagnetic absorption line 204. Since the center end 206 of the electromagnetic absorption line 204 is grounded, the induced potential is introduced to the ground. absorb.

The power supply device 200 can reduce the external electromagnetic interference to the PFC/PWM control circuit 220 by assembling the PFC/PWM control circuit 220 on a separate circuit board 222 and covering the PFC/PWM control circuit 220 with a metal mask layer. In addition, the electromagnetic absorption line 204 can absorb the electromagnetic waves generated by the transformer circuit 230, thereby reducing the influence of other components on the electromagnetic waves. Therefore, it is possible to reduce the influence of the power supply device 200 on electromagnetic interference and improve the stability of the output direct current.

To sum up, the invention complies with the requirements of the invention patent and submits a patent application according to law. However, the above description is only a preferred embodiment of the present invention, and equivalent modifications or variations made by those skilled in the art of the present invention should be included in the following claims.

200‧‧‧Power supply unit

202‧‧‧Main board

204‧‧‧Electromagnetic absorption line

206‧‧‧Center

210‧‧‧Input rectification filter circuit

220‧‧‧PFC/PWM control circuit

222‧‧‧ circuit board

224‧‧‧Connector

226‧‧‧Heat through hole

230‧‧‧Transformer circuit

240‧‧‧Output rectification filter circuit

1 is a schematic view of a conventional power supply unit.

2 is a schematic diagram of a power supply device of a preferred embodiment.

3 is a circuit diagram showing a specific structure of the power supply device shown in FIG. 2.

4 is a schematic view showing the distribution of the power supply device of FIG. 2 on a circuit board.

Figure 5 is a schematic diagram of the wiring of the electromagnetic absorption line on the circuit board.

200‧‧‧Power supply unit

202‧‧‧Main board

210‧‧‧Input rectification filter circuit

220‧‧‧PFC/PWM control circuit

222‧‧‧ circuit board

224‧‧‧Connector

226‧‧‧Heat through hole

230‧‧‧Transformer circuit

240‧‧‧Output rectification filter circuit

Claims (10)

A power supply device comprises: an input rectification filter circuit, a control circuit, a transformer circuit and an output rectification filter circuit, wherein the input rectification filter circuit, the transformer circuit and the output rectification filter circuit are mounted on the main circuit board; the input rectification filter circuit is used Converting the alternating current power into primary direct current; the control circuit is for controlling the primary direct current; the transformer circuit is for transforming the primary direct current controlled by the control circuit; the output rectifying and filtering circuit is used for transforming The primary direct current is converted into a load direct current; the improvement is that the control circuit is mounted on a separate circuit board and covered with a metal mask layer; the separate circuit board is electrically connected to the main circuit board, the metal The mask layer is used to shield the external electromagnetic waves from causing interference to the control circuit. The power supply device of claim 1, wherein an electromagnetic absorption line is provided on the main circuit board on which the transformer circuit is placed. The power supply device of claim 2, wherein the electromagnetic absorption line is spiral. The power supply device of claim 3, wherein the center end of the electromagnetic absorption line is grounded. The power supply device of claim 1, wherein the control circuit is a power factor correction/pulse width modulation control circuit. The power supply device of claim 1, wherein the input rectification filter circuit and the control circuit are isolated from the output rectification filter circuit by a transformer and an optocoupler element, and are separately grounded. The power supply device of claim 1, wherein the independent circuit board and the main circuit board are electrically connected by a connector. The power supply device of claim 7, wherein the connector The number is greater than 1. The power supply unit of claim 5, wherein the power factor correction/pulse width modulation control circuit is disposed on the independent circuit board with a ring-shaped element isolation strip. The power supply device of claim 5, wherein the independent circuit board is provided with a heat dissipation through hole.