CURRENT DRIVEN BIPOLAR HIGH VOLTAGE DRIVER FOR CAPACITIVE LOADS

• US 20070296348A1
• Filed: 06/14/2007
• Published: 12/27/2007
• Est. Priority Date: 06/15/2006
• Status: Active Grant

• Current Assignee: Microchip Technology Incorporated
• Original Assignee: Supertex Incorporated (Microchip Technology Incorporated)
• Inventors: Walker, James T.
• Granted Patent: US 8,154,898 B2
• Time in Patent Office: Days
• US Class Current: 315/226
• CPC Class Codes: H02M 3/073 Charge pumps of the Schenkel-type
• CPC Class Codes: H05B 44/00 Circuit arrangements for operating electroluminescent light sources for operating light emitting diodes H05B45/00
• CPC Class Codes: H05B 45/355 Power factor correction [PFC]; Reactive power compensation

Abstract

A circuit for generating a high voltage alternating current to drive a load has a current source having a first terminal and a second terminal. The circuit further has an output terminal and a circuit ground terminal. A first switch will conduct between the first terminal of the current source and the circuit ground terminal when the first switch is closed. A second switch will conduct between the first terminal of the current source and the output terminal when the second switch is closed. A third switch will conduct between the second terminal of the current source and the circuit ground terminal when the third switch is closed. A fourth switch will conduct between the second terminal of the current source and the output terminal when the fourth switch is closed. A load is coupled to the output terminal and the circuit ground terminal.

Claims

1. A circuit for generating a high voltage alternating current to drive a load comprising:

a current source having a first terminal and a second terminal;

an output terminal;

a circuit ground terminal;

a first switch conducting between the first terminal of the current source and the circuit ground terminal when the first switch is closed;

a second switch conducting between the first terminal of the current source and the output terminal when the second switch is closed;

a third switch conducting between the second terminal of the current source and the circuit ground terminal when the third switch is closed;

a fourth switch conducting between the second terminal of the current source and the output terminal when the fourth switch is closed; and

a load coupled to the output terminal and the circuit ground terminal.

2. A circuit for generating a high voltage alternating current to drive a load in accordance with claim 1 wherein the load is an electroluminescent lamp.

3. A circuit for generating a high voltage alternating current to drive a load in accordance with claim 1 wherein the load is an electroluminescent lamp having more than two electrodes.

4. A circuit for generating a high voltage alternating current to drive a load in accordance with claim 1 wherein the first switch, the second switch, the third switch and the fourth switch open and close to alternately connecting the current source in series with the load with one of two polarities.

5. A circuit for generating a high voltage alternating current to drive a load in accordance with claim 1 wherein the second switch and the third switch closes to charge the load in a first polarity and the first switch and the fourth switch closes to charge the load in a second polarity.

6. A circuit for generating a high voltage alternating current to drive a load in accordance with claim 1 wherein the current source has an output resistance.

7. A circuit for generating a high voltage alternating current to drive a load in accordance with claim 1 wherein the first switch, the second switch, the third switch and the fourth switch are MOSFET devices.

8. A circuit for generating a high voltage alternating current to drive a load in accordance with claim 1 wherein the current source is a capacitive charge pump.

9. A circuit for generating a high voltage alternating current to drive a load in accordance with claim 8 wherein the capacitive charge pump comprises:

a plurality of diodes coupled in series;

a plurality of capacitive elements wherein one capacitive element is coupled to an output of each of the plurality of diodes; and

a pair of voltage sources coupled to the plurality of capacitive elements wherein the pair of voltage sources have voltage signals of opposite phases.

10. A circuit for generating a high voltage alternating current to drive a load in accordance with claim 8 wherein the capacitive charge pump comprises:

a first voltage source;

a second voltage source, wherein the second voltage sources is approximately 180 degrees out of phase with the first voltage source;

a plurality of diodes coupled in series;

a first capacitor coupled to an output of a first diode and to ground;

a second capacitor coupled to an output of a second diode and to the first voltage source;

a third capacitor coupled to an output of a third diode and to the second voltage source;

a fourth capacitor coupled to an output of a fourth diode and to the first voltage source;

a fifth capacitor coupled to an output of a fifth diode and to the second voltage source; and

a sixth capacitor coupled to an input of the fifth capacitor and to ground.

11. A circuit for generating a high voltage alternating current to drive a load in accordance with claim 10, wherein the first capacitor and the sixth are bypass capacitors to reduce a voltage ripple across the load.

12. A circuit for generating a high voltage alternating current to drive a load in accordance with claim 1 wherein the circuit is fabricated on a single semiconductor die.

13. A circuit for generating a high voltage alternating current to drive a load comprising:

a current source having a first terminal and a second terminal;

an output terminal;

a circuit ground terminal;

a first switch conducting between the first terminal of the current source and the circuit ground terminal when the first switch is closed;

a second switch conducting between the first terminal of the current source and the output terminal when the second switch is closed;

a third switch conducting between the second terminal of the current source and the circuit ground terminal when the third switch is closed;

a fourth switch conducting between the second terminal of the current source and the output terminal when the fourth switch is closed; and

a load coupled to the output terminal and the circuit ground terminal;

wherein the first switch, the second switch, the third switch and the fourth switch open and close to alternately connecting the current source in series with the load with one of two polarities, the second switch and the third switch closing to charge the load in a first polarity and the first switch and the fourth switch closing to charge the load in a second polarity.

14. A circuit for generating a high voltage alternating current to drive a load in accordance with claim 13 wherein the load is an electroluminescent lamp.

15. A circuit for generating a high voltage alternating current to drive a load in accordance with claim 13 wherein the load is an electroluminescent lamp having more than two electrodes.

16. A circuit for generating a high voltage alternating current to drive a load in accordance with claim 13 wherein the first switch, the second switch, the third switch and the fourth switch are MOSFET devices.

17. A circuit for generating a high voltage alternating current to drive a load in accordance with claim 13 wherein the current source is a capacitive charge pump.

18. A circuit for generating a high voltage alternating current to drive a load in accordance with claim 13 wherein the capacitive charge pump comprises:

a plurality of diodes coupled in series;

a plurality of capacitive elements wherein one capacitive element is coupled to an output of each of the plurality of diodes; and

a pair of voltage sources coupled to the plurality of capacitive elements wherein the pair of voltage sources have voltage signals of opposite phases.

19. A circuit for generating a high voltage alternating current to drive a load in accordance with claim 13 wherein the capacitive charge pump comprises:

a first voltage source;

a second voltage source, wherein the second voltage sources is approximately 180 degrees out of phase with the first voltage source;

a plurality of diodes coupled in series;

a first capacitor coupled to an output of a first diode and to ground;

a second capacitor coupled to an output of a second diode and to the first voltage source;

a third capacitor coupled to an output of a third diode and to the second voltage source;

a fourth capacitor coupled to an output of a fourth diode and to the first voltage source;

a fifth capacitor coupled to an output of a fifth diode and to the second voltage source; and

a sixth capacitor coupled to an input of the fifth capacitor and to ground.

20. A circuit for generating a high voltage alternating current to drive a load in accordance with claim 19 wherein the first capacitor and the sixth capacitor are bypass capacitors to reduce a voltage ripple across the load.