65W reference design for in socket USB-C PD power
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Pulsiv in the UK has launched a modular 65W USB-C reference design for in-socket chargers and is planning a 240W version.
The 65W USB-C PD reference design is designed by Pulsiv to have high efficiency and smaller size than that for external adapters with low thermal requirements so that it can be integrated into sockets by OEMs.
“We have taken the AC-DC front end of the power supply and pulled it into an end to end system,” said Tim Moore, Chief Product Officer of Pulsiv tells eeNews Europe. “What we really wanted to do with the design was prove the technology works and learn from this.”
The design uses the ‘valley fill’ control algorithms developed by Pulsiv, implemented in Osmium, a commercial secure microcontroller. The valley fill algorithm allows a half active bridge that can be difficult to implement at low current but helps boost the efficiency to 95% with a peak of 96%.
Cost optimised power supply reference designs cut energy waste
The transformer and inductor are designed and produced by Frenetic in Spain. This allows the design to fit into a power socket with a depth of 25mm, allowing retrofitting where efficiency and heat is a key issue.
“In terms of size we are using an EQ20 transformer rather than RM8 or RM10 and between that and the output cap those are the largest things on the board,” said Moore.
The design also uses gallium nitride transistors from Innoscience switching at 125kHz, although devices from other suppliers can be used. “GaN has been interesting and a pain in the neck for this design but we have optimised it for GaN,” said Moore. “Out of all the companies we work with, we found Innoscience to be really responsive with devices with low RDSon and fast switching.”
The chosen GaN parts are not part of the ongoing patent disputes between Innoscience and Infineon in Europe and EPC in the US. “You can use similar GaN products and we have tested our boards with other devices from Nexperia just in case,” he said
The design has been tested in a calorimeter and shows a maximum transformer temperature of 39.5 C above ambient. This avoids the risk of electrolytic capacitors drying out over time, enhancing the reliability.
The 65W reference design is modular so that different parts can be adopted or changed, including the USB PD3.0 controller. “We’ve used Innotek for the USB-C controller but there are plenty of others available,” he said. “That’s why we pull out the different elements of the design.”
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