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How to synchronise my ADC with PWM anyone please help

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Submitted by Aditya23456 on Sun, 04/07/2013 - 05:38 

My main project is having maximum power point tracking of a pv cell using dspa kit...For this process I need my DSPA kit to sense V and I as input and calculate power(ie V*I) and it needs to compare its new power with power old and thereby varies its duty cycle in such a way that power stays outputs constant power and maximuk power too...I m using VISSIM software for this..I m trying to sense V and I through input ports of my DSPA kit by ADC functioning but I m not understanding how to link this output to ePWM in such a way that it varies duty cycle dynamically..Tutorials given are more of complex kind and they r trying to explain cases with 2 or more PWM units which is not needed in my case..ANyone plzz help because my project submission date is coming soona nd I m done with my hardware part ie boost converter , driver circuit etc etc..I hope I m clear if I not..I m ready to type it even more profoundly.

Thanking you, Aditya

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Your post title asks how you synchronize the ADC with the PWM unit. You do that by 1. configuring the PWM to send an SOC (Start of Conversion) pulse to the ADC unit, and 2. you configure the ADC Unit to listen for the pulse. The directions below apply to Texas Instruments Piccolo and Octave chip line.

  1. Each PWM unit can send up to 2 pulses, SOCA and SOCB. To configure the PWM: right click on the ePWM block, and selecting the PWM event for SOCA and SOCB as below.
    Usually it will be CTR=zero or CTR=PRD depending on your inverter topology, Action Qualifier configuration and PWM count mode. If you use up/down count, and active high AQ, for output A and complementary on output B, then CTR=zero will give you the middle of the A on time, and CTR=PRD will give you middle of the B on time (normally B is used to switch the lower half H-bridge to ground, where it is common to find a shunt resistor)

  2. Configure the ADC channel by selecting Embedded > F280x > ADC Config..., then choose the trigger source for each ADC channel as below:

But then the body of your post goes on to ask how to link VI measurements as feedback control to your PWM. That is a general control question. You can use a PID to maintain a set point power and the output of the PID can be fed directly to the ePWM input.

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