Silanna Semiconductor expanded its line of fully integrated active clamp flyback (ACF) controllers with the 60W SZ1105 flyback PWM controller. Like its 30W SZ1101 sibling, Silanna’s SZ1105 60W controller combines four key ACF components: an advanced adaptive digital ACF controller and three ultra-high-voltage (UHV) components – an active clamp MOSFET, an active clamp FET driver, and a startup voltage regulator. This level of integration facilitates designing efficient, high-power-density AC/DC power adapters with low bill-of-material (BOM) cost. The 30W version is suited for designing mobile phone travel adapters, while the 60W version is suited for designing slim and compact adapters for powering notebooks, video game consoles and multi-port wall chargers.
High-power-density capabilities help designers overcome the thermal challenges of packing ever-increasing amounts of power into the small-form-factor power adapters that consumers have come to expect that also remain cool to the touch. High efficiency, or reducing power loss, is key to achieving the power density without overheating the adapter’s case. With an easy-to-use simple flyback controller and an all-silicon design, Silanna’s SZ1105 delivers over 93% efficiency at 20V/3A, and over 20W/in3 power density at full 60W output power, while using an industry-standard, avalanche-rated silicon MOSFET main switch.
SZ1105 combines design simplicity of traditional flyback with efficiency and power density of ACF: Silanna’s integrated circuit overcomes the traditional complexities of designing with ACF controllers. It eliminates the need for a tight tolerance for the clamp capacitor and leakage inductance. Instead, Silanna’s proprietary OptiMode adaptive digital control technology precisely manages the critical on/off the timing of the active clamp FET based on system operating conditions.
By replacing the traditional RCD snubber with a clamp capacitor and an integrated active clamp MOSFET, the SZ1105 delivers lossless recycling of leakage energy to the output. Precise control of the active clamp circuit delivers near-zero-voltage switching (ZVS) for further efficiency improvements. Additional features include optimal valley mode switching, tight switching frequency control, and intelligent switching frequency handling, all of which result in higher efficiency, a reduced main switch voltage rating, and appreciable attenuation of common-mode EMI noise.
The SZ1105 reduces BOM cost not only by integrating the ACF circuit but also by enabling designers to use a lower-cost transformer, SR FET, clamp capacitor and input filter.