1 Features
1• Ultra-low no-load input power enables < 80-mW
standby power at 230 VAC in PFC+LLC system
• Excellent light load efficiency and high efficiency
over wide range of load due to multi-mode TM
and DCM control
• Enables low system cost through FET drain valley
synchronized turn-on which eliminates need for
second winding on the boost inductor
• Enables compliance to green power standards
without disabling PFC
– EuP Lot 6 Tier 2, CoC Ver. 5 Tier 2, Energy
Star Ver. 6.1, DoE Level VI
• Burst mode with soft-entry and soft-exit periods
enables ultra-low audible noise output
• Enhanced error amplifier, responds rapidly to load
steps without degrading input current distortion
• User adjustable valley delay ensures valley
switching
• Low start-up current consumption (<46 μA)
• Wide VCC range 8.5 V to 34 V
• Cycle-by-cycle current limit
• Second independent output over-voltage
protection
• Integrated over-temperature protection
• Create a custom design using the UCC28056
device with the WEBENCH® Power Designer

2 Applications
• Desktop computing and digital TV
• Gaming, set top box and AC adapter front end
• LED drivers and luminaries
• Industrial and medical power supplies, e-bike
chargers, power tools chargers

3 Description
The UCC28056 device drives PFC boost stages
based on an innovative mixed mode method that
operates in transition mode (TM) at full load and
transitions seamlessly into discontinuous conduction
mode (DCM) at reduced load, automatically reducing
switching frequency. This device incorporates burst
mode operation to further improve light load
performance, enabling systems to meet challenging
energy standards while eliminating the need to switch
off the PFC. UCC28056 can drive a PFC power stage
up to 300 W, ensuring sinusoidal line input current
with low distortion, close to unity power factor. When
used with the LLC controller UCC256403/4, and dual
synchronous rectifier controller UCC24624 less than
80 mW system standby power can be achieved,
enabling PFC always on architecture and eliminating
the need for an auxiliary converter. This with FET
Drain valley turn-on with simple boost inductor allows
fewest component count and reduced system cost.