New Bipolar Boost TX and Front End

[Mdtoday]

Things are looking much better... it looks like Boost_B_G is 9-10 V drive and Boost_A_G is ~11V drive. But it also looks like the total yellow trace is about 85% of the blue trace overall, like there is a missmatch of the channel inputs. If that is the case, then they both might be meeting the minimum 10V drive (actually 9V will work well enough to progress on with testing and we can improve that with new inductors when we get them ready). But I think the drive is now high enough to see what we get for TX.

In fact I have just updated the firmware of the DSO and did a calibration, the mismatch has just presented itself...so I will investigate that as it is on channel 4 too and yet channel 1 and 3 are near identical..

This is what I get on channel one for both gate drives, So yes both the same

[KingJL]

@Mdtoday, do you have probe points for M6_G and M7_G?

[KingJL]

This is what we have. Yellow trace is Boost_B_G measured at gate of M1, Blue trace is Boost_A_G measured at gate of M3 to Gnd.

[ATTACH]48490[/ATTACH]

I can't find my differential probes at the moment, when I do, I will connect coil take some measurements

Things are looking much better (looks like 100% improvement over previous boost signal waveforms)... it looks like Boost_B_G is 9-10 V drive and Boost_A_G is ~11V drive. But it also looks like the total yellow trace is about 85% of the blue trace overall, like there is a missmatch of the channel inputs. If that is the case, then they both might be meeting the minimum 10V drive (actually 9V will work well enough to progress on with testing and we can improve that with new inductors when we get them ready). But I think the drive is now high enough to see what we get for TX.

[Mdtoday]

This is approximately what we are shooting for measured at either Boost_A_G to gnd or Boost_B_G to gnd. We are looking for a minimum peak of 15V... preferably 20V (gives a 10v -15V signal between gate and source).

This is what we have. Yellow trace is Boost_B_G measured at gate of M1, Blue trace is Boost_A_G measured at gate of M3 to Gnd.



I can't find my differential probes at the moment, when I do, I will connect coil take some measurements

[KingJL]

Ok, I'll swap them out then and test, thanks.

This is approximately what we are shooting for measured at either Boost_A_G to gnd or Boost_B_G to gnd. We are looking for a minimum peak of 15V... preferably 20V (gives a 10v -15V signal between gate and source).

[Mdtoday]

@JL, Here is the Windows 64 bit driver used for Prolific based USB to TTL serial converters.

Profilic_Win8_x64_x86.zip

[Mdtoday]

I think the ones we have are too small to try and get the total windings needed. A little larger will also make mounting in the currently spaced mounting holes easier also. When we get them as we need them, I think we need some sort of potting (a gel or flexible type... not solid) to support them. You wouldn't believe it but they will fail from micro vibrations caused by their use that will work harden the copper and will lead micro breaks causing increased resitance in the windings. There are some flexible conformal coatings out there.

I agree, they are a bit of a squeeze for mounting. Latex may work well or non acetic flow-able silicone, like you say, there are a number of flexible potting compounds available.

[Mdtoday]

As near as I can tell, even though some suppliers list type 75/J, the type 75 only has a ui of ~3000 ( I think I have seen 1 spec that listed it at 3500)... a little short of 5000!

Ok,will be mindful of double checking the specs before proceding

[Mdtoday]

I have done some checking and it is safe to make R22, R23, R28, R29, R32, R33, R37, and R38 zero ohm jumpers instead of 1 ohm resistors. That should also help bring up the voltage a little.

Ok, I'll swap them out then and test, thanks.

[KingJL]

I will rewind the transformers tomorrow and measure the gate voltages again but I do see an improvement with just reducing the windings back to 4.

I have done some checking and it is safe to make R22, R23, R28, R29, R32, R33, R37, and R38 zero ohm jumpers instead of 1 ohm resistors. That should also help bring up the voltage a little.

[KingJL]

I think the type J (also known as type 75) core material (ui of 5000) ...

As near as I can tell, even though some suppliers list type 75/J, the type 75 only has a ui of ~3000 ( I think I have seen 1 spec that listed it at 3500)... a little short of 5000!

[KingJL]

Excellent, I will see what I can find over here...

I think the type J (also known as type 75) core material (ui of 5000) with the size about the same as the ones identified will work fine.

I might also solder in some good quality pcb sockets into the transformer pads. That will make things a little better for testing.

That is a superb idea!

[KingJL]

... Rewinding the ones we have or winding from scratch will take about the same time ...

I think the ones we have are too small to try and get the total windings needed. A little larger will also make mounting in the currently spaced mounting holes easier also. When we get them as we need them, I think we need some sort of potting (a gel or flexible type... not solid) to support them. You wouldn't believe it but they will fail from micro vibrations caused by their use that will work harden the copper and will lead micro breaks causing increased resitance in the windings. There are some flexible conformal coatings out there.

[Mdtoday]

I think I have a good candidate. I am placing an order and when I get back from my Thanksgiving day holiday trip, I will wind and test.

Another (probably a better fit as it has a higher ui due to larger cross sectional diameter) id here. In fact just placed an order. I will wind and test. With this last one 5 turns of 22 awg results in between 70uH and 92 uH (range of accuracy of permeability factor). For the secondary I will use 18-20 turns 28 - 32 awg.

Excellent, I will see what I can find over here.
I might also solder in some good quality pcb sockets into the transformer pads. That will make things a little better for testing.

[Mdtoday]

Great! The waveform across COIL_ & COIL+ is just about what I would expect. Now the gate drive for M3 (Boost_A_G) to ground will be riding on top of (in reference to) TX_COIL- to gnd and the gate drive for M1 (Boost_B_G) will be riding on top of (in reference to) TX_COIL+. In the mean time I am doing to see what info I can find on Amidn's site to research some aspect of toroid cores available for our purpose, just in case we have to wind our own. If we have to go that route, I would like a core just a little larger OD (~20 - 24 mm) & ID (~11 - 13 mm) and a ui such that 5 turns would yield between ~70 and 90 uH primary with a 3.5: - 4:1 turns ratio.

Looking good... Yes the gate drive in reference to TX+ and TX- is as you describe, I will setup and take some more detailed measurements and take notes. At least we are in the ball park now.

Ok on toroids, it is a great plan I think. Rewinding the ones we have or winding from scratch will take about the same time with better results, so is a good move for sure.