In this article I have explained a 32V, 3 amp SMPS circuit which may be specifically used as an SMPS 100 watt LED driver, rated with the same specs.
The circuit of the proposed 32 V, 3 amp smps led driver may be understood with the the help of the following points:
Circuit Operation
The mains voltage is rectified and filtered by the bridge network and the associated filter capacitor C1. This rectified 310 V DC passes through R1, R2 and triggers T1 into conduction.
T1 switches ON and pulls this DC to ground through the 30 + 30 primary winding inducing a steep pulse through this winding and also across the lower auxiliary winding.
This pulse across the auxiliary winding enables a negative pulse to be generated at the junction of R1/R2 which momentarily sinks the base drive to ground such that T1 now shuts off.
In the meantime C2 charges up drying up the auxiliary winding impact, and allows T1 with a fresh triggering potential at its base.
T1 conducts yet again and the cycle keeps repeating at a frequency determined by the value of R2/R3/C2 which could be around 60 kHz here.
This rapid switching induces a corresponding voltage and current across the secondary winding which may be well over 32 V, 3amps AC as per the given winding details.
The above voltage is appropriately filtered by C4 and applied across R6, R7 for feeding the shunt regulator and the opto coupler stage.
R6 is appropriately adjusted such that the output voltage settles to about 32 V.
The Shunt Regulator
The shunt regulator instantly activates the opto in case the voltage tends to rise above the set value.
The opto in turn "kills" the base drive of T1 temporarily disabling the primary operations until the output potential is restored to the correct value, the opto now releases T1 and allows the operations to work normally, only until the output rises again to initiate the opto yet again, the process keeps repeating ensuring a constant 32 V at the output, for driving the 100 watt LED module safely
Circuit Diagram of 32V 3A LED Driver for 100 Watt LED
The transformer is wound over a standard EE ferrite core having a central cross sectional area of at least 7 square mm.
Referring to the figure, the upper two primary winding are made up 30 turns of 0.3 mm diameter super enameled copper wire.
How to Wind the Ferrite Transformer
The lower primary auxiliary primary winding consists of 4 turns of the same wire as above.
The secondary is wound with 22 turns of 0.6mm super enameled copper wire.
The procedures are as follows:
- First begin winding the upper 30 turns, secure its ends on the bobbin leads by soldering, and put a thick layer of insulation tape over these turns.
- Next, wind the secondary 22 turns and solder its end terminals on the other side of the bobbin leads, put a layer of thick insulation tape.
- Over the above layer start winding the auxiliary 4 turns and as above secure the ends appropriately on the primary side leads of the bobbin, again put some layers of insulation over this,
- Finally, wind the second 30 primary turns starting from the previous 30 turn end, and secure the end over one of the leads of the bobbin on the primary side.
- Cover the finished winding with additional layers of insulation tapes.
- Make sure you remember the terminated leads properly so that you don't make incorrect connections with the circuit and cause a possible fire hazard.
Parts List
All 1 watt, CFR
- R1 = 10E
- R2 = 1M
- R3 = 470E
- R4 = 100E
All 1/4 watt MFR 5%
- R5 = 470E
- R6 = preset 22k
- R7 = 2k2
- C1 = 10uF/400V
- C2 = 2.2nF/250V
- C3 = 220pF/1kV
- C4 = 2200uF/50V
- D1---D4 = 1N4007
- D5, D6 = BA159
- shunt regulator = TL431
- opto = 4n35
- T1 = MJE13005
at the output 3 amp how can we use BA159 its 1amp diode
Yes that’s right, please change it to a 5 amp schottky diode.
sir you have not defined the primary inductance of transformer
Hello Sanjay,
Inductance value is not known to me, and I think it is not required since the winding specifications are given in details.
Hello swagatam pls help me .I built this smps circuit but it doesn’t work am not getting any voltage at the output of the transformer and secondly I used 13003 transistor instead of 13005 due to unavailability but it didn’t work so I now changed the 13003 to 13001 transistor which it blew up again i don’t no why but pls help me asap……..
