Wednesday, 2 April 2014

How to make a 0-300V Variable Voltage, Current Transformerless Electronic Power Supply or Driver Circuit.

How to make a 0~300v Variable Voltage & Current Transformerless Electronic Power Supply or LED Driver or Electronic Dimmer.


In this post i am going to show how to make a variable transformerless electronic Power supply or Electronic Dimmer means this power supply can vary  both voltage as well as current. This circuit can be of great importance like checking different appliances (samll as well as big appliances) without worrying about buying their power supply which is diffrent for different appliances. It can be used on any device....

One day when i was testing a led strip on  Electrical Dimmer or Auto-transformer ( which actually is a bulky circuit), due to its bulkiness i start thinking why not develop a Transformerless Electronic dimmer for ease of use. So i come up with this circuit.

I made this circuit, short circuit proof. so enjoy making this marvel piece of Gadget.

   0 ~ 300V Variable Voltage, Current Transformerless Electronic Power Supply or LED Driver or Electronic Dimmer circuit

 Working of above circuit

First of all the purpose of incorporating a 100watt bulb along mains is to make the circuit damage proof while short circuiting.
When mains voltage after passes through the 100watt bulb is being rectified through diodes(1amp/500v) bridge and then filtered through C1. Now T1 will come in role, Here T1 congigured as a source follower. The source of T1 interacts with the voltage of the the moving connection of preset or potentiometer(500k) R3 resistor. Here ZENER D2 is here to ensure that gate of T1 is safe and act as a safegurd.

Here the role of current limiter is performed by Transistor T2 and and Resistor R2. So whenever the current value exceeds above certain amount or excessively then T2 make the T1 DISCHARGE through gate. This arrangement limit the current from exceeding above certain amount. Here You must adjust the value of R2 which actually depends upon HFE of T1 and you have to find it experimentally.

Here in extreme cases the maximum current will be 100mA at 330v, So you have to choose a mosfet which can actually can handel 33watt(330v*100mA). Just use what i use for the sake of easy maintainance. Use BUZ 326 (400v/10.5A) or IRF 740 (400v/10A) and use a good HEATSINK to prevent overheating. 
For your kind information the bigger mosfet you choose the lesser impedence of output. Because impedence of output depends on Beta of Mosfet T1.

Thank you for reading.  

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