The UCC28740 isolated-flyback power-supply controller provides Constant-Voltage (CV) using an optical coupler to improve transient response to large-load steps. Constant-Current (CC) regulation is accomplished through Primary-Side Regulation (PSR) techniques. This device processes information from opto-coupled feedback and an auxiliary flyback winding for precise high-performance control of output voltage and current.
An internal 700-V startup switch, dynamically controlled operating states, and a tailored modulation profile support ultra-low standby power without sacrificing startup time or output transient response.
Control algorithms in the UCC28740 allow operating efficiencies to meet or exceed applicable standards. The drive output interfaces to a MOSFET power switch. Discontinuous conduction mode (DCM) with valley-switching reduces switching losses. Modulation of switching frequency and primary current-peak amplitude (FM and AM) keeps the conversion efficiency high across the entire load and line ranges.
The controller has a maximum switching frequency of 100 kHz and always maintains control of the peak-primary current in the transformer. Protection features keep primary and secondary component stresses in check. A minimum switching frequency of 170 Hz facilitates the achievement of less than 10-mW no-load power.
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This is a high efficiency 65W AC/DC design using UCC24630 Synchronous Rectification Controller for a Universal input (85Vac to 265Vac) to 19.5V @3.33A output exceeding CoC-5 Tier2 and DOE Level VI performance requirements for external power supplies.
The UCC28740EVM-525 evaluation module is a 10W off-line discontinuous mode (DCM) flyback converter that provides constant-voltage (CV) and constant-current (CC) output regulation. It uses optical coupler feedback for tight voltage regulation and improved the transient response to large load steps (...)
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