Author Topic: "Slayer exciter" analysis  (Read 5206 times)

Offline acmq

  • High Voltage Enthusiast
  • *
  • Posts: 15
  • Karma: +2/-0
    • View Profile
"Slayer exciter" analysis
« on: June 30, 2020, 05:13:57 PM »
Looking in the Internet I found many incorrect descriptions about how this circuit works, and so made a precise analysis to see what happens.
First, solving the confusion about winding directions of the coils, it's obvious that any combination of directions can be used, if the primary coil is correctly connected:



A simulation of the circuit, with some idealizations to simplify the interpretation, results in the following ideal waveforms:



It's assumed that the output voltage is at 1000 V initially, and that the current through the resistor (that serves just for startup) is negligible. The transistor is an ideal switch.
The output voltage is practically a cosinusoid at the resonance frequency of L2 with its distributed capacitance, of the coil and of the top load.
The base voltage is a square wave, positive when the transistor conducts.
The collector voltage is almost zero when the transistor conducts, has a large peak when it ceases to conduct (this is what heats the transistor), and then becomes negative and rises a bit when the transistor is not conducting, due to the action of the transformer.
The current in the secondary coil L2 is almost sinusoidal, and controls when the transistor conducts or not. When the transistor is conducting it flows to the base of the transistor. When it is not conducting it flows through the LED. Has a small step when the transistor ceases to conduct.
The current in the primary coil is a ramp added to a sinusoid when the transistor conducts.

A (very) detailed analysis, with the oscillator used as transmitter for "wireless energy transfer" experiments: http://www.coe.ufrj.br/~acmq/tesla/WirelessEnergy.pdf
« Last Edit: June 30, 2020, 05:18:46 PM by acmq »

Offline Weston

  • High Voltage Technician
  • ***
  • Posts: 132
  • Karma: +11/-0
    • View Profile
Re: "Slayer exciter" analysis
« Reply #1 on: June 30, 2020, 07:54:40 PM »
Nice write up! A lot of bad information about the slayer exciter online.

To improve efficiency I don't think you need something as complicated quasi-resonant snubber. You should be able to tune the coil as in Class-E, where an added capacitor across C-E of the BJT resonates with the primary leakage inductance to recycle the energy and give zero voltage turn on.

Offline acmq

  • High Voltage Enthusiast
  • *
  • Posts: 15
  • Karma: +2/-0
    • View Profile
Re: "Slayer exciter" analysis
« Reply #2 on: July 01, 2020, 02:47:13 AM »
Nice write up! A lot of bad information about the slayer exciter online.

To improve efficiency I don't think you need something as complicated quasi-resonant snubber. You should be able to tune the coil as in Class-E, where an added capacitor across C-E of the BJT resonates with the primary leakage inductance to recycle the energy and give zero voltage turn on.

The snubber studied in the document gave uncertain results, mostly due to the approximations used. I tried the capacitor tuning the primary. An ideal simulation says that the idea should work, but in practice it doesn't. I prepared a setup using the largest coil shown in the document, using a neon lamp suspended at some distance to verify if there is some change in the output. What happened is that it's possible to observe a slight resonance looking at the collector waveform, similar to the simulation, but the output falls dramatically when any significant capacitance is put there. Investigating why.
« Last Edit: July 01, 2020, 02:48:58 AM by acmq »

Offline T3sl4co1l

  • High Voltage Technician
  • ***
  • Posts: 174
  • Karma: +9/-0
    • View Profile
    • Seven Transistor Labs
Re: "Slayer exciter" analysis
« Reply #3 on: July 01, 2020, 06:25:30 AM »
Can clamp the collector voltage by using a CT winding, well coupled (bifilar or better), with a diode up from ground to the free end of the winding.  Like the top left part of this, https://www.seventransistorlabs.com/Images/Mag_Amp2.png but self-excited, of course.

This reduces the problem from a matter of L1's leakage (considerable, because it can't be very well coupled to an L2 of any useful size), to a matter of the leakage between the ends of the winding (which can be quite good, say k > 0.98 or so?).

