Re: [neonixie-l] Re: Using a standard cell phone charger (USB) as power supply for Nixie project
Hi everyone *It seems to me that if you wired it as an autotransformer, you'd get a 1:6 unit.* Hmm you're probably right, since the inductor discharges through both the primary and secondary winding. *Are you thinking of operating in flyback mode? * Yes, this is based on a modified boost converter, so energy will be transferred to the secondary only during (1-D). It seems that forward converters are more common than flyback converters but I would like to avoid the extra inductor and rectifier. *Looks like all it involves is a couple of capacitors, a FET, and a diode. Should be something you could add to an existing design, although it might be a technique that only applies to forward converters (I need to do more reading, apparently). * Active clamps can be used in any topology that use inductors with more than one winding, but the controllers with built-in driver for the auxiliary FET are meant for forward converters according to their data sheets. This is actually something I have been wondering about: *Is there a substantial difference in controllers meant for flyback or forward conversion? Or can such controller be used for in any topology? * It is indeed possible to implement the auxiliary driver with discrete components, but I don't think it is a good idea, since the dead-band in between must be controlled extremely carefully. Otherwise the dissipation in the switch will be extreme. *but I'm unsure why ringing would be a problem.* When the switch closes the current in the leakage inductance (which is in series with the switch) don't have anywhere to go. Instead the voltage will increase which just might destroy the switch completely, or at least shorten its life time. A more detailed analysis reveals that the leakage inductance will actually resonate with the output capacitance of the (closed) switch. By adding an RC snubber network in parallel the ringing can be damped in several different ways (under-, critical- and overdamped). This type of snubber will however consume som energy which will reduce efficiency. Another bad effect of the ringing is that the transfer of energy from the magnetizing inductance to the secondary will not start until the potential at the midpoint of the coupled inductor (transformer) has reached the reflected output voltage. In simpler words this means that the energy will not be transferred efficiently until the ringing has ended. Also the ringing will be a good source of EMI. This might not be a huge issue in hobby electronics, but now that I know about it I can just not forget about it =) * * *There's a nice discussion of snubbers here: http://softsolder.com/2009/03/06/rc-snubber-resonant-design/* This was a great reference, and that is the way I would proceed with the design of an RC snubber network, at least when it comes to the measurements. I do think that the text lacks a bit of the details, and I would probably do an analysis in the laplace-domain, see how the poles move when R and C is changed (root locus method) and choose their values based on that. If the RC snubber don't catch the peak voltage I might need to put an RCD snubber across the primary winding, but I think simulation in Spice will reveal that. As you see this is actually a quite advanced procedure; with active clamp there is just one clamping capacitor that I need to choose. I also think that the size of the clamp capacitor is not as dependent on stray capacitance either. Best Regards Anton -- You received this message because you are subscribed to the Google Groups neonixie-l group. To post to this group, send an email to neonixie-l@googlegroups.com. To unsubscribe from this group, send email to neonixie-l+unsubscr...@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msg/neonixie-l/-/SzB6R8iwUh8J. For more options, visit https://groups.google.com/groups/opt_out.
Re: [neonixie-l] Re: Using a standard cell phone charger (USB) as power supply for Nixie project
Hi Everyone Here is a small update on progress. Last couple of months have been busy at work, but I have been able to spend some time thinking about this project. The best source of multi winding inductors I have found so far is the Versa-Pac series from Cooper Busman. They come with 6 identical windings and properly connected they will give me a 1:5 autotransformer. In theory this will reduce the duty cycle from a whopping 97.5% to the somewhat more manageable 86.7%. I have spent a considerable time reading about different kinds of snubbers. Just when I thought that I had found an optimal way of designing RC- and RCD-snubbers for the switch and the rectifier I got notice of far more modern alternatives: active clamps. But so far I have only found one such controller that can be driven from a 5V supply, but the carrier is not very easy to hand-solder, and in any case the maximum duty cycle is just 74% due to current-mode implementation. I guess that a good old voltage-mode controller will have to do. My requirements on the quality of the regulated output is not very high anyway. When I look at the few exemples of tapped inductor boost converter that provide any kind of schematic I have not seen any kind of snubber at all, except for the secondary side rectifier diode. Is this just a simplification for sake of presentation clarity, or can it really be omitted? My plan, so far, is to draw snubber networks for the diode and switch just in case, and just don't put them on the PCB if they prove redundant. With some strategic test points I can measure the leakage inductance of the autotransformer and this should be a good starting point for an almost optimal design. It seems however that the leakage can be measured in different ways. How would the members of the group proceed with such measurement? This became quite some texts, but I guess that my main questions at this point boild down to: Is there any point in considering more advanced topologies such as active clamp and active rectification? To which extent are snubber networks necessary? Best Regards Anton -- You received this message because you are subscribed to the Google Groups neonixie-l group. To post to this group, send an email to neonixie-l@googlegroups.com. To unsubscribe from this group, send email to neonixie-l+unsubscr...@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msg/neonixie-l/-/AU4Ie0xGS3MJ. For more options, visit https://groups.google.com/groups/opt_out.
