JAJSHT2C august 2019 – december 2020 UCC28740-Q1
PRODUCTION DATA
The UCC28740-Q1 is a flyback power-supply controller which provides high-performance voltage regulation using an optically coupled feedback signal from a secondary-side voltage regulator. The device provides accurate constant-current regulation using primary-side feedback. The controller operates in discontinuous-conduction mode (DCM) with valley-switching to minimize switching losses. The control law scheme combines frequency with primary peak-current amplitude modulation to provide high conversion efficiency across the load range. The control law provides a wide dynamic operating range of output power which allows the power-supply designer to easily achieve less than 30-mW standby power dissipation using a standard shunt-regulator and optocoupler. For a target of less than 10-mW standby power, careful loss-management design with a low-power regulator and high-CTR optocoupler is required.
During low-power operating conditions, the power-management features of the controller reduce the device-operating current at switching frequencies below 32 kHz. At and above this frequency, the UCC28740-Q1 includes features in the modulator to reduce the EMI peak energy of the fundamental switching frequency and harmonics. A complete low-cost and low component-count charger-solution is realized using a straight-forward design process.