| 摘要 |
PURPOSE:To stabilize the operation of an audio component, by supplying a carrier signal from a high-precision master oscillating circuit which uses a crystal oscillator to the modulating circuit of a switching type power source circuit. CONSTITUTION:A commercial AC voltage is supplied through a switch 2 to a rectifying circuit 4 to be rectified into a DC voltage, which is supplied to the series circuit of the primary coil of a transformer 5 and a switching transistor TR6. This DC voltage is supplied to a PWM modulating circuit 24 through a starting circuit 11 to turn on and off the TR6 by PWM pulses from the circuit 24. The output of the transformer 5 is rectified by a rectifying circuit 7 into a DC voltage, which is supplied as the operating voltage of a load circuit 130, etc.; and a DC voltage rectified by a rectifying circuit 12 is supplied to the master oscillating circuit 30, frequency dividing circuit 39, circuit 24, etc. The circuit 30 is a highly stable oscillator using a crystal oscillator and its output is frequency-divided and supplied to the circuit 24 and a PWM modulating circuit 132 as the carrier signal. |
