Method for starting a discharge lamp using high energy initial pulse

• US 7,880,397 B2
• Filed: 08/15/2007
• Issued: 02/01/2011
• Est. Priority Date: 12/11/1998
• Status: Expired due to Fees

• Current Assignee: Monolithic Power Systems Incorporated
• Original Assignee: Monolithic Power Systems Incorporated
• Inventors: Rust, Timothy J., Christy, David Joseph, Moyer, James C.
• Primary Examiner(s): Vo; Tuyet Thi
• Application Number:
  US11/839,174
• Publication Number:
  US 20070278967A1
• Time in Patent Office: 1,266 Days
• Field of Search: 315/247, 315/246, 315/224, 315/225, 315/209.R, 315307-312, 315/128, 315/119, 315/127, 315/194, 315/276, 315/274
• US Class Current: 315/224
• CPC Class Codes: H05B 41/2824 using control circuits for the switching element H05B41/2822 takes precedence
• CPC Class Codes: H05B 41/2827 using specially adapted components in the load circuit, e.g. feed-back transformers, piezoelectric transformers; using specially adapted load circuit configurations
• CPC Class Codes: H05B 41/2828 using control circuits for the switching elements H05B41/2827 takes precedence
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps

Abstract

The described DC to AC inverter efficiently controls the amount of electrical power used to drive a cold cathode fluorescent lamp (CCFL). Additionally, during striking of the CCFL, a higher energy initial energy pulse is used. During normal operation, a lower energy pulse is used.

Claims

1. A method of controlling a DC to AC inverter that includes a network of plurality of switches that generates an AC signal from a DC signal, a tank circuit, and a controller for driving a discharge lamp, comprising:

initializing said controller;

striking said discharge lamp using a first AC signal generated by said network of plurality of switches and said tank circuit, said first AC signal having the same frequency as a resonant frequency of said tank circuit; and

driving said discharge lamp using a second AC signal generated by said network of plurality of switches and said tank circuit, wherein said first AC signal has a higher electrical energy than said second AC signal;

wherein said first AC signal has a larger pulse width than said second AC signal, and further wherein said striking of said discharge lamp using a first AC signal comprises modulating the pulse width of each half cycle of said first AC signal.

2. The method of claim 1 further comprising:

monitoring an electrical power delivered to said discharge lamp using a feedback control mechanism; and

adjusting said electrical power delivered into said discharge lamp whenever said electrical energy is outside of a predetermined range.

3. The method of claim 1 wherein said driving said discharge lamp further comprises:

monitoring an on and off state of each of said switches in said network of plurality of switches; and

controlling said on and off state of said network of switches to avoid a shoot-through problem.

4. The method of claim 1 wherein said driving said discharge lamp further comprising using parasitic capacitances and inductances to generate said resonant frequency in said tank circuit.

5. The method of claim 1 wherein said driving said discharge lamp further comprises:

determining whether a thermal overload condition occurs at said discharge lamp; and

terminating said second AC signal that drives said discharge lamp.

6. The method of claim 1 wherein said driving said discharge lamp further comprises:

detecting an open-circuit condition in said discharge lamp; and

reducing the power delivered to said discharge lamp after said open-circuit condition.

7. The method of claim 1 wherein said driving said discharge lamp further comprises:

detecting whether an electrical malfunction condition exists in said discharge lamp; and

terminating said second AC signal delivered to said discharge lamp after said electrical malfunction is detected.