Sunday, 4 May 2014

Simplest 5V Transformerless Power Supply Circuit

How to make Simplest Transformerless power supply for low current and low voltage application(5volt 150mAmp) using a IC-LR645

Some of the followers of this blog have requested to post a simple low current and low voltage i.e 5volt & 100mAmp. So today i am going to post an transformerless power supply which is not only easy to construct but also very cheap and small or compact electronic circuit. This electronic circuit can be used to for various purpose like charging small li-ion batteries e.t.c. In this circuit we are going to use IC-LR645 which can control any voltage between 24 and 270 V AC and produces DC voltages below 15 volts at the output, which becomes ideally suitable for operating condition.

The great thing about this circuit is that it does not include or incorporate any bulky transformer but it also dont uses high voltage polar capacitors here. So no worries about surge current and we don't need crowbar protection circuit here.

Components required:

Diodes - 1N4007

Input Capacitor - 4.7uF/400V,

Output Capacitors are 1uF/25V

ICs are LR645LG and 7805,

FET - DN2540N5

Using IC-LR645G the maximum current available from this device is quite low, around 3 mAmp, however that is not a problem, because the current can be shot up to 150 mA, through a simple addition of an  FET DN2540N5 in the circuit.

simplest transformerless electronic circuit or schematics 5volt 150mAmp

The figure shown above is a great circuit set up of a transformer less power supply circuit which can provide an outputs of 15 volts and 5 volts.
15 volts is available just at the junction of the output of IC-LR645 and the input of IC-7805.
Here if 5 volt option is not required, then configuration around the 5 volt regulator may be just eliminated, which makes the circuit more simpler and compact.

Here the high voltage AC mains is rectified by the bridge configuration  at the input. 
then the voltage required is filtered by the filter capacitor introduced at the output of the rectifying network configuration. Then the smooth filtered rectified high voltage output is fed to our IC-LR645LG, which reduces the output voltage from ic to 15volt and 3mAmp. Now the FET pulls the 3mAmp current value to 150mAmp and fed it to the next stage which include the 5volt regulator stage.

One of the big drawback of eliminating the transformer is the DANGER of high voltage shock that actively hangs with all the naked points of the circuit. Therefore extreme caution must be taken care while building and testing this circuit.

Thank you for reading.

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