Hi I am working on a small 100mW forward converter and I need a very low power PWM control. So the 555 comes up, along with some ultra low power opamps. But, isn't there a PWM chips out there with low operating current. Sofar I found the TPS5110 with sub mA current consumption: http://www.ti.com/lit/ds/symlink/tps5110.pdf Anyone used one with lower current? Thanks Klaus
Low power PWM controller, possibly the 555 (flame war coming)
Started by ●August 30, 2012
Reply by ●August 30, 20122012-08-30
On a sunny day (Thu, 30 Aug 2012 04:05:39 -0700 (PDT)) it happened Klaus Kragelund <klauskvik@hotmail.com> wrote in <b82a88e9-a2b7-4bc4-ae9a-bb845ab075e5@googlegroups.com>:>Hi > >I am working on a small 100mW forward converter and I need a very low power PWM control. > >So the 555 comes up, along with some ultra low power opamps. But, isn't there a PWM chips out there with low operating current. >Sofar I found the TPS5110 with sub mA current consumption: > >http://www.ti.com/lit/ds/symlink/tps5110.pdf > >Anyone used one with lower current? > >Thanks > >KlausI know it is an old song, but I am using PICs (PWM output, build in 2 comparators, calibration in EEPOM) for all that. Why go looking for chips when I have one in the box that can do almost anything, given some software capabilities.
Reply by ●August 30, 20122012-08-30
On Aug 30, 1:33=A0pm, Jan Panteltje <pNaonStpealm...@yahoo.com> wrote:> On a sunny day (Thu, 30 Aug 2012 04:05:39 -0700 (PDT)) it happened Klaus > Kragelund <klausk...@hotmail.com> wrote in > <b82a88e9-a2b7-4bc4-ae9a-bb845ab075e5@googlegroups.com>: > > >Hi > > >I am working on a small 100mW forward converter and I need a very low po=wer PWM control.> > >So the 555 comes up, along with some ultra low power opamps. But, isn't =there a PWM chips out there with low operating current.> >Sofar I found the TPS5110 with sub mA current consumption: > > >http://www.ti.com/lit/ds/symlink/tps5110.pdf > > >Anyone used one with lower current? > > >Thanks > > >Klaus > > I know it is an old song, but I am using PICs (PWM output, build in 2 com=parators,> calibration in EEPOM) for all that. > Why go looking for chips when I have one in the box that can do almost an=ything, given some software capabilities. Well, I have a Cortex M3 running at 4MHz, but the sw guys don't like me using that in a SW loop. I could generate a PWM to set the frequency, add F/F to set the output, and a comparator to reset the output (current mode control). Then add an voltage error amp to control the peak current level. Going further, I could use the internal comparator for the reset of the PWM for peak current control without CPU resources used, but the comparator has 2-4us propagation delay, seriously lowering the sensible frequency the converter can run at. I guess the delay is just a level shift of the peak current level and that is regulated back by the error amp anyway, so maybe it could work. Would however have a minimum duty cycle of 20% (for 100kHz and 2us propagation delay) For that solution I need to add a circuit to monitor the current and reset the CPU if it hangs. That takes some more parts in the wrong direction. But, I would like to see if there is a PWM controller that has low enough current anyway. Regards Klaus
Reply by ●August 30, 20122012-08-30
On Thu, 30 Aug 2012 04:05:39 -0700 (PDT), Klaus Kragelund <klauskvik@hotmail.com> wrote:>Hi > >I am working on a small 100mW forward converter and I need a very low power PWM control. > >So the 555 comes up, along with some ultra low power opamps. But, isn't there a PWM chips out there with low operating current. Sofar I found the TPS5110 with sub mA current consumption: > >http://www.ti.com/lit/ds/symlink/tps5110.pdf > >Anyone used one with lower current? > >Thanks > >KlausThat's a buck controller, technically not what you'd use in a forward converter. Are you actually doing a non-isolated buck? What are your input and output voltages? -- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
