# DC-DC converter topology

Is it possible to build a DC-DC converter by means of a piezo crystal followed by a voltage multiplier? The crystal would supply the AC voltage needed by the voltage multiplier. I'm looking to get around 60~70 V from an Arduino 5V pin, and don't require much current(around 0.5mA).

Specifically, I'd use 5V to excite the crystal and use the AC output as the input of a voltage multiplier.

• How much is "not much" current? 1 nA or 1 mA, for example. Commented Jan 23, 2015 at 17:19
• Can you explain the relationship between DC-DC, piezo and arduino? It look totally unclear to me. Schematic would be preferable. Commented Jan 23, 2015 at 17:21
• Edited my initial question. Don't have a schematic yet, just trying to decide on the best approach Commented Jan 23, 2015 at 17:31
• So why do you need a piezo? Just generate a square wave from arduino itself... But really, use an external supply, don't risk your IO pins.. Commented Jan 23, 2015 at 17:42
• I could also use the supply I'm using to power the Arduino - point is, I only have 5V DC to work with Commented Jan 23, 2015 at 17:44

There are piezo "transformers" that do exactly what you suggest. Their output current is usually very low. I haven't ever looked at one in detail, so I'm not sure whether 500 µA is doable or not. One advantage is that they can have very high voltage step up ratios and be physically smaller than a normal magnetic transformer.

I've never used one, or even looked at a datasheet in any detail, so I can't help further. Look around on a distributor site like Mouser to see what's available, then peruse some datasheets carefully to see what is possible and what usage restriction there are.

That all said, getting 65 V from 5 V doesn't require anything exotic. Why not use a typical boost converter?

• I would do 5V to 65V with a flyback converter. Boost converters are not recommended for boost factors greater than 5x or 6x. Commented Jan 23, 2015 at 19:07
• @NickAlexeev: Obviously, your definition of "boost converter" is more narrow than "any circuit that produces a high voltage from a low voltage". To me, a flyback converter is just one way of implementing a boost converter. Commented Jan 23, 2015 at 19:47
• @DaveTweed Yes, I had a narrow definition of a "simple" inductive boost converter in mind. Commented Jan 23, 2015 at 19:54

If space is an issue I would use a voltage multiplier.

use schottky diodes and 100nF caps, the last cap should be 1uF. With 2 arduino pwm pins you can generate the complementary outputs that are needed.

If you have an external voltage source (12v or so) use some bss138 or 2n7000 to get the voltage you need with lower amount of stages.