| 摘要 |
PURPOSE:To avoid a radiation of in electric wave an the out of synchronization from a radio device using a PLL circuit, by discontinuing the operation of a voltage control oscillator for the period during which the step-out state of the PLL circuit is detected. CONSTITUTION:When the electric power is supplied to a PLL circuit, the phase error voltage given from the phase comparator 18 is applied to the input terminal 34 of the step-out detection control circuit 21. Thus the transistors TR1 and TR2 are turned on and off respectively for a certain period of the rise time of the quartz oscillating circuit 15. However, the state reverses after a certain time to turn on the TR2, and the electric power is supplied to the voltage control oscillator 13 through the output terminal 35 of the TR2. The oscillator 13 delivers the oscillation frequency controlled by the phase error voltage that passed through the phase comparator 11 and the low pass filter 12. When a fault is caused to the circuit, the voltage is lowered for the phase error voltage input terminal 34 of the circuit 21. Then transistors TR1 and TR2 are turned on and off respectively after a prescribed time. As a result, the supply of the electric power is discontinued to the oscillator 13 to stop the output. |
