Reduced bus voltage integrated boost high power factor circuit

• US 5,712,536 A
• Filed: 07/31/1995
• Issued: 01/27/1998
• Est. Priority Date: 07/31/1995
• Status: Expired due to Fees

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Kachmarik, David J., Belle, Kelvin B., Haas, Kurt W.
• Primary Examiner(s): Pascal, Robert
• Assistant Examiner(s): KINKEAD, ARNOLD M
• Application Number:
  US08/509,281
• Time in Patent Office: 911 Days
• Field of Search: 315/247, 315/219, 315/DIG. 7, 315/209 R, 363/37, 363/132, 323/222
• US Class Current: 315/247
• CPC Class Codes: H05B 41/28 using static converters
• CPC Class Codes: Y10S 315/07 Starting and control circuits for gas discharge lamp using transistors

Abstract

A condensed power supply circuit for powering a gas discharge lamp with bi-directional current reduces duty cycle by increasing dead time. The circuit comprises an arrangement for supplying d.c. power from an a.c. voltage, a series half bridge converter, a boost converter, a resistor-capacitor delay circuit associated with a gate to control dead time, and a snubber capacitance for facilitating zero voltage switching to fill the entire dead time. The series half-bridge converter alternately impresses a d.c. bus voltage from a bus conductor across a load circuit first with one polarity and then with an opposite polarity. The series half-bridge converter includes a first switch, a second switch, and a switching control circuit for alternately switching on the first and second switches. The boost converter comprises a boost capacitor, a boost inductor, and means for periodically connecting a load end of the boost inductor through a low impedance path to the ground conductor, thereby charging the boost inductor. The present invention reduces duty cycle via an increase in dead time. The resistor-capacitor delay circuit, associated with a gate, is used to control dead time. The snubber capacitance, which facilitates zero voltage switching to fill the entire dead time range, has a value set by the resistor-capacitor delay circuit.

Claims

1. A condensed power supply circuit for powering a gas discharge lamp with bi-directional current, the circuit comprising:

means for supplying d.c. power from an a.c. voltage;

a series half bridge converter for alternately impressing a d.c. bus voltage from a bus conductor across a load circuit first with one polarity and then with an opposite polarity relative to said one polarity, said series half bridge converter including;

a first switch interposed between said bus conductor and a first node to which said load circuit is coupled, a second switch interposed between a ground conductor and said first node, and

a switching control circuit for alternately switching on said first and second switches;

a boost converter comprising;

a boost capacitor connected between said bus and ground conductors and whose level of charge determines the bus voltage on said bus conductor, a boost inductor for storing energy from said means for supplying d.c. power, said boost inductor being connected by a diode to said boost capacitor for discharging its energy into said boost capacitor, and

means for periodically connecting a load end of said boost inductor through a low impedance path being connected by a diode to said ground conductor and thereby charging said boost inductor, said connecting means including a boost switch wherein said load end of said boost inductor is coupled to one terminal of said boost switch so that, in a first condition, said boost switch is effective so as to allow such charging of said boost inductor, and in a second condition, is effective so as to allow said boost inductor to discharge into said boost capacitor;

a resistor-capacitor delay circuit means associated with a gate to control dead time a period during which both first and second switches are off; and

a snubber capacitor means for facilitating zero voltage switching to fill said entire dead time, said snubber capacitor means having a value set by said resistor-capacitor delay circuit means.

2. A condensed power supply circuit as claimed in claim 1 wherein said resistor-capacitor delay circuit means controls dead time by building a delay into transition of voltage across said first and second switches.

3. A condensed power supply circuit as claimed in claim 1 wherein said snubber capacitor means is interposed across said first and second switches.

4. A condensed power supply circuit as claimed in claim 1 wherein said snubber capacitor means is interposed between said first and second switches and first and second half-bridge capacitors.

5. A condensed power supply circuit as claimed in claim 1 wherein said boost switch comprises said second switch of said series half bridge converter.

13. A condensed power supply circuit as claimed in claim 1 wherein the dead time controls the bus voltage.

6. A method for powering a gas discharge lamp with bi-directional current, the method comprising the steps of:

supplying d.c. power from an a.c. voltage;

providing a series half bridge converter for alternately impressing a d.c. bus voltage from a bus conductor across a load circuit first with one polarity and then with an opposite polarity relative to said one polarity, said series half bridge converter including;

a first switch interposed between said bus conductor and a first node to which said load circuit is coupled,

a second switch interposed between a ground conductor and said first node, and

a switching control circuit for alternately switching on said first and second switches;

providing a boost converter comprising;

a boost capacitor connected between said bus and ground conductors and whose level of charge determines the bus voltage on said bus conductor,

a boost inductor for storing energy from said means for supplying d.c. power, said boost inductor being connected by a diode to said boost capacitor for discharging its energy into said boost capacitor, and

means for periodically connecting a load end of said boost inductor through a low impedance path being connected by a diode to said ground conductor and thereby charging said boost inductor, said connecting means including a boost switch wherein said load end of said boost inductor is coupled to one terminal of said boost switch so that, in a first condition, said boost switch is effective so as to allow such charging of said boost inductor, and in a second condition, is effective so as to allow said boost inductor to discharge into said boost capacitor; and

increasing a dead time a period during which first and second switches are off for reducing the bus voltage.

7. A method for powering a gas discharge lamp with bi-directional current as claimed in claim 6 wherein the step of increasing dead time further comprises the step of providing a resistor-capacitor delay circuit means associated with a gate to control said dead time.

8. A method for powering a gas discharge lamp with bi-directional current as claimed in claim 6 further comprising the step of using a snubber capacitor means to facilitate zero voltage switching to fill said entire dead time.

9. A method for powering a gas discharge lamp with bi-directional current as claimed in claim 7 further comprising the step of using said resistor-capacitor delay circuit means to set a value for said snubber capacitor means.

10. A method for powering a gas discharge lamp with bi-directional current as claimed in claim 8 wherein said snubber capacitor means is interposed across said first and second switches.

11. A method for powering a gas discharge lamp with bi-directional current as claimed in claim 8 wherein said snubber capacitor means is interposed between said first and second switches and first and second half-bridge capacitors.

12. A method for powering a gas discharge lamp with bi-directional current as claimed in claim 6 further comprising the step of building a delay into transition of voltage across said first and second switches.

14. A method for powering a gas discharge lamp with bi-directional current as claimed in claim 6 wherein increasing the dead time reduces a duty cycle.

15. A condensed power supply circuit for powering a gas discharge lamp with bi-directional current, the circuit comprising:

means for supplying d.c. power from an a.c. voltage;

a series half bridge converter for alternately impressing a d.c. bus voltage from a bus conductor across a load circuit first with one polarity and then with an opposite polarity relative to said one polarity, said series half bridge converter including a first switch, a second switch and a switching control circuit for alternately switching on said first and second switches;

a boost converter comprising a boost capacitor connected between said bus conductor and a ground conductor and whose level of charge determines the bus voltage on said bus conductor; and

a resistor-capacitor delay circuit for controlling a dead time, the dead time controlling the bus voltage, the first switch and the second switch being in an off state during the dead time.

16. A condensed power supply circuit as claimed in claim 15 wherein increasing the dead time reduces a duty cycle seen by the boost converter.

17. A condensed power supply circuit as claimed in claim 16 wherein reducing the duty cycle reduces the bus voltage.

18. A condensed power supply circuit as claimed in claim 15 wherein increasing the dead time reduces a duty cycle seen by the boost converter, thereby reducing the bus voltage.