1. Description
Design goals for a Cold Cathode Fluorescent Lamp (CCFL)
inverter for use in a notebook computer or other portable
applications include small size, high efficiency, and low cost.
The FAN7311 provides the necessary circuit blocks to
implement a highly efficient CCFL backlight power supply
in 20-SSOP and 20-SOIC packages. The FAN7311 typically
consumes less than 4mA of operating current, improving
overall system efficiency. External parts count is minimized
and system cost is reduced by the integration of features
including; feedback-controlled Pulse Width Modulation
(PWM) driver stage, soft start, open lamp regulation, and
Under Voltage Lockout protection (UVLO). The FAN7311
includes an internal shunt regulator that allows operation
with an input voltage from 5V to 25.5V. It supports analog
and burst dimming modes of operation. The FAN7311 provides
open lamp regulation and protection. Open lamp regulation
protects the transformer from over-voltage during start
up or when an open lamp occurs. The transformer voltage is
regulated by reducing duty cycle when an over-voltage is
detected. Open lamp protection can be used to shut down an
IC when an open lamp condition continues longer than a
specified time.
