Introduction

A Cincon converter or supply delivers its specified performance only when the design around it respects the derating, the thermal path and the filtering. The part itself is well specified, but the layout and the thermal design decide whether it runs cool and compliantly for years. This application note explains the practical rules for applying a Cincon DC-DC converter and an AC-DC supply in a real product power system for an industrial, a telecom or a railway design.

Load and Derating

A converter and a supply are rated at a temperature and a mounting, and they deliver less at a higher ambient, so the derating curve is the real specification. Compute the load, add margin for the start-up and the lifetime, and read the available power at the worst-case ambient, not the nominal. A part that runs at a lower fraction of its rating runs cooler and lasts longer, so a modest over-size is a good choice.

Thermal Path and Mounting

The thermal path from the part to the air or the chassis matters as much as the rating. A board-mount module spreads its heat into the board and the air, a 2x1 inch case spreads it more, and a baseplate part conducts it to the mounting surface. Leave clearance for an open-frame supply and a board-mount module, provide a good thermal path for a baseplate part, and measure the case and the baseplate temperature at the worst case.

Isolation and the Layout

An isolated module separates the input and the output for safety and noise immunity, so the design must respect the barrier. Keep the input and the output wiring separated, reserve the required creepage and clearance, and do not run a trace across the barrier, because a single trace defeats the isolation. Keep the input capacitor close and the switching loop small, and use a ground plane that does not bridge the barrier.

EMC and the Input Filter

A DC-DC converter reflects a ripple current onto the input, so it needs the recommended pi input filter, and the Cincon modules often include one. The Cincon CFM series meets the EN55032 Class B emission on its own, so the EMC is often designed in for the supply, but the layout still matters. Confirm the conducted emissions with the real load and the enclosure.

Efficiency and the Heat

The efficiency sets the loss and the heat, so compare it at the working load rather than at the full scale, and compute the loss to plan the thermal path. A higher efficiency keeps the enclosure cooler and allows a smaller thermal path, and a cooler part fails less. For a continuous duty, confirm the derating at the worst-case ambient and the load.

Medical Leakage

For a medical application, confirm the isolation and the leakage against the standard and the patient-contact limit, and choose a part with the medical approval where the design requires it. Keep the input filter and the leakage in mind, because the leakage is a safety limit for an equipment that touches a person.

Railway and Harsh Environment

For a railway or a harsh industrial design, choose a module that meets the EN50155, the EN50121-3-2 and the EN45545-2 standards, with an ultra-wide input and a baseplate or an enclosed chassis. Plan the input protection for the surge and the transient, confirm the ride-through class, and confirm the baseplate temperature at the worst case, because the environment is unforgiving.

Verification

Validate the design on the bench by measuring the efficiency and the derating at the worst-case load and ambient, by checking the ripple, the transient and the holdup, by confirming the isolation with a hipot test and by measuring the conducted emissions and the leakage with the real load. Our FAE team can review your measurements and your layout and help you interpret them, so the power system performs in the product as it does on the datasheet.