Current driven bipolar high voltage driver for capacitive loads

• US 8,154,898 B2
• Filed: 06/14/2007
• Issued: 04/10/2012
• 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.
• Primary Examiner(s): Berhane, Adolf
• Assistant Examiner(s): Finch, III, Fred E
• Application Number:
  US11/762,901
• Publication Number:
  US 20070296348A1
• Time in Patent Office: 1,762 Days
• Field of Search: 363/59, 363/132, 363/98, 363/60, 315/169.3, 327/536
• US Class Current: 363/132
• 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 charge pump having a first terminal and a second terminal;

an output terminal;

a circuit ground terminal;

a pair of output capacitive elements attached to the charge pump and the circuit ground terminal to reduce frequency fluctuations, wherein a first output capacitive element is attached to the first terminal of the charge pump and to the circuit ground terminal and a second output capacitive element is attached to the second terminal of the charge pump and to the circuit ground terminal;

a first switch wherein a first switch first terminal is connected to the first terminal of the charge pump and the first output capacitive element, a first switch second terminal is attached to the circuit ground terminal, the first switch conducting between the first terminal of the charge pump and the circuit ground terminal when the first switch is closed;

a second switch wherein a second switch first terminal is connected to the first terminal of the charge pump and the first output capacitive element, a second switch second terminal is attached to the load terminal, the second switch conducting between the first terminal of the charge pump and the output terminal when the second switch is closed;

a third switch wherein a third switch first terminal is connected to the circuit ground terminal and a third switch second terminal is attached to the second terminal of the charge pump and the second output capacitive element, the third switch conducting between the second terminal of the charge pump and the circuit ground terminal when the third switch is closed;

a fourth switch wherein a fourth switch first terminal is connected to the load terminal and a fourth switch second terminal is attached to the second terminal of the charge pump and the second output capacitive element, the fourth switch conducting between the second terminal of the charge pump and the output terminal when the fourth switch is closed; and

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

wherein both the first terminal and the second terminal of the charge pump float to interchange which of the first terminal and the second terminal of the charge pump is grounded to the load;

wherein the charge pump is a capacitive charge pump providing an approximately constant current output across variable load voltages;

wherein a minimum terminal count of the circuit is 3.

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, wherein an electroluminescent first terminal is attached to the output terminal and an electroluminescent second terminal is attached to the circuit ground terminal.

3. A circuit for generating a high voltage alternating current to drive a load in accordance with claim 1,

wherein the first switch is a first transistor having a first transistor first terminal connected to the first terminal of the current source, a first transistor second terminal attached to the circuit ground terminal, and a first transistor third terminal attached to a first digital control signal;

wherein the second switch is a second transistor having a second transistor first terminal connected to the first terminal of the current source, a second transistor second terminal attached to the load terminal, and a second transistor third terminal attached to a second digital control signal;

wherein the third switch is a third transistor having a third transistor first terminal connected to the circuit ground terminal, a third transistor second terminal attached to the second terminal of the current source, and a third transistor third terminal attached to a third digital control signal;

wherein the fourth switch is a fourth transistor having a fourth transistor first terminal connected to the load terminal, a fourth transistor second terminal attached to the second terminal of the current source, and a fourth transistor third terminal attached to a fourth digital control signal.

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 connect 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 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.

9. A circuit for generating a high voltage alternating current to drive a load in accordance with claim 1 wherein the 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.

10. A circuit for generating a high voltage alternating current to drive a load in accordance with claim 9, wherein the first capacitor and the sixth capacitor are bypass capacitors to reduce a voltage ripple across the load.

11. 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.

12. 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 shaping capacitor attached to the first terminal of the current source and to the circuit ground terminal to reduce frequency fluctuations from the first terminal of the current source;

a second shaping capacitor attached to the second terminal of the current source and to the circuit ground terminal to reduce frequency fluctuations from the second terminal of the current source;

a first switch wherein a first switch first terminal is connected to the first terminal of the current source and a first switch second terminal is attached to the circuit ground terminal, the 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 wherein a second switch first terminal is connected to the first terminal of the current source and a second switch second terminal is attached to the load terminal, the second switch conducting between the first terminal of the current source and the output terminal when the second switch is closed;

a third switch wherein a third switch first terminal is connected to the circuit ground terminal and a third switch second terminal is attached to the second terminal of the current source, the 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 wherein a fourth switch first terminal is connected to the load terminal and a fourth switch second terminal is attached to the second terminal of the current source, the fourth switch conducting between the second terminal of the current source and the output terminal when the fourth switch is closed;

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 connect 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;

wherein both the first terminal and the second terminal of the current source float to interchange which of the first terminal and the second terminal of the current source is grounded to the load;

wherein the current source is a capacitive charge pump providing an approximately constant current output across variable load voltages;

wherein a minimum terminal count of the circuit is 3.

13. A circuit for generating a high voltage alternating current to drive a load in accordance with claim 12 wherein the load is an electroluminescent lamp.

14. A circuit for generating a high voltage alternating current to drive a load in accordance with claim 12 wherein the first switch is a first transistor having a first transistor first terminal connected to the first terminal of the current source, a first transistor second terminal attached to the circuit ground terminal, and a first transistor third terminal attached to a first digital control signal;

wherein the second switch is a second transistor having a second transistor first terminal connected to the first terminal of the current source, a second transistor second terminal attached to the load terminal, and a second transistor third terminal attached to a second digital control signal;

wherein the third switch is a third transistor having a third transistor first terminal connected to the circuit ground terminal, a third transistor second terminal attached to the second terminal of the current source, and a third transistor third terminal attached to a third digital control signal;

wherein the fourth switch is a fourth transistor having a fourth transistor first terminal connected to the load terminal, a fourth transistor second terminal attached to the second terminal of the current source, and a fourth transistor third terminal attached to a fourth digital control signal.

15. A circuit for generating a high voltage alternating current to drive a load in accordance with claim 12 wherein the first switch, the second switch, the third switch and the fourth switch are MOSFET devices.

16. A circuit for generating a high voltage alternating current to drive a load in accordance with claim 12 wherein the current source is a capacitive charge pump.

17. A circuit for generating a high voltage alternating current to drive a load in accordance with claim 16 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.

18. A circuit for generating a high voltage alternating current to drive a load in accordance with claim 16 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.

19. A circuit for generating a high voltage alternating current to drive a load in accordance with claim 18 wherein the first capacitor and the sixth capacitor are bypass capacitors to reduce a voltage ripple across the load.