Abstract: A method of controlling the charge of the bootstrap capacitor during light load or no load conditions for a non-synchronous type of DC-DC converter consists of bootstrap capacitor voltage detector, light load detector and secondary switch controller. By turning on the secondary switch during the off-time of the power transistor when the bootstrap voltage is lower than the required value under light load condition, the bootstrap capacitor voltage will be able to charge back to the required value, yet minimizing the minimum current requirement for the DC-DC converter.

Abstract: A voltage level detector (8) activates itself through monitoring the voltage level (VSTB) at a standby pin (5) during power-up of an audio power amplifier (10), and can detect fault conditions of an output block (2), such as a short to ground at an output terminal (3), in contrast to conventional protection circuits that can operate only after power-up. In a voltage level detector (8), a second short-to-ground detection block (81) monitors the voltage levels (VSTB and Vout) at the standby pin (5) and the output terminal (3) during power-up. Upon detection of the voltage level (VSTB) reaching a first threshold level (Vth1) and a short to ground at the output terminal (3), the second short-to-ground detection block (81) activates a cutoff signal generating block (83). The recovery block (82) monitors the voltage level (VSTB) at the standby pin (5) during power-up.