Start-up circuit for providing a start-up voltage to an application circuit

1. 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 directly 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; and

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 contained in a high voltage well and

further comprising a second switch for sensing the startup low voltage DC output and for turning off the first high voltage switch,

further comprising a third switch coupled in series with a further resistance element between the second terminal and the low voltage DC output, with the third switch having its gate electrode coupled through another resistance element to the low voltage DC output, whereby the third switch is turned on when the first high voltage switch is turned off, thereby providing power to said low voltage DC output, with power dissipation reduced by said further resistance element.

2. The startup circuit of claim 1 , wherein said dropping resistor comprises a polysilicon resistor contained in the high voltage well.

3. The startup circuit of claim 2 , wherein the polysilicon resistor comprises a spiral-shaped polysilicon resistor disposed at a border of the high voltage well for shaping the electric field.

4. The startup circuit of claim 1 , wherein the second and third switches are contained in a low voltage well.

5. The startup circuit of claim 2 , wherein said polysilicon resistor has a resistance in the tens of megohms.

6. The startup circuit of claim 1 , wherein the application circuit comprises a high voltage application circuit.

7. The startup circuit of claim 6 , wherein the high voltage application circuit comprises a switching regulator.