I would like to experiment a bit with magnetic parametric amplifiers. For that purpose, I believe I need a 200kHz sine wave generator with a watt worth of output power. My obvious choice was to construct a current-fed resonant Royer oscillator. For a 1nF tank capacitor it implies a 633uH inductor (2x5 turns on a 6400nH/turn^2 way to big toroidal core), 2x ZTX851, a 100k base polarization resistor, 1 turn of feedback winding, 15 turns on the load winding. The current-mode choke is 7 turns on a 5500nH/t^2 core. The supply voltage is 8V. And it works like a charm, the output waveform is *very* close to a sine, 183kHz is also great for the first shot. But it works only when not loaded. Even a 910 resistor shunting the load winding is sufficient to kill the oscillations. Well, it still oscillates, but the waveform does not resemble anything typical. A train of weak wave packets with 2 maxima each, strange. There is something terribly wrong with my circuit, people are using it for muli-watt backlight applications without much problems. What proven oscillator design would you suggest using instead? Best regards, Piotr

# 200kHz oscillator

Started by ●May 2, 2017

Reply by ●May 2, 20172017-05-02

On Tue, 2 May 2017 19:56:46 +0200, Piotr Wyderski <peter.pan@neverland.mil> wrote:>I would like to experiment a bit with magnetic parametric amplifiers. >For that purpose, I believe I need a 200kHz sine wave generator with >a watt worth of output power.Most benctop function generators can just about do that. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com

Reply by ●May 2, 20172017-05-02

On Tuesday, May 2, 2017 at 1:56:55 PM UTC-4, Piotr Wyderski wrote:> I would like to experiment a bit with magnetic parametric amplifiers. > For that purpose, I believe I need a 200kHz sine wave generator with > a watt worth of output power. My obvious choice was to construct > a current-fed resonant Royer oscillator. For a 1nF tank capacitor > it implies a 633uH inductor (2x5 turns on a 6400nH/turn^2 way to > big toroidal core), 2x ZTX851, a 100k base polarization resistor, > 1 turn of feedback winding, 15 turns on the load winding. The > current-mode choke is 7 turns on a 5500nH/t^2 core. The > supply voltage is 8V. > > And it works like a charm, the output waveform is *very* close > to a sine, 183kHz is also great for the first shot. But it works > only when not loaded. Even a 910 resistor shunting the load winding > is sufficient to kill the oscillations. Well, it still oscillates, > but the waveform does not resemble anything typical. A train of > weak wave packets with 2 maxima each, strange. > > There is something terribly wrong with my circuit, people are > using it for muli-watt backlight applications without much problems. > > What proven oscillator design would you suggest using instead? > > Best regards, PiotrWhat kind of power? Voltage and current. I was thinking a sig. gen. and power opamp. George H.

Reply by ●May 2, 20172017-05-02

On Tue, 02 May 2017 19:56:46 +0200, Piotr Wyderski wrote:> I would like to experiment a bit with magnetic parametric amplifiers. > For that purpose, I believe I need a 200kHz sine wave generator with a > watt worth of output power. My obvious choice was to construct a > current-fed resonant Royer oscillator. For a 1nF tank capacitor it > implies a 633uH inductor (2x5 turns on a 6400nH/turn^2 way to big > toroidal core), 2x ZTX851, a 100k base polarization resistor, > 1 turn of feedback winding, 15 turns on the load winding. The > current-mode choke is 7 turns on a 5500nH/t^2 core. The supply voltage > is 8V. > > And it works like a charm, the output waveform is *very* close to a > sine, 183kHz is also great for the first shot. But it works only when > not loaded. Even a 910 resistor shunting the load winding is sufficient > to kill the oscillations. Well, it still oscillates, but the waveform > does not resemble anything typical. A train of weak wave packets with 2 > maxima each, strange. > > There is something terribly wrong with my circuit, people are using it > for muli-watt backlight applications without much problems. > > What proven oscillator design would you suggest using instead? > > Best regards, PiotrGenerate at low level, buffer, filter, amplify the s**t out of it. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com I'm looking for work -- see my website!

Reply by ●May 2, 20172017-05-02

Well... what V, I and Z were you expecting? Because it doesn't sound like much, assuming you chose the LC values intentionally. 1W at 50 ohms is 7V and 141mA, RMS. A Royer doesn't really work at extremely low Q, so let's say the minimum Q should be 3, or a parallel resonant tank of 16.7 ohms. Or 47nF and 13.3uH. To keep it going under heavier loading, you probably want much less than that, so the Q stays above 3 or 5, say, at the highest loading. An ungapped winding doesn't mean much, either. You need air to store energy! And you should probably use power MOSFETs, like a pair of IRF540. No need to worry about base current, or teensy BJTs puffing off when you inevitably short it out. :-) Tim -- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: http://seventransistorlabs.com "Piotr Wyderski" <peter.pan@neverland.mil> wrote in message news:oeah93$309$1@node1.news.atman.pl...>I would like to experiment a bit with magnetic parametric amplifiers. > For that purpose, I believe I need a 200kHz sine wave generator with > a watt worth of output power. My obvious choice was to construct > a current-fed resonant Royer oscillator. For a 1nF tank capacitor > it implies a 633uH inductor (2x5 turns on a 6400nH/turn^2 way to > big toroidal core), 2x ZTX851, a 100k base polarization resistor, > 1 turn of feedback winding, 15 turns on the load winding. The > current-mode choke is 7 turns on a 5500nH/t^2 core. The > supply voltage is 8V. > > And it works like a charm, the output waveform is *very* close > to a sine, 183kHz is also great for the first shot. But it works > only when not loaded. Even a 910 resistor shunting the load winding > is sufficient to kill the oscillations. Well, it still oscillates, > but the waveform does not resemble anything typical. A train of > weak wave packets with 2 maxima each, strange. > > There is something terribly wrong with my circuit, people are > using it for muli-watt backlight applications without much problems. > > What proven oscillator design would you suggest using instead? > > Best regards, Piotr

