| 摘要 |
#CMT# #/CMT# The backlight has LEDs (12) arranged in lines, connected in series, and fed by a power source. A controllable switching unit is provided for influence of diode currents of the LEDs. An optocoupler (14) controls the switching unit. The switching unit includes transistors (10, 11), where one of the transistors is connected in series to the LEDs and another one of the transistors is in series to a diode (13). The LEDs and the diode include same characteristic curves and internal resistance, and are operated by the transistors in push-pull. #CMT#USE : #/CMT# Backlight for a LCD display for displaying an image. #CMT#ADVANTAGE : #/CMT# The controllable switching unit is provided for influence of the diode currents of the LEDs, and the optocoupler controls the switching unit, thus controlling local brightness of the LCD display in simple manner. The backlight is controlled with a small response time. The LEDs and the diode include the same characteristic curves and the internal resistance, thus rapidly and independently controlling the LEDs. The backlight achieves constant energy dissipation. #CMT#DESCRIPTION OF DRAWINGS : #/CMT# The drawing shows a circuit diagram of a LED-bypass circuit. 10, 11 : Transistors 12 : LEDs 13 : Diode 14 : Optocoupler 15 : Control signal. |
