GaN, E-HEMT bridgeless-totem-pole power factor correction reference design

GaN, E-HEMT bridgeless-totem-pole power factor correction reference design

Market news |
By Graham Prophet

The major hurdle, the company says, is fixed diode bridge losses. An option to overcome this is to use silicon MOSFETs in place of the diodes to achieve efficiencies of 99% or more. However, this BTPPFC approach suffers from poor reverse recovery performance, is suitable only for low power, and requires complicated control parameters. GaN Systems mitigates these drawbacks by replacing silicon MOSFETs with GaN E-HEMTs that eliminate the body diode (zero Qrr) and exhibit very fast switching. This also provides design engineers with a platform to demonstrate the performance of GaN HEMTs,


The 3 kW GS665BTP-REF reference design compares the switch-on losses of a silicon-based CoolMOS CFD2 with losses exhibited by a GaN Systems 650 V E-HEMT. The results show that GaN has superior reverse recovery. Operating the CCM BTPPFC at 50 kHz, GaN dissipates only 0.75W switching loss due to the Qoss Loss at turn-on, while the CoolMOS CFD2 shows a loss of 20W, solely due to Qrr. The result is excellent hard-switching performance in a CCM BTPPFC with maximized efficiency.



The figure shows the topologies of a BTPPFC. It can be considered as a conventional boost PFC in which one half of the diode bridge is replaced by active switches S1 and S2 in a half bridge configuration, hence the name “totem pole”. The diode D1/D2 forms the slow 50/60Hz line frequency leg which can either be slow AC rectifier diodes or can be replaced by low-RDS(on) synchronous MOSFETs for improved efficiency, as shown.


Comprehensive documentation for the GS665BTP-REF reference design, entitled “High-Efficiency CCM Bridgeless Totem Pole PFC Design using GaN E-HEMT,” is available for download from GaN Systems website. The documentation includes the motivation, operating principles, and design considerations for the BTPPFC using 650 V GaN E-HEMTs. Also included in the documentation are discussions pertaining to test setup, test results (i.e. efficiency, power factor, waveforms, thermal measurements), and applications.


GaN Systems;




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