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 temperatures||120°C Deg||Failed in less than 2 minutes|
|VisIC GaN case temperature||52°C Deg||Operated continiously|
|Heat Sink on Transistor on||Q1 removed|
|Frequency||Varied up to 250kHz|
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.