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TIDM-HV-1PH-DCAC: PWM with frequency >20kHz

Part Number: TIDM-HV-1PH-DCAC
Other Parts Discussed in Thread: TMS320F280049C

Hello,

I work with TIDM-HV-1PH-DCAC evm. I have a problem with the PWM generation.

At 20kHz, everything is fine : the low frequency PWM toggle at the same time as the high frequencies. 

But if I increase the PWM frequency (50kHz), the low frequency PWM toggle 10µs after :

In the code from TI :

if(duty>=0)
{
// CTR = CMPA@UP , set to 1
EPWM_setActionQualifierAction(base1, EPWM_AQ_OUTPUT_A , EPWM_AQ_OUTPUT_HIGH, EPWM_AQ_OUTPUT_ON_TIMEBASE_UP_CMPA);
// CTR = CMPA@Down , toggle
EPWM_setActionQualifierAction(base1, EPWM_AQ_OUTPUT_A , EPWM_AQ_OUTPUT_TOGGLE, EPWM_AQ_OUTPUT_ON_TIMEBASE_DOWN_CMPA);
// CTR=0, clear to 0
EPWM_setActionQualifierAction(base1, EPWM_AQ_OUTPUT_A , EPWM_AQ_OUTPUT_LOW, EPWM_AQ_OUTPUT_ON_TIMEBASE_ZERO);
// CTR = CMPA@Down , clear
EPWM_setActionQualifierAction(base2, EPWM_AQ_OUTPUT_A , EPWM_AQ_OUTPUT_LOW, EPWM_AQ_OUTPUT_ON_TIMEBASE_DOWN_CMPA);
}
else
{
// CTR = CMPA@UP , clear to 0
EPWM_setActionQualifierAction(base1, EPWM_AQ_OUTPUT_A , EPWM_AQ_OUTPUT_LOW, EPWM_AQ_OUTPUT_ON_TIMEBASE_UP_CMPA);
// CTR = CMPA@Down , toggle
EPWM_setActionQualifierAction(base1, EPWM_AQ_OUTPUT_A , EPWM_AQ_OUTPUT_TOGGLE, EPWM_AQ_OUTPUT_ON_TIMEBASE_DOWN_CMPA);
// CTR=0, set to 1
EPWM_setActionQualifierAction(base1, EPWM_AQ_OUTPUT_A , EPWM_AQ_OUTPUT_HIGH, EPWM_AQ_OUTPUT_ON_TIMEBASE_ZERO);
// CTR = CMPA@Down , set
EPWM_setActionQualifierAction(base2, EPWM_AQ_OUTPUT_A , EPWM_AQ_OUTPUT_HIGH, EPWM_AQ_OUTPUT_ON_TIMEBASE_DOWN_CMPA);
}

Why the ActionQualifier of base2 (low freq) have this 10µs delay ?

Thanks,

Nicolas