Modified standard, semi-custom and full-custom designs – the RECOM approach

One of the reasons RECOM has the broadest power converter portfolio in the industry is the sheer number of variations available within our standard product range. If we take a classic 5W isolated and regulated DC/DC converter in a DIP24 case, the REC5 series (for example), then the datasheet explains that it has five input and nine output voltage range options, including single and dual outputs.

There are three different isolation voltage options from 2kV up to 6kV and three different pinning options to make it a pin-compatible alternative to the competition, including a version with a remote on-off pin. Additionally, the board mounting pins can be through-hole or SMT. The case material can be plastic or metal. Finally, the series is available with either tube or tape-and-reel packaging options. Overall, for this one DC/DC converter series, there are well over two thousand permutations as standard!

The boundary between a semi-custom and a modified standard power converter is not always obvious, so a useful definition is whether safety re-certification is needed. Modifications that influence safety-critical components or separations – such as the transformer construction, choice of optocoupler or Y-capacitor, or creepage or clearance distances – will almost certainly require a new certification process. However, the safety test reports typically allow a ±10% variation in the output voltage and current rating to accommodate production tolerances, leaving some scope for flexibility.

The input voltage rating also has at least a ±20% tolerance and often more. If the required modification can respect these tolerance bands, then safety re-certification may not be required. The same applies if the original safety test report lists ‘alternate construction’ options for certain components or the potting materials. We have customer applications where silicone potting material is unacceptable, either because of the possibility of outgassing, which could affect other parts or because silicone could emit smoke in a fire, so although silicone is an excellent encapsulation material with high thermal conductivity and good adhesion, we could offer these customers epoxy potting as a modified standard.

It may seem surprising, but the label design and text are considered part of the safety documentation and are very carefully controlled by the certifying bodies. We regularly receive requests for a custom label design with, for example, the customer’s own brand name and part number instead of RECOM’s standard label. Although physically the two parts would be identical, we would need to apply for a copy certificate with the new label, part number and customer logo to manufacture this modified part with valid safety certification. However, we have experience in handling such requests and we strive to make the process as fast, simple and unbureacratic as possible.

Once we enter the realm of semi-custom power converters, then we can offer much more flexibility than simply tweaking the specifications, such as using alternative PCB layouts to change the shape of the converter or matching the pinout to replace a competitor’s part that has been rendered obsolete. The changes do not need to be physical; we have made semi-custom converters that use higher-rated components to extend the operating temperature range or harder epoxy to allow the converter to meet specific environmental conditions. All of these modifications are based on standard designs, so although a semi-custom product meets individual customer requirements for form, fit or function, it can still be manufactured quickly and cheaply on our standard production lines with a short time-to-market.

In 2010, a US competitor abruptly stopped manufacturing a series of switching regulators, leaving their existing customer base ‘in the lurch.’ One customer approached us, asking if we could modify our standard R-78 series to be pin-and-function compatible with these end-of-life products, even though the format was completely different from our existing design.


In only 12 weeks, we released the R-78T series with three different open-frame SMD pinning options, designed to be pin-compatible with these no longer available parts. The reason we could react so swiftly was that we did not need to start from ground zero – we already had extensive experience in designing and manufacturing switching regulator modules and could use this as a base for the semi-custom design.

A full-custom power converter differs from the modified standard or semi-custom variants because it is not based on an existing product, but it obviously uses proven and tested building blocks and existing production infrastructure where appropriate. Typical requirements that would make a custom power converter project viable would be that no existing product can fulfil the need, that the costs (R&D, testing and production) are viable for both partners, and that the project volume justifies the investment in resources.

The typical custom power converter project stages are shown in Figure 5:

As can be seen by this brief introduction, a RECOM power converter can be offered as a modified standard, semi-custom or full-custom product to the customer in several ways. Each variant has advantages and disadvantages (Figure 6), so the simplest way to decide is to establish a dialog with us so we can advise and work together with you to offer the optimum solution.

To facilitate this, RECOM has set up four dedicated e-mail addresses for customisation requests. Someone from RECOM will then contact you to discuss your requirements in more detail.

Contact RECOM to discuss your project and for advice on how to specify your fully custom, semi-custom or modified-standard power converter for minimum cost and fastest delivery.