Super low power isolated MOSFET driver

P

Piotr Wyderski

Guest
Hi,

I need to slowly drive a high-voltage high-side MOSFET in a 5kV isolated
setup. This use case reminds an electronic fuse: the MOSFET is expected
to be almost always ON, but the driver needs to start in an OFF
condition. Generally the answer would be Si8261, but it
requires ~50mW. So I have devised a much less energy hungry driver based
on a tiny 1:1 bipolar drive pulse transformer and a 555 (the CMOS
variant, but I don't have a model for it). It looks fine, switching a
180nC MOSFET in under 2us; it should be possible to be tweaked to
consume a milliwatt or two as well. The sim is attached below. My
concern is with the initial conditions: is this setup guaranteed to
reset the timer at power-on
provided the transformer is not energized?

Comments warmly welcomed.

Best regards, Piotr

Version 4
SHEET 1 2408 772
WIRE 464 -928 64 -928
WIRE 176 -832 128 -832
WIRE 304 -832 256 -832
WIRE 544 -832 384 -832
WIRE 128 -704 128 -832
WIRE 176 -704 128 -704
WIRE 544 -704 544 -832
WIRE 544 -704 400 -704
WIRE 128 -688 128 -704
WIRE 64 -640 64 -928
WIRE 176 -640 64 -640
WIRE 1120 -592 880 -592
WIRE 176 -576 -16 -576
WIRE 464 -576 464 -928
WIRE 464 -576 400 -576
WIRE 880 -560 880 -592
WIRE 176 -512 128 -512
WIRE 432 -512 400 -512
WIRE 432 -496 432 -512
WIRE 880 -432 880 -480
WIRE 1120 -432 1120 -592
WIRE 432 -416 432 -432
WIRE -16 -352 -16 -576
WIRE 656 -352 -16 -352
WIRE 832 -352 736 -352
WIRE 880 -320 880 -336
WIRE 1120 -320 1120 -352
WIRE 128 -272 128 -512
WIRE 544 -272 544 -704
WIRE 544 -272 128 -272
WIRE 544 -192 544 -272
WIRE 64 -96 64 -640
WIRE 352 -96 64 -96
WIRE 544 -96 544 -112
WIRE 544 -96 432 -96
WIRE 544 -64 544 -96
WIRE 240 48 144 48
WIRE 352 48 304 48
WIRE 544 48 544 16
WIRE 144 80 144 48
WIRE 352 112 352 48
WIRE 144 192 144 160
WIRE 144 288 144 272
WIRE 352 288 352 192
FLAG 144 288 0
FLAG 352 288 0
FLAG 880 -320 0
FLAG 1120 -320 0
FLAG 128 -688 0
FLAG 432 -416 0
FLAG 544 48 0
SYMBOL voltage 144 64 R0
WINDOW 3 -973 45 Left 2
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value PULSE(0 {Vkey} 100u {Tkey_rise} {Tkey_fall} {Tkey_on}
{Tkey_period})
SYMBOL cap 304 32 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C2
SYMATTR Value 10Âľ
SYMBOL ind2 336 96 R0
WINDOW 3 -12 60 Right 2
SYMATTR InstName L1
SYMATTR Value 400Âľ
SYMATTR Type ind
SYMBOL ind2 448 -80 M270
WINDOW 0 32 56 VTop 2
WINDOW 3 4 56 VBottom 2
SYMATTR InstName L2
SYMATTR Value 400Âľ
SYMATTR Type ind
SYMBOL res 752 -368 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R3
SYMATTR Value 50
SYMBOL nmos 832 -432 R0
SYMATTR InstName M1
SYMATTR Value IXTH88N30P
SYMBOL res 864 -576 R0
SYMATTR InstName R4
SYMATTR Value 300
SYMBOL voltage 1120 -448 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V3
SYMATTR Value 300
SYMBOL Misc\\NE555 288 -608 R0
SYMATTR InstName U1
SYMBOL voltage 272 -832 R90
WINDOW 0 -32 56 VBottom 2
WINDOW 3 -84 34 VTop 2
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V4
SYMATTR Value PWL(0 0 100u 9.6)
SYMBOL res 400 -848 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R2
SYMATTR Value 1m
SYMBOL cap 416 -496 R0
SYMATTR InstName C1
SYMATTR Value 1n
SYMBOL res 528 -80 R0
SYMATTR InstName R1
SYMATTR Value 20k
SYMBOL res 528 -208 R0
SYMATTR InstName R6
SYMATTR Value 20k
SYMBOL voltage 144 176 R0
WINDOW 3 -973 45 Left 2
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V2
SYMATTR Value PULSE(0 {-Vkey} 550u {Tkey_rise} {Tkey_fall} {Tkey_on}
{Tkey_period})
TEXT 110 312 Left 2 !.tran 1m
TEXT 328 -8 Left 2 !K L1 L2 0.98
TEXT 32 424 Left 2 !.param Vkey=2.7
TEXT 32 456 Left 2 !.param Tkey_rise=10n Tkey_fall=10n Tkey_on=1u
Tkey_period=100u
 
