GaN HEMT transistors top 99% efficiency in power switching

Technology News |
By Nick Flaherty

The ALL-Switch V22S65A (with an internal SiC diode) and V22N65A (without internal SiC diode) devices significantly reduce the MILLER effect enabling readily available, standard drivers to be used. These new devices also reduce the bill of materials for switching topologies with a System-in-Package (SIP) that combines a patented, high-density, lateral-layout GaN power transistor with control block circuitry and an optional SiC Schottky diode into a product with a low RDS(ON) of 15mΩ,  fast 200kHz switching performance and a small, surface mount footprint. VisIC has demonstrated record efficiencies with performance of its Half Bridge demonstration board, achieving better than 99.3 % peak efficiency at 200 kHz in a hard-switched topology providing 2.5KW output.

The tester output shown above uses a Continuous Current Mode with a Switching frequency of 200kHz, Dead Time of 100ns, Vin =401.219Vdc Vout=229.626V Pin=2502W Rise time=11.5ns Iin=6.2362A Iout=10.822A Pout=2485W Fall Time=18.5ns, giving an efficiency of 99.3%.

The V22 series may be used for hard switching Zero Voltage Switching or Zero Current Switching topologies. At 15mΩ, it has the lowest RDS(on) among either 650V GaN or SiC MOSFET transistors, and can achieve extremely efficient power conversion with slew rate exceeding 100V/ns. In addition, as the threshold voltage exceeds 5V, the devices work well in harsh EMI environments.

The devices use a MISHEMT (Metal Insulator Semiconductor – HEMT) structure and are voltage-controlled like the MOSFETs used in most power system designs but exhibit only monotonic transfer characteristics making power system design less complex and easing the adoption of this next-generation of power devices. The ALL Switch SIP design overcomes the major factors which have limited wide adoption of GaN transistors for power switching applications with a  high positive threshold voltage of  >+3V, as opposed to the low threshold voltage (typically around 1V) of existing GaN E- mode transistors.  This gives the devices higher EMI immunity in high voltage systems where high current  transitions can cause voltage spikes. The igh breakdown voltage of more than 800V enables safe blocking voltage up to 650 V, and a low voltage drop allows reverse conductivity operation.

Based in Nes Ziona, Israel, VisIC Technologies was established in 2010 by experts in GaN technology, and the company expects GaN to replace most of the silicon and SIC-based products currently used in power conversion systems. The devices are currently manufactured on 150mm GaN-on-Si wafers.


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