| 摘要 |
PURPOSE:To prevent a fault picture from being displayed, by connecting a resistor in series with a diode which is turned on with a power supply switched off and a discharge current of a capacitor flows therethrough, for relinquishing almost instantly a picture with the power supply switched off. CONSTITUTION:When a main power supply +B1 is applied, a capacitor C1 is charged to slow down the leading of a control voltage for luminance adjustment. Further, when a power supply +B2 is changed from the transient state to the steady-state, the charging voltage of the capacitor C1 is equal to a voltage lower by about 0.4V than the control voltage for luminance adjustment, allowing to turn off diodes D1, D2. When the power supply +B1 is interrupted, the voltage of the power supply +B1 is decreased, the control voltage for luminance adjustment is decreased, and the charging voltage of the capacitor C1 is decreased, the diode D1 is turned on. Since the discharge current is limited with a resistor R9 although the capacitor C1 starts discharging, the positive feedback operation progressing the voltage decrease of the power supply +B2 is limited. |
