1.General descriptionThe UBA2071 and UBA2071A are high voltage ICs intended to drive Cold CathodeFluorescent Lamps (CCFLs) or External Electrode Fluorescent Lamps (EEFLs) forbacklighting applications. Theycan drive a half bridge circuit made up of two NMOSFETswith a supplyvoltage of up to 550 V, so the inverter can be supplied directlyfrom a 400 VPFC bus.The UBA2071 and UBA2071A contain a controller, a level shifter, a bootstrap diode anddrivers for the external half bridge power switches. It also contains a low frequency PWMgenerator, which can be used to control the brightness level of the lamps, using an analogbrightness/dimming control voltage. PWM dimming can also be realized, using a digitalPWM input signal. PWM dimming can be synchronized with other ICs. The lamp current iscontrolled by means of a true zero voltage switching resonant control principle, ensuringlowest possible switch losses in the half bridge power structure.The UBA2071 is designed to be supplied bya ∆V/∆t supplyfrom the half bridge circuit thatit drives. The IC itself needs little current and if the IC is off, a clamp protects the supplyvoltage from getting too high.The UBA2071A is designed to be supplied by a fixed 12 V supply. It has a lower supplystart voltage and no supply clamp.2.FeaturesI Suitable for operating in a very wide inverter supply voltage range (up to 550 V DC).I Integrated level shifter.I Integrated bootstrap diode.I Lamp current control by means of a true zero voltage switching resonant controlprinciple.I Sample & Hold circuit, maintaining current control value during PWM lamp-offsituation.I Separately definable time constants for current control loop and PWM dimmingattack/decay setting.I Overvoltage control.I Over...
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