DC to DC converter ( source, or circuit diagram) - Page 1
Forum section: electronics / projects

author: TheKraken
author_rank: Newbie
timestamp: July 02, 2013, 05:15:01 am
content: Now I know that a normal dc-dc boost converter is a fairly straight forward thing, and I could find many online. My problem, or more so my curiosity is in finding where I could get a relatively cheap dc to HV dc boost converter, or at least a basic circuit diagram to work from. This has always puzzled me, and I know there are ways to get my hands on circuits that do this ( camera flashes for instance ) but I am curious how I would go about designing a specific voltage booster. 400v would be ok, 600v-800v would be more along the lines of what I'm looking to find. Or even a reputable source for circuits of this nature. dc- dc via inductor ( though i do not believe this to be the best or most feasible) or dc->ac->rectified dc. A concern would be size of the overall circuit if sourced, would like something within 2x2...2x4 give or take, theres some room to work here most definitely.The trouble I'm having is finding a way to get a small scale inverter ( I have a standard 12vdc-110vac inverter but its bulky ) that could be rectified, but thats not what im curious or interested in finding. A higher voltage then a 120/240 standard in the ranges above ( really anywhere from 400v-800v maybe higher if its easier to source/find a diagram ). Input voltages could be...1.5v (or multiples) 3.7v ( or multiples ) 9v ( but would not prefer ) or 12v but this is only after the fact thoughts here, I could in essence purchase many types of DC sources to power the circuit so this isn't a necessary, but a strong preference. Output amperage is a trivial concern currently ( pardon the pun ).

author: Paul Price
author_rank: Super Contributor
timestamp: July 04, 2013, 04:04:26 pm
content: Pretty simple to make a very simple fly-back boost converter, just takes a toroid inductor, a HV n-MOSFET, a HV fast-recovery diode, a 555 timer, a few resistors and caps to get 800V or more at low current, and this circuit could be quite small, with the transformer taking up most of the space. The higher the input battery voltage, the better, so as to convert say, 12V to 800V DC.

author: rbola35618
author_rank: Frequent Contributor
timestamp: July 04, 2013, 05:38:40 pm
content: With a high turn ratio, the winding ration will give you a high leakage that maybe an problem. A better solution is to keep the voltage down and use a series of diode multipliers like the one that Dave lectured on. We use that technique in our high voltage designs. We always try to keep the voltages in the transformer to 300 to 400 volts. That will make for a much more reliable transformer.Hope this helps,Robert B

author: TheKraken
author_rank: Newbie
timestamp: July 05, 2013, 02:33:25 am
content: Ahh, thanks guys. I have been a bit curious about whether utilizing multiple circuits for voltage boosting would work, also was a bit 'iffy' on what sort of transformer to use. Ill look more into the 555 timer circuits. Is the 555 the only way to get the oscillation for the ac current?

author: poorchava
author_rank: Super Contributor
timestamp: July 05, 2013, 06:03:38 am
content: No, there are tons of others:-schmitt inverter oscillator-ring oscillator-some decidated 7400 and 4000 series chips-various pwm controllers with TL494 on the very top-microcontroller (there are 8-bit ones out there that have ADCs, comparators and whatnotThe best ratio of features for cost seems to be 555 timer in astable mode with feedback realized as BJT driven from divided down output voltage and pulling down the CV pin on the 555.You can do kind of the same thing with schmitt oscillator, by discharging the capacitor by a mosfet/bjt driven from divided down output voltage.

author: Paul Price
author_rank: Super Contributor
timestamp: July 05, 2013, 08:39:00 am
content: The 555 is just a drive signal to a bjt or power MOSFET, the actual voltage conversion work is done by the bjt or MOSFET kicking current into an inductor an then, in just a few nano seconds abruptly opening the bjt /MOSFET switch. This cause the voltage to rise at the inductor for an instant very very high. This effect is called flyback. This high voltage is shunted away from the switching transitor/MOSFET by a HV fast-recovery diode to charge a HV capacitor at a very high voltage.So the idea is to, with very short on-time kicks, kick current pulses into the inductor and then harvest the HV pulse result with a diode.This is how your ignition system works in your car to develop AC HV to spark your plugs and a 12V car battery develops 15-25 KV this way.You could look into ULN2524 ULN3844 circuits, but I mentioned the 555 because it is cheap, it can bully around a MOSFET to get HV pulses.

