Design of switchmode regulator (Buck regulator)

[fantabulous68]

Specifications:

input voltage=[10v-30v]

output voltage=5V
output current=[0.5A-1A]

I just want to know if the design is reasonable (see attached picture) & will work. Im going to build it soon.

 

[crutschow]

From a quick look it appears the circuit will functionally work.

But you will need compensation in the error amp for stability. The output filter L1 and C4 form a resonant tank circuit that causes a large phase shift in the feedback. Without compensation, this phase shift will cause positive feedback and oscillation near the resonant frequency.

See the following attachment for info on how to calculate the proper compensation values.
View attachment Designing Stable .pdf

 

[indulis]

If you make it current mode control, you will have an easier time with the loop. The double pole from the LC goes away and you can use simple type 1 compensation.

 

[AbsoluteCPP]

I think you must give a look to LM2576HV Series SIMPLE SWITCHER 3A Step-Down Voltage Regulator.

 

[crutschow]

If you make it current mode control, you will have an easier time with the loop. The double pole from the LC goes away and you can use simple type 1 compensation.

That is true. But then you need to add a current sensor in the switching circuit such as a current transformer, or another winding on the inductor. So the tradeoff is one complexity for another.

 

[indulis]

Yes, but supplies should have a "current limit circuit" anyway...