On a sunny day (Sat, 05 Nov 2011 16:34:45 -0700) it happened John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in <u4gbb7pfkoj039kml020vjr0lde1mrfosn@4ax.com>:>On Sat, 05 Nov 2011 20:46:28 GMT, Jan Panteltje ><pNaonStpealmtje@yahoo.com> wrote: > >>On a sunny day (Sat, 05 Nov 2011 10:11:37 -0700) it happened John Larkin >><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in >><18rab7t8aheb55q4s8m7b26nhmscdlk3bm@4ax.com>: >> >>>On Sat, 05 Nov 2011 10:59:48 -0500, Vladimir Vassilevsky >>><nospam@nowhere.com> wrote: >>> >>>> >>>> >>>>John Larkin wrote: >>>> >>>>>>Vladimir Vassilevsky wrote: >>>>>>>John Larkin wrote: >>>>>>> >>>>>>>>This >>>>>>>> >>>>>>>>http://www.panoramio.com/photo/61564837 >>>>>>>> >>>>>>>>might work for powering a thing I'm doing. >>>>>>>>Anybody got ideas for the base driver device? >>>> >>>>>>>You might want to check IR2085S >>>>> Actually, I ordered some IRS2153D's, a very simlar part. >>>> >>>>So, getting a self oscillating thing to work seems too complicated ? >>>>(http://www.abvolt.com/misc/self_osc.jpg) >>> >>>Actually, that does look complicated. >>> >>>> >>>>> A couple of bux of parts cost is not a big deal here. Getting it to >>>>> work the first time is. >>>> >>>>Use a PIC. >>> >>>Where would the PIC get its power from?! >>> >>>Just getting a square wave clock isn't hard. The power drivers are >>>what I'm playing with. I want a quiet, efficient, cheap, low-risk >>>5-watt dc/dc converter that uses stock parts, and I want it designed >>>and proven by, say, Monday afternoon. That's not unreasonable, is it? >>> >>>John >> >>I do not get it, you can use that same circuit you recommended and I used for the PMT HV supply. >>Just one transistor, 1 resistor, 1 transformer, 3 caps, and some diodes. >>I have used it in the past with the feedback in the base to power many things, >>for example my old EPROM programmer, from 5 V. > >I need nine separate power supplies, from a prime 24 volts that I have >to isolate. > >http://www.panoramio.com/photo/61715323Nice frame around it :-) Why not use different turns and diodes + cap for each voltage?>I just breadboarded the HV supply. I can pick off the 24 volts p-p >from the input half-bridge and run it through a cheap ISDN transformer >to get +110 VDC. Works like a charm, eliminates a boost converter I >was going to use. Those ISDN transformers are very cool. > >Dumping a full watt in the 2.5 linear regulator is sort of painful, >but it sure is cheap. > >A sinewave type converter would too inefficient for these sorts of >power levels. > >JohnI think this is not correct. In your sinewave oscillator the transistor actually works as a switch, it is only on for a very short period of time, sort of class C. I have used the sinewave circuit (with feedback in the base) to power relais in industrial applications were we needed isolation. The transistor stays cold, even under heavy load. What got warm was ceramic caps (for tuning), after replacing those with poly caps it all stayed cool. I suspect with your emittor feedback system it will work even better. Last week I replaced an other regulator with a LM2596-33. This whole thing runs of such an oscillator: http://panteltje.com/panteltje/pic/swr_pic/ Diagram, see top left: http://panteltje.com/panteltje/pic/swr_pic/swr_box_diagram.jpg
isolated DC/DC converter
Started by ●November 3, 2011
Reply by ●November 6, 20112011-11-06
Reply by ●November 6, 20112011-11-06
John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:>On Thu, 03 Nov 2011 11:51:16 -0500, legg <legg@nospam.magma.ca> wrote: > >>On Wed, 02 Nov 2011 23:45:15 -0700, miso <miso@sushi.com> wrote: >> >>>Given base charge storage, if the driver rise/fall time is fast, the >>>design could have shoot through. >> >>...and given magnetizing energy, emitters will be pulled above and >>below the rails. Shottkys can discourage this. The driver still may >>not be close enough to the rails to prevent base current and >>conduction in the switch, CE, to the opposite rails. >> >>Consider using a driver or controller intended for the function, with >>schottkys. >> >>RL > >I want to avoid custom magnetics, and I want it to be cheap, in caseThese guys put a nice transformer together for me rather quickly and for a reasonable price (competing with off-the-shelf transformers): http://www.custom-transformers.co.uk/ -- Failure does not prove something is impossible, failure simply indicates you are not using the right tools... nico@nctdevpuntnl (punt=.) --------------------------------------------------------------
