New Bipolar Boost TX and Front End

[KingJL]

It is 6mm with room for 0.5mm spacer if required

[ATTACH]48610[/ATTACH]

[ATTACH]48611[/ATTACH]

With the ZW-41303-TC, it should fit. core height 3.15 mm + winding (0.645 mm* 2) * EL7202 height 1.625 mm = 6.065 mm

[WM6]

Maybe some manufactures use color coding?

Some yes, in regard to ferrite core frequency range:






But not sure if all producer use color mark as standard data on their cores.

[Altra]

Hi WM6

It looks like iron powder cores use a color code. We are using "soft ferrite" cores which are a mix of various metals. Probably each manufacture has it's own proprietary mix with similar characteristics to the other makers. But no colors. Still learning, I've always bought pre-made inductors and transformers for the application and not had to worry about core material.

This explains a little

https://www.nutsvolts.com/questions-...nganese%20zinc.

[KingJL]

... When my order for AWG 28 arrives, I will wind the secondaries with 18 turns...

The AWG 28 arrived. Wound the secondaries with 18 turns (primaries are 4 3/4 turns) and checked the secondary: primary inductance. The results are 997uH:67uH, 911uH:64uH, 1020uH:73uH, 1008uH:69uH.


Temporarily mounted the toroid transformer on the PCB to check the fit. We need to add insulation between the windings of the primary and the 2 resistors and 2 capacitors in the primary circuit on which the primary is resting.


I am satisfied with the transformer parameters and the PCB fit.

[Mdtoday]

The AWG 28 arrived. Wound the secondaries with 18 turns (primaries are 4 3/4 turns) and checked the secondary: primary inductance. The results are 997uH:67uH, 911uH:64uH, 1020uH:73uH, 1008uH:69uH.
[ATTACH=CONFIG]48638[/ATTACH]

Temporarily mounted the toroid transformer on the PCB to check the fit. We need to add insulation between the windings of the primary and the 2 resistors and 2 capacitors in the primary circuit on which the primary is resting.
I am satisfied with the transformer parameters and the PCB fit.

Excellent news and looking good. I used Kapton tape under the original mounting of the toroids
Should see my order of cores this week and I’ll then wind and test and post results

[dbanner]

Having the drivers within the toroid field is rather interesting. Keep up the good work guys! Wish you success.

[KingJL]

Excellent news and looking good. I used Kapton tape under the original mounting of the toroids
Should see my order of cores this week and I?ll then wind and test and post results

I have populated the power distribution and MOSFET driver circuits. I had to wait for a re-order of BAT54S's as when I went to mount them I could not find them. Will power up later this week and check driver signals without any other circuit interaction. I suspect (as I have no idea of the transformer coupling coefficient, which with toroids should be very close to 1.0) that the toriods will work well with turns ratios ranging from 3.3:1 to 4:1. Below 3.3:1 the "off" condition voltage raises to a level (~1V) dangerously (for my satisfaction) close to the lower end of the threshold voltage range of the MOSFET. Due to the way that this driver circuit works, it is better to slightly overdrive the circuit as during the turn-off drive, it provides sufficient drive across the zener diode to ensure a 0V or slightly negative residual during the "off" condition, while the zener provides over voltage protection during the "on" condition.

[Mdtoday]

I have populated the power distribution and MOSFET driver circuits. I had to wait for a re-order of BAT54S's as when I went to mount them I could not find them. Will power up later this week and check driver signals without any other circuit interaction. I suspect (as I have no idea of the transformer coupling coefficient, which with toroids should be very close to 1.0) that the toriods will work well with turns ratios ranging from 3.3:1 to 4:1. Below 3.3:1 the "off" condition voltage raises to a level (~1V) dangerously (for my satisfaction) close to the lower end of the threshold voltage range of the MOSFET. Due to the way that this driver circuit works, it is better to slightly overdrive the circuit as during the turn-off drive, it provides sufficient drive across the zener diode to ensure a 0V or slightly negative residual during the "off" condition, while the zener provides over voltage protection during the "on" condition.

It will interesting to see the results.
I might load another board or two with all the passives and smaller diodes etc then load the remaining semis if/when required for further testing.

[KingJL]

Will power up later this week and check driver signals without any other circuit interaction...

Decided to hold off on mounting the toroids... I only want to do this once. I have ordered some Kapton tape ( thanks @Mdtoday for that suggestion) to insulate the winding from the components over which the toroids are mounted. The tape should arrive mid next week. Also things will slow down after next Tuesday for probably about 2 weeks as I go in for cataract surgery Tuesday, Dec 17.

Forgive me, but I must stress that from this point forward in testing M1,M3,M6,M7 MOSFET drivers, TX coil signals, all signals in the path from the coil thru damp switch(M6 & M7), damp resistance, U4, U5 and the pre-amp (U9) inputs are truly differential with a floating reference... meaning that any signal in these paths is valid only with reference to the opposite side of the signal ( i.e. NOT GND ). The only safe way to view these signals, with meaningful results, is with an oscilloscope with a delta function (chanA - ChanB) capability between two input channels. Any attempt to use a probe's ground clip to connect to the opposite signal reference can result in disaster as some oscilloscopes have the outer BNC conductor of the probe jack connected to a common ground. All points in this path have at least 5V sourced alternately (between TX cycles).

[Mdtoday]

Decided to hold off on mounting the toroids... I only want to do this once. I have ordered some Kapton tape ( thanks @Mdtoday for that suggestion) to insulate the winding from the components over which the toroids are mounted. The tape should arrive mid next week. Also things will slow down after next Tuesday for probably about 2 weeks as I go in for cataract surgery Tuesday, Dec 17.

