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LED power consumption how to decrease it

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dr.power

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Hello guys,

Just wondering is it possible to decrease the power consumption of a LED or an array of LEDs all connected together in parallel and supplied by 3V DC without any significant loss in the light intensity/brightness of them?

thanks
 
Last edited:
Use a switching LED driver.
 
Hi,


The only way to decrease power consumption in LEDs without affecting the light output is to find LEDs that are more efficient. That is, they put out more light per amp, and/or they have a lower terminal voltage. Either way you get the same light output with less power consumed in the LED itself.

The power consumption of the LED is not the only issue however because sometimes the LEDs are driven from a resistive source. The resistive part of the source dissipates power too so you loose power just because of the way it is being driven. So the idea then is to reduce the resistive part of the driver. This is usually done with a switching voltage regulator set up as a current feedback regulator. This usually (but not always) provides higher efficiency in the overall system. I said usually because this isnt always the case. If the voltage source voltage level is close to the voltage of the LED or LED string, then there may be little or nothing to gain by using a switching regulator. In fact, there are times when using a switcher will actually reduce overall efficiency and this is when the source voltage is already pretty well matched to the LED voltage.

So the first thing to do is analyze the system to see what category your circuit falls under and take the appropriate action. It usually helps to find the most efficient LEDs first unless the lower forward voltage then provides a mismatch between source and LED characteristic voltage.

It almost always helps to run the LED at reduced current too. The efficiency goes up if you run it at 1/2 the nominal rated current, so running two LEDs at the same current as one LED effectively produces more light. The effect isnt super significant however so you may want to do a couple of tests with your actual LEDs to see if it warrants doubling the number of LEDs for a small gain in light output. Another benefit however is very significantly increasing the life of the LED.
 
Hello guys,

Just wondering is it possible to decrease the power consumption of a LED or an array of LEDs all connected together in parallel and supplied by 3V DC without any significant loss in the light intensity/brightness of them?

thanks

Hi dr.power,

How about driving them with AC volatge instead DC, making them to blink at high rate frequencies? for instance at 100Hz, or 1kHz and see what comes up about the power consuming and brightness? Our eyes are not sensitive against such blinks at those frequencies as I know.
 
The power used by an electrical device is calculated by its voltage times its current. An LED sets its own voltage so you cannot change it but your circuit sets its current that you can change. Less current reduces the power that is used.
BUT the brightness of an LED is determined by its average current. Less current produces less brightness.

A switching LED driver reduces the average current then it also reduces the brightness.

A 2V red LED will draw a very high current and instantly burn out if you supply it with 3V. A current-limiting resistor is needed in series with each LED.
I have a CR2032 3V battery cell that is nearly dead (2.882V with no load) and it dimly lights a 2V red LED because its internal resistance is high. A new CR2032 cell might not be able to provide enough current to burn out a 2V red LED.
 
Just like sound to your ears, light sensitivity of your eyes is not linear. A significant decrease in current to the LED will only seem slightly dimmer.
 
Hi,


The only way to decrease power consumption in LEDs without affecting the light output is to find LEDs that are more efficient. That is, they put out more light per amp, and/or they have a lower terminal voltage. Either way you get the same light output with less power consumed in the LED itself.

The power consumption of the LED is not the only issue however because sometimes the LEDs are driven from a resistive source. The resistive part of the source dissipates power too so you loose power just because of the way it is being driven. So the idea then is to reduce the resistive part of the driver. This is usually done with a switching voltage regulator set up as a current feedback regulator. This usually (but not always) provides higher efficiency in the overall system. I said usually because this isnt always the case. If the voltage source voltage level is close to the voltage of the LED or LED string, then there may be little or nothing to gain by using a switching regulator. In fact, there are times when using a switcher will actually reduce overall efficiency and this is when the source voltage is already pretty well matched to the LED voltage.

So the first thing to do is analyze the system to see what category your circuit falls under and take the appropriate action. It usually helps to find the most efficient LEDs first unless the lower forward voltage then provides a mismatch between source and LED characteristic voltage.

