This document introduces a high efficiency Royer driver for a scanner CCFL. The circuit can be easily modified for CCFL lamps of other sizes for use in large screen LCD displays and notebook computers.
The note presents a practical application of Zetex’s very low Vcesat transistor to drive a 4.5 W CCFL lamp used in scanners. The circuit is powered from a fixed 12.0 V DC supply and can be adapted for other CCFL sizes in LCD displays and notebook computers.
The complete circuit (Figure 1) operates at a nominal 65.0 kHz, draws 5.0 mA lamp current (370 mA input), and achieves greater than 80 % efficiency with a 150 kΩ dummy load. No heatsinking is required, reducing cost and simplifying integration.
| CCFL lamp size | 240.0 mm × 3.0 mm diameter |
|---|---|
| Lamp current | 5.0 mA |
| Input current | 370.0 mA |
| Supply voltage | 12.0 V DC |
| Operating frequency | 65.0 kHz |
| Dummy load for efficiency test | 150 kΩ pulling 5.0 mA rms |
The driver is powered from a fixed 12.0 V DC supply.
The circuit operates at a nominal frequency of 65.0 kHz.