Class-E Totem-Pole Drive Documentation

[ke1gf]

Here guys I slapped together page or two about my TP driver.
http://users.wpi.edu/~smithw/Official_TP_Driver/index.html


Best, of wishes
-Bill 'GF

[frank carcia]

Good Job Bill!

Analog devices sells a DDS evaluation module that may be easier to
use but I bet will cost a couple hundred bucks. Remember the Class E
party when Pete WA1SOV demonstrated his exciter that used that module.
Pete used a thumb wheel switch as the interface if I remember.

[Phil G4ZOW]

Bill,

Freddo in the Netherlands is 'da man' for inexpensive design PLL's:

http://www.freddospage.nl/

Not exactly what you're after but he invented the word 'inexpensive' AND his designs work.

Check out his AM broadcast band designs.

Phil G4ZOW

[ke1gf]

Cool Site Phil, thanks for the link!

-Bill 'GF

[frank carcia]

Bill,
I was looking at your DDS thing and noticed your regulator. We found stringing regulators like that can casue latch up in LSI parts. Usually the core voltage is lower and the external drivers use the higher voltages.
We found the part will latch up if the drivers come up before the core. This is a common FPGA power problem. There are parts out there that control the regulator power up sequence so you don't get into a latch up condition. Your configuration makes sense for saving power but it is better to hang them in parallel off the unregulated supply. So if you get weird latch ups that is where to look.

[ke1gf]

Okay frank, I'm going to order the parts to build it up probably this week, my MQP advisor wants work done do maybe I'll have afew hours to mod the board in the following weeks.

I'll keep you guys updated

[frank carcia]

Bill,
I just wanted to point out a possible problem. We learned the hard way
when a clown didn't read the data sheet. Then I had to spend many a late
night having system problems during temperature qualification tests.
At least the clown is gone and only screwed up one more design after that.
Oh, I forgot he is now a contractor in the other building making more money.

[frank carcia]

Bill,
how warm do your 4420 drivers run? I just tor the 160 meter rig down
and plan to do an update. Might be time to get the second final on line.
fc

[ke1gf]

They run cool frank, I've basically got them surface mounted to a piece of copper clad board, even know they're the pdip package.

I did some signal tracing trying to figure out why the driver wouldn't do 40, the chips just don't have enough umph to do it.

Plus the lenghts between the fets and the drivers is too much even know they're less than an inch away... I need to get the driver chips within 1/3 of an inch of the gates. It's just a mounting nightmare, these TO-247 packages just aren't designed to do this.

I'm stumped right at the moment with going to 40... back to the drawing board.

I read in some IXYS engineering notes that it's not a good Idea to piggy back driver chips, they'll be missmatching in the timing and shoot-through current will most likely occur.

I'm looking at the current moment finding a pair of maybe CB SSB matched NPN/PNP bipolars for an emitter follower/ half bridge

Anyway I'd say it was a sucessful first attempt!

There's stuff out there to do it correctly, it's just way to expensive right now.

Regards,
-Bill 'GF

[ke1gf]

Ooops sorry frank, I'll measure them my my temp probe, my fingers aren't too reliable anymore, to much soldering without a third hand...
Once I get back from school I'll measure them for you.

BTW, I'm probably going to order that PECL osc tonight along with the parts, get out the dremel tool sometime in the following weeks and cut out some traces in the spare clad on the DDS board.

All The BEST!

[frank carcia]

Hi Bill,
When the tree fell I was transmitting and
I fried the transformer secondary wire in the 160 meter rig so decided to
rip it down and update the pre driver. It has a pair of TO3 n and p channel
fets. (built back in '96) Also want to bring the second final on line to double the power.
My antenna is still stuck in the end tree so a good time to do some building.
My dip parts are in sockets and get warm on 75M. There are 2 chips/4 drivers resistor or-ed with 10 ohm resistors per phase.

[ke1gf]

Sorry to hear about your antenna, I hope you get it back up soon.

Your 160 deck is a class S rig right, Double-Pole switching a series resonant network, maybe a parallel network on the output to further reduce harmonics?

I thought my antenna was up there pretty good until the rope snaped right off at the counterweight a few months ago; when we had lots of wind and rain. Ive taken steps to try to get it back up with ease if it happens again, I now have a rope that goes completely from one side of the tree to the other so that the pully can be pulled back down to the ground and another rope placed through it...

I have a pretty good idea about how you're driving, but I don't fully understand.

I have alot of hamradio things that I want to do, but I must get going on school work. Graduation is comming up soon in the fall (for me) and projects are comming due. I probably have time in the term to play I just haven't gotten settled yet, it's only the first week of classes so things are a bit shaken up in my schedule. Looks like I'll have a few hours to play with this weekend so I might do some tinkering.

CUL OM.
-Bill 'GF

[frank carcia]

Hi Bill,
The driver is class S square wave drive but the final is class E.
The final is class E by total accident though. It just ended up that way.
The output is series tuned.
My drive is off a HP VHF generator through a divide by 10 prescaler into a
74AC74 to create 2 phases. That drives the 4 dip totem drivers. Next a pair TO220 totem poles then the pair of TO3 totem poles. That drives the push pull class S driver and on to the final.
I'm looking to add one more push pull stage ahead of the driver to be able to handle the load of the second driver. This would allow the second final to come on line.
The TO3 pre driver couldn't handle both drivers to maintain a 15 ns rise and fall time. I suppose I could back away from hard gate switching
now that we are all smarter. Still it looks cool on the scope.
I started this rig 10 years ago so some parts are obsolete by today's
thinking. I figured it was time to upgrade.
I will need a good wind storm to pull the insulator back on the antenna side so I can lower the whole thing for repair. I just have some ropes providing tension for that day.
I was just curious to know how hot your dips ran, no big deal.
Good luck with school! fc

[KM5TZ/6]

Bill, Frank,

I have my driver working quite well on 40m now (90+% efficient)

I'm using 3 x MAX4420's in parallel per 11N40. I have 2 x 11N40's in parallel (6 MAX4420's altogether). This arrangement works to at least 8MHz but starts to exceed the power dissipation rating of the 4420's above this. There is a small ammount of timing skew on 40m which I compensate for with a RC circuit in the drive circuitry. The gate drive waveform looks very nice. Be sure to use the Maxim 4420's. I made sure to use 4420's with the same date code, the timing consitency appears excellent.

I'll post some pics soon.

David
KM5TZ

[Tom WA3KLR]

Hi Dave,

I learned of the Maxim 4420 family but then for what was readily available at the time, the Microchip TC4420 family appeared to be another source. I don’t know who is the second source of who on these parts. I ordered some Microchip TC4429CPA’s from Digi-Key and played with one driving an IRF-740A. I wasn’t too impressed and it appeared to me that the driver i.c. did not meet spec. Hopefully the Maxim parts are better.

I have since ordered (2) DEIC420 directly from IXYS, $35. each, this past April. They are a bonified CMOS driver i.c. for class E FETs. The data sheet shows driving 4000 pf. at 45 MHz. Check out their data sheet.

I haven’t been back on the class E hobby project to evaluate them yet.