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how can centered waveforms be achieved for a half h-bridge?

Les Nelson
Prodigy 110 points

The half h-bridge example in Section 3.5 of spruge9d shows that the top and bottom waveforms of a half bridge are NOT centered with respect to each other.

How can these upper and lower half h-bridge waveforms be centered such that:

time between turn-off of upper switch and turn-on of lower switch = time between turn-off of lower switch and turn-on of upper switch ?

 

  • 0
    Prodigy 110 points

    Solution - this code produces half h-bridge waveforms that are centered with respect to each other, instead of run together (as the TI examples show):

     

     

     

     

     

    EPwm5Regs.AQCTLA.bit.ZRO = 0x2 ;

    // make epwm5a output high when counter = 0 and is incrementing
    EPwm5Regs.AQCTLA.bit.CAU = 0x1 ;  // make epwm5a output low when counter = cmpa and is incrementing
    EPwm5Regs.AQCTLB.bit.PRD = 0x2 ; // make epwm5b output high when counter = period and is starting to decrement
    EPwm5Regs.AQCTLB.bit.CBD = 0x1 ; // make epwm5b output low when counter = CMPB and is decrementing
    EPwm5Regs.CMPA.half.CMPA = 290 ; // 150 FOR 50% DUTY CYCLE ADJUST: between 0 and EPwm5Regs.TBPRD = 300
    EPwm5Regs.CMPB = EPwm5Regs.TBPRD - EPwm5Regs.CMPA.half.CMPA ; // this centers the upper and lower waveforms with respect to each other.