26 – 28 June 2019 Shanghai, China More Info

High Frequency Power Conversion

10:00 Tuesday, 26 June 2018
Chairperson: Prof. Dehong Xu, Zhejiang University, China

10:00 A Synchronous FET Class E Rectifier for >30 W Highly Resonant Wireless Power Receivers

Michael De Rooij, Efficient Power Conversion, USA

6.78 MHz resonant wireless power receivers based on the AirFuel standard have high rectifier losses when
using diodes and fail thermal limits for products such as laptops. This proposal uses a GaN FET in a class E
topology for a 30 W or higher receiver. Results show that a full bridge Schottky diode solution reaches a
temperature of 70°C with 83.4% system end to end efficiency when delivering 30 W, while the GaN FET
used in a class E rectifier reaches only 53°C and 86.1% efficiency.
10:25 Kilowatt Laser Driver with 120 A, sub-10 nanosecond pulses in < 3 cm2 using an GaN FET

John Glaser, Efficient Power Conversion, USA

Lidar time-of-flight distance measurement is the primary means of high-speed, accurate mapping of 3-D space. A primary application is for navigation and obstacle avoidance in real-time ADAS and autonomous vehicles. The laser transmitter is a key lidar subsystem and must generate optical pulses of duration less than 10 ns and high peak power. This work describes a laser driver using a single commercial GaN FET to achieve current pulses into a laser diode of >120 A peak for peak power of > 4 kW, with a duration < 10 ns. The driver area is < 3 cm2.
  Coffee Break
11:05 800V synchronous buck converter with series-connected GaN power transistors

Alexander Hensler, Siemens AG, Germany

Today’s GaN on Si semiconductor technology enables power transistors (HEMTs) with the maximum blocking voltage of 650V. However, for the majority of industrial converter applications 1200V blocking voltage of power transistors is desired. The approach to overcome this limited blocking capability is a series connection of two GaN devices. With this circuitry today’s well-known two level topology can be used without the need of a more complex and cost-intensive multilevel solution. For the feasibility study a 80A, 650V single GaN device was used.  With the realized synchronous configuration the switching behavior of proposed circuitry is demonstrated at 800V DC-link voltage; the switched current is up to 100A. Measurements are compared to the switching performance of a conventional 1200V Si-IGBT.
CCM Totem Pole PFC with Single-Shunt Peak Current Sensing and Indirect Differential AC Voltage Sensing

Wei Wu, Infineon Technologies America Corp., USA

This paper is about a design for low cost, high efficiency CCM totem pole PFC. It has single shunt resistor placed in negative DC bus. The current sensing circuit sense the inductor peak current, and use software to estimate average inductor current. Indirect differential AC voltage sensing method only uses ADC inputs and doesn’t require any op-amp or magnetic voltage sensor. Hardware cost is minimized which make totem pole PFC a good candidate for cost sensitive application to replace traditional boost PFC. A 1.5kW prototype is built and test result will be shown.