krw@att.bizzzzzzzzzzzz wrote:> On Sat, 05 Nov 2011 10:36:42 -0700, John Larkin > <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: > >> On Sat, 05 Nov 2011 12:15:02 -0400, Spehro Pefhany >> <speffSNIP@interlogDOTyou.knowwhat> wrote: >> >>> On Sat, 05 Nov 2011 10:59:48 -0500, the renowned 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) >>>> >>>>> A couple of bux of parts cost is not a big deal here. Getting it to >>>>> work the first time is. >>>> Use a PIC. >>> It should be pretty easy to throw some randomness into the frequency >>> with a PIC for a spread-spectrum converter. >>> >>> >>> Best regards, >>> Spehro Pefhany >> I did a box that used a bunch of the LTM8023 bricks. I built a >> TinyLogic schmitt oscillator and used the triangle to FM all the >> switchers a little. It spread the switcher noise spectrum beautifully. > > What exactly did you do? Dither the voltage? > > If you were using a bunch, wouldn't multi-phase synchronous operation be > better? >The trick is to inject a slightly varying small current into the pin the timing capacitor hangs off of. This dithers the frequency a bit. -- Regards, Joerg http://www.analogconsultants.com/
isolated DC/DC converter
Started by ●November 3, 2011
Reply by ●November 5, 20112011-11-05
Reply by ●November 5, 20112011-11-05
On Sat, 05 Nov 2011 17:01:23 -0500, "krw@att.bizzzzzzzzzzzz" <krw@att.bizzzzzzzzzzzz> wrote:>On Sat, 05 Nov 2011 10:36:42 -0700, John Larkin ><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: > >>On Sat, 05 Nov 2011 12:15:02 -0400, Spehro Pefhany >><speffSNIP@interlogDOTyou.knowwhat> wrote: >> >>>On Sat, 05 Nov 2011 10:59:48 -0500, the renowned 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) >>>> >>>>> A couple of bux of parts cost is not a big deal here. Getting it to >>>>> work the first time is. >>>> >>>>Use a PIC. >>> >>>It should be pretty easy to throw some randomness into the frequency >>>with a PIC for a spread-spectrum converter. >>> >>> >>>Best regards, >>>Spehro Pefhany >> >>I did a box that used a bunch of the LTM8023 bricks. I built a >>TinyLogic schmitt oscillator and used the triangle to FM all the >>switchers a little. It spread the switcher noise spectrum beautifully. > >What exactly did you do? Dither the voltage?Just squirt a little triangle current into the Vadj pin. That dithers the duty cycle. How much it wobbles the output voltage depends on the triangle frequency and the output filter caps. http://www.panoramio.com/photo/61713825 http://www.panoramio.com/photo/61713828 http://www.panoramio.com/photo/61713822 This much FM wobbled the DC output about a millivolt p-p.> >If you were using a bunch, wouldn't multi-phase synchronous operation be >better? >This was an FTMS spectroscopy app where any birdies in the FFT would be noticed. The dither sawtooth was around 4 KHz, below the range of interest of the physics. John
Reply by ●November 5, 20112011-11-05
On Sat, 05 Nov 2011 10:11:37 -0700, John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> 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) > >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?--- Maybe, maybe not. What are you willing to pay for a solution? -- JF
Reply by ●November 5, 20112011-11-05
On 11/2/2011 10:51 PM, John Larkin wrote:> This > > http://www.panoramio.com/photo/61564837 > > might work for powering a thing I'm doing. I can use a standard cheap > Coiltronix dual-coil inductor as the transformer. The complementary > emitter followers will have no shoot-through and can have controllably > slow switching edges, since they will just follow the base drive. > > Anybody got ideas for the base driver device? Ideally it would be > self-oscillating, set with some R-C; have a moderate slew rate; swing > to the rails. I'm thinking roughly 150 KHz maybe, a few watts output. > > Maybe an LM8261 opamp? I'd have to see if it winds up when it rails. > It might not. > > Some sort of fet gate driver would be OK, but few go to 24 volts. > > Something discrete maybe, like a 2N7002 to 24-, and maybe a > bootstrapped pullup? > > > JohnI have no suggestions for the driver, John, but I would suggest some resistance in series with the supply as the cap will need to charge to half the supply voltage and the core may saturate in the process. Just a precaution, and it may not be necessary. Looks good to me. John S
