Patent ID: 8570102

Claim:
A switching amplifier operated by a first power supply voltage, a second power supply voltage, and a reference potential as an electric potential between the first power supply voltage and the second power supply voltage, the switching amplifier comprising: a pulse-width modulating circuit for outputting a pulse width modulation signal according to an input signal; a logic power supply circuit for generating a logic power supply voltage with respect to the reference potential based on the first power supply voltage with respect to the reference potential, and supplying the generated logic power supply voltage to the pulse-width modulating circuit; and a switching output circuit that is operated on/off according to the pulse width modulation signal, wherein the pulse-width modulating circuit includes; a pulse generating unit being operated by the reference potential and the logic power supply voltage, the pulse generating unit having a first accumulating unit, a second accumulating unit, a first output element and a second output element, the pulse generating unit outputting the pulse width modulation signal from at least one of the first output element and the second output element by charging the first accumulating unit with a first electric current and charging the second accumulating unit with a second electric current, a constant current circuit for generating a constant current, and when the switching amplifier transitions into an off state, reducing the constant current according to a reduction in the reference potential with respect to the second power supply voltage, a current distribution unit for controlling a distribution ratio between the first electric current and the second electric current based on the input signal and the constant current, and controlling a time required for charging the first accumulating unit with the first electric current and a time required for charging the second accumulating unit with the second electric current so as to control a pulse width of the pulse width modulation signal, the switching amplifier further comprising: a power supply controller for, when the switching amplifier transitions into a power-off state, forcibly reducing the reference potential with respect to the second power supply voltage.