A new switched-capacitor frequency modulated driver for light emitting diodes.

A new type of drivers for light emitting diodes (LEDs) is introduced based on the switched-capacitor frequency modulation. In contrast to conventional constant dc current drivers, the current pulse is provided by this new switched-capacitor LED driver. In the present driver, the charging capacitor is charged and discharged through a LED and the current flow direction is controlled by a metal oxide semiconductor switch. The input current (and thus the LED brightness) is proportional to the switch clock frequency at relatively low frequencies and becomes saturated at relatively high frequencies. This new driver circuit is simple and robust and maintains high efficiency for a wide range of input powers. In addition, the dimming control is easily realized by modulating clock frequency. Finally, this LED driver consumes no dc current and thus provides inherent protection to LED in standby mode.