Unlike the traditional single mode of charge pump structure , the paper adopted 1x / 1 . 5x fractional adaptive charge pump , which can automatically convert working mode with the change of input voltage , and utilized ultra - low - dropout current regulators to make 0 . 15v led _ minimum regulation voltage in order to remain the charge pump working mostly in higher - efficiency 1x mode
2.
A white led driver circuit is presented in this paper . the circuit drives up to four white leds with regulated constant current for uniform intensity . by utilizing proprietary adaptive 1x / 1 . 5x modes and ultra - low - dropout current regulators , it maintains the highest possible efficiency over the full 1 - cell li + battery input voltage range
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