VARIABLE MASTER CURRENT MIRROR

摘要

A variable master current mirror circuit (170) may be used to balance the currents through a parallel Light Emitting Diode (LED) strings (110, 111) in an illumination module when the LED string with the largest forward voltage changes due to events, such as a short failure of an LED. The variable master current mirror circuit (170) includes a switching circuit (170s) that is coupled to the parallel LED strings and a current mirror circuit (170cm) that is coupled to the parallel LED strings and the switching circuit. The switching circuit switchably connects the LED string with the largest forward voltage to the current mirror circuit as a master LED string. The current mirror circuit maintains equal currents (182, 183) through the LED strings with reference to the current through the master LED string.