Patent ID: 7430131

Claim:
A startup circuit for providing a startup voltage from a high voltage DC bus voltage to an application circuit, the startup circuit comprising: an integrated circuit package for at least a control circuit for driving at least one power switch of the application circuit having a low voltage terminal; a dropping resistor in the integrated circuit package having a first terminal for coupling to the high voltage DC bus and a second terminal, the dropping resistor dropping the high voltage DC bus voltage to a reduced voltage and providing the reduced voltage at the second terminal; a low voltage regulator coupled to the second terminal for using the reduced voltage for enabling generation of a regulated startup low voltage DC output at a preset level at the low voltage terminal for powering at least one part of the application circuit during startup of the application circuit, wherein the high voltage DC bus voltage is the only voltage source provided externally to the integrated circuit package and wherein the low voltage regulator comprises a first high voltage switch in series circuit with a first resistance, the series circuit coupled between said first terminal and said low voltage terminal; a second switch coupled between said second terminal and a terminal having a reference potential and having a control electrode coupled to a voltage sensor sensing said low voltage DC output; a voltage reference source for setting the low voltage DC output; said voltage reference source and voltage sensor being coupled in series between said low voltage DC output and said terminal having said reference potential; whereby when said low voltage DC output at the low voltage terminal changes from the preset level, conduction through said second switch changes, thereby changing the voltage at the control electrode of the first high voltage switch to drive the low voltage DC output back to the preset level.