UNITRODE UC2855B
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.| Part No. | UC2855B |
|---|---|
| Datasheet | UC2855B Download |
| Manufacturer |  UNITRODE |
| Description | High Performance Power Factor Preregulator |
| Buy | Stock & Price |
FEATURES
● 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
● Inductor Current Synthesizer allows Single Current Transformer Current Sense for Improved Efficiency and Noise Margin
● Accurate Analog Multiplier with Line Compensator allows for Universal Input Voltage Operation
● High Bandwidth (5MHz), Low Offset Current Amplifier
● Overvoltage and Overcurrent protection
● Two UVLO Threshold Options
● 150µA Startup Supply Current Typical
● Precision 1% 7.5V Reference BLOCK DIAGRAM
DESCRIPTION
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.
