The real-time fault diagnosis of optocoupler in switching mode power supply

Optocoupler is applied to isolate the control loop to the main power stage, and transfer feedback signal in the negative feedback loop of SMPS. But due to surface deterioration and the generation of crystal defects, optocoupler would degrade and result the decrease of the CTR. Once the CTR decline to a threshold, Optocoupler would degrade to failure, leading to the unstability of SMPS. The paper presents a precise and reliable fault diagnosis method to optocoupler in SMPS. According to the method, we can realize real-time and online fault diagnosis to optocoupler by monitoring the Current Transfer Ratio and finishing health assessment to optocoupler by analyzing the degeneration of CTR.