Reply by ●August 30, 20122012-08-30
On Thursday, August 30, 2012 4:24:03 PM UTC+2, John Larkin wrote:> On Thu, 30 Aug 2012 04:05:39 -0700 (PDT), Klaus Kragelund > > <klauskvik@hotmail.com> wrote: > > > > >Hi > > > > > >I am working on a small 100mW forward converter and I need a very low power PWM control. > > > > > >So the 555 comes up, along with some ultra low power opamps. But, isn't there a PWM chips out there with low operating current. Sofar I found the TPS5110 with sub mA current consumption: > > > > > >http://www.ti.com/lit/ds/symlink/tps5110.pdf > > > > > >Anyone used one with lower current? > > > > > >Thanks > > > > > >Klaus > > > > That's a buck controller, technically not what you'd use in a forward > > converter. Are you actually doing a non-isolated buck? > > > > What are your input and output voltages? > > >Yes, its a buck, and it has to large max duty cycle. Just an example of a low current PWM. My input voltage is from about 8V to 20V, output 3.3V. Transformer will probably be 1:1 so I can use off the shelf types approved for EN69650. Regards Klaus
Reply by ●August 30, 20122012-08-30
On Thu, 30 Aug 2012 13:35:13 -0700 (PDT), Klaus Kragelund <klauskvik@hotmail.com> wrote:>On Thursday, August 30, 2012 4:24:03 PM UTC+2, John Larkin wrote: >> On Thu, 30 Aug 2012 04:05:39 -0700 (PDT), Klaus Kragelund >> >> <klauskvik@hotmail.com> wrote: >> >> >> >> >Hi >> >> > >> >> >I am working on a small 100mW forward converter and I need a very low power PWM control. >> >> > >> >> >So the 555 comes up, along with some ultra low power opamps. But, isn't there a PWM chips out there with low operating current. Sofar I found the TPS5110 with sub mA current consumption: >> >> > >> >> >http://www.ti.com/lit/ds/symlink/tps5110.pdf >> >> > >> >> >Anyone used one with lower current? >> >> > >> >> >Thanks >> >> > >> >> >Klaus >> >> >> >> That's a buck controller, technically not what you'd use in a forward >> >> converter. Are you actually doing a non-isolated buck? >> >> >> >> What are your input and output voltages? >> >> >> > >Yes, its a buck, and it has to large max duty cycle. Just an example of a low current PWM. > >My input voltage is from about 8V to 20V, output 3.3V. Transformer will probably be 1:1 so I can use off the shelf types approved for EN69650. > >Regards > >KlausTransformer? A buck uses an inductor! What is the topology? -- John Larkin Highland Technology, Inc jlarkin at highlandtechnology dot com http://www.highlandtechnology.com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser drivers and controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation
Reply by ●August 30, 20122012-08-30
Reply by ●August 30, 20122012-08-30
On Thu, 30 Aug 2012 04:51:28 -0700, Klaus Kragelund wrote:> On Aug 30, 1:33 pm, Jan Panteltje <pNaonStpealm...@yahoo.com> wrote: >> On a sunny day (Thu, 30 Aug 2012 04:05:39 -0700 (PDT)) it happened >> Klaus Kragelund <klausk...@hotmail.com> wrote in >> <b82a88e9-a2b7-4bc4-ae9a-bb845ab075e5@googlegroups.com>: >> >> >Hi >> >> >I am working on a small 100mW forward converter and I need a very low >> >power PWM control. >> >> >So the 555 comes up, along with some ultra low power opamps. But, >> >isn't there a PWM chips out there with low operating current. Sofar I >> >found the TPS5110 with sub mA current consumption: >> >> >http://www.ti.com/lit/ds/symlink/tps5110.pdf >> >> >Anyone used one with lower current? >> >> >Thanks >> >> >Klaus >> >> I know it is an old song, but I am using PICs (PWM output, build in 2 >> comparators, calibration in EEPOM) for all that. >> Why go looking for chips when I have one in the box that can do almost >> anything, given some software capabilities. > > Well, I have a Cortex M3 running at 4MHz, but the sw guys don't like me > using that in a SW loop. > > I could generate a PWM to set the frequency, add F/F to set the output, > and a comparator to reset the output (current mode control). Then add an > voltage error amp to control the peak current level. > > Going further, I could use the internal comparator for the reset of the > PWM for peak current control without CPU resources used, but the > comparator has 2-4us propagation delay, seriously lowering the sensible > frequency the converter can run at. I guess the delay is just a level > shift of the peak current level and that is regulated back by the error > amp anyway, so maybe it could work. Would however have a minimum duty > cycle of 20% (for 100kHz and 2us propagation delay) > > For that solution I need to add a circuit to monitor the current and > reset the CPU if it hangs. That takes some more parts in the wrong > direction. > > But, I would like to see if there is a PWM controller that has low > enough current anyway. > > Regards > > KlausUse a 6-pin PIC, program it yourself, and pass it off as an analog component. -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com
Reply by ●August 30, 20122012-08-30
Do something like this, but configured for forward operation instead: http://t3sl4.dnsdynamic.net/Images/Deadbug_Sch.png obviously, replace the amp-gobbling TL431 with something more frugal. You can save the bias current wasted in the switching transistor by using a positive feedback winding, making the circuit a basic blocking oscillator instead. Tim -- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms "Klaus Kragelund" <klauskvik@hotmail.com> wrote in message news:b82a88e9-a2b7-4bc4-ae9a-bb845ab075e5@googlegroups.com...> Hi > > I am working on a small 100mW forward converter and I need a very low > power PWM control. > > So the 555 comes up, along with some ultra low power opamps. But, isn't > there a PWM chips out there with low operating current. Sofar I found > the TPS5110 with sub mA current consumption: > > http://www.ti.com/lit/ds/symlink/tps5110.pdf > > Anyone used one with lower current? > > Thanks > > Klaus
Reply by ●September 3, 20122012-09-03
On Thu, 30 Aug 2012 13:58:31 -0700, John Larkin <jlarkin@highlandtechnology.com> wrote:>On Thu, 30 Aug 2012 13:35:13 -0700 (PDT), Klaus Kragelund ><klauskvik@hotmail.com> wrote: > >>On Thursday, August 30, 2012 4:24:03 PM UTC+2, John Larkin wrote: >>> On Thu, 30 Aug 2012 04:05:39 -0700 (PDT), Klaus Kragelund >>>=20 >>> <klauskvik@hotmail.com> wrote: >>>=20 >>>=20 >>>=20 >>> >Hi >>>=20 >>> > >>>=20 >>> >I am working on a small 100mW forward converter and I need a very =low power PWM control.>>>=20 >>> > >>>=20 >>> >So the 555 comes up, along with some ultra low power opamps. But, =isn't there a PWM chips out there with low operating current. Sofar I = found the TPS5110 with sub mA current consumption:>>>=20 >>> > >>>=20 >>> >http://www.ti.com/lit/ds/symlink/tps5110.pdf >>>=20 >>> > >>>=20 >>> >Anyone used one with lower current? >>>=20 >>> > >>>=20 >>> >Thanks >>>=20 >>> > >>>=20 >>> >Klaus=20 >>>=20 >>>=20 >>>=20 >>> That's a buck controller, technically not what you'd use in a forward >>>=20 >>> converter. Are you actually doing a non-isolated buck? >>>=20 >>>=20 >>>=20 >>> What are your input and output voltages? >>>=20 >>>=20 >>>=20 >> >>Yes, its a buck, and it has to large max duty cycle. Just an example of=a low current PWM.>> >>My input voltage is from about 8V to 20V, output 3.3V. Transformer will=probably be 1:1 so I can use off the shelf types approved for EN69650.>> >>Regards >> >>Klaus=20 > >Transformer? A buck uses an inductor! > >What is the topology?You clearly missed the isolation requirement implied by EN69650. ?-)
