How to design LED switching power PCB circuit
The research and development speed of LED switching power supply has seen a significant technological leap in recent years, and the speed of new product upgrading has also been accelerated. As the last link design, PCB design also is very important, because once in this link problems, then will probably LED switching power supply of the whole system to produce more electromagnetic interference, stability and safety of power supply work also will be adversely affected. So what is the right design for PCB?
Through the last few years LED power supply components layout research and market practice proved that even in the early stage of development by the circuit principle diagram of the design is very correct, once the PCB design problems, however, will be harmful to the reliability of electronic devices, for example due to power supply, ground of not considerate, will make the product performance, so in the design of PCB, you need to use the right method.
In a commonly used to switch power supply PCB board, usually every switching power supply with four current loop, they respectively are input signal source current loop, the exchange of power switch circuit, output rectifier circuit, output load current loop. The input circuit is charged to the input capacitor through an approximate dc current, and the filter capacitance mainly ACTS as a broadband energy storage. Similarly, the output filter capacitance is used to store the high frequency energy from the output rectifier while eliminating the dc energy of the output load loop. Therefore, the input and output filter capacitors are very important, and the input and output current circuits should only be connected to the power supply from the connection end of the filter capacitor.
The setting and connection of input and output circuits is very important for the entire printed circuit board, and its reasonable or not is directly related to the size of electromagnetic interference. If the input and output circuit and the power switch, the connection between the rectifier circuit can not attached directly to the terminal of capacitor, energy will be composed of input or output filter capacitor and radiation to the environment. Power switch ac circuits and the communication of the rectifier circuit contains high of trapezoidal current, the current in the harmonic components is very high, its frequency is greater than the switch base frequency, the peak amplitude can be as high as 5 times for the amplitude of the input, output, the dc current, transition time is usually about 50 ns. The two circuits are most likely to produce electromagnetic interference, so the communication loops must be made before other printed wiring in the power supply.
In LED switching power supply, input, input circuits of each loop is composed of three main components to, these three components are respectively filter capacitance, the power switch or rectifier, inductor or transformer. These three important components should be placed adjacent to each other, adjusting the position of the elements so that the current path between them is as short as possible. One of the best ways to build switching power supply layout and its similar electrical design, optimal design process is as follows: place the transformer to design the power switch to design the output rectifier current loop, current loop is connected to the ac power circuit and control circuit of the input current source circuit and the input filter design.