US 7,030,569 B2Granted

Direct drive CCFL circuit with controlled start-up mode

AssigneeAnalog Microelectronics, Inc.

InventorRichard L. Gray

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Abstract

A CCFL can exhibit different strike characteristics depending on age and temperature. A CCFL in a direct driven CCFL circuit that is difficult to strike can appear to be malfunctioning using a standard start up operation. A controlled start up allows additional opportunities for a slow striking CCFL to strike. In one embodiment, the CCFL of the direct drive CCFL circuit can be initially driven at a switching frequency substantially different than a resonant frequency. Based on certain conditions, the switching frequency can subsequently be allowed to approach resonant frequency in a controlled manner. If the driving frequency reaches the resonant frequency of the CCFL during a set time period, then the CCFL can enter into steady state operation. At this point, the same conditions can be monitored to identify fault conditions in the direct drive CCFL circuit.

Claims5

Dependent claims

A method of improving a start up operation of a direct drive CCFL circuit, the method comprising:

driving a CCFL of the direct drive CCFL circuit at a switching frequency substantially different than a resonant frequency of the CCFL circuit;
and
allowing the switching frequency to approach the resonant frequency in a controlled manner,
wherein allowing the switching frequency to approach resonant frequency in a controlled manner includes:
monitoring an input voltage and a current of the CCFL to determine whether the switching frequency is incrementally changed to approach resonant frequency,
wherein monitoring includes:
determining whether the input voltage is equal to or less than a predetermined intermediate voltage and an output voltage of the CCFL, which is proportional to the current of the CCFL, is less than a predetermined low voltage;
and
if so, then incrementally changing the switching frequency to approach resonant frequency.

6 more elements

Dependencies are inferred from the claim text.