OSMIUM Technology Reaches Beyond USB-C

The last few times that I’ve talked to Pulsiv, the company has been highlighting its USB-C solutions - initially a reference design, and then as a full product. Due to that, it’s easy to forget that the company’s technology was developed to be used in a wide variety of power supply designs. In fact, Pulsiv’s CEO Darrel Kingham thinks that the technology is more relevant outside of the USB-C space, especially for higher power designs.

He expands, “USB-C was initially chosen as a showcase for OSMIUM technology because of the size of the market. We developed a full USB-C solution, with PCB layout, thermal and electrical characterization, EMC testing and safety approvals. The design was intended to demonstrate how capable the technology is, and the cube we created has better thermal performance than anything else in the market today. If that can be done in the crowded USB-C area, imagine what the technology could do in other areas, for example, LED drivers, industrial power supplies, data centres or EV charging? I'd argue that it will be even more valuable at higher power, as the losses there are more significant. But, USB-C was a great place to start, because the standard is very popular and well understood.”

Figure 1 - Pulisv's USB-C design features very low heat generation, allowing it to operate in small spaces without additional cooling

Pulsiv’s OSMIUM technology is based around the company’s OSMIUM microcontroller. Instead of using a boost inductor, a parallel capacitor is used as storage. The microcontroller precisely controls the charging of a storage capacitor, as well as the operation of other parts of the circuit. The technique removes the need for boost operation, and keeps line currents much lower, minimizing losses. A more in-depth explanation of how the technology works can be found in an earlier TechTalk blog here.

Kingham highlights OSMIUM ’s advantages by saying, “Power supplies usually work by taking the majority of the energy at the peak power of the grid. That high current brings greater I²R losses. OSMIUM uses current levels that are near 90% less than the peak current of a typical design, spreading the energy over the AC waveform, meaning that the losses drop off. It's a completely different way of thinking about AC/DC conversion that improves the whole system. It can be improved further by using GaN devices or other technologies, where you will get the benefit from the other technologies in addition to the uplift from OSMIUM .”

Along with a few other components, the microcontroller forms the front-end PFC part of the supply. Power can be scaled by changing an inductor, capacitor, resistor, and possibly the MOSFET. Those four key components form the basis of proven designs from 50W up to 350W, and demonstated it will scale to 650W, and possibly higher, in the future. The back-end DC/DC converter can be a number of configurations and topologies, depending on the application. These include industry standard DC/DC converter types including flybacks, forward converters, and asymmetric half bridge solutions. For a designer of PFC stages to use OSMIUM , the main change is the difference in the interface from traditional boost PFCs that use a 400V fixed voltage. The OSMIUM technology uses variable 160V and designers will need a second stage that is compatible.

In the case of flyback converters, OSMIUM technology has the potential to extend their usefulness to much higher power levels. Kingham explains, “One of our customers makes motors for hospital beds. They've designed a 350W flyback converter using our front end. OSMIUM technology gives engineers a new way of thinking about power supply designs, away from the traditional assumptions on when you make the transition from one topology to another. Flyback technology can now go much higher in power than than was previously assumed.”

The main advantage of OSMIUM is the increased efficiency through lower losses, and each OSMIUM design keeps a two-stage construction, even at power levels where other solutions would use a single stage. Kingham clarifies, “OSMIUM was originally about power factor correction. People asked why we’d use the technology in situations that no power factor correction was needed. Would it not just add losses? Our 65W USB-C design did not need power factor correction, but the stage still reduced overall losses. We compared the system to other commercial products and reference designs and we achieve better thermal performance and better efficiency with a two stage design than a single stage one. Our fundamental reduction in line currents has a knock on effect through the entire design. It cuts losses in the bridge rectifier, it cuts losses in the transformer and it stresses capacitors less.”

That reduced heat and stress on capacitors is important. Electrolytic capacitors are often the weak link in designs as they deteriorate over time, and heat can accelerate that process. It is estimated that for every 10°C rise in temperature, the expected lifetime of electric capacitors will be reduced by around 50%. The better operating conditions also allow solid polymer aluminium capacitors to be used to replace electrolytic capacitors, which was not not previously possible in universal input and high-line designs.

Another major benefit that OSMIUM provides is the lack of inrush current. This effect is most noticeable in large installations, for example in office buildings, hotels and other types of industrial and commercial premises. These buildings may have hundreds, or even thousands, of smaller power supplies. Kingham reckons that this is an area of concern that could emerge in the future, “I can see this become a growing problem in large installations, in situations after a power outage, when all the power comes back on at once and sequencing is currently used to avoid overloads. The lighting industry also face this situation as well with LED drivers. Typical their data sheets will recommend you only have four LEDs on a circuit due to inrush currents. At the moment, there are constraints and compromise that designers are making when it comes to system level, that could completely go away when using OSMIUM technology.”

https://www.pulsiv.com/