On Sun, 19 Jan 2020 18:41:20 +0100, Piotr Wyderski
<peter.pan@neverland.mil> wrote:

Hi,

I need to slowly drive a high-voltage high-side MOSFET in a 5kV isolated
setup. This use case reminds an electronic fuse: the MOSFET is expected
to be almost always ON, but the driver needs to start in an OFF
condition. Generally the answer would be Si8261, but it
requires ~50mW. So I have devised a much less energy hungry driver based
on a tiny 1:1 bipolar drive pulse transformer and a 555 (the CMOS
variant, but I don't have a model for it). It looks fine, switching a
180nC MOSFET in under 2us; it should be possible to be tweaked to
consume a milliwatt or two as well. The sim is attached below. My
concern is with the initial conditions: is this setup guaranteed to
reset the timer at power-on
provided the transformer is not energized?

Comments warmly welcomed.
Click to expand...

Is PWL a floating power supply, on the high side? Is that available?
Everything is grounded in your sim.

I'd consider going optical, a PV supply and a dual (or maybe single)
optoisolator. No highside power supply, DC drive coupling.



--

John Larkin Highland Technology, Inc

The cork popped merrily, and Lord Peter rose to his feet.
"Bunter", he said, "I give you a toast. The triumph of Instinct over Reason"
 
On Sun, 19 Jan 2020 19:50:41 +0100, Piotr Wyderski
<peter.pan@neverland.mil> wrote:

jlarkin@highlandsniptechnology.com wrote:

Is PWL a floating power supply, on the high side? Is that available?

Yes.

Everything is grounded in your sim.

Just for the ease of prototyping of the core idea. At the beginning the
modelling of the bipolar transformer drive was crazy enough. It will be
fully isolated in the real application.

I'd consider going optical, a PV supply and a dual (or maybe single)
optoisolator. No highside power supply, DC drive coupling.

Optical devices have too high FIT value. To be eradicated just after
electrochemical capacitors.

Best regards, Piotr
Click to expand...

Tons of parts accumulate FITs too. I haven't found optos to be
unreliable. If PWL is an existing floating power supply, the whole
thing reduces to one optocoupler and no states to have hazards.



--

John Larkin Highland Technology, Inc

The cork popped merrily, and Lord Peter rose to his feet.
"Bunter", he said, "I give you a toast. The triumph of Instinct over Reason"
 
On 19/01/2020 5:41 pm, Piotr Wyderski wrote:
Hi,

I need to slowly drive a high-voltage high-side MOSFET in a 5kV isolated
setup. This use case reminds an electronic fuse: the MOSFET is expected
to be almost always ON, but the driver needs to start in an OFF
condition. Generally the answer would be Si8261, but it
requires ~50mW. So I have devised a much less energy hungry driver based
on a tiny 1:1 bipolar drive pulse transformer and a 555 (the CMOS
variant, but I don't have a model for it). It looks fine, switching a
180nC MOSFET in under 2us; it should be possible to be tweaked to
consume a milliwatt or two as well. The sim is attached below. My
concern is with the initial conditions: is this setup guaranteed to
reset the timer at power-on
provided the transformer is not energized?

Comments warmly welcomed.

