12V SMPS Driver Circuit for LED Strip

A 12V SMPS Switch Mode Power Supply Driver Circuit is a regulated power source that transforms mains power which is typically 110V or 220V AC, into a steady and secure 12V DC voltage that may be used to light LED strips.

We will construct a simple, reasonably priced and potent LED driver circuit in this DIY project post.

This circuit may be used to power a whole 12V light string with more than 100 or even 200 LEDs.

Important Note:

This circuit converts the 12V output in an isolated way using a direct 230V AC power supply, this gadget is extremely unsafe to use.

It has no further protection other than output short circuit protection.

If you are determined to construct your own SMPS circuit, careful study and adherence to a trustworthy circuit diagram with safety precautions are essential.

Before taking on a job of this nature, make sure you possess the required abilities and expertise.

Circuit Working:

Parts List:

Prior to exploring into the operation of the LED strip driver, it is crucial to understand the fundamental concepts behind the circuit.

Due to the high voltage involved this circuit should always be protected by a sturdy enclosure.

But first, we will look at an exposed simpler version that was constructed on a solderless prototyping board (Veroboard) to better comprehend its purpose.

Feedback Capacitor C1:

This capacitor aids in controlling the output voltage of the circuit.

Primary Supervisor TNY285DG:

This chip regulates the transformer serving as the circuits brain.

It works by quickly turning on and off the current at a very high frequency 125kHz.

Internal Capacitor C2:

This capacitor maintains the primary controller chips internal operations IC1.

R1 and R2 together form the under voltage lockout which senses when the input voltage is too low.

In order to protect itself, the main controller IC1 will halt switching if the voltage falls below a certain threshold.

Transient Voltage Protection D1 & D2:

The primary controller chip IC1 is protected against abrupt voltage spikes brought on by the transformer by the combined action of a voltage regulator and a diode.

They are essential to the protection of circuits.

Schottky Diode SB380 D3:

This diode is intended to handle the voltage and current levels in the circuit and aids in controlling the flow of electricity.

You can substitute any other schottky diode with a comparable rating.

Snubber Circuit R3 & C3:

The Schottky diode D3 is shielded from voltage spikes by this resistor and capacitor combination.

The output capacitor C5 ensures a constant supply of power to the LED strip by balancing the output voltage.

The optocoupler PC817 is an essential component in feedback control since it separates the circuits high and low voltage sides.

Transformer Construction:

Steps to design you own transformer:

• Wind 85 revolutions starting on pin 2.
• The wire needs to be one filar (magnet wire 34 AWG 0.16 mm, solderable double coated).
• Additionally, it needs to be double sided coated and solderable.
• Now go cautiously from left to right to the second layer.
• There is just one winding direction clockwise.
• Continue winding the subsequent layer from right to left when the first layer is finished.
• Spread the winding uniformly throughout the whole bobbin on the last layer.
• Complete this pin 1 winding.
• Increase the insulations three layers.
• The barrier tape polyester film [1 mil (25 µm) base thickness] 8.45 mm wide.
• Turn on the secondary winding.
• Pin 7 is the starting point, and wind 8 spins triple insulated wire 24 AWG (0.55 mm) single filar.
• Throughout the whole bobbin, distribute the winding equally.
• There is just one winding direction clockwise.
• Complete pin 6 winding now.
• Put on two coats of tape.
• Securely assemble the core halves.
• Dip Do not vacuum impregnate the transformer, instead evenly varnish it.

Formulas:

Here are some important formulae and things to keep in mind while designing a 12V SMPS (Switch Mode Power Supply) driver circuit for an LED strip utilizing integrated circuits:

Turns Ratio (Np/Ns):

N_p / N_{s ​​}= √V_out​* (V_in​−V_out​)​​ / V_in​* f * A_e​

where,

• Np = The quantity of primary turns
• Ns = The quantity of secondary turns
• Vin = Input voltage 12V.
• Vout = The output voltage 12V.
• f = The SMPSs operating frequency (usually expressed in kHz)
• Ae = The cores effective cross sectional area

Peak Primary Current (Ipeakprimary):

I_{peakprimary​} = V_in​ * D_max​​ / f * A_e​

where,

• Maximum duty cycle of the switching regulator is represented by Dmax.

Output Capacitor (Cout):

C_out​ ≥I_out​ * (1−D)​ / f * ΔV_out​

where,

• Iout = Current output
• Dstands for the converters duty cycle.
• ΔVout = The outputs ripple voltage

Feedback Voltage Divider:

V_out / V_ref ​​= R_top​​ / R_bottom​

where,

• Vref = The TL431s reference voltage, which is usually 2.5V.

Efficiency (η):

η = P_out / P_{in ​​​}× 100%

where,

• Pout​ = Output power
• Pin = Input power

Note:

You may use these formulas as a starting point to figure out the size and values of the components in your SMPS design.

Nevertheless, certain conditions, such the maximum load current, the required efficiency, and the switching frequency used for your application, will determine the precise numbers.

Always consult the datasheets of the components you have selected (such as TL431, TNY285DG, etc.) to find sample circuits and comprehensive application notes that align with your design objectives.

How to Build:

To build a 12V SMPS Driver Circuit for LED Strip follow the below mentioned steps for connections:

• Gather all the components as mentioned in the the above circuit diagram
• Connect pin 1 of IC1 to positive supply through resistors R1 and R2.
• Connect pin 2 of IC1 to ground through capacitor C2.
• Connect pin 4 of IC1 to positive supply through diodes D1 and D2
• Connect pin 5,6,7, and 8 of IC1 to ground.
• Connect capacitor C1 from positive supply to ground.
• Connect pin 1 of IC2 to cathode of IC3, connect pin 2 of IC2 to positive supply, connect pin 3 of IC2 to ground, connect pin 4 of IC2 to pin 1 of IC1.
• Connect pin 1 of IC3 to capacitor C4, connect anode pin of IC3 to negative supply (0V), connect cathode pin of IC3 to pin 1 of IC2.
• Connect one leg of ferrite transformer to 230V positive supply of primary side, connect 2nd leg to pin 4 of IC1, connect pin 3 to negative supply (0V) and connect fourth neg to secondary side of 12V supply
• Connect a bridge rectifier negative leg to ground, positive leg 220V positive supply, connect remaining 2 legs to 220V AC supply.

Conclusion:

To conclude, Its nice to build 12V SMPS Driver Circuit for LED Strip, SMPS circuits are more effective than linear regulators particularly when large power conversions are involved.

Less energy is lost as heat as a result, but safety comes first!

Before touching, unplug, operate in a well lit location and hire an expert for high voltage operations.

Develop your abilities on lower voltage tasks by starting small.

References:

Datasheet TNY285DG

Datasheet IC PC817

Datasheet IC TL431