| 摘要 |
PURPOSE:To flow a large current when there is a margin in the temperature of a junction part, by varying a current limit value and an overcurrent in accordance with the temperature of the junction part while monitoring the temperature of the junction part of a semiconductor switching element by detection or estimation. CONSTITUTION:A temperature TF of a radiating fan 2 of a semiconductor switching element 1 is detected by a thermosensitive element and is subjected to level conversion in a signal converter 6 in consideration of the saturation head impedance between the junction part and the radiating fan 2 to obtain a stationary junction part temperature signal T10. Meanwhile, a rated current reference signal IRN set by a setter 3 and a current signal IF detected by a current detector 4 are compared with each other, and a differential current DELTAI is given to function generator 5, where a current-temperature characteristic is determined, to obtain a momentary junction part tempeature rise signal DELTAT due to a momentary current. This signal and the stationary junction part temperature signal T10 are added to obtain a junction part temperature signal TJ, and a current limiting signal ILIMT is obtained through a function generator 7 where a junction part temperature-latching current characteristic is determined. Thus, the current limit value and the overcurrent detection value are varied in accordance with a latching current value changing momentary with the junction part temperature TJ, and a large current is flowed at a short time, the start time, or the like especially. |