Alternately, if the transistors can be arranged in series symmetrically, then when both of them switch off, each end of the coil flies back towards the opposite rail, where a single catch diode can be used.  This is called a 2-switch converter, and is commonly seen in modern computer PSUs (with PFC, "80 PLUS" rating and such).  Unfortunately, driving the high side transistor requires additional circuitry.

So it's better to just use two transistors symmetrically, in push-pull -- the usual "ZVS" driver circuit.  Often erroneously called Royer, but that is commutated by magnetic saturation, not resonance; it's actually a Baxandall oscillator (yes, the one famous for an audio tone control, among many other things).  In this case, the feedback is magnetic, which is fine (just a few turn sense winding).


The snubber studied in the document gave uncertain results, mostly due to the approximations used. I tried the capacitor tuning the primary. An ideal simulation says that the idea should work, but in practice it doesn't. I prepared a setup using the largest coil shown in the document, using a neon lamp suspended at some distance to verify if there is some change in the output. What happened is that it's possible to observe a slight resonance looking at the collector waveform, similar to the simulation, but the output falls dramatically when any significant capacitance is put there. Investigating why.

It's a tricky situation, because you're trying to double-tune a well-coupled network, while modulating the impedance on one end of it (the transistor is alternately saturated (~0Ω impedance) and open).

Double-tuning is alright if you have well defined impedances; you can peak the response at critical coupling.  You still might not need critical coupling, as long as the secondary gets enough voltage at one or the other resonant peak (overcoupled).  But what does it mean, to have a source that's PWM'd between zero and infinite impedance?  You don't magically get a real impedance out of that.  Maybe you do?  I don't know, I'd have to think about it a lot.  I think it's at a point where you fundamentally must approach the hard problem of a nonlinear system, i.e. where LTI analysis is utterly insufficient.


Hmm...

So, if you make the constraints that:
1. For it to be called "class E operation", the switch load must be:
a. Resistive to inductive at the fundamental frequency,
b. Resonant, so that harmonics are reflected back (i.e., as negative current during part of the switching phase, thus recycling that reactive energy into the supply); and so, consequently,
c. Capacitive in parallel, which allows us to use semiconductor switches like BJTs and MOSFETs, with antiparallel diodes and relatively high output capacitance (Ccb / Coss).
2. Since the waveform is fixed, there isn't much plasticity, i.e., it has a low impedance.  At least near the fundamental.  Whatever's left will dominate the equivalent impedance.

That must be where the key is; the fundamental might not have much room to move, but it's all squeezed into the harmonics.  The resonant peak can be shorter and taller, or longer and flatter; it can be more or less convex on its return.  I've not actually read up on harmonic balance analysis, but this must be germ of the method, huh.

So you'd have to figure that out, and that's your source impedance.  You need the source impedance to figure out how resonant-tank-ly the primary circuit behaves.  If it's got quite a low impedance, it may not act much at all as a double-tuned network, which should be convenient for tuning purposes.

Tim

Offline acmq

  • High Voltage Enthusiast
  • *
  • Posts: 15
  • Karma: +2/-0
    • View Profile
Re: "Slayer exciter" analysis
« Reply #4 on: July 03, 2020, 03:01:56 AM »
Can clamp the collector voltage by using a CT winding, well coupled (bifilar or better), with a diode up from ground to the free end of the winding.  Like the top left part of this, https://www.seventransistorlabs.com/Images/Mag_Amp2.png but self-excited, of course.
Again, a simulation says that the idea should work, but in practice little difference is seen, and there is a reduction in the output, worse with slow transistors. I had made a bifilar coil for other purpose, but it seems adequate for this use. The coupling is not perfect but seems good enough. The consumed power is slightly smaller with the snubber, depending on the transistor used, but it appears that the gain is at the cost of smaller output power, as the transistor continues hot. The problem with all snubbers appear to be related to the presence of the transformer. When the primary current is interrupted and diverted from the transistor some energy is drained from the secondary. I am simulating the circuits with LTSPICE, but the transistor models there have some strange behaviors, as not showing this.

