| 摘要 |
The speed of the disc drive of a CD-player is regulated by means of a phase-control circuit, which is set manually during production. In order to avoid tiresome manual setting during production as well as speed fluctuations, resulting in deterioration of the sound reproduction due to aging of the components and to variations in temperature, setting is performed automatically. To this end, the controller (R) of the phase-control circuit is separated from the voltage-controlled oscillator (VCO). The output of the voltage-controlled oscillator (VCO) is connected to the first input of a phase-compensation device (P2), the reference frequency (BF) being directed towards its second input. A microprocessor (MP), the input (E) of which is connected to the output of the phase-compensation device (P2) and the output (A1) of which is connected to the input of the voltage-controlled oscillator (VCO), modifies the tension at its output (A1) until the frequency at the output of the voltage-controlled oscillator (VCO) corresponds with the reference frequency (BF). The microprocessor (MP) retains said tension. The controller (R) is then reconnected to the voltage-controlled oscillator (VCO). The phase-control circuit is now set and operational. Setting of a CD-player can for example be performed every time it is switched on or another CD is being played, or during a pause between two tracks of music. Said phase-control circuit is particularly suited for a CD player. |
