Patent ID: 7362058

Claim:
A method of controlling the light intensity in a multi-lamp illumination device for a display panel, comprising the steps of: supplying a pulse-width modulated intensity control signal, a master/slave control signal and a phase control signal from a display controller to a plurality of lamp controllers, each lamp controller associated with a respective lamp of the display panel; for each lamp controller; switching the respective lamp controller between a master mode and a slave mode in response to the master/slave control signal using a logic control circuit; providing a phase lock loop having an output that, in the slave mode, is locked to the intensity control signal; multiplexing a lamp activation output so that, in the master mode, the intensity control signal is routed to the lamp activation output, and, in the slave mode, a signal is passed to the lamp activation output, the phase of which is determined by the output of a phase control circuit that receives as a first input the output of the phase lock loop and as a second input the phase control.