An Online Proactive CTR Monitoring Method for Optocoupler in Automotive Auxiliary Converter

Automotive auxiliary converter empowers the electronic system, the failure of which will affect the system performance. As a critical component in the feedback loop of the converter, real-time health monitoring for optocoupler is of great importance. The degraded optocoupler mainly shows a falling current transfer ratio (CTR). This article proposes an online proactive CTR monitoring method for optocoupler via voltage measurement of critical nodes. The monitored CTR can indicate the health condition of the optocoupler. First, the principle of a boost- LLC converter is analyzed in detail. Then, the influences of degraded CTR on the feedback loop are derived. An online proactive CTR monitoring scheme is introduced. The realization of voltage measurement, signal filtering, wireless communication, and time synchronization are in two independent embedded systems. CTR will be calculated in the local server and be stored in the local database. The proposed method can monitor CTR for both unaged and aged optocouplers. Effects of switching frequency and ambient temperature are also incorporated for online CTR monitoring. Experimental results validate the superiority of this online proactive monitoring method. The method could be extended and further evaluate the health condition of the overall automotive auxiliary converter.