    Best regards, Piotr

Version 4
SHEET 1 2408 772
WIRE 464 -928 64 -928
WIRE 176 -832 128 -832
WIRE 304 -832 256 -832
WIRE 544 -832 384 -832
WIRE 128 -704 128 -832
WIRE 176 -704 128 -704
WIRE 544 -704 544 -832
WIRE 544 -704 400 -704
WIRE 128 -688 128 -704
WIRE 64 -640 64 -928
WIRE 176 -640 64 -640
WIRE 1120 -592 880 -592
WIRE 176 -576 -16 -576
WIRE 464 -576 464 -928
WIRE 464 -576 400 -576
WIRE 880 -560 880 -592
WIRE 176 -512 128 -512
WIRE 432 -512 400 -512
WIRE 432 -496 432 -512
WIRE 880 -432 880 -480
WIRE 1120 -432 1120 -592
WIRE 432 -416 432 -432
WIRE -16 -352 -16 -576
WIRE 656 -352 -16 -352
WIRE 832 -352 736 -352
WIRE 880 -320 880 -336
WIRE 1120 -320 1120 -352
WIRE 128 -272 128 -512
WIRE 544 -272 544 -704
WIRE 544 -272 128 -272
WIRE 544 -192 544 -272
WIRE 64 -96 64 -640
WIRE 352 -96 64 -96
WIRE 544 -96 544 -112
WIRE 544 -96 432 -96
WIRE 544 -64 544 -96
WIRE 240 48 144 48
WIRE 352 48 304 48
WIRE 544 48 544 16
WIRE 144 80 144 48
WIRE 352 112 352 48
WIRE 144 192 144 160
WIRE 144 288 144 272
WIRE 352 288 352 192
FLAG 144 288 0
FLAG 352 288 0
FLAG 880 -320 0
FLAG 1120 -320 0
FLAG 128 -688 0
FLAG 432 -416 0
FLAG 544 48 0
SYMBOL voltage 144 64 R0
WINDOW 3 -973 45 Left 2
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value PULSE(0 {Vkey} 100u {Tkey_rise} {Tkey_fall} {Tkey_on}
{Tkey_period})
SYMBOL cap 304 32 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C2
SYMATTR Value 10Âľ
SYMBOL ind2 336 96 R0
WINDOW 3 -12 60 Right 2
SYMATTR InstName L1
SYMATTR Value 400Âľ
SYMATTR Type ind
SYMBOL ind2 448 -80 M270
WINDOW 0 32 56 VTop 2
WINDOW 3 4 56 VBottom 2
SYMATTR InstName L2
SYMATTR Value 400Âľ
SYMATTR Type ind
SYMBOL res 752 -368 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R3
SYMATTR Value 50
SYMBOL nmos 832 -432 R0
SYMATTR InstName M1
SYMATTR Value IXTH88N30P
SYMBOL res 864 -576 R0
SYMATTR InstName R4
SYMATTR Value 300
SYMBOL voltage 1120 -448 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V3
SYMATTR Value 300
SYMBOL Misc\\NE555 288 -608 R0
SYMATTR InstName U1
SYMBOL voltage 272 -832 R90
WINDOW 0 -32 56 VBottom 2
WINDOW 3 -84 34 VTop 2
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V4
SYMATTR Value PWL(0 0 100u 9.6)
SYMBOL res 400 -848 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R2
SYMATTR Value 1m
SYMBOL cap 416 -496 R0
SYMATTR InstName C1
SYMATTR Value 1n
SYMBOL res 528 -80 R0
SYMATTR InstName R1
SYMATTR Value 20k
SYMBOL res 528 -208 R0
SYMATTR InstName R6
SYMATTR Value 20k
SYMBOL voltage 144 176 R0
WINDOW 3 -973 45 Left 2
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V2
SYMATTR Value PULSE(0 {-Vkey} 550u {Tkey_rise} {Tkey_fall} {Tkey_on}
{Tkey_period})
TEXT 110 312 Left 2 !.tran 1m
TEXT 328 -8 Left 2 !K L1 L2 0.98
TEXT 32 424 Left 2 !.param Vkey=2.7
TEXT 32 456 Left 2 !.param Tkey_rise=10n Tkey_fall=10n Tkey_on=1u
Tkey_period=100u
Click to expand...

Simple answer is no. In the absence of transformer pulses the Trig and
Thrs pins will power up at 50% Vdd which is midway between their
comparsion references so neither state can be assured. You need to find
a way to assert Rst or drive Thrs higher than 2Vdd/3 to get power up in
the output low state.

piglet



In practice 555's tend to power up
 
jlarkin@highlandsniptechnology.com wrote:

> Is PWL a floating power supply, on the high side? Is that available?

Yes.

> Everything is grounded in your sim.

Just for the ease of prototyping of the core idea. At the beginning the
modelling of the bipolar transformer drive was crazy enough. It will be
fully isolated in the real application.

I'd consider going optical, a PV supply and a dual (or maybe single)
optoisolator. No highside power supply, DC drive coupling.
Click to expand...

Optical devices have too high FIT value. To be eradicated just after
electrochemical capacitors.

Best regards, Piotr
 
Hi Piotr,

I hacked your schematic into this simple minded version that will start
up always with output low. Gate can be turned off within a few us of the
keep-alive pulse stream disappearing - I dont know if that is responsive
enough but you did say slow :)

Choose C2 value to be near resonant to L.


