Re: Circuit Maker Simulation of Modified "Mazzilli" Driver
Sulaiman, Mon Dec 05 2016, 06:59PM

I've not used a circuit simulator for a long time so not certain but;

. CircuitMaker do not have a circuit simulator in their present suite ... why not ?
. in real life your circuit will not work
. add a switch for the battery and watch the simulated transients
. a simulation is only as good as the model, often 'parasitic'/intrinsic virtual components have to be modelled to get a true simulation

Re: Circuit Maker Simulation of Modified "Mazzilli" Driver
jpsmith123, Mon Dec 05 2016, 07:29PM

Hello Sulaiman, thanks for the reply.

I always take simulation results with a (big) grain of salt. In this case however I also happened to find a blog where someone mentioned this modified circuit...although when I read it again, it's not clear from the wording that it was actually tested.



(BTW: Happy Birthday!)

Re: Circuit Maker Simulation of Modified "Mazzilli" Driver
Antonio, Mon Dec 05 2016, 08:09PM

At least in a simulation, this circuit appears to really work. It is being powered through the 390 ohms resistors and the diodes. The choke can be omitted, as it is not doing anything, and a single capacitor across the primary coil can be used. Don't expect great efficiency.

Re: Circuit Maker Simulation of Modified "Mazzilli" Driver
Sulaiman, Mon Dec 05 2016, 09:30PM

the few zvs that I have played with work best when
gate resistor power is applied - oscillations can be seen on a 'scope, and now in simulation,
then when power to the primary is applied you do not get the dreaded lock up condition.

Re: Circuit Maker Simulation of Modified "Mazzilli" Driver
Blackcurrant, Mon Dec 05 2016, 10:37PM

try using Initial Conditions to force a better start up ie make the caps + & -

Re: Circuit Maker Simulation of Modified "Mazzilli" Driver
jpsmith123, Tue Dec 06 2016, 12:03AM

Every time I try to set an initial condition, I get an error message that the time step is too small.

But I just got another idea. I'm going to try to use a "battery" to supply power to the gates, and a "signal generator" (set to produce a long positive "pulse" with a small initial delay) to supply power to the primary.

Edit: Finally, it seems to be...at least oscillating. The signal generator seems to be a work-around for the start up problem.

Re: Circuit Maker Simulation of Modified "Mazzilli" Driver
Antonio, Tue Dec 06 2016, 12:19AM

Oscillators in simulations have to be started, or they just continue in the DC operating point, calculated by the simulator at the start of the simulation. Add a pulsed voltage source in series with one of the capacitors, producing a brief pulse at the start of the simulation.

Re: Circuit Maker Simulation of Modified "Mazzilli" Driver
jpsmith123, Tue Dec 06 2016, 12:29AM

Here's the circuit:





And here's the output:

Re: Circuit Maker Simulation of Modified "Mazzilli" Driver
Sulaiman, Tue Dec 06 2016, 11:24AM

I'm not sure why your simulation works because looking at the circuit diagram I would not expect it to,

. Rload (100R) would betransformed to about 5 Ohms across the primary
. from the simulation, the resonant frequency is 80 kHz
0.1 uF at 80 kHz has a reactance of about 20 Ohms ... much too large for a 5 Ohm load,
try using Rload = 100 kOhm
and for resonance at 80 kHz, 100 nF requires 40 uH to resonate with ....
all looks odd to me.

For my curiosity, would you run the simulation again
but show the voltage at one of the transistor drain terminals please ?

Re: Circuit Maker Simulation of Modified "Mazzilli" Driver
jpsmith123, Tue Dec 06 2016, 02:59PM

Probe at drain of Q2:





Edit: I forgot to say, now that the amazing fact that it's oscillating in the first place - has worn off - it doesn't look right to me either. Hopefully later today or tomorrow I'll get a chance to try it with another simulator and see what happens.

