Designing a Simple 7W LED Bulb Circuit

Since LED lights last longer and use less energy than conventional incandescent bulbs, they are growing in popularity.

This article will describe how to build and use a basic circuit for a 7W LED bulb using the following parts: a 230V AC power supply, a Metal Oxide Varistor (MOV), capacitors, resistors, bridge rectifiers, Zener diodes, and capacitors.

When working with high voltage circuits, always make sure that safety precautions are in place since the circuit is powered by 230V AC.

Circuit Working:

Parts List:

Handle this circuit with utmost caution as it works at a high AC voltage of 230V AC.

The 230V AC supply is connected to the MOV to start the circuit.

This part guards against spikes in voltage that can harm the circuit.

A resistor R1 and a capacitor C1 are used to restrict the 230V AC mains supply.

These parts set a limit on the voltage and current, which a bridge rectifier then corrects.

In doing so, the AC voltage is changed into a DC supply.

The AC voltage is delivered into the bridge rectifier subsequent to the MOV.

The AC voltage is converted into pulsing DC by the bridge rectifier.

This stages output wont be smooth, hence filtering is necessary.

To guard against high voltage surges in the circuit, a varistor VR1 is employed.

Capacitor C2 filters and a reverse biased Zener diode regulates the DC supply from the bridge rectifier.

After being linked in series, one-watt white LEDs or warm, highly bright 8mm white LEDs are connected to the output terminals over the Zener diode.

We are able to change how many LEDs are in the array in accordance with our needs.

Check to verify that the anode and cathode terminals are appropriately aligned before attaching the LEDs.

Formulas:

A basic 7W LED bulb circuit requires the design of many essential parts, each of which has a unique formula for selection and size.

The crucial calculations and factors to take into account for every part in your circuit are listed below:

Capacitor C1 AC Coupling Capacitor:

Reactance (X_C): X_C ​= ​1​ / 2πfC₁

where,

• f is the frequency around 50Hz or 60Hz
• C1​ is the capacitance in Farads

Choose C1 to limit the current through the bridge rectifier:

I = V_ac​​ / X_C​

Resistor R2 Current Limiting Resistor:

Use Ohms law to determine R2:

R_2​ = V_ac​​ / I_desired​

Choose Idesired based on the desired current through the rectifier.

Filter Capacitor C2:

To calculate the capacitance needed to minimize ripple voltage (V_ripple):

C₂​ = ​I_LED​​ / f × V_ripple

where,

• ILED​ is forward current of the LED string
• f is the frequency of the ripple which is twice the AC frequency for full-wave rectification.

Zener Diode Resistor R3:

The resistor R3 limits the current through the Zener diode:

R₃​ = ​V_Zener​ − V_LED​​ / I_Zener

where,

• VZener​ is the breakdown voltage of the Zener diode
• VLED​ is the forward voltage drop of the LED string
• IZener​ is the desired Zener current which is often around 10-20mA

LED String 7 LEDs in Series:

Total forward voltage (V_total):

V_total​ = N_{LED ​}× V_LED​

where,

• NLED is 7
• VLED is 2.1V

Resistor R1 Parallel to C1:

Used for discharging capacitor C1 safely:

R1​ (choose based on desired discharge time):

τ = R1​ × C1​

where,

•  τ is the time constant

These formulas offers a basic understanding that will help you construct your circuit for a 7W LED bulb.

When dealing with AC mains voltage, always be sure to check the component ratings and take safety measures.

How to Build:

Designing a Simple 7W LED Bulb Circuit following are the steps to follow for connections:

• Assemble all the components as shown in the above circuit diagram.
• Connect RV1 varistor parallel to the input of 230V AC supply.
• Connect one AC terminal of bridge rectifier with one input of AC 230V through C1 capacitor.
• Connect the other AC terminal of the bridge rectifier with the other input of the AC 230V through R2 resistor.
• Connect a filter capacitor C2 across the positive and negative outputs of the bridge rectifier.
• Connect the cathode of the Zener diode to the positive of the bridge rectifier through the resistor R3.
• Connect the anode of the Zener diode with the negative output of the bridge rectifier.
• Connect the positive terminal of the LED string consisting of 7 LEDs in series with the junction of R3 and the cathode of Zener diode.
• Connect the negative end of LED string with the GND.
• Connect the resistor R1 parallel to capacitor C1

Safety Measures:

• Make use of enclosures and wiring that are well-insulated to avoid unintentional contact with active parts.
• Opt for components rated higher than 230V to prevent malfunctions and guarantee secure functioning.
• To securely reroute stray currents and lower the danger of shock, provide adequate grounding.
• Limit current with resistors to avoid overheating and possible fire.
• LEDs are shielded from overvoltage by zener diodes, which aid in voltage regulation.
• To increase knowledge about the risks associated with high voltage, clearly mark circuits and provide warnings.
• To make sure the design satisfies safety criteria, adhere to electrical safety regulations.

Conclusion:

This article for designing a simple 7W LED bulb circuit is a useful and efficient method of creating energy saving illumination.

The circuit may provide reliable performance and safeguard delicate components by employing elements such as the MOV, Zener diode, and appropriate filtering and current limiting methods.

These circuits show off the adaptability and advantages of utilizing LEDs in contemporary lighting solutions in addition to providing energy efficient illumination.

When handling high voltage circuits, safety and following local electrical codes should always come first.

References:

Simple Battery to LED Bulb Hookup