Version 4
SHEET 1 2408 772
WIRE 464 -928 64 -928
WIRE 176 -832 128 -832
WIRE 304 -832 256 -832
WIRE 544 -832 384 -832
WIRE 128 -704 128 -832
WIRE 176 -704 128 -704
WIRE 544 -704 544 -832
WIRE 544 -704 400 -704
WIRE 128 -688 128 -704
WIRE 64 -640 64 -928
WIRE 176 -640 64 -640
WIRE 1120 -592 880 -592
WIRE 176 -576 -16 -576
WIRE 464 -576 464 -928
WIRE 464 -576 400 -576
WIRE 880 -560 880 -592
WIRE 176 -512 128 -512
WIRE 432 -512 400 -512
WIRE 432 -496 432 -512
WIRE 880 -432 880 -480
WIRE 1120 -432 1120 -592
WIRE 432 -416 432 -432
WIRE -16 -352 -16 -576
WIRE 656 -352 -16 -352
WIRE 832 -352 736 -352
WIRE 880 -320 880 -336
WIRE 1120 -320 1120 -352
WIRE 128 -288 128 -512
WIRE 288 -288 128 -288
WIRE 544 -288 544 -704
WIRE 544 -288 288 -288
WIRE 288 -256 288 -288
WIRE 128 -240 128 -288
WIRE 64 -144 64 -640
WIRE 128 -144 128 -176
WIRE 128 -144 64 -144
WIRE 288 -144 288 -176
WIRE 288 -144 128 -144
WIRE 64 -80 64 -144
WIRE 144 -80 64 -80
WIRE 336 -80 208 -80
WIRE 544 -80 544 -288
WIRE 544 -80 416 -80
WIRE 272 32 -96 32
WIRE 464 32 336 32
WIRE 464 112 464 32
WIRE -96 160 -96 32
WIRE -96 272 -96 240
WIRE 464 288 464 192
FLAG 464 288 0
FLAG 880 -320 0
FLAG 1120 -320 0
FLAG 128 -688 0
FLAG 432 -416 0
FLAG -96 272 0
SYMBOL cap 336 16 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C2
SYMATTR Value 68p
SYMBOL ind2 448 96 R0
WINDOW 3 -12 60 Right 2
SYMATTR Value 400Âľ
SYMATTR InstName L1
SYMATTR Type ind
SYMBOL ind2 432 -64 M270
WINDOW 0 32 56 VTop 2
WINDOW 3 4 56 VBottom 2
SYMATTR InstName L2
SYMATTR Value 400Âľ
SYMATTR Type ind
SYMBOL res 752 -368 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R3
SYMATTR Value 50
SYMBOL nmos 832 -432 R0
SYMATTR InstName M1
SYMATTR Value IXTH88N30P
SYMBOL res 864 -576 R0
SYMATTR InstName R4
SYMATTR Value 300
SYMBOL voltage 1120 -448 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V3
SYMATTR Value 300
SYMBOL Misc\\NE555 288 -608 R0
SYMATTR InstName U1
SYMBOL voltage 272 -832 R90
WINDOW 0 -32 56 VBottom 2
WINDOW 3 -84 34 VTop 2
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V4
SYMATTR Value PWL(0 0 100u 9.6)
SYMBOL res 400 -848 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R2
SYMATTR Value 1m
SYMBOL cap 416 -496 R0
SYMATTR InstName C1
SYMATTR Value 1n
SYMBOL res 272 -272 R0
SYMATTR InstName R6
SYMATTR Value 20k
SYMBOL voltage -96 144 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V5
SYMATTR Value PULSE(0 2.7 300u 10n 10n 0.5u 1u 400)
SYMBOL diode 144 -64 R270
WINDOW 0 32 32 VTop 2
WINDOW 3 0 32 VBottom 2
SYMATTR InstName D1
SYMATTR Value 1N914
SYMBOL cap 112 -240 R0
SYMATTR InstName C3
SYMATTR Value 100p
TEXT -160 416 Left 2 !.tran 1m
TEXT 512 184 Left 2 !K L1 L2 0.98

piglet
 
The bipolar 555 is piss, obviously you'd use a CMOS model, yeah.

I've done that before (happened to be a discrete circuit). But have you
thought about common mode immunity yet?

Consider using something like this,
https://www.digikey.com/product-detail/en/pulse-electronics-power/PH9185.011NLT/553-2052-1-ND/3503429
and don't simply nod at the CT windings: take full advantage of them. The
CMRR of this part is surprisingly good, up to surprisingly high frequencies.
You will have a very hard time doing it unbalanced.

Even an Ethernet transformer will do, if you don't mind the 1kV isoation
rating (in this case obviously you would mind). The flux is quite small,
but more than adequate for little pulses, and the isolation barrier is
smaller (lower capacitance). Double balanced design again, and usually
comes with CMCs included (for even more immunity).

Forget if you can find COTS Ethernet transformers with reinforced kV+
isolation, if so that may be handy. Huh, probably same price as the Pulse
part anyway...

Another approach that may be of interest, pulse or frequency modulation.
ASK through one transformer allows you to maintain high-side power, while
filtering the signal for immunity.

OOK through two transformers, you could do the same while sharpening it with
a flip-flop (in essence, detect and filter two signal paths, and route them
to your 555's inputs).

PSK would be... interesting to decode without a clock reference (two
transformers would be easy, one would be harder), but could be unambiguous
(in phase = on, etc.; or 90 deg. to the right = on, etc.).

FM, you could use a crude discriminator, like a missing-pulse detector; give
or take additional filtering before or after, you can clean up most
interference.

Could all be done at VHF too, in which case planar magnetics are feasible
(coreless or otherwise), or even at UHF where interference from power
supplies is unlikely and the resulting bandwidth (which might be say 5-10%
of Fc) is competitive with monolithic drivers.

Tim

--
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Design
Website: https://www.seventransistorlabs.com/

"Piotr Wyderski" <peter.pan@neverland.mil> wrote in message
news:r024bu$4ra$1@gioia.aioe.org...
Hi,

I need to slowly drive a high-voltage high-side MOSFET in a 5kV isolated
setup. This use case reminds an electronic fuse: the MOSFET is expected to
be almost always ON, but the driver needs to start in an OFF condition.
Generally the answer would be Si8261, but it
requires ~50mW. So I have devised a much less energy hungry driver based
on a tiny 1:1 bipolar drive pulse transformer and a 555 (the CMOS variant,
but I don't have a model for it). It looks fine, switching a 180nC MOSFET
in under 2us; it should be possible to be tweaked to consume a milliwatt
or two as well. The sim is attached below. My concern is with the initial
conditions: is this setup guaranteed to reset the timer at power-on
provided the transformer is not energized?

Comments warmly welcomed.