author: Psi
author_rank: Super Contributor
timestamp: July 05, 2013, 09:11:28 am
content: The quickest to build would be a 555 timer feeding 2 transistors to produce 12V 50hz AC.Feed that into a generic 12V:230V transformer with a 3 stage voltage doubler on the output.That would get you 690V quite easy with parts you probably already have.12V to 230Vhttp://electrosuite.com/converter/5-vdc-to-240-vac-converter.htmlVoltage doubler/multiplierhttp://en.wikipedia.org/wiki/Voltage_multiplier

author: TheKraken
author_rank: Newbie
timestamp: July 12, 2013, 12:55:57 am
content: Awesome, Thanks for the links. I have almost everything on hand except for the inductor, diodes and the 2700uF cap. Though i might be able to find some around here its a pain to look up all the part numbers on parts that I dont need. Did find a 555 timer laying around though =P.Thanks for you help!

author: mariush
author_rank: Super Contributor
timestamp: July 12, 2013, 01:05:57 am
content: The Signal Path Blog author had a series of youtube videos in which he described how the camera flash circut works and how to adapt it to power nixie tubes.Maybe you'll find the series informative:

author: PA4TIM
author_rank: Super Contributor
timestamp: July 12, 2013, 11:36:49 pm
content: http://www.pa4tim.nl/?p=4440Here I compare a 555 boost converter with a commercial one.http://www.pa4tim.nl/?p=4364And here a compare of the two opamp version you see everywhere and one I designed myselfThese all run 24V (or finally 27V because that was what I needed) but they do easy over 100V.The most important thing is the coil. It must be suited for the high frequency and it must be able to handle the peak current without saturating.Commercial ones for smps are rather foolproof, junkbox parts can be used but a L meter that measures on that frequency and a saturation tester comes in handy and saves a lot of time.

author: WarSim
author_rank: Frequent Contributor
timestamp: July 13, 2013, 12:45:43 am
content: I have always relied on by ability to recognize saturation problems. I had no idea they make saturation detectors for magnetics. I thought it was a tube world specialty.Which reliable manufacture makes lower cost but safe saturation detectors?Or a site on the most common testing methods to make one.

author: PA4TIM
author_rank: Super Contributor
timestamp: July 13, 2013, 05:45:31 am
content: AN-25 from Jim Williams off Linear Technology descibes a simple one. The side dos4ever too. I builded that last one but performance was not great, i later found Jims design and alterd mine with some of Jims ideas. That worked great.http://www.pa4tim.nl/?p=1859. Sorry this page is still in Dutch but there is a translate button in the menubar at the right.

author: sibushree
author_rank: Newbie
timestamp: July 13, 2013, 06:00:09 am
content: can anyone help me to design a dsp circuit for bandpass filter design using adspls reply me soon

author: WarSim
author_rank: Frequent Contributor
timestamp: July 13, 2013, 06:43:30 am
content: PA4TimFrom what I can see you skipped the reference coil and added a snubber to smooth out the reading.What I don't see is how is the output quantified?Is saturation calculated from the represented uncorrected current and duty on the scope?

author: PA4TIM
author_rank: Super Contributor
timestamp: July 13, 2013, 07:01:20 am
content: No, the reference coil is still there. The second schematic is just to show the snubber / "load" problem with the original is that all the energy had no where to go but back in the psu, so with a few Amp the powersupply did not like it.It uses a resistor to measure current differential with a scope. I forget the ratio, something like 100 mV/A, but I do not use that output anymore since I have a P6042 currentprobe.An improvement would be a adjustable oscillator but upto now it worked perfect as it is, even for inductors used at 200 kHz.You see the current go up while charging the coil, then when it starts to saturite you see a knee, and then in staturation the trace goes skyhigh. So you can see how much current it can handle. But it is very funny, inductors tell you when they get hurt, they start to scream when they go into saturation.