Re: [neonixie-l] Re: Using a standard cell phone charger (USB) as power supply for Nixie project
If you're going charlieplexed, then you'll be lighting only one cathode at a time. Depending, on your overall design, that might mean one cathode ON, at any time, period. What kind of nixie are you using ? You may actually, need much less than that 10mA, you originally specified. If so, you have a little more wiggle room, in your design. Well yes, the tubes will be multiplexed. My plan is to make the converter fairly general to support most medium sized tubes. In the first batch I will most likely use IN-8's. The nominal current is ca 2.5 mA so with a 4 tube clock I should need 10 mA to get the same brightness. I do think that it might be (far) too bright for use during the night, but I reckon that I can control that with a lower duty cycle for either the anode or cathode drivers. I haven't completed the design yet, but if it turns out to be too difficult to get a full 10 mA at 200 V then it is probably not a big deal. /Anton -- You received this message because you are subscribed to the Google Groups neonixie-l group. To post to this group, send an email to neonixie-l@googlegroups.com. To unsubscribe from this group, send email to neonixie-l+unsubscr...@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msg/neonixie-l/-/h1qZqjixZqYJ. For more options, visit https://groups.google.com/groups/opt_out.
Re: [neonixie-l] Re: Using a standard cell phone charger (USB) as power supply for Nixie project
On Friday, August 3, 2012 12:32:45 PM UTC-7, quanton wrote: ... I plan to use charlie-plexed cathode drivers driven by the uC directly ... Best Regards Anton If you're going charlieplexed, then you'll be lighting only one cathode at a time. Depending, on your overall design, that might mean one cathode ON, at any time, period. What kind of nixie are you using ? You may actually, need much less than that 10mA, you originally specified. If so, you have a little more wiggle room, in your design. -- You received this message because you are subscribed to the Google Groups neonixie-l group. To post to this group, send an email to neonixie-l@googlegroups.com. To unsubscribe from this group, send email to neonixie-l+unsubscr...@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msg/neonixie-l/-/eDy_9S0jt8oJ. For more options, visit https://groups.google.com/groups/opt_out.
Re: [neonixie-l] Re: Using a standard cell phone charger (USB) as power supply for Nixie project
A flyback transformer seems to give higher conversion ratios, but I am puzzled about it being an isolated topology by nature. Yeah, a transformer can give you an isolated output, but then voltage feedback is more complicated. Also, transformers are harder to find than plain inductors, and have more parameters to play with (for example, most flyback converters use transformers with a gapped core). A tapped inductor boost converter might be just what I need. It is very elegant really, split the inductor in two and connect the switch to the center tap. Sometimes such inductor is called 'autotransformer' since only one winding acting on itself. When the energy of the magnetic field is dumped during the discharge period there will be a substantial voltage gain since the number of turns in the second part of the inductor is greater. Right. 2, There does not seem to be that many inductors available seems limited at best. Quite true. You have four basic choices here. One is to try to find a stock transformer that does what you want - as you've seen, this can be tricky. Another is to take a basic inductor, and add some turns on top of the winding, and use those turns as the primary - there's a lot of trial and error involved, and some learning on magnetics*. The third step is to wind your own transformer from the ground up - having a coil winding machine is a help (our own David Forbes has taken this approach). The fourth one, which I am in the process of investigating, is to use a universal transformer - these have six identical windings, which can be connected in series and parallel in various combinations in order to implement a variety of transformer functions. One example is Digikey 732-2449-1-ND. Maybe I am just using the wrong phrases when I search. Any ideas on suitable inductors are appreciated. One approach I use is to look up the example circuits put up by the chip manufacturers and examine the part numbers and manufacturers of the transformers used there. While a Pulse Engineering gobblydegook may not be a line item at Digikey, it's worth asking Pulse Engineering about them. * Wurth Electronics used to offer a dandy set of books, among them ABCs of Transformers (Digikey 732-1415-ND) for $18 and that explained a lot of useful concepts. They seem to have discontinued that one, and have combined them, along with some new material, into a single book called Trilogy of Inductors (Digikey 732-1414-ND), which is also discontinued, and replaced it with Trilogy of Magnetics (Digikey 732-2511-ND), that covers a lot more ground, but is $72. - John -- You received this message because you are subscribed to the Google Groups neonixie-l group. To post to this group, send an email to neonixie-l@googlegroups.com. To unsubscribe from this group, send email to neonixie-l+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
