| 摘要 |
PROBLEM TO BE SOLVED: To provide a power amplifier circuit which can also detect a DC output caused by an abnormality occurred at a driver stage. SOLUTION: The power amplifier circuit includes a PWM circuit 10, a driver section 13 performing switching power amplification depending on an output signal from the PWM circuit 10, a section for generating a voltage synchronizing with the output voltage from the driver section 13, a voltage drop section for dropping a voltage (at a BSP terminal 17) synchronizing with the output voltage from the driver section 13 according to a predetermined time constant when the output voltage from the driver section 13 goes above a predetermined duty (e.g. on duty near 100%), and a DC output protection circuit 21 for deciding that a DC voltage is outputted if a voltage dropped at the voltage drop section is below a predetermined value when the output signal from the PWM circuit 10 has a high level. COPYRIGHT: (C)2009,JPO&INPIT
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