| 摘要 |
PURPOSE:To ensure the accurate stabilization of levels and to simplify the constitution of a level stabilizing circuit, by inserting reference signals having the reference levels corresponding to black and white levels into a TV signal and controlling these reference signals with a common circuit so that they are set at a constant level. CONSTITUTION:The reference signals S1 and S2 are set at a reference level E1 corresponding to a black level and at a reference level E2 higher than the level E1 by DELTAE. A TV signal SV to which the signals S1 and S2 are inserted is supplied to a video output circuit 40 via an AGC circuit 20 and a control circuit 30 for DC bias. A part of the video output is supplied to a level control circuit 60 to perform the control so that the level difference between signals S1 and S2 is always constant. Furthermore a level control circuit 70 performs the control so that a beam current IK flowing to a CRT 50 when the signal E2 is inserted is set at a constant level. Therefore the level difference DELTAE is set constant by the circuit 60, and the level E2 is set constant by the circuit 70. As a result, both black and white levels are controlled at one time and can be stabilized. |
