Abstract
The conventional cascode structure for driving depletion-mode (D-mode) gallium nitride (GaN) high electron mobility transistors (HEMTs) raises reliability concerns. This is because of the possibility of the gate to source voltage of the GaN HEMT surging to a negative voltage during the turn off transition. The existing solutions for this problem in the literature produce additional drawbacks such as reducing the switching frequency or introducing many additional components. These drawbacks may outweigh the advantages of using a GaN HEMT over its silicon (Si) alternative. This paper proposes two innovative gate drive circuits for D-mode GaN HEMTs—namely the GaN-switching based cascode GaN HEMT and the modified GaN-switching based cascode GaN HEMT. In these schemes, the Si MOSFET in series with the D-mode GaN HEMT is always turned on during regular operation. The GaN HEMT is then switched on and off by using a charge pump based circuit and a conventional gate driver. Since the GaN HEMT is driven independently, the highly negative gate-to-source voltage surge during turn off is avoided, and in addition, high switching frequency operation is made possible. Only two diodes and one capacitor are used in each of the schemes. The application of the proposed circuits is experimentally demonstrated in a high voltage flyback converter, where more than 96% efficiency is obtained for 60 W output load.
Highlights
Gallium nitride (GaN) high electron mobility transistors (HEMT) are a new disruptive technology that has the potential to change the power electronics industry drastically.GaN devices offer superior converter performance due to their ability to switch at higher frequencies than conventional Silicon (Si) devices [1,2,3,4,5,6,7]
It is observed that the ratio between the drain–source voltage of the GaN is 40 times as the drain–source voltage of the MOSFET
Order to avoid a large portion of the drain–source voltage with a low voltage in order to avoid a large portion of the drain–source voltage falling on the MOSFET during its turn-off time and permanently damaging the GaN HEMT
Summary
Gallium nitride (GaN) high electron mobility transistors (HEMT) are a new disruptive technology that has the potential to change the power electronics industry drastically.GaN devices offer superior converter performance due to their ability to switch at higher frequencies than conventional Silicon (Si) devices [1,2,3,4,5,6,7]. GaN HEMTs are gaining popularity in switching power supplies because they are inherently normally off devices [8,9,10]. These devices have stringent gate driving voltage limits (–10 to 7 V) and often require additional protection circuits [11]. Depletion-mode (D-mode) GaN HEMTs are normally on devices, which have a wider gate voltage range (–30 to 8 V) [12]. D-mode GaN HEMTs usually offer lower on-resistance and smaller junction capacitances than rated E-mode devices [13]
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