Anyone familiar with a high voltage charge pump designed as a step down power supply? The voltage is between 175 & 200. Numerous high voltage versions exist using inductors, (Onsemi has one that is "self supplied" which is attractive) but not a one that works with just a capacitor. Are there any out there I've missed? Hul
high voltage charge pump
Started by ●December 30, 2019
Reply by ●December 30, 20192019-12-30
Hul Tytus wrote...> > Anyone familiar with a high voltage charge pump designed as a > step down power supply? The voltage is between 175 & 200. Numerous > high voltage versions exist using inductors, (Onsemi has one that > is "self supplied" which is attractive) but not a one that works > with just a capacitor. Are there any out there I've missed?Capacitor step-up supplies are called Cockcroft-Walton generators and a similar form are Marx generators. An inverse version of the circuit can do step-down. We encountered a fellow, Steve Cerwin, who promoted that form. Crazy, we thought, but went ahead anyway, and wrote it up for the AoE x-Chapters, section 9x.15.5, page 439. Capacitors are charged in series, but discharged in parallel. We show a circuit that does 120 Vac to 24 Vdc, using six capacitors, and 14 diodes, awk! The output current is stepped up, of course. But, just because you can do it, that doesn't mean you should. -- Thanks, - Win
Reply by ●December 30, 20192019-12-30
AFAIR the step down cap supplies is not that bad 7 stages or more sounds like a nightmare, but since individual voltage is low, the process can be low voltage and thus cheap That said, I am yet to see one that can compete with inductor step down Cheers Klaus
Reply by ●December 30, 20192019-12-30
Win - In this case, the existing power supply is between 175 & 200 volts. The needed supply is 12 volts. Similar to a nonisolated dc supply from a 115 volt ac line I suspect there is such a device on the market, but proper search terms are required. Hul Winfield Hill <winfieldhill@yahoo.com> wrote:> Hul Tytus wrote... > > > > Anyone familiar with a high voltage charge pump designed as a > > step down power supply? The voltage is between 175 & 200. Numerous > > high voltage versions exist using inductors, (Onsemi has one that > > is "self supplied" which is attractive) but not a one that works > > with just a capacitor. Are there any out there I've missed?> Capacitor step-up supplies are called Cockcroft-Walton generators > and a similar form are Marx generators. An inverse version of the > circuit can do step-down. We encountered a fellow, Steve Cerwin, > who promoted that form. Crazy, we thought, but went ahead anyway, > and wrote it up for the AoE x-Chapters, section 9x.15.5, page 439. > Capacitors are charged in series, but discharged in parallel. We > show a circuit that does 120 Vac to 24 Vdc, using six capacitors, > and 14 diodes, awk! The output current is stepped up, of course. > But, just because you can do it, that doesn't mean you should. >> -- > Thanks, > - Win
Reply by ●December 30, 20192019-12-30
You're going the wrong way, Klaus. Take a look at the message to win. Hul Klaus Kragelund <klauskvik@hotmail.com> wrote:> AFAIR the step down cap supplies is not that bad> 7 stages or more sounds like a nightmare, but since individual voltage is low, the process can be low voltage and thus cheap> That said, I am yet to see one that can compete with inductor step down> Cheers> Klaus
Reply by ●December 30, 20192019-12-30
Hul Tytus wrote...> > Win - In this case, the existing power supply is between > 175 & 200 volts. The needed supply is 12 volts. Similar > to a nonisolated dc supply from a 115 volt ac line. > I suspect there is such a device on the market, but proper > search terms are required.Of course there is, but it'll most likely be transformer based (an inductor will have too poor a duty cycle). No capacitive circuits, such as I mentioned will be found. (There is low-power AC-to-DC, using a single cap, which we cover in some detail, but that's another story). What you're forgetting is that most AC offline to low-V DC converters start with a bridge rectifier.** In the case of 120Vac, they're internally working from about 170Vdc on their bulk capacitor. Many work up to 230Vac, which more than covers your range. They convert down to all types of DC voltages. But they're happy with DC as an input. So you simply hook up your DC source to one of these "AC supplies", and hey, Bob's your uncle. ** Inspect to be sure there's a input bridge rectifier -- Thanks, - Win
Reply by ●December 30, 20192019-12-30
On Monday, December 30, 2019 at 12:59:03 PM UTC-8, Hul Tytus wrote:> Win - In this case, the existing power supply is between 175 & 200 volts. The needed > supply is 12 volts. Similar to a nonisolated dc supply from a 115 volt ac line > I suspect there is such a device on the market, but proper search terms are > required. >> > > ...but not a one that works > > > with just a capacitor.The level-shifting required to make switches for the whole voltage range is one problem, and the high inrush currents when capacitors are connected (like, only limited by the switch resistance) is another. Microscopic switches can get hot FAST. Inductance solves the inrush problem, but once you go with power inductors, the capacitors aren't required.
Reply by ●December 30, 20192019-12-30
On Monday, 30 December 2019 20:59:03 UTC, Hul Tytus wrote:> Win - In this case, the existing power supply is between 175 & 200 volts. The needed > supply is 12 volts. Similar to a nonisolated dc supply from a 115 volt ac line > I suspect there is such a device on the market, but proper search terms are > required. > > HulI'm imagining a wooden drum with brass shim contacts, a bank of paper caps and a small motor. Probably feeding a CLC filter, and thence to a post-WW1 radio. NT
Reply by ●December 31, 20192019-12-31
On Monday, December 30, 2019 at 10:00:46 PM UTC+1, Hul Tytus wrote:> You're going the wrong way, Klaus. Take a look at the message to win. >I don't think so See example: https://www.analog.com/media/en/technical-documentation/data-sheets/7820fc.pdf Page 25, 48V to 12V switched capacitor high efficiency solution. A 200V DC type might exist
Reply by ●December 31, 20192019-12-31
On Tuesday, December 31, 2019 at 11:06:06 AM UTC+1, Klaus Kragelund wrote:> On Monday, December 30, 2019 at 10:00:46 PM UTC+1, Hul Tytus wrote: > > You're going the wrong way, Klaus. Take a look at the message to win. > > > > I don't think so > > See example: > > https://www.analog.com/media/en/technical-documentation/data-sheets/7820fc.pdf > > Page 25, 48V to 12V switched capacitor high efficiency solution. > > A 200V DC type might existPage 89 of this excellent danish thesis :-) https://backend.orbit.dtu.dk/ws/portalfiles/portal/146710275/PhD_thesis_Lin_Fan_20180422_Orbit.pdf 380V to 95V (4:1). Add a couple of more stages, and your ratio is solved. This is not easy stuff though, plenty of easy solutions are available. Pick any: https://www.digikey.com/products/en/integrated-circuits-ics/pmic-ac-dc-converters-offline-switchers/748?k=&pkeyword=&sv=0&pv939=380376&sf=0&FV=-8%7C748%2C740%7C193216%2C740%7C213650%2C740%7C221502%2C740%7C237347%2C740%7C241322%2C740%7C256165%2C740%7C258857%2C740%7C262530%2C740%7C264229%2C740%7C273330&quantity=&ColumnSort=0&page=1&pageSize=25
