Automotive, Zero-power standby PSR flyback controller

The UCC28731-Q1

isolated-flyback power supply controller provides constant-voltage (CV) and

constant-current (CC) output regulation without the use of an optical coupler

minimizing board area plus BOM count for higher lifetime reliability. This device

processes information from the primary power switch and an auxiliary flyback winding

for precise regulation of output voltage and current, hence the label "PSR".

A minimum switching frequency of 32Hz

facilitates achieving less than 5mW of no-load power. An internal 700V start-up

switch, dynamically- controlled operating states and a tailored modulation profile

support ultra-low stand-by power without sacrificing start-up time. Control

algorithms in the UCC28731-Q1 allow operating

efficiencies to meet or exceed applicable standards. Discontinuous conduction mode

(DCM) operation with valley-switching reduces switching losses. Modulation of the

switching frequency and primary current peak amplitude (FM and AM) keeps the

conversion efficiency high across the entire load and line ranges.