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.