Hello Okongwu,
the person who contributed me this article has tested this design successfully.
However, please remember that the heart of any SMPS is its transformer. If you make even a smallest of mistakes in the transformer winding then it may have serious consequences or it may simply not work.
I would suggest that initially you keep the opto feedback cut off or removed from the circuit and test just the basic response.
Make sure to provide a paper gap between the E core legs where the two e cores join with each other.
Always use a 40 or 60 watt bulb in series with the 220V mains while testing an smps circuit.
Dear swagatam I used an EE16 FERRITE core transformer with no air gap ,and what is the importance of an air gap in a FERRITE transformer. And pls can I have your WhatsApp number I wish to learn more from you
Thank you…….
Hi Miracle,
Air gap or paper gap prevent the transformer core from getting saturated which can otherwise result in short circuiting of the switching transistor.
You can communicate with me through this blog comment platform since I am mostly online with my blog. You can ask as many questions as you want, I will try to help.
Hello swagatam how can I reduce the voltage of this circuit to 4.2v in order for me to charge a lithuim ion battery???
Hello Okongwu,
For 4.2V you can try the concept explained in the following article:
https://www.homemade-circuits.com/220v-smps-cell-phone-charger-circuit/
Swagatam, good afternoon.
I am an industrial automation engineer.
I am doing such a project, it is for people with low incomes.
https://www.facebook.com/dan.saudabaev/posts/pfbid02nT1yLhhQ4kspxVPupVZtntpHeiCMfnLPmBa5KoxWeu2QJ6gn8Gmk7bqbDXFtiFkjl
I bought samples of lamps on Sanan & Seuol diodes, spectrum 5000k+660nm (for leafy greens) – lamps 24V/40W (1.66A).
We sell regular switching power supplies
POWER SUPPLY 24V 20A 480W ($16).
There is no 36V.
I want to connect DC-DC converters (XL4016) to it.
It has two resistors for voltage and current.
– stabilization in both current and voltage (right?)!!!
Set the output to 24V, reduce the current for the lamps by 5% (1.58A).
And connect the lamps in parallel.
Sir, reducing the current by 5% will give me a guarantee that all the lamps will work without any problem?
In the description –
10. For example: input 12V * 5A = 60W, input 24V * 5A = 120W
Input 36V * 5A = 180W, input 48V * 5A = 240W
Sir, approximately how many watts can this DC-DC converter produce?
Efficiency, if 4-5A will be higher than 90%?
Another option is a DC-DC converter:
I asked them questions in the morning, they promised to answer, but there is still no answer. There are few specialists there… – they can’t even answer basic questions!
Thank you Dan,
If the current limiting is set to provide 1.58A then the LED lamps cannot get more than this value. So if the requirement for your parallel LED lamps is more than 1.58A then their light intensity will become reduced and they will look dim.
Swagatam, hi.
You’re right –
https://www.homemade-circuits.com/wp-content/uploads/2023/10/LED-forward-current-vs-forward-voltage.jpg
You can see this clearly from the electrical characteristics of the Cree XP-G2 below in Figure 1. When the LED is turned on, even the smallest 5% change in voltage (2.74V to 2.87V) can create a 100% increase in current driven to the XP-G2 as you can see at the red marks current went from 350mA to 700mA.
– I’m very surprised that a minor change can have such an impact!!!
Thank you)))
Thanks Dan,
Yes i agree.
As the voltage nears the LED’s maximum forward drop level, the current tends to increase drasitically. That is why it is crucial to have a constant voltage supply which can never exceed the forward drop level of the LED.
– constant voltage driver?
Sorry to interrupt you…
But if the external voltage jumps, and the driver output has a stabilized voltage
– then the current will change, which will have a very negative impact on the diodes!!!
I chose the fixed current driver DL-400W-V260X-PLS
Input voltage 120-277V.
They told me that they could use a programmer to fix the current I needed (1.66A).
And I want to connect 8 lamps in series (24VDC, 40W, 1.66A).
– Am I doing it wrong!???
