| 摘要 |
PURPOSE:To avoid OFF-control for a power transistor by surge current by controlling a current detection circuit OFF only in the period of the generation of surge current generated by the ON action of the power transistor. CONSTITUTION:When the signal is outputted from a control circuit 26 and a power transistor 22 is controlled ON, a surge current flows to a current detection resistance 24 at the beginning of turning ON the transistor 22. On the other hand, the output of the control circuit 26 is inputted into an inverter circuit 36 with the delay for the period of surge current generation by the delay element of an integrating circuit. The voltage across the resistance 24 is thereby sampled to a sampling capacitor 29 in the period excepting the surge current generation period. If an excess current flows to a DC motor 23, a transistor 33 is actuated ON with the output of a comparator 32 and the power transistor 22 is controlled OFF.
|
