Hi all,
I'm using the TL431 in a Flyback DC DC converter. The topology of the DC DC converter is similar to that shown in this article (and many other articles). Basically the TL431 internal reference (+2.5V) is compared to one of the DC DC converter's output (+5.3V in this case) and the difference is converted into a current. I have a doubt on how to set the resistive divider conerting the +5.3V output voltage into a voltage close to the TL431 internal reference. Based on my understanding, if i set the resistive divider so that +5.3V is converted to +2.5V, the TL431 will switch on and off depending if the +5.3V output is below or above +5.3V. Also, the TL431 datasheet states the following:
"Slow or inaccurate responses can also occur when the reference pin is not provided enough overdrive voltage. This is the amount of voltage that is higher than the internal virtual reference. The internal virtual reference voltage will be within the range of 2.5 V ±(0.5%, 1.0% or 1.5%) depending on which version is being used. The more overdrive voltage provided, the faster the TL431 will respond. For applications where TL431 is being used as a comparator, it is best to set the trip point to greater than the positive expected error (i.e. +1.0% for the A version). For fast response, setting the trip point to >10% of the internal VREF should suffice."
Does it mean that, for proper operation, the resistive divider shall be designed so that for a +5.3V output, the resulting voltage on the reference pin is slightly higher than +5.3V?
Thanks in advance for your feedback
Best regards
Frederic
