I am making an LED driver circuit which will drive 2 strings of LEDs connected in parallel.

Each string has 4 LEDs in series.

Specification of each LED is 2.2V, 20mA.

This means the supply that i need to give to the driver should be 8.8V or say 9V and 40mA.

My original supply is directly from car battery which gives a spike of 9V-16V. If i introduce an led driver directly to this supply it will burn.

So i need to stabilize this spike to say 9V and this 9V now will be the supply for my LED driver. With this 9V i will attach a current limiter.

Now i want to know how will this voltage regulation take place meaning the circuit that i need to make or is there any IC available.

 

use an On-Semi device like the 20mA constant current driver NSI45020W. Small Cheap, and does exactly what you want to do. Because it's a constant current device, any variation in voltage, as you say from a car pwer supply, will have no effect on the brightness of your LED. (Easily used with a PWM dimming circuit too.)
Rgds Jeff

 

but the current is 20mA and the circuit needs 40mA

 

you can use a 7809 voltage regulator IC. It will maintain 9V across your circuit even if your supply increases.

 

ok.
so i will need to drop 0.2V.
how will i limit the current? a resistor would be sufficient or any ic is required.

 

I am making an LED driver circuit which will drive 2 strings of LEDs connected in parallel.

Each string has 4 LEDs in series.

Specification of each LED is 2.2V, 20mA.

This means the supply that i need to give to the driver should be 8.8V or say 9V and 40mA.

My original supply is directly from car battery which gives a spike of 9V-16V. If i introduce an led driver directly to this supply it will burn.

So i need to stabilize this spike to say 9V and this 9V now will be the supply for my LED driver. With this 9V i will attach a current limiter.

Now i want to know how will this voltage regulation take place meaning the circuit that i need to make or is there any IC available.

Actually this is incorrect. Any regulator circuit, be it voltage or current, will work to prevent this. My favorite is a LM317T current regulator

There are many schemes that will work.

Have you read this article? It covers the basics in chapters 1 and 2.

LEDs, 555s, Flashers, and Light Chasers