Method and apparatus for canceling ripple current in a lamp

• US 6,628,094 B2
• Filed: 07/30/2002
• Issued: 09/30/2003
• Est. Priority Date: 12/27/2000
• Status: Expired due to Fees

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: InFocus Corporation (Lap-Shun Hui, MBA)
• Inventors: Pruett, Henry Frazier
• Primary Examiner(s): Lee, Wilson
• Application Number:
  US10/208,986
• Publication Number:
  US 20020195976A1
• Time in Patent Office: 427 Days
• Field of Search: 315/291, 315/224, 315/244, 315/283, 315/289, 315/276, 315/209.R, 315/240, 315/246, 315/248, 315/247, 323/280-282, 323/285, 323/269
• US Class Current: 315/291
• CPC Class Codes: H02M 1/14 Arrangements for reducing ripples from dc input or output
• CPC Class Codes: H02M 3/1584 with a plurality of power processing stages connected in parallel
• CPC Class Codes: H05B 41/28 using static converters
• CPC Class Codes: H05B 41/2858 for protecting the lamp against abnormal operating conditions

Abstract

A method and apparatus for reducing ripple current in a projector lamp comprising an electrical network comprising input terminals A and C, and output terminals B and D, including a first inductive element and a second inductive element, each inductive element having a first terminal and a second terminal, with the second terminal of the first inductive element electrically connected with the second terminal of the second inductive element at output terminal B, with the first terminal of the first inductive element connected to input terminal A, and the first terminal of the second inductive element connected to input terminal C; and a means for impressing a first source of switching potential from an external source at input terminal A, and a second source of switching potential from the external source out-of-phase with the first source of switching potential, at input terminal C such that a ripple current across the output terminals B and D is minimum.

Claims

1. An apparatus comprising:

a pulse width modulation circuit having a first output to provide a first switched signal and a second output to provide a second switched signal, wherein the first switched signal and the second switched signal are 180°

out of phase;

a first drive amplifier having an input coupled to the first output of the pulse width modulation circuit to receive the first switched signal;

a second drive amplifier having an input coupled to the second output of the pulse width modulation circuit to receive the second switched signal;

a first inductive element having an input terminal coupled to an output terminal of the first drive amplifier and an output terminal;

a second inductive element having an input terminal coupled to an output terminal of the second drive amplifier and an output terminal, the output terminal of the second inductive element coupled with the output terminal of the first inductive element;

a lamp socket coupled between the output terminals of the first inductive element and the second inductive element and ground; and

a capacitive element coupled between the output terminals of the first inductive element and the second inductive element and ground.

2. The apparatus of claim 1 further comprising a projector lamp connected to the lamp socket.

3. The apparatus of claim 1 wherein a value of the capacitive element is between 0.01 microFarads and 0.1 microFarads.

4. The apparatus of claim 1 wherein a value of the first inductive element is between 100 microHenrys and 500 microHenrys.

5. The apparatus of claim 1 wherein a value of the second inductive element is between 100 microHenrys and 500 microHenrys.

6. The apparatus of claim 1 wherein a value of the first inductive element is substantially equal to a value of the second inductive element.

7. A projector comprising:

a pulse width modulation circuit having a first output to provide a first switched signal and a second outnut to provide a second switched signal, wherein the first switched signal and the second switched signal are 180°

out of phase;

a first drive amplifier having an input coupled to the first output of the pulse width modulation circuit to receive the first switched signal;

a second drive amplifier having an input coupled to the second output of the pulse width modulation circuit to receive the second switched signal;

a first inductive element having an input terminal coupled to an output terminal of the first drive amplifier and an output terminal;

a second inductive element having an input terminal coupled to an output terminal of the second drive amplifier and an output terminal, the output terminal of the second inductive element coupled with the output terminal of the first inductive element;

a capacitive element coupled between the output terminals of the first inductive element and the second inductive element and ground;

a lamp coupled between the output terminals of the first inductive element and the second inductive element and ground.

8. The projector of claim 7 wherein a value of the capacitive element is between 0.01 microFarads and 0.1 microFarads.

9. The projector of claim 7 wherein a value of the first inductive element is between 100 microHenrys and 500 microHenrys.

10. The projector of claim 7 wherein a value of the second inductive element is between 100 microHenrys and 500 microHenrys.

11. The projector of claim 7 wherein a value of the first inductive element is substantially equal to a value of the second inductive element.