While existing silicon designs have improved steadily in efficiency and density, there’s a limit to what can be achieved with this technology. This is where gallium nitride (GaN) devices are being increasingly employed to meet the challenging requirements of the data centre market with respect to density and efficiency.
Over recent years, there’s been a shift towards computing being handled in the cloud, which has led to an unprecedented growth of hyper scale datacentres with ever more power to be handled per rack. In turn, this has meant power demands have increased with the focus being laid upon more efficient, compact power supplies that use less electricity. Heat dissipation is the other essentially element here, with the aim to minimize the cooling demands as far as possible. With power demands for each rack rocketing up to 20kW and higher, there has been a trend away from the conventional 12V power rails to using 48V, thus reducing losses. However, more improvements are needed.
GaN devices have a number of electrical characteristics that give them advantages over silicon. Firstly, GaN high-electron-mobility transistors (HEMTs) have an order of magnitude lower gate charge and output charge, as well as virtually zero reverse recovery charge. Together, this means that hard commutation of reverse conducting devices is possible, thus enabling the use of simpler topologies such as totem pole PFC stages with trapezoidal current modulation.
By reducing switching losses and allowing higher switching frequencies, GaN devices can deliver higher efficiency than silicon alternatives in many applications, as well as higher power densities. On the downside, GaN switching devices are more expensive than silicon alternatives, and may increase the overall power supply cost.