The post elaborately explains how to build a 3 simple LED bulb using many LEDs in series and powering them through a capacitive power supply circuit
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.
Simulation and Working 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 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.
R1 = 1M 1/4 watt
R2, R3 = 100 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 design 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
The LEDs in the above discussed LED lamp circuit can be also protected and their life increased by adding a zener diode across the supply lines as shown in the following image.
The zener value shown is 310V/2 watt, and is suitable if the LED light includes around 93 to 96V LEDs. For other lower number of LED strings, simply reduce the zener value as per the total forward voltage calculation of the LED string.
For example if a 50 LED string is used, multiply 50 with the forward drop of each LED that is 3.3 V which gives 50 x 3.3 = 165V, therefore a 170V zener will keep the LED well protected from any sort of voltage surge or fluctuations....and so on
Video clip showing an LED circuit circuit using 108 numbers of LED (two 54 LED series strings connected in parallel)
Simple LED Bulb using 1 watt LEDs.
A simple high power LED bulb can be built using 3 or 4 1 watt LEDs in series, although the LeDs would be operated only at their 30% capacity, still the illumination will amazingly high compared to the ordinary 20mA/5mm LEDs.
Moreover you won't require a heatsink for the LEDs since these are being operated at only 30% of their actual capacity.
In the videos above I have purposely flickered the LEDs by twitching the supply wire just to test ensure that the circuit is 100% surge proof.
Solid State LED Bulb Circuit with Dimmer Control using IC IRS2530D
A simple yet efficient mains transformerless solid state LED controller circuit is explained here using a single full bridge driver IC IRS2530D
Normally LED control circuits are based on buck boost or flyback principles, where the circuit is configured to produce a constant DC for illuminating an LED series.
The above LED control systems have their respective drawbacks and the positives in which the range of operating voltage and the number of LEDs at the output decide the efficiency of the circuit.
Other factors like whether the LEDs are included in parallel or series or whether they need to bedimmed or not, also affects the above typologies.
These considerations make these LED control circuits rather dicey and complicated.The circuit explained here employs a different approach and relies on a resonant mode of application.
Though the circuit does not provide direct isolation from the input AC, it has the features of driving many LEDs with current levels as high as 750 mA. The soft switching process involved in the circuit ensures greater efficiency to the unit.
How the LED Controller Functions
Basically the mains transformerless LED control circuit is designed around the fluorescent lamp dimmer control IC IRS2530D. The circuit diagram shows how the IC has been wired up and how its output has been modified for controlling LEDs in place of the usual fluorescent lamp.
The usual preheating stage required for a tube light utilized a resonant tank which is now effectively replaced by a LC circuit suitable for driving LEDs.Because the current at the output is an AC, the need of a bridge rectifier at the output became imperative; this makes sure that current is continuously passing through the LEDs during every switching cycle of the frequency.
The AC current sensing is done by the resistor RCS, placed across the common and the bottom of the rectifier.This provides an instant AC measurement of the amplitude of the rectified LED current.The DIM pin of the IC receives the above AC measurement via the resistor RFB and capacitor CFB.
This allows the dimmer control loop of the IC to keep track of the LED current amplitude and regulates it by instantaneously varying the frequency of the half bridge switching circuit, such that the voltage across the LED maintains a correct RMS value.
The dimmer loop also helps to keep the LED current constant irrespective of the line voltage, load current and temperature changes.Whether a single LED is connected or a group in series, the LED parameters is always maintained correctly by the IC.
Alternatively the configuration may also be used as a high current transformerless power supply circuit.
Original article can be found here