I've looked at a number of data sheets, and they never seem to give a
voltage rating.

Of course, applying any significant DC voltage across an inductor is
unlikely to have a good outcome, but one can certainly put a significant
voltage across one for a short period, and it would be nice to know what
the limits are.

As a random example

https://www.farnell.com/datasheets/1870387.pdf

The obvious concerns here are breakdown of the insulation between the
wire and the core, and between windings at the two ends where they are
close together.

Sylvia.

On Sun, 6 Mar 2022 10:23:29 +1100, Sylvia Else <sylvia@email.invalid>
wrote:

>I've looked at a number of data sheets, and they never seem to give a
>voltage rating.
>
>Of course, applying any significant DC voltage across an inductor is
>unlikely to have a good outcome, but one can certainly put a significant
>voltage across one for a short period, and it would be nice to know what
>the limits are.
>
>As a random example
>
>https://www.farnell.com/datasheets/1870387.pdf

Powdered iron can get lossy if you drive it hard. Then it gets hot and
everything gets worse. KoolMu or Sendust has become affordable.

>
>The obvious concerns here are breakdown of the insulation between the
>wire and the core, and between windings at the two ends where they are
>close together.
>
>Sylvia.

I think a few of the Coilcraft parts have voltage ratings, but it's
rare. The dual-winding guys, like DRQ127, are probably bifalar and
have more ways to arc.

I usually test them.

How much voltage were you considering? That toroid looks pretty good.

Class D amp?

--

I yam what I yam - Popeye

On 06-Mar-22 10:59 am, jlarkin@highlandsniptechnology.com wrote:
> On Sun, 6 Mar 2022 10:23:29 +1100, Sylvia Else <sylvia@email.invalid>
> wrote:
>
>> I've looked at a number of data sheets, and they never seem to give a
>> voltage rating.
>>
>> Of course, applying any significant DC voltage across an inductor is
>> unlikely to have a good outcome, but one can certainly put a significant
>> voltage across one for a short period, and it would be nice to know what
>> the limits are.
>>
>> As a random example
>>
>> https://www.farnell.com/datasheets/1870387.pdf
>
> Powdered iron can get lossy if you drive it hard. Then it gets hot and
> everything gets worse. KoolMu or Sendust has become affordable.
>
>>
>> The obvious concerns here are breakdown of the insulation between the
>> wire and the core, and between windings at the two ends where they are
>> close together.
>>
>> Sylvia.
>
> I think a few of the Coilcraft parts have voltage ratings, but it's
> rare. The dual-winding guys, like DRQ127, are probably bifalar and
> have more ways to arc.
>
> I usually test them.
>
> How much voltage were you considering? That toroid looks pretty good.
>
> Class D amp?
>
>
>

No. I was pondering why LED light fittings need to have a large
electrolytic capacitor with its limited life.

I have a couple of small LEDs illuminating an otherwise frequently pitch
black corridor. They're powered through a transformer, bridge rectifier
and current limiter, with no capacitors at all. They obviously flicker
at 100Hz, but it's not visible.

So then I was thinking that one could use a buck converter directly off
the rectified, but not filtered, mains, hence the voltage requirement.

This has not moved past musings at this point, but I was looking at the
voltage specs for inductors, hence my comment.

Sylvia.

On Sun, 6 Mar 2022 12:21:09 +1100, Sylvia Else <sylvia@email.invalid>
wrote:

>On 06-Mar-22 10:59 am, jlarkin@highlandsniptechnology.com wrote:
>> On Sun, 6 Mar 2022 10:23:29 +1100, Sylvia Else <sylvia@email.invalid>
>> wrote:
>>
>>> I've looked at a number of data sheets, and they never seem to give a
>>> voltage rating.
>>>
>>> Of course, applying any significant DC voltage across an inductor is
>>> unlikely to have a good outcome, but one can certainly put a significant
>>> voltage across one for a short period, and it would be nice to know what
>>> the limits are.
>>>
>>> As a random example
>>>
>>> https://www.farnell.com/datasheets/1870387.pdf
>>
>> Powdered iron can get lossy if you drive it hard. Then it gets hot and
>> everything gets worse. KoolMu or Sendust has become affordable.
>>
>>>
>>> The obvious concerns here are breakdown of the insulation between the
>>> wire and the core, and between windings at the two ends where they are
>>> close together.
>>>
>>> Sylvia.
>>
>> I think a few of the Coilcraft parts have voltage ratings, but it's
>> rare. The dual-winding guys, like DRQ127, are probably bifalar and
>> have more ways to arc.
>>
>> I usually test them.
>>
>> How much voltage were you considering? That toroid looks pretty good.
>>
>> Class D amp?
>>
>>
>>
>
>No. I was pondering why LED light fittings need to have a large
>electrolytic capacitor with its limited life.
>
>I have a couple of small LEDs illuminating an otherwise frequently pitch
>black corridor. They're powered through a transformer, bridge rectifier
>and current limiter, with no capacitors at all. They obviously flicker
>at 100Hz, but it's not visible.
>
>So then I was thinking that one could use a buck converter directly off
>the rectified, but not filtered, mains, hence the voltage requirement.
>
>This has not moved past musings at this point, but I was looking at the
>voltage specs for inductors, hence my comment.
>
>Sylvia.

