Creating 9v-12V 1000mA or higher rating of Adapter Circuit

[lloydi12345]

Hi I would like to ask if you guys have any schematic that could produce 9v to 12v that has a current rating of at least 1A. I'm connecting them to the AC line directly. I prefer to use a switching type of circuit to have the smallest circuit and components to use. I already thought of using transformer to be connected to the AC line but it seems to be bulky so I'm looking for a simpler and smaller design. I would like to power several strings of leds to make a small version of fluorescent tube.

I found this one https://bbs.dianyuan.com/bbs/u/30/1118463481.pdf but the components are not available locally and it outputs a low voltage of 5V. I prefer using 9V circuit or above.

Any suggestion or comment will be so much of help. Hoping for your usual assistance. :smile:

Cheers,

lloyd

 

[goldsmith]

Dear lloydi12345
Hello
You should try boost converters , for example this IC: LM2577 it's out put will be DC that is higher than input with your desired value .View attachment lm2577.pdf
But if you want AC , what is your desired frequency?
Best Wishes
Goldsmith

 

[lloydi12345]

Dear lloydi12345
Hello
You should try boost converters , for example this IC: LM2577 it's out put will be DC that is higher than input with your desired value .View attachment 68888
But if you want AC , what is your desired frequency?
Best Wishes
Goldsmith

Hi Goldsmith, well LM2577 is not also available on our place. I wanted to use the AC line for the fluorescent lights. I'm creating a smaller tube and LEDs on it like a hundred of 5mm super bright LEDs. Our AC line sockets are 60Hz. I have opened several adapters and chargers and they give a current of 1A. They have 2 small transformers inside but I guess the process involved is switching.

 

[goldsmith]

Yes those are switching and normally are at fly back or forward arrangement . so where are you from ? i think this IC is not very critical and new thing ? . so , do you have SG3526 in you r country ? or UC3844 ?
Good luck
Goldsmith

 

[lloydi12345]

Yes those are switching and normally are at fly back or forward arrangement . so where are you from ? i think this IC is not very critical and new thing ? . so , do you have SG3526 in you r country ? or UC3844 ?
Good luck
Goldsmith

I'm from Philippines. Unfortunately those ICs aren't available. Anything else? :???:

 

[BradtheRad]

It is feasible to use a capacitor to drop mains AC. It avoids using resistance which generates wasteful heat. Instead it uses reactance.

Sample link:



Better suited for low current loads. And there's the risk of component failure which could expose your devices to mains voltage.

 

[lloydi12345]

Hello BradtheRad, that's one option I have in mind also but I can't juice out a current as high as 1A from that kind of setup. I tried to use this setup

but I can only get a maximum current of 100mA. Will it help if I increase the capacitance?

 

[BradtheRad]

Hello BradtheRad, that's one option I have in mind also but I can't juice out a current as high as 1A from that kind of setup. I tried to use this setup

but I can only get a maximum current of 100mA. Will it help if I increase the capacitance?

If you combine the led's into 2 strings (and only 2 strings), the total draw will be less than 20mA. Per this schematic:

If you wish you can add dozens of led's to the two strings, and can reach over 120V forward voltage threshold in each direction.

 

[lloydi12345]

If you combine the led's into 2 strings (and only 2 strings), the total draw will be less than 20mA. Per this schematic:

If you wish you can add dozens of led's to the two strings, and can reach over 120V forward voltage threshold in each direction.

Very thank you for the circuit Brad theRad but my objective for the design is to have parallel leds so that when one led goes down I won't have a hard time on finding the broken LED and I could replace it easily. If I'll be using this kind of setup for parallel LEDs like for 1 string I have 2 LEDs only and I might be making 50 parallel strings will it work?

What do you mean with 20mA? Is that the current for one led alone?

 

[goldsmith]

As i understood from Post #8 , his , mean is that , the all of the LED 's will be less than 20 ma . and it is certainly correct. and it is the advantage of his circuit .
Good luck
Goldsmith

 

[lloydi12345]

Hi, I tried the circuit above but as I increase the number of strings the current on each string decreases too. I used 0.1uF Cap and 1K 2W resistor. The total current only is 150mA.

Help pls?

 

[goldsmith]

Hello Dear lloydi
DO you know how is the correct calculation of top circuit ? it's calculation is good , but for that number of LED 's . if you want increase the number of LED's , all thing will change . so you should make choice , that : you can increase the number of series LED's or you can increase the number of parallels ( complex ) . or both of them ?! so what is your prediction ?
Best Wishes
Goldsmith

 

[BradtheRad]

Yes the total draw of my schematic is under 20mA. Start with a very low value capacitor. Move up to higher values while checking current draw.

Very thank you for the circuit Brad theRad but my objective for the design is to have parallel leds so that when one led goes down I won't have a hard time on finding the broken LED and I could replace it easily. If I'll be using this kind of setup for parallel LEDs like for 1 string I have 2 LEDs only and I might be making 50 parallel strings will it work?

It will work, however some led's may have a slightly different forward voltage threshold. If there's one with a slightly low value, it will hog current and likely fry. Any led with a high value will not light.

As for how to get 1A through the capacitive-drop technique...

You will need to use a bigger capacitor value. And reduce the series resistor value. It means the capacitor will have at least 1A going through it continuously (average). It may blow the capacitor. Even though we don't usually see capacitors having a current rating.

If the capacitor were to short internally, all your led's would be exposed to high voltage.

This is a case where you might as well consider using a transformer. 9 VAC at 1 or 2 amps.

There was a time when transformers were less expensive. It was all but assumed that a transformer would be used in powering a hobby project from house current. They isolate our project from high voltage.