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Can someone give me the simplest 120vdc 100mA power supply circuit

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Dzoro

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Can someone give me a schematic for the simplest ac to dc psu that can give from 110 to 130 v dc with 100 mA current.
I want to power some led strips
I have 3 led strips.One uses around 40v 30mA so i want them in series and thats about 120v 100mA and also i don't want to use transformer and i don't need a regulated one like some led drivers
 

dknguyen

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The simplest and safest thing would just to be find a 48V AC to DC wall adapter and use that.
 

dknguyen

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Oh, I misread your post. Frankly, I'm not sure you should be messing around with high voltage supplies if you're just starting out ESPECIALLY If you don't want to use a transformer.
 

Dzoro

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If you did, you would not have needed to ask your question.
I asked so i can build something simple and cheap whitout transformer and i didn't mean that i have knowlege how to build high voltage power suply i have knowlege how to handle high voltage
 

unclejed613

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40v 30mA so i want them in series and thats about 120v 100mA
you only need 30mA, currents in series don't add. currents only add in parallel strings.

EDIT: if you are trying to operate the LEDs direct off the line, you need to current limit your supply to 30mA. if you don't one LED shorting will cause a catastrophic failure of the whole string. so, in addition to a rectifier to get DC, you need something that can do current limiting. you could use a series resistor, but use a flameproof type, and calculate it's value to burn open at 40 to 50mA, or some type of dynamic current limiting, such as using FET current limiters.
 
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Dzoro

New Member
you only need 30mA, currents in series don't add. currents only add in parallel strings.
I know but i want to have more beacose i wabt 120 volts and if i don't supply enough current the voltage is going to drop and i don't want that
The current is not constant so the led diodes should use how much they need
 

Dzoro

New Member
I know but i want to have more beacose i wabt 120 volts and if i don't supply enough current the voltage is going to drop and i don't want that
The current is not constant so the led diodes should use how much they need
Sorry for my english i am from macedonia
 

gophert

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gophert

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Republic of macedonia
Republic of Macedonia? Where are the boarders of this yet-to-be-recognized country you call Republic of Macedonia? Does the Macedonia region of Greece fall inside or outside the boarder?
 

Dzoro

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It falls outside the border that is called egejska makedonija there is two more borders the bugarian that is called pirinska makedonija and the albanian border that is called tirinska makedonija but in those borders as i know macedonians do not live beacose the borders aren't in macedonia
 

unclejed613

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I know but i want to have more beacose i wabt 120 volts and if i don't supply enough current the voltage is going to drop and i don't want that
The current is not constant so the led diodes should use how much they need
with LEDs you don't want to exceed their current rating. LED junctions are not linear, and the change in forward voltage between 30mA and 100mA is very small. if you want to keep the LEDs working, you need some current limiting. to run your string of LEDs directly from the AC line, you need to use a rectifier to provide DC for the LEDs. this is because the maximum reverse voltage of an LED is usually around 5V, so you don't want reverse voltage applied to them. if you intend on filtering the DC feeding the LEDs, first of all, you will actually have about 150V available (full wave rectified DC is 1.414 x Vrms, and half wave rectified is 0.707 x Vrms). running a series string of LEDs at line voltage can be a dicey proposition. while i have seen LED strings powered "on the edge" (i.e. powered directly from a power source without current limiting where the total Vf of the LEDs is exactly the same as the supply voltage), i usually see it using a power supply with a regulated output voltage, and current limiting (in case something goes wrong). because power lines have occasional voltage surges, running LEDs "on the edge" from the AC line probably not a good idea. all it takes is one LED to short, and the increase in current through the string will begin a cascade of failing LEDs.

i'm not saying it won't work, just that it may not be the best solution. running LEDs "on the edge" is a fine balancing act that works fine with proper current and voltage regulation, but could be a disaster running directly off the raw AC line.
 
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