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UC3854A

UNITRODE
Part Number UC3854A
Manufacturer UNITRODE
Description Enhanced High Power Factor Preregulator
Published Oct 17, 2015
Detailed Description Enhanced High Power Factor Preregulator UC1854A/B UC2854A/B UC3854A/B FEATURES • Controls Boost PWM to Near Unity Powe...
Datasheet PDF File UC3854A PDF File

UC3854A
UC3854A

Overview
Enhanced High Power Factor Preregulator UC1854A/B UC2854A/B UC3854A/B FEATURES • Controls Boost PWM to Near Unity Power Factor • Limits Line Current Distortion To <3% • World-Wide Operation Without Switches • Accurate Power Limiting • Fixed Frequency Average Current Mode Control • High Bandwidth (5MHz), Low Offset Current Amplifier • Integrated Current and Voltage Amp Output Clamps • Multiplier Improvements: Linearity, 500mV VAC Offset (eliminates external resistor), 0-5V Multout Common Mode Range • VREF "GOOD" Comparator • Faster and Improved Accuracy ENABLE Comparator • UVLO Threshold Options (16/10V / 10.
5/10V) • 300µA Startup Supply Current UVLO Turn on UVLO Turn off UC1854A 16V 10V UC1854B 10.
5V 10V DESCRIPTION The UC1854A/B products are pin compatible enhanced versions of the UC1854.
Like the UC1854, these products provide all of 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 the AC input line voltage.
To do this the UC1854A/B uses average current mode control.
Average current mode control maintains stable, low distortion sinusoidal line current without the need for slope compensation, unlike peak current mode control.
The UC1854A/B products improve upon the UC1854 by offering a wide bandwidth, low offset Current Amplifier, a faster responding and improved accuracy enable comparator, a VREF "good" comparator, UVLO threshold options (16/10V for offline, 10.
5/10V for startup from an auxiliary 12V regulator), lower startup supply current, and an enhanced multiply/divide circuit.
New features like the amplifier output clamps, improved amplifier current sinking capability, and low offset VAC pin reduce the external component count while improving performance.
Improved common mode input range of the Multiplier output/Current Amp input allow the designer greater flexibility in choosing a method for current sensing.
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