| 摘要 |
PURPOSE:To prevent the generation of color shading at the upper part of a reproduced screen for an optical video disk player, etc., by varying the operating state of a feedback path that limits an excessive driving current of an actuator coil when a truck has a jump. CONSTITUTION:The signal showing the fluctuation component of a time axis is amplified 3 and 4 through an impedance circuit 2 and then supplied to an actuator 5 from an input terminal 1. A driving current is detected by a resistance 6 and then fed back to the input of the amplifier 3 via a feedback impedance 7 to ensure a stable operation. At the same time, an excessive driving current is limited via a feedback amplifying circuit 8. A command signal is supplied to an input terminal 12 when a track has a jump and then fed to a switching transistor TR15 via a waveform shaping circuit 13. As a result, the TR15 is turned off and the feeback path is made inactive by the circuit 8. Therefore it is possible to follow quickly the phase of an information signal of a jumped information track when a track has a jump. This can obtain a reproduced picture free from the color shading. |
