PWM regenration

Dharmendra Savaliya

Intellectual 700 points

Here input is to DSP & Output is from DSP.

So we want to control PWM Duty cycle.

How can we do this is issue?

over 8 years ago

0 Aditya BG over 8 years ago

Expert 1825 points

Hi Dharmendra,

Could you please elaborate what exactly you are trying?

Aditya

0 Subrahmanya over 8 years ago in reply to Aditya BG

TI__Mastermind 24095 points

Interesting... Do you have the knowledge of the frequency of the incoming waveform before hand? Can we assume only duty cycle is varying and frequency stays the same?

0 Rasesh Dave over 8 years ago in reply to Subrahmanya

Prodigy 150 points

I am Working with Dharmendra. Answer to your question , Frequency is known and should stay same. Only Duty cycle is varying,

0 Rasesh Dave over 8 years ago in reply to Aditya BG

Prodigy 150 points

Its Duty Cycle Control for Chopper Unit.

0 Dharmendra Savaliya over 8 years ago in reply to Subrahmanya

Intellectual 700 points

Hi Subrahmanya sir,

We have constant frequency & want to vary duty cycle as well as clip duty if it is more than 90%.

Thank You.

0 Gautam Iyer over 8 years ago in reply to Dharmendra Savaliya

Guru 192875 points

So did you try varying the duty otg? This is very well possible.

0 Rasesh Dave over 8 years ago in reply to Gautam Iyer

Prodigy 150 points

Dear Gautam, Can you explain in detail? How to monitor Input signal's Duty and Blocking it if above 90%? We want it regeneration of output signal based on Input signal with minimum delay.

0 Gautam Iyer over 8 years ago in reply to Rasesh Dave

Guru 192875 points

Rasesh Dave said:
How to monitor Input signal's Duty and Blocking it if above 90%?

You can do the same in combination of eCAP and ePWM peripherals. eCAP can capture the incoming signal and calculate the duty for you which you can later pass it to ePWM peripheral to generate the same waveform. Delay should be very minimal.

Regards,

Gautam

0 Brett Larimore over 8 years ago in reply to Gautam Iyer

TI__Guru 57255 points

If all you want is clamping, a non-CPU intensive approach might be to:

Use a ePWM module to output a PWM at the same frequency as the input PWM. Set and use the CMPA such that it outputs at 90% duty cycle.
Enable synchronization such that the external signal generates a synch pulse for the ePWM module. This will then make sure that the input and output PWMs are in synch.
Use the ePWM's Digital Compare module to make your unclamped PWM signal trip the generated PWM signal on a falling edge. The trip you'd want to use is a cycle-by-cycle (CBC) trip.

I have not specifically tried this, but it should be possible.

===

If you want to edit or scale the duty cycle between the input and output, you'd likely instead need to do something like Gautam has mentioned.

At any rate, the above may give you some ideas on less CPU intensive possibilities.

Thank you,
Brett

0 Dharmendra Savaliya over 8 years ago in reply to Brett Larimore

Intellectual 700 points

Dear sir,

we found some theory for this step , but if you have any Example available please suggest us.

Thank you.

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PWM regenration