UCC2819A

UCC2819A UCC3819A ą SLUS579 − OCTOBER, 2003 PROGRAMMABLE OUTPUT POWER FACTOR PREREGULATOR FEATURES D Controls Boost Preregulator to Near-Unity Power Factor D World Wide Line Operation D Over-Voltage Protection D Accurate Power Limiting D Average Current Mode Control D Improved Noise Immunity D Improved Feed-Forward Line Regulation D Leading Edge Modulation D 150-µA Typical Start-Up Current D Low-Power BiCMOS Operation D 10.8-V to 17-V Operation D Programmable Output Voltage (Tracking Boost Topology) BLOCK DIAGRAM OVP/EN 10 DESCRIPTION The UCC2819A/UCC3819A provides all the functions necessary for active power factor corrected preregulators. The controller achieves near unity power factor by shaping the ac-input line current waveform to correspond to that of the ac-input line voltage. Average current mode control maintains stable, low distortion sinusoidal line current. Designed in Texas Instrument’s BiCMOS process, the UCC3819A offers new features such as lower start-up current, lower power dissipation, overvoltage protection, a shunt UVLO detect circuitry and a leading-edge modulation technique to reduce ripple current in the bulk capacitor. The UCC3819A allows the output voltage to be programmed by bringing out the error amplifier noninverting input. VCC 15 7.5 V REFERENCE 9 VREF VAOUT 7 VSENSE 11 VAI 13 VFF 8 IAC 6 MOUT 5 VOLTAGE − ERROR AMP + X2 ÷X MULT X MIRROR 2:1 1.9 V − + 0.33 V CURRENT AMP − + ENABLE ZERO POWER − + 8.0 V + OVP − − PWM + OSC CLK SQ ...