So what? Do it without a regulator. https://www.seventransistorlabs.com/Images/Discrete_Tube_Supply.png I lie, there's a TL431. So what, it's like a single transistor (making this a "10"-transistor-lab product, alas; if you ignore the complementary follower and feedback, the core circuitry uses a mere seven however). Hmm, don't know if I have any pictures of a finished converter with this. Have built a few though. Works fine. Sometimes weird modes (subharmonics, poorly optimized compensation?), eh, it's simple. Nice thing about low gain devices (which I think includes the ancient Simpler Switchers, for better and for worse) is they don't make much for harmonics. I've got one of these on a shortwave radio and another on a Theremin, just CLCLC output filters is fine even for such sensitive purposes. Tim -- Seven Transistor Labs, LLC Electrical Engineering Consultation and Design Website: https://www.seventransistorlabs.com/ "John Larkin" <jlarkin@highland_atwork_technology.com> wrote in message news:79cqoehqeqmmiqt5ekuck5pe7a8r65anic@4ax.com...>I have a 48 volt power supply and I want to drive a lot of relays and > uPs and FPGAs and stuff, so I figured I'd knock it down to 12 volts > first. > > We have LM2567HV-ADJ in stock, a 52 KHz Simple Switcher probably > designed by druids during the last ice age. Figured I'd breadboard the > reg just for fun. A boy gets tired of typing all day. > > https://www.dropbox.com/sh/ajtqs7c1nswfhey/AABi7r0gchljjrxka4aHZItfa?dl=0 > > > Works pretty well, actually. Nothing gets very warm at 1 amp out. > > Yes, that unshielded drum core will spray field everywhere, but then I > am simulating alternators. >
stonehenge regulator
Started by ●September 26, 2019
Reply by ●September 28, 20192019-09-28
Reply by ●September 29, 20192019-09-29
Steve Wilson wrote...> On September 28, 2019, Steve Wilson wrote: >> On September 28, 2019, Winfield Hill wrote: >>> jlarkin@highlandsniptechnology.com wrote... >>>> On 28 Sep 2019, Winfield Hill wrote: >>>>>> >>>>>> ... The TVS would just limit damage downstream ... >>>>> >>>>> Exactly, my worry is the TVS, with its very high >>>>> dissipation, could fail. Maybe it would fail >>>>> shorted, but maybe not. An SCR running at 1V is >>>>> safer. If you really want to be safe, use the >>>>> serious fail-safe circuit Paul devised: >>>>> >>>>>https://www.dropbox.com/s/a33pelolwzrdv37/9x.7_crowbar.pdf?dl >>>> >>>> Way too complex to protect against a low-probability event. >>>> >>> It was protecting $8k of electronic PCBs. I thought >>> the impact in your case would be pretty dramatic as >>> well. A portion of the circuit might be sufficient. > > The previous version allowed the input to exceed the > 36V maximum of the TL431. Here's the fix. [ snip ]Posts using LTspice are hard to see, save file, open, etc. Some issues with your idea: (1) It's a voltage clamp, which must be fast, but also its control loop must be stable at high currents. (2) The Si7489DP FET's Vgs is limited to 20 volts. (3) If a fault persists for any length of time, the Si7489DP will overheat and fail. So you need to add a crowbar. Paul's circuit handles these issues, and also times actions carefully to avoid employing the crowbar, if the clamp can handle the problem and save the day. As a bonus, it turns off the source's AC power. It would have been nice to add some performance waveforms to the article. -- Thanks, - Win
Reply by ●September 29, 20192019-09-29
On 29 Sep 2019 12:17:17 -0700, Winfield Hill <winfieldhill@yahoo.com> wrote:>Steve Wilson wrote... >> On September 28, 2019, Steve Wilson wrote: >>> On September 28, 2019, Winfield Hill wrote: >>>> jlarkin@highlandsniptechnology.com wrote... >>>>> On 28 Sep 2019, Winfield Hill wrote: >>>>>>> >>>>>>> ... The TVS would just limit damage downstream ... >>>>>> >>>>>> Exactly, my worry is the TVS, with its very high >>>>>> dissipation, could fail. Maybe it would fail >>>>>> shorted, but maybe not. An SCR running at 1V is >>>>>> safer. If you really want to be safe, use the >>>>>> serious fail-safe circuit Paul devised: >>>>>> >>>>>>https://www.dropbox.com/s/a33pelolwzrdv37/9x.7_crowbar.pdf?dl >>>>> >>>>> Way too complex to protect against a low-probability event. >>>>> >>>> It was protecting $8k of electronic PCBs. I thought >>>> the impact in your case would be pretty dramatic as >>>> well. A portion of the circuit might be sufficient. >> >> The previous version allowed the input to exceed the >> 36V maximum of the TL431. Here's the fix. [ snip ] > > Posts using LTspice are hard to see, save file, open, etc. > > Some issues with your idea: > (1) It's a voltage clamp, which must be fast, but also > its control loop must be stable at high currents. > (2) The Si7489DP FET's Vgs is limited to 20 volts. > (3) If a fault persists for any length of time, the Si7489DP > will overheat and fail. So you need to add a crowbar. > > Paul's circuit handles these issues, and also times actions > carefully to avoid employing the crowbar, if the clamp can > handle the problem and save the day. As a bonus, it turns > off the source's AC power. It would have been nice to add > some performance waveforms to the article. >Maybe an updated version of Paul's circuit would be one tiny uP doing all the thinking. -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●September 29, 20192019-09-29
