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PMP41006: soft-start

Kien
Expert 3520 points
Part Number: PMP41006

Hi Champs,

I have a question about the soft-start routine. It was stated on page 9 of the SW guide that there are 2 modes at which the converter starts its turn-on. It can be VMC or PWM mode. So when at VMC mode, does this mean that there is a voltage controlled-oscillator to determine the turn-on and -off during start up?

Regards,

Kien Nguyen

  • 0
    TI__Genius 15555 points

    Hi Kien,

    I didn't fully get your question. what does voltage controlled-oscillator mean here? basically, it is the same as the normal voltage control mode(VMC) which the frequency is decided by the voltage loop. 

    Kien said:
    does this mean that there is a voltage controlled-oscillator to determine the turn-on and -off during start up?

    Regards,

    Chen

  • 0 in reply to Chen Jiang ti
    Prodigy 20 points

    Hi Chen, 

    Basically what you are trying to say is that during the start up, the PWM mode is first activated, which means that it is still at fixed frequency operation? And it is the duty that is controlled until it reaches a maximum duty value (is it 50% in this case?).  and then once it reaches a certain threshold, in this case the dead band threshold, it will already be direct frequency control for the remaining of the soft start time.

    Did I get it correctly?

  • 0 in reply to Jessica
    TI__Genius 15555 points

    Hi Jessica,

    Jessica said:
    Basically what you are trying to say is that during the start up, the PWM mode is first activated, which means that it is still at fixed frequency operation? And it is the duty that is controlled until it reaches a maximum duty value (is it 50% in this case?).  

    Yes, the freq is clamped to a max value. And yes, it is 50%. 

    Jessica said:
    and then once it reaches a certain threshold, in this case the dead band threshold, it will already be direct frequency control for the remaining of the soft start time.

    That is correct. 

    Regards,

    Chen

  • 0 in reply to Chen Jiang ti
    Prodigy 20 points

    Thanks Chen.

    During the PWM mode, am I correct to assume that it is the maximum frequency at which the soft start will begin with? 

    Regards, 

    Jessica