World simplest SMPS Circuit

[grittinjames]

smps circuit

Hi.
Here i have attached the circuit.
Dont forget to give minimum load
For tx winding and more detail mail me
thanks

 

[eem2am]

smps circuit diagram

is this what they used to call a Royer converter>?
i know it was once very popular........still used today i believe.

the trouble it is has no feedback

 

[neelandan]

simplest smps

I have looked at the circuit of a few SMPS chargers for mobile phones and they use a variant of this circuit.

The simplest have no feedback at all, and the output voltage varies linearly with the supply current.

Next up, is voltage feedback from an auxiliary winding. There is some regulation.

The reputed brands include an optoisolator with sensing of the output voltage.

 

[grittinjames]

circuit of +cheap smps

Ys Opto isolated version also available.
I will post it soon

Added after 10 minutes:

any one please explain its working?

 

[me_guitarist]

smps schematics

Anybody can tell what is the output voltage & current?

 

[me_guitarist]

smps cct diagram

Any similar circuit that can provide 24VDC with 100mA? Transformer less PSU wanted.

 

[arbj]

circuit diagram of smps

i used a NCP 1010 monolithic converter to make a similar SMPS design, but I find that the SMPS stops working when the input voltage is more than 75 VAC...why is this???

Has anyone used the IC before...?

thanks
aa

 

[grittinjames]

smps forum mje13005

hi arbj
plz post ur schematics for better responds

 

[eem2am]

cfl circuit diagram

hi

looks good but how does it regulate the output voltage.......?

what if the input voltage changes?

is it a Royer converter ?

I think they use similar in CFL ballast

shame appears no regulation though

 

[grittinjames]

royer converter

ys
here there is no regulation.
but these can be used aplications such as high brightnes LED etc were constant load is present

 

[grittinjames]

smps design with mje13005 transistor

Considering all of your request I am posting circuit with feedback.
This circuit is tested and working well
If someone required PCB design I can provide

Please note
I forgot to place a 1M from VCC to Base of MJE 13003 in schematics.

 

[evision]

bjt smps

What is the output current ? How to increase/decrease o/p voltage ? is it by varying o/p turns ?

 

[eem2am]

circut diagram of smps

i have a problem with this circuit...what if the storage time of the BJTs is long?.....it will mean they will blow up ?

....someone will have to be payed to sort through bjt's testing for the ones that have the good enough storage time for your application.

i'm sorry to say this, but i feel it is truthful

 

[max0412]

royer circuit with led loads

what if the storage time of the BJTs is long?

Place a cap in PARALLEL with the base resistor of your BJT. You will have to experiment to get the optimum value usually somewhere between 200pf to 2n.

 

[eem2am]

china make smps circuit

hello,

i know putting a cap in parallel with the base resistor improves the turn off time due to charge storage, but it won't be enough to mitigate it well enough.

this circuit is often used in CFL bulbs , and if you look inside one, they do not have a parallel cap like that.

...what they do is they test each individual transistor in the factory and only take the ones with short storage time.

these CFL bulbs actually use T0-92 package BJTs which is amazing when you think its a DC bus of 330V (even though the current is only low the turn off power can still be high enough to damage the t0-92 bjt for a 15W lamp)

 

[FvM]

smps circuit world

...what they do is they test each individual transistor in the factory and only take the ones with short storage time.

Very unlikely, to my opinion. Have you seen this? Generally, dynamic transistor parameters can be expected not to show large variations. Highest variation is in DC gain for most types.

 

[eem2am]

small smps circuit transformer cfl

FvM,

I looked into using this kind of circuit some time ago, but a whole host of references insisted that you need to individually test each transistor, so i had to bin the idea of this circuit...it disappointed me because i was well into this circuit.

....of course , there are places where labour is very cheap and plentiful, and its not so bad for places in that situation to test each transistor individually....

...this kind of individual unit testing also happens with certain LEDs, to bin them accorcing to the forward voltage at rated current etc.

 

[Externet]

circuit daigram of s.m.p.s

And where does L1 gets its magnetic coupling from ?

 

[max0412]

circuit diagram smps

i know putting a cap in parallel with the base resistor improves the turn off time due to charge storage, but it won't be enough to mitigate it well enough.

Well it would depend on the frequency. As an example I just used a speed up cap for an NJT4031N low Vce sat high gain BJT driven off a PIC. Turn on time was reasonable sub 100nS in that area but turn off time was pathetic 1.4uS. Using a 10n speedup cap gave me a turn on time of 60ns and turn off time of 110ns so this BJT can easily be suitable for several hundred kHz. A smaller speed up cap would probably be good to but I have limited selection of thru-hole caps most of my caps are smd.

There are other tricks like a Baker clamp being one. If the transistor isn't driven into hard saturation the turn off time can be minimized at the expense of power dissipation in the bjt of course.

...what they do is they test each individual transistor in the factory and only take the ones with short storage time.

I’m not going to say that somewhere in china they aren’t paying someone a nickel a day to sort thru BJT’s nothing surprises me it just seems unlikely. Not only are BJT parameters vary widely with manufacturing tolerances but temperature has a impact particularly on hfe ,off the top of my head I’m not sure how temperature effects storage time.

 

[grittinjames]

how to change smps output voltage

And where does L1 gets its magnetic coupling from ?

all winding in same bobbin