Start-up regulator for high-input-voltage power converters

1. A power converter system comprising:

first and second input terminals;

a converter connected to the first and second input terminals and including an output terminal;

a start-up circuit connected to a first capacitor and configured to charge the first capacitor during start-up and hiccup conditions;

a voltage source connected to the first and second input terminals and configured to provide, during the start-up and hiccup conditions, a voltage proportional to a voltage applied to the first and second input terminals; and

a voltage buffer including a MOSFET, the MOSFET including:

a gate connected to the voltage source;

a source connected to the start-up circuit; and

a drain connected to one of the first and second input terminals.

2. A power converter system of claim 1 , wherein the voltage source includes a high-impedance resistive divider.

3. A power converter system of claim 2 , wherein:

the high-impedance resistive divider includes first and second resistors connected in series;

the first resistor is connected to the first input terminal; and

the second resistor is connected to the second input terminal.

4. A power converter system of claim 3 , wherein:

the high-impedance resistive divider further includes second and third capacitors;

the second capacitor is connected in parallel with the first resistor; and

the third capacitor is connected in parallel with the second resistor.

5. A power converter system of claim 1 , wherein:

the converter includes a half-bridge circuit including at least two capacitors connected in series; and

the voltage source includes the at least two capacitors.

6. A power converter system of claim 1 , further comprising a capacitor connected to the output of the voltage buffer.

7. A power converter system of claim 1 , wherein the converter includes an auxiliary output.

8. A power converter system of claim 7 , wherein the auxiliary output is configured to charge the first capacitor during steady-state conditions.

9. A power converter system of claim 1 , further comprising an IC controller configured to provide control signals to the converter after the first capacitor is charged to a predetermined voltage level.

10. A power converter system of claim 9 , wherein the IC controller includes the start-up circuit.

11. A power converter system of claim 10 , wherein the IC controller includes an input pin that is connected to the start-up circuit and a power-supply pin that is connected to the first capacitor.

12. A power converter system of claim 11 , wherein the start-up circuit charges the first capacitor through the power-supply pin.

13. A power converter system of claim 1 , wherein the voltage source does not include a Zener diode or a reference voltage.