Designing more functionality, flexibility, power in dc/dc converter boards

The Ericsson BM456/457 dc/dc converters are the first models in the second generation of digital Advanced Bus Converter (ABC) products. They target information and communication technology (ICT) companies that needed more advanced functionality and higher levels of flexibility from board-mounted power source manufacturers. To achieve this, designers are now combining at the board level a number of power units that integrate PMBus interfaces, such as power interface modules, ABCs and PoL regulators. In addition, the datacom industry, working on an ac-source and converting via narrow-output voltage rectifiers to 48 or 52 V, require an increased level of output power per quarter-brick module, provided by these Ericsson products.

Core members of the BM456/457 design team – left to right: Henrik Borgengren, Anders Kullman, Fredrik Wahledow, Jonas Malmberg, Jan Arvidsson

The company used a small core design team that was supported by dedicated resources from different design units including thermal simulation and verification to develop the dc/dc converters. Their biggest challenge was developing a new product at the same time as a new control IC plus firmware. When they were developing the first ABC platform — called FRIDA I — and integrated digital control and power management, the company explored new ways to optimize energy utilization and make it possible for system architects to increase the integration of dc/dc converters within the rest of the digital chain. Working in close cooperation with silicon vendors, Ericsson achieved the development of such a product, but also faced an immediate demand for more advanced features and an increased level of power required by the datacom industry.

Increasing the level of functionality and making the power module even more efficient meant that the R&D team had to significantly increase the level of embedded software (firmware) while also increasing the number of commands executed by the processor. As there was no suitable control IC available, they had to work in close cooperation with silicon vendors to develop the new control IC for the second-generation FRIDA II, in parallel with developing the product.

In addition to the complexity of developing a new platform at the same time as the control IC, there was an additional level of complexity with the development of new algorithms to optimize the built-in power management. Very few software designers combine power-switching expertise with knowledge of developing complex program algorithms.

The development of the firmware required the team to take a step-by-step approach and develop a process for design, verification, and validation, and finally function-by-function implementation. In the development of this new process, the most difficult part was to balance functionality with processing power. The switching cycle and timing events, combined with analog delays and sampling limitations, called not only for accuracy, but also thorough verifications and quality checks.

The result of this process was the Ericsson Energy Optimizer Firmware, which optimizes operational parameters to any type of load or line transients such in the case of ATCA switching from Feed A to Feed B.

This type of complex project normally takes about 36 months. However, due to the expertise gained from the first-generation FRIDA I, by combining the development of software and firmware in a single core team, together with the company’s knowledge of energy management and dedicated algorithms, creating the BM456/457 dc/dc converters took only 18 months.