Reply by ●May 2, 20172017-05-02

On Tue, 02 May 2017 11:29:20 -0700, the renowned John Larkin <jjlarkin@highland_snip_technology.com> wrote:>On Tue, 2 May 2017 19:56:46 +0200, Piotr Wyderski ><peter.pan@neverland.mil> wrote: > >>I would like to experiment a bit with magnetic parametric amplifiers. >>For that purpose, I believe I need a 200kHz sine wave generator with >>a watt worth of output power. > >Most benctop function generators can just about do that.Yup. 10V peak ~= 7V RMS into 50 ohms is about 1W. Which is why the function generator output amplifiers need to be beefy. I had a look at one of the Agilent ones' output before sending it back for repair (wasn't the output section, I suspect it lost its calibration constants) .. parallel high frequency high performance op-amps IIRC. --sp -- Best regards, Spehro Pefhany

Reply by ●May 3, 20172017-05-03

On Wednesday, May 3, 2017 at 3:56:55 AM UTC+10, Piotr Wyderski wrote:> I would like to experiment a bit with magnetic parametric amplifiers. > For that purpose, I believe I need a 200kHz sine wave generator with > a watt worth of output power. My obvious choice was to construct > a current-fed resonant Royer oscillator.If it's resonant and produces a sine wave it isn't a Royer oscillator, but a Baxandall oscillator. http://sophia-elektronica.com/0344_001_Baxandal.pdf> For a 1nF tank capacitor > it implies a 633uH inductor (2x5 turns on a 6400nH/turn^2 way to > big toroidal core), 2x ZTX851, a 100k base polarization resistor, > 1 turn of feedback winding, 15 turns on the load winding. The > current-mode choke is 7 turns on a 5500nH/t^2 core. The > supply voltage is 8V.If you make the choke too inductive in a classical Baxandall oscillator it can "squeg". This only happens if you use bipolar transistors as switches, and doesn't happen if you use MOSFET switches (though start-up voltages can go rather high with a high feed inductor). With a supply voltage of 8V you can't just connect the gate of one MOSFET to the drain of the other - you get more than 20V between gate and source, and it can be even more during start-up. The simplest MOSFET driven circuits can be difficult to get to start up neatly - using a pair of bipolar transistors to drive the MOSFETs offers a tidy solution - see the oscillator part of the circuit at the bottom of the page. http://www.sophia-electronica.com/Baxandall_parallel-resonant_Class-D_oscillator1.htm> And it works like a charm, the output waveform is *very* close > to a sine, 183kHz is also great for the first shot. But it works > only when not loaded. Even a 910 resistor shunting the load winding > is sufficient to kill the oscillations. Well, it still oscillates, > but the waveform does not resemble anything typical. A train of > weak wave packets with 2 maxima each, strange.If you load a Baxandall enough, the harmonic content of the output goes up a lot, and you can kill the oscillation completely. The late Tony Williams had found that a Q higher then ten didn't give you a better sine wave, and a Q less than five gave you something less than good.> There is something terribly wrong with my circuit, people are > using it for muli-watt backlight applications without much problems.100k of base polarisation doesn't sound like much. Spice it and look at the actual currents.> What proven oscillator design would you suggest using instead?Baxandall should work fine, but you do have to think about what is going on. -- Bill Sloman, Sydney

Reply by ●May 3, 20172017-05-03

On a sunny day (Tue, 2 May 2017 19:56:46 +0200) it happened Piotr Wyderski <peter.pan@neverland.mil> wrote in <oeah93$309$1@node1.news.atman.pl>:>I would like to experiment a bit with magnetic parametric amplifiers. >For that purpose, I believe I need a 200kHz sine wave generator with >a watt worth of output power. My obvious choice was to construct >a current-fed resonant Royer oscillator. For a 1nF tank capacitor >it implies a 633uH inductor (2x5 turns on a 6400nH/turn^2 way to >big toroidal core), 2x ZTX851, a 100k base polarization resistor, >1 turn of feedback winding, 15 turns on the load winding. The >current-mode choke is 7 turns on a 5500nH/t^2 core. The >supply voltage is 8V. > >And it works like a charm, the output waveform is *very* close >to a sine, 183kHz is also great for the first shot. But it works >only when not loaded. Even a 910 resistor shunting the load winding >is sufficient to kill the oscillations. Well, it still oscillates, >but the waveform does not resemble anything typical. A train of >weak wave packets with 2 maxima each, strange. > >There is something terribly wrong with my circuit, people are >using it for muli-watt backlight applications without much problems. > >What proven oscillator design would you suggest using instead? > > Best regards, PiotrDo it the China way: http://panteltje.com/pub/inductive_coupling_real_power_300Vpp_IMG_6092.JPG :-)

Reply by ●May 4, 20172017-05-04

Jan Panteltje wrote...> > Do it the China way: > http://panteltje.com/pub/inductive_coupling_real_power_300Vpp_IMG_6092.JPGMore details, please. -- Thanks, - Win

Reply by ●May 4, 20172017-05-04

Den torsdag den 4. maj 2017 kl. 23.36.18 UTC+2 skrev Winfield Hill:> Jan Panteltje wrote... > > > > Do it the China way: > > http://panteltje.com/pub/inductive_coupling_real_power_300Vpp_IMG_6092.JPG > > More details, please.the pcb looks like one of those cheap chinese induction heater driver, based roughly on this: https://markobakula.files.wordpress.com/2012/10/royer_ih.png