Six pin high performance CRM/DCM PFC controller

24th August 2018

Anna Flockett

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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 while keeping the PFC ‘always on’. When used with the LLC controller UCC256301, this 6-pin device eliminates the need for an auxiliary fly back converter, (typically needed in systems for good standby performance) while achieving less than 80 mW at 230 Vac. The device also enables instant turn on while reducing external component count to a minimum.

Features include:

Low input current distortion and near unity power factor down to 10% load
- Enables compliance to IEC1000-3-2
Ultra-low no-load input power (25mW at 115Vac, 40mW at 230Vac)
Excellent efficiency over range of load
Enables <60mW standby power at 115Vac and <80mW standby power at 230Vac in PFC+LLC system
Enables compliance to green power standards without disabling PFC
- EuP Lot 6 Tier 2, CoC Ver. 5 Tier 2, energy star for computers ver. 6.1, DOE level VI
Ultra-low audible noise output
Burst mode with soft-entry and soft-exit periods
Enhanced EA, responds rapidly to load steps without degrading input current distortion
Valley synchronised turn-on requires no second winding on the boost inductor
User adjustable valley delay
Low start-up current consumption (<46 µA)
Wide VCC range 8.5-34V
Cycle-by-cycle current limit
Second independent output voltage protection
Integrated over-temperature protection