| 摘要 |
PROBLEM TO BE SOLVED: To provide PWM modulator circuit variable of a maximum modulation degree which reliably charges up, at starting a class D amplifier, a floating power source of an output circuit to start this amplifier. SOLUTION: The PWM modulator circuit 20 has an integrator circuit 14 with inputs of input analog signals Vin and a reference voltage Vref, a PWM comparator 17 with inputs of the output Vo of the intetegrator circuit 14 and a triangular wave Va, and a negative feedback loop 18 for feeding back a PWM output PWM2 of the PWM comparator 17 to the input of integrator circuit 14. Further, the circuit comprises a means K for limiting maximum signal amplitudes f1, f2 of the output Vo of the integrator circuit 14 to limit the maximum modulation degree of the PWM output PWM2 according to an external control signal S2. The maximum modulation degree limiting means K is connected between the output of the integrator circuit 14 and the input of the PWM comparator 17. COPYRIGHT: (C)2006,JPO&NCIPI
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