TMS320F28335: How to remove PWM noise from measured AC signal.

Manish Girase

Part Number: TMS320F28335

Tool/software:

Dear Sir,

I am working with 3 phase Voltage source Inverter. Presently AC input is taken from 3 phase Variable voltage source. DC voltage is generated using Diode bridge. AC voltage is sensed using voltage divider network and OPAmp.

ADC input is filtered using RC network . If the PWN signal is off then the signal is clean . After switching on PWM (12.8 KHz) heavy noise is getting imposed on measured signal and the inverter outputs distorted AC Signal. Attaching screen shot of AC sampled signal. Please suggest how I can remove that noise from hardware itself.

over 1 year ago

0 Delaney Woodward over 1 year ago

TI__Mastermind 19375 points

Hi Manish,

The ePWM expert is currently out of office until Tuesday 7/9, so please expect some delay in response. I apologize for the inconvenience.

Best Regards,

Delaney

0 Shamim Choudhury over 1 year ago in reply to Delaney Woodward

TI__Genius 11855 points

It is not a PWM issue. It is the external RC filter that you are using to filter the ADC signal. Pls make sure you have RC filter cutoff frequency low enough so you get good attenuation of the PWM switching noise. Use RC filter cutoff of about 1/10 th of PWM frequency for this voltage signal that you are sensing

Other than that it could also be related to your PCB layout,

0 Manish Girase over 1 year ago in reply to Shamim Choudhury

Intellectual 360 points

Thanks Shamim for your help. I will cross check and come back to you very shortly.Please keep the case open.

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TMS320F28335: How to remove PWM noise from measured AC signal.