| 摘要 |
<p>A luminance signal generation circuit with single clamp and horizontal synchronization pulse generation circuit generates a separate luminance video signal Y, representing RGB input signals, and having a horizontal synchronization pulse. During a burst period, the single clamping circuit (30) is enabled and compares the separate luminance signal Y to a reference signal. A difference signal, representing the difference between the separate luminance signal Y and the reference signal, is used to adjust a blanking level of the RGB input signals until the blanking level of the separate luminance signal Y is equal to the reference signal. During the non-burst periods, the single clamping circuit (30) is disabled and a Y-matrix circuit (32) combines the RGB input signals into the separate luminance signal Y. A horizontal synchronization pulse generation circuit (36) generates a horizontal synchronization pulse to be added to the clamped separate luminance signal Y. During the horizontal synchronization period, a current is switched through a path resistor (54) and used to generate the voltage level of the horizontal synchronization pulse. The voltage drop across the path resistor (54) during the horizontal synchronization period is applied directly to the outpout video signal thereby generating a horizontal synchronization pulse. The current switched through the path resistor (54) is generated by a voltage drop across a current resistor (64). The ratio of the path resistor (54) to the current resistor (64) is matched, allowing the required signal accuracy to be achieved in the voltage drop across the path resistor (54) and generating the appropriate voltage drop across the path resistor (54) according to the current flowing through the current resistor (64).</p> |
