General description

The UBA2071 and UBA2071A are high voltage ICs intended to drive Cold Cathode Fluorescent Lamps (CCFLs) or External Electrode Fluorescent Lamps (EEFLs) for backlighting applications. They can drive a half bridge circuit made up of two NMOSFETs with a supply voltage of up to 550 V, so the inverter can be supplied directly from a 400 V PFC bus.

The UBA2071 and UBA2071A contain a controller, a level shifter, a bootstrap diode and drivers for the external half bridge power switches. It also contains a low frequency PWM generator, which can be used to control the brightness level of the lamps, using an analog brightness/dimming control voltage. PWM dimming can also be realized, using a digital PWM input signal. PWM dimming can be synchronized with other ICs. The lamp current is controlled by means of a true zero voltage switching resonant control principle, ensuring lowest possible switch losses in the half bridge power structure.

The UBA2071 is designed to be supplied by a ∆V/∆t supply from the half bridge circuit that it drives. The IC itself needs little current and if the IC is off, a clamp protects the supply voltage from getting too high.

The UBA2071A is designed to be supplied by a fixed 12 V supply. It has a lower supply start voltage and no supply clamp.

Features

■ Suitable for operating in a very wide inverter supply voltage range (up to 550 V DC).

■ Integrated level shifter.

■ Integrated bootstrap diode.

■ Lamp current control by means of a true zero voltage switching resonant control

principle.

■ Sample & Hold circuit, maintaining current control value during PWM lamp-off

situation.

■ Separately definable time constants for current control loop and PWM dimming

attack/decay setting.

■ Overvoltage control.

■ Overcurrent protection.

■ Ignition failure detection.

■ Hard switching control.

■ Arcing detection.

■ Open/short pin protections on feedback pins.

■ Integrated, programmable fault timer.

■ Bidirectional pin acting both as fault signaling output and input, allowing external fault

interfacing to operate via the integrated fault timer.

■ Brightness level adjustment through PWM dimming.

■ Integrated PWM generator.

■ Power-down mode.

■ Communication pin for master / slave operation.

■ DC blocking capacitor pre-charging sequence.

■ Supply clamp (UBA2071 only).

Applications

■ LCD-backlighting, including LCD-TV and LCD-monitor applications. The IC is intended

to drive and control a half bridge inverter with resonant load circuit for CCFLs, but can

also drive an array of External Electrode Fluorescent Lamps (EEFLs).