Best regards, Piotr

Version 4
SHEET 1 2408 772
WIRE 464 -928 64 -928
WIRE 176 -832 128 -832
WIRE 304 -832 256 -832
WIRE 544 -832 384 -832
WIRE 128 -704 128 -832
WIRE 176 -704 128 -704
WIRE 544 -704 544 -832
WIRE 544 -704 400 -704
WIRE 128 -688 128 -704
WIRE 64 -640 64 -928
WIRE 176 -640 64 -640
WIRE 1120 -592 880 -592
WIRE 176 -576 -16 -576
WIRE 464 -576 464 -928
WIRE 464 -576 400 -576
WIRE 880 -560 880 -592
WIRE 176 -512 128 -512
WIRE 432 -512 400 -512
WIRE 432 -496 432 -512
WIRE 880 -432 880 -480
WIRE 1120 -432 1120 -592
WIRE 432 -416 432 -432
WIRE -16 -352 -16 -576
WIRE 656 -352 -16 -352
WIRE 832 -352 736 -352
WIRE 880 -320 880 -336
WIRE 1120 -320 1120 -352
WIRE 128 -272 128 -512
WIRE 544 -272 544 -704
WIRE 544 -272 128 -272
WIRE 544 -192 544 -272
WIRE 64 -96 64 -640
WIRE 352 -96 64 -96
WIRE 544 -96 544 -112
WIRE 544 -96 432 -96
WIRE 544 -64 544 -96
WIRE 240 48 144 48
WIRE 352 48 304 48
WIRE 544 48 544 16
WIRE 144 80 144 48
WIRE 352 112 352 48
WIRE 144 192 144 160
WIRE 144 288 144 272
WIRE 352 288 352 192
FLAG 144 288 0
FLAG 352 288 0
FLAG 880 -320 0
FLAG 1120 -320 0
FLAG 128 -688 0
FLAG 432 -416 0
FLAG 544 48 0
SYMBOL voltage 144 64 R0
WINDOW 3 -973 45 Left 2
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value PULSE(0 {Vkey} 100u {Tkey_rise} {Tkey_fall} {Tkey_on}
{Tkey_period})
SYMBOL cap 304 32 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C2
SYMATTR Value 10Âľ
SYMBOL ind2 336 96 R0
WINDOW 3 -12 60 Right 2
SYMATTR InstName L1
SYMATTR Value 400Âľ
SYMATTR Type ind
SYMBOL ind2 448 -80 M270
WINDOW 0 32 56 VTop 2
WINDOW 3 4 56 VBottom 2
SYMATTR InstName L2
SYMATTR Value 400Âľ
SYMATTR Type ind
SYMBOL res 752 -368 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R3
SYMATTR Value 50
SYMBOL nmos 832 -432 R0
SYMATTR InstName M1
SYMATTR Value IXTH88N30P
SYMBOL res 864 -576 R0
SYMATTR InstName R4
SYMATTR Value 300
SYMBOL voltage 1120 -448 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V3
SYMATTR Value 300
SYMBOL Misc\\NE555 288 -608 R0
SYMATTR InstName U1
SYMBOL voltage 272 -832 R90
WINDOW 0 -32 56 VBottom 2
WINDOW 3 -84 34 VTop 2
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V4
SYMATTR Value PWL(0 0 100u 9.6)
SYMBOL res 400 -848 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R2
SYMATTR Value 1m
SYMBOL cap 416 -496 R0
SYMATTR InstName C1
SYMATTR Value 1n
SYMBOL res 528 -80 R0
SYMATTR InstName R1
SYMATTR Value 20k
SYMBOL res 528 -208 R0
SYMATTR InstName R6
SYMATTR Value 20k
SYMBOL voltage 144 176 R0
WINDOW 3 -973 45 Left 2
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V2
SYMATTR Value PULSE(0 {-Vkey} 550u {Tkey_rise} {Tkey_fall} {Tkey_on}
{Tkey_period})
TEXT 110 312 Left 2 !.tran 1m
TEXT 328 -8 Left 2 !K L1 L2 0.98
TEXT 32 424 Left 2 !.param Vkey=2.7
TEXT 32 456 Left 2 !.param Tkey_rise=10n Tkey_fall=10n Tkey_on=1u
Tkey_period=100u
Click to expand...
 
jlarkin@highlandsniptechnology.com wrote:
On Sun, 19 Jan 2020 19:50:41 +0100, Piotr Wyderski
peter.pan@neverland.mil> wrote:

jlarkin@highlandsniptechnology.com wrote:

Is PWL a floating power supply, on the high side? Is that available?

Yes.

Everything is grounded in your sim.

Just for the ease of prototyping of the core idea. At the beginning the
modelling of the bipolar transformer drive was crazy enough. It will be
fully isolated in the real application.

I'd consider going optical, a PV supply and a dual (or maybe single)
optoisolator. No highside power supply, DC drive coupling.

Optical devices have too high FIT value. To be eradicated just after
electrochemical capacitors.

Best regards, Piotr

Tons of parts accumulate FITs too. I haven't found optos to be
unreliable. If PWL is an existing floating power supply, the whole
thing reduces to one optocoupler and no states to have hazards.
Click to expand...

