TIDM-HV-1PH-DCAC: Which frequency was selected for the Low frequency switches

Hi,

The low frequency is turned on and off based on ac line cycle.

Please check 'Figure 2. PWM Waveform Generation Using PWM Peripheral on C2000 MCU' in the user guide ( p.6).

Best,

John

hi John,

Thanks for the reply.  That means that  the low frequency is either 50 0r 60 hz.  I however have another question.

In the example (voltageSourceInverterLCFltr_F28004x) that relates to the application report, both epwms were configured for 20 KHz.  This negates the Figure 2.  The code is below:

setupInverterPWM(INV_PWM1_BASE,INV_PWM2_BASE,
INV_PWM_PERIOD,INV_DEADBAND_PWM_COUNT,
INV_DEADBAND_PWM_COUNT);

void setupInverterPWM(uint32_t base1, uint32_t base2, uint16_t pwm_period_ticks,
uint16_t pwm_dbred_ticks, uint16_t pwm_dbfed_ticks)
{
//
// PWM clock on F2837x is divided by 2
// Deadband needs to be 0.5us => 10ns*50=500ns
// Time Base SubModule Registers
//
EPWM_setPeriodLoadMode(base1,EPWM_PERIOD_SHADOW_LOAD);
EPWM_setTimeBasePeriod(base1,pwm_period_ticks >>1);
EPWM_setTimeBaseCounter(base1,0);
EPWM_setPhaseShift(base1,0);
EPWM_setTimeBaseCounterMode(base1,EPWM_COUNTER_MODE_UP_DOWN);
EPWM_setClockPrescaler(base1,EPWM_CLOCK_DIVIDER_1,EPWM_HSCLOCK_DIVIDER_1);

EPWM_setPeriodLoadMode(base2,EPWM_PERIOD_SHADOW_LOAD);
EPWM_setTimeBasePeriod(base2,pwm_period_ticks >>1);
EPWM_setTimeBaseCounter(base2,0);
EPWM_setPhaseShift(base2,0);
EPWM_setTimeBaseCounterMode(base2,EPWM_COUNTER_MODE_UP_DOWN);
EPWM_setClockPrescaler(base2,EPWM_CLOCK_DIVIDER_1,EPWM_HSCLOCK_DIVIDER_1);

How am I best to interpret this.

Thanks

Hi,

Check duty update code below. base2_EPWM is set to 1 and AQ setting is changed depending on duty (positive or negative)

static inline void updateInverterPWM(uint32_t base1, uint32_t base2,
float32_t duty)
{
uint16_t invDuty;

invDuty= ((float32_t)(INV_PWM_PERIOD/2.0f)) * (1.0f-fabsf(duty));

if(invDuty==(EPWM_getTimeBasePeriod(base1)))
{
invDuty=invDuty-1;
}

EPWM_setCounterCompareValue(base1,EPWM_COUNTER_COMPARE_A,invDuty);
EPWM_setCounterCompareValue(base2,EPWM_COUNTER_COMPARE_A,1);

// Used for debugging purposes
// wait for the PWM to start counting down
// make sure the PWM is counting down
// if(EPWM_getTimeBaseCounterDirection(base1)==0)
// {
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);
}
// }
}