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please suggest me a procedure

Naveen Rangu
Intellectual 600 points

Hi,

can any one help me in generating SPWM signals using F28335?

please give some procedure to to generate SPWM.I know general procedure like comparing two waveforms i.e carrier and modulated (traingular and sinusoidal ) signals

and producing pulses by comparision.

I have some idea , tell me whether it is correct or not?

 EPwm1Regs.CMPA.half.CMPA = x1; (where x1 = sgen1.out)  (For Sinewave )

but how to generate traingular with positive nad negative cycles, if i choose the follwing ,it will generate only positive traingular wave;

 EPwm1Regs.TBPRD = 3750;  // for 20KHz

EPwm1Regs.TBCTL.bit.CTRMODE = TB_COUNT_UPDOWN;

is above one is correct or not?

please help me out in this issue

 

Thanks & regards,

Naveen Rangu

 

 

 

 

 

  • 0
    Intellectual 665 points

    Hi Naveen,

     

    I assume you mean space vector PWM... One common trick in order to get negative signals is to shift your reference. For example, if your inverter can only give 0-100V at its output, you could use a reference of 50V and the outputs would then become -50 to +50V. SVPWM is another way of looking at three phase PWMs, and you can probably read more about it on your own.

    In terms of the data you put in the registers, you always need to scale things properly. If the output of your controller is a certain amount of volts, you need to scale it to your PWM period and DC bus to get a value appropriate for your compare register.

    Read about:

    - inverters: motor drives might be a good start

    - fixed point math