High Current Transformerless Power Supply Circuit

The simple configuration of a transformerless power supply circuit presented below is able to provide high current at any assigned fixed voltage level. The idea seems to have solved the problem of deriving high current from capacitive power supplies which earlier seemed a difficult proposition. I assume I am the first person to have invented this.

I have discussed a few transformerles power supply circuit in this blog which are good only with low power applications, and tend to become less effective or useless with high current loads.

The above concept utilizes high voltage PP capacitors for dropping the mains voltage to the required level,  however it is unable to raise current levels as per any desired particular application.   

Although, since the current is directly proportional to the reactance of the capacitors, means the current can be lifted just by incorporating more capacitors in parallel. But this puts a risk of high initial surge currents which might destroy the involved electronic circuit instantly.

Therefore adding capacitors might help to increase the current specs of such power supplies but the surge factor must be first taken care of for making the circuit feasible for practical usage.

The circuit of a high current transformerless power supply explained here hopefully, effectively handles the surge developing from power transients such that the output becomes free from the dangers, and provides the required current supply at the rated voltage levels.

Everything in the circuit is kept just as its old counterpart, barring the inclusion of the triac and zener network which  actually is a crowbar network, used for grounding anything that goes above the rated voltage.

In this circuit the output would hopefully provide a stable voltage of around 12+ volts at around 500 mA of current without the dangers of any accidental voltage or current influx.

CAUTION: THE CIRCUIT IS NOT ISOLATED FROM MAINS AND THEREFORE INVOLVES HIGH RISK OF ELECTROCUTION, APPROPRIATE PRECAUTION NEEDS TO BE EXERCISED.

Parts List

R1 = 1M, 1/4W

R2,R3 = 1K, 1/4 WATT

C1----C5 = 2uF/400V PPC, EACH

C6 = 100uF/25V

All DIODES = 1N4007
Z1 = 15V, 1 watt

TRIAC = BT136


Update (August 22, 2014)

A deeper analysis of the circuit showed that the triac was dumping a significant amount of current while restricting the surge and controlling the current.

The approach taken in the above circuit for controlling voltage and the surge is negative in terms of efficiency.

In order to obtain the intended results as proposed in the above design and without dumping precious amps, a circuit with exactly opposite response needs to be implemented, as shown below:

Interestingly, here the triac is not configured to dump power rather it's wired in a such a way that it switches OFF power as soon as the output reaches the specified safe voltage limit, which is detected by the BJT stage.

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