On Wed, 9 Sep 2020 10:26:14 -0700 (PDT), Edward Lee <edward.ming.lee@gmail.com> wrote:>On Wednesday, September 9, 2020 at 10:14:34 AM UTC-7, John Larkin wrote: >> On Wed, 9 Sep 2020 08:42:20 -0700 (PDT), Edward Lee >> <edward....@gmail.com> wrote: >> >> >On Wednesday, September 9, 2020 at 7:28:15 AM UTC-7, John Larkin wrote: >> >> On Wed, 9 Sep 2020 05:21:42 -0700 (PDT), Edward Lee >> >> <edward....@gmail.com> wrote: >> >> >I can't figure out how to post new message with the new google group. A search of TL431 came up with this thread recently. So, i am high-jacking this for a quick question: >> >> > >> >> >> For isolated application, the feedback divider has to be secondary side only >> >> >> and a TL431 used for error amp, into an opto, in the usual way. >> >> > >> >> >I need a 12V 5A High Current Shunt Regulator, using fig. 19 of page 7 >> >> > >> >> >https://www.onsemi.com/pub/Collateral/TL431-D.PDF >> >> > >> >> >I am using 10K for R1, 1.1K for R2. What should i use for Rbe of the pass transistor (TO-220 PNP)? >> >> You could fry the TL431 at 5 amps out, from too much PNP base current. >> > >> >5A max for the AWG22 wires. Actual current may be couple of As for an instant. >> > >> >> A p-channel mosfet would help there, instead of the PNP. >> > >> >OK. >> > >> >> But the answer could be 5K either way. >> > >> >OK, thanks. >> Actually, with the PNP, it doesn't need a b-e resistor. Once, about 60 >> years ago, people used leaky germanium transistors, so using b-e >> resistors became folklore. > >OK, i'll try a 5 ohm emitter resistor to limit the current. Once triggered, it will probably start to discharge into other cells, but that's fine.Or consider a collector resistor. That's easier to think about. -- John Larkin Highland Technology, Inc trk The cork popped merrily, and Lord Peter rose to his feet. "Bunter", he said, "I give you a toast. The triumph of Instinct over Reason"
24V to 500-1000V, 20W floating DC-DC converter
Started by ●July 21, 2020
Reply by ●September 9, 20202020-09-09
Reply by ●September 9, 20202020-09-09
On Wed, 09 Sep 2020 14:09:45 -0400, legg <legg@nospam.magma.ca> wrote:>On Wed, 09 Sep 2020 10:14:16 -0700, John Larkin ><jjlarkin@highlandtechnology.com> wrote: > >>On Wed, 9 Sep 2020 08:42:20 -0700 (PDT), Edward Lee >><edward.ming.lee@gmail.com> wrote: >> >>>On Wednesday, September 9, 2020 at 7:28:15 AM UTC-7, John Larkin wrote: >>>> On Wed, 9 Sep 2020 05:21:42 -0700 (PDT), Edward Lee >>>> <edward....@gmail.com> wrote: >>>> >I can't figure out how to post new message with the new google group. A search of TL431 came up with this thread recently. So, i am high-jacking this for a quick question: >>>> > >>>> >> For isolated application, the feedback divider has to be secondary side only >>>> >> and a TL431 used for error amp, into an opto, in the usual way. >>>> > >>>> >I need a 12V 5A High Current Shunt Regulator, using fig. 19 of page 7 >>>> > >>>> >https://www.onsemi.com/pub/Collateral/TL431-D.PDF >>>> > >>>> >I am using 10K for R1, 1.1K for R2. What should i use for Rbe of the pass transistor (TO-220 PNP)? >>>> You could fry the TL431 at 5 amps out, from too much PNP base current. >>> >>>5A max for the AWG22 wires. Actual current may be couple of As for an instant. >>> >>>> A p-channel mosfet would help there, instead of the PNP. >>> >>>OK. >>> >>>> But the answer could be 5K either way. >>> >>>OK, thanks. >> >>Actually, with the PNP, it doesn't need a b-e resistor. Once, about 60 >>years ago, people used leaky germanium transistors, so using b-e >>resistors became folklore. > >It's still advisable for any npn running over it's Vce >range at the temperature limit.Why? -- John Larkin Highland Technology, Inc trk The cork popped merrily, and Lord Peter rose to his feet. "Bunter", he said, "I give you a toast. The triumph of Instinct over Reason"
Reply by ●September 9, 20202020-09-09
