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TMS320F280049: Using Tripzone to trigger two PWM?

Watermelon and Noodles
Prodigy 40 points
Part Number: TMS320F280049
Other Parts Discussed in Thread: TIDM-1007

Hi,experts

This is PWM and CBC-OCP, designed for Totempole bridgeless PFC.

Here, I need to use two PWM for one half bridge, and the two PWMs are compensate with each other. ( If PWM1 is low, PWM2 is high; if PWM2 is low, PWM2 is high. And, there should be deadtime both are low)

When I using the tripzone to do the CBC OCP protection, I need to trip PWM1 low@'positive AC line cycle', and trip PWM2 low @ 'negative AC line cycle'.

But, when the trip happens, I sametime need to the compensated PWM channel. That means when PWM1 is triped to low, PWM2 should be forced to high with a deadtime.

Could I use a same tripzone to trigger PWM1 low and PWM2 high in 'positive AC line cycle', and reverse the action (trigger PWM2 low, and PWM1 high) in 'negative AC line cycle'?

How to do that?

  • 0
    TI__Mastermind 43730 points

    "Could I use a same tripzone to trigger PWM1 low and PWM2 high in 'positive AC line cycle', and reverse the action (trigger PWM2 low, and PWM1 high) in 'negative AC line cycle'?"

    You can use the same trip zone to only affect xA or xB is a programmable manner, please see registers TZCTL, TZA and TZB are different register bits.

    For the behavior to change based on the line cycle you will need to do that in SW. there is a time during zero crossing that we do not have any switching and this may be safe to do then. We do something similar on the totem pole PFC code because the active switches are different.

    Seed TIDM-1007 code from the SDK

    switch(pwm_SwState.enum_pwmSwState)
    {

    ....

    case pwmSwState_positiveHalf:

    //AQCSFRC xA LOW, xB HIGH
    AQ_SW_FORCE_PWMxA_LOW_PWMxB_HIGH(LOW_FREQ_PWM_BASE);

    ...

    case pwmSwState_negativeHalf:

    //AQCSFRC xA HIGH, xB LOW
    AQ_SW_FORCE_PWMxA_HIGH_PWMxB_LOW(LOW_FREQ_PWM_BASE);

    ....

  • 0 in reply to Manish Bhardwaj
    Prodigy 40 points

    Hi, Manish

    Sorry, I comeback for this.

    But, I think there is no deadtime between the trip low PWMA and the trip high PWMB.

    Could we add a deadtime before turn on the flywheeling MOSFET? Though this is a minus issue, 

  • 0 in reply to Watermelon and Noodles
    TI__Mastermind 43730 points

    The Deadband unit is after AQSFRC so you should get deaband still.

    Also the AQ reg are shadowed and will only affect the next PWM cycle, if configured correctly. .