| 摘要 |
PROBLEM TO BE SOLVED: To provide a class D amplifier in which electromagnetic interference is suppressed by reducing the peak level of harmonic noise incident to switching operation of a power switch in the class D amplifier. SOLUTION: A voice out-band signal 2 is entered to the frequency conversion circuit 3a in the PWM signal generating section 3 of a class D amplifier to obtain a rectangular wave signal where a PWM reference signal 1 is frequency modulated by the voice out-band signal 2. A triangular wave generating circuit 3b generates a triangular wave signal frequency modulated by the voice out-band signal 2 using the rectangular wave signal. The triangular wave signal and an analog voice signal are entered to a comparison circuit 3c and a PWM signal is obtained by frequency modulating a PWM carrier frequency by the voice out-band signal 2. After power amplification is performed by a power switch 6, a PWM demodulation output 8 is obtained from a filter 7. COPYRIGHT: (C)2005,JPO&NCIPI
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