A novel PMOS controlled high voltage current source

A novel high voltage current source for providing an initial bias current to an integrated switched mode power supply (SMPS) is presented. An enhanced mode VDMOS transistor, the gate of which is biased by a floating p-island, is used to provide start up current and sustain high voltage. A PMOS transistor is included to turn the high voltage current source off to eliminate power consumption when the start up phase is over. Simulation results indicate the high voltage current source can start and restart as designed. The proposed structure is believed to be more energy saving and cost effective compared with other solutions.