Patent ID: 7064945
Filing Date: 2006-06-20
Classification: H02H

Abstract:
1. A capacitive load driving circuit for supplying a charging-current to a capacitive load and withdrawing a discharging-current from said capacitive load, the load driving circuit comprising: an output circuit which comprises a power supply terminal, a ground terminal, and an output terminal connected to said capacitive load, and which performs a charging-current supplying operation of supplying a charging-current from said power supply terminal to said capacitive load and a discharging-current withdrawing operation of withdrawing a discharging-current from said capacitive load to said ground terminal; and an overcurrent protection circuit that detects a short circuit between said output terminal and said ground terminal so as to stop or suppress said charging-current supplying operation, and that detects a short circuit between said output terminal and said power supply terminal so as to stop or suppress said discharging-current withdrawing operation, wherein: said output circuit selects any one of said charging-current supplying operation and said discharging-current withdrawing operation depending on the state of a control input signal, said output circuit comprises: a first NPN transistor the collector of which is connected to said power supply terminal and the emitter of which is connected to said output terminal; and a first PNP transistor the collector of which is connected to said ground terminal and the emitter of which is connected to said output terminal, and said overcurrent protection circuit comprises: a second NPN transistor the collector of which is connected to the base of said first NPN transistor, and the emitter of which is connected to said output terminal, and further the base of which is connected to a first voltage supply for-generating a predetermined electric potential higher than the electric potential of said ground terminal; and-a second PNP transistor the collector of which is connected to the base of said first PNP transistor, and the emitter of which is connected to said output terminal, and further the base of which is connected to a second voltage supply for generating a predetermined electric potential lower than the electric potential of said power supply terminal.