SLUSD37E October 2017 – November 2019 UCC28056
The UCC28056 controller followed with the UCC256403/4 LLC controller device to provide a complete PFC and LLC isolated off-Line power supply system. The combined power supply is designed to meet tough efficiency and standby power requirements without the need for an Auxiliary Flyback converter and with no need to switch off the PFC under light load conditions. It allows designers to meet modern green power standards with a simpler and lower system cost of power supply.
The controller contains a number of features designed to maximize operating efficiency across the entire range of Line and Load. A versatile CrM/DCM control algorithm allows UCC28056 to operate in transition mode at full power and then transition seamlessly into DCM at reduced load without compromising Line current harmonics or power factor. The controller operates at maximum frequency (Transition mode) when delivering full load and then automatically reduce switching frequency, moving to DCM operation, when delivering reduced load for maximum efficiency.
Light-load efficiency and standby power are further enhanced by transitioning automatically to a burst mode of operation when delivering less than 10% load for UCC28056C variants and 15% load for UCC28056A/B. During the burst OFF periods, the controller powers down most of its internal circuits to minimize controller power consumption.
The UCC28056 controller includes a comprehensive list of fault protection features such as cycle-by-cycle current limit, over-current protection, dual independent output over-voltage protection, Line Brown-In, Over-temperature protection and supply undervoltage lockout (UVLO).
Quantised 7-level line voltage feed-forward ensures that the loop gain is almost independent of line voltage, to ease design of the output voltage control loop. A non-linear error amplifier greatly improves the response to large steps in load without compromising steady state Line current harmonics.