I have a few questions in my mind. I've searched alot but couldn't find a satisfactory answer. Kindly help me if anyone has knowledge about it. I am concerned regarding the feedback loops of the variable smps.
Consider I set the reference voltage at 2.5V, I get a 30% duty cycle on this and my output voltage is 5V. Now as the voltage drops to 3V due to load then the reference voltage at tl431 decreases to 2.3 suppose. Accordingly my pwm duty cycle insreases to 45% suppose. Now the voltage become 3V again. With a 3V set at the output my reference from output again gets to 2.5V. Accordingly the IC has to set the duty cycle back to 30% as set initially. This oscillations contioues.I have two basic ideas in my mind kindly add your points to them.
- if I consider that the controller IC always maintains a constant 2.5V reference and makes the error to zero as is done in an op amp then the problem can be solved as each time the voltage change, it will be brought back to 2.5V by increasing the duty cycle.
- secondly if I assume that the voltage at output changes according to the voltage reference of output/feedback pin voltage, then I would get the same problem discussed above ie oscillations even after I set up my output to 10V.Kindly tell me which approach is correct.
Kindly help me in these confusions as I could get a proper explanation on these anywhere.