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Wide bandgap devices are enabling high-efficiency operation for 6.78 MHz highly resonant wireless power applications based on the AirFuel standard. Wireless power systems need to move beyond charging pads and become considered power sources. To do this they need to support a larger area such as an office desk and increase their power capability. This demands fundamental changes in coil technology...
This paper presents a monolithic multilevel converter realized in a depletion-mode GaN process and intended to operate as a drain supply modulator (DSM) for high efficiency radio-frequency (RF) power amplifiers (PAs). The custom prototype chip includes a four-level power stage with on-chip integrated gate drivers and damping networks designed to mitigate effects of parasitics during output voltage...
This paper introduces an envelope tracking (ET) power supply for 4G cell phone base stations using EPC eGaN® FETs. An analytical loss model is developed for design optimization and verified by a single phase synchronous buck converter using the zero-voltage switching (ZVS) technique. The model is then extended to four phases and is used to design a 60 W ET power supply with 20 MHz large signal bandwidth...
This paper presents high efficiency de-de converters based on monolithic normally-off GaN half-bridge power stages with integrated gate drivers. A new gate driver circuitry is introduced, which enhances both the power stage efficiency and the converter overall efficiency. While using only n-type transistors in the GaN process, the proposed gate driver maintains low quiescent power consumption by emulating...
This paper describes very high frequency (10–200 MHz) switched-mode power converters using custom GaN chips with integrated power switches and gate drivers, allowing standard logic-level PWM control inputs. Circuit design techniques are described in depletion-mode 0.15μm RF and 0.25μm switch GaN-on-SiC processes, including integration of gate-drive and level translation circuits. Operating from up...
This paper describes a very high frequency (VHF) isolated dc-dc resonant converter operating at 100 MHz switching frequency with a rated output power of 2 W. The power stage consists of two half-bridge GaN chips with integrated gate drivers, one operating as a dc-ac inverter on the primary side, the other operating as an ac-dc synchronous rectifier on the secondary side. Isolation is provided by a...
This paper describes a closed-loop regulated dual half-bridge series resonant de-de converter operated at up to 100 MHz switching frequency using GaN half-bridge stages with integrated gate drivers. A digital online efficiency optimization technique together with burst-mode control are developed and applied, to achieve output voltage regulation and efficiency improvements. An experimental prototype...
Supply modulation is a system efficiency improvement technique in radio-frequency (RF) transmitters, where a power converter operating as an envelope tracking (ET) amplifier serves as the power supply for an RF power amplifier. This paper presents design of higher-order output filters in multi-phase buck ET amplifiers to achieve wide-bandwidth tracking with high efficiency using zero-voltage switching...
Linear-assisted switching power amplifiers are based on combinations of switching converters (for high efficiency) and linear amplifiers (for high-speed, wide bandwidth responses) in applications such as envelope tracking (ET) for radio-frequency (RF) power amplifiers. This paper presents a pre-filter design approach for band separation of inputs signals for the linear and the switching amplifier...
This paper describes a synchronous buck converter based on a GaN-on-SiC integrated circuit, which includes a halfbridge power stage, as well as a modified active pull-up gate driver stage. The integrated modified active pull-up driver takes advantage of depletion-mode device characteristics to achieve fast switching with low power consumption. Design principles and results are presented for a synchronous...
This paper describes three driver options for integrated half-bridge power stage using depletion-mode GaN-on-SiC 0.15µm RF process: an active pull-up driver, a bootstrapped driver, and a modified active pull-up driver. The approaches are evaluated and compared in 5 W, 20 V synchronous Buck converter prototypes operating at 100 MHz switching frequency over a wide range of operating points. Measured...
GaN-on-SiC technology has been widely used in radiofrequency (RF) power amplifiers to achieve high power density at very high frequencies due to the enhanced power handling capabilities provided by the SiC substrate and very high transition frequencies of GaN High Electron Mobility Transistors (HEMTs). Along with other well-known advantages of GaN, such as high breakdown voltage and high temperature...
Distribution STATic synchronous COMpensator (DSTATCOM) can be used for reactive and harmonic current compensation. The safety and reliability of DC-bus voltage control are critical in practice in both dynamic process and steady state, especially for the ones of DC-bus self-regulation. This paper proposes a modulation-ratio-regulation based control strategy for the setup of DC-bus voltage of DSTATCOM...
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