­Silanna Semiconductor Takes ACF Integration to Next Level


Highly integrated ACF controller simplifies and speeds design of high-efficiency, high-power-density AC/DC power supplies and adapters.

Silanna Semiconductor

Highly integrated ACF controller simplifies and speeds design of high-efficiency, high-power-density AC/DC power supplies and adapters.


Silanna Semiconductor has expanded its CO2 Smart Power Family of AC/DC and DC/DC converter technologies.


The new active clamp flyback (ACF) controller integrates adaptive digital PWM control with ultra-high-voltage (UHV) components comprising a 700 V primary GaN FET, X capacitor (X-Cap) discharge circuit, active clamp driver and start-up regulator.


Silanna’s CO2 Smart Power technologies help engineers by simplifying design and improving performance while addressing environmental sustainability goals through more efficient energy use. Well-suited for high-efficiency and high-power-density power supplies, USB-PD/QC AC/DC power adapters and battery charging applications, the new SZ1200 integrated ACF controller combines the ease of design of a simple flyback controller with all the benefits of ACF. These include recycling of the leakage inductance energy of the flyback transformer and limiting primary FET drain voltage spikes during turn-off events.


Delivering above 93% efficiency at low line, the SZ1200 offers consistent efficiency across the universal input voltage range (90 - 265 Vac) and various loading conditions of up to 150W single-port and multi-port USB-PD applications. Silanna’s OptiMode™ digital control architecture adjusts operation mode on a cycle-by-cycle basis to maintain high efficiency, low EMI, fast dynamic load regulation and other key power supply parameters as line voltage and load vary. Very low no-load power consumption for the most stringent USB-PD applications further minimizes energy use during system stand-by.


“Our goal is to make it as easy as possible for power design engineers to develop ultra-efficiency, high-density power conversion designs in the shortest time possible,” says Ahsan Zaman, Silanna Semiconductor’s, Director of Product Marketing. “The addition of the SZ1200 to our family of ACF technologies supports this goal by offering high-speed switching, unprecedented levels of integration and functionality that ensures optimum efficiency across wide input and loading conditions while minimizing EMI.”


By allowing designers to program switching frequency to up to 250 kHz, the new controller supports high power densities while advanced digital active clamp operation ensures best-in-class efficiency. Switching frequency is confined within a tight frequency band to simplify EMI filtering. Further efficiency and EMI performance benefits are realized through adaptive digital control of the active clamp operation, which enables near ZVS turn-on of the primary FET and clamps the drain voltage during the turn-off.


SZ1200 also incorporates continuous conduction mode (CCM) operation, which allows delivering up to 225% rated output power for a limited duration without sacrificing the power density. This feature is targeted for applications requiring peak power, such as laptop and notebook power adapters.