TIDA-00443: Input cap RMS current calculation

Hi, Milarepa

I have replied your questions, pls refer to below thread.

https://e2e.ti.com/support/tools/simulation-hardware-system-design-tools-group/sim-hw-system-design/f/simulation-hardware-system-design-tools-forum/1181943/tida-00443-input-cap-design/4455180#4455180

Thanks

Hely

Hi,

I agree that the cap current should be a sine wave not a triangular wave as i have drawn. So, if you calculate the RMS, it comes out to be 0.972 A.

So, one capacitor is good enough, as it can carry 2A RMS at 100 kHz, as per the datasheet.

Now, if say,  i am not connecting earth terminal and hence do not want any CM filter, can i go ahead with just one capacitor.

Thanks and regards,

I think ripple current is not sinusoidal, because for switching period duration, the voltage across the inductor can be assumed to be constant voltage, and hence current ripple rise and fall will be linear. Its more a triangular waveform than sinusoidal. Therefore, the capacitor current is a triangular waveform as I had drawn before.

Hi, Milarepa,

Hely is in sick leave, Hely will reply you on January 3rd, thanks.

BR

Jenson

Wishing him speedy recovery!

Thank you please be patient and we will answer your questions later.

Jenson