Nice. Thyatrons were about the only component available for high-power control in the tube era. Today we have MOSFETs which approach ideal power switches, but it took a long time to get there.
As someone pointed out, that's a switching voltage regulator, not a switching power supply. The transformers there are all upstream of the switching.
I've restored five Teletype machines like the OP's Model 19 [1], so I've needed similar 120VDC 60mA power supplies. So I designed my own switching power supply.[2] This has a USB port for input, and a 120VDC 60mA output for directly driving the Teletype machine. It's powered entirely from the USB port.
This seemed impossible to some people. There's only 5V at less than 500mA coming in, and 120VDC 60mA out. But it's not impossible, because the load is inductive and intermittent. The selector magnet in old Teletypes has a huge inductance, about 5.5 Henries. (Not mH, H.). The 120VDC is only needed for about the first 1ms of each bit time, to force current through that huge inductance. By 5ms or so, you only need about 6V. So you can charge up a capacitor to get the initial 120V, then let a sustain supply take over.
My design is totally modern, built from surface mount components and in a small case.
Here's the schematic.[3] There's an explanation in [2].
It's been amusing to see the reaction of
the Teletype community. They like it, but most can't solder surface mount. One hobbyist is making
these things for others. I put the design on Github as open source and made a few for myself, and
I've sold some board kits. Not enough potential volume to have it manufactured.
Informally, here's how a switching power supply works. Everywhere else in electronics, you try to get rid of spikes. In switching power supplies, you make and use big ones. You start with a source of DC power, and you hook that to the primary winding of a transformer, with a switch so you can turn the power on and off. You turn the switch on, and current flows into the transformer. The magnetics in the transformer charge up, storing energy. After a while (milliseconds) the magnetics will saturate, and can't store any more energy. You now have a short circuit, DC going through a low-resistance transformer. But you turn off the switch before that happens. (Switching power supplies are always milliseconds from burnout, which is why they burn up if the switching fails.)
When you turn the switch off, you now have an open circuited inductor. The energy in that inductor has to go someplace. It comes out as a huge spike, in theory infinite voltage if the transformer resistance was zero, and in practice it can be a few hundred volts. It can't come out the primary, because the switch is open. So it comes out the transformer's secondary winding, where it's fed through a diode into a capacitor. There's the output.
It's simple. An old-style auto ignition with a coil and breaker points works this way. The problems come in as you make it well-behaved. First, controlling the switch is complicated. You want to open the switch before the transformer hits saturation. Failure to do this will burn something out. So there's usually current sensing. Then you want to turn the switch back on when the output voltage from the inductor drops below the voltage in the output capacitor, because no more current will flow through the diode after that.
That just makes it output power. Then you need output voltage sensing, which shortens the charging time to reduce output to maintain the desired voltage. You need protection to shut everything down if the switch gets stuck. (MOSFETs tend to fail in the ON state, and lack of good protection circuitry causes fires.)
This thing works by making big spikes at a few hundred kilohertz. That makes it a radio transmitter. You need inductors and bypass caps to prevent it from blithering all over the RF spectrum. Or sending spiky noise to its output or input. The bypass caps and inductors need to be close to the source of the spikes, so PC board layout really matters. These things will not work on a breadboard.
All this is why switching power supplies have so many small parts. Once you get it right, they work beautifully. Very high efficiency and low heat.
That reminds me of a funny story. The windmill I built worked well in medium and high winds, but did nothing but spin idly when the wind was low. Still, that's (a little) energy that you could capture in theory but it simply did not have enough voltage to get over the battery terminal voltage which makes it impossible to charge the battery.
But a windmill is mostly coils and magnets and when you short it it actually will charge the battery, briefly robbing the blades of some momentum. So, if you periodically short the coils using a bunch of powerfets and an oscillator you can charge a windmill in low wind conditions that would otherwise do nothing.
So far so good. Built it, tested it, worked like a charm. And then one day I decided to temporarily decouple the windmill from the switchboard, but I had forgotten about that little booster. FOOM, instant fire on the booster board after I pulled the switch. The FET circuitry and the oscillator had happily continued to work on the power provided by the windmill, and had allowed the end stage of the circuit to reach a very large multiple of the voltage that it normally dealt with because the battery kept the voltage pegged to a maximum of about 48V!
Needless to say that led to a somewhat more robust V2...
What you've built here is a rudimentary boost converter, using the motor inductance as your inductor, and your battery as your output capacitance.
