Transformerless Power Supply

transformerless power supply

Transformerless Power Supply Circuit

Transformers are indispensable in the field of electronics. But the need for a bulky and expensive component like a transformer can be eliminated in circuits involving low current chips, by utilising the circuit presented here. Finding a way to reduce the overload of electricity that a device has to draw and then convert via a transformer is beneficial for the home, especially if you make use of a pay as you go electricity plan for your home. Saving money on your electricity is important for those families who need to keep money expenses low, with various power saving equipment, and finding better ways to use their electricity that works for them this can be achieved, looking at all areas of saving electricity can help those in the long run. It also makes products that use this circyuitry more viable in the home situation.

In addition to being compact and versatile,this circuit is also low cost and capable of supplying almost any voltage ranging from 3 to 24 volts by selecting suitable component values.The Output is sufficiently regulated.

transformerless power supply circuit

Fig.1. single polarity DC power supply

Fig. 1 shows a single polarity DC power utilises R1 as a series dropper.D1 rectifies the voltage obtained through R2, while D2 stabilises the output to the specified voltage.C1 filters the output.

R1 100K
R2 (see table) 10W
C1 (see table) 25V
C2 0.22µF
D1 IN4001
D2 (see table) 250mW

some ICs require a dual DC power supply.For this purpose, the circuit shown in Fig. 2 may be used.R1 drops the voltage . which in turn is rectified by D1. D2 stabilises the voltage and C2 filters it.The polarities of D1, D2 and C1 are reversed to obtain a negative voltage.Neon lamp indicates the presence of the mains.

transformerless dual power supply circuit

Fig.2. Dual polarity DC power supply

Values of R2, C1, and D2 Depend on the output voltage required (see table)

Both circuits are capable of providing 25mA current, They continue to provide the specified voltage even if the mains voltage varies from 195 to 270 volts. Suitable component selection table given here.

Component Selection Table
V Out R2 D2 C1
3V 15K 3V 220µF
6V 12K 6.2V 220µF
9V 10K 9V 220µF
12V 10K 12V 470µF
15V 10K 15V 470µF
18V 10K 18V 1000µF
24V 8.2K 24V 1000µF

The circuit can be used with low current ICs.The circuit has been successfully tested with with ICs like UM3482, UM3484, UM66, UM3561, UM3562, NE555, LM741, LM748 and LM556.the circuit is capable of providing around 25 mA current.

The current supplying capability may be enhanced to about 40-50 mA by using a 5.6k, 2oW resistor as R2. However, this would require the use of at least a 1-watt zener diode.

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