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Dear Sir,

How to evaluate power device junction temperature, at the time of Eon?

For example, the power dissipation I see is about 6kW+2.3kW,

Is my temperature rise equal to TA + (6kW+2.3kW) *RJA?

Solved! Go to Solution.

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Hello Kuowenyung,

Temperature rise has to be estimated based on the average losses and not considering the peak dissipation.

You may estimate the average loss during turn-on as below, by approximating the power curve as a triangle.

Psw_on = (1/2 * ton * Vds*Id)/T

where T - total switching period

Here 6kW would account for Vds*Id.

Temperature rise due to the turn-on losses can be calculated as below

Tj= Psw_on * Rthj-a + Ta

But you may not be able to observe this change in real-time as temperature rise will be gradual and not instantaneous.

Hence to estimate the actual junction temperature of your device, it is advised to estimate the total power loss over a switching period, which will include both conduction and switching losses and then calculate the junction temperature as below.

Tj= Ploss*Rthj-a + Ta

where Ploss = Pcond + Psw

I hope this helps. Please feel free to reach out to us if you need further clarification on this topic.

Regards

Meghana R

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Hello Kuowenyung,

Temperature rise has to be estimated based on the average losses and not considering the peak dissipation.

You may estimate the average loss during turn-on as below, by approximating the power curve as a triangle.

Psw_on = (1/2 * ton * Vds*Id)/T

where T - total switching period

Here 6kW would account for Vds*Id.

Temperature rise due to the turn-on losses can be calculated as below

Tj= Psw_on * Rthj-a + Ta

But you may not be able to observe this change in real-time as temperature rise will be gradual and not instantaneous.

Hence to estimate the actual junction temperature of your device, it is advised to estimate the total power loss over a switching period, which will include both conduction and switching losses and then calculate the junction temperature as below.

Tj= Ploss*Rthj-a + Ta

where Ploss = Pcond + Psw

I hope this helps. Please feel free to reach out to us if you need further clarification on this topic.

Regards

Meghana R