Stories of Manufacturing#07
The future of power supply design shaped
by the hybrid of analog
and digital technologiesLogiCoA™ Power Supply Solution
Power supply technology is on the verge of change
After studying electrical and electronic engineering, he joined ROHM over 30 years ago.
Mr. Yokomizo, who currently works as a Field Application Engineer (FAE), has been involved in LSI product development since joining the company.
Stereo headphones, mobile phones, USB interfaces, e-books...
His journey, centered on consumer electronics, closely mirrors the path taken by Japan's electronics industry as a whole.
FAE Division 1
System Solutions Engineering Headquarters Manager
Ichiro Yokomizo
We always want to sell what we make. In other words, make things that sell.
With this in mind, he has been involved in a variety of products up to now.
His enthusiasm for this project was also considerable.
This industry has energized the market with technologies and products suited to the times, continuously creating new needs.
Having witnessed the industry's every move, Mr. Yokomizo is now focusing his efforts on bringing new power supply solutions to the market, mainly targeting industrial equipment.
At the core is the LogiCoA™ brand.
This technology is designed to contribute to improving power efficiency, which is a major social issue, by offering solutions that can be applied to an extremely wide range of applications in the power electronics field.
Initially focusing on power supplies essential for a variety of electrical devices, ROHM has advanced its long-standing expertise in analog control power technology to an entirely new level.
The key to this breakthrough was the ‘hybrid of digital elements’ with the goal of maximizing the performance of analog circuits.
Market Background Surrounding Digital Power Supplies
Features and Challenges of Analog and Digital Power Control Circuits
As can be seen from the comparison table above, analog control, predominantly used in the low to medium range from 50W to 1kW, struggles to achieve advanced functionality, while digital control typically employed in high-power applications encounters issues related to high costs and considerable power consumption.
Low to medium power supplies, which make up roughly 70% of the market, are expected to see a steadily increasing demand, particularly in industrial equipment, as illustrated in the graph below.
Applications include power supply units for industrial robots, factory automation, PCs, and servers, but as previously mentioned, the majority of these currently rely on analog control. LogiCoA™ is primarily targeting this market segment.
Market Size Forecast for Power Systems in the Low to Medium Power Range for Industrial Equipment (approx. 50W to 1kW)
Barriers of Power Consumption and Cost
Yokomizo
: ‘The reason why the adoption of digital power supply control is not progressing quickly is quite clear. It simply comes down to power consumption and cost.
Both of these factors can increase by about 10 times compared to analog control.’
In digital control power supplies, output voltage information is fed directly into the MCU, where the CPU/DSP continuously operates at high speed to perform feedback control.
This requires a highly sophisticated MCU, leading to increased power consumption.
Overcoming this barrier is a major challenge for engineers involved in power supplies and, by extension, the entire field of power electronics.
In switching power supplies, an MCU monitors output voltage and controls power devices to maintain a constant output voltage.
Issues Facing Analog Power Supply Circuits
Another long-standing challenge faced by engineers working with analog power ICs is the variation in component characteristics. Differences in the properties of key components in power topologies, such as power devices, gate drivers, resistors, inductors, and regulators, can contribute to the overall variability of analog circuits.
A typical solution is to implement a ‘design margin’, which in analog control circuits often means allowing for extra rated current.
Industrial Consumer Power & Motor FAE Department
FAE1 Division
System Solutions Engineering Headquarters Engineer
Kenji Funatani
I am always mindful of the saying, ‘People often miss opportunities more than opportunities miss people.’
Perhaps the key to breakthroughs lies in persistence and a continuous thirst for knowledge and exploration.
Funatani
: ‘A straightforward method is to increase the size and breakdown voltage of components or incorporate variation correction circuits such as trimming, but these approaches inevitably lead to larger footprint and higher costs.
Conversely, if such measures are not taken, the accuracy and performance will be compromised.’
