Turbo Royer/Baxandall in boost configuration

It sort-of reminds me of the oscillator in the original touch-tone dial pad, although the AGC was a pair of silicon diodes in anti-parallel across a winding somewhere. The circuit had power gain, but no voltage gain, as I recall. Hmm. I think the feedback path was from emitter back to base of a single germanium transistor, biased using the drop across a silicon diode.

I have that circuit diagram somewhere. I think it was published in the BSTJ.

I think that they are optical now, versus ~LVDT.

The original economic niche in machine shops has been taken over by optical autocollimators. But there are still big things like bridges.

.

Joe Gwinn

It seems a Halfbridge converter would be a good fit

With 5V it's easy to drive, with high frequency the number of turns will be low. Increase efficiency by splitting the winding, maybe add external inductor for resonant LLC operation

Drive it from a microcontroller with 50 duty to avoid output inductor or do a phase shifted Halfbridge to be able to regulate the voltage if needed

Even if said gf enjoys winding toroids, you still have to mount it and identify/strip/terminate the leads. It doesn't take many turns or windings to get nasty.

(Mo enjoys knitting, and has made pilgrimages to upstate California and Ireland to meet sheep and get special wool. Turns out there is a famous sheep-shearer in our neighborhood.)

Here's a home-made transmission-line transformer, under 1 ns rise time. The connectors are surface-mount and the windings are a Digikey stock connectorized coax jumper. It takes a couple minutes to assemble on a board.

I like the dual-winding inductors, like DRQ127. You can do all sorts of fun stuff with them.

Here it is. They used a germanium transistor and varistors for amplitude control.

On 9/21/2021 4:00 PM, John Larkin wrote:

"stripping" enamel wire is the worst, burning and/or sanding more like

Looks like cell phone antenna connectors...

As a kinda interesting mod to your circuit, you can reduce the power in the base resistor for larger step-up ratios if you first increase its value, and then use a tap on the feedback winding to nudge the effective base supply voltage up a bit:

Version 4 SHEET 1 1148 680 WIRE -1232 -880 -1360 -880 WIRE -1120 -880 -1232 -880 WIRE -944 -880 -1056 -880 WIRE -752 -880 -944 -880 WIRE -576 -880 -752 -880 WIRE -368 -880 -512 -880 WIRE -128 -880 -368 -880 WIRE -368 -816 -368 -880 WIRE -752 -800 -752 -880 WIRE -128 -800 -128 -880 WIRE -752 -672 -752 -736 WIRE -368 -672 -368 -736 WIRE -1232 -512 -1232 -880 WIRE -560 -512 -1232 -512 WIRE -288 -512 -560 -512 WIRE 256 -496 96 -496 WIRE 560 -496 320 -496 WIRE 688 -496 560 -496 WIRE 832 -496 688 -496 WIRE -1472 -464 -1472 -512 WIRE 176 -400 0 -400 WIRE 256 -400 176 -400 WIRE 560 -400 560 -496 WIRE 560 -400 320 -400 WIRE -944 -352 -944 -880 WIRE -288 -352 -288 -512 WIRE 0 -352 0 -400 WIRE -1472 -336 -1472 -384 WIRE -560 -336 -560 -512 WIRE 560 -336 560 -400 WIRE 688 -272 688 -496 WIRE 832 -240 832 -496 WIRE 0 -208 0 -272 WIRE 96 -208 96 -496 WIRE 96 -208 0 -208 WIRE 560 -208 560 -272 WIRE 560 -208 96 -208 WIRE 560 -144 560 -208 WIRE -560 -96 -560 -272 WIRE -288 -96 -288 -272 WIRE -288 -96 -560 -96 WIRE 176 -80 176 -400 WIRE 256 -80 176 -80 WIRE 384 -80 320 -80 WIRE -288 0 -288 -96 WIRE 96 16 96 -208 WIRE 256 16 96 16 WIRE 384 16 384 -80 WIRE 384 16 320 16 WIRE 560 16 560 -80 WIRE 560 16 384 16 WIRE 688 16 688 -208 WIRE 688 16 560 16 WIRE 832 16 832 -160 WIRE 832 16 688 16 WIRE -944 48 -944 -272 WIRE -352 48 -944 48 WIRE 560 48 560 16 WIRE 560 64 560 48 WIRE 560 160 560 128 WIRE -288 176 -288 96 WIRE -128 176 -128 -720 WIRE -128 176 -288 176 WIRE -944 224 -944 48 WIRE -288 272 -288 176 WIRE -944 416 -944 288 WIRE -288 416 -288 352 FLAG -1360 -880 +5 IOPIN -1360 -880 In FLAG -288 416 0 FLAG -1472 -336 0 FLAG -1472 -512 +5 IOPIN -1472 -512 Out FLAG 560 160 0 FLAG -944 416 0 FLAG -368 -672 0 FLAG -752 -672 0 SYMBOL ind2 -272 -368 M0 WINDOW 3 -49 82 Left 2 SYMATTR InstName L1 SYMATTR Value 4.7µ SYMBOL ind2 16 -368 M0 SYMATTR InstName L2 SYMATTR Value 220µ SYMBOL ind2 -304 368 M180 WINDOW 0 36 80 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName L3 SYMATTR Value 1µ SYMBOL npn -352 0 R0 SYMATTR InstName Q1 SYMATTR Value 2SCR553P SYMBOL cap -544 -272 R180 WINDOW 0 24 56 Left 2 WINDOW 3 -86 38 Left 2 SYMATTR InstName C1 SYMATTR Value 0.47µ SYMBOL res -928 -256 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R3 SYMATTR Value 2.2k SYMBOL cap -928 288 R180 WINDOW 0 24 56 Left 2 WINDOW 3 24 8 Left 2 SYMATTR InstName C2 SYMATTR Value 0.022µ SYMBOL voltage -1472 -480 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V1 SYMATTR Value 5 SYMBOL cap 544 -144 R0 SYMATTR InstName C3 SYMATTR Value 0.1µ SYMBOL res 544 32 R0 SYMATTR InstName R1 SYMATTR Value 1Meg SYMBOL current 832 -240 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName I1 SYMATTR Value 0.005 SYMBOL cap 544 -336 R0 SYMATTR InstName C4 SYMATTR Value 0.1µ SYMBOL cap 672 -272 R0 SYMATTR InstName C5 SYMATTR Value 0.47µ SYMBOL schottky 320 0 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName D4 SYMATTR Value RB168L150 SYMATTR Description Diode SYMATTR Type diode SYMBOL schottky 320 -96 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName D1 SYMATTR Value RB168L150 SYMATTR Description Diode SYMATTR Type diode SYMBOL schottky 256 -480 R270 WINDOW 0 32 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName D2 SYMATTR Value RB168L150 SYMATTR Description Diode SYMATTR Type diode SYMBOL schottky 256 -384 R270 WINDOW 0 32 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName D3 SYMATTR Value RB168L150 SYMATTR Description Diode SYMATTR Type diode SYMBOL ind2 -144 -704 M180 WINDOW 0 36 80 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName L4 SYMATTR Value 1µ SYMBOL schottky -512 -896 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName D6 SYMATTR Value RB168L150 SYMATTR Description Diode SYMATTR Type diode SYMBOL res -384 -832 R0 SYMATTR InstName R2 SYMATTR Value 10k SYMBOL schottky -1120 -864 R270 WINDOW 0 32 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName D5 SYMATTR Value RB168L150 SYMATTR Description Diode SYMATTR Type diode SYMBOL cap -768 -800 R0 SYMATTR InstName C6 SYMATTR Value 4.7µ TEXT -1464 -216 Left 2 !.tran 30m startup uic TEXT -1432 -248 Left 2 !K L1 L2 L3 L4 0.99

