Patent ID: 8760832

Claim:
A load circuit protection device for protecting a load circuit including a DC power supply, a semiconductor switch and a load, comprising: a current detection section that detects a current flowing into the semiconductor switch; a voltage detection section that detects a voltage generated at an electric wire coupling between the DC power supply and the semiconductor switch; a threshold current adjusting section that adjusts a threshold current for determining whether or not an overcurrent flows into the load circuit according to the voltage detected by the voltage detection section; a turning-off control section that determines whether or not a current detected by the current detection section reaches the threshold current and outputs a turning-off signal when it is determined that the detected current reaches the threshold current; and a driving control section that switches an on/off state of the semiconductor switch based on an external input signal and turns off the semiconductor switch when the turning-off signal is supplied thereto, wherein the threshold current adjusting section reduces the threshold current according to reduction of a voltage detected by the voltage detection section when the voltage detected by the voltage detection section is reduced and sets an upper limit voltage and a lower limit voltage as to a voltage detected by the voltage detection section, and the threshold current adjusting section adjusts the threshold current in a linear function manner in a voltage region between the lower limit voltage and the upper limit voltage and maintains the threshold current to a constant value in a voltage region equal to or lower than the lower limit voltage and in a voltage region equal to or greater than the upper limit voltage.