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UC2855BN Fiches technique(PDF) 1 Page - Texas Instruments |
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UC2855BN Fiches technique(HTML) 1 Page - Texas Instruments |
1 / 12 page UC2855A/B UC3855A/B DESCRIPTION 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 program- ming 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, result- ing in lower EMI emissions and higher efficiency. Boost converter switch- ing 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 us- ing a simple resistive shunt or a current sense transformer. Using the cur- rent 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. The UC3855A/B also features a single quadrant multiplier, squarer, and divider circuit which provides the programming signal for the current loop. The internal multiplier current limit reduces output power during low line conditions. An overvoltage protection circuit disables both controller out- puts in the event of a boost output OV condition. Low startup supply current, UVLO with hysteresis, a 1% 7.5V reference, voltage amplifier with softstart, input supply voltage clamp, enable com- parator, and overcurrent comparator complete the list of features. Avail- able packages include: 20 pin N, DW, Q, J, and L. BLOCK DIAGRAM High Performance Power Factor Preregulator 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 SLUS328A JUNE 1998 - REVISED MAY 2004 License Patent from Pioneer Magnetics. Pin numbers refer to DIL-20 J or N packages. UDG-94001-2 application INFO available |
Numéro de pièce similaire - UC2855BN |
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Description similaire - UC2855BN |
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