SMPS designing 12v/2amp

I want to develop 12v/2a SMPS without transformer.Input of smps will be between 90 to 250 volt ac (50hz & 60hz) . Please help me about this topic to find out circuit..

Not really an Arduino topic, is it?

CRJ:
I want to develop 12v/2a SMPS without transformer.Input of smps will be between 90 to 250 volt ac (50hz & 60hz) . Please help me about this topic to find out circuit..

Surely you do not.

There are zillions of these readily available and very cheap.

If its a homework question at least think a bit about a better forum to ask about switched mode power supply design.

Here’s one for 120mA output.

From Circuits Today

For a simpler power supply search in google for either “Transformer-less power supply” or a “Capacitive dropper” , but 2A is not possible for these types.

Why transformer-less.
Transformers provide isolation from the mains.
That circuit in post#3 is dangerous, because it’s directly connected to mains power.

12volt/2Amp supplies are cheap and easy to get. I use one from an external hard drive enclosure.
Leo…

Wawa:
That circuit in post#3 is dangerous, because it's directly connected to mains power.

It is, if you handle it without safety precautions. The OP wanted one without transformer, he should have known the disadvantage of such a supply without galvanic isolation.

Edit:

Wawa:
Why transformer-less....12volt/2Amp supplies are cheap and easy to get.

I presume he is developing one, possibly for a client who paid or will pay him, and he needs arduino forum to help him develop that supply. How convenient.

Noobian:
I presume he is developing one, possibly for a client who paid or will pay him, and he needs arduino forum to help him develop that supply. How convenient.

I find it hard to believe that anyone would pay a most probably inexperienced hardware developer to design this potentially dangerous component.

Hard to believe doesn't mean it's not possible. If the client had substantial knowledge about electronics they would develop it themselves and if they don't then they just go for the lowest bidder, experienced or not.

There are a lot of businesses out there which suffer from serious communication gaps between technical department and their other department, some might even be lacking a technical department. I have won bids from local led tube light manufacturers to design power supply for their tubes even though I don't know anything much about electronics.

The specifications the OP asked sounded a lot familiar to the specifications I got from those manufacturers.

Noobian:
I have won bids from local led tube light manufacturers to design power supply for their tubes even though I don't know anything much about electronics.

I hope you have good third party insurance and a good lawyer !

Hi,
@Noobian

I have won bids from local led tube light manufacturers to design power supply for their tubes even though I don’t know anything much about electronics.

Who is running these companies, no wonder we have so many ebay “specials” that don’t cut the mustard when asked to perform to claimed specification.

Can you tell me the manufactures names so I can avoid ALL their products.

@CRJ can you tell us your electronics, programming, Arduino, hardware experience?

Tom… :o :o :o :o :o :o :o

TomGeorge:
Who is running these companies, no wonder we have so many ebay "specials" that don't cut the mustard when asked to perform to claimed specification.

Can you tell me the manufactures names so I can avoid ALL their products.

Mostly startups that jumped on to the led lighting bandwagon to exploit the increasing market share these products have. Fake led chips + cheap plastic housing + capacitive dropper = led bulb cheaper than cfl and almost double the price of an incandescent.

One of them is an led tube called 'new omini', their product and company name is the same. leds are over driven so that they can skimp on the number of already cheap leds. No heatsink to save money on aluminum. capacitive supply, no galvanic isolation since they figured plastic body is not conductive and that tube lights mounted high up on the wall where nobody touches. Most of these tubes die within a year, so people are forced to buy new ones, sure beats the purpose of using leds in the first place, lol.
Another one is 'vihan', same story except they used a heatsink on some models for a while.

You don't have to worry as these things are never exported, obviously because electronics without certification cannot be exported or sold in the west?.

stowite:
I hope you have good third party insurance and a good lawyer !

That's not how things work in some parts of the world.

Does anyone see any obvious problems with the supplied circuits today circuit?
Hint , how does the circuit regulate the output to 12V?

mauried:
Does anyone see any obvious problems with the supplied circuits today circuit?
Hint , how does the circuit regulate the output to 12V?

Hi,
Me too.
Earlier in the article that the diagram comes from is this dagram.

I think a wire is missing, would be nice if they labelled the pins in this diag.

The circuit explanation is;

The circuit diagram of a practical 12V/120mA transformerless switch mode power supply is shown above. Resistor R1, capacitors C1 and C2, diodes D1 and D2 and inductor L1 forms the input stage. D1 and D2 forms the rectifier section while C1 and C2 are input filters. Resistor R1 which is a fusible resistor limits the inrush current, increases differential mode noise attenuation and also serves as an input safety fuse.
The next stage is the regulator stage which consists of IC LNK304, diodes D3 and D4, capacitors C3, C4 and C5, resistors R3, R4 and R5 and inductor L2. D3 is the freewheeling diode while L2 is the output choke. C5 is the output filter capacitor which limits the output ripple voltage to a value as low as possible. The IC LNK304 is so configured that the power supply operated in the most discontinuous mode and that’s why a fast recovery diode (UF4005) is used as the freewheeling diode (D3). UF4005 has a reverse recovery time of around 75nS and it is well enough for the given situation.
The voltage drop across diodes D3 and D4 are practically same and so the voltage across C4 tracks the output voltage and this voltage is picked by the network comprising of resistors R2, R3 and is fed to the feedback pin. R2 and R3 sets the output voltage and for 12V output the voltage at the feedback pin must be 1.65V DC. The circuit attains regulation by skipping the switching cycles. When the output voltage rise, the current at the feedback pin also rises and when the current rises above the threshold value, subsequent cycles are skipped until the current at the feedback pin goes below the threshold and thus a constant output voltage is maintained.
The IC will auto restart if no cycles are skipped during a 50mS time period and this limits the maximum output power to 6% of the maximum over load power. That’s how over load protection is attained. Resistor R4 serves as a small preload which nullifies the effects of tracking error.

If it was a constant current circuit fine, but they describe it as a voltage regulation.
Tom.... :o
I wouldn't touch it with an insulated barge pole.

I wouldn't touch it with an insulated barge pole

...and my rubber lineman gloves on :wink:

The concept is no worse than a capacitive dropper which are just as dangerous , but you will find them in a lot of cheap household appliances like radio controlled power points.
But 2A from a capacitive dropper is impractical for this purpose due to the physical size of the capacitor thats needed.
In this case its just as impractical due to the size of the inductor for L2 thats needed, roughly 8mh with a saturation current of 2.4 A minimum.