Reply by ●November 6, 20112011-11-06
On Sat, 05 Nov 2011 10:59:48 -0500, Vladimir Vassilevsky <nospam@nowhere.com> wrote:> > >John Larkin wrote: > >>>Vladimir Vassilevsky wrote: >>>>John Larkin wrote: >>>> >>>>>This >>>>> >>>>>http://www.panoramio.com/photo/61564837 >>>>> >>>>>might work for powering a thing I'm doing. >>>>>Anybody got ideas for the base driver device? > >>>>You might want to check IR2085S >> Actually, I ordered some IRS2153D's, a very simlar part. > >So, getting a self oscillating thing to work seems too complicated ? >(http://www.abvolt.com/misc/self_osc.jpg) >No, it's the built-in simplicity that's hard to find, as an integrated feature. Most IC designers just don't get it. RL
Reply by ●November 6, 20112011-11-06
On Sat, 05 Nov 2011 09:40:53 -0700, John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:>On Sat, 05 Nov 2011 01:53:47 -0500, legg <legg@nospam.magma.ca> wrote: ><snip>>I did find a weird asymmetry that turned out to be a feature of LT >Spice. If you specify a pulse generator of > >Ton 5 us >Tr 1 us >Tf 1 us >Tper 10 us > >you get an asymmetric waveform. You need Ton of 4u to get symmetry. > > >John >It means a lot of decimal places, if you're trying to build a longer pattern within a set period, but I prefer this to some unknown homogenization going on, at the SW writer's half-baked whim. Realistic rise-times are best developed by identifiable elements in the simulation. I guess you're wondering, right about now, why there isn't an integrated, self-oscillating transformer driver in SO8 or even SOT23-5. Rail pins, output, timing and inhibit pins. No doubt there will be one, someday, but it will require 1-Wire serial programming and run on 2.65 - 3.6V supply rails. It'll only be available in 9-pin (3mm x 2mm) DFN. It will still require external schottkys, but this will not be discovered till 6 months after product release. RL
Reply by ●November 6, 20112011-11-06
On Sun, 06 Nov 2011 10:25:04 -0500, the renowned legg <legg@nospam.magma.ca> wrote:>On Sat, 05 Nov 2011 09:40:53 -0700, John Larkin ><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: > >>On Sat, 05 Nov 2011 01:53:47 -0500, legg <legg@nospam.magma.ca> wrote: >> ><snip> >>I did find a weird asymmetry that turned out to be a feature of LT >>Spice. If you specify a pulse generator of >> >>Ton 5 us >>Tr 1 us >>Tf 1 us >>Tper 10 us >> >>you get an asymmetric waveform. You need Ton of 4u to get symmetry. >> >> >>John >> > >It means a lot of decimal places, if you're trying to build a longer >pattern within a set period, but I prefer this to some unknown >homogenization going on, at the SW writer's half-baked whim. > >Realistic rise-times are best developed by identifiable elements in >the simulation. > >I guess you're wondering, right about now, why there isn't an >integrated, self-oscillating transformer driver in SO8 or even >SOT23-5. > >Rail pins, output, timing and inhibit pins.There are a few, but they're a bit oddball and expensive. MAX253 MAX845 MAX13256 This one is a bit more complex, but claims to be ultra-low noise: LT3439> >No doubt there will be one, someday, but it will require 1-Wire serial >programming and run on 2.65 - 3.6V supply rails. It'll only be >available in 9-pin (3mm x 2mm) DFN. It will still require external >schottkys, but this will not be discovered till 6 months after product >release. > >RLBest regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
Reply by ●November 6, 20112011-11-06
