Q13. A buck converter is constructed with a MOSFET which has anon-state resistance of 75m?, and a diode with a forward voltagedrop of 1.3V. The MOSFET exhibits switching rise and fall times of50ns. The converter operates from an input voltage of 400V and. Theconverter supplies 1.2kW at an output voltage of 300V and switchesat 150kHz. The MOSFET and the diode are mounted onto separateheatsinks. The ambient temperature in which the power converteroperates is 45°C.
Other thermal data are:
MOSFET Junction to case thermal resistance, R?jc 0.5°C/W, Caseto heatsink thermal resistance, R?chs 1.2°C/W
Diode Junction to case thermal resistance, R?jc 0.8°C/W ,Case toheatsink thermal resistance, R?chs 1.5°C/W
(a) Calculate the power dissipation in the MOSFET.
(b) Calculate the power dissipation in the diode.
(c) Calculate the thermal resistance of each heatsink if thetemperature of the devices’ junctions is to be restricted to110°C. Â
