Posted on 18 February 2019

Unlocking Digital Power

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This is a story of change, a story that began 5 years ago when a small power company entered an uncertain market dominated by larger firms. Unlocking the true potential of digital power has required an approach very different to what had traditionally existed in the power supply industry. This company’s vision to collaborate and think creatively has changed the way the entire industry now approaches the board mount power market.

By Mark Adams, CUI

CUI is the company that entered into the digital power market at a time when only a few large firms dominated the space. As is typical with any new and exciting technology, the introduction of digital power to the market was not smooth. CUI knew that their approach to the market had to be different because this was a very different technology compared to analog solutions of the past. The technology had the potential to open up a range of new possibilities for system and board level designers, but with this potential also came a perception of complexity. CUI knew that in order for digital power to spread beyond the large tier 1 organizations with vast in-house design resources, they needed to take this technology and simplify it, similar to the way the FPGA market did in the late 90’s to address a space that was dominated by ASICs.

Up until CUI entered the market, digital power technology was primarily being implemented at a discrete semiconductor level. Power module companies were primarily focused on custom designs rather than general market release products for two primary reasons. First, many module companies perceived the customer support requirements for a standardized digital module platform as too great. Second, the digital power marketplace was in the midst of a significant lawsuit that forced a delay in product development by numerous power supply and semiconductor companies.

In 2005, Power One went to court versus Artesyn for a series of patents that they had on serial bus communication within a digital point of load (POL) device. In 2007, the courts sided with Power One, immediately stalling the development path of many power supply and semiconductor companies designing with the technology. When CUI started looking at the market in early 2009, they knew that the Power One patent for this technology was a major barrier to entry . At the time, Power One had only licensed this patent to semiconductor companies because they had their own interests in the point of load space. In September of 2009, CUI and Power One announced that they had signed a non-exclusive license agreement for their digital power IP - a first for a power supply company. This was a major step for the market in opening up the technology beyond a single source solution, and representative of the way CUI would approach the market moving forward - to work collaboratively with others in an open, transparent, and honest manner - with their customers, technology partners, and competitors. With the intellectual property concerns addressed, CUI began development of their first modules with the understanding that their product was only as good as the IC technologies that they integrated. With this in mind, CUI began to look for strategic partnerships with semiconductor companies that possessed IP that would help to simplify implementation of digital power for the customer.

Based on initial market feedback, one of the most complicated factors in implementing this new technology was proper compensation of the circuit. Finalizing the circuit compensation required special tools and many dedicated man hours. To address this, CUI partnered with Powervation; a controller company founded in 2006 out of Cork, Ireland and backed by Intel and TSMC. Powervation had technology that would allow for auto-compensation within the circuit, providing customers with the means to bypass the traditional practice of building in margins to account for factors such as component aging, manufacturing variations, and temperature. The ability for the module to dynamically achieve optimum stability in real time as conditions change was important to not only provide a superior product to the market, but also to allow for the technology to be more easily adopted. In September 2009, CUI announced the industry’s first auto-compensated digital POL modules in a push to take the technology beyond the traditional tier 1 companies in an initiative they dubbed as “Simple Digital”.

The market began to embrace digital power technology for the value it added to the system and the fact that it could dramatically shorten designs in the most sophisticated circuits - but this was still not a simple transition for many customers. In the power space, “sole source” is a dirty word. Because digital power was still a relatively new technology, multi-source options were not yet available to customers, creating another barrier to digital power’s mass adoption. To address this, CUI and Ericsson Power Modules began talks to create a cooperation based on a set of common footprints. For the previous 2 years, Ericsson Power Modules and CUI had competed in the same space for the same customers. However, they also competed against the fact that customers would not accept a single source design. Thus, in July 2011, Ericsson Power Modules and CUI announced a collaboration to provide their customers with an alternate source for their digital power products, an industry first.

The NDM2Z Series based on an Intersil controller was the first fully digital POL module to offer a dual source option to customers

As part of this collaboration, CUI uncovered yet another possible barrier to mass-adoption of digital power technology. PMBus was established as an open standard power-management protocol. The command language is intended to enable communication between components of a power system: CPUs, power supplies, power converters, and more. However, it doesn’t guarantee interoperability between digital ICs from different manufacturers. To address traffic issues on the main bus, semiconductor manufacturers developed their own proprietary serial buses to alleviate the burden. The commands transferred over the secondary serial buses are not standard, varying from vendor to vendor. If an engineer were to mix ICs from different vendors within a digital system, it becomes imperative that the documentation is extremely thorough. If the software platform on a board is not accurately written, catastrophic failures could occur. For example, in Figure 2 you will see a system with a host controller.

The same PMBus Vout command sent to 4 different digital controllers creates 4 unique and potentially catastrophic outputs

This controller sends out a simple Vout command to change the voltage of each rail to 1.0 V. The data format and exponent value for each rail is provided from 4 leading digital power IC vendors. 1.0 V is sent to the first rail with the appropriate command, and then subsequently sent to the other 3 power rails. In this example, the other controllers will change output voltages anywhere from 1.6 V to 8.0 V - creating the potential of catastrophic failure on this board. In short, a PMBus logo does not guarantee compatibility.

