This paper presents a comprehensive online condition monitoring algorithm for power semiconductor devices. The proposed algorithm utilizes the voltage measurement between the collector and emitter of power semiconductor devices to fully monitor the performance and state of the device. The proposed algorithm provides four different detection and monitoring conditions of the device; these four elements are open-circuit fault detection, short circuit fault detection, overheating fault detection, remaining useful lifetime estimation. Compared to the previously addressed approaches in the literature, the proposed algorithm provides full state monitoring and detection of the device using only one sensed quantity. The collector-emitter voltage measurement of the device is chosen for implementing the proposed algorithm for its generality as it can be applied to various semiconductor devices technologies. Additionally, the proposed algorithm provides the advantages of simple implementation, comprehensive condition monitoring, and low cost. The implementation of the full proposed condition monitoring system is provided in the paper with case study application to boost DC-DC converter system. The results and comparisons of the proposed algorithm with previous strategies verify the feasibility of the proposed algorithm.