With snubber:


Without snubber:


High Voltage Forum

Re: "Slayer exciter" analysis
« Reply #4 on: July 03, 2020, 03:01:56 AM »

 


* Recent Topics and Posts

post Re: Re-chargeable 1.5 volt lithium ion AAA batteries
[General Chat]
MRMILSTAR
Today at 04:47:35 AM
post Re: Re-chargeable 1.5 volt lithium ion AAA batteries
[General Chat]
davekni
Today at 03:59:27 AM
post Re: Kaizer VTTC 1
[Vacuum Tube Tesla Coils (VTTC)]
MRMILSTAR
March 28, 2024, 09:15:11 PM
post Re: capacitor and diodes. Voltage values for a CW
[Voltage Multipliers]
Alberto
March 28, 2024, 01:01:12 PM
post Re: Big Coil Build Log
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
March 28, 2024, 05:47:34 AM
post Re: capacitor and diodes. Voltage values for a CW
[Voltage Multipliers]
davekni
March 28, 2024, 04:45:07 AM
post Re: capacitor and diodes. Voltage values for a CW
[Voltage Multipliers]
MRMILSTAR
March 28, 2024, 04:18:27 AM
post Push Pull VTTC
[Vacuum Tube Tesla Coils (VTTC)]
janno288
March 28, 2024, 01:10:08 AM
post Re: capacitor and diodes. Voltage values for a CW
[Voltage Multipliers]
Alberto
March 27, 2024, 10:54:52 PM
post Re: CM400 Induction Heater
[Electronic Circuits]
markus
March 27, 2024, 11:53:42 AM
post Re: OCD Triggering Early + Low Output
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
March 27, 2024, 05:14:36 AM
post Re: Is the UD2.7C under voltage lock out basically worthless?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
March 27, 2024, 04:47:48 AM
post Re: DRSSTC Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
March 27, 2024, 04:41:59 AM
post Re: DRSSTC Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
alan sailer
March 27, 2024, 12:04:34 AM
post Re: Super flat QCW simulation (does this look reasonable?)
[Dual Resonant Solid State Tesla coils (DRSSTC)]
toooldforthis
March 26, 2024, 11:08:14 PM
post Re: DRSSTC Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Benjamin Lockhart
March 26, 2024, 11:07:20 PM
post Re: Is the UD2.7C under voltage lock out basically worthless?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Benjamin Lockhart
March 26, 2024, 10:46:29 PM
post OCD Triggering Early + Low Output
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Saattvik24
March 26, 2024, 09:03:43 PM
post Re: DRSSTC Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
alan sailer
March 26, 2024, 08:46:59 PM
post Re: DRSSTC Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
March 26, 2024, 05:02:18 PM
post Re: DRSSTC Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
alan sailer
March 26, 2024, 03:16:03 PM
post Re: CM400 Induction Heater
[Electronic Circuits]
Anders Mikkelsen
March 26, 2024, 01:41:49 PM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Benjamin Lockhart
March 26, 2024, 04:48:22 AM
post Re: Re-chargeable 1.5 volt lithium ion AAA batteries
[General Chat]
MRMILSTAR
March 26, 2024, 04:16:37 AM
post Re: DRSSTC Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
March 26, 2024, 04:16:24 AM
post Re: Smoke Screen Machine Protect 950 XP - Teardown of a Smoke Cannon!
[Electronic Circuits]
davekni
March 26, 2024, 04:13:02 AM
post Re: CM400 Induction Heater
[Electronic Circuits]
davekni
March 26, 2024, 04:00:43 AM
post Re: Re-chargeable 1.5 volt lithium ion AAA batteries
[General Chat]
davekni
March 26, 2024, 03:19:18 AM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
thedoc298
March 26, 2024, 01:50:42 AM
post Re: DRSSTC Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
March 25, 2024, 08:05:02 PM
post Re: Smoke Screen Machine Protect 950 XP - Teardown of a Smoke Cannon!
[Electronic Circuits]
Mads Barnkob
March 25, 2024, 07:41:29 PM
post Re: DRSSTC Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
alan sailer
March 25, 2024, 06:45:46 PM
post Re: DRSSTC Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
