| 摘要 |
A voltage level detector ( 8 ) activates itself through monitoring the voltage level (V<SUB>STB</SUB>) 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 (V<SUB>STB </SUB>and V<SUB>out</SUB>) at the standby pin ( 5 ) and the output terminal ( 3 ) during power-up. Upon detection of the voltage level (V<SUB>STB</SUB>) reaching a first threshold level (V<SUB>th1</SUB>) 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 (V<SUB>STB</SUB>) at the standby pin ( 5 ) during power-up. Upon detection of the voltage level (V<SUB>STB</SUB>) reaching a second threshold level (V<SUB>th2</SUB>>V<SUB>th1</SUB>), the recovery block ( 82 ) deactivates the cutoff signal generating block ( 83 ). The cutoff signal generating block ( 83 ) sends a cutoff signal (Sc) to a protection switch block ( 71 ) as a request for turn-off of protection switches ( 7 A) on activation, and on the other hand, terminates the sending of the cutoff signal (Sc) on deactivation.
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