On Sunday, September 29, 2019 at 3:17:38 PM UTC-4, Winfield Hill wrote:> Steve Wilson wrote... > > On September 28, 2019, Steve Wilson wrote: > >> On September 28, 2019, Winfield Hill wrote: > >>> jlarkin@highlandsniptechnology.com wrote... > >>>> On 28 Sep 2019, Winfield Hill wrote: > >>>>>> > >>>>>> ... The TVS would just limit damage downstream ... > >>>>> > >>>>> Exactly, my worry is the TVS, with its very high > >>>>> dissipation, could fail. Maybe it would fail > >>>>> shorted, but maybe not. An SCR running at 1V is > >>>>> safer. If you really want to be safe, use the > >>>>> serious fail-safe circuit Paul devised: > >>>>> > >>>>>https://www.dropbox.com/s/a33pelolwzrdv37/9x.7_crowbar.pdf?dl > >>>> > >>>> Way too complex to protect against a low-probability event. > >>>> > >>> It was protecting $8k of electronic PCBs. I thought > >>> the impact in your case would be pretty dramatic as > >>> well. A portion of the circuit might be sufficient. > > > > The previous version allowed the input to exceed the > > 36V maximum of the TL431. Here's the fix. [ snip ]> Posts using LTspice are hard to see, save file, open, etc.Posts showing the ASC file are extremely useful. You seem to have managed. Unfortunately, it is difficult to include the PLT file to show the waveforms. Perhaps the solution is to zip the files and upload them to google drv. Try a different newsreader. I find XNews to be extremely useful to save any post that contains useful information, such as problems with ICs or other information.> Some issues with your idea: > (1) It's a voltage clamp, which must be fast, but also > its control loop must be stable at high currents.It is not a clamp. There is no control loop. It simply opens the FET when the input voltage exceeds the limit.> (2) The Si7489DP FET's Vgs is limited to 20 volts.I added a 12V zener from gate to src in later versions. Fixed.> (3) If a fault persists for any length of time, the Si7489DP > will overheat and fail. So you need to add a crowbar.Mosfets are available with milliohms of on resistance. This would take a lot of current to cause overheating. The problem would shift back to the source supply. A crowbar could make a bad situation worse. A better solution would be to measure the current and shut the FET off if it exceeds some limit. This would need to store the fault and provide a reset. An additional enhancement would be to check for undervoltage and turn off the FET. These additions would require some LEDs to indicate the problem and show the status.> Paul's circuit handles these issues, and also times actions > carefully to avoid employing the crowbar, if the clamp can > handle the problem and save the day. As a bonus, it turns > off the source's AC power. It would have been nice to add > some performance waveforms to the article.Paul's circuit is way too complex. Crowbars can cause severe damage. No need to shut off the power. Just shut off the FET. Run the ASC file and look at whatever waveforms you desire. Thanks for your reply.
Reply by ●September 29, 20192019-09-29
Steve Wilson wrote...> > On September 29, 2019, Winfield Hill wrote: > >> Some issues with your idea: >> (1) It's a voltage clamp, ... > > It is not a clamp. There is no control loop. It simply > opens the FET when the input voltage exceeds the limit.Excuse me, you are right. OK, that changes everything. -- Thanks, - Win
Reply by ●October 1, 20192019-10-01
On Friday, September 27, 2019 at 7:33:45 AM UTC-4, mpm wrote:> On Thursday, September 26, 2019 at 5:56:15 PM UTC-4, John Larkin wrote: > > I have a 48 volt power supply and I want to drive a lot of relays... > > And what's wrong with old tech? :) > > I just approved two designs with the LM2575HVT, another "simple switcher" part....One of my pet weekend projects is to breadboard the LM2575 (actually, using a PCB) and try about a dozen different values for the coil under various loading. I'd just like to get a good feel for the part, since it is dirt simple to use and is a low-freq switching design. Of course, I've had the coils for about a year now, and they are still sitting in the DigiKey box. I also wanted to characterize its EMI profile and see if I could get it to oscillate under some "off-datasheet conditions". :) In general, I think this "old tech" gets a bad rap sometimes. While better designs exist, the old ones are still pretty good! Although I can't remember the last time I used a 7805. :)
