System Board 7055

MAXREFDES1234: Miniature 5W DC-DC Flyback Converter Using the MAX17596

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Input Type VIN (MIN)
Isolated/Non-Isolated Topology
DC 24 160 1 Single 5 5 Isolated Flyback

Flyback converters are the preferred topology in isolated converters for medium and low power range applications due to their simplicity and economic considerations. As flyback converters are isolated converters, the output voltage and the current are traditionally regulated by utilizing the secondary side regulation (SSR) composed of an optocoupler and a secondary-error amplifier.

The MAXREFDES1234 is a miniature, isolated power supply that can deliver 5V at 1A of load current. The design uses the MAX17596 peak-current-mode controller operated in discontinuous-conduction mode (DCM) flyback topology to efficiently control the MOSFET switching, current sense, output-voltage feedback sense, and optimization. An additional bias winding provides a power supply to the device under operating conditions so that the primary winding of the flyback transformer can function at high input voltages up to 160V.

Key Features

  • Miniature Design Optimized for Small Size
  • 24V to 160V Input Range
  • Isolated Output of 5V DC at 5W
  • Cycle-by-Cycle Current Limit
  • Resistor-Programmable UVLO/OVI Threshold
  • Low-Cost DCM Flyback Design
  • Galvanic Isolation Up to 1500VRMS
  • Proven PCB Layout
  • Fully Assembled and Tested
MAXREFDES1234 Board - Top Enlarge+ MAXREFDES1234 Board - Bottom Enlarge+

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Designed, Built, Tested

This document describes the hardware shown above. It provides a detailed, systematic technical guide to designing a DC-DC DCM flyback using Maxim’s MAX17596 current-mode controller. The power supply has been built and tested, details of which follow later in this document.

Design Resources


Peak-Current-Mode Controllers for Flyback and Boost Regulators

  • Programmable Switching Frequency Allows Optimization of the Magnetic and Filter Components, Resulting in Compact, Cost-Effective, Efficient Isolated/Non-Isolated Power Supplies
  • Programmable Frequency Dithering Enables Low-EMI Spread-Spectrum Operation
  • Integrated Protection Features Enhance System Reliability