Maxim reference design sets out isolated 24V to 12V, 20W supply

September 04, 2016 // By Graham Prophet
Maxim has posted details of a series of isolated, industrial power-supply reference designs. Each of these power supplies efficiently converts 24V into useful voltage rails at a variety of power levels. Every power rail is isolated with a readily available transformer from multiple, global vendors, providing for quick, convenient transformer selection.

Each design has been tested for load and line regulation, as well as efficiency and transient performance: BOM, schematics, layout files, and Gerber files are all available in the Design Resources tab. Boards are available for purchase; most boards feature through-hole pins for immediate board placement and accelerated prototyping.

MAXREFDES113# is an efficient flyback topology with 24V input, and a 12V output at 20W of power (1.6A). The design features the MAX17596, a peak-current-mode converter with flexible switching frequency. This entire circuit fits on a 20 × 35mm board. A related design, MAXREFDES114, delivers 5V from 24V.

Maxim notes that, transformer selection is often the most difficult step in isolated power design. Multiple transformers (Halo Electronics TGSP-P153EP13LF, Wurth Electronics 750316112r01, HanRun HR051441, and Sumida 13324-T115) have been qualified for this design, simplifying the process of transformer selection. The reference design operates over a 17V to 36V input voltage range, and provides up to 1.6A (plus 20% overhead) at 12V output. The MAX17596 has an internal amplifier with 1% accurate reference, eliminating the need for an external reference. The switching frequency is programmable from 100 kHz to 1 MHz with an accuracy of 8%, allowing optimization of magnetic and filter components, resulting in compact and cost-effective power conversion. This design is set to switch at 200 kHz. For EMI-sensitive applications, the MAX17596 incorporates a programmable frequency dithering scheme, enabling low-EMI spread-spectrum operation.