How to use LED switching power supply design PCB circuit?

   Through recent years LED power supply layout components research and market practice results show that even in the early stages of development, the design of the circuit principle diagram is very correct. However, once the PCB design problems, have adverse effects on the reliability of electronic equipment, such as due to interference of power supply, ground considered not attentive and cause, will make product performance decreased, so in the design of PCB board, you need to use correct method.

   In a switching power supply used to the PCB board, usually every switching power supply has four current loop, they are the input signal source current circuit, power switch AC circuit, output rectifier AC circuit, output load current loop. The input circuit is charged by an approximate direct current to the input capacitor, and the filter capacitor acts as a broadband energy storage function. Similarly, the output filter capacitor is also used to store the high frequency energy from the output rectifier, and to eliminate the DC power of the output load circuit. Therefore, the input and output filter capacitance of the terminal is very important, input and output current loop should only be connected to the power supply from the junction of the filter capacitor respectively.

   Input and output circuit settings and connections for the entire printed circuit board, is very important, whether it is reasonable or not will directly relate to the size of electromagnetic interference. If the connection between the input and output circuit and the power switch and the rectifier circuit can not be directly connected with the connecting end of the capacitor, the AC energy will be radiated into the environment by the input or output filter capacitor. Power switch circuit and AC rectifier AC circuit contains high amplitude trapezoidal current, high harmonic components of the current, the frequency far outweigh switch frequency and peak amplitude can be up to five times the height of the input and output DC current amplitude, the transition time is about 50ns. These two loops are most likely to produce electromagnetic interference, so they must be distributed before the other printed wiring in the power supply.

   In the LED switch power supply input, the input circuit, each circuit is composed of three main components, the three components are filter capacitor, power switch or rectifier, inductor or transformer. These three important elements should be placed adjacent to each other, adjusting the position of the components to make the current path as short as possible. A switch power source for the layout of best method and electrical design similar, the optimal design process are as follows: place transformer, power supply design, switched current circuit, design output current rectifier circuit, connected to the AC power supply circuit, control circuit, design of input current source loop and input filter.


 

(Source: Inside information)

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