On Wed, 09 Sep 2020 10:14:16 -0700, John Larkin <jjlarkin@highlandtechnology.com> wrote:>On Wed, 9 Sep 2020 08:42:20 -0700 (PDT), Edward Lee ><edward.ming.lee@gmail.com> wrote: > >>On Wednesday, September 9, 2020 at 7:28:15 AM UTC-7, John Larkin wrote: >>> On Wed, 9 Sep 2020 05:21:42 -0700 (PDT), Edward Lee >>> <edward....@gmail.com> wrote: >>> >I can't figure out how to post new message with the new google group. A search of TL431 came up with this thread recently. So, i am high-jacking this for a quick question: >>> > >>> >> For isolated application, the feedback divider has to be secondary side only >>> >> and a TL431 used for error amp, into an opto, in the usual way. >>> > >>> >I need a 12V 5A High Current Shunt Regulator, using fig. 19 of page 7 >>> > >>> >https://www.onsemi.com/pub/Collateral/TL431-D.PDF >>> > >>> >I am using 10K for R1, 1.1K for R2. What should i use for Rbe of the pass transistor (TO-220 PNP)? >>> You could fry the TL431 at 5 amps out, from too much PNP base current. >> >>5A max for the AWG22 wires. Actual current may be couple of As for an instant. >> >>> A p-channel mosfet would help there, instead of the PNP. >> >>OK. >> >>> But the answer could be 5K either way. >> >>OK, thanks. > >Actually, with the PNP, it doesn't need a b-e resistor. Once, about 60 >years ago, people used leaky germanium transistors, so using b-e >resistors became folklore.It's still advisable for any npn running over it's Vce range at the temperature limit. Germaniums were both leaky and more temperature-sensitive - typical BE resistor <200R. You'd normally want to keep the TL431 in linear operation. Minimum spec is Ik >= 1mA for bog standard TL431. There's no spec for Ik, out of regulation. Maximum Ik at 11V is about 30mA, before you'd get overheating. RL
Reply by ●September 9, 20202020-09-09
On Wednesday, September 9, 2020 at 11:04:00 AM UTC-7, legg wrote:> On Wed, 09 Sep 2020 10:14:16 -0700, John Larkin > <jjla...@highlandtechnology.com> wrote: > > >On Wed, 9 Sep 2020 08:42:20 -0700 (PDT), Edward Lee > ><edward....@gmail.com> wrote: > > > >>On Wednesday, September 9, 2020 at 7:28:15 AM UTC-7, John Larkin wrote: > >>> On Wed, 9 Sep 2020 05:21:42 -0700 (PDT), Edward Lee > >>> <edward....@gmail.com> wrote: > >>> >I can't figure out how to post new message with the new google group. A search of TL431 came up with this thread recently. So, i am high-jacking this for a quick question: > >>> > > >>> >> For isolated application, the feedback divider has to be secondary side only > >>> >> and a TL431 used for error amp, into an opto, in the usual way. > >>> > > >>> >I need a 12V 5A High Current Shunt Regulator, using fig. 19 of page 7 > >>> > > >>> >https://www.onsemi.com/pub/Collateral/TL431-D.PDF > >>> > > >>> >I am using 10K for R1, 1.1K for R2. What should i use for Rbe of the pass transistor (TO-220 PNP)? > >>> You could fry the TL431 at 5 amps out, from too much PNP base current. > >> > >>5A max for the AWG22 wires. Actual current may be couple of As for an instant. > >> > >>> A p-channel mosfet would help there, instead of the PNP. > >> > >>OK. > >> > >>> But the answer could be 5K either way. > >> > >>OK, thanks. > > > >Actually, with the PNP, it doesn't need a b-e resistor. Once, about 60 > >years ago, people used leaky germanium transistors, so using b-e > >resistors became folklore. > It's still advisable for any npn running over it's Vce > range at the temperature limit.Yes, i will use a 5 ohm emitter resistor to limit both base and collector current.> Germaniums were both leaky and more temperature-sensitive - > typical BE resistor <200R. > > You'd normally want to keep the TL431 in linear operation. > Minimum spec is Ik >= 1mA for bog standard TL431. There's > no spec for Ik, out of regulation. > > Maximum Ik at 11V is about 30mA, before you'd get overheating.It will be much less than 11V for the TL431. I think it can handle 100mA.