It almost always helps to run the LED at reduced current too. The efficiency goes up if you run it at 1/2 the nominal rated current, so running two LEDs at the same current as one LED effectively produces more light. The effect isnt super significant however so you may want to do a couple of tests with your actual LEDs to see if it warrants doubling the number of LEDs for a small gain in light output. Another benefit however is very significantly increasing the life of the LED.

Thanks,

Yea, I know what you are meaning about the LED exchange and the Resistive action of the source.

I would like to make a test with my LEDs and then try to make something like this:
https://petapixel.com/2012/08/28/up...t-paintings-with-this-diy-500-led-flashlight/
So lowering the power consumption is very important to me.
 
Hi dr.power,

How about driving them with AC volatge instead DC, making them to blink at high rate frequencies? for instance at 100Hz, or 1kHz and see what comes up about the power consuming and brightness? Our eyes are not sensitive against such blinks at those frequencies as I know.

Oh, very good idea if possible?
Is it really possible to do so? just like florecent tube that works by AC and the blinks are not affective so much...
 
A switching LED driver reduces the average current then it also reduces the brightness.

Switching LED driver eliminates the need for current limiting resistor. The average current can stay the same. Switching regulator is more efficient than linear regulator.
 
Switching LED driver eliminates the need for current limiting resistor. The average current can stay the same. Switching regulator is more efficient than linear regulator.
That's only true if you replace the resistor with an inductor.
 
Why not simply switch banks of LED's to alter brightness, as he does in the article.

I want to decrease the AMP-draw for a constant amount of LED's, So It does not help me if just try to just switch.....

Is it really possible to do so by what Wizard is telling?
 
Switching LED driver eliminates the need for current limiting resistor. The average current can stay the same. Switching regulator is more efficient than linear regulator.

What are Switching LED drivers really? is the output of them DC or AC?
 
A switching LED driver turns on the LED very brightly for a moment then turns it off for a moment over and over so the average current is enough to produce fairly bright visiblity. It turns on and off so quickly that you see no flickering unless it moves.
When the driver turns on then its voltage drop is low so it wastes very low power. When the driver is off then it wastes no power.

A current-limiting resistor wastes power ALL THE TIME.
 
I want to decrease the AMP-draw for a constant amount of LED's, So It does not help me if just try to just switch.....

Switching LED's in and out alters brightness and current consumption, which is what you're wanting to do - and is what most commercial lights do (it's simple, cheap, and effective). Altering the PWM ratio (if using PWM) will provide the same effect, but in a much more complex way).
 
Hello,


I second that idea. If you have a lot of LEDs, why not turn some off for lower power. It's the simplest way to do it and it works pretty well if you only need a few set brightness/power levels.
 
A switching LED driver turns on the LED very brightly for a moment then turns it off for a moment over and over so the average current is enough to produce fairly bright visiblity. It turns on and off so quickly that you see no flickering unless it moves.
When the driver turns on then its voltage drop is low so it wastes very low power. When the driver is off then it wastes no power.

A current-limiting resistor wastes power ALL THE TIME.

So you mean, that a switching LED driver is kind of step dwon system that is used instead of current-limiting resistor? If so it acts in the circuits having a higher power supply than so needed for the LEds
Are you talking about these:

http://www.fasttech.com/product/1110712-220v-3x1w-high-power-constant-current-led-driver

**broken link removed**

**broken link removed**
 
Switching LED's in and out alters brightness and current consumption, which is what you're wanting to do - and is what most commercial lights do (it's simple, cheap, and effective). Altering the PWM ratio (if using PWM) will provide the same effect, but in a much more complex way).

Really I want to MAINTAIN the brightness yet decrase the electric power needed for them, So sorry I am not able to understand you correctly Nigel.

What actually a PWM system does in such LED's?
 
Hello,


I second that idea. If you have a lot of LEDs, why not turn some off for lower power. It's the simplest way to do it and it works pretty well if you only need a few set brightness/power levels.

Because I want to see if there is any alternative to decrase the power draw yet MAINTAIN the brightness of the whole leds. For ibstance is it possible to do so by using a high frequency circuit connected to the LEDs so that the LEDs not be turned on all the time? by doing so maybe I could maintain the brightness for lower electric power consumption of the system (because our eyes is not able to detects the fast reated swings of the light yet The power supply is not working ALL the time so the power consumption should be decreased, Right?)
 
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