| 摘要 |
A beam current limiting (BCL) control apparatus for a digital television system includes a control unit for controlling the reference voltage for the analog-to-digital converter (ADC), which converts the analog composite video signal, including both luminance and chrominance components, to corresponding digital samples, so as to reduce excessive beam currents. A switching circuit prevents the reference voltage from being changed in response to the beam current during horizontal blanking intervals so as to inhibit interference with digital synchronization component detection and automatic chrominance control. A clamping circuit is coupled to the ADC to inhibit the conversion of portions of the composite video signal extending from the black level (0 IRE units) to the sync tips from being affected by the BCL operation. This inhibits the BCL operation from adversely affecting the reproduction of details in dark portions of an image. |
