Home Power management AC/DC & isolated DC/DC switching regulators Power factor correction (PFC) controllers

UC3855B

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Bipolar CCM PFC controller with 10.5V/10V UVLO and zero voltage transition, 0°C to 70°C

UC3855B is in the process of being discontinued
Consider one of these alternates:
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Same functionality with different pin-out to the compared device
UCC28056 ACTIVE 6-pin high performance CRM/DCM PFC controller fewer pins, more integrated protections, lower standby and operating current, higher VDD absmax
Similar functionality to the compared device
UCC28180 ACTIVE 18-kHz-250-kHz CCM PFC controller with enhanced startup & transient response Replacement

Product details

Topology Boost Control mode CCM Switching frequency (max) (kHz) 500 UVLO thresholds on/off (V) 10.5/10 Vin (max) (V) 20 Features > 750 W applications, Average current mode, Continuous Control Mode, Enable, Overvoltage protection Rating Catalog Operating temperature range (°C) 0 to 70 Duty cycle (max) (%) 95
Topology Boost Control mode CCM Switching frequency (max) (kHz) 500 UVLO thresholds on/off (V) 10.5/10 Vin (max) (V) 20 Features > 750 W applications, Average current mode, Continuous Control Mode, Enable, Overvoltage protection Rating Catalog Operating temperature range (°C) 0 to 70 Duty cycle (max) (%) 95
PDIP (N) 20 228.702 mm² 24.33 x 9.4 SOIC (DW) 20 131.84 mm² 12.8 x 10.3
  • 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
  • 150&mirco;A Startup Supply Current Typical
  • Precision 1% 7.5V Reference
  • 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
  • 150&mirco;A Startup Supply Current Typical
  • Precision 1% 7.5V Reference

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.

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 outputs 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 comparator, and overcurrent comparator complete the list of features. Available packages include: 20 pin N, DW, Q, J, and L.

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.

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 outputs 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 comparator, and overcurrent comparator complete the list of features. Available packages include: 20 pin N, DW, Q, J, and L.

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Technical documentation

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Type Title Date
* Data sheet High Performance Power Factor Preregulator datasheet (Rev. B) 27 Oct 2005
Application note U-153 UC3855A/B High Performance Power Factor Preregulator (Rev. A) 23 Sep 2003
Application note AC Requirements for Power Factor Correction Circuits 28 Mar 2002
Application note Accurate PWM Duty Cycle Clamp 25 Jan 2002
Application note DN-66 UC3854A/B and UC3855A/B Provide Power Limiting with Sinusoidal Input (Rev. A) 06 Nov 2001

Design & development

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PDIP (N) 20 View options
SOIC (DW) 20 View options

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