Development of fast electronic over-current protection circuit using current-adjustable sensing method

Traditional methods to protect the electric-driven facilities from overload or short circuit usually use electronic breaker or fuse. However, the reaction time for these devices normally require more than 0.1 s that may be not sufficiently fast to disconnect the power supply for protection. For this reason, this article develops a fast and simple electronic over-current protection circuit based on the current-adjustable sensing method. First, the load current is sensed and converted to a voltage signal using Hall sensor. Then, the signal is amplified and compared with the predefined threshold value, that is, the maximum tolerance current, using amplifier and comparator, respectively. The timer will generate a pulse signal input to the trigger circuit for rapidly switching off alternating current power once the load current exceeds the tolerance value. The alternating current power disconnection can continue for a period of time set by the timer in advance. The experimental results prove that the proposed circuit takes less than 10 ms and it is significantly fast to react for facility protection in time.