TPS54240: PSpice for TI: Invalid Expression Error When Using AVG(W(U1))

user1475503

Part Number: TPS54240

Tool/software:

This figure shows the simulation results obtained using TI’s TPS54240 in PSpice for TI. This waveform data was taken from the interval between 1.1ms and 1.2ms, where the output is stable. There are three waveforms: the top shows the output current (1.3A), the middle shows the power of the TPS54240, and the bottom shows the output voltage (3.3V).

To calculate the average power consumption of the TPS54240 (Reference No. = “U1”), I attempted to register AVG(W(U1)) in the Measurement settings in order to compute the average power during this interval. However, as shown in the figure, an Invalid Expression Error occurred, and I am unable to determine the cause. On the other hand, Max(W(U1)) and Min(W(U1)) can be registered correctly, as shown in the figure.

If anyone knows the cause of this issue and how to avoid it,

I would greatly appreciate your advice. Thanks in advance.

1 month ago

+1 Sourish Nandy 1 month ago

TI__Intellectual 2530 points

Hello,

Thanks for the query!

Can you send the file you ran this simulation on?

Thanks and Regards,

Sourish Nandy.

0 user1475503 1 month ago in reply to Sourish Nandy

Prodigy 50 points

Thank you for your reply.
I have attached the project file.
I have deleted the simulation result files as they become large in size.
The simulation profiles remain intact.
Please proceed with the simulation as is.
Thank you for your cooperation.

TPS54240_PSPICE_TRANS.zip

0 Sourish Nandy 1 month ago in reply to user1475503

TI__Intellectual 2530 points

Hello,

Thank for the reply!

Will get back to you as soon as possible.

Thanks and Regards,

Sourish Nandy.

0 Sourish Nandy 1 month ago in reply to Sourish Nandy

TI__Intellectual 2530 points

Hello,

Kindly wait for a little more time, will get back to you asap.

Thanks for the consideration.

Thanks and Regards,

Sourish Nandy

0 user1475503 1 month ago in reply to Sourish Nandy

Prodigy 50 points

Of course, I understand. I will await your response.

0 Sourish Nandy 1 month ago in reply to user1475503

TI__Intellectual 2530 points

Hi,

Thanks for considering.

Thanks and Regards,

Sourish Nandy.

0 Sourish Nandy 1 month ago in reply to Sourish Nandy

TI__Intellectual 2530 points

Hi Shinoda San,

You can use cursors for average value.

Steps]

1) Add the power trace by selecting Trace > Add Trace > Plot W(U1) [Already done by you]

2) Enable Cursors by selecting Trace > Cursors > Display.

3) Find Average by placing cursor 1 at start time and cursor 2 at end time. See the Cursor data window for the value.

I am attaching a screenshot for the same.

You can see the encircled average value.

Hope this clarifies your query.

Thanks and Regards,

Sourish Nandy.

0 user1475503 1 month ago in reply to Sourish Nandy

Prodigy 50 points

Hello Nandy,

Thank you very much for your step-by-step guidance on how to calculate the average power. Thanks to your instructions, I was able to correctly obtain the average power for the specified interval.

I do have one question. In the dialog that appears from the Trace → Add Trace menu, I can calculate the average power using AVG(W(U1)). However, when I enter the same AVG(W(U1)) in the dialog that opens by clicking the Evaluate Measurement icon, it results in an error. Could you please explain why this happens and what the difference is between the two methods?

In any case, my issue has been resolved. Once again.

Thank you very much for your kind support.

+1 Sourish Nandy 1 month ago in reply to user1475503

TI__Intellectual 2530 points

Hello Shinoda San,

Glad to hear that your query was resolved.

It may be due to the post processing process of Pspice and how it handles the calculation.

I will look into it and will inform you once I get an explanation.

Thanks and Regards,

Sourish Nandy.

0 user1475503 1 month ago in reply to Sourish Nandy

Prodigy 50 points

Hello Nandy,

Thank you for your continuous support.

I look forward to your reply at your convenience.

0 Sourish Nandy 1 month ago in reply to user1475503

TI__Intellectual 2530 points

Hello Shinoda,

Thanks for the consideration!

Thanks and Regards,

Sourish Nandy.

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TPS54240: PSpice for TI: Invalid Expression Error When Using AVG(W(U1))