Silicon 33W charger reference design tops 92 percent efficiency

Silicon 33W charger reference design tops 92 percent efficiency

Technology News |
By Nick Flaherty

Silanna Semiconductor has launched an active clamp flyback (ACF)-based reference design that simplifies and speeds the development of 33W 1C fast charger applications built using silicon power FETs.

The RD-23 design uses the SZ1131 ACF controller 65W technology and matches or exceeds that of commercially available 30W GaN-based chargers at a cost more readily associated with conventional silicon designs.

The reference design incorporates everything an engineer needs to prototype and develop a fully functional charger with low operational and no-load/ stand-by power consumption and minimum component count, BOM cost and size. The  SZ1131 is rated for 65W for Universal input and above 100W with PFC-supported applications and integrates an adaptive digital PWM controller, ultra-high-voltage (UHV) active clamp FET, active clamp gate driver and startup regulator into a single compact device.

The uncased power density of the design is 22W/in3 and it operates with a peak efficiency of over 92 percent and has a no-load power consumption (@ 230Vac) below 20mW, a key requirement. Efficiency is flat across the universal input (90 – 265Vac) input range and the reference design with all Gerber and production files is fully production-ready as it exceeds conducted and radiated EMI requirements by more than 6dB margins.

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The SZ1131 operates at frequencies of up to 146kHz and provides the ease-of-design of a simple flyback controller with all the benefits of an ACF design. This includes recycling the leakage inductance energy of the flyback transformer and limiting the primary FET drain voltage spike during turn-off events. Silanna’s OptiMode digital control architecture is used to adjust the mode of operation on a cycle-by-cycle basis to maintain high efficiency, low EMI, fast dynamic load regulation, and other key power supply parameters in response to varying line voltage and load.

“The RD-23 is the latest in a series of silicon- and GaN-based reference designs that Silanna has created to help engineers quickly and easily develop the industry’s most efficient and highest power density chargers,” said Ahsan Zaman, director of product marketing at Silanna. “In our benchmarking tests the RD-23 met and exceeded both the efficiency and no-load vampire power consumption of the best-in-class commercially available GaN-based power adapters. RD-23 demonstrates GaN-level performance at silicon-level costs.”     

Supplied in a 16-pin SOIC package, the SZ1131 offers protection against over-temperature, over-voltage, over-current, over-power and short circuit conditions, as well as transformer core saturation fault without the need for additional external components.

Details of the design are at

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