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Original question:

TIDA-00779: tida-00779

TIDA-00443: what should be the correct Vsense voltage in boost follower mode

Lenin Prakash
Intellectual 660 points
Part Number: TIDA-00443
Other Parts Discussed in Thread: UCC28180

Hi

  We have made a proto based on TIDA-00443, In this design the Vsense equals 4.99 V for a output voltage of 391 V. 

What shd be the Vsense value in the boost follower mode. I guess it shd be equal to 5 V for a o/p voltage ranging from 290 V to 390 V.

Then only it could maintain a varying  o/p voltage for different value of i/p AC

We were just checking the Vsense value by disabling the controller. (Just varying the I/P AC voltage and measuring the o/p voltage and Vsense value)

we noticed that the Vsense was varying ( not constant as we expected) and it was around 4.5 V for a output of 390 V DC. Is this correct ?

What shd be the correct value of Vsense for a o/p voltage of 290 ~ 390 V DC in boost followe r mode ?

Thanks

Lenin.

  • 0
    TI__Intellectual 950 points

    Hi Lenin,

    Thanks for your reaching out, for UCC28180, the pin of Vsense, we have a internal Voltage Error Amplifier, the ref is 5V, so at any situation, the voltage you test at this pin should be 5V, it no matter with fixed output or boost follower output, thanks.

    BR

    Jason

  • 0 in reply to Yuan Tao
    Intellectual 660 points

    Hi Jason

      Thanks for the response. Pls clarify the below.

    In the fixed o/p control mode, Vsense is 5 V for 391 V, (Vo=  391V --> Vsense = 5 V)

    what is the actual value of output ( or range) for which Vsense is 5 V in the boost follower mode. ( Vo = ? --> Vsense = 5V)

    We would like to know this to test the boost follower circuit before actually powering up in this mode. The proto perfectly works with

    constant o/p voltage mode.

    Thanks

    Lenin.

  • 0
    Prodigy 10 points
    Hi Lenin,
    Thanks for your reaching out. As long as the converter works properly, whether in the boost follower mode, the vsense pin should be 5V.
    In the boost follower mode,although Vsense is always 5V， the larger the input voltage, the larger current ie of transistor is and greater the Vout can be controlled.
  • 0 in reply to Lenin Prakash
    TI__Prodigy 110 points

    Hi Lenin,

    Thanks for your reaching out. As long as the converter works properly, whether in the boost follower mode, the vsense pin should be 5V.

    In the boost follower mode,although Vsense is always 5V， the larger the input voltage, the larger current ie of transistor is and greater the Vout can be controlled.

    thanks.