150W PFC THERMAL MANAGEMENT
SIMPLIFIED USING GaN vs Si MOSFETs

The following circuit diagram shows a common AC/DC power supply topology implementing a PFC block to convert the AC line input to 400VDC using a high voltage transistor (Q1 in the figure below) for the PWM switch. At the customer’s request, VisIC measured performance parameters with Q1 as an IPA50R250 Si MOSFET (as in the customer’s design) and as replaced by VisIC’s VT15R65.
The heat sink in the customer’s design was removed during the measurements.

Fig 1. PFC using NCP1612 controller and Q1 as the main switch

 

Table 1. Case temperatures:
Infineon IPA50R250 Si MOSFET vs VisIC VT15R65 GaN MISFET
Infeneon MOSFET case temperatures120°C DegFailed in less than 2 minutes
VisIC GaN case temperature52°C DegOperated continiously

 

Conditions:
Heat Sink on Transistor onQ1 removed
PFC Controller ON/NCP1612
Frequency Varied up to 250kHz
Pout 150W
Vout 400VDC
Vin85VAC
Conclusion

1.Switching losses are reduced: GaN transistor switches in 4-5 nS compared to 15-20 nS for Si MOSFET.

2.Conduction losses are reduced: 15 mOhm VisIC GaN transistor is a very high conductance switch compare to 150-250 mOhm Si MOSFET.

3.Case temperature is drastically reduced. In the same application the circuit using VisIC’s GaN transistor can work without a heat sink.

Contacts

Address
VisIC Technologies LTD
Golda Meir 7
Nes Ziona, 7403650 Israel

Telephone
972 8 9720090

Fax
972 8 6909467

E-mail
eliz@visic-tech.com