C. The power transistor above is subject to a short-time overload during transient operation. Junction-to-case thermal impedance against be pulse duration characteristic of the transistor is given in Fig. 2. Let the ambient temperature TA= 40C. i. If the transistor is subject to a single heating power pulse of PpM= 600 W during 200 us time,calculate the peak value of the junction temperature at the end of the pulse. Assume that the heat sink has a very large thermal storage capacity and that the case temperature remains constant at Tc= 40C during this short-time pulse duration. ii. By considering that the operating duty cycle of the transistor is D=0.2, calculate the peak value of the junction temperature rise above the case temperature for the power pulse in (i) applied repetetively. Comment on the results. 10 Thermal Response (Zec) 0.2 0.1 0.1 0.05 0.02 0.01 SINGLE PULSE (THERMAL RESPONSE) 10-2 10-6 NOTES 1. DUTY FACTOR, D-4,12 2. PEAK T, POM X Zinc + Tc 10-3 10-2 0.1 1 t. Rectangular Pulse Duration (seconds) 10-4 10 Fig.2. Junction-to-case thermal impedance against pulse duration characteristic of the power transistor C. The power transistor above is subject to a short-time overload during transient operation. Junction-to-case thermal impedance against be pulse duration characteristic of the transistor is given in Fig. 2. Let the ambient temperature TA= 40C. i. If the transistor is subject to a single heating power pulse of PpM= 600 W during 200 us time,calculate the peak value of the junction temperature at the end of the pulse. Assume that the heat sink has a very large thermal storage capacity and that the case temperature remains constant at Tc= 40C during this short-time pulse duration. ii. By considering that the operating duty cycle of the transistor is D=0.2, calculate the peak value of the junction temperature rise above the case temperature for the power pulse in (i) applied repetetively. Comment on the results. 10 Thermal Response (Zec) 0.2 0.1 0.1 0.05 0.02 0.01 SINGLE PULSE (THERMAL RESPONSE) 10-2 10-6 NOTES 1. DUTY FACTOR, D-4,12 2. PEAK T, POM X Zinc + Tc 10-3 10-2 0.1 1 t. Rectangular Pulse Duration (seconds) 10-4 10 Fig.2. Junction-to-case thermal impedance against pulse duration characteristic of the power transistor