Lots of LED bulbs have a bridge and a linear IC current limiter but no
cap. A capless switcher is an interesting idea. The LED could run at
constant current at a very high duty cycle.

An inductor like you showed would be fine at hundreds of volts. Test
one to breakdown!

--

I yam what I yam - Popeye

On Sun, 6 Mar 2022 12:21:09 +1100, Sylvia Else <sylvia@email.invalid>
wrote:

>On 06-Mar-22 10:59 am, jlarkin@highlandsniptechnology.com wrote:
>> On Sun, 6 Mar 2022 10:23:29 +1100, Sylvia Else <sylvia@email.invalid>
>> wrote:
>>
>>> I've looked at a number of data sheets, and they never seem to give a
>>> voltage rating.
>>>
>>> Of course, applying any significant DC voltage across an inductor is
>>> unlikely to have a good outcome, but one can certainly put a significant
>>> voltage across one for a short period, and it would be nice to know what
>>> the limits are.
>>>
>>> As a random example
>>>
>>> https://www.farnell.com/datasheets/1870387.pdf
>>
>> Powdered iron can get lossy if you drive it hard. Then it gets hot and
>> everything gets worse. KoolMu or Sendust has become affordable.
>>
>>>
>>> The obvious concerns here are breakdown of the insulation between the
>>> wire and the core, and between windings at the two ends where they are
>>> close together.
>>>
>>> Sylvia.
>>
>> I think a few of the Coilcraft parts have voltage ratings, but it's
>> rare. The dual-winding guys, like DRQ127, are probably bifalar and
>> have more ways to arc.
>>
>> I usually test them.
>>
>> How much voltage were you considering? That toroid looks pretty good.
>>
>> Class D amp?
>>
>>
>>
>
>No. I was pondering why LED light fittings need to have a large
>electrolytic capacitor with its limited life.
>
>I have a couple of small LEDs illuminating an otherwise frequently pitch
>black corridor. They're powered through a transformer, bridge rectifier
>and current limiter, with no capacitors at all. They obviously flicker
>at 100Hz, but it's not visible.
>
>So then I was thinking that one could use a buck converter directly off
>the rectified, but not filtered, mains, hence the voltage requirement.
>
>This has not moved past musings at this point, but I was looking at the
>voltage specs for inductors, hence my comment.
>
>Sylvia.

Low voltage LED lighting and hardware is not mains-rated for safety.

Their safe use is achieved through the isolation transformer, tested
at the time of assembly to 3x book isolation ratings. The secondary
circuit is SELV (Safe Extra Low Voltage).

Led lamps that sub for incandescent bulbs in mains hardware are
constructed with sufficient insulation between the electronics
and the end user, to achieve safe use.

Hardware running at SELV is subjected only to simple flammability
and material/environmental regs.

Mains inductors are invariably core-loss or VT limited, below their
current ratings or corona susceptibility.

If you crunch some numbers, you'll see why direct buck conversion
off the mains, at low power, is not easily practised.

RL

On Saturday, March 5, 2022 at 5:22:29 PM UTC-8, bill....@ieee.org wrote:
> On Sunday, March 6, 2022 at 10:23:41 AM UTC+11, Sylvia Else wrote:
> > I've looked at a number of data sheets, and they never seem to give a
> > voltage rating.

> Wound parts are mostly wound with double-enamelled copper wire, which is good to about 500V.
> Everybody is supposed to know this, which is why it won't get into the part data sheet.

Since the enamel insulation separates adjacent windings, it isn't the device rating at all; if
there's 100 turns, at 1 kV, the adjacent turns have at least 10 volts across each two-layers,
but possibly no more than that. The insulating former (for small power xformers) between
windings and core is probably good for kilovolts. Spaghetti around the wires, and tape
between layers, all add to the voltage-breakdown tolerance, as does pie-winding...

