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60 W power for box PCs without derating

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HFBC60-W/O - Customized DC/DC converter for box PCs in railway technology

How is that supposed to work?

Limited space, very high EMC requirements, individual connections, high ambient temperatures and everything passively cooled!

As a developer, have you ever asked yourself: How is this supposed to work?

It was precisely this situation that a renowned supplier of box PCs had to face and fulfill the following requirements:

  • Development of a completely new and super-compact box PC for harsh applications, primarily railway technology, with passive cooling
  • Use of modern architecture including high-speed processor and 5G modules
  • IP54 housing
  • DC input voltage from 14.4 V to 154 V with high efficiency over the entire range
  • DC output voltage of 12 V
  • Power 60 W without derating over a temperature range of -40 °C to 95 °C (immediate environment around the power supply unit), also with high efficiency over the entire input range
  • Conducted and radiated interference emission according to class B
  • Useful life time min. 20 years, maintenance-free
  • Max. Dimensions: 120 mm x 50 mm x 30.5 mm

A small and compact 50 W DC/DC converter for railrway technology with 24 V to 110 V input and 12 V output as an open frame was required.

With this information, it is easy to select a supposedly suitable converter from the portfolio and offer it to the customer. The range includes PCB-mountable DC/DC converters, open-frame devices, encapsulated converters, 19" plug-in units and top-hat rail devices. A dealer or manufacturer with limited interest in an optimal solution for the customer would, without asking, also go this route and not realize that none of the above-mentioned simple solutions really represent a solution for the customer.

During an initial meeting with the customer, the project data was exchanged with more details, so it quickly became clear that using a ready-made solution off the shelf would mean too many compromises in the customer's application.

Between the initial meeting with the customer and the ongoing communication, the customer continued to develop the BOX PC, so that further requirements had to be taken into account. These new requirements and adaptations can have an influence on the DC/DC converter and vice versa, the DC/DC converter can influence the customer's assemblies. If EMC-critical components (processor, 5G radio modules) of the customer board are moved close to the converter, this can have a huge impact on the interference immunity or interference emission on both sides. The same applies if the earthing concept is changed, which can then have an impact on the power supply.

In addition to EMC, there is also a high thermal load, e.g. from a high-performance processor. This is known from gaming PCs, where the CPU, GPU and semiconductors have to be cooled at great expense. In a passively cooled system, the housing serves as a heat sink for ALL components.

From an initially planned application of an IP40 housing, the customer changed his requirements to IP54. This meant that the original cooling concept, which had envisaged natural convection, could no longer be adhered to. The EMC was raised from class A to class B, the mounting location of the power supply unit was moved and therefore the contacting of the heat dissipation to the housing had to be reconsidered. In addition, it was determined that the consumers on the PC board require more peak power, especially the 5G modules, and therefore the converter must deliver 60 W continuously. And the full power must be available in all limit ranges (temperature and input voltage) without derating.

You can see: What did the customer ask for? Where have we ended up now?

The small difference is that the DC/DC converter is tailored precisely to his needs. As a bonus, everything fits into its own housing and works without the customer having to worry about how to get everything to work.

After placing the order, the customer was able to hold the first functional samples in their hands within 5 weeks, which fulfilled the basic electrical functions and allowed them to check the installation conditions.

In a further 7 weeks, very advanced devices were delivered to the customer in terms of EMC, which were immediately put through their paces in the customer's development department. The successfully tested prototypes prompted the customer to order a further 40 prototypes in order to build more test Box-Pcs. This means that box Pcs can be delivered to customers in the first project phase in order to test them directly in the end customer application.

With the customer-specific power supply, the customer was able to achieve market readiness of the new Box PC generation within a very short time. This was possible because the customer was able to focus on its core competencies and entrust the development of the DC/DC converter to the professionals at FORTEC Power. And without the restrictions that a COTS power supply, for example, would have entailed.

Fortec Power