Think you have a hose with strong water pressure 12V, but your plant needs a gentle sprinkle 3.3 to 3.5V. A buck converter circuit is like a fancy adapter for your hose.
It takes the strong pressure and lowers it to the perfect level for your plant.
This circuit also makes sure the water flow current is just right so your plant does not get flooded.
This way, it keeps your LED nice and bright without burning it out.
Circuit Working:
Parts List:
| Category | Description | Quantity |
|---|---|---|
| Resistors | 10k, 330Ω, 1k, 100Ω, 390Ω, 1Ω (1/4 watt each) | 1 each |
| 100k (1/4 watt) | 2 | |
| Preset 2k | 1 | |
| Capacitors | Ceramic 1nF | 1 |
| Ceramic 330pF | 1 | |
| Electrolytic 100μF 25V | 1 | |
| Semiconductors | Transistors BC547 | 3 |
| Transistor BC327 | 1 | |
| Diode UF4004 | 1 | |
| LED | 1W LED | 1 |
| Inductor | 10mH with 70 turns of 0.25mm wire wound around its core | 1 |
This buck converter circuit is designed to power a 1 watt white LED using a 12V power supply delivering a constant current of 300mA.
It utilizes a BC327 transistor as the driver and a 10mH inductor with 70 turns of 0.25mm wire wound around its core.
The LED operate at a voltage between 3.3V and 3.5V.
To measure the LED current a 1 ohm resistor R8 is used with a voltage drop of 300mV corresponding to a 300mA LED current.
The diode in the circuit must be high speed using a non high speed diode can increase the current by 50mA.
This circuit is considered optimal because it avoids current spike through the LED.
To increase the maximum current the 390 ohm resistor must be slightly reduced.
Formulas:
A buck converter circuits efficiency, operating frequency, and component selection are some of the factors to be taken into account while designing a circuit to drive a one watt LED.
The following basic outline and essential formula will assist you in comprehending and creating such a circuit:
Output Voltage Vout:
Vout = Vin×(D / 1−D)
where,
- Vin is the input voltage.
- D (Duty Cycle) is the ratio of ON time of the switch to the total period.
Duty Cycle D:
D = Vout / Vin+Vout
Inductor Current IL:
The following may be used to estimate average inductor current:
IL=Vout *(1−D) / L*Ton
where,
- Our inductance is L.
- Switch ON time is represented by Ton.
Switching Frequency f:
f = 1 / T = Vin / L *(Vin−Vout)*IL
where,
- T is the switching period.
The basis for creating a buck converter circuit for a 1 Watt LED driver is provided by these formulas
The precise voltage and current requirements of your LED and input power source will determine the details of your calculations and component choices.
How to Build:
To build a Buck Converter Circuit for 1 Watt LED Driver you need to follow the below mentioned steps for connections:
- Connect the collector of transistor Q1 to positive supply through resistor R1.
- Connect the base of transistor Q1 to R4 resistor and C2 capacitor.
- Connect the emitter of transistor Q1 to ground.
- Connect the collector of transistor Q2 to R5 and R6 resistor.
- Connect the base of transistor Q2 to positive supply through R2 resistor.
- Connect the emitter of transistor Q3 to ground.
- Connect the collector of transistor Q3 to one end of R3 resistor and other end of R3 resistor connect to base of transistor Q2.
- Connect the base of transistor Q3 to one leg of P1 preset.
- Connect the emitter of transistor Q3 to ground.
- Connect the collector of transistor Q4 to ground through D1 diode.
- Connect base of transistor Q4 between the series of two resistors R5 and R6.
- Connect emitter of transistor Q4 to positive supply.
- Connect a inductor coil and a resistor R8 in series from the collector of transistor Q4.
- Connect a capacitor C3 between inductor coil and a resistor R8
- Connect a 1 watt LED from R8 resistor to ground.
- Connect C1 capacitor between R1 and R2 resistor.
- Connect a resistor R7 from one leg of P1 preset to ground.
Safety Note:
- Choose components rated for the required voltage, current and temperature range to ensure reliable operation.
- Incorporate short circuit protection to prevent damage in case of a short circuit in the LED or circuitry.
Conclusion:
To conclude, a buck converter circuit for a 1 watt LED driver efficiently steps down a higher input voltage to the lower voltage required by the LED, while also regulating the output current to ensure safe and constant operation of the LED.