March 25, 2024, 05:44:25 PM
post Re: CM400 Induction Heater
[Electronic Circuits]
Anders Mikkelsen
March 25, 2024, 04:47:17 PM
post Re: DRSSTC Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
alan sailer
March 25, 2024, 04:27:22 PM
post Re-chargeable 1.5 volt lithium ion AAA batteries
[General Chat]
MRMILSTAR
March 25, 2024, 03:57:34 PM
post Re: CM400 Induction Heater
[Electronic Circuits]
markus
March 25, 2024, 02:06:41 PM
post Re: Odd MOSFET Driver Behavior
[Solid State Tesla Coils (SSTC)]
KrisPringle
March 25, 2024, 04:43:25 AM
post Re: Odd MOSFET Driver Behavior
[Solid State Tesla Coils (SSTC)]
davekni
March 25, 2024, 02:39:40 AM
post Re: Odd MOSFET Driver Behavior
[Solid State Tesla Coils (SSTC)]
KrisPringle
March 25, 2024, 12:47:09 AM
post Re: capacitor and diodes. Voltage values for a CW
[Voltage Multipliers]
Alberto
March 24, 2024, 07:36:32 PM
post Re: My completed 14-stage Cockroft-Walton voltage multiplier
[Voltage Multipliers]
Alberto
March 24, 2024, 07:27:24 PM
post Re: capacitor and diodes. Voltage values for a CW
[Voltage Multipliers]
MRMILSTAR
March 24, 2024, 04:25:23 AM
post Re: capacitor and diodes. Voltage values for a CW
[Voltage Multipliers]
Alberto
March 23, 2024, 10:47:35 PM
post Re: capacitor and diodes. Voltage values for a CW
[Voltage Multipliers]
MRMILSTAR
March 23, 2024, 09:30:21 PM
post Re: capacitor and diodes. Voltage values for a CW
[Voltage Multipliers]
Alberto
March 23, 2024, 04:34:31 PM
post Re: capacitor and diodes. Voltage values for a CW
[Voltage Multipliers]
MRMILSTAR
March 23, 2024, 03:04:25 PM
post Re: capacitor and diodes. Voltage values for a CW
[Voltage Multipliers]
Alberto
March 23, 2024, 01:38:34 PM
post Re: capacitor and diodes. Voltage values for a CW
[Voltage Multipliers]
MRMILSTAR
March 23, 2024, 04:20:03 AM
post Re: Welcome new members, come say hello and tell a little about yourself :)
[General Chat]
davekni
March 23, 2024, 12:54:30 AM
post Re: Smoke Screen Machine Protect 950 XP - Teardown of a Smoke Cannon!
[Electronic Circuits]
davekni
March 23, 2024, 12:05:57 AM
post capacitor and diodes. Voltage values for a CW
[Voltage Multipliers]
Alberto
March 22, 2024, 11:45:03 PM
post Re: Welcome new members, come say hello and tell a little about yourself :)
[General Chat]
OmGigaTron
March 22, 2024, 11:30:09 PM
post Smoke Screen Machine Protect 950 XP - Teardown of a Smoke Cannon!
[Electronic Circuits]
Mads Barnkob
March 22, 2024, 10:20:35 PM
post Re: Where's all this voltage coming from?
[Spark Gap Tesla Coils (SGTC)]
Benbmw
March 22, 2024, 09:21:13 PM
post Re: What actually kills MOSFETs?
[Beginners]
AstRii
March 22, 2024, 03:37:11 PM
post What actually kills MOSFETs?
[Beginners]
FPS
March 22, 2024, 05:09:20 AM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Benjamin Lockhart
March 22, 2024, 03:57:54 AM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
March 22, 2024, 02:59:25 AM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Benjamin Lockhart
March 21, 2024, 06:31:42 PM
post Re: 2x Panasonic Inverter Microwaves - what to salvage, dangers?
[General Chat]
rikkitikkitavi
March 21, 2024, 03:08:01 PM
post Re: [WTS] IGBT, Ferrite, Capacitors, Tools, PSU, Industrial components and parts
[Sell / Buy / Trade]
Mads Barnkob
March 21, 2024, 01:37:32 PM
post Re: Difference between these transformers
[Transformer (Ferrite Core)]
Alberto
March 21, 2024, 11:42:07 AM
post Re: Phase Lead Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
March 21, 2024, 04:09:14 AM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Benjamin Lockhart
March 21, 2024, 02:15:31 AM
post My Homemade Structural Analysis X-Ray Machine
[X-ray]
Luca c.
March 21, 2024, 01:35:40 AM
post Re: Phase Lead Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Saattvik24
