| 摘要 |
PURPOSE:To prevent the driving operability of a vehicle driver from being impaired, and in addition, to prevent thermal breakdown of a circuit, etc., from occurring by dividing a range extending over from a steady using state to a non-steady using state into three specified operating regions. CONSTITUTION:The circuit is constituted of a power MOSFET 1, load 2, a current miller MOSFET 3, a shunt resistor 4, a current detection circuit 5, a PWM(pulse width modulation) circuit 6, and a booster circuit 7. Then, three kinds of the operating regions are provided according to a current to flow in the power MOSFET 1, and a semiconductor element is turned to an ON state in the case of the rated range of this current, and in the case of a prescribed range in which protection against an overcurrent is requested, it is shifted to PWM control, and further, in the case of shortcircuit or where an extraordinarily large current flows, it is turned into a complete OFF state. Thus, in the case where it is applied to a semiconductor switch etc., for the head-light of a vehicle, the driving operability of the driver is never impaired, and in addition, the thermal breakdown or the like is prevented from occurring. |
