Silicon AC-DC charger reference design extends to 65W

Technology News |
By Nick Flaherty

Silanna Semiconductor has developed a 65W charger reference design around its all silicon active clamp flyback controller.

The RD-31 refence design challenges the performance of many commercially available 65W GaN-based chargers at a cost more readily associated with conventional silicon designs, says Silanna.

The RD-31 is the latest in a family of production-ready reference designs that provide everything needed 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. This family includes all-silicon 33W and GaN-based 65W USB-PD reference designs.

The reference designs are all based on Silanna’s SZ1131 ACF controller, which is rated for 65W for universal input and above 100W for power factor correction (PFC) applications. The chip incorporates 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 RD31 reference design is 30W/inch3 with a peak efficiency of around 94% and a no-load power consumption below 25mW. Efficiency is flat across the universal input voltage range (90 – 265Vac) and the reference design is fully production-ready as it exceeds conducted and radiated EMI requirements by more than 6dB. In benchmarking tests the RD-31 exceeded the efficiency of the best-in-class commercially available GaN-based power adapter by 0.5% and reduced no-load vampire power by as much as 44%.

“We are committed to helping engineers deliver high-performance chargers with ever higher power densities by developing technologies that increase operational efficiency and reduce vampire power,” said Ahsan Zaman, Silanna Semiconductor’s director of product marketing. “By building production-ready reference designs around these technologies we are also simplifying the design-to-manufacturing cycle to ensure these advanced charger designs move to production in the shortest possible time.”

The SZ1131 operates at frequencies 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 allows the SZ1131 to adjust 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 conditions.

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

All PCB Gerber files and production files for the 65W RD31 reference design are available on request.

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