Reply by ●November 5, 20112011-11-05
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 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
Reply by ●November 5, 20112011-11-05
On Sat, 05 Nov 2011 18:21:29 -0500, John Fields <jfields@austininstruments.com> wrote:>On Sat, 05 Nov 2011 10:11:37 -0700, John Larkin ><jjlarkin@highNOTlandTHIStechnologyPART.com> 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) >> >>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? > >--- >Maybe, maybe not. > >What are you willing to pay for a solution?Heck, the most fun thing I do at work is design circuits. I'm happy to pay people to hack VHDL or write test code, but not to design my circuits! John
Reply by ●November 5, 20112011-11-05
John Larkin wrote:> 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 > > 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. >No smoothing inductors at the rectifiers? The current peaks when the caps get replenished "whambam style" are often not too friendly towards analog stuff in the neighborhood. Like a Harley at night :-) -- Regards, Joerg http://www.analogconsultants.com/
Reply by ●November 5, 20112011-11-05
On Sat, 05 Nov 2011 17:13:43 -0700, Joerg <invalid@invalid.invalid> wrote:>John Larkin wrote: >> 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 >> >> 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. >> > >No smoothing inductors at the rectifiers? The current peaks when the >caps get replenished "whambam style" are often not too friendly towards >analog stuff in the neighborhood. Like a Harley at night :-)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
Reply by ●November 6, 20112011-11-06
On Sat, 05 Nov 2011 16:01:56 -0700, John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:>On Sat, 05 Nov 2011 17:01:23 -0500, "krw@att.bizzzzzzzzzzzz" ><krw@att.bizzzzzzzzzzzz> wrote: > >>On Sat, 05 Nov 2011 10:36:42 -0700, John Larkin >><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: >> >>>On Sat, 05 Nov 2011 12:15:02 -0400, Spehro Pefhany >>><speffSNIP@interlogDOTyou.knowwhat> wrote: >>> >>>>On Sat, 05 Nov 2011 10:59:48 -0500, the renowned 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) >>>>> >>>>>> A couple of bux of parts cost is not a big deal here. Getting it to >>>>>> work the first time is. >>>>> >>>>>Use a PIC. >>>> >>>>It should be pretty easy to throw some randomness into the frequency >>>>with a PIC for a spread-spectrum converter. >>>> >>>> >>>>Best regards, >>>>Spehro Pefhany >>> >>>I did a box that used a bunch of the LTM8023 bricks. I built a >>>TinyLogic schmitt oscillator and used the triangle to FM all the >>>switchers a little. It spread the switcher noise spectrum beautifully. >> >>What exactly did you do? Dither the voltage? > > >Just squirt a little triangle current into the Vadj pin. That dithers >the duty cycle. How much it wobbles the output voltage depends on the >triangle frequency and the output filter caps.That's what I suspected, but doesn't that also dither the output voltage?> >http://www.panoramio.com/photo/61713825 > >http://www.panoramio.com/photo/61713828Impressive.>http://www.panoramio.com/photo/61713822 > >This much FM wobbled the DC output about a millivolt p-p.I would have thought it would take significantly more to change the edges significantly. Neat.> >>If you were using a bunch, wouldn't multi-phase synchronous operation be >>better? >> > >This was an FTMS spectroscopy app where any birdies in the FFT would >be noticed. The dither sawtooth was around 4 KHz, below the range of >interest of the physics.Yes, interesting.
Reply by ●November 6, 20112011-11-06
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. > > JohnWhat kind of PCB tricks will keep fast edges out of wideband amps and a 250MHZ ADC? Mike