MIL-HDBK-217 (which introduced FITs IIRC) is a random-number generator.

You can improve your design's FITs by taking out all the ESD protection,
current limiters, fuses, supply-reversal protection diodes, self-test
capability, and other such non-essential functions.

It also assumes that all failures have an Arrhenius temperature
dependence, which is nuts.

Cheers

Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com
 
On Sun, 19 Jan 2020 18:26:14 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

jlarkin@highlandsniptechnology.com wrote:
On Sun, 19 Jan 2020 19:50:41 +0100, Piotr Wyderski
peter.pan@neverland.mil> wrote:

jlarkin@highlandsniptechnology.com wrote:

Is PWL a floating power supply, on the high side? Is that available?

Yes.

Everything is grounded in your sim.

Just for the ease of prototyping of the core idea. At the beginning the
modelling of the bipolar transformer drive was crazy enough. It will be
fully isolated in the real application.

I'd consider going optical, a PV supply and a dual (or maybe single)
optoisolator. No highside power supply, DC drive coupling.

Optical devices have too high FIT value. To be eradicated just after
electrochemical capacitors.

Best regards, Piotr

Tons of parts accumulate FITs too. I haven't found optos to be
unreliable. If PWL is an existing floating power supply, the whole
thing reduces to one optocoupler and no states to have hazards.

MIL-HDBK-217 (which introduced FITs IIRC) is a random-number generator.
Click to expand...

The handbook doesn't have a table entry for the FITS of "bad design."



--

John Larkin Highland Technology, Inc

The cork popped merrily, and Lord Peter rose to his feet.
"Bunter", he said, "I give you a toast. The triumph of Instinct over Reason"
 
On Sun, 19 Jan 2020 17:34:39 -0600, "Tim Williams"
<tiwill@seventransistorlabs.com> wrote:

The bipolar 555 is piss, obviously you'd use a CMOS model, yeah.

I've done that before (happened to be a discrete circuit). But have you
thought about common mode immunity yet?

Consider using something like this,
https://www.digikey.com/product-detail/en/pulse-electronics-power/PH9185.011NLT/553-2052-1-ND/3503429
and don't simply nod at the CT windings: take full advantage of them. The
CMRR of this part is surprisingly good, up to surprisingly high frequencies.
You will have a very hard time doing it unbalanced.

Even an Ethernet transformer will do, if you don't mind the 1kV isoation
rating (in this case obviously you would mind). The flux is quite small,
but more than adequate for little pulses, and the isolation barrier is
smaller (lower capacitance). Double balanced design again, and usually
comes with CMCs included (for even more immunity).

Forget if you can find COTS Ethernet transformers with reinforced kV+
isolation, if so that may be handy. Huh, probably same price as the Pulse
part anyway...

Another approach that may be of interest, pulse or frequency modulation.
ASK through one transformer allows you to maintain high-side power, while
filtering the signal for immunity.

OOK through two transformers, you could do the same while sharpening it with
a flip-flop (in essence, detect and filter two signal paths, and route them
to your 555's inputs).

PSK would be... interesting to decode without a clock reference (two
transformers would be easy, one would be harder), but could be unambiguous
(in phase = on, etc.; or 90 deg. to the right = on, etc.).

FM, you could use a crude discriminator, like a missing-pulse detector; give
or take additional filtering before or after, you can clean up most
interference.

Could all be done at VHF too, in which case planar magnetics are feasible
(coreless or otherwise), or even at UHF where interference from power
supplies is unlikely and the resulting bandwidth (which might be say 5-10%
of Fc) is competitive with monolithic drivers.

Tim
Click to expand...

How about a retriggerable one-shot? As long as you keep pulsing it,
the mosfet is on.



--

John Larkin Highland Technology, Inc

The cork popped merrily, and Lord Peter rose to his feet.
"Bunter", he said, "I give you a toast. The triumph of Instinct over Reason"
 
On Sunday, January 19, 2020 at 9:41:24 AM UTC-8, Piotr Wyderski wrote:

I need to slowly drive a high-voltage high-side MOSFET in a 5kV isolated
setup. This use case reminds an electronic fuse: the MOSFET is expected
to be almost always ON, but the driver needs to start in an OFF
condition. ... I have devised a much less energy hungry driver based
on a tiny 1:1 bipolar drive pulse transformer and a 555
Click to expand...

Not sure about 5kV transformer being 'tiny'. Why not pulse
a dual optoisolator, and at the high side have it set/reset a CMOS flipflop.
Even if it takes a couple of milliamps to strobe the opto, if you do that
for a microsecond every tenth of a second, it only takes a tiny
average current at the low side. If you put some capacitance
on the HV side power, the CMOS drive is quite peppy, even at
trickle-from-a-Li-cell power drain on the high side.
 
whit3rd wrote:

> Not sure about 5kV transformer being 'tiny'.

It is, fits nicely within its creepage area. A 6mm OD F938 core + 2x11
turns made of the thinnest available TIW.

> Why not pulse a dual optoisolator, and at the high side have it set/reset a CMOS flipflop.

