The article explains a simple single IC LED tube ligt circuit applicable for 110V/120V AC inputs. The circuit uses 30 numbers of 1 watt LEDs, and also includes a voltage and current control features.
In my previous post I discussed the IC TL783 which is a 1.25V to 120V variable DC regulator IC. We learned how this IC could be configured for acquiring the specified adjustable outputs.
Here we employ the same basic configuration for making a simple 120V compact current controlled LED tubelight circuit.
Circuit Operation
Referring to the 120V compact tube light circuit shown below, we can see the fundamental design incorporating the IC TL783 with the addition of a current control stage made around a single NPN transistor BC546.
30 nos of 1 watt high bright LEDs can also be seen connected across the output of the circuit. All the LEDs are connected in series.
The transistor BC546 along with its base/emitter 2 ohm resistor forms a classic current control stage.
It ensures that the current to the LEDs can never exceed the 300mA limit, which is quite enough for providing an optimal glow over the LEDs.
Before connecting the LED string to the circuit output via the switch S1, the 100k pot should be adjusted to produce exactly 100V across the specified output terminals of the circuit, before or at the left of S1.
Once this voltage is ascertained, S1 may be pressed ON for integrating the LEDs with the circuit.
The above setting ensures that the LEDs are subjected to the correct 3.3V per LED spec and at a current of 300mA.
20 Watt is Equal to 40 Watt
The overall illumination level of this 120V compact transformerless tubelight circuit would be equivalent to a 40 watt fluorescent tubelight.
The 100k pot could be also used for reducing the brightness of the "tubelight", however be sure you don't accidentally increase the voltage above 100V...although this won't damage the LEDs due to the current control feature being present, it's not recommended.
The IC TL 783 will require a good heatsink for enabling optimal results.
This circuit cannot be used in countries with 220V AC Mains specification.
Circuit Diagram
Warning: The circuit explained below is not isolated from mains AC, and therefore are extremely dangerous to touch in the powered and open condition. You should be extremely careful while building and testing this circuit, and make sure to take the necessary safety precautions. The author cannot be held responsible for any mishap due to any negligence by the user
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