Patent ID: 6191958
Filing Date: 2001-02-20
Classification: H02M,H04N

Abstract:
An apparatus for controlling a drive transistor, comprising:a switching controller comparing a reference voltage with a signal provided externally, and removing noise;a switch comprising a first switch coupled to a constant voltage and a second switch having a first terminal coupled to a first terminal of the first switch and having a second terminal grounded, either the first or second switch being turned on according to an output of the switch controller; anda base current supplier comprising diodes and a capacitor, the base current supplier supplying, when the first switch is turned on and a constant current is supplied from the constant voltage, the constant current to a base terminal of the drive transistor through the diodes so that the drive transistor is turned on and the capacitor is simultaneously charged as much as a forward voltage drop of the diodes, and discharging, when the second switch is turned on, the capacitor and turning off the drive transistor, wherein the base current supplier includes an anode of one of the diodes coupled to the first and second switches, a cathode coupled to the base terminal of the drive transistor, and the capacitor coupled to the diodes in parallel.