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Half-Bridge 0-30V, 0-20A Feedback loop problem
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paladyn:
Hi everyone
After long break i would like to resurrect topic.
I changed LC filter to 300uH inductor and total capacity 9000uF plus common mode choke. Also i bought Analog Discovery 2 to measure bode plot.

Quick recap:
Topology - Half Bridge
PWM Controller - SG3525
Mosfet Drivers - HCPL3120
Transistors - IRFP460
Rectifer - 4 x 60CPQ150
Voltage after diodes on max PWM - 43V
Target output voltage 0-30V (regulated)
Feedback OP-AMP - TL3474C
Used compensators - Type 2 , or Type 3
Load = about 1ohm

LC_Filter schematic


I have charts bode plot with out compensator, and few charts for compensator type 2 and type 3. Can you evaluate where put zero and pole looking to uncompensated chart. Also i would ask you to evaluate attached charts for compensator type 2 and type 3.

Feedback loop uncompensated Output = 5V


Feedback loop uncompensated Output = 12V



Type 2 compensator Output = 5V


Type 2 compensator Output = 12V


I have hope that toogether we will resolve feedback loop compensation problem, and acquired knowledge will be usefull for others designers

paladyn:
Type 3 compensator VOUT = 5V

Type 3 compensator VOUT = 12V


T3sl4co1l:
I suppose it's too late to recommend an average current mode control...

The CMC in the filter by the way, can't possibly do anything if it's shorted between GND and GND; indeed if the circuit is common ground, the solution is easier because common mode noise can be controlled by layout alone.

Tim
paladyn:
Sorry, I made mistake during drowing schematic. I will correct atachment above

T3sl4co1l
can you tell more about average current mode control. Why is it better ?
David Hess:
Sometimes I am amazed that anybody gets a voltage mode variable input or output switching regulator to work.
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