How to design the PCB circuit of LED power supply?

How to design the PCB circuit of LED power supply? The research and development of LED power supply is very fast, and the design of PCB is particularly important as the last design link. Because once PCB problems occur, it is likely to cause electromagnetic interference to the entire LED switching power supply system, affecting the stability and safety of the power supply. How to design PCB is a problem that every LED driver power technical engineer needs to consider

In PCB boards commonly used for switching power supply, each switching power supply usually has four current circuits, namely input signal source current circuit, power switch AC circuit, output rectifier AC circuit and output load current circuit. The input circuit charges the input capacitor through the approximate DC current, and the filter capacitor mainly plays the role of broadband energy storage. Similarly, the output filter capacitor is also used to store the high-frequency energy of the output rectifier and eliminate the DC energy of the output load circuit. Therefore, the terminals of the input and output filter capacitors are very important, and the input and output current circuits should be connected to the power supply only from the terminals of the filter capacitors.

The setting and connection of input and output circuits are very important for the whole printed circuit version, and their rationality will directly affect the size of electromagnetic interference. If the connection between input circuit, output circuit, power switch and rectifier circuit cannot be directly connected to the terminal of capacitor, AC energy will be radiated to the environment by input or output filter capacitor. The AC circuit of the power switch and the AC circuit of the rectifier contain high trapezoidal current, high harmonic components, and the frequency is far greater than the basic frequency of the switch. The peak range can be up to 5 times of the range of continuous input and output DC current, and the transition time is usually about 50ns. These two circuits are most likely to generate electromagnetic interference, so these AC circuits must be arranged before other printed lines in the power supply are routed.

In the input and input circuit of LED switching power supply, each circuit is composed of three main components: filter capacitor, power switch or rectifier, inductor or transformer. The three important parts shall be placed adjacent to each other, and the position of the parts shall be adjusted to make the current path between them as short as possible. The best way to establish a switching power supply layout is similar to its electrical design. The optimal design process is as follows: placement of transformer → design of power switch current circuit → design of output rectifier current circuit → control circuit connected to AC power circuit → design of input current circuit and input filter.

A large number of practice results show that even if the circuit schematic diagram of LED driver power design is very correct in the early stage of R&D, once PCB design problems occur, the reliability of electronic equipment will be adversely affected. For example, the interference caused by the inconsiderate power supply and ground wire will reduce the performance of the product. Therefore, we must take the correct method when designing PCB boards. The above is some of our experience, and I hope it can be helpful.

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