MAXREFDES119#: Isolated 24V to 5V, 9W optocoupler-less flyback power supply

Maxim’s power supply experts have designed and built 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.

MAXREFDES119# is unique. While most isolated power supplies require an optocoupler, MAXREFDES119# does not use one. The design features the MAX17690, a peak-current-mode converter with flexible switching frequency, which measures primary-side voltage for system control, and the MAX17606, a secondary-side MOSFET driver that eliminates inefficient diodes. This efficient flyback topology provides a 5V output at 9W of power (1.8A) from a 24V input. This entire circuit fits on a 20mm (0.8in) x 60mm (2.35in) board.

As with all Maxim reference designs, the BOM, schematics, layout files, and Gerber files are all available from the Design Resources tab. In addition, boards are available for purchase; most boards feature through-hole pins for immediate board placement and accelerated prototyping.

Features

• Functional insulation
• Compact and flexible
• Minimal external components
• Robust operation in adverse industrial environments
• 5V 1.8A with 20% over range current
• ±5% output accuracy

Applications

• Industrial control and automation
• Process control
• PLC
• Telecom and datacom power supplies