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Return to BlogElectroluminescent Inverter Form of LCD Backlight
Posted Jan 27, 2012 at 11:27 am
Figure 1
The idea behind the construction of this project is to formulate an LCD backlight with the use of an electroluminescent inverter.
The electroluminescent backlights are more efficient and provide more uniform lighting the LEDs. However, electroluminescent backlights would require complicated circuitry since they are hard to drive. This is because they typically require around 100V AC with a frequency around 150Hz.
Although the circuit is running a logic 5V DC, the high voltages can still be generated by using an inductor. The switch in the circuit will be opened after a current is allowed to build up in the inductor. It follows the fundamental device law of any inductor where the voltage can be obtained by the product of inductor value and the change in current per time. A huge voltage will be present if the current is asked to change from something to zero instantly.
Two square waves are generated by the AVR microcontroller from its Timer 1 and Timer 2 units. The adjustment of frequency that drives the transistor varies the brightness of the LCD. A less time of current build up in the inductor is indicated by faster frequency.
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