With this revelation in hand, CUI set out to educate customers, partners, and even competitors that interoperability was an issue that needed to be considered and addressed in order for digital power to propagate throughout the industry. And because the existing Powervation design could not provide a true 2nd source to the Ericsson footprint due to the PMBus interoperability issues between the controllers, CUI created a second POL family based on Intersil’s digital controllers. Since 2011, CUI has been focused on the continuation of product development to create a platform of easy to implement digital solutions. This has never been a more daunting task as the power supply requirements of today’s advanced designs become more complex. The market has made a shift, in a very quick manner, to a new era of power conversion. Simply converting one voltage to another is no longer adequate. Now, converting one voltage to a perfect voltage, under all conditions, all of the time is mandatory.

This is evident when you look at the transition in power supplies needed for a technology that is abundant across all markets, the FPGA. As FPGA geometries reduce with each successive generation, so have the core voltages and allowable voltage tolerances within the device.

As FPGA geometries reduce with each successive generation, so have the core voltages and allowable voltage tolerances within the device

To address this rapidly growing challenge, CUI set out to acquire IP that could integrate with digital control technology to better address the lowering core voltages, rising current densities and tightening tolerances of advanced ICs. In March 2010, CUI signed an exclusive license agreement for a SEPIC-fed buck topology that would be branded as “Solus”. This technology would allow CUI to reach performance levels that others could not.

Solus Power Topology’s Sepic-Fed Buck design allows for a significant reduction in switching losses compared to a standard buck design

CUI’s Solus® Power Topology provides advantages in isolated and non-isolated dc-dc converter designs through a significant reduction in switching and conductivity losses. Very simply, the Solus Topology combines a single-ended primary-inductor converter (SEPIC) with the conventional buck topology to form the SEPIC-fed buck converter. Lower voltage and current stresses in the topology coupled with an inherent GCE (gate charge extraction) process allows the new topology to reduce switching turn-on losses by 75% and switching turn-off losses by 99% on the control FET when compared to a conventional buck converter. Total efficiency is further increased by distributing the energy delivery into multiple paths, reducing circuit conduction losses by nearly 50%. The rich feature set of the Solus Topology is allowing CUI to accelerate the performance trend trajectories for the big-four power conversion needs in their latest designs: higher power density , higher efficiency for “greener” systems, faster transient response, and lower EMI.

In March of 2014, CUI released its first non-isolated digital POL based on the technology. The NDM3ZS-60 was a 60A module that delivered 20% more power in the same space as competing products, equivalent transient performance with one-third the output capacitance of other solutions, and a reduction in power losses by almost 25% versus best in class products on the market, thus addressing the needs brought on in today’s application – power loss, power density, and power accuracy.

CUI’s NDM3ZS-60 was the company’s first non-isolated digital POL based on Solus Power Topology.

On top of the growing need for perfect power conversion, the capabilities of digital power are quickly moving from an “optional” to a “required” technology thanks to the effects of Moore’s Law. As the geometries of new semiconductors continue to drop, semiconductor manufacturers are looking for ways to increase yields and also provide options to customers that allow them to optimize between performance and power consumption. However, in order to achieve this, power rails need to be digitally controlled and need to have the capability to be adjusted dynamically with a simple command. An example of this is Altera’s new SmartVoltage ID. In Altera’s Arria 10 FPGA, they will program an “ID” into the chip during testing that will allow a customer to read that ID. They will then know how low they can operate the core voltage while still meeting the performance benchmarks of the device. The customer can then adjust their power supply rail accordingly.

According to IHS, the digital power market is expected to grow 3.5 to 5 times over the next 4 years.

The trends driving digital power to a “required” aspect of today’ s pow - er systems are highlighted in recent forecasts from market analysts. According to Jonathon Eykyn, Power Supply and Storage Component Senior Analyst for IHS, digital power is now well-established in the server and telecommunication markets. However, IHS is now starting to see growing adoption across a much broader range of products and applications, which is driving rapid growth. IHS expects the market for digital power to grow 3.5-5 times between now and 2018 with the majority of the growth coming from customers outside of the traditional server and telecom space.

Due to this accelerating market growth, CUI has recognized the need for further collaboration in the industry to meet customer needs and stay ahead of technology advancements. In October 2014 CUI, Ericsson Power Modules, and Murata announced the founding of a new power industry consortium, the Architects of Modern Power (AMP Group). The goals of the Group go far beyond the ambitions or achievements of established trade associations in the power industry . The AMP Group will be characterized by deep collaboration between its member firms in developing leading-edge digital power technology , in terms of both functionality and efficiency. Common standards will encompass mechanical, electrical, communications, monitoring and control specifications. Members will focus on developing products that deliver high efficiency power conversion under all operating conditions and provide supply chain security to customers through true plug-and- play compatibility between their products.

Architects of Modern Power was founded to be a unique, long-term strategic consortium that will enable the power design community to benefit from world-class technology innovation and true plug-and-play product compatibility

Though still a relatively new entrant into the market, CUI has recognized that the key to unlocking digital power’s true value has required a very different way of thinking. Through collaboration with customers, vendors, and industry peers, barriers that have had the potential to limit adoption of the technology have been broken down. Moving forward, CUI will be a leader and a voice in the industry as the board- level power landscape continues to change.

CUI will be at the Applied Power Electronics Conference (APEC) in Charlotte, NC from March 15~19 demonstrating their latest digital products. In addition, Mark Adams will be speaking at 2 different industry sessions, Industry session #1: PMBus Considerations for Interoperability in a Complete Digital Power Ecosystem – as part of the PMBus Track and Industry session #2: Multi-Sourcing Standards for PoL and IBC Digital Power Supplies.


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