Datasheet Texas Instruments UC3855ADWTR — Datenblatt

application
INFO
available UC2855A/B
UC3855A/B High Performance Power Factor Preregulator
FEATURES DESCRIPTION Controls Boost PWM to Near Unity
Power Factor The UC3855A/B 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, the UC3855
utilizes an active snubbing or ZVT (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. Improved signal to noise ratio
and negligible current sensing losses make this an attractive solution for
higher power applications. Fixed Frequency Average Current
Mode Control Minimizes Line Current
Distortion Built-in Active Snubber (ZVT) allows
Operation to 500kHz, improved EMI
and Efficiency Inductor Current Synthesizer allows
Single Current Transformer Current
Sense for Improved Efficiency and
Noise Margin Accurate Analog Multiplier with Line …