| 摘要 |
PROBLEM TO BE SOLVED: To provide an overload protection circuit for a digital audio amplifier in which a secure protecting operation for an overload state is realized at low cost by detecting both polarities. SOLUTION: An overload protection circuit 30 for a digital audio amplifier circuit 50 equipped with a shut-down terminal SD is provided with an overload detection circuit 8 having an impedance bridge 10 composed of an output current detection resistor R3 between an output terminal OUTPUT and a load R4, serially connected two resistors R1 and R2 balanced with a resistance ratio of R3 and R4 and a diode D2, and a transistor Q2 to be turned on by generating a difference signal Vs2 only when R4 is changed smaller to be unbalanced, and a similar overload detection circuit 9. Only when the load R4 is turned into overload state with respect to both the positive and negative polarities, a detection signal S resulting from ON of the transistor Q2 or Q1 is inputted to the shut-down terminal SD to turn off a switching transistor on a power stage. COPYRIGHT: (C)2004,JPO
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