Front end AC-DC architecture slashes size

Technology News |
By Nick Flaherty

Cambridge start-up Pulsiv has launched an AC-DC power conversion technology that can reduce the  size of converters and scale from USB-C chargers up to electric vehicles.

It has developed reference designs for its AC-DC converter technology, which it calls Osmium. This uses a small storage capacitor to avoid the need for an inductor in a power factor correction circuit for higher power converters.

This is controlled by specialist algorithms developed by Pulsiv and implemented in industry standard microcontrollers, which Pulsiv sells as the PSV-AD-150 and PSV-AD-250. The company would no comment on which microcontroller they use.

The technology is built on research by Dr Zaki Ahmed at the University of Plymouth. “The problem that I was working on was extracting more energy out of solar panels using clever algorithms. There were a lot of the things I couldn’t do with DC-DC converters so I went back and designed a system from scratch,” said Ahmed, who is chief strategy officer and based at the R&D hub in Plymouth.

“We move away from the traditional boost regulator with a resonant converter. We have a universal input for PFC without a switched inductor and a small storage capacitor that stores enough energy to ride through when the line is at low voltage,” he said. “The microcontroller regulates the charging current into the capacitor to maximise the power factor.”

While PFC is usually used above 65W, the smaller size of the Osmium design from the smaller 160 V or 200V capacitors can be used in lower power designs as well. Using gallium nitride (GaN) transistors rather than silicon can further reduce the size.

“There are people that need power factor below 65W such a lighting and the 150W design is more efficient than a 30W design for the vampire [low load] power consumption as we have a flat efficiency profile,” said Darrel Kingham, CEO.  “People are re-thinking power supplies at the moment.”

“As we started testing we realised we have a unique efficiency profile,” he said. “Down to 2W we are still over 80% efficient and then it’s the passives that become significant and the dominant power loss mechanism.

The design is intended to work with different DC-DC converters as companies all have their own designs. “Customers have their favoured DC-DC converter with favoured pricing and everyone does it differently,” he said.

The architecture also provides a single design for laptop power supplies that need different controllers to meet various standards.

Pulsiv has demonstrated a universal input, single switch 180W flyback power supply design that delivers 97.5% average (99.5% peak) front-end efficiency while maintaining 90% at just 2W.

A 350W interleaved flyback is currently being developed and work is underway to showcase reference designs with higher power capability.

The algorithm in the microcontrollers ensure that critical components operate at lower temperatures to extend their expected operating life, even under convection cooling.

Regulating the flow of mains through the charging capacitor eliminates the inrush current, so manufacturers of SMPS and LED lighting products can simplify designs and reduce the cost of system installation.

The technology supports Active Bridge Control, Configurable Hold-Up, X-Cap Discharge, HVDC Output Selection, a Power Consumption Indicator and Grid Failure Detection. These optional features can be used as required to meet the needs of different end applications.

Pulsiv is also looking at scaling the architecture to high power applications such as electric vehicle (EV) charging.

“For higher power levels what we are seeing is we can meet regulatory requirements while upgrading the charging path,” said Kingham. “The capacitor will still be 160V or 200V. If you want more energy stored it’s the current rating of the inductor and the MOSFET that needs to increase but you can still use a silicon MOSFET at much higher power levels.”

Pulsiv is selling the controller through distributors Astute and Digi-key.

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