The demand for more functionality and improved performance in electronic products continues to expand, driven by a variety of factors such as a desire to reduce energy costs to the need to optimise performance for efficiency, reliability, and safety. The ability of an electronic product of any type to address performance and functionality begins with its power supply, as every aspect of a circuit is based upon how effectively it can manage energy.

There have been many solutions presented to increase power efficiency in a circuit. These range from materials advances like wide-bandgap semiconductors to software advances in digital power management. There have been great strides made in advancing efficiency in modern electronics, but there is still more that can be done. The goal is to have a high level of efficiency across the power supply’s full load and input voltage range. This is especially important at low power levels, in situations like trickle-charging a laptop, smartphone, or portable device, for example.

A new power electronics technology has been unveiled from a company called Pulsiv, a Cambridge-based start-up who recently emerged from stealth mode.

Pulsiv’s OSMIUM technology uses a patented method to convert AC to DC involving the charging and discharging of a small storage capacitor, without the need for a PFC inductor. Offering an ultra-compact system design, this technology enables a high-power factor with consistently high levels of efficiency, and can be used to improve system performance, optimise cost, and reduce overall energy consumption.

This power conversion methodology came from efforts by a Plymouth University research team in collaboration with the solar industry. They were working on ways to increase the power output from solar panel arrays by minimising system losses, especially in the conversion and control circuitry. The team discovered they couldn’t use standard DC/DC or DC/AC solutions and run the algorithms they wanted, so they developed new power circuits from scratch.

This breakthrough not only has applications in DC to AC inverters, but also in AC to DC conversion.

Pulsiv was founded in 2013 and spun-out from the University of Plymouth in the UK to commercialise the new conversion technology to improve power efficiency in electronics. This technology benefits both wall-tethered and battery-powered applications, in addition to the initial intent to enable more energy to be extracted from solar panels. In September 2022, Pulsiv launched a solution based on their new OSMIUM microcontroller and patented switching techniques.

Figure 1: Pulsiv’s AC to DC solution using an intelligent controller and patented switching technique.

Power Factor Correction (PFC) is achieved without a switched inductor, and just needs a small storage capacitor to be charged and discharged with switches S¹ and S², as shown in Figure 1. The advantages of this topology stem from the use of capacitors as the switching element, rather than inductors, to significantly reduce losses. That way instead of using the traditional method using a boost PFC with an inductor in series, Pulsiv’s approach uses a capacitor in parallel.

This enables the charging path to be regulated, with a separate discharge path from the capacitor. The algorithms that run on the OSMIUM microcontroller optimise PFC by regulating the current used to charge the capacitor, with the discharge side controlled precisely by the follow-on DC/DC converter. The capacitor stores the energy needed to “ride through” when the grid is weak. By intelligently controlling the charging path, very high-power factors are possible, able to meet any line-current regulations required.

Using OSMIUM technology

To underscore the advantages of OSMIUM technology, let’s compare it to a legacy solution such as a low-line, wide-input LLC resonant converter, used in a 12V at 10A consumer electronics application. Above 20W, and certainly above 40W, the performance is in the high 80% to low 90% range. However, below 20W, performance tends to fall off dramatically, so badly that when drawing under 10W, the efficiency falls to around 50%. This disappointing efficiency profile is typical of consumer products using a legacy LLC solution.

This reference design example operates from a low-line supply (100Vac to 132Vac) using a single LLC resonant converter stage and offers a claimed efficiency of 87% at full load.

OSMIUM technology can be leveraged with standard DC-DC converters to displace higher-cost LLC solutions and the OSMIUM microcontrollers such as the PSV-AD-xxx family (PSV-AD-250 sampling now) can be used as a platform for any application requiring from 1W to 10kW, simply by adjusting just three system components and the use of a suitable DC/DC converter. The company recently demonstrated a universal input, single-switch 150W flyback design delivering a 97.5% average front-end efficiency, with a 99.5% peak, while operating at 90% with loads as low as 2W.

Figure 2: Basic schematic and operation of an OSMIUM-driven power solution.

Figure 2 shows the basic operating principle, with Path 3 showing the charging of the storage capacitor, with the maximum capacitor voltage regulated by pin 4 at 150V or 180V. The grid-sense on pins 5 and 6 determines the grid voltage & frequency. Path 4 follows the discharging of the storage capacitor. Cch is discharged via Dd; the discharge current will depend on the follow-on DC/DC converter. Importantly, the regulated charging path to Cch means that there is no inrush current, crucial in many applications. This also means you can eliminate any kind of inrush filtering, another huge advantage of the technology.

Figure 3: Pulsiv’s front-end performance curves vs EnergyStar requirements.

Figure 3 shows the efficacy of the Pulsiv solution, with the plots for voltage inputs 90V (purple), 115V (green) and 230V (blue), enabled by the OSMIUM MCU with active bridge and flyback topology. Note that even down to a load as low as around 2W, the power supply’s efficiency remains between 80% and 90%, depending on the input voltage. Then from around 5W until maximum load, the efficiency is solidly in the mid 90% range. Various EnergyStar standards are also plotted for comparison, showing how an OSMIUM solution easily meets even the most stringent Energy Star VI requirements. SiC, GaN and other technologies can be used to further improve performance, but the default circuit configurations use silicon FETs optimised for cost.

Figure 4: Salom’s 150 flyback platform using the OSMIUM MCU achieves an ‘astonishing flat efficiency profile with no inrush current at both hi and low-line input voltage’.

High efficiency power conversion naturally benefits thermal management. The critical components in a Pulsiv OSMIUM circuit operate at low temperatures to extend their expected operating life, enabling methods such as convection cooling.

Since the solution regulates the flow of power through a charging capacitor, there is no inrush current, so creators and manufacturers of products such as industrial power supplies and LED lighting drivers can simplify their circuit designs, reducing both the bill or materials as well as the cost of system installation.

In addition, Pulsiv OSMIUM technology also supports advanced optional functionalities like Active Bridge Control, Configurable Hold-Up, X-Cap Discharge, and HVDC Output Selection, as well as Power Consumption Indication and Grid Failure Detection.

A Front-End Solution

Pulsiv OSMIUM microcontrollers are combined with supporting components to produce a complete front-end AC/DC solution. These can be optimised for performance, size, or cost depending upon the overall system requirements. For example, leading consumer electronics PSU maker Salom is already using OSMIUM MCUs in their new 150W PSU flyback platform. The overall performance of the new PSU runs at 91.5% from a 10% load to a 100% load and can be compared to other flyback designs employed by Salom by looking at the orange line, which shows a still-impressive mid-80% efficiency, but it falls off sharply below 30% loading. Their more complex and expensive LLC PSU solution is shown in yellow, and also falls off from 40% load.

According to Salom’s Andy Richardson, Vice President of Business Development, “The Pulsiv technology delivers an astonishing flat efficiency profile with no inrush current at both hi and low-line input voltage. A single PSU can now be used to support multiple applications – previously an optimised PSU was required for each.”

Looking forward

The demand for powerful, reliable, and efficient power supplies will only continue to increase as both electronic products and the infrastructures to support them continue to expand into more and more application spaces. Using advanced power topologies and methodologies like Pulsiv’s OSMIUM technology can go a long way to address these high-efficiency power demands.