Active switching AC-DC controller uses silicon over GaN
Silanna has launched two active switched AC-DC controllers for consumer power adapter designs using silicon rather than gallium nitride (GaN).
The controllers are aimed at 33W and 65W designs, including USB-PD power delivery, with conversion efficiencies over 94 per cent. This approaches the conversion of GaN at lower cost, says Mark Drucker, chief executive of Silanna.
“We are delivering the advantages of GaN with silicon with a much lower bill of material (BoM) cost,” said Drucker. “There is no arguing from a switching efficiency GaN is a superior material – the question becomes at what price point is that valuable.”
The controllers use a system-in-package approach that allows new technologies to be easily adopted. “We are technology agnostic,” said Drucker. “We’ve worked with GaN and will absolutely move to a more efficient switch technology if and when the economics work so I think you will see offering coming from us in the next few quarters.”
“There are two types of GaN solution in the market,” he said. “The first is integrated from a standard AC-DC 60kHz flyback design. Then there is the 300kHz switchd design and there the pricing there is enormous – it’s a huge premium, and we are matching their efficiency and density at a 35 per cent lower BoM cost.”
“What we focus on is a control system that extracts the maximum efficiency regardless of the technology,” he said. The digital controller optimises performance cycle by cycle as the component values change throughout manufacturing, die temperature and external temperature, line voltage, switch voltage, output voltage and load. Using this data, the switching frequency and mode is adjusted, again cycle by cycle.
The SZ1110 (33W) and SZ1130 (65W) devices integrate the adaptive digital PWM controller, an active clamp FET, gate driver and startup regulator, all in the same package. This allows designs with 27 W/in3 power density at 65W, and also allows the silicon superfunction FET to be replaced with a GaN FET.
“The adaptive digital control is key as well as how we operate the active clamp and we give the system designer all of that benefit while making the design process as easy as a standard flyback controller,” said Drucker.
Sampling to lead customers and broad sampling in the next month and qualified for volume in June.
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