MPPT DC/DC Converter

[SyedAliHasnain]

Hi , I am doing a project on MPPT controller. I am using PIC micro controller to generate the PWM signal. Solar panel VOC 23V, Isc=8.5A, Vmp=17.5V and Imp=8A.
Trouble is dc-dc converter. I have tried making a buck boost and cuk. As soon as I switch on the power supply (which is being used in lab instead of solar panel) the supply becomes a current source and starts giving 5A (maximum it can). Output voltage remains almost zero. any idea where the problem may be? or any design ideas for dc/dc converter.
Attaching cuk converter design

 

[crutschow]

What's the purpose of C1 :?:

If the input goes to 5A then you have a short or Q2 is ON.

 

[SyedAliHasnain]

But Q2 is getting PWM on its gate! even on 20% duty cycle, it remains short. And well the design is from power electronics book! apparently C1 is charge in mode 1 and discharged to supply current to load part in C2!
if u can perhaps guide me to a simple buck boost design, that would be great

 

[SyedAliHasnain]

Ok so i made a simple Buck boost circuit! 1.7mH inductor, 220uF capacitor...Mosfet that i am using is IRFP150. The circuit is some what working....i cna control the output through duty cycle from NI Cdaq! the only issue is that the output is all wrong...it wont increase to more then 3.5v. maximum duty cycle it can take is 0.6, after that it starts drawing maximum current from the power supply and volatge levels drop! :/ any clue on how can i fix the output problem. I have 33ohm resistor at the output so i am guessing the current at the output is also less! Voltage across inductor is not more then 6V

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I also noted that the 50kHz signal i am giving at the gate gets highly distored! and gets a sawtooth kind of shape! can that be my only problem?

 

[crutschow]

If you have a sawtooth shaped waveform at the MOSFET gate then it's not being properly turned on and off. You need a gate driver capable of driving the high capacitance load provide by the gate. Not sure if that's your only problem.