Re: [neonixie-l] Re: Using a standard cell phone charger (USB) as power supply for Nixie project
One more thing, that I'm always repeating If you find yourself needing an obscure item from an obscure manufacturer that is not sold by digikey or mouser, don't be afraid to call up the manufacturer and ask for a sample. They won't sell it to you directly (probably.. unless you want 50,000 of them anyways) but will almost always send you a couple of them if you tell them that you're prototyping a new design. -Adam On Sat, Aug 4, 2012 at 9:09 AM, John Rehwinkel jreh...@mac.com wrote: A flyback transformer seems to give higher conversion ratios, but I am puzzled about it being an isolated topology by nature. Yeah, a transformer can give you an isolated output, but then voltage feedback is more complicated. Also, transformers are harder to find than plain inductors, and have more parameters to play with (for example, most flyback converters use transformers with a gapped core). A tapped inductor boost converter might be just what I need. It is very elegant really, split the inductor in two and connect the switch to the center tap. Sometimes such inductor is called 'autotransformer' since only one winding acting on itself. When the energy of the magnetic field is dumped during the discharge period there will be a substantial voltage gain since the number of turns in the second part of the inductor is greater. Right. 2, There does not seem to be that many inductors available seems limited at best. Quite true. You have four basic choices here. One is to try to find a stock transformer that does what you want - as you've seen, this can be tricky. Another is to take a basic inductor, and add some turns on top of the winding, and use those turns as the primary - there's a lot of trial and error involved, and some learning on magnetics*. The third step is to wind your own transformer from the ground up - having a coil winding machine is a help (our own David Forbes has taken this approach). The fourth one, which I am in the process of investigating, is to use a universal transformer - these have six identical windings, which can be connected in series and parallel in various combinations in order to implement a variety of transformer functions. One example is Digikey 732-2449-1-ND. Maybe I am just using the wrong phrases when I search. Any ideas on suitable inductors are appreciated. One approach I use is to look up the example circuits put up by the chip manufacturers and examine the part numbers and manufacturers of the transformers used there. While a Pulse Engineering gobblydegook may not be a line item at Digikey, it's worth asking Pulse Engineering about them. * Wurth Electronics used to offer a dandy set of books, among them ABCs of Transformers (Digikey 732-1415-ND) for $18 and that explained a lot of useful concepts. They seem to have discontinued that one, and have combined them, along with some new material, into a single book called Trilogy of Inductors (Digikey 732-1414-ND), which is also discontinued, and replaced it with Trilogy of Magnetics (Digikey 732-2511-ND), that covers a lot more ground, but is $72. - John -- You received this message because you are subscribed to the Google Groups neonixie-l group. To post to this group, send an email to neonixie-l@googlegroups.com. To unsubscribe from this group, send email to neonixie-l+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out. -- You received this message because you are subscribed to the Google Groups neonixie-l group. To post to this group, send an email to neonixie-l@googlegroups.com. To unsubscribe from this group, send email to neonixie-l+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
Re: [neonixie-l] Re: Using a standard cell phone charger (USB) as power supply for Nixie project
On 8/3/12 9:10 AM, Nick wrote: Do the sums - 200V @ 10mA == 5V @ 400mA with 100% efficiency. However, even the best supplies are about 85% efficient (some slightly better), which will mean 470mA or thereabouts on the input side - very close to the 500mA limit (yes , I know that this is not being driven from a PC), Note that for USB the 500mA (USB 2) or 600mA (USB 3) number is only for a powered hub port after negotiation - unpowered hubs have only a single unit load (100mA) available under all versions of the USB spec. http://en.wikipedia.org/wiki/Universal_Serial_Bus#Power Nick. Nick, He's not proposing to power it from a computer, but from a charger. Those make more power than a USB hub will provide. -- David Forbes, Tucson AZ -- You received this message because you are subscribed to the Google Groups neonixie-l group. To post to this group, send an email to neonixie-l@googlegroups.com. To unsubscribe from this group, send email to neonixie-l+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
Re: [neonixie-l] Re: Using a standard cell phone charger (USB) as power supply for Nixie project
