Universal Design, Developed by Swagatam
You just have to adjust the pot to set the output according to the total forward drop of the LED series string.
Meaning, if the total voltage of the LED series is say 3.3V x 50nos = 165V, then adjust the pot to get this output level and then connect it with the LED string.
This will instantly illuminate the LEDs at full brightness and with complete over voltage and over current or surge inrush current protections.
R2 can be calculated using the formula: 0.6 / Max LED current Limit
Improving the above Design
Although the above simple current controlled MOSFET LED driver looks easy and safe for illuminating high watt LEDs, it has one serious drawback.
The MOSFET can generate a lot of heat if the output is adjusted for low voltage LED strings.
The heat dissipation is basically due to the bridge rectifier and the C1 which converts the full AC cycle to DC, causing a lot of stress on the MOSFETs.
This aspect can be improved drastically by replacing the bridge rectifier with a single diode and moving the C1 capacitor parallel to the output LED, as shown in the following diagram:
In the above diagram due to the presence a single diode D1 only half AC cycles are delivered across the MOSFET, causing 50% less stress and heat dissipation on the MOSFET.
In the above diagram due to the presence a single diode D1 only half AC cycles are delivered across the MOSFET, causing 50% less stress and heat dissipation on the MOSFET.
However, the capacitor C1 parallel to the LED string ensures that the LED keeps getting the required power even during the absence of the other AC half cycles.
You can add more number of LEDs in series, a maximum upto 300 / 3.3 = 90 LEDs.
Make sure to adjust the P1 pot accordingly to adjust the output voltage to match the LED string's max forward voltage.
Likewise. adjust the base/emitter resistor of T2 (BC547) to match the LED max current spec.
Why use LEDs
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.
The circuit of a LED bulb explained here is very easy to build and the circuit is very reliable and long lasting.
The reasonably smart surge protection feature included in the circuit ensures an ideal shielding of the unit from all electrical power ON surges.
How the Circuit Functions
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 reactance value is optimized 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.
Universal Design, Developed by Swagatam
You just have to adjust the pot to set the output according to the total forward drop of the LED series string.
Meaning, if the total voltage of the LED series is say 3.3V x 50nos = 165V, then adjust the pot to get this output level and then connect it with the LED string.
This will instantly illuminate the LEDs at full brightness and with complete over voltage and over current or surge inrush current protections.
R2 can be calculated using the formula: 0.6 / Max LED current Limit
Improving the above Design
Although the above simple current controlled MOSFET LED driver looks easy and safe for illuminating high watt LEDs, it has one serious drawback.
The MOSFET can generate a lot of heat if the output is adjusted for low voltage LED strings.
The heat dissipation is basically due to the bridge rectifier and the C1 which converts the full AC cycle to DC, causing a lot of stress on the MOSFETs.
This aspect can be improved drastically by replacing the bridge rectifier with a single diode and moving the C1 capacitor parallel to the output LED, as shown in the following diagram:
In the above diagram due to the presence a single diode D1 only half AC cycles are delivered across the MOSFET, causing 50% less stress and heat dissipation on the MOSFET.
In the above diagram due to the presence a single diode D1 only half AC cycles are delivered across the MOSFET, causing 50% less stress and heat dissipation on the MOSFET.
However, the capacitor C1 parallel to the LED string ensures that the LED keeps getting the required power even during the absence of the other AC half cycles.
You can add more number of LEDs in series, a maximum upto 300 / 3.3 = 90 LEDs.
Make sure to adjust the P1 pot accordingly to adjust the output voltage to match the LED string's max forward voltage.
Likewise. adjust the base/emitter resistor of T2 (BC547) to match the LED max current spec.
Why use LEDs
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.
The circuit of a LED bulb explained here is very easy to build and the circuit is very reliable and long lasting.
The reasonably smart surge protection feature included in the circuit ensures an ideal shielding of the unit from all electrical power ON surges.
How the Circuit Functions
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 reactance value is optimized 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.
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