MAXREFDES113# Reference Design Block Diagram

Details

Introduction

Isolated power supplies provide reliable power regulation for a variety of applications. Transformer selection is

often the most difficult step in isolated power design. The MAXREFDES113# is a compact 24V input flyback

converter module that features 12V at 1.6A output. 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. In addition, through-hole pins on the

bottom side of the module allow for quick and easy integration of this power converter into the main system.

Pins are 15.24mm (0.6in) from power to ground, and 27.94mm (1.1in) from the input side to the output side.

The MAX17596 is a peak-current-mode controller for design of wide input-voltage flyback and boost

regulators. 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 100kHz to 1MHz 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

200kHz. For EMI-sensitive applications, the MAX17596 incorporates a programmable frequency

dithering scheme, enabling low-EMI spread-spectrum operation.

The input undervoltage lockout (EN/UVLO) is provided for programming the input-supply start voltage

(set to 17V in the design), and to ensure proper operation during brownout conditions. The EN/UVLO

input is also used to turn on/off the IC. The overvoltage input (OVI) protection scheme is provided to

make sure that the controller shuts down when the input supply exceeds its maximum allowed value

(set to 36V in the design).

A capacitor is connected to the SS pin to program the soft-start period hence reduces the input inrush

current during startup. Hiccup-mode overcurrent protection and thermal shutdown are provided to

minimize dissipation in overcurrent and overtemperature fault conditions.

The reference design delivers a peak efficiency of 87% with the supplied components when the input

is 24V. This general-purpose power solution can be used in many different types of power

applications, such as programmable logic controllers (PLC), industrial process control, industrial

sensors, telecom power supplies, isolated battery chargers, servers, and embedded computing.