UC3855 Datasheet PDF

●The UC3855BDW is a high-performance Power Factor Preregulator provides all the control features necessary for high power, high frequency PFC boost converters. The average current-mode control method allows for stable, low distortion AC line current programming without the need for slope compensation. In addition, it utilizes an active snubbing or zero voltage transition technique to dramatically reduce diode recovery and MOSFET turn-on losses, resulting in lower EMI emissions and higher efficiency. Boost converter switching frequencies up to 500kHz are now realizable, requiring only an additional small MOSFET, diode and inductor to resonantly soft switch the boost diode and switch. Average current sensing can be employed using a simple resistive shunt or a current sense transformer. Using the current sense transformer method, the internal current synthesizer circuit buffers the inductor current during the switch on-time and reconstructs the inductor current during the switch off-time.

● Controls Boost PWM to Near unity power factor

● Fixed frequency average current mode control minimizes line current distortion

● Built-in active snubber (ZVT) allows operation to 500kHz, Improved EMI and efficiency

● Accurate analog multiplier with line compensator allows for universal input voltage operation

● Overvoltage and overcurrent protection

● Precision 1% 7.5V Reference

● Green product and no Sb/Br