The next step up here is to build a controllable device that can implement maximum power point tracking; a buck-boost power topology might be what you're looking for here.
Note that MPPT on a wind turbine is more difficult than, say solar, because the rotor speed is another state variable to consider. A naive/greedy algorithm might apply maximum torque to the rotor to extract maximum power for a moment, but this strategy will try to stall the rotor. As power is torque * angular velocity, both terms require consideration.
Thanks for your reply. We have a USB-powered current loop interface for the Teletypes; that's your design, I assume? If so, cool.
I figured it would be controversial to call the power supply a switching power supply, but I haven't seen a solid reason yet to exclude it. Putting a transformer upstream of the switching makes it an on-line power supply as opposed to an off-line power supply (dumb names, but I didn't make them). I'm not sure how you're distinguishing between a "switching voltage regulator" and a "switching power supply".
Oh, did you get the ones Steve Garrison makes up? That's my design. Or did someone else get the files off Github and make some?
A switching power supply has actual power conversion driven by the switching. See The Art of Electronics, by Horowitz and Hill, 3rd ed., section 9.6.
That thyratron circuit is a lamp dimmer circuit repurposed as a voltage regulator. Like SCRs and triacs, a thyratron is a switch you can't turn off. You have to wait for the input power to turn off. Usually that's the next cycle of AC. Because you can't turn off the power, you can't generate inductive spikes, so you can't pull the basic trick that make a switching power supply go.
There were some real switchers in the tube era. The most common one was used to generate the high voltage (10KV-20KV) for CRTs. Those used the horizontal oscillator, running at 15KHz and yanking the beam back at the end of each scan line, as a spike generator. That approach used a real vacuum tube, not a cold-cathode gas filled tube like a thyratron. So those were high voltage but low current devices.
Switching power supplies with serious current output had to wait for a component that could turn off fast under load. Power MOSFETS, etc. If you could do that with a thyratron, we would have had switching power supplies by 1950.
"I put the design on Github as open source and made a few for myself, and I've sold some board kits. Not enough potential volume to have it manufactured." - you could possibly have a look at services like macrofab etc. I used them to fab/assemble a single PCB not too long ago, which I was really pleased with.
Can't vacuum tubes such as krytrons still provide the ability to switch vast amount of current in the order of kiloamperes at kilovolts, which would be hard to use semiconductors for?
Apparently they were used in atomic bombs for delivering power to exploding-bridgewire detonators iirc.
The krytrons I've seen are too small to conduct that much current. The Wikipedia article refers to kiloampere currents ( https://en.wikipedia.org/wiki/Krytron ) but I don't see how that would work with the tube in their photograph. At long duty cycles you'd either vaporize the electrodes or fuse the wires, and at short duty cycles the parasitic inductance would be the limiting factor.
https://nuclear-knowledge.com/detonators.php provides more information, they are designed for fast switching, but still at vast currents re. triggered spark gaps "Typically, compact versions of these devices rate at 20-100 KV, and 50-150 kiloamps, and the triggering potential is one-half to one-third the maximum voltage. Switch current rise times last 10-100 nanoseconds. "
For krytron's specifically it says 'These devices have maximum voltage ratings from 3 to 10KV, and peak current rating of 300-3000 amps' which would have been useful for detonating the exploding-bridgewire, which requires a hefty current.
Good question. It's one of the recommended ones on the LT3750 data sheet.[1] I needed to charge up 2uF to 120V in 13ms or less, and the smallest of the Coilcraft transformers listed could do that. Matching controller, transformer, and MOSFET is a big headache; subtle properties of all of them matter. That data sheet is a good read.
Finding the right MOSFET was a huge headache. I kept trying reasonable ones in LTSpice, then on a real board. Gate capacitance of the MOSFET really matters. You normally think of MOSFET gates as drawing nearly zero power, but in a switcher, you want to turn them on fast, which means pumping in almost an amp for a few nanoseconds.
That IC is intended for charging up photoflash units. I'm using it at a lower voltage with a lower capacitance but a faster cycle time. The examples show charge times around 1 second; I only have 22ms. I'm only charging 2uF. It's two 1uF ceramic caps; none of the current limits of electrolytic caps. Not surface mount, though; I tried those new ceramic multilayer surface mount capacitors, but they have some very strange properties; the capacitance declines with voltage. OK in filters, terrible for energy storage.