Dan,
With a consant voltage regulator the voltage to the LED can never jump, unless the input AC becomes exceedingly high, which would anyway destroy all forms of stabiliziing elements.
If the DC voltage is fixed or constant then current becomes immaterial, meaning larger current will have no impact on the LED. For example if you supply a 3.3 V to a 3.3 V LED, with a current of a million amps, the LED would still illumnate safely and draw only the amount of current it needs optimally at 3.3V.
Conversely, if you have a fixed or a constant current then the voltage becomes immaterial, meaning suppose if you have a current limit applied to a 3.3V LED, then even if the volatge increases to 100V or 1000V it would drop down to 3.3V without harming the LED.
If you are too much concerned then you can have both constant current and constant voltage supply for your LEDs.
Sir, excuse me, one more question.
Where I ordered samples of lamps, a girl works there as an engineer.
They agree to check the connection of 8 lamps to this driver.
But she claims that they have constant voltage lamps (24VDC, 40W) and this driver will not work.
I explained to her that there is no such thing as constant voltage or constant current lamps.
I asked for a wiring diagram for the diodes, but for the second day it was silent.
I gave them a diagram of how to check –
https://photos.google.com/photo/AF1QipNMR479Lv7Msybv3Nj5RwHU9G9kY520JSYeVax5
Using Variac Auto Transformer we change the input alternating voltage 150-250V, using multimeter 2 we look at the variable voltage, using multimeter 1 we look at the fixed current (1.66A).
I don’t know how else to explain to them))))
Maybe you can help?
Dan, You can show me the picture link of the lamp, I will try to figure out its specifications.
The link of your google photos is not opening in my computer.
Sir, sorry, I’ve been working all day.
I made the link wrong.
https://photos.app.goo.gl/ChLTCjH344kk6yzM8
Hi Dan, THe voltmeter and the ammmeter connections are correcty wired. No problems.
Good morning sir.
https://photos.app.goo.gl/KsTvj643rAYi2K1s9
– this is the programmer they have.
That link is not working.
Sorry, I did not understand what you mean by programmer? I actually asked about the LED specification which you are having problem with.
Programmer – I’m talking about the capabilities of this company that produces drivers.
https://drive.google.com/file/d/1s5KFJelMUinbIDeyOztnIIc3_tKuxfMO/view?usp=drive_link – just received.
– diode connection diagram.
They made me two samples using diodes:
– SANAN MH-S3030E23C50HE https://www.homemade-circuits.com/wp-content/uploads/2023/10/3030-SMD-LED-specifications.jpg
– SEOUL 3030C.
They claim that voltage drivers are needed for these lamps.
Are there diode circuits for voltage or current?
Your first googlr dive link needs to be in the shared mode otherwise it won’t open for me.
You can see in the second link, all the specifications of the LEDs are given.
You simply need a constant voltage and a constant current LED circuit adjusted to the above specifications, that’s all, and the LED will be safely driven. Ofcourse if the LED heat up a bit then you might require a heatsink also.
Good afternoon sir.
Sorry, I’ll repeat it again.
The company that produces the lamps claims that their lamps are for voltage drivers.
I sent you their lamp wiring diagram, there are 276 diodes.
They have 10 sections (each with 27 diodes), I think there is such a connection – https://drive.google.com/file/d/1N1w1mSncy970dPmukWq9ivNcBqu1UG08/view
Swagatam, these lamps, if you connect them 8 in series – https://photos.app.goo.gl/ChLTCjH344kk6yzM8
– will they work under a current driver?
I have no doubt that these lamps will work under both a current driver and a voltage driver – there is no difference there!!
Hi Dan, Your Google drive link is not opening because you have not sent it in shared mode.
Yes, LEDs in series will work with constant current driver circuit.
Using a constant voltage and a constant current driver is the best option.
https://photos.app.goo.gl/WXpbqmcuN3fisnFt7
– opens?
They have 276 diodes on the lamp.
I took one sector (there are 10 in total).
There are 27 diodes in this sector.
If we take an operating current of 65 mA, then the result is a current of 195 mA in three parallel circuits.
