Improving Efficiency in Downhole Power Converters using GaN Technology

Abstract

Abstract In downhole applications, the ability to convert wildly varying wireline voltages standard +/− 15 VDC stretches the limit on switching converters whose components have to be rugged, compact, and offer low thermal paths to surrounding metal housings. Many times the incoming voltages exceed 200V with spikes above 500 quite common. Functioning in extreme environments up to 200 degrees Celsius requires the designer to squeeze out the highest power efficiency possible and every percent increase is an important milestone. Over the past three decades silicon devices were the only technology available that could be made to work at such temperatures, almost always bypassing the manufacturer's maximum specifications. In the past several years wide bandgap semiconductors have become available that offer new possibilities for operation at elevated temperatures. This paper discusses the efficiency improvements when silicon power devices are replaced with gallium nitride based components. By utilizing GaN High Electron Mobility Transistors (HEMTs) in an existing H bridge phase shifted converter, efficiency improvements of up to 9% have been achieved at 175 °C operation. Advantages of HEMT devices compared to silicon are discussed and associated loss mechanisms of both are compared.