[Concept] DC DC Voltage Multiplier and Co.

Hi everyone, hope you’re surviving the coldness of winter °3°

Today i will talk about a concept that I’ve built a few month ago about voltage conversion.
I was in the need of an high voltage source but could only afford a low voltage supply. In the field of well-known High Voltage converters there are a bunch of heavy transformer, expensive DC Boost converters (but very stable and with a good current supply) and pure Voltage multipliers.

Finally, I’ve chose the third option (In the end, I’ve mainly combined the two last options..) which is designed for simple a DC DC Conversion, exactly what i want.

For example, the main schematic for  a “Dickson Bridge” works like this :

dickson_voltage_multiplier-svg
Dickson Voltage Multiplier Bridge (from wikipedia)

It’s an multiplier bridge that you can (quite) extend at will . That voltage multiplier  do the job by adding the voltage supply value at each step.
For example, if you bring a 5 volts supply with 5v-Ov complementary oscillations on a 4 step bridge you will have 20 volts on the output :

 

dickson_voltage_multiplier2
The capacitor could be around 0.1 µF and the Oscill. at 500kHz

An easy what to manage the oscillation and make them complementary is an “Astable” oscill. like the NE555 with two OP-Amp on the output.
The first OP-Amp will have Vcc/2 on the “+” and the second one on the “-“, so when the square-wave comes they will react in a complementary way.

comp
Even if it’s not on the schematic, don’t forget the regulation capacitors (between supply and Gnd) after V1 and V1/2 and before U1(+) and U2(+) 😉

As always , we can search for new ways of using this concept !

For example, the two OP-amp could have an  5v-0v in input (with the 5v/2 comparator-limit) BUT be supplied in 40v – 0v. That will produce a medium voltage oscillation (38v-2v [because an comparator output equals approx Vsupply – 0v]) that can manage a 40v bridge-supply  with only a single 5v input (be careful of the Slow Rate !) .

It allows you to keep you’re (5v) NE555 for your wave-generation instead of building a complex high voltage oscillator.

With a x4 Dickson Bridge it will bring 160v (approx.) on the output !

image3398

But keep in mind that the system is not a current supply so don’t expect much more than 10mA (depends of the capacitor)

Also, if you put a resistor on the output, the output-capacitor will discharge in it, so you need to have a good value for your capacitor and a good frequency oscillation if you don’t want to have spikes instead of a flat DC output (but in involve less multiplication step because the system is slower !).

Hope that gives you some ideas !

 

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