Abstract
This paper attempts to disclose a new GaN-based device, called the P-Cascode GaN HEMT, which uses only a single gate driver to control both the D-mode GaN and PMOS transistors. The merit of this synchronous buck converter is that it can reduce the circuit complexity of the synchronous buck converter, which is widely used to provide non-isolated power for low-voltage and high-current supply to system chips; therefore, the power conversion efficiency of the converter can be improved. In addition, the high side switch using a single D-mode GaN HEMT, which has no body diode, can prevent the bi-directional flow and thus reduce the power loss and cost compared to a design based on a series of two opposite MOSFETs. The experiment shows that the proposed P-Cascode GaN HEMT efficiency is above 98% when it operates at 500 kHz with 6 W output. With the input voltage at 12 V, the synchronous buck converter provides an adjustable regulated output voltage from 1.2 V to 10 V while delivering a maximum output current of 2 A.
Highlights
Synchronous buck converters are widely used in industries, consumer, and automotive applications
In the context of this paper, we focused only on the continuous current mode (CCM) application using the synchronous buck converter for maintaining the stable voltage output
An innovative design of a new GaN HEMT synchronous buck converter is proposed. This synchronous buck converter is associated with a PMOS transistor; it will need only one single gate drive to perform the DC/DC conversion, which is suitable for the point of load (POL) applications
Summary
Synchronous buck converters are widely used in industries, consumer, and automotive applications. As the size becomes more compact, designers have turned to faster switching speeds in order to reduce the size of the converter [1,2]. The switching speed is limited by the switching loss and the reverse recovery characteristic of the transistors. Wide-bandgap devices, such as GaN and SiC, have the potential benefits of achieving high switching and high efficiency capability because of their superior material properties, including a small gate charge and low Coss loss [3,4]. The disadvantage of the GaN HEMTs is the normally-on characteristic with negative Vth. From the fail-safe and simple gate drive point of view, cascode configuration is one of the suitable ways to turn the normally-on into normally-off devices [5]
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