LED Brightness Control

What kind of help? Do you mean do it for you? Tell you what to do?

What have you done? What are you going to do next? Why do you need help?

Could you describe in detail what you need? And What's kind of function you want ? 

How conincidental, I had to design a IR remote control to change the brightness of an LED for my university project last year at exactly this time.

You may need a current source, please take a look at this website (Fig.3).

http://en.wikipedia.org/wiki/Current_source

In addition, you need a DAC output to control the power level of Vin.  

Sunglin Chen said:

You may need a current source, please take a look at this website (Fig.3).

http://en.wikipedia.org/wiki/Current_source

In addition, you need a DAC output to control the power level of Vin.  

To control brightness of the LED you don't need current source nor DAC. You can use timer in PWM mode.

PWM is a good choice for LED brightness control.  For the high power LED, the fan out of microcontroller or chip is not enough to drive it.  Do you have any idea for this case?  Thank you.

But make sure the PWM frequency is far away form the sub-carrier frequency used in your IR remote control.

Sunglin Chen said:

 For the high power LED, the fan out of microcontroller or chip is not enough to drive it.  Do you have any idea for this case?

Bipolar or MOSFET transistor as LED driver.

Hello.....could you please tell me your project in detail description?....email : kmdineshece@Gmail.com 

Basically I am a embedded programmer and I am new to circuit design.....   I want to know about led brightness control technology.... 

Yes...I have planned to use mosfet 

It depends on the specific LED you are using. If it needs less then 20 mA and the voltage drop across it is less than 2V,  you can use PWM from a MSP430 Timer directly with a current limiting resistor.

Some LED may need as much as 350 mA.  And may have voltage drop above 3V (temperature dependent). They are used in light-bubs (post 2013). Are you thinking of remote controlled light dimmers? If so, you need to understand the  build-in circuit in the light-bubs.

dineshkumar mani said:

I want to know about led brightness control technology.... 

The drawbacks are:
1) light output and current are not a linear function 
2) on lower current, even the color may change.
3) voltage/current regulation usually causes energy waste and heat generation in the regulation circuit.

The alternative method is to drive the LED full current all the time but vary the time it is on, on high speed. this is what PWM means: pulse-width-modulation. 0% duty cycle mans pulse duration zero (LED off) and 100% DC means pulse duration 100% of a cycle period (LED maximum light). Between the two, you can vary the time the LED is on and off. The advantage is that you don't waste energy in the regulator circuit. Either the switch is on, then the LED consumes the current, turning it into light, or the switch is off, then no current flows and no energy is wasted. The slowness of human eye perception makes the LED appear dim or bright rather than flickering (assuming a short enough cycle time).

The drawback is that you may experience a 'stroboscope effect' when you quickly move your eyes: the LED is no 'moving' but rather seems to 'jump'. On RGB video projectors, this effect is also called 'rainbow effect' because the R, G and B parts of an image are on at different times, so when you turn your head, they seem to 'jump' to different places.
However, this is the usual way to do high-current LED brightness control these days. (also motor speed control and many other things)