Re: Circuit Maker Simulation of Modified "Mazzilli" Driver
Sulaiman, Tue Dec 06 2016, 05:51PM

O.K. ... now I'm confused because the drain waceform is what I'd expect,
maybe the 100 nF is resonating with the transformer leakge inductance ?
(in parallel with 2x 100 uH)

Re: Circuit Maker Simulation of Modified "Mazzilli" Driver
jpsmith123, Wed Dec 07 2016, 05:41AM

That's what I was thinking also.

But since CircuitMaker seems generally "messed up" in ways I don't understand, I'm going to force myself to stop wasting time with it and get more familiar with other simulators such as Pspice.

Right now I'm experimenting a little bit with LTspice. Hopefully by tomorrow I will be able to compare its result to that of CircuitMaker.

(Basically what I want to do is to run one of my big ferrite HV transformers with a ZVS driver - preferably powered directly from the 120 volt wall socket. So I'm trying to get a good simulation of the basic Mazzilli circuit as a baseline, and then possibly modify it, if need be.

Re: Circuit Maker Simulation of Modified "Mazzilli" Driver
Sulaiman, Wed Dec 07 2016, 03:30PM

this type of zvs topology has many limitations;
if you want a continuous fixed secondary voltage (e.g. no short-circuits or capacitor charging) ok
what sort of things do you expect to do with the output ?

Re: Circuit Maker Simulation of Modified "Mazzilli" Driver
jpsmith123, Thu Dec 08 2016, 02:27AM

I was seriously considering using a Mazzilli ZVS driver to drive a ferrite transformer (@25 to 30 kHz and 20 to 22 volts/turn) followed by a voltage multiplier - as a 50 kv CCPS.

The simplicity of the circuit is an attractive feature. Also, some people e.g., on youtube, are claiming to have successfully operated them from the 240V mains.

I was thinking that if I can get good simulations, I can experiment with different gate drive modifications to the circuit.

Also, if I try to run a ZVS driver and ferrite transformer from a DC bus voltage of 330 volts or something like that, I may need to gap the core to get a higher Q, right? Simulations might shed light on this too.

OTOH with a half-bridge SLR driver for example I wouldn't have that complication. So maybe I should forget the ZVS driver for this purpose?

Re: Circuit Maker Simulation of Modified "Mazzilli" Driver
hen918, Thu Dec 08 2016, 01:30PM

The problem with high voltage Mazzillis is the much higher current flowing. It causes problems with the gate diodes not switching quick enough, and causing a FET to remain on, and explode. The is also a higher inductance on the primary required, (and I'm talking much higher) and higher voltage FETs, or, better, IGBTs, required (at least 1200 V). At 3.14*340 V (1070 V) isolation becomes important on the primary. High voltage FETs or IGBTs and high currents = high losses.

An interesting Mazzilli equivalent for high voltages is John's Induction Heater circuit:
Even this is temperamental.

There are reasons there aren't many high voltage Mazzillis!

I personally avoid them, I never get even low voltage induction heaters / wireless chargers to work properly with a low coil inductance, although all my flyback drivers have worked fine, even charging electrolytics.

Re: Circuit Maker Simulation of Modified "Mazzilli" Driver
jpsmith123, Thu Dec 08 2016, 02:34PM

I could be wrong, but I don't necessarily see those issues as fundamentally limiting it to low voltage operation, but at some point it may
be more of a hassle than it's worth, IMO.

BTW have you seen this video on youtube?

Re: Circuit Maker Simulation of Modified "Mazzilli" Driver
hen918, Thu Dec 08 2016, 05:05PM


That's not a normal Mazzilli:
But even so, impressive.

Re: Circuit Maker Simulation of Modified "Mazzilli" Driver
jpsmith123, Thu Dec 08 2016, 09:54PM


Well as I see it, it's a Mazzilli driver with a modified gate drive circuit - which may or may not be necessary. (It seems no two "Mazzilli driver" circuits are exactly the same these days, so they seem to be collectively known as generic "ZVS drivers").

Anyway, IMO, the point of going to higher DC supply voltage - for a given power throughput - is to reduce the primary current. Of course this requires more turns on the primary, which will increase the inductance and lower the Q.

At the bottom of that schematic diagram you linked to there's a statement that the Q must be several times > 1 even when under heavy load (arcing). What happens if it's not? (It would be nice to have more detailed information about his circuit, especially the transformer and capacitor).

With the big TSC ferrite core transformer I have ("50all" ferrite material) I get something like 7800 nH/(turn)^2, so for a primary running at a drive level of 20 to 22 volts per turn with a 330 volt DC supply voltage, my primary inductance will be somewhere close to 2 mH. So what I want to know is: How do I get a Q > 1 under load with so much inductance?

This is one of the things I was hoping to explore with simulation, i.e., to see how the circuit behaves under various load conditions vs. Q.

###########################################

E dit: I keep forgetting that the primary voltage on the Mazzilli driver is 3.33 (or something like that) * DC supply voltage, so apparently I would need many more turns than I mentioned above. Anyway, I'm going to forget about it and take Suliaman's hint and just go with a SG3525 based half-bridge SLR circuit, which CircuitMaker seems to simulate properly.

Re: Circuit Maker Simulation of Modified "Mazzilli" Driver
hen918, Fri Dec 09 2016, 02:36PM

I was going to mention that comment at the bottom of the diagram.
the voltage across the LC tank should be Pi * Vin, so 330*3.14 = 1040 V
1040 / 20 = 52 turns
according to some playing around with ExellentIT, the magnetising inductance is going to be about 6mH with an ungapped core. This will be the approximate inductance unloaded.

The capacitance to achieve a frequency of 25kHz is 6.8 nF.
The Q factor is going to be approximately 0.001, depending on the series resistance of your inductor (I have assumed a resistance of 1 ohm.)

When loading increases the Q factor also increases as the effective inductance drops, to become the total leakage inductance of the transformer with a 0 ohm load. This leakage inductance will be in the 10s of uHs, or much greater with a gapped core.

The only issue now is the huge voltage across such a small inductance. MASSIVE currents now flow.
X(L) = 2 * Pi * f * L
2 * 3.14 * 25000 * 0.00001 = 1.57 ohms.
V(RMS) = 1040/sqrt(2) = 735 V
735/1.57 = 470 A

if R(L) = 1 ohm, P(Dissipated) = 470^2 = 220 kW
oops!
This is why the core is gapped. But Q will still be very low, and the circuit probably won't oscillate.

Re: Circuit Maker Simulation of Modified "Mazzilli" Driver
jpsmith123, Fri Dec 09 2016, 06:40PM

In my case I'm using a TSC Intl. double "U" core, part# 102-57-25 (x2), with "50All" ferrite material which has a permeability of 3000 and Al of about 7800 nH/turn^2 or something like that. (Ferroxcube makes an almost identical part, but with their 3C90 material, you get 5500 nH/turn^2).

BTW I found a decent online gapped-core inductance calculator here:

So if I'm not mistaken, if I were to put 52 turns on the primary of my core, I'd have an inductance of about 21 mH, and I estimate the leakage inductance would be in the range of about 500 uH or something like that (assuming a coupling factor of about 0.975).

For a frequency of 25 kHz, C would be 0.002 uF and the Q of the primary circuit would be about 0.0003*R, where R is the load resistance referred to the primary.

So somewhere between a load drawing 100 to 200 watts, the Q will drop below 1.

I think "Microwave89" said that during arcing he was drawing 3kw or something like that. So in my case that would be about 179 ohms shunted across the primary inductance of 21 mh and the Q would be about 0.05.

Maybe I'm looking at everything all wrong, but it seems it would stop oscillating before getting to this point.

Re: Circuit Maker Simulation of Modified "Mazzilli" Driver
hen918, Sat Dec 10 2016, 10:25AM

Ahhh, oops, forgot to use 1040 V when messing around with ExcellentIT.
21mH looks more like it.

BTW, your link needs a closing bracket removing from the end of it.

Re: Circuit Maker Simulation of Modified "Mazzilli" Driver
Enceladus, Thu Feb 09 2017, 07:00AM

The only circuit simulator I could ever make sense of is EveryCircuit for Android. I'm really surprised it doesn't get more mention on this site.