It took me seven boards to get this working. The first few were a much simpler design with a 555 timer running the switcher. It worked, but it turned out I needed 2uF instead of 1uF because the Teletype selector magnet has an inductance larger than the ham community thought it did. The simpler design couldn't charge up 2uF in 22ms (one bit time); it took about 30-35ms. I had to start over with a more efficient design. This is all running off a USB port, so there's a limited power budget.
Running off USB port power added of complexity. There are strict rules about drawing power from USB ports, and if you violate them, even for a microsecond, the USB port turns off, and on many devices stays off until power cycled. That's a good thing; it's why hot-plugging works. The AP2553W6 manages startup current draw and has comparators checking for abnormal situations. It has a reverse current flow detector. Spikes from the switcher made it back into the power input and tripped the AP2553W6's protection. Had to add another surface mount ferrite bead, L1, to damp out current spikes. A lot of switcher design is about putting small capacitors and inductors in the right places to damp out trouble. Most of this you can see in LTSpice.
What you don't see in LTSpice is the effect of board layout. LTSpice assumes idealized wires with zero resistance, capacitance, inductance, and coupling. The layout around U1 really matters. First time around, I didn't follow the recommended layout, and the system would not oscillate.
The LTSpice model is on Github, along with the KiCAD files, so you can play with the parameters.
As someone pointed out, that's a switching voltage regulator, not a switching power supply. The transformers there are all upstream of the switching.
I've restored five Teletype machines like the OP's Model 19 [1], so I've needed similar 120VDC 60mA power supplies. So I designed my own switching power supply.[2] This has a USB port for input, and a 120VDC 60mA output for directly driving the Teletype machine. It's powered entirely from the USB port.
This seemed impossible to some people. There's only 5V at less than 500mA coming in, and 120VDC 60mA out. But it's not impossible, because the load is inductive and intermittent. The selector magnet in old Teletypes has a huge inductance, about 5.5 Henries. (Not mH, H.). The 120VDC is only needed for about the first 1ms of each bit time, to force current through that huge inductance. By 5ms or so, you only need about 6V. So you can charge up a capacitor to get the initial 120V, then let a sustain supply take over.
My design is totally modern, built from surface mount components and in a small case. Here's the schematic.[3] There's an explanation in [2].
It's been amusing to see the reaction of the Teletype community. They like it, but most can't solder surface mount. One hobbyist is making these things for others. I put the design on Github as open source and made a few for myself, and I've sold some board kits. Not enough potential volume to have it manufactured.
Informally, here's how a switching power supply works. Everywhere else in electronics, you try to get rid of spikes. In switching power supplies, you make and use big ones. You start with a source of DC power, and you hook that to the primary winding of a transformer, with a switch so you can turn the power on and off. You turn the switch on, and current flows into the transformer. The magnetics in the transformer charge up, storing energy. After a while (milliseconds) the magnetics will saturate, and can't store any more energy. You now have a short circuit, DC going through a low-resistance transformer. But you turn off the switch before that happens. (Switching power supplies are always milliseconds from burnout, which is why they burn up if the switching fails.)
When you turn the switch off, you now have an open circuited inductor. The energy in that inductor has to go someplace. It comes out as a huge spike, in theory infinite voltage if the transformer resistance was zero, and in practice it can be a few hundred volts. It can't come out the primary, because the switch is open. So it comes out the transformer's secondary winding, where it's fed through a diode into a capacitor. There's the output.
It's simple. An old-style auto ignition with a coil and breaker points works this way. The problems come in as you make it well-behaved. First, controlling the switch is complicated. You want to open the switch before the transformer hits saturation. Failure to do this will burn something out. So there's usually current sensing. Then you want to turn the switch back on when the output voltage from the inductor drops below the voltage in the output capacitor, because no more current will flow through the diode after that.
That just makes it output power. Then you need output voltage sensing, which shortens the charging time to reduce output to maintain the desired voltage. You need protection to shut everything down if the switch gets stuck. (MOSFETs tend to fail in the ON state, and lack of good protection circuitry causes fires.)
This thing works by making big spikes at a few hundred kilohertz. That makes it a radio transmitter. You need inductors and bypass caps to prevent it from blithering all over the RF spectrum. Or sending spiky noise to its output or input. The bypass caps and inductors need to be close to the source of the spikes, so PC board layout really matters. These things will not work on a breadboard.
All this is why switching power supplies have so many small parts. Once you get it right, they work beautifully. Very high efficiency and low heat.
[1] http://www.aetherltd.com [2] https://github.com/John-Nagle/ttyloopdriver [3] https://raw.githubusercontent.com/John-Nagle/ttyloopdriver/m...