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EE Times-India > Optoelectronics/Displays

Want to boost battery voltage in White LED apps?

Posted: 31 Jan 2008     Print Version  Bookmark and Share

Keywords:light-emitting diode  switched capacitor converter 

White LEDs are usually driven with a constant DC current source in order to maintain constant luminosity. In portable applications with single-cell Li-Ion source, the sum of the voltage drop across the white LED and the current source can be lower or higher than the battery voltage. This means that a white LED requires the battery voltage to be sometimes boosted. The easiest way to boost the battery voltage is to use a step-up DC/DC converter. This method significantly optimises efficiency at the expense of cost and PCB area. An alternative method of boosting the battery voltage is to use a charge pump, also called switched capacitor converter. Let's analyse in more detail the principle of operation of such a device. Charge pump basics A capacitor is a component that stores electrical charge or energy for release at some predetermined rate and at some predetermined time.

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