32V, 3 Amp LED Driver SMPS Circuit

The article presents 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