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TPS51220: Light load induct temperature

GARETH OU
Mastermind 9465 points
Part Number: TPS51220

Hi

My customer has a question about the TPS51220 inductor temperature is higher 

The following are the application conditions and test results

vin=19v

vout=12v (Ch2)

Iout=0.1A 

L=4.7u (DCR30m ohm)

When the output current is 0.1A and the inductor temperature is above 40C, MODE =CCM

Thank you

  • 0
    TI__Expert 5060 points

    Hi Gareth,

    What's the switching frequency of the controller?

    The temperature rise of inductor is a normal phenomenon, since there's AC loss (AC copper loss + core loss) for inductor. With CCM mode, the inductor current ripple won't be reduced at light load. 

    Or could you help to get the part no of inductor? We can find if there's any corresponding calculation tool or simulation tool for the inductor to give an explanation.

    Regards,

    Andrew

  • 0 in reply to Andrew Xiong
    Mastermind 9465 points

    Hi Andrew

    Thank you for you support

    frequency =300khz

    DCM can reduce the inductor current ripple at ligh load?

  • 0 in reply to GARETH OU
    TI__Expert 5060 points

    Hi Gareth,

    DCM itself cannot reduce the current ripple. On-time reduction in the DCM implementation for some part can reduce current ripple. But what affects most is that the switching frequency is reduced a lot in DCM, so the AC loss of inductor will be reduced a lot.

    For the AC loss estimation, since the inductor suppliers normally don't provide detailed data for the AC loss analysis. I can just do some simple study here to show you some inaccurate analysis results. If you want to analyze accurately or choose a inductor with smaller AC loss, you should ask the inductor supplier for more information.

    I didn't find the part no of inductor that you provided. But I found a inductor with similar spec and similar part no from Cyntec. 

    On the website of inductor supplier Cyntec, it does provide the loss calculator for some inductor, but I didn't find the calculator for this one. I tried to choose a most similar one with 4.7uH inductance. Through the calculator, it can be seen that the temp rise is about 25C. So I think the temperature rise is a normal condition, the easiest method for optimization is just to choose a inductor with small AC loss and small thermal resistance.

    Also, you can check the inductor current to eliminate the concerns of IC. If there's no abnormal waveform for the inductor current, then it's all about inductor it self.

    Regards.

    Andrew