A LOW VOLTAGE HEADROOM CURRENT SINK DESIGN FOR WHITE LED DRIVER WITH PWM DIMMING

摘要

: The various embodiments of the present invention provide a device and method to develop a low voltage current sink for WLED with PWM control for dimming. According to one embodiment, two MOSFETs are connected in parallel with the input power source. Two feed back paths involving operational amplifiers are connected to the MOSFETS to ensure the same drain source voltages and identical over drive voltages through both the MOSFETs. A third MOSFET is connected to the second MOSFET to make the current through the two MOSFETs identitical. A fourth MOSFET is cormected to third MOSFET in parallel to form a sink for WLED. A PWM switch set is cormected to the sink to regulate the current to achieve dimming control. The MOSFETs are operated in linear region. No. of Pages : 51 No. of Claims : 23