| 摘要 |
To provide an overcurrent protection apparatus which can surely protect a load circuit from an overcurrent with a simple configuration. Supposing that the temperature increasing amount of a semiconductor element caused when the semiconductor element is turned on is &Dgr;Tch, the on-resistance value of the semiconductor element (T1) is Ron, the thermal resistance value of the semiconductor element (T1) is Rth_f, the temperature increasing amount of a connecting wiring is &Dgr;Tw when a current flows into the connecting wiring (WL), the resistance value per unit length of the connecting wiring is Rw, and the thermal resistance value per unit length of the connecting wiring is Rth_w, &Dgr;Tch is obtained based on an expression of &Dgr;TW/&Dgr;Tch=Rth_w/Rth_f*Rw/Ron with respect to the temperature increasing amount &Dgr;Tw not exceeding a difference between the upper limit of the permissible temperature of the connecting wiring (WL) and the upper limit of an operational peripheral temperature, then a voltage Vds is obtained based on an expression of &Dgr;Tch=Rth_f*Vds2/Ron with respect to the &Dgr;Tch thus obtained, and the voltage Vds thus obtained is set as a determination voltage. |
