Answer to Question #186108 in Electrical Engineering for Kingsley yuan

Question #186108

You are required to design the heatsink for the power transistor of a voltage regulator, keeping the heatsink cost minimal. The voltage regulator has an output voltage of 5 V and a full load current of 500 mA. At full load, the regulator efficiency is 25 %, with the power transistor contributing to 45% of the power loss. The regulator is expected to operate at ambient temperature of between 20 °C and 40 °C. The heatsink temperature should not be more than 80 °C. Assume the cost of the heatsink is inversely proportional to the value of the thermal resistance θ_SA. The power transistor has the following parameters: θ_JC = 3 °C /W TJ, max = 150 °C Determine the thermal resistances, θ_CS and θ_SA.