Solutions suitable for high-performance power supply units
Efficiency and simple thermal management with minimal additional parts

ON Semiconductor has introduced a new Synchronous Rectifier (SR) controller optimized for LLC resonant converter topologies. The new FAN6248 provides high efficiency with minimal additional components, simplifies thermal management, and enhances overall system reliability. Furthermore, it simplifies the design of LLC power supplies.

The FAN6248 is an ideal solution for modern, high-performance power supply units (PSUs) requiring high levels of reliability and efficiency in small spaces. Common applications include servers and desktop computers, gaming, large-screen LCD and OLED TVs, networking, communications, and LED lighting.

This device incorporates a modern hybrid SR control method that detects the immediate drain voltage along with information from the previous switching cycle. Through a separate 100V rated sense input function, it accurately determines the drain and source voltages through two SR MOSFETs while allowing for asymmetric or poor coupling in the secondary winding.

The FAN6248, along with just two external resistors and a MOSFET, delivers a simple LLC converter supporting up to 800W. The addition of two capacitors enhances system safety, particularly in noisy environments. This product also operates very reliably and efficiently over a wide power range. It is possible to operate beyond resonance without adopting voltage spikes.

The FAN6248 enters green mode under no-load conditions and stops operating automatically. The controller generates pulses in green mode that provide highly efficient power delivery required by efficiency standard regulations such as 80 PLUS®, DoE VI, and CoC Tier 2 under low load conditions.

The adjustable built-in parasitic inductance compensation feature also improves PSU efficiency by minimizing body diode conduction in SR MOSFETs due to stray inductance in the package. With this series available in four devices, power supply designers can select the one best suited for their application based on switching frequency (25 kHz–70 kHz or 60 kHz–700 kHz) and MOSFET-related stray inductance levels.

These products are suitable for use with MOSFETs mounted in TO-220, D2PAK, DPAK, or PQFN package styles. In addition, the FAN6248's 10.5V high gate drive output ensures the ability to drive a very wide range of MOSFETs.

Shane Chilton, General Manager of Power Conversion Solutions at ON Semiconductor, said, “The FAN6248 comprehensively addresses the needs of modern LLC PSU designers.” “Innovative technologies such as mixed control methods and adjustable parasitic inductance compensation ensure stable and high-efficiency operation,” he added. “This controller, which requires only two resistors and MOSFETs to implement the advanced LLC converter, will be popular among all engineers requiring high-performance designs.”