Feature: Electronic design


Figure 6: LED current waveform of the test circuit shown in Figure 5


A circular return trace is provided for the total LED


current around the PCB; thus, the magnetic fields of the traces cancel each other. Also, the current loop area is decreased to prevent more magnetic fields forming. A fairly uniform LED current is measured through the second revised design; see Figure 8. Tis design does not require additional snubbers or filter


Figure 7: Green mask (left) and copper layer (right) scheme of the PCB design with symmetrical LED placement


circuits. It successfully solves the EMI problems through a simple layout configuration and, yet, the circuit’s performance is improved without increasing its cost or PCB size.


Figure 8: Current and voltage waveform of the PCB design in Figure 7


20 March 2022 www.electronicsworld.co.uk


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