Electrical load detection for SSPC regardless of power source switching status

The existing solid state power controller (SSPC) can output several statuses of loads and power sources, but the output statuses are not enough to detect load connection status, especially when the power source is switched off. In this paper, a detection circuit is designed in SSPC to judge the load connection status effectively, regardless of whether the power source is switch on or off. The circuit is constructed by three modules of which mechanism and logic state truth table are presented. Moreover, the delay characteristic of resistor-capacitor (RC) circuit is analyzed and formulated by a theoretical way. Experiment results show that the presented method can detect the load status accurately whether the electric power source system is powered on or off, which is more effective than existing SSPC. Additionally, it is verified that the theoretically calculated voltage in RC delay circuit is much closer to the actual measured voltage than the conventional approach.