Transformerless supply

About the device in general

Many small electronic applications do not require transformer supply and can operate easily with this transformerless power supply. In many cases, while small projects are developed, the price of the conventional transformer supply can be considerably higher then the actual project. Usually the transformerless supplies are developed for 5-15mA consumption. They are very cheap and consist of only few elements. The price is approximately three times less then the transformer supply for the same requirements. Also using transformless supply we can reduce significantly the weight of the final device. In some applications this is very important issue. Also transformerless supply can be used where the magnetic field (coming usually from the transformer) is necessary to be reduced. The present difficulties in using this kind of supply are mainly two:

• The power of transformerless supply is small (around 15mA)
  
  
• The voltage on the output of the supply can be the same as your application requires - usually low voltage such as: 5, 10, 12 or 24V. However, touching any not isolated part of the project can be life threatening because no one of the poles (+ or -) is earthed. This problem is typical for transformerless supply and can be corrected adding small transformer 1:1 (low voltage) into the circuit.

Application