COLD_CATHODE_FLUORESCENT_LAMP_DRIVER

Published:2009/7/13 20:55:00 Author:May | From:SeekIC

In this circuit, the lamp is driven sinusoidally, minimizing RF emissions in sensitive portable applications. Lamp intensity is controlled smoothly from zero to full brightness with no hysteresis or pop on. This floating bulb circuit configuration extends the illumination range for the bulb because parasitic bulb-to-display-frame capacitive losses are minimized. The feedback signal is generated by monitoring the primary-side Royer converter current between the BAT and Royer pins. The LT1184F current-mode switching regulator and L2 provide an average current to Q1 and Q2, which form a Royer-class converter along with L1 and C1. The lamp is driven by L1's secondary. Feedback to the LT1184F is provided on the primary side of L1 for floating bulb configurations, whereas feedback in the grounded configuration is provided by sensing one-half of the average bulb current. The oscillator frequency is 200 kHz, which minimizes the size of the required magnetics.



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