March 20, 2024, 10:40:00 PM
post Re: Difference between these transformers
[Transformer (Ferrite Core)]
Mads Barnkob
March 20, 2024, 08:03:41 PM
post Re: 2x Panasonic Inverter Microwaves - what to salvage, dangers?
[General Chat]
Mads Barnkob
March 20, 2024, 07:51:57 PM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
March 20, 2024, 10:39:47 AM
post Re: Phase Lead Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
March 20, 2024, 04:09:59 AM
post Re: 160mm DRSSTC II project | Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Benjamin Lockhart
March 20, 2024, 01:13:23 AM
post Re: Phase Lead Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Keybored
March 20, 2024, 12:45:16 AM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
March 20, 2024, 12:30:30 AM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Benjamin Lockhart
March 19, 2024, 11:12:24 PM
post Re: 160mm DRSSTC II project | Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Late
March 19, 2024, 09:47:49 PM
post Re: 160mm DRSSTC II project | Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Late
March 19, 2024, 09:44:19 PM
post Phase Lead Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Saattvik24
March 19, 2024, 06:52:09 PM
post Re: 160mm DRSSTC II project | Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
March 19, 2024, 05:02:44 PM
post Re: Welcome new members, come say hello and tell a little about yourself :)
[General Chat]
Mads Barnkob
March 19, 2024, 05:01:41 PM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
March 19, 2024, 04:31:02 PM
post Re: 160mm DRSSTC II project | Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
March 19, 2024, 03:59:54 PM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Benjamin Lockhart
March 19, 2024, 06:41:39 AM
post Re: Welcome new members, come say hello and tell a little about yourself :)
[General Chat]
davekni
March 19, 2024, 04:05:49 AM
post Re: Welcome new members, come say hello and tell a little about yourself :)
[General Chat]
OmGigaTron
March 18, 2024, 09:08:35 PM
post Re: Can I Trust This Super Cheap Site?
[General Chat]
2020-Man
March 18, 2024, 09:07:35 PM
post Re: Can I Trust This Super Cheap Site?
[General Chat]
Twospoons
March 18, 2024, 08:57:06 PM
post Re: Can I Trust This Super Cheap Site?
[General Chat]
MRMILSTAR
March 18, 2024, 03:51:33 PM
post Re: 160mm DRSSTC II project | Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Late
March 18, 2024, 02:59:46 PM
post Re: 160mm DRSSTC II project | Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Late
March 18, 2024, 02:33:25 PM
post Can I Trust This Super Cheap Site?
[General Chat]
2020-Man
March 18, 2024, 11:02:12 AM
post Re: Where's all this voltage coming from?
[Spark Gap Tesla Coils (SGTC)]
Twospoons
March 18, 2024, 02:36:11 AM
post Re: Best forum for vacuum tube amplifiers?
[General Chat]
Mads Barnkob
March 17, 2024, 07:42:55 PM
post Re: 2x Panasonic Inverter Microwaves - what to salvage, dangers?
[General Chat]
Michelle_
March 17, 2024, 04:15:14 PM
post Re: 2x Panasonic Inverter Microwaves - what to salvage, dangers?
[General Chat]
Michelle_
March 17, 2024, 05:05:04 AM
post Re: Where's all this voltage coming from?
[Spark Gap Tesla Coils (SGTC)]
davekni
March 17, 2024, 04:50:51 AM
post Re: 2x Panasonic Inverter Microwaves - what to salvage, dangers?
[General Chat]
Twospoons
March 17, 2024, 04:45:17 AM
post 2x Panasonic Inverter Microwaves - what to salvage, dangers?
[General Chat]
Michelle_
March 17, 2024, 04:17:51 AM
post Where's all this voltage coming from?
[Spark Gap Tesla Coils (SGTC)]
Terry
March 17, 2024, 01:29:32 AM
post Re: DRSSTC Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
March 17, 2024, 12:33:06 AM

Sitemap 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 
SimplePortal 2.3.6 © 2008-2014, SimplePortal