This post shows you how to build a power supply to directly power bright LEDs from your wall outlet.
It is made especially for white LEDs, but it can also work with other colors like blue, green, red, yellow and even ultraviolet UV.
What is a 5 Watt LED Driver Circuit:
A 5 Watt LED driver circuit is designed to provide a regulated and constant current or voltage to power a 5 watt Light Emitting Diode LED.
LEDs require a specific current or voltage to operate efficiently and reliably, and a dedicated LED driver helps achieve this by maintaining the necessary electrical parameters.
The schematic diagram below is a 5 Watt LED Driver Circuit depicts a self oscillating flyback converter ensuring efficient LED operation directly from the mains.
Parts List:
| Component Type | Description | Quantity |
|---|---|---|
| Resistors | ||
| 10Ω, 1W MFR | 1 | |
| 470k, 1W MFR | 1 | |
| 330Ω, 1/4 W MFR | 1 | |
| 100k, 1/4 W MFR | 1 | |
| 47Ω, 1/4 W MFR | 1 | |
| Rx = See text | 1 | |
| Capacitors | ||
| PPC 4.7nF / 500V | 1 | |
| PPC 2.2nF / 50V | 1 | |
| Electrolytic 4.7μF / 400V | 2 | |
| Tantalum 4.7μF / 16V | 2 | |
| Semiconductors | ||
| Diode 1N4007 | 4 | |
| Diode 1N4148 | 1 | |
| Fast diode BA159 | 1 | |
| Schottky diode 1N5844 | 1 | |
| Transistors | ||
| Transistor KSC5027 | 1 | |
| Transistor BC547 | 1 | |
| Other | ||
| LED 5 Watt White | 1 | |
| Transformer (as given in article) | 1 | |
| Filter Inductor (as given in article) | 1 |
Schematic Operation
The power supply operates as a flyback self oscillating converter utilizing the primary winding T1 as the power switch.
A KSC5027 transistor can be employed for this purpose.
This design operates in current mode, with LED current sensed by the shunt resistor Rx.
The auxiliary winding also serves as a feedback mechanism.
Resistor Calculation
To determine the shunt resistor value Rx use the formula:
Rx = 0.65V / I
where,
- I is the desired LED current.
Adjusting LED current allows for increased efficiency and extended LED lifetime.
Transformer Construction
The transformer Tr1 is wound on an EE core with a middle column measuring 4.5 x 4.5 mm sourced from an old ATX PC supply.
The primary winding consists of 180 turns with a wire diameter of 0.2 mm ,and the secondary winding comprises 6 turns of triple wire with a diameter of 0.5 mm.
The winding sequence involves the first half of the primary followed by the secondary, and then the remaining half of the primary.
Alternatively, a ready made transformer designed for 5V switching power supplies can be utilized with the auxiliary winding left unused.
Adding Voltage Feedback
demonstrates how to incorporate voltage feedback into the power supply ensuring its resilience in the event of LED disconnection or failure.
This addition enhances the overall reliability of the system.
Power Supply Frequency
The power supply operates at a frequency of approximately 80 kHz optimizing its performance for LED applications.
Circuit Construction :
Constructing a 5 Watt LED Driver Circuit operating directly from 220V mains voltage are mentioned below:
- Wind the primary winding with 180 turns of wire with a diameter of 0.2 mm.
- Wind the secondary winding with 6 turns of triple wire with a diameter of 0.5 mm.
- Wind the first half of the primary 90 turns followed by the secondary, and then the remaining half of the primary.
- Install the transistor eg KSC5027 to perform the power switch function.
- Calculate the shunt resistor value using the formula R = 0.65 VIR = I0.65V.
- Connect the shunt resistor Rx to sense the LED current.
- Integrate the Schottky diode as the rectifier due to its higher efficiency.
- Place capacitors and resistors according to the schematic
- Ensure the correct values and orientations.
- Connect the LED to the output ensuring correct polarity.
Testing:
- Power up the circuit gradually using a variable power supply.
- Monitor LED operation and measure output voltage and current.
Warning: Safety Precautions
It is crucial to emphasize that this switching power supply is not recommended for beginners, as all circuits are directly connected to fatal mains voltage.
The LED diode is not isolated from the mains, and capacitors may retain dangerous voltages even when disconnected.
All activities are undertaken at ones own risk and the author assumes no responsibility for any injury to health or property.
Safety precautions should be strictly adhered to throughout the construction and operation of this power supply.