DC-DC Converters

It’s easy to generate DC voltages greater than 12 -13.6 VDC; or if you…

need a regulated -15 VDC,  or so for the time base in a spectrum analyzer or sweeper time base. Just ensure you apply correct capacitor and diode polarity. Ply 3 terminal or zener diode regulators as required.

Here’s some circuit examples:

DC-DC converter using a diode “tripler”. I sought 28 VDC to tune some SMT varactors.

dc-convert

Here’s some scope traces (square edges very desirable):

clock-out

bases

emitters

My final version:

f-dc-convert

I applied some Schottky rectifier diodes in my final version to reduce diode drop losses and allow shunt resistor regulation.  With ideal components and no load you should technically get 3 * 12.3v = 36.9 volts.  In reality, I got 33.2v because of diode drops, transistor saturation and losses which multiply as the voltage is stepped up. With the shunt 2K7, I measured a low ripple 28 VDC output. I’m happy.

A useful link that shows a bevy of diode doublers/triplers etc.

http://n5dux.com/ham/files/pdf/Voltage%20Converters.pdf

My Bench Adjustable DC-DC Generator   (~24-30 VDC output into a load)

Another way to go —  chop an inductor:

Design credit goes to Matjaž, S53MV — permission to use this circuit comes from Andy Barter @ VHF Communications  http://www.vhfcomm.co.uk/

dc-dc

dc-con

dc-con-bb

My regulated bench supply for applying reverse DC voltage to varactors in circuit under test.

Finally — a cool Bob, K3NHI design using a 600 Ω  AF transformer Mouser # 42TM028-RC . Long live the multivibrator!

bobs

I used this stage in the USG — Utility Sweep Generator for Bob Kopski’s sweep system. The USG produces an amazingly sharp triangle wave.

k3nhi sweeper system

scope_17offset-ad8307

Bob’s also clever with generating a little negative DC voltage with a diode.  That’s my power meter for use with his sweep system.

Best!

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