Characterization of Electromagnetic Susceptibility in Optocouplers Exposed to Different Interference Waveforms

An optocoupler is a widely used electrical control switching device that falls under the direct-current (DC) on/off category from a functional perspective. The datasheet for optocouplers typically provides DC characteristics and the delay time associated with the on/off switching transition. However, it often lacks detailed information regarding the device’s electromagnetic behavior and performance at radio frequencies (RF). To characterize the electromagnetic susceptibility (EMS) of optocouplers, we propose a new method that injects interference signals with different waveforms through direct power injection (DPI). This paper focuses on the EMS of two specific optocouplers, P521GB and PC817, which exhibit significant susceptibility to electromagnetic interference. The experimental results show that when the interference signal intensity exceeds the susceptibility threshold of the optocoupler, its operational state is altered, and the output voltage drops to a low level. Additionally, we present the susceptibility thresholds of the optocouplers under varying interference conditions. This study provides valuable insights into the electromagnetic susceptibility characteristics of optocouplers and offers data and theoretical support for the electromagnetic protection design of electronically controlled switching systems composed of optocouplers, which is of significant value.