Three-level driving method for GaN transistor with improved efficiency and reliability within whole load range

Compared with Si MOSFET, gallium nitride (GaN) power transistor has higher reverse conduction voltage drop due to the absence of body-diode, which will result in higher reverse conduction loss. Furthermore, the oscillation on the driving voltage is quite severe when the GaN transistor operates in high frequency condition, which is critical for GaN transistor because of its relatively narrow driving voltage range. To guarantee GaN transistor operating reliably, driving voltage can't be set high enough to have lower conduction resistance, thus reducing the forward conduction loss. The existed three-level driving method for GaN transistor solves the issue of high reverse conduction voltage drop in some extent, but not completely, and the problem of driving voltage ringing still exists. This paper proposes an improved three-level driving method for GaN transistor in synchronous Buck converter. The method can reduce the reverse conduction loss within the whole load range and effectively decrease the ringing of the driving voltage. The mechanism for the reduction of the driving voltage ringing is presented and simulation results verify the analysis finally.