SPWM using F28035 ePWM

Hello,

I am using the Ti F28035 microcontroller to generate sine PWM, as depicted in the PWM figure. I have successfully generated a signal. However, I've encountered an issue with the signal's frequency. Instead of the desired 60 Hz, it measures at 232.7 mHz on the oscilloscope, despite achieving a switching frequency of 50 kHz, which I confirmed. I have created a Simulink model, as illustrated in Figure 2, with the sine parameters provided in the figure. I kindly request assistance in resolving this matter to attain the 60 Hz pulse."

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Answer 1

[Sayan]

Hi Derick,

I understand from your issue that the SPWM frequency is not the same as desired (60 Hz) when you try to generate it with the model shown above using the ePWM block.

The possible reasons for the same and their resolution are mentioned below.

• You have provided the value of "Samples per period" of the Sine Wave block as "floor((2*pi)/(60*1e-5))" which does not implement discrete sine wave of frequency 60 Hz. You can use "floor(1/(60*1e-5))" which will implement 60Hz discrete sine wave as the reference "CMPA" values for the ePWM block.
• Verify the comparison conditions with "CMPA" and "CMPB" in the "ePWMA" and "ePWMB" tabs are selected as required.

You can find more information on Sine Wave and ePWM blocks in the following documentations.

• Sine Wave : https://www.mathworks.com/help/simulink/slref/sinewave.html
• ePWM : https://www.mathworks.com/help/ti-c2000/ref/c280xc2802xc2803xc2805xc2806xc2833xc2834xf28m3xf2807xf2837xdf2837xsf2838xf2800xxepwm.html

Hope this helps in resolving the issue.