The function that solves this problem using digital technology is ‘calibration.*’
* A function that allows the MCU to store data to compensate for variations in individual circuits and mounted parts at the time of shipment, ensuring that various protection functions operate at appropriate values
Funatani
: ‘Calibration enables component optimization by eliminating unnecessary margins, allowing for designs with smaller sizes and lower ratings.
For example, large transformers and inductors in the analog blocks of power supplies fall under this category, so eliminating the design margins for these components alone would have a substantial impact.
Example of reducing inductor size through the calibration function
Our goal is to maximize product performance by fully unlocking the potential of each device and the power circuit itself without being constrained with design margins.
This dilemma, shared by many engineers, has gradually evolved into a driving force for a new approach: ‘integrating digital elements’ to ‘maximize the performance of analog circuits.’
Towards the Hybrid of Digital and Analog
Yokomizo
: ‘The first prerequisite is that power consumption and cost must be on par with analog systems while benefiting from the advanced functionality of digital technology.
Simply put, the goal of the LogiCoA™ power solution is to create an analog-digital circuit design that combines the best of both worlds. This is its core feature and guiding concept.’
‘Even if I weren't in this role, I would still be involved in developing electrical appliances that I would use myself,’ he says.
Maybe I’m an electronic sapien at heart.
This seemingly paradoxical project was initiated at ROHM in the latter half of 2020. A select group of engineers from within and outside the company was assembled to address the challenge of effectively combining the advantages of both analog and digital technologies.
Despite the overall slowdown of society due to the COVID-19 pandemic, development proceeded at a rapid pace.
Industrial Consumer Power & Motor FAE Department
FAE1 Division
System Solutions Engineering Headquarters Engineer
Ryo Kato
The expression on his face as he quietly performs the experimental work reflects a deep sense of pride and responsibility, stemming from his involvement in this project since its inception.
It’s also refreshing to see another side of him, passionately cheering for his favorite soccer team in his hometown of Yokohama on the weekends.
Kato
: ‘The first major decision we made was to take a decisive approach by using analog feedback control. This eliminates the need for a high-spec MCU, significantly reducing power consumption and cost.’
‘In the digital section, development and design focused on improving power supply performance, including ① Power supply status monitoring, ② Optimizing the timing control of switching elements, and ③ Calibration. At this point, we had already formed a certain expectation that we could optimize and customize inexpensive general-purpose MCUs.
MCU x Switching Power Supply
The solution hinged on developing circuits and programs that could mutually complement the general-purpose MCU and analog circuitry. Signals are generated to control power devices based on the output voltage received through the analog compensator.
This crucial function is carried out by ROHM's LogiCoA™ power supply control MCU that integrates proprietary new technology.
The core of the LogiCoA™ solution fully showcases the technologies and expertise of LAPIS Technology, acquired by ROHM in April 2024.
Event-driven control is included that manages the subsequent signals based on dynamically changing signals. Another important feature is the ability to simultaneous control two topologies.
At the beginning of the project, however, we faced numerous setbacks and moments of confusion, as analog power supplies and MCUs, despite both being part of the semiconductor industry, represent two distinctly different fields.
Inuzuka
: ‘I had never been involved in the design of a power supply itself, so when I first heard about it I thought, ‘Power supply control with an MCU???’ with question marks popping up in my head.
Although I’ve been part of the project from the beginning, my knowledge of power supplies was limited, so I didn't know how the circuits I was developing would be used. I also wasn’t sure how well this MCU would resonate with customers. I couldn’t envision it at all.’
MCU Product Development Division,
LAPIS LSI Segment, LSI Business Headquarters Deputy Chief Engineer
Kotaro Inuzuka
He is eager to leverage his experience working various roles in MCU development during his time at Oki Electric and LAPIS Semiconductor for the benefit of ROHM MCUs.
As development progressed, several issues within the power supply industry emerged. These included margin design and power efficiency, support for multi-functionality such as logging and communications, system reuse/serialization, and customization.
By systematically addressing these challenges through hybrid with digital technology and realizing that the outcome could be widely offered to customers as reference designs, all doubts disappeared.
Inuzuka
: ‘The most memorable moment was when a customer said, ‘This is going to change the world of power supplies!’ My motivation instantly soared.’
