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UCC28056: Cancel for UCC28056

Yuki Saito
Intellectual 970 points
Part Number: UCC28056
Other Parts Discussed in Thread: UCC28064A, , UCC28064

Hi Application team 

I get question below customer.

Could you give me answer?

The instantaneous instantaneous drop test is specified by the safety standards and is a test to see how the monitor behaves when the input AC voltage is momentarily reduced.
The test includes 100%, 60%, and 30% reduction of the input AC voltage rating, with different drop times.


When the input AC voltage drops, the PFC output voltage also drops. Therefore, medical monitors use ICs with a function to minimize the drop in PFC output voltage.
The names of the PFC IC's in use are as follows
R2A20133D (manufactured by RENESAS) - Dynamic Undervoltage Protection Function (D-UVP)
R2A201112A (manufactured by RENESAS) ・ PFC output voltage drop protection (D-UVP)
Both of these functions detect a drop in feedback voltage and increase the maximum ON range for driving the FETs to twice the steady-state level.
By doubling the maximum ON range, the drop in PFC output voltage is slowed down.

if you have a method of providing equivalent functions for your current UCC28056 and UCC28064A ICs with an external circuit, etc., please let us know.

Thanks 

  • 0
    TI__Prodigy 590 points

    Hello,

    Your thread has been assigned. You should be receiving a reply shortly.

  • 0 in reply to Pye Naing
    TI__Genius 9140 points

    Hello,

    thanks for your interest in these PFC controllers.

    For UCC28056, Since it has Max on time limited at 12.8uS, I suppose there is no way to realise the function you need.

    For UCC28064 or UCC28064A, because the controller detects the Vinac directly, so during the drop test, there should be a change on the sampling of Vinac.

    You can try to use this signal to change the Rtset in order to change to change the max on time.One concern is you need to take care of PFC inductor to make sure at this conditon it won't be saturated at this condition.