non-inverting buck boost converter

[Ahmed Kh]

In boost mode the output power is stored in the L during the time the second FET is on, so value of L?, value of I?
Frank

the output of ( current and the voltage ) always change that is depend on the R load
the value of L is 170uH AND I ALSO CHANGED the L BUT still the SAME PROLEM
MAYBE I MUST USE PID FEEDBACK ?
MY REGARDS

 

[FvM]

Maybe I must use PID feedback?

Yes. Your circuit topology changes it's operation mode from continuous conducting (CCM) to discontinuous (DCM) below a certain load level. In DCM the output voltage is directly load dependant (both for buck and boost operation) and must be stabilized with a feedback controller. Also in CCM, the output voltage varies due to diode and transistor voltage drops, but the stability might be sufficient for very basic applications.

 

[Ahmed Kh]

Thanks for replay
so please what type of feedback i have to use(PID or anther type )
i need the satiable one for my circuit ( four switch non-inverting buck boost converter)
my best regards ..

 

[BradtheRad]

A buck converter is a simple way to demonstrate how feedback works.

20V is dropped to 12V. The output is regulated at 12V, any current. (The simulation has a load of 1A.)

The feedback signal acts to regulate output, by causing the op amp to turn on and off when output strays too high or low.