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Silanna Semiconductor Reference Design Supports Development of Industry’s Most Efficient All-Silicon 33W 1C Chargers


Active Clamp Flyback (ACF) design offers performance in excess of commercially available 30W GaN adapters

Silanna Semiconductor, The Power Density Leader, has launched a new active clamp flyback (ACF)-based reference design that simplifies and speeds the development of 33W 1C fast charger applications built using silicon power FETs. Featuring the company’s latest SZ1131 CO2 Smart Power™ ACF controller technology, the Silanna Semiconductor RD-23 provides a route to delivering performance that matches or exceeds that of commercially available 30W GaN-based chargers at a cost more readily associated with conventional silicon designs.

Silanna’s new RD-23 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. RD-23 uses the SZ1131 – Silanna Semiconductor’s newest ACF controller, which is rated for 65W for Universal input and above 100W with PFC-supported applications. This controller offers the industry’s highest level of integration by incorporating an adaptive digital PWM controller, ultra-high-voltage (UHV) active clamp FET, active clamp gate driver and startup regulator into a single compact device.

Providing an (uncased) power density of 22W/inch3, the RD-23 operates with a peak efficiency of over 92% and has a no-load power consumption (@ 230Vac) below 20mW. Efficiency is flat across the universal input (90 – 265Vac) input range and the reference design is fully production-ready as it exceeds conducted and radiated EMI requirements by more than 6dB margins.

“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,” comments Ahsan Zaman, Silanna Semiconductor’s director of product marketing. “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.”

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. Employing Silanna Semiconductor’s OptiModeTM digital control architecture, the SZ1131 adjusts the device’s 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.

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.

To further speed designs based on the RD-23 all PCB Gerber files and production files are available on request.

RD-23 Key Features

  • 33W USB-PD 1C High Power Density Reference Design
  • > 92% Peak Efficiency
  • < 20mW No Load Power Consumption, CO2 Smart Power by Silanna Semiconductor
  • 6dB Conducted and Radiated EMI Margins
  • Flat Efficiency Across Universal (90 – 265Vac) Input Voltage and Load
  • Uses Silanna Semiconductor’s Newest Fully Integrated ACF controller SZ1131
  • SZ1131 Integrates ACF Controller with UHV Active Clamp FET, Active Clamp Driver, and Start-up Regulator
  • Up to 146kHz Switching Frequency Operation
  • OptiMode™ Cycle-by-Cycle Adaptive Digital Control
  • Self-Tuning Valley Mode Switching (VMS)
  • Multi-Mode Operation (Burst Mode, QR, VMS)
  • OTP, OVP, OCP, OPP, and Output Short Circuit Protections


Information is available at https://powerdensity.com/reference-design or by contacting sales@silanna.com.

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