Abstract
The commercial mature gallium nitride high electron mobility transistors (GaN HEMT) technology has drawn much attention for its great potential in industrial power electronic applications. GaN HEMT is known for low on-state resistance, high withstand voltage, and high switching frequency. This paper presents comparative experimental evaluations of GaN HEMT and conventional Si insulated gate bipolar transistors (Si IGBTs) of similar power rating. The comparative study is carried out on both the element and converter level. Firstly, on the discrete element level, the steady and dynamic characteristics of GaN HEMT are compared with Si-IGBT, including forward and reverse conducting character, and switching time. Then, the elemental switching losses are analyzed based on measured data. Finally, on a complementary buck converter level, the overall efficiency and EMI-related common-mode currents are compared. For the tested conditions, it is found that the GaN HEMT switching loss is much less than for the same power class IGBT. However, it is worth noting that special attention should be paid to reverse conduction losses in the PWM dead time (or dead band) of complementary-modulated converter legs. When migrating from IGBT to GaN, choosing a dead-time and negative gate drive voltage in conventional IGBT manner can make GaN reverse conducting losses high. It is suggested to use 0 V turn-off gate voltage and minimize the GaN dead time in order to make full use of the GaN advantages.
Highlights
Power electronic devices convert huge amounts of energy in industrial applications, and provide the basis for upper layer control
MOSFETs and IGBTs differ in three main aspects: Firstly, the major difference is in conducting character
It can be seen that the turn-on loss increases more rapidly as the current increases, and the seen that the IGBT turn-on loss increases more rapidly as the current increases, and the GaN HEMT
Summary
Power electronic devices convert huge amounts of energy in industrial applications, and provide the basis for upper layer control. As a main difference from the conventional Si-based devices, the reverse conducting character of GaN HEMT does not require an additional diode and the reverse conduction voltage drop is largely related with the gate-drive voltage [16,17]. This reverse conduction is seldom discussed in detail in the literature. For complementary-modulated converter legs, the dead band must be set to avoid DC bus short circuits In this dead zone, if not properly configured, the GaN transistor voltage drop can be relatively large for dead band reverse conduction, inducing higher losses during this period.
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