Yes, good idea, when the cores arrive, I will wind, mount them on the carrier boards and probably leave this set up as a test board for the bench, then build up another for the field test.

All the best for your surgery JL

[Mdtoday]

Forgive me, but I must stress that from this point forward in testing M1,M3,M6,M7 MOSFET drivers, TX coil signals, all signals in the path from the coil thru damp switch(M6 & M7), damp resistance, U4, U5 and the pre-amp (U9) inputs are truly differential with a floating reference... meaning that any signal in these paths is valid only with reference to the opposite side of the signal ( i.e. NOT GND ). The only safe way to view these signals, with meaningful results, is with an oscilloscope with a delta function (chanA - ChanB) capability between two input channels. Any attempt to use a probe's ground clip to connect to the opposite signal reference can result in disaster as some oscilloscopes have the outer BNC conductor of the probe jack connected to a common ground. All points in this path have at least 5V sourced alternately (between TX cycles).

Very good advice, I have witnessed some quite funny things with young engineers using laptops with USB programming connections to high voltage control products containing differential ADCs and oscilloscope measurements with real ground connected probes...

[KingJL]

More improvements for TxRXx version 2

@Mdtoday and others that may be interested. I have made some improvements that will be incorporated into version 2 of the TXRX board. The improvements accomplish the following. (1) A more desireable and flatter constant current waveform, (2) a much faster (about 2x) current transition from full on to 0, (3) complete redesign of the MOSFET driver using an ADuM4120. This eliminates the toroid pulse transformers and reduces the parts count per MOSFET driver from 12 down to 4. (4) Reduced propagation delays for the MOSFET drive.

The HV boost section has slightly added complexity by eliminating MOSFET body diode charge path for the boost storage capacitors. A diode is required between the coil and the boost MOSFET(s) to isolate the capacitance in the MOSFET drive from the coil. Additional steering diodes are needed to suppl the flyback voltage to the boost capacitor. Also the flyback voltage is "stacked' onto 15V, thereby overcoming the usual loss of boost, allowing boost up to 1 amp in less than 5 usec. The two HV boost capacitors are reduced to 0.022uF which is readily available in higher voltage ratings and smaller footprint (200V vs 100V for the 0.22 and are available in 1206 package).

The signaling for the MOSFET(s) is more straightforward (and more like everyone is used to seeing)... no more start and stop signals for each function. The pin count needed for interfacing with the logic board is reduced by 4.

The simulation files are in improved Bipolar.zip

There are two versions of the simulation schematic:
TX(ADuM)_RX(THAT).asc : new TX with THAT RX
TX(ADuM)_RX(dual JFET).asc : new TX with dyul OPA828 JFET(s)
the ADuM.asc is not a separate simulation schematic, but is a subsheet used by both simulations

I believe I have included all of the needed symbols and subcircuits, but let me know if any turn up missing.

These improvements will not be incorporated into the PCB set until we are done with our testing of the current hardware. Also we will probably move to a 20 bit ADC in version 2.

[Mdtoday]

@Mdtoday and others that may be interested. I have made some improvements that will be incorporated into version 2 of the TXRX board. The improvements accomplish the following. (1) A more desireable and flatter constant current waveform, (2) a much faster (about 2x) current transition from full on to 0, (3) complete redesign of the MOSFET driver using an ADuM4120. This eliminates the toroid pulse transformers and reduces the parts count per MOSFET driver from 12 down to 4. (4) Reduced propagation delays for the MOSFET drive.

The HV boost section has slightly added complexity by eliminating MOSFET body diode charge path for the boost storage capacitors. A diode is required between the coil and the boost MOSFET(s) to isolate the capacitance in the MOSFET drive from the coil. Additional steering diodes are needed to suppl the flyback voltage to the boost capacitor. Also the flyback voltage is "stacked' onto 15V, thereby overcoming the usual loss of boost, allowing boost up to 1 amp in less than 5 usec. The two HV boost capacitors are reduced to 0.022uF which is readily available in higher voltage ratings and smaller footprint (200V vs 100V for the 0.22 and are available in 1206 package).

The signaling for the MOSFET(s) is more straightforward (and more like everyone is used to seeing)... no more start and stop signals for each function. The pin count needed for interfacing with the logic board is reduced by 4.

The simulation files are in [ATTACH=CONFIG]48705[/ATTACH]

There are two versions of the simulation schematic:
TX(ADuM)_RX(THAT).asc : new TX with THAT RX
TX(ADuM)_RX(dual JFET).asc : new TX with dyul OPA828 JFET(s)
the ADuM.asc is not a separate simulation schematic, but is a subsheet used by both simulations

I believe I have included all of the needed symbols and subcircuits, but let me know if any turn up missing.

These improvements will not be incorporated into the PCB set until we are done with our testing of the current hardware. Also we will probably move to a 20 bit ADC in version 2.

Excellent, thanks for sharing JL, I will study the simulation and familiarise myself with the ADuM4120. Nice work!

[eclipse]

KingJL I would like to thank you for the changes and the circuit with ADuM4120 & THAT1512.

mcemos.lib & 74HC.lib are missing (I've added those but the sim shouts Time step too small schmitt instance TX(ADuM)_RX(THAT))

[KingJL]

KingJL I would like to thank you for the changes and the circuit with ADuM4120 & THAT1512.

mcemos.lib & 74HC.lib are missing (I've added those but the sim shouts Time step too small schmitt instance TX(ADuM)_RX(THAT))

Will reply in more detail in about 5 hrs... a little busy right now. There are somes things to check that may help.