Reply by ●September 9, 20202020-09-09
On Wed, 9 Sep 2020 10:26:14 -0700 (PDT), Edward Lee <edward.ming.lee@gmail.com> wrote:>On Wednesday, September 9, 2020 at 10:14:34 AM UTC-7, John Larkin wrote: >> On Wed, 9 Sep 2020 08:42:20 -0700 (PDT), Edward Lee >> <edward....@gmail.com> wrote: >> >> >On Wednesday, September 9, 2020 at 7:28:15 AM UTC-7, John Larkin wrote: >> >> On Wed, 9 Sep 2020 05:21:42 -0700 (PDT), Edward Lee >> >> <edward....@gmail.com> wrote: >> >> >I can't figure out how to post new message with the new google group. A search of TL431 came up with this thread recently. So, i am high-jacking this for a quick question: >> >> > >> >> >> For isolated application, the feedback divider has to be secondary side only >> >> >> and a TL431 used for error amp, into an opto, in the usual way. >> >> > >> >> >I need a 12V 5A High Current Shunt Regulator, using fig. 19 of page 7 >> >> > >> >> >https://www.onsemi.com/pub/Collateral/TL431-D.PDF >> >> > >> >> >I am using 10K for R1, 1.1K for R2. What should i use for Rbe of the pass transistor (TO-220 PNP)? >> >> You could fry the TL431 at 5 amps out, from too much PNP base current. >> > >> >5A max for the AWG22 wires. Actual current may be couple of As for an instant. >> > >> >> A p-channel mosfet would help there, instead of the PNP. >> > >> >OK. >> > >> >> But the answer could be 5K either way. >> > >> >OK, thanks. >> Actually, with the PNP, it doesn't need a b-e resistor. Once, about 60 >> years ago, people used leaky germanium transistors, so using b-e >> resistors became folklore. > >OK, i'll try a 5 ohm emitter resistor to limit the current. Once triggered, it will probably start to discharge into other cells, but that's fine.Check your battery spec. A float voltage will seldom be 12V. You're looking for a series cell ballancing circuit . . ? RL
Reply by ●September 9, 20202020-09-09
On Wednesday, September 9, 2020 at 11:08:08 AM UTC-7, legg wrote:> On Wed, 9 Sep 2020 10:26:14 -0700 (PDT), Edward Lee > <edward....@gmail.com> wrote: > > >On Wednesday, September 9, 2020 at 10:14:34 AM UTC-7, John Larkin wrote: > >> On Wed, 9 Sep 2020 08:42:20 -0700 (PDT), Edward Lee > >> <edward....@gmail.com> wrote: > >> > >> >On Wednesday, September 9, 2020 at 7:28:15 AM UTC-7, John Larkin wrote: > >> >> On Wed, 9 Sep 2020 05:21:42 -0700 (PDT), Edward Lee > >> >> <edward....@gmail.com> wrote: > >> >> >I can't figure out how to post new message with the new google group. A search of TL431 came up with this thread recently. So, i am high-jacking this for a quick question: > >> >> > > >> >> >> For isolated application, the feedback divider has to be secondary side only > >> >> >> and a TL431 used for error amp, into an opto, in the usual way. > >> >> > > >> >> >I need a 12V 5A High Current Shunt Regulator, using fig. 19 of page 7 > >> >> > > >> >> >https://www.onsemi.com/pub/Collateral/TL431-D.PDF > >> >> > > >> >> >I am using 10K for R1, 1.1K for R2. What should i use for Rbe of the pass transistor (TO-220 PNP)? > >> >> You could fry the TL431 at 5 amps out, from too much PNP base current. > >> > > >> >5A max for the AWG22 wires. Actual current may be couple of As for an instant. > >> > > >> >> A p-channel mosfet would help there, instead of the PNP. > >> > > >> >OK. > >> > > >> >> But the answer could be 5K either way. > >> > > >> >OK, thanks. > >> Actually, with the PNP, it doesn't need a b-e resistor. Once, about 60 > >> years ago, people used leaky germanium transistors, so using b-e > >> resistors became folklore. > > > >OK, i'll try a 5 ohm emitter resistor to limit the current. Once triggered, it will probably start to discharge into other cells, but that's fine. > Check your battery spec. A float voltage will seldom be 12V.Maximum is 12.6V for lithium battery.> You're looking for a series cell ballancing circuit . . ?Yes. each 12V module (3x 4.2V) has it's own BMS ballancing circuit. I just need to limit external voltage to 12V. 4 modules for 48V. 8 modules for 96V.
