CCM-BOOST Datasheet, PDF (15/18 Pages) Infineon Technologies AG – CCM PFC Boost Converter Design

CCM PFC Boost Converter Design
Design Note DN 2013-01
V1.0 January 2013
Heatsink
The MOSFET and diode can have separate heatsinks or share the same one, however, the selection of the
heatsink is based on its required thermal resistivity.
In case of separate heatsinks for the diode and
MOSFET, thermal resistors are modeled as in Figure
4.5.
P_{FET TJ.FET RthJC.FET TC.FET RthCS.FET TS.FET RthSA.FET}
P_{diode TJ.diodeRthJC.diode TC.diode RthCS.deiode TS.diodeRthSA.diode}
Figure 4.5
In case of a single heatsink for both the diode and the
MOSFET, thermal resistors are modeled as in Figure
4.6.
The maximum heatsink temperature is the minimum
outcome of the two equations below
Once
is specified, then the heatsink thermal
resistance can be calculated.
P_{FET TJ.FET RthJC.FET TC.FET RthCS.FET}
P_{diode TJ.diode} R_{thJC.diode TC.diode RthCS.diode}
T_S ^RthSA T_A
P_FET+P_diode
Figure 4.6
is the thermal resistance from junction to case, this is specified in the MOSFET and Diode datasheets.
is the thermal resistace from case to heatsink, typically low compared to the overall thermal resistance,
its value depends on the the interface material, for example, thermal grease and thermal pad.
is the thermal resistance from heatsink to ambient, this is specified in the heatsink datasheets, it
depends on the heatsink size and design, and is a function of the surroundings, for example, a heatsink
could have difference values for
for different airflow conditions.
is the heatsink temperature, is the case temperature , is the ambient temperature.
is FET’s total power loss ,
is diode’s total power loss.
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