some Questions about Transformerless power supply and Zener diode.

[Qaisar Azeemi]

What is the basics of Transformerless power supply?

Secondly at how much high voltages a Zener diode can work?

Can i use two 15V zener diodes at 220V and get 30Vp-p signal and pass it Through Bridge rectifier and then to Capacitor to make smooth dc of 30V?
and the supply should be capable of providing up to 5A or more current.

Thank you

 

[papunblg]

For your need the steps should be as follows:-
AC Mains-->Step Down--->Rectifier-->filter + Regulator

A zener diode can be used with AC source but the result is different from what you need.


Zener diodes are available in a wide variety of zener voltages and power ratings. The voltage range from less than 2 volts to a few hundred volts while power ratings run from less than 0.25Watts to 50 watts.

Power dissipation in a zener is very important for its health.


For Practical designs,

Value of series resistance R_s=(E_DC(min)-E_z)/1.1 I_L(max)

When R_s is known, maximum power dissipation is calculated as,

P_D=[(E_DC(max)-E_z)/R_s)-I_L(min)]E_z

Its possible to combine a low power zener with a high power Transistor to simulate a high power zener.

Two zener diodes can be connected in series to get higher regulated voltages. Since the current through the two series connected diodes is same, the power dissipated in each zener depends on its zener voltage.



The efficiency of Zener regulated power supply becomes very low when the load current is high. Under such conditions a Zener controlled transistor is always used for maintaining output voltage constant. Basically there are two types of Zener controlled transistor voltage regulators. They are

■Series Voltage Regulators
■Shunt Voltage Regulators.

For details see Zener Controlled Transistor Voltage Regulators - Electronic Circuits and Diagram-Electronics Projects and Design

Please note that a Transformer less powersupply is not isolated from AC mains. the circuit must be treated with caution and encosed at all times. Do not work on the circuit (or any other circuits attached to it) when it is plugged in.
For idea only, you may check: Transformerless Power Supply

or
Transformerless AC to DC power Supply

A Transformer less powersupply is used for very low power application.