Abstract: A circuit is provided to drive LEDs or diode lasers that emit light in desired wavelengths, such as the primary colors red, green, and blue, which serve as the light source for a projection display system. A display controller controls one or more series-parallel arrays of each color LED in the LED circuit with control signals to synchronize the color output of the light source with image data received from an image data source such as a personal computer. Synchronization is achieved by sending control signals to the power supply and circuit switches to sequence the color output in a single path system or adjust continuous color output in a triple path system with minimal or no reductions in the brightness of the projected image.

Abstract: A FET switching regulator has a FET switch which is periodically turned on to couple an unregulated DC input voltage to an output filter which develops a regulated output DC voltage. Regulation of the output DC voltage is determined by the on time or duty cycle of the FET switch. A periodic waveform is developed by a pulse-width modulator. The pulse-width modulator compares the input and output DC voltages to a reference voltage to pulse-width modulate the periodic waveform to determine the duty cycle. When the periodic waveform goes high, it triggers a first regenerative circuit which drives the gate of the FET switch into saturation within 20-30 nanoseconds. When the periodic waveform goes low, a second regenerative circuit is triggered to return the FET switch to an off state within 20-30 nanoseconds. Accordingly, the FET switch may be operated at frequencies approaching 500 kHz without excessive power losses within the FET switch in the transitory states between cutoff and saturation.

Abstract: A current driven flyback power supply has a transistor current switch which periodically couples a primary current through the primary winding of a power transformer which is connected between a source of DC and the collector of the current switch. A current transformer has a first winding coupled between the primary winding and the collector of the current switch, and a second winding which develops a drive current proportional to the primary current. The drive current is coupled to the base of the current switch and increases proportionally with the increasing amplitude of the primary current. An electrical switch shorts the drive current to ground to turn off the current switch so that stored energy in the power transformer is coupled out through its secondary winding to an output rectifier circuit which develops the output DC voltage.