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A power diode used in a cell phone tower power supply dissipating power during the conduction process requires its junction temperature on not to exceed 180 degrees C. The power diode data sheet gives conduction-state voltage drop of 1.8V and for the DO-4 diode case, the junction-to-case thermal resistance, R-theta , jcis 0.8 degrees C/W. The diode is mounted over a heat sink having thermal resistances, case- to-sink R-theta,cs = 0.3degrees C/W and sink-to-ambient R-theta, sa= 0.6degrees C/W. Calculate the maximum current that diode can withstand safely without overheating if the ambient temperature is 30 degrees C. Calculate the difference of temperature from case to sink. If the design requires to limit the junction temperature to 150 degrees C, select a value of R-theta,sa for a heat sink which should be used.

A power diode used in a cell phone tower power supply dissipating power during the conduction process requires its junction temperature on not to exceed 180 degrees C. The power diode data sheet gives conduction-state voltage drop of 1.8V and for the DO-4 diode case, the junction-to-case thermal resistance, R-theta , jcis 0.8 degrees C/W. The diode is mounted over a heat sink having thermal resistances, case- to-sink R-theta,cs = 0.3degrees C/W and sink-to-ambient R-theta, sa= 0.6degrees C/W. Calculate the maximum current that diode can withstand safely without overheating if the ambient temperature is 30 degrees C. Calculate the difference of temperature from case to sink. If the design requires to limit the junction temperature to 150 degrees C, select a value of R-theta,sa for a heat sink which should be used.

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A power diode used in a cell phone tower power supply dissipating power during the conduction
process requires its junction temperature on not to exceed 180 degrees C. The power diode data sheet gives
conduction-state voltage drop of 1.8V and for the DO-4 diode case, the junction-to-case thermal resistance, R-theta , jcis 0.8 degrees C/W. The diode is mounted over a heat sink having thermal resistances, case-
to-sink R-theta,cs = 0.3degrees C/W and sink-to-ambient R-theta, sa= 0.6degrees C/W.

  • Calculate the maximum current that diode can withstand safely without overheating if the
    ambient temperature is 30 degrees C.
  • Calculate the difference of temperature from case to sink.
  • If the design requires to limit the junction temperature to 150 degrees C, select a value of R-theta,sa for a
    heat sink which should be used.
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