Yasser Nour

Design and implementation of high frequency buck converter using multi-layer PCB inductor

Increasing the switching frequency for switch mode power supplies is one of methods to achieve smaller, lighter weight and cheaper power converters. This work investigates the opportunity of using two layer circular spiral inductors implemented in a 150 μm finished thickness printed circuit board for a high frequency DC-DC converter. The inductor was tested in a 5 W buck converter switching at 10 MHz. The converter achieved 84.7% peak efficiency converting 12 V to 5 V and 78% efficiency converting 24 V to 5 V.

Resonant full-bridge synchronous rectifier utilizing 15 V GaN transistors for wireless power transfer applications following AirFuel standard operating at 6.78 MHz

Connectivity in smart devices is increasingly realized by wireless connections. The remaining reason for using connectors at all is for charging the internal battery, for which wireless power transfer is an alternative. Two industry standards, AirFuel and Qi, exist to support compatibility between devices. This work is focusing on the AirFuel standard, as it is operating at a higher frequency (6.78 MHz), than the Qi standard, and therefore allows smaller passive components, including the coupling coils. Whereas gallium-nitride (GaN) devices are being widely used on the transmitter (Tx) side, this work uses low voltage GaN transistors on the receiver (Rx) side to allow synchronous rectification and soft switching, thereby achieving high efficiency. After analyzing adequate Class-DE rectifier topologies, a Class-DE full-bridge 5 W rectifier using 15 V GaN transistors are designed and implemented. The experimental results show an efficiency above 80 % over a wide operating range and a peak efficiency of 89 %, at an arbitrary alignment of Tx and Rx coils with 3 cm distance between them.

Module integrated GaN power stage for high switching frequency operation

An increased attention has been detected to develop smaller and lighter high voltage power converters in the range of 50 V to 400 V domains. The main applications for these converters are mainly focused for Power over Ethernet (PoE), LED lighting and ac adapters. Design for high power density is one of the targets for next generation power converters. This paper presents an 80 V input capable multi-chip module integration of enhancement mode gallium nitride (GaN) field effect transistors (FETs) based power stage. The module design is presented and validated through experimental results. The power stage is integrated on a high glass transition temperature 0.4 mm thick FR4 substrate configured as a 70 pin ball grid array package. The power stage is tested up to switching frequency of 12 MHz. The power stage achieved 88.5 % peak efficiency when configured as a soft switching buck converter operating at 7 MHz. The converter is tested up to 12 W of output power at 13 V ± 1.5 V output voltage. The converter achieved a volume power density of 20 W/cm3 and area power density of 9.4 W/cm2.