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need help building a power supply

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jason 77

New Member
Hello everyone.......

I need some help in building a power supply for some led lights I am making. I need to figure out a easy way of getting say 60-70 volts DC from the 120 volts AC off the mains. Size is kind of a issue, so I was hoping to be able to do it without a step down transformer.

The LED lights are not going to take more than about 40-50 Ma each, and there will be a set of 3 LED lights. I have a full wave bridge rectifier and a Cap which gives me 169VDC unloaded. I am kinda stumped as how to get it down to 60-70VDC.

Can someone please help me out?

Thanks in advance
 

Sceadwian

Banned
Why not use the right number of LED's to be able to run them off 120 volts directly? Makes a lot more sense that stepping the voltage down.
 

Hero999

Banned
You need constant current not constant voltage to power LEDs.

They're plenty of ICs than enable you to power LEDs directly from the mains.
 

jason 77

New Member
Why not use the right number of LED's to be able to run them off 120 volts directly? Makes a lot more sense that stepping the voltage down.
The lights I am putting these in don't have room for that many led's, also I really don't want to buy that many LEDs......

You need constant current not constant voltage to power LEDs.

They're plenty of ICs than enable you to power LEDs directly from the mains.
Could you possibly give me an example of one of these IC's? Would it be something like this?

http://www.electro-bay.com/LED_Driver/datesheet/HA220XXPB%20ED.pdf

If so I am unable to understand the formula they use for figuring out the number of LEDs?
 

Sceadwian

Banned
I boughtt a pack of bright white LED's the I directly connected to mains power. Cost less than 10 dollars.
 

jason 77

New Member
I boughtt a pack of bright white LED's the I directly connected to mains power. Cost less than 10 dollars.
The superflux LEDs I am using cost more than $10 for 100..

I am really interested in the IC's mentioned above that can use 120v as a input, and provide a constant current output to the LED arrays. Can someone provide me with more information on these?

Thank you! :D
 

ronsimpson

Well-Known Member
Most Helpful Member
Jason#77,

>The IC you chose is designed for driving many LEDs. It needs a minimum of 30 volts of LEDs and should have 90 volts of LEDs. (or more)
>You say you want to drive 3 LEDs. I do not know what type so...maybe 6 to 9 volts of LEDs.
>The IC will take 120v and make 60-70 volts like you said but that 70 volts will not work with only 3 LEDs.
>How big...How much area do you have to put all the parts into?
 

jason 77

New Member
Jason#77,

>The IC you chose is designed for driving many LEDs. It needs a minimum of 30 volts of LEDs and should have 90 volts of LEDs. (or more)
>You say you want to drive 3 LEDs. I do not know what type so...maybe 6 to 9 volts of LEDs.
>The IC will take 120v and make 60-70 volts like you said but that 70 volts will not work with only 3 LEDs.
>How big...How much area do you have to put all the parts into?
Sorry, I think I was a bit vague..

I want to drive 3 "sets" of leds, each "set" has 40-60 leds in series each. The leds are 3.4Vf and 20-30 mA each....

each "set" could be either all in series or in smaller series then connected in parallel depending of the maximum output voltage of these IC chips that were mentioned above.
 

Sceadwian

Banned
How much did you pay for your LEDs jason? Mine are 3.4Vf and 20ma as well. 15000MCD.
 

jason 77

New Member
Jason,
The data sheet is OK. Just build one of the examples.
There is more information like:
HA220P???????????LED?????? - ????? - MySpace?? - ?????????????
Much of the data may be hard to read.
Ok so besides that IC I found, can you recommend any other IC's?

I had a constant current circuit already, using discrete componets that I was using. But the transistors I have are only good for 80v. So these IC's that take in 120VAC and can run the led's using constant current are very appealing to me! :D

How much did you pay for your LEDs jason? Mine are 3.4Vf and 20ma as well. 15000MCD.
I paid about $18 USD for 50 superflux warm white leds, I got them from ebay from seller "phenoptix"
 
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