Patent ID: 9578724
Date: 2017-02-21
CPC Classifications: H04B,H05B

Claim:
1. An illumination device, comprising: a plurality of light emitting diode (LED) chains; a driver circuit configured for driving the plurality of LED chains with drive currents substantially continuously to produce illumination, periodically turning the plurality of LED chains off during a first period to take measurements or communicate optical data, and supplying a non-operative drive current to each LED chain, one chain at a time, during short durations of time to measure an operating forward voltage developed across each LED chain; and a control circuit configured for determining respective drive currents needed to achieve a desired luminous flux from each LED chain using the operating forward voltages measured across each LED chain, a table of calibration values and one or more interpolation techniques, wherein during the first period, the control circuit instructs the driver circuit to increase the respective drive currents supplied to the plurality of LED chains by a small amount when the plurality of LED chains are on to compensate for a decrease in or lack of illumination when the LED chains are periodically turned off during the first period.