Flyback converters are the preferred topology in the SMPS (switched-mode power supply) for medium- and low-power range applications because they are simple and economic. They have less components and are efficient in isolating the output from input. They are used in battery-powered applications, universal AC/DC converters, and industrial and telecommunication equipment. Isolated converters traditionally regulate the output voltage and current by utilizing a secondary side regulation (SSR) composed of an optocoupler and secondary error amplifier.

The MAXREFDES1249 is a universal input (86V to 305V AC) offline-isolated power supply that works across all geographical regions. It delivers 36W DC at 48V suitable for Power over Ethernet (PoE) and telecommunication applications.

The design uses a MAX17595 peak-current-mode controller operated in the discontinuous conduction mode (DCM) of the flyback topology. The architecture efficiently regulates the output by utilizing the feedback network and current-sense, and controlling the duty cycle of the switching MOSFET (metal-oxide semiconductor field-effect transistor) for compact and cost-effective power conversion.

特征

Programmable frequency dithering for a low-EMI (electromagnetic interference) spread-spectrum operation
Programmable switching frequency optimizes the magnetic and filter components for compact, cost-effective, and efficient isolated/non-isolated power supplies
Isolation of 4000V AC between the primary and secondary sides
EMI and EMC (electromagnetic compatibility) compliant design
Programmable input enable/UVLO (undervoltage lockout) feature
Programmable input overvoltage protection
Adjustable soft-start
Hiccup-mode, short-circuit protection
Fast cycle-by-cycle peak current limit
Thermal shutdown protection
Space-saving, 16-pin, 3mm x 3mm TQFN (thin quad flat no-leads) package
Operating temperature range of -40°C to +125°C