This is basically what the 555 is. AFAIK there are no CMOS flip-flops
capable of gate drive voltages/current in SO8 or smaller. Flip-flops
with predefined initial state are even more rare.

My first "correct on the paper" approach was to use a SOT23 MOSFET
driver with UVLO and make a latching buffer out of it with a resistive
divider between out and in. The UVLO would ensure the initial off state.
There are parts with -5V Vin tolerance, so a simple bipolar inductive buffer
state override at the input would work safely without any additional
parts -- just overpower the divider for enough microseconds.

The problem would be with Cgd and Cgs of the driven transistor -- a
sufficiently strong transient would be able to override the buffer state
as well. So two buffers would be necessary in series, one to manage the
state
and one to drive the FET without any feedback. Which... the 555 is. :)

Even if it takes a couple of milliamps to strobe the opto, if you do that
for a microsecond every tenth of a second, it only takes a tiny
average current at the low side.
Click to expand...

Sure -- my pulse trafo is going to be driven exactly the same way.
The sim pulse train is dense just not to wait too long for the sim to
complete. The duty cycle in practice would be much lower than that,
maybe a state change per week or so. So only the floating side energy
consumption + all the internal housekeeping expenses matter.

Best regards, Piotr
 
DecadentLinuxUserNumeroUno@decadence.org wrote in
news:r03n3j$13cq$1@gioia.aioe.org:

Piotr Wyderski <peter.pan@neverland.mil> wrote in
news:r03jiu$jt1$1@gioia.aioe.org:

whit3rd wrote:

Not sure about 5kV transformer being 'tiny'.

It is, fits nicely within its creepage area. A 6mm OD F938 core +
2x11 turns made of the thinnest available TIW.


I made a 15kV supply that you could fit 6 of into a pack of
cigarettes.

The multiplier section was potted in a 1 inch square box just
under
3/8 inch tall. The transformer was about 1500 V per section 5
sections, and that is what fed the Multiplier. I think it was
like #54 wire.
Click to expand...

Was like 300V per segment.
 
Piotr Wyderski <peter.pan@neverland.mil> wrote in
news:r03jiu$jt1$1@gioia.aioe.org:

whit3rd wrote:

Not sure about 5kV transformer being 'tiny'.

It is, fits nicely within its creepage area. A 6mm OD F938 core +
2x11 turns made of the thinnest available TIW.
Click to expand...

I made a 15kV supply that you could fit 6 of into a pack of cigarettes.

The multiplier section was potted in a 1 inch square box just under
3/8 inch tall. The transformer was about 1500 V per section 5
sections, and that is what fed the Multiplier. I think it was like #54
wire.
 
On Sun, 19 Jan 2020 20:43:40 -0800 (PST), whit3rd <whit3rd@gmail.com>
wrote:

On Sunday, January 19, 2020 at 9:41:24 AM UTC-8, Piotr Wyderski wrote:

I need to slowly drive a high-voltage high-side MOSFET in a 5kV isolated
setup. This use case reminds an electronic fuse: the MOSFET is expected
to be almost always ON, but the driver needs to start in an OFF
condition. ... I have devised a much less energy hungry driver based
on a tiny 1:1 bipolar drive pulse transformer and a 555

Not sure about 5kV transformer being 'tiny'. Why not pulse
a dual optoisolator, and at the high side have it set/reset a CMOS flipflop.
Even if it takes a couple of milliamps to strobe the opto, if you do that
for a microsecond every tenth of a second, it only takes a tiny
average current at the low side. If you put some capacitance
on the HV side power, the CMOS drive is quite peppy, even at
trickle-from-a-Li-cell power drain on the high side.
Click to expand...

This sort of thing is easier and has no states that can be glitched.

https://www.dropbox.com/s/pwi91ext9cclhzz/Gate_Driver_3.JPG?raw=1

https://www.dropbox.com/s/t7v9rrx1gbcqq7a/Faster_Opto_Totem.JPG?raw=1

Add a resistor across one phototransistor to define a default state,
probably mosfet off.





--

John Larkin Highland Technology, Inc

The cork popped merrily, and Lord Peter rose to his feet.
"Bunter", he said, "I give you a toast. The triumph of Instinct over Reason"
 
jlarkin@highlandsniptechnology.com wrote:

How about a retriggerable one-shot? As long as you keep pulsing it,
the mosfet is on.
Click to expand...

This is a good idea, too. Thanks, John!

Best regards, Piotr
 
On Mon, 20 Jan 2020 19:06:57 +0100, Piotr Wyderski
<peter.pan@neverland.mil> wrote:

jlarkin@highlandsniptechnology.com wrote:

How about a retriggerable one-shot? As long as you keep pulsing it,
the mosfet is on.

This is a good idea, too. Thanks, John!

Best regards, Piotr
Click to expand...

It might be scary to float a flip-flop up there. High voltage circuits
might make EMI that could confuse a flop. I like the idea of no drive
==> fet is guaranteed off.

It could be simple: transformer, 3.3 or 5v Tiny cmos one-shot, and
maybe a 10V gate driver. On the bottom side, just gate a clock into
the transformer primary, or don't.