Reply by ●September 9, 20202020-09-09
onsdag den 9. september 2020 kl. 20.17.40 UTC+2 skrev Edward Lee:> On Wednesday, September 9, 2020 at 11:08:08 AM UTC-7, legg wrote: > > On Wed, 9 Sep 2020 10:26:14 -0700 (PDT), Edward Lee > > <edward....@gmail.com> wrote: > > > > >On Wednesday, September 9, 2020 at 10:14:34 AM UTC-7, John Larkin wrote: > > >> On Wed, 9 Sep 2020 08:42:20 -0700 (PDT), Edward Lee > > >> <edward....@gmail.com> wrote: > > >> > > >> >On Wednesday, September 9, 2020 at 7:28:15 AM UTC-7, John Larkin wrote: > > >> >> On Wed, 9 Sep 2020 05:21:42 -0700 (PDT), Edward Lee > > >> >> <edward....@gmail.com> wrote: > > >> >> >I can't figure out how to post new message with the new google group. A search of TL431 came up with this thread recently. So, i am high-jacking this for a quick question: > > >> >> > > > >> >> >> For isolated application, the feedback divider has to be secondary side only > > >> >> >> and a TL431 used for error amp, into an opto, in the usual way. > > >> >> > > > >> >> >I need a 12V 5A High Current Shunt Regulator, using fig. 19 of page 7 > > >> >> > > > >> >> >https://www.onsemi.com/pub/Collateral/TL431-D.PDF > > >> >> > > > >> >> >I am using 10K for R1, 1.1K for R2. What should i use for Rbe of the pass transistor (TO-220 PNP)? > > >> >> You could fry the TL431 at 5 amps out, from too much PNP base current. > > >> > > > >> >5A max for the AWG22 wires. Actual current may be couple of As for an instant. > > >> > > > >> >> A p-channel mosfet would help there, instead of the PNP. > > >> > > > >> >OK. > > >> > > > >> >> But the answer could be 5K either way. > > >> > > > >> >OK, thanks. > > >> Actually, with the PNP, it doesn't need a b-e resistor. Once, about 60 > > >> years ago, people used leaky germanium transistors, so using b-e > > >> resistors became folklore. > > > > > >OK, i'll try a 5 ohm emitter resistor to limit the current. Once triggered, it will probably start to discharge into other cells, but that's fine. > > Check your battery spec. A float voltage will seldom be 12V. > > Maximum is 12.6V for lithium battery. > > > You're looking for a series cell ballancing circuit . . ? > > Yes. each 12V module (3x 4.2V) has it's own BMS ballancing circuit. I just need to limit external voltage to 12V. 4 modules for 48V. 8 modules for 96V.sure you need the 12V limit? wouldn't it already be limited by the individual BMSs?
