| 摘要 |
<p>An automatic brightness adjusting circuit for a cathode ray tube is disclosed which includes a video signal source from which a video signal is derived, a cathode ray tube having an electrode normally supplied with the video signal derived from the video signal source, a reference signal source for producing a reference signal, a signal processing circuit between the video signal source and the cathode ray tube, a switching circuit for selectively supplying either the video signal derived from the video signal source or the reference signal to the signal processing circuit, the switching circuit supplying the reference signal to the signal processing circuit during a brightness adjusting period, a control signal generator connected to the signal processing circuit for supplying the latter with a control signal the level of which varies gradually during the brightness adjusting period, a level detector connected to the cathode ray tube for detecting a signal level at its electrode, and a control circuit responsive to the level detector for stopping the control signal generator from varying the control signal level and for actuating the switching circuit such that the latter supplies the video signal to the signal processing circuit when the detected signal level of the electrode exceeds a predetermined value. The adjusting circuit thus constructed can operate stably and perform the adjusting operation in a short period of time.</p> |
