Electronic – use more diodes to reduce the voltage off a diode bridge

acdiodesrectifiertransformervoltage

I have a transformer labeled as providing 9Vac, 3.36 A. It appears to provide 9.4 v ac according to my multimeter.

It runs through a diode bridge (WAB 040 diodes — already fried the last version), and at the output, I'm getting 11.3 v (which is consistent with 9.4v AC^2 – 2 diodes).

I'd like to bring this down under 9.5 v. Can I just attach two or three more diodes until the voltage is sufficiently low?

Obviously, each one is going to waste energy, but I'm not particularly concerned.

Best Answer

If your idea is to bring the output voltage down under 9.5V you can use extra diodes in series.

But the voltage regulation would be really bad even if you use large capacitors. Since the forward bias voltage of diode is a function of forward current, then the effect gets multiplied n times the number of diodes you have added. Not recommended to power semiconductor chips, Please use a proper regulator instead.

Vt    Vf1  Vf2   Vf3 
o----|>|---|>|---|>|---| Vo
                       \
                       /
                       \ RL
                       /
GND        If          |
o-----------<----------|

Vo = Vt - ( Vf1 + Vf2 + Vf3 );

Where,
  Vt is the voltage at positive terminal coming out of the birdge rectifier.
  Vf1, Vf2 and Vf3 are the forward biased voltage of Diodes.
  RL is the load resistance.
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