On Sun, 06 Nov 2011 10:25:04 -0500, legg <legg@nospam.magma.ca> wrote:>On Sat, 05 Nov 2011 09:40:53 -0700, John Larkin ><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: > >>On Sat, 05 Nov 2011 01:53:47 -0500, legg <legg@nospam.magma.ca> wrote: >> ><snip> >>I did find a weird asymmetry that turned out to be a feature of LT >>Spice. If you specify a pulse generator of >> >>Ton 5 us >>Tr 1 us >>Tf 1 us >>Tper 10 us >> >>you get an asymmetric waveform. You need Ton of 4u to get symmetry. >> >> >>John >> > >It means a lot of decimal places, if you're trying to build a longer >pattern within a set period, but I prefer this to some unknown >homogenization going on, at the SW writer's half-baked whim. > >Realistic rise-times are best developed by identifiable elements in >the simulation. > >I guess you're wondering, right about now, why there isn't an >integrated, self-oscillating transformer driver in SO8 or even >SOT23-5. > >Rail pins, output, timing and inhibit pins. > >No doubt there will be one, someday, but it will require 1-Wire serial >programming and run on 2.65 - 3.6V supply rails. It'll only be >available in 9-pin (3mm x 2mm) DFN. It will still require external >schottkys, but this will not be discovered till 6 months after product >release. > >RLI've used UCC3808 in a similar project, SO8, but it's a dual square wave gate driver, so it needs a center-tapped transformer, namely custom magnetics. John
Reply by ●November 6, 20112011-11-06
On Sun, 06 Nov 2011 09:45:41 -0500, legg <legg@nospam.magma.ca> wrote:>On Sat, 05 Nov 2011 10:59:48 -0500, Vladimir Vassilevsky ><nospam@nowhere.com> wrote: > >> >> >>John Larkin wrote: >> >>>>Vladimir Vassilevsky wrote: >>>>>John Larkin wrote: >>>>> >>>>>>This >>>>>> >>>>>>http://www.panoramio.com/photo/61564837 >>>>>> >>>>>>might work for powering a thing I'm doing. >>>>>>Anybody got ideas for the base driver device? >> >>>>>You might want to check IR2085S >>> Actually, I ordered some IRS2153D's, a very simlar part. >> >>So, getting a self oscillating thing to work seems too complicated ? >>(http://www.abvolt.com/misc/self_osc.jpg) >> > >No, it's the built-in simplicity that's hard to find, as an integrated >feature. > >Most IC designers just don't get it. > >RL"Most" IC Designers are laughing up their sleeve ;-) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
Reply by ●November 6, 20112011-11-06
On Sun, 06 Nov 2011 07:10:49 GMT, Mike <spam@me.not> wrote:>John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: > >> That might cause more problems than it cures. I am resigned (sigh) to >> having a noisy power supply, and doing PCB tricks to keep it from >> getting into the front-end amps and the 250 MHz ADC. >> >> John > >What kind of PCB tricks will keep fast edges out of wideband amps and a >250MHZ ADC? > >MikeKeep the switcher far from the ADC stuff; avoid circulating currents poked into the ground plane, by slitting the plane if necessary; add ferrite bead+capacitor lowpass filters to the supplies of the sensitive stuff. Keep the analog stuff very tight. And slow down those fast edges with gate resistors. Compounding the difficulty, there's the thermal design, getting rid of all that heat from the linear regulators. Less noise, more heat. Should be an interesting PCB layout. John
Reply by ●November 6, 20112011-11-06
On Sun, 06 Nov 2011 11:12:07 GMT, Jan Panteltje <pNaonStpealmtje@yahoo.com> wrote:>On a sunny day (Sat, 05 Nov 2011 16:34:45 -0700) it happened John Larkin ><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in ><u4gbb7pfkoj039kml020vjr0lde1mrfosn@4ax.com>: > >>On Sat, 05 Nov 2011 20:46:28 GMT, Jan Panteltje >><pNaonStpealmtje@yahoo.com> wrote: >> >>>On a sunny day (Sat, 05 Nov 2011 10:11:37 -0700) it happened John Larkin >>><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in >>><18rab7t8aheb55q4s8m7b26nhmscdlk3bm@4ax.com>: >>> >>>>On Sat, 05 Nov 2011 10:59:48 -0500, Vladimir Vassilevsky >>>><nospam@nowhere.com> wrote: >>>> >>>>> >>>>> >>>>>John Larkin wrote: >>>>> >>>>>>>Vladimir Vassilevsky wrote: >>>>>>>>John Larkin wrote: >>>>>>>> >>>>>>>>>This >>>>>>>>> >>>>>>>>>http://www.panoramio.com/photo/61564837 >>>>>>>>> >>>>>>>>>might work for powering a thing I'm doing. >>>>>>>>>Anybody got ideas for the base driver device? >>>>> >>>>>>>>You might want to check IR2085S >>>>>> Actually, I ordered some IRS2153D's, a very simlar part. >>>>> >>>>>So, getting a self oscillating thing to work seems too complicated ? >>>>>(http://www.abvolt.com/misc/self_osc.jpg) >>>> >>>>Actually, that does look complicated. >>>> >>>>> >>>>>> A couple of bux of parts cost is not a big deal here. Getting it to >>>>>> work the first time is. >>>>> >>>>>Use a PIC. >>>> >>>>Where would the PIC get its power from?! >>>> >>>>Just getting a square wave clock isn't hard. The power drivers are >>>>what I'm playing with. I want a quiet, efficient, cheap, low-risk >>>>5-watt dc/dc converter that uses stock parts, and I want it designed >>>>and proven by, say, Monday afternoon. That's not unreasonable, is it? >>>> >>>>John >>> >>>I do not get it, you can use that same circuit you recommended and I used for the PMT HV supply. >>>Just one transistor, 1 resistor, 1 transformer, 3 caps, and some diodes. >>>I have used it in the past with the feedback in the base to power many things, >>>for example my old EPROM programmer, from 5 V. >> >>I need nine separate power supplies, from a prime 24 volts that I have >>to isolate. >> >>http://www.panoramio.com/photo/61715323 > >Nice frame around it :-) >Why not use different turns and diodes + cap for each voltage?I'm trying to use standard magnetics. Two Coiltronics DRQ127's for the +-10, one Talema ISDN transformer for the 100 volts. Custom magnetics is a pain to develop and tends to be expensive in modest volumes. Or maybe an ISDN for the negative supplies. I'll have to try that.> > >>I just breadboarded the HV supply. I can pick off the 24 volts p-p >>from the input half-bridge and run it through a cheap ISDN transformer >>to get +110 VDC. Works like a charm, eliminates a boost converter I >>was going to use. Those ISDN transformers are very cool. >> >>Dumping a full watt in the 2.5 linear regulator is sort of painful, >>but it sure is cheap. >> >>A sinewave type converter would too inefficient for these sorts of >>power levels. >> >>John > >I think this is not correct. >In your sinewave oscillator the transistor actually works as a switch, >it is only on for a very short period of time, sort of class C. >I have used the sinewave circuit (with feedback in the base) >to power relais in industrial applications were we needed isolation. >The transistor stays cold, even under heavy load. >What got warm was ceramic caps (for tuning), >after replacing those with poly caps it all stayed cool. >I suspect with your emittor feedback system it will work even better. >Last week I replaced an other regulator with a LM2596-33. > >This whole thing runs of such an oscillator: > http://panteltje.com/panteltje/pic/swr_pic/ >Diagram, see top left: > http://panteltje.com/panteltje/pic/swr_pic/swr_box_diagram.jpgOK, but a class-C resonant converter has to circulate a lot of energy in the L-C tank, high currents into custom magnetics. Sloshing all that energy around doesn't seem, to me, to have any real advantage. I do recall some of the Tek 7000-series scopes having a single-transistor class C resonant main power supply, off the rectified AC line. We should establish a PayPal fund to buy you some nice gridded vellum and an electric pencil sharpener. John
Reply by ●November 6, 20112011-11-06
On Sun, 06 Nov 2011 09:45:41 -0500, legg <legg@nospam.magma.ca> wrote:>On Sat, 05 Nov 2011 10:59:48 -0500, Vladimir Vassilevsky ><nospam@nowhere.com> wrote: > >> >> >>John Larkin wrote: >> >>>>Vladimir Vassilevsky wrote: >>>>>John Larkin wrote: >>>>> >>>>>>This >>>>>> >>>>>>http://www.panoramio.com/photo/61564837 >>>>>> >>>>>>might work for powering a thing I'm doing. >>>>>>Anybody got ideas for the base driver device? >> >>>>>You might want to check IR2085S >>> Actually, I ordered some IRS2153D's, a very simlar part. >> >>So, getting a self oscillating thing to work seems too complicated ? >>(http://www.abvolt.com/misc/self_osc.jpg) >> > >No, it's the built-in simplicity that's hard to find, as an integrated >feature. > >Most IC designers just don't get it. > >RLWhen transistors are free, people tend to use lots of them. John