I prefer that idea, these one and two transistor circuits are cute but pretty crude

Something like this is actually probably good enough, there won't be large load variations:

The nice thing about some GreenPAK devices is they have two sets of output pins, one rated to +5.5 and one rated to +12, with independent Vccs. So the thing can start up off +5 and then an aux winding can feed the +12 rail to drive the high-side transistor.

if you have 12V, IR2153 ?

Yes, that is self-running. But not easy to trim if you need to

On a sunny day (Tue, 21 Sep 2021 13:00:03 -0700) it happened John Larkin <jlarkin@highland_atwork_technology.com> wrote in snipped-for-privacy@4ax.com:

That soldering has me a bit worried...

The pad looks like a lot of thickness for heat to go through. Soldering it at a few points to pads would heatsink it and make it more robust.

The circuit I linked is a complete front-end showing a common use. Most of the other components are related to that , not for the basic oscillator. The only fundamental difference is the placement of the tank on the primary rather than the better position on the secondary.

The only way your circuit reduces the number of components is by scrimping on biasing components.

Your circuit doesn't have any compensation for component variations or the operating current.

It also does not have AGC, it relies upon saturation of the transistor to limit the oscillation amplitude.

As Phil Hobbs mentions his book that is not the ideal way to control the amplitude of an oscillator and comes with side effects that reduce the quality of the output.

kw ...

That's one of my iterations. Production units are prettier.

But it's perfectly reliable.

The grey stuff is 3G thermally conductive pad, 5 w/m-K. It really works. I roasted two generations of commercial inductors. Soldering "a few points" along the coil would still leave a lot of the coil basically uncooled, and the thermal contact areas would be small.

This is a 10 square inch, 7ns pulse width, 1400v, 5 MHz Pockels Cell driver. This coil, and some critical pcb traces, get hot from skin loss. The PCB is bolted to a water-cooled plate with more of the gap-pad goop.

The power semis are SiC fets on AlN insulators, driven by GaN fets. Fun project. I learned a lot.

The biasing is brilliant.

It does; it's just not obvious on casual inspection.

It does have AGC. Think about it.

This one can have a tiny flat on one sine excursion. If that matters, it is easily fixed.

The base resistor burns a lot of power for high step up ratios but you can cut that down as I posted FWIW

On a sunny day (Wed, 22 Sep 2021 07:39:02 -0700) it happened snipped-for-privacy@highlandsniptechnology.com wrote in snipped-for-privacy@4ax.com:

OK

Maybe I am thinking too much about G forces...

Through hole at the ends. And like someone suggested, more pads along the way to support the coil.

But personally I would go for a ceramic coil former with mounting bracket etc..

Yours is probably OK for just the lab table.

Just spend some hours with something I build long ago that needed a new Oled display. I had ordered some, but turns out although it is the same control chip it needs one byte different in the Oled ini. But the chip was soldered in, and all programming pins used for other things. So programmed a new PIC and put in an IC socket so I can easily change code now. Works fine, but was wired in my usual way, no PCB, so needed re-wiring.

On Wednesday, 22 September 2021 at 07:57:41 UTC-7, snipped-for-privacy@highlandsniptechnology.com wrote: ...

That's a matter of opinion. It doesn't temper component or temperature variations.

I know how it works - but the bias generated on the capacitor that reduces the conduction angle doesn't do enough to prevent saturation. It's not automatic level control in the same way that good quality oscillators utilize which keep the active element in its linear region.

Most BJT oscillators do self-biasing, whether they want to or not. Often JFET oscillators add an external diode to avoid forward biasing the gate junction but still provide the automatic biasing.

The circuit may fulfill its requirements very well, I'm not saying that it doesn't but to claim that it is a novel invention when the same design had been around for decades and was in common usage is stretching things. ...

kw