Simple LED Bulb Circuit


LEDs are being Incorporated in vast magnitudes today for everything that may involve lights and illuminations. White LEDs have especially become very popular due to their mini size, dramatic illuminating capabilities and high efficiency with power consumptions.

In one of my earlier post I discussed how to make a super simple LED tube light circuit, here the concept is quite similar but the product is a bit different with its specs.

Here we are discussing the making of a simple LED bulb CIRCUIT DIAGRAM

By the word “bulb” we mean the shape of the unit and the fitting secs will be similar to that of an ordinary incandescent bulb, but actually the whole body of the “bulb” would involve discrete LEDs fitted in rows over a cylindrical housing.

The cylindrical housing ensures proper and equal distribution of the generated illumination across the entire 360 degrees so that the entire premise is equally illuminated.

The image below explains how the LEDs needs to be installed over the proposed housing.

Image credit: http://www.sharplumi.com/en/userfiles/20100913191605380.jpg

Circuit Description

The circuit of a LED bulb explained here is very easy to build and the circuit is very reliable and long lasting. The exclusive surge protection feature included in the circuit ensures an ideal shielding of the unit from all electrical power ON surges.

The diagram shows a single long series of LEDs connected one behind the other to form a long LED chain.

To be precise we see that basically 40 LEDs have been used which are
connected in series. Actually for a 220V input, you could probably
invorporate around 90 LEDs in series, and for 120V input around 45 would
suffice. These figures are obtained by dividing the rectified 310V DC
(from 220V AC) by the forward voltage of the LED. Therefore, 310/3.3 = 93 numbers,
and for 120V inputs it’s calculated as 150/3,3 = 45 numbers. Remember
as we go on reducing the number of LEDs below these figures, the risk of
switch ON surge increases proportionately, and vice versa.

The power supply circuit used for powering this array is derived from a high voltage capacitor, whose low reactance is exploited for stepping down the high current input to a lower current suitable for the circuit.

The two resistors and a capacitor at the at the positive supply are positioned for suppressing the initial power ON surge and other fluctuations during voltage fluctuations.

In fact the real surge correction is done by C2 introduced after the bridge (in between R2 and R3).

All instantaneous voltage surges are effectively sunk by this capacitor, providing a clean and safe voltage to the integrated LEDs at the next stage of the circuit.

CAUTION: THE CIRCUIT SHOWN BELOW IS NOT ISOLATED FROM THE AC MAINS, THEREFORE IS EXTREMELY DANGEROUS TO TOUCH IN POWERED POSITION. 

LED bulb circuit using transformerless power supply

Parts List

R1 = 1M 1/4 watt

R2, R3 = 50 Ohms 1watt,

C1 = 474/400V or 0.5uF/400V PPC

C2, C3 = 4.7uF/250V

D1—D4 = 1N4007

All LEDs = white 5mm straw-hat type

input = 220/120V mains…

The above LED bulb lacks a genuine surge protection feature and therefore could be severely prone to damage in the long run….in order to safeguard and guarantee the design against all sorts of surge and transients, you can refer to the following concepts and implement any one of these in the above simple design:

Using an NTC Thermistor as a Surge Suppressor

SCR Shunt for Protecting Capacitive LED Driver Circuits
High Power Zener Diode Circuit

Simple LED Lamp for Home Decor, Made by Using Ordinary LEDs, Powered by a 12V AC/DC Adapter:

 The following images were sent to me by one of the keen followers of this blog Mr.Ishaan Pathania. The shown prototype of a simple LED lamp was built and tested successfully by him: