Thank you Spokane1 !

May I ask why why do my messages not appear? You replied to me but my original message is not on the thread and my status says that I have zero posts. Thanks!

Dear Smann,

That is odd. Your post showed up quite normally on my machine. Then again I've been given some moderator control buttons to use (which haven't been needed). I shall ask Chet K. he seems to know a lot about these things.

Spokane1

Thank you Spokane1 !

May I ask why why do my messages not appear? You replied to me but my original message is not on the thread and my status says that I have zero posts. Thanks!

Smann,

Your posts appear to be normal for me also.  Your post asking about GG seems to be normal to me.  And your posts after that also.  According to what I see you now have 6 posts total.

Carroll

Gentlemen,

Here is my take on the operation of the Synchronous Diode.

Comments Welcomed!

Spokane1

Dear All.

Here is my take on the Primary circuit timing sequence.

Spokane1

Dear All,

This weekends work showed a little promise. I was able to get the junk box mockup circuit to lock into the proper timing sequence to display the discontinuous sine wave. I just have the primary circuit operational. This evening I shall add the synchronous diode circuit and start to get a look at the backend operation. For what its worth this circuit shows:

1. This circuit will function at 12 VDC (using the single switch approach)

2. Operation can take place as low as 3.2 kHz

3. A classical laminated iron core  will support the novel oscillation pattern.

None of this means that we are in the OU window of operation, but it is nice to see some hardware implementation of the circuit under discussion. Using the component parameters I have in the actual circuit the simulation shows that I might be able to harvest up 6.5 Watts at a COP of .863. I'm sure the real world performance will be far less than this.

The advantage of the 12 V approach is that all the excitation energy comes from one source. All the gate losses, skew losses, and magnetic probe  interference issues can be evaluated. If this circuit can perform as a self runner then this is the direction to go.

The simulation also shows that the circuit performance improves if I were to use a smaller charging inductance choke. The junk box device (from a salvaged X-Ray transformer) has a 1 KHz inductance of 11.5 mH. The simulation shows that I need a 2 mH unit there. Grahams circuit apparently used a .0324 mH custom device.

If any one is interested in a schematic for this temporary evaluation circuit let me know. I'm sure there will be several variations employed as the circuit technique improves.

Spokane1

Looks nice Spokane1! Love the LeCroy.

Are you using readings from that green current transformer in your calculations? Have you corrected for any phase shift in the current transformer readings?

Dear TK,

"Oh Great Master of Measurement bestow upon this humble and unworthy novice the secrets of professional analysis. Show me the path to accurate and meaningful evaluation of the True and Pure knowledge of Performance. I have only my hands and a few crude tools to sacrifice to this higher cause."

I haven't used any of the observations for calculations nor have I corrected for any phase shift since I don't know how to do that. I was busy just attempting to get the circuit to run. The photos are from last Sunday evening and are of the primary circuit only. Now I have the secondary circuit operational and can actually harvest a little on the back end. After making adjustments and changing gate resistors I was able to collect a whooping 1.75 V across the output capacitor using a Harbor Freight DVM.

The next step is to add some additional wide band current transformers on the secondary in two places to see what might be going on there and how the harvest circuit works.

I did notice that once I started to harvest secondary energy that my tank voltage became lopsided with the initial negative swing being larger than the following positive swing. (No photos since I left my cell phone at work). Also the current trace is not very close to what Graham had, then again I'm glad that this circuit functions at all.

I just purchased a new Import LCR meter and the instruction book is all in Japanese or something, so I can't follow the calibration procedure. So, I'm not sure my static inductance measurements of the transformer are correct or not. Also I need to do some DC resistance measurements of the transformer since there is significant losses there, much more than what Graham had with his huge Litz wire windings.

Anyway this is a place to start.

Spokane1

Also... the mosfets. The IRFPG50 is slow and has a high resistance of 2 ohms when fully on. I've done a lot of work with that particular mosfet... heh heh... and I don't think I'd want to use it in a high-frequency H-bridge or an energy harvesting circuit.

Dear TK,

I figured as much for those MOSFETS, But the price is right when you have them on hand. These will probably be the first things to go as I get this circuit going as good as it is going to get using an iron core. At 3 kHz their slowness is most likely not going to impact a basic understanding of what is going on. Right now I believe that we have at least three proposed approaches for a harvesting protocol. This circuit might determine which is best.

As far as measurements go, can't we just measure the usable energy in and the usable energy out and dispense with Kelvin probes (which I probably can't afford). I have placed a current sensing resistor at the battery. Is there some method that you would recommend where I could see how much power is coming from the battery and compare that to how much power is being consumed by the load?  To me what happens in-between is not all the relevant to our goal. (except for engineering judgments) Both ends are fitted with large smoothing capacitors.  An accuracy within 5% would be good enough for me. If this system can't produce a COP of at least 5.0 then it is probably not going to have much commercial value anyway.

Dealing with AF and DC mixed for measurement purposes with $5 DVM's is not my forte, but it is probably what most researchers have to work with.

Spokane1

Well.... hmmm.

Now I'm confused. In previous posts you've said that the harvest pulse is turning the mosfets _off_ for a very brief time (see the diagram attached below) but now your mosfet Gate trace (CH4) looks like it's going HIGH and turning the mosfets _on_ for a very brief time and leaving them off for the remainder of the cycle.

So is the substantial current you are reading here, actually going through the mosfet body diode? What am I missing here?

What is that 50R, 10W load resistor? Is it a wirewound resistor?

Yes, I'll bet that ringing you are seeing is a "real artifact" in the sense that it is really happening but is something you don't want happening and may be caused by stray inductances due to wiring length or maybe the inductance of that load resistor.