On 8/3/12 9:15 AM, Nick wrote: On Friday, 3 August 2012 17:12:49 UTC+1, nixiebunny wrote: On 8/3/12 9:10 AM, Nick wrote: Do the sums - 200V @ 10mA == 5V @ 400mA with 100% efficiency. He's not proposing to power it from a computer, but from a charger. Ummm. note my comment yes , I know that this is not being driven from a PC... It was a general comment about the risks of using USB ports... Nick Your point being that you'll find out whether your computer makes smoke or not if its USB port is overloaded? I remember reading that PC USB ports are supposed to automatically shut down on overload, but I don't know how well that attribute is tested by China Inc. -- David Forbes, Tucson AZ -- You received this message because you are subscribed to the Google Groups neonixie-l group. To post to this group, send an email to neonixie-l@googlegroups.com. To unsubscribe from this group, send email to neonixie-l+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
Re: [neonixie-l] Re: Using a standard cell phone charger (USB) as power supply for Nixie project
On Friday, 3 August 2012 17:23:57 UTC+1, nixiebunny wrote: Your point being that you'll find out whether your computer makes smoke or not if its USB port is overloaded? I remember reading that PC USB ports are supposed to automatically shut down on overload, but I don't know how well that attribute is tested by China Inc. As most boards are made in Taiwan or China, I suspect that they are mostly Ok - they tend to use polyswitches or similar to self-reset after a bit. However, sticking an HV SMPS which may or may not protect its input onto a computer port may have exciting consequences (or may be perfectly fine). ;-) Nick -- You received this message because you are subscribed to the Google Groups neonixie-l group. To post to this group, send an email to neonixie-l@googlegroups.com. To unsubscribe from this group, send email to neonixie-l+unsubscr...@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msg/neonixie-l/-/PHCFenfZYmwJ. For more options, visit https://groups.google.com/groups/opt_out.
Re: [neonixie-l] Re: Using a standard cell phone charger (USB) as power supply for Nixie project
Hi Everyone I have looked more into this during the day. The performance of John's flyback converter is indeed impressive but since space is extremely limited this time I will need to implement the SMPS on the main (only) PCB. I think that it will be more fun that way too =) A flyback transformer seems to give higher conversion ratios, but I am puzzled about it being an isolated topology by nature. I plan to use charlie-plexed cathode drivers driven by the uC directly and I don't want to use transformers or optocouplers to isolate so many signals. Admittedly I haven't looked too much into flyback converters, but if it is not possible to connect the grounds on the primary and secondary side I don't see how this path is feasible. Some weeks ago I stumbled over some interresting app-notes from Maxim and Linear that described a simple modification that can be made to the simple boost topology. http://www.maxim-ic.com/app-notes/index.mvp/id/1109 http://www.edn.com/design/power-management/4317951/Tapped-inductor-boost-regulator-deliver-high-voltage A tapped inductor boost converter might be just what I need. It is very elegant really, split the inductor in two and connect the switch to the center tap. Sometimes such inductor is called 'autotransformer' since only one winding acting on itself. When the energy of the magnetic field is dumped during the discharge period there will be a substantial voltage gain since the number of turns in the second part of the inductor is greater. 1, Does anyone have experience in this or a similar topology? 2, There does not seem to be that many inductors available seems limited at best. Maybe I am just using the wrong phrases when I search. Any ideas on suitable inductors are appreciated. Best Regards Anton -- You received this message because you are subscribed to the Google Groups neonixie-l group. To post to this group, send an email to neonixie-l@googlegroups.com. To unsubscribe from this group, send email to neonixie-l+unsubscr...@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msg/neonixie-l/-/2GgWifpC47EJ. For more options, visit https://groups.google.com/groups/opt_out.
Re: [neonixie-l] Re: Using a standard cell phone charger (USB) as power supply for Nixie project
On 12-08-03 12:23 PM, David Forbes wrote: I remember reading that PC USB ports are supposed to automatically shut down on overload, but I don't know how well that attribute is tested by China Inc. the easiest way for the Computer maker to do this is just to connect directly from the 5V and many amps output of the Computer supply to the USB port, and program the BIOS to just say yes and otherwise ignore the request for more power from the USB device. I am not sure how you can ensure that someone does not plug your device into a computer, even just to test it if I does not come on. A half amp fuse in the 5V input would be a a great idea for starters. -- Charles MacDonald Stittsville Ontario cm...@zeusprune.ca Just Beyond the Fringe http://users.trytel.com/~cmacd/tubes.html No Microsoft Products were used in sending this e-mail. -- You received this message because you are subscribed to the Google Groups neonixie-l group. To post to this group, send an email to neonixie-l@googlegroups.com. To unsubscribe from this group, send email to neonixie-l+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
