Flux & Micross: Partnering up for excellent EMI performance

Micross was chosen to develop and manufacture DC/DC converters for power RF circuitry for the OneWeb satellite constellation. Micross partnered with Flux to carry out the critical task of manufacturing, testing, and screening the magnetic components ensuring they met the highest standards of quality and performance.

Strategic collaboration

The project posed a challenging specification, requiring five outputs, high power efficiency, and a significantly reduced price point compared to classical space power electronics. Uncompromising on performance and reliability, Micross formed a strategic partnership with Flux to embark on the development and production journey, resulting in the delivery of 2,000 isolated DC/DC converters.

Rigorous screening and testing

The magnetic components were a key cost factor for the space-grade DC/DC converters. Crafting magnetic components for a task like this required the utmost precision in manual craftsmanship, alongside rigorous screening and testing protocols. Moreover, custom designs were imperative to fulfill the stringent electrical performance criteria. Although the chosen topology, a flyback converter, theoretically only requires one magnetic component, the need for high efficiency led to use of synchronous rectification with associated gate drive transformers, as well as a current transformer instead of a sense resistor for the converter PMW control scheme.

Since 1995, we've adhered to US standards (MIL-STD-981 / MIL-PRF-27), leveraging this experience to craft components tailored for American aerospace needs. To uphold the highest standards, Micross cooperated with Flux for the manufacturing, testing, and screening of their renowned PBC-based isolated space-grade DC/DC converters. Typically, such converters in classical space applications employ full-custom magnetic designs to achieve unparalleled performance. The product assurance methodology employed for the OneWeb DC/DC converter adhered to the same rigorous design principles, derating criteria, and finite element modeling as established in classical space, ensuring predictability and reliability in performance.

Combining customs and COTS to meet the cost

We used a mix of COTS magnetic and custom magnetic designs to meet the cost target. While COTS serve for non-performance setting elements such as signal transformers and output chokes, custom magnetic designs were required for the performance setting fly-back transformer. The key parameters for the fly-back transformer included minimum cross regulation between the five outputs, low power loss, and low cost.

While custom bobbins and cores are standard in Micross’ line of classical space DC/DC converters, they were not an option for the OneWeb project due to cost constraints. Therefore, Micross and Flux meticulously selected from available COTS bobbins, wires, and cores to balance between design, performance, manufacturability, and cost. Despite the limitations posed by commercially available bobbins, the partnership innovatively addressed thermal performance challenges by developing a custom-designed heatsink winding. These components were produced at our HiRel production in Thailand, Flux International Ltd., to meet the cost requirements suitable for Commercial Space.

A partnership resulting in exceptional EMI performance

This collaborative effort generated outstanding results, particularly evident in the exceptional EMI performance—a critical requirement for DC/DC converters used in RF applications. More than 1,800 units of the final DC/DC design were produced, incorporating more than 9,000 magnetic components, proving the effectiveness of the partnership and the ingenuity in addressing complex challenges.

We are very proud of having been a part of this successful collaboration and sharing our expertise in the testing, screening, and manufacturing of the magnetic components required to reach these impressive results.

Do you want Flux to help you in your next project? Contact Lars Gregersen, our COO of Defence and Space, to learn more and let us unfold how we can help you.