--

John Larkin Highland Technology, Inc

The cork popped merrily, and Lord Peter rose to his feet.
"Bunter", he said, "I give you a toast. The triumph of Instinct over Reason"
 
On 20/01/2020 7:06 pm, jlarkin@highlandsniptechnology.com wrote:
On Mon, 20 Jan 2020 19:06:57 +0100, Piotr Wyderski
peter.pan@neverland.mil> wrote:

jlarkin@highlandsniptechnology.com wrote:

How about a retriggerable one-shot? As long as you keep pulsing it,
the mosfet is on.

This is a good idea, too. Thanks, John!

Best regards, Piotr

It might be scary to float a flip-flop up there. High voltage circuits
might make EMI that could confuse a flop. I like the idea of no drive
==> fet is guaranteed off.

It could be simple: transformer, 3.3 or 5v Tiny cmos one-shot, and
maybe a 10V gate driver. On the bottom side, just gate a clock into
the transformer primary, or don't.
Click to expand...
Isn't that just what I posted 24 hours ago - using Piotr's 555 as the
retriggerable?

With minor refinement he could probably get the pulse transformer to
also power the driver thus taking on the floating power supply role, use
high pulse rate for driver ON and low pulse rate for driver OFF - FSK.

piglet
 
Piotr Wyderski <peter.pan@neverland.mil> wrote in
news:r024bu$4ra$1@gioia.aioe.org:

Hi,

I need to slowly drive a high-voltage high-side MOSFET in a 5kV
isolated setup. This use case reminds an electronic fuse: the
MOSFET is expected to be almost always ON, but the driver needs to
start in an OFF condition. Generally the answer would be Si8261,
but it requires ~50mW. So I have devised a much less energy hungry
driver based on a tiny 1:1 bipolar drive pulse transformer and a
555 (the CMOS variant, but I don't have a model for it). It looks
fine, switching a 180nC MOSFET in under 2us; it should be possible
to be tweaked to consume a milliwatt or two as well. The sim is
attached below. My concern is with the initial conditions: is this
setup guaranteed to reset the timer at power-on
provided the transformer is not energized?

Comments warmly welcomed.

Best regards, Piotr
Click to expand...

An audio chip with a VFO driving it. The audio chip is adjustable on
the output power. So 2 points of adjustment. They drive downstream
circuits pretty darn good, unless you want faster oscillation than
they cover.
 
On Monday, January 20, 2020 at 12:34:31 AM UTC+1, Tim Williams wrote:
The bipolar 555 is piss, obviously you'd use a CMOS model, yeah.

I've done that before (happened to be a discrete circuit). But have you
thought about common mode immunity yet?

Consider using something like this,
https://www.digikey.com/product-detail/en/pulse-electronics-power/PH9185.011NLT/553-2052-1-ND/3503429
and don't simply nod at the CT windings: take full advantage of them. The
CMRR of this part is surprisingly good, up to surprisingly high frequencies.
You will have a very hard time doing it unbalanced.

Even an Ethernet transformer will do, if you don't mind the 1kV isoation
rating (in this case obviously you would mind). The flux is quite small,
but more than adequate for little pulses, and the isolation barrier is
smaller (lower capacitance). Double balanced design again, and usually
comes with CMCs included (for even more immunity).

Forget if you can find COTS Ethernet transformers with reinforced kV+
isolation, if so that may be handy. Huh, probably same price as the Pulse
part anyway...

Another approach that may be of interest, pulse or frequency modulation.
ASK through one transformer allows you to maintain high-side power, while
filtering the signal for immunity.

OOK through two transformers, you could do the same while sharpening it with
a flip-flop (in essence, detect and filter two signal paths, and route them
to your 555's inputs).

PSK would be... interesting to decode without a clock reference (two
transformers would be easy, one would be harder), but could be unambiguous
(in phase = on, etc.; or 90 deg. to the right = on, etc.).

FM, you could use a crude discriminator, like a missing-pulse detector; give
or take additional filtering before or after, you can clean up most
interference.

Could all be done at VHF too, in which case planar magnetics are feasible
(coreless or otherwise), or even at UHF where interference from power
supplies is unlikely and the resulting bandwidth (which might be say 5-10%
of Fc) is competitive with monolithic drivers.
Click to expand...

You can do isolation with spiral coreless coils quite simple:

https://www.researchgate.net/publication/224224765_Insulating_IGBT_driver_with_PCB_integrated_capacitive_coupling_elements

The important parameter to look for is the parasitic capacitance over the isolation barrier, which creates problems with conducted emissions and susceptibility to fast dV/dt transients on the switching node

Another nice paper is this one:

https://www.semanticscholar.org/paper/Coreless-Printed-Circuit-Board-(-PCB-)-Transformers-Sain-Chen/f683ebe9da5a97ce8b9e69a7105105d78979dc41

About modulation, nothing really beats a AM. Just start an oscillator when you need to trigger the FET, transmit the pulse through the transformer, impedance match, rectify and apply to the gate. With <10MHz osc freq and a bleeder resistor you can easily get sub us propagation delays

Cheers

Klaus
 
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