Your LED Switch Power Should Do This For PCB Loop Design
- Nov 03, 2018-
In a PCB board commonly used in switching power supply, each switching power supply usually has four current loops, which are input signal source current loop, power switch ac loop, output rectifier ac loop and output load current loop.The input circuit charges the input capacitance through an approximate dc current, and the filter capacitance mainly ACTS as a broadband energy storage.Similarly, the output filter capacitor is used to store high frequency energy from the output rectifier while eliminating dc energy from the output load loop.Therefore, the terminals of the input and output filter capacitors are very important. The input and output current loops should only be connected to the power supply from the terminals of the filter capacitors.
The setup and connection of the input and output circuits is very important for the entire printed circuit board, and the reasonableness is directly related to the magnitude of the electromagnetic interference.If the connection between the input and output circuits and the power switch and rectifier circuits cannot be directly connected to the capacitor's terminal, the ac energy will be filtered by the input or output capacitors and radiated to the environment.The ac circuit of power switch and rectifier contains high-amplitude trapezoidal current, in which the harmonic component is very high, the frequency is much higher than the switching base frequency, the peak amplitude can be as high as 5 times of the amplitude of continuous input and output dc current, and the transition time is usually about 50ns.These two circuits are most prone to electromagnetic interference, so these ac circuits must be deployed before any other printed wiring in the power supply.
In the input and input circuits of the LED switching power supply, each circuit is composed of three main components: filter capacitor, power switch or rectifier, inductance or transformer.These three important elements should be placed next to each other, adjusting the position of the elements so that the current path between them is as short as possible.The best method to establish the layout of switching power supply is similar to the electrical design. The optimal design process is as follows: put transformer, design power switch current loop, design output rectifier current loop, control circuit connected to ac power supply circuit, design input current source loop and input filter.