A CFL bulb needs a special helper circuit to turn on and shine brightly.
This circuit acts like a translator, taking your regular home electricity and converting it into the right power and signals the CFL needs.
CFL bulbs are like tiny recyclers they use a little mercury vapor to create invisible light then zap a special powder inside to make the light you see.
Circuit Working:
Parts List:
| Category | Item | Quantity | Additional Specifications |
|---|---|---|---|
| Resistors | 2.2k | 2 | All resistors are assumed to be 1/4 watt |
| Capacitors | Ceramic 470pF | 2 | |
| Semiconductors | Transistors TIP142 | 2 | |
| Transformer Coil | (see the text) | 1 | |
| Miscellaneous | CFL Bulb 5W | 1 | |
| Battery | 12V | 1 |
The two TIP142 transistors are NPN Darlington transistors capable of handling high currents.
They are connected in a crossed coupled manner, where the base of each transistor is connected to the collector of the other transistor through a 2.2k resistor.
This configuration allows each transistor to turn off when the other is on creating a push pull operation.
The outer primary windings of the center tapped transformer are connected to the collectors of the transistors.
The center tap of the transformer is connected to the positive terminal of the battery while the emitters of the transistors are connected to the negative terminal of the battery.
This setup allows the transistors to switch the current flowing through the primary winding generating an alternating magnetic field in the transformer core.
When one transistor is on current flows through its collector emitter path creating a magnetic field in one direction in the transformer core.
This field induces a voltage in the secondary winding lighting up the CFL lamp.
When the other transistor turns on the current flows in the opposite direction creating a magnetic field in the opposite direction and maintaining the alternating current flow through the lamp.
The CFL lamp is connected to the secondary side of the transformer.
The alternating current induced in the secondary winding causes the CFL lamp to illuminate.
Overall, this circuit efficiently drives the CFL lamp using a push pull configuration allowing for high efficiency and reduced power consumption compared to other driver circuits.
Working of Transformer:
This circuit is designed to power a 5 watt Compact Fluorescent Lamp using a 12 volt power source.
The transformer is constructed by winding 50 turns and creating a center tap at one end.
An additional 50 turns are then wound for the push pull primary.
The transformers core can be a ferrite rod either round or flat salvaged from an old AM radio.
The secondary winding requires 500 turns.
These turns must be wound carefully on top of each other progressing across the rod to avoid overlapping.
This winding technique known as jumble winding is necessary because the enamel on the wire can only withstand up to 100V.
A wire diameter of 0.25mm or thinner is suitable for this purpose.
To prevent high voltage from shorting to the rod it is important to apply at least three layers of sticky tape before starting the winding process.
Electrical Characteristic for TIP142
| Characteristic | Symbol | Minimum | Maximum | Unit |
|---|---|---|---|---|
| Collector-Emitter Sustaining Voltage (1) | VCEO(sus) | 100 | V | |
| Collector Cut off Current(VCE = 50V, IB = 0) | ICEO | 2.0 | mA | |
| Collector Cut off Current ((VCB = 100V, IE = 0)) | ICBO | 1.0 | mA | |
| Emitter Cut off Current (VBE=5.0V, IC=0) | IEBO | 2.0 | mA | |
| DC Current Gain (IC=5.0A, VCE=4.0V) | hFE | 1000 | – | |
| (IC=10A, VCE=4.0V) | 500 | |||
| Collector-Emitter Saturation Voltage (IC=5.0A, IB=10mA) | VCE(sat) | 2.0 | V | |
| (IC=10A, IB=40mA) | 3.0 | |||
| Base-Emitter Saturation Voltage (IC=10A, IB=40mA) | VBE(sat) | 3.5 | V | |
| Base-Emitter On Voltage (IC=10A, VCE=4.0V) | VBE(on) | 3.0 | V | |
| Delay Time (VC=30V, IC=5.0A) | td | 0.15 (Typical) | us | |
| Rise Time (IB1 = -IB2 = 20mA) | tp | 0.55 (Typical) | us | |
| Storage Time (Duty cycle ≤2.0%) tp = 20µs, | ts | 2.5 (Typical) | us | |
| Fall Time |
How to Build:
To build a Simple CFL Driver Circuit you need to follow the below mentioned steps:
Gather Components:
Gather the required components as mentioned in the diagram.
Assemble the Transistors:
- Connect the two transistors in a crossed-coupled manner.
- Connect the base of the first transistor to the collector of the second transistor using a 2.2k resistor, and vice versa for the second transistor.
- Ensure the emitters are connected together.
Connect the Transformer:
- Connect the outer primary windings of the center tapped transformer to the collectors of the transistors.
- Connect the center tap of the transformer to the positive terminal of the battery or power supply.
- Connect the emitters of the transistors to the negative terminal of the battery or power supply.
Wire the CFL Lamp:
- Connect the secondary side of the transformer to the CFL lamp.
- Ensure the lamp is securely connected and insulated.
- Before fully assembling the circuit perform a basic test to ensure the transistors are switching correctly and the CFL lamp is lighting up.
- Use caution and ensure proper safety measures are in place.
Final Assembly:
- Once the circuit is tested and working finalize the assembly by securing all connections and insulating exposed wires.
Usage:
- Connect the circuit to a suitable power supply and test it with the CFL lamp.
- Adjust any component values or connections if necessary to achieve optimal performance.
Note:
- Please note that working with high voltages can be dangerous.
- If you are not familiar with electronics or unsure about any step seek assistance from someone experienced or consult a professional.
Conclusion:
A simple CFL driver circuit is an essential electronic circuit that converts input voltage from a power source into the appropriate form to power a CFL lamp.
The circuits main functions include stepping up the voltage providing the necessary current and ensuring efficient and safe operation of the CFL lamp.
Overall, these circuits are vital for enabling the energy efficient illumination provided by CFL lamps.
References:
General circuit diagram pattern for the CFL electronic ballast.
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