Voltage regulation using Zener Diode when RF Power is feed at input

[ajeetpal]

Hi All,

I am designing a Voltage Regulator of 3.3 Volt. Input is the RF Power and using the rectifier circuit I am getting around 6 volt DC signal after rectifier circuit. But when I am placing the Zener diode then it is not regulate at 3.3 volt. So please give me some suggestion then i'll get the regulated output...

Thanks in advance....

 

[pranam77]

If it is a DC signal what you are getting after converting the RF, and your zener is actually a 3.3volts and not more, it should naturally regulate at the specified level.
Cheers

 

[jayce3390]

What happened when you put the Zener diode? Please post the circuit schematic.

 

[ajeetpal]

I am getting a 2-2.9 volt across the zener when varying the rf power from 2dB to 16dB (output voltage after rectifier varies 2- 6 volts).

 

[jayce3390]

Did you put decoupling capacitors at input/output? Again, post the circuit to get a valid answer.

 

[123jack]

What they said - but also try:

Do you need to use current limiting - is your circuit able to supply
sufficient current to keep the zener running - have you put a scope
on the line - is it clean and stable - what load is on the circuit - do you
have reservoir caps in place etc.

jack

 

[jiripolivka]

Low-voltage Zeners like yours typically do not regulate so well like higher-voltage Zeners.
Depending upon the Zener current, the output voltage may vary over certain limits. It may be said that by adjusting the current you could adjust the output voltage.
Now, as you rectify a RF power, this source may be "soft" and the load current of your detector may be too low to push a reasonable current through your Zener over the dropping resistor.
If you wish to have a better-regulated output, use rather a regulator IC like 7805 for 5V output, or there are many other IC regulators that can be used.
Also, take care to use filter capacitors around your regulator, to prevent the RF affecting it.