How to properly PWM a large LED array?

[gday56]

PWM Large LED Array

Hello,

I'm building a light source out of LEDs and was wondering what the best way of going about a power supply would be. The LEDs need to be able to dim, but when they do so must stay the same color. So, varying the supplied current isn't an option.

I think the best option is to PWM the power supply to vary the intensity of the LEDs. This seems like a decent option (the number and length of LED strings is different), but I think linear regulators are kind of slow and I fear the LEDs' flickering might be noticeable. Is there anyway to be able to PWM the LEDs more quickly in order to avoid the flickering? I thought maybe a switching regulator, but I'm not sure how to go about building one and inductors are hard to come by where I am.

Any ideas or suggestions? Any help will be appreciated.

Thanks!
Chris

 

[~E3016~]

Re: PWM Large LED Array

it's the same thing, PWM is of course will vary the input current. and it's the way for you, indeed. do you know about switching devices? one example is transistor, using this transistor you can either turn on or off the current path, so the pwm can be done. as for the duty cycle you can use the timer which can be controlled, try read about 555, or if you familiar with microcontroller, it can be the choice too...

regards...

 

[Siniša]

Re: PWM Large LED Array

What is large array? Are they connected serially?

You current regulator, being either switching or linear can operate normally as it was and you can apply bypass transistor with PWM drive to regulate on/off time. Your current should maintain required current level.
Another way is if PWM switching transistor can work as current limiter as well, but then you won't be able to implement switching current regulator and efficiency would be low. PWM frequency can be as high as your LED's speed will allow.

 

[FvM]

Re: PWM Large LED Array

Manufacturers are suggesting PWM frequencies around 1 kHz to dim LED without wavelength shift and to operate LED arrays near the grouping current (the current used to select LED of equal intensity during assembly) to achieve uniform intensity.