If there are 10 sectors, then the total is 1.95A.
However, they state that the lamp is 24V and 1.66A.
Are they wrong or am I wrong?
Yes the image opens now.
Your calculations are perfectly correct.
Did you ask them the reason why they state it should be 1.66 amps?
It maybe because they want to reduce stress on the LEDs to enhance their life.
By the way if 65 mA is the maximum breakdown current of these LEDs then it may be recommended to use a current that’s below 65 mA
Thank you sir ))))
As an LED lighting specialist, you helped me a lot!!!
You are most welcome Dan, Glad I could help!
Hi, have you got PCB project for this power supply?
Hi, sorry, a PCB is not available for this project!
Sorry Swagatam, I forgot to ask
– what is the efficiency of these SMPS drivers?
Efficiency could be around 80 to 90%
I need some advice.
Sir, please help.
alibaba.com/product-detail/Exclusive-Design-Against-Moisture-And-Dust_1600724917607.html?spm=a2700.details.0.0.52ac6e5b3ohgnl
– it says here – 100W 200W 300W 400W Smps Dc12v 24V Constant Voltage LED Pulse.
Does this LED driver have stable constant current?
I’m a little confused by what it says – constant tension!
Thank you very much sir!
Hi Dan, if the unit is specified for operating power LEDs then it should be current controlled, however since no specific mentions are made it is always better to inquire about the same from the manufacturer before purchasing it.
Thank you very much, sir)))
You are welcome Dan!
I have made this circuit but it is giving 24v in open circuit condition and 11v when load is connected. As it crosses 11v, MJE13005 is getting short circuit and R1 is getting burnt. Can anyone help me?
Adjust the R6 R7 resistors to increase or decrease the output voltage. If the transformer is not built correctly then the transistor will burn. Make sure to add a paper gap between the E core legs.
All SMPS circuits published in this blog are strictly recommended only for the experts who are well versed with electronic switching circuits.
Few observations:
1) 7mm^2 looks like suspiciously small value for 100W something. Especially flyback.
2) Its much better to use versions of RCC flybacks that employ current-sense resistor and transistor that closes main switch upon reaching current limit. Without current sense this thing would blow up badly upon e.g. short circuit in secondary due to lack of protections limiting outup power. Current sense resistor hooked to small BJT closing main one – and once voltage exceeding about 0.6V it would initiate shutdown of main transistor. Net result is that current in primary winding limited to whatever value causing 0.6V drop on resistor (so value of current sense resistor sets available output power) and wouldnt exceed that, not even on output short circuit – actually that’s what makes flybacks quite robust things.
How to calculate RC time constant ?
Auxiliary winding has 4 turns , how much voltage will be induced to secondary winding ?
You can search it online, you will get the formula from wikipedia.
Auxiliary winding is only for switching the transistor base….the actual voltage induction happens across the upper primary winding and the secondary winding…the secondary winding will produce over 50 V.
Sir, What is the role of Diode D5 ??
R2 = 1M, R3 ~= 0.5K (suppose voltage Across C1 is 315 V).
Using these values
Total Voltage across (R3+ D5) : = 0.857 (0.157 Volt Across R3 + 0.7 Across D5 )
To conduct the Transistor ?
Sanjay, D5 is for neutralizing any residual negative spikes that may arise from the high frequency oscillation.
Total voltage across D5 will 315 V but due to extremely low current it will drop to the transistor’s base/emitter forward voltage 0.7 V enabling a forward bias for the transistor base.
Hello sir what would be the typical value of transformer in order to purchase it.
Hello Rohit, the transformer shown in the above diagram is not available ready made….you can either build it at home, or get it made-to-order from a professional coil manufacturer
Swagatam sir,
What changes are needed in design for 12V 3A and how much the new circuit may cost approx.
Thanks in advance.
Shivraj, for 12V 3 amp you can use the following circuit:
https://www.homemade-circuits.com/12v-5-amp-transformerless-battery/
I am not sure about the cost of the circuit.
Thank you sir.