# Converting small AC output voltage of a piezo element to DC without IC

I've been trying to find a AC to DC converting circuit that will take a piezoelectric crystal as its input. I have the piezo to a bridge rectifier but all the diagrams I am finding have some kind of an IC to help smooth out and regulate the voltage(3-5v output is what i'm looking for).

I'm trying specifically without an IC as I am using circuit simulating software that does not have the IC models i'm finding referenced.

ideally i can build this circuit in software before I buy parts.

Thanks!

• Piezoelectric crystals normally don't provide very much power. Can you elaborate on what kind of crystal it is and how you're stimulating it to produce a voltage? – Adam Haun Apr 8 '15 at 1:38

You want a zener regulator:

Software should have no problem simulating that. You do not need R -- piezo's internal resistance will be large enough.

You should consider using LTspice, a free circuit simulator from Linear Technology. In addition to the ICs that are sold by Linear Technology (which are built into the program), it is relatively straightforward to find models for other manufacturers' chips on the internet because the program has a very large user base. Many models can be found in the LTspice Yahoo! Group.

There is a reason for those ICs. http://cds.linear.com/docs/en/datasheet/35881fc.pdf does a lot more than a simple rectifier.

• the rectifier shall have a very small voltage drop
• the piezo does not produce a continuous power, so you need to store it somehow
• the piezo is definitely not produce the voltage you're looking for, so you need some sort of regulator. As the piezo voltage is usually lower, you need a step-up regulator, which is fairly inefficient to make from components. On the other hand, it is widely available as a ready made chip.

I suggest you to read up some material on energy harvesting of piezo elements - that will bring you a lot closer to your goals than to simulate a theoretical mechanical input to a theoretical piezo element and theroetically not processing the output properly.

(I am unsure if you can find a simluation environment for mechanical input to voltage conversion of a piezo, and I am unsure if you can find right data on your piezo to figure out its output waveforms at a specific load.)