Reply by ●September 9, 20202020-09-09
On Wednesday, September 9, 2020 at 12:15:51 PM UTC-7, lang...@fonz.dk wrote:> onsdag den 9. september 2020 kl. 20.17.40 UTC+2 skrev Edward Lee: > > On Wednesday, September 9, 2020 at 11:08:08 AM UTC-7, legg wrote: > > > On Wed, 9 Sep 2020 10:26:14 -0700 (PDT), Edward Lee > > > <edward....@gmail.com> wrote: > > > > > > >On Wednesday, September 9, 2020 at 10:14:34 AM UTC-7, John Larkin wrote: > > > >> On Wed, 9 Sep 2020 08:42:20 -0700 (PDT), Edward Lee > > > >> <edward....@gmail.com> wrote: > > > >> > > > >> >On Wednesday, September 9, 2020 at 7:28:15 AM UTC-7, John Larkin wrote: > > > >> >> On Wed, 9 Sep 2020 05:21:42 -0700 (PDT), Edward Lee > > > >> >> <edward....@gmail.com> wrote: > > > >> >> >I can't figure out how to post new message with the new google group. A search of TL431 came up with this thread recently. So, i am high-jacking this for a quick question: > > > >> >> > > > > >> >> >> For isolated application, the feedback divider has to be secondary side only > > > >> >> >> and a TL431 used for error amp, into an opto, in the usual way. > > > >> >> > > > > >> >> >I need a 12V 5A High Current Shunt Regulator, using fig. 19 of page 7 > > > >> >> > > > > >> >> >https://www.onsemi.com/pub/Collateral/TL431-D.PDF > > > >> >> > > > > >> >> >I am using 10K for R1, 1.1K for R2. What should i use for Rbe of the pass transistor (TO-220 PNP)? > > > >> >> You could fry the TL431 at 5 amps out, from too much PNP base current. > > > >> > > > > >> >5A max for the AWG22 wires. Actual current may be couple of As for an instant. > > > >> > > > > >> >> A p-channel mosfet would help there, instead of the PNP. > > > >> > > > > >> >OK. > > > >> > > > > >> >> But the answer could be 5K either way. > > > >> > > > > >> >OK, thanks. > > > >> Actually, with the PNP, it doesn't need a b-e resistor. Once, about 60 > > > >> years ago, people used leaky germanium transistors, so using b-e > > > >> resistors became folklore. > > > > > > > >OK, i'll try a 5 ohm emitter resistor to limit the current. Once triggered, it will probably start to discharge into other cells, but that's fine. > > > Check your battery spec. A float voltage will seldom be 12V. > > > > Maximum is 12.6V for lithium battery. > > > > > You're looking for a series cell ballancing circuit . . ? > > > > Yes. each 12V module (3x 4.2V) has it's own BMS ballancing circuit. I just need to limit external voltage to 12V. 4 modules for 48V. 8 modules for 96V. > sure you need the 12V limit? wouldn't it already be limited by the individual BMSs?Yes, the BMS will cut-off over 12.6V, which would break the serial chain. I need to shunt it slightly below. This is only for charging.
Reply by ●September 9, 20202020-09-09
On Wed, 09 Sep 2020 11:08:49 -0700, John Larkin <snip>>>>Actually, with the PNP, it doesn't need a b-e resistor. Once, about 60 >>>years ago, people used leaky germanium transistors, so using b-e >>>resistors became folklore. >> >>It's still advisable for any npn running over it's Vce >>range at the temperature limit. > >Why?Because. I should have said ANY bipolar transistor, used in a power circuit. Leakage current is process controlled and pretty stable; that is to say - it is generally untested. Iceo is usually worse than Icbo, because it is generated by concurrent Icbo/beta effects. The emitter-base resistor avoids the effect on Icbo, by permitting a path for Icb that is not amplified - as I understand it. As with all silicon device leakage, it gets worse non- linearly, with temperature. In doing so - it adds to self heating which will aggravate a supposedly static condition. Local hot-spots on a wafer can develop. Most nondestructive Ice/Vce plots will show this effect as a 'negative resistance' slope at lower currents. This reduces between the stimulated conditions as Icbo becomes Icbx - from no bias to reverse bias - as will occur if some unaccounted for current is forced through an emitter-base resistor that is missing or inappropriately large. If this were a thyristor structure . . . Under transient conditions, the emitter-base resistor also aids in reducing miller charge effects, through the same mechanism, though saturation effects would dominate in a non-linear switching circuit. As the OP is anticipating a battery protection circuit, leakage current may only be a concern if connections remain, on the shelf. In a simple circuits like the OP's, where the TL431 can't be guaranteed 'off' above 1Vak, a path for it's stray current, to bypass the bipolar's base terminal, is only prudent. RL
Reply by ●September 9, 20202020-09-09
On Wed, 9 Sep 2020 11:12:19 -0700 (PDT), Edward Lee <edward.ming.lee@gmail.com> wrote: <snip>>> You'd normally want to keep the TL431 in linear operation. >> Minimum spec is Ik >= 1mA for bog standard TL431. There's >> no spec for Ik, out of regulation. >> >> Maximum Ik at 11V is about 30mA, before you'd get overheating. > >It will be much less than 11V for the TL431. I think it can handle 100mA.The emitter resistor is an ideal place to swot excess power in both the bipolar transistor and the TL431. RL
