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.