Provided as a Reference Design
Let's take a moment to review the overall picture of the LogiCoA™ solution, which was released in April 2024.
●At the core of the solution, as previously mentioned, is the LogiCoA™ power control MCU
●A power supply topology that integrates everything from power devices to analog compensators into a cohesive circuit
●A newly developed power supply control OS <RMOS> that significantly reduces user design workload
A key feature is that we offer these three optimized components as a reference design.
To significantly reduce the design workload for power supply and set manufacturers, we’ve also started offering onboard simulation environments and reference boards tailored to various power topologies.
The benefits of adopting this solution are so considerable and diverse that they cannot be fully detailed here. For more information, please visit our dedicated page.
Related Link(s)
Dedicated LogiCoA™ Solution Site
(*Coming soon)
Who Benefits from the Evolution of Power Supplies?
Sebata
: ‘For customers, one of the biggest advantages of digital technology is the ability to record operational log data.
By continuously monitoring the circuit’s status externally, we hope to provide proposals that encompass the operation of the power supply itself.’
MCU Product Development Division,
LAPIS LSI Business Unit, LSI Business Headquarters
Kohei Sebata
A promising engineer and one of the youngest members of the project, he has made outstanding contributions in multiple areas. He finds joy in the daily process of creating semiconductors, using that passion as motivation for his work.
One example of the specific benefits of introducing digital technology was shared by Mr. Sebata, an engineer engaged in development on the microcontroller/OS side. Through his close involvement with power supply systems, he became aware of the overwhelming design burden faced daily by power supply manufacturers and set manufacturers.
Sebata
: ‘When specifications differ for each product, customers often need to modify the configuration and constants of the control unit and peripheral circuits.
Each time a series or custom product is developed for a specific customer, components and circuits must be changed individually. I believe one of the major advantages of MCUs is the ability to dramatically reduce these design burdens.
▶ Parameter settings make it possible to adjust specifications such as output voltage, startup/shutdown voltage, and overcurrent protection
▶ Software changes allow for additional controls
Introducing MCUs that provide thorough support for development and design will undoubtedly bring about major changes in power supply design itself.
Sebata
: ‘For many power supply designers, the downside of ‘having to start by writing source code for the MCU’ is often a concern, but with the newly developed OS for power control, design has become remarkably straightforward.
We hope to accelerate the customer development process.’
Leveraging ROHM's Strengths in the Market
Yokomizo
: ‘ROHM offers a wide range of products, from discretes to ICs, but after decades of competing in the power supply industry, I honestly felt that we lacked strength in the area of controllers/MCUs that control the power circuits themselves.’
As an FAE who frequently collaborates with customers, he noticed a rising demand for ‘comprehensive power solutions’ that take into account not only the capabilities of individual products, but also the overall operation of the circuit itself.
He embodies a sense of ‘strength and simplicity’ with a dignified and calm demeanor.
‘I spend my weekends playing with my dog,’ he says with a warm smile.
Yokomizo
: ‘By expanding the LogiCoA™ solution we’ve developed, ROHM's strengths in discrete products and analog ICs will prove to be even more useful.
We believe we can leverage our strengths to propose solutions across a wide range of applications.’
Our main objective is to achieve the ambitious task of replacing all power supplies in the low to medium power range which has traditionally been dominated by analog technology, with LogiCoA™ solutions.
Ambitions shouldn't be a privilege reserved for the young.
Embracing the spirit of ‘monozukuri’ (manufacturing) where every engineer dreams of their own ambitions is what will drive the world of tomorrow.
Yokomizo
: ‘Digital power control, which gained prominence in the 1990s, has become widespread in fields that handle large amounts of power. However, analog control remains the standard for low to medium power supply devices that constitute the majority of electrical equipment in the market. Although power supply and set manufacturers recognize the benefits of digital power supplies, including enhanced functionality, user-friendliness, and scalability, when considering practical factors such as costs, the prevailing sentiment seems to be: 'Isn't analog still sufficient?’