Then you need to run your switching regulator sim with an input that is both current and voltage limited.

 

Then you need to run your switching regulator sim with an input that is both current and voltage limited.

How can I set the current in the Orcad in properties or something ?

 

You can make a current limiter by adding a diode across a current source (anode to plus side).
If you place that in series with a voltage source it will limit the current to the value of the current source.
Below the current limit the diode shunts the excess current around the current source.
The only limitation of that technique is the voltage across the current source of one diode-drop when it is below the current-limit point.
A large Schottky diode will minimize that.

 

I tried to find some Buck Converter IC that doesn't need any Microcontroller to control it

I found a LM2825 here

Can I use this IC instead of a normal circuit ? or is there any other IC work like Buck Converter ?

 

I tried to find some Buck Converter IC that doesn't need any Microcontroller to control it

I found a LM2825 here

Can I use this IC instead of a normal circuit ? or is there any other IC work like Buck Converter ?

I have forgotten what you are trying to do? Solar panel to what battery?

 

I have forgotten what you are trying to do? Solar panel to what battery?

Solar Panel to charge Ni-Cd Battery by using Buck Converter

 

NiCd charging requires constant-current, and then time to cut-off the charger. Constant-voltage is the wrong way to control charging of a NiCad (your professor is wrong!)
If you must use a microcontroller for your school project, then use it to integrate the charging current over time ∫Idt, and then terminate the charging process when battery capacity is passed.

How many cells in the NiCd pack?

 

NiCd charging requires constant-current, and then time to cut-off the charger. Constant-voltage is the wrong way to control charging of a NiCad (your professor is wrong!)
If you must use a microcontroller for your school project, then use it to integrate the charging current over time ∫Idt, and then terminate the charging process when battery capacity is passed.

How many cells in the NiCd pack?

6 cells, maybe because my professor doesn't know that I pick Ni-Cd Battery so he gave me a topic about Buck Converter

But he said that I can control Buck to Constant Current by using a feedback back to Micro to control it (Controlling Duty Cycle for Constant Current)

 

If your going to use a buck down converter,use a Lm2596.

http://www.onsemi.com/pub_link/Collateral/LM2596-D.PDF

less than a 1$ bill
http://m.ebay.com/sch/i.html?_nkw=lm2596&_pgn=1&_sacat=261&_back=1&_sop=15

 

If your going to use a buck down converter,use a Lm2596.

http://www.onsemi.com/pub_link/Collateral/LM2596-D.PDF

less than a 1$ bill
http://m.ebay.com/sch/i.html?_nkw=lm2596&_pgn=1&_sacat=261&_back=1&_sop=15

Thx, Is there any example circuit using this IC to charge battery ?

 

If your going to use a buck down converter,use a Lm2596.
http://www.onsemi.com/pub_link/Collateral/LM2596-D.PDF

All of the applications shown on that data sheet are fixed voltage output converts; the OP needs a constant-current converter.

 

Since your are charging 6 cells, and 6 cells have an approximate voltage of 1.4V per cell during charge, then the voltage of the pack will be 6*1.4 = 8.4V. Since your panel puts out up to 18V, you do not need anything but a timer. The cells will take all of the current that the panel can make, so no current-limiter is needed.

Connect the panel directly to the battery pack. The voltage and current will take care of itself. Disconnect the panel when the battery is fully charged.