On Sunday, March 6, 2022 at 9:51:48 PM UTC, whit3rd wrote:
> On Saturday, March 5, 2022 at 5:22:29 PM UTC-8, bill....@ieee.org wrote:
> > On Sunday, March 6, 2022 at 10:23:41 AM UTC+11, Sylvia Else wrote:
> > > I've looked at a number of data sheets, and they never seem to give a
> > > voltage rating.

It seems Coilcraft anticipated your question Sylvia:
www.coilcraft.com/getmedia/393e18e1-adbc-45b6-bbe7-5923255e72fc/doc712_Inductor_Voltage_Ratings.pdf

"Working Voltage Ratings Applied to Inductors"
"Why Voltage Ratings Are Not Specified on Inductor Data Sheets"

However I accept someone could have a design that requires
knowing the wire's dielectric breakdown
(tested per IEC 60851-5:2008 test 13, documented per IEC 317-0-1, clause 13 )
The wire maker might declare this, but I suppose only in
special cases would the inductor maker do so.

On 07-Mar-22 10:05 am, Rich S wrote:
> On Sunday, March 6, 2022 at 9:51:48 PM UTC, whit3rd wrote:
>> On Saturday, March 5, 2022 at 5:22:29 PM UTC-8, bill....@ieee.org wrote:
>>> On Sunday, March 6, 2022 at 10:23:41 AM UTC+11, Sylvia Else wrote:
>>>> I've looked at a number of data sheets, and they never seem to give a
>>>> voltage rating.
>
> It seems Coilcraft anticipated your question Sylvia:
> www.coilcraft.com/getmedia/393e18e1-adbc-45b6-bbe7-5923255e72fc/doc712_Inductor_Voltage_Ratings.pdf
>
> "Working Voltage Ratings Applied to Inductors"
> "Why Voltage Ratings Are Not Specified on Inductor Data Sheets"
>
> However I accept someone could have a design that requires
> knowing the wire's dielectric breakdown
> (tested per IEC 60851-5:2008 test 13, documented per IEC 317-0-1, clause 13 )
> The wire maker might declare this, but I suppose only in
> special cases would the inductor maker do so.
>

Thanks for the link - I read it all.

I'd have thought the same issues would arise in the context of mains
transformer primaries, though the consequences of failure may be more
predictable.

Sylvia.

Sylvia Else wrote:
===============
>
> Thanks for the link - I read it all.
>
> I'd have thought the same issues would arise in the context of mains
> transformer primaries, though the consequences of failure may be more
> predictable.
>

** Mains transformers are rated for particular mains supply voltages and frequency.
Some allowance is made for typical spike voltages but to be safe it it wise to add a 250VAC rated cap cap and/or transient suppressor ( ie Varistor) across that winding.

The is no similar way for a maker to rate an inductor, as the possible applications are endless.
Up to the user to figure that out.

....... Phil

On 06-Mar-22 2:12 pm, jlarkin@highlandsniptechnology.com wrote:
> On Sun, 6 Mar 2022 12:21:09 +1100, Sylvia Else <sylvia@email.invalid>
> wrote:
>
>> On 06-Mar-22 10:59 am, jlarkin@highlandsniptechnology.com wrote:
>>> On Sun, 6 Mar 2022 10:23:29 +1100, Sylvia Else <sylvia@email.invalid>
>>> wrote:
>>>
>>>> I've looked at a number of data sheets, and they never seem to give a
>>>> voltage rating.
>>>>
>>>> Of course, applying any significant DC voltage across an inductor is
>>>> unlikely to have a good outcome, but one can certainly put a significant
>>>> voltage across one for a short period, and it would be nice to know what
>>>> the limits are.
>>>>
>>>> As a random example
>>>>
>>>> https://www.farnell.com/datasheets/1870387.pdf
>>>
>>> Powdered iron can get lossy if you drive it hard. Then it gets hot and
>>> everything gets worse. KoolMu or Sendust has become affordable.
>>>
>>>>
>>>> The obvious concerns here are breakdown of the insulation between the
>>>> wire and the core, and between windings at the two ends where they are
>>>> close together.
>>>>
>>>> Sylvia.
>>>
>>> I think a few of the Coilcraft parts have voltage ratings, but it's
>>> rare. The dual-winding guys, like DRQ127, are probably bifalar and
>>> have more ways to arc.
>>>
>>> I usually test them.
>>>
>>> How much voltage were you considering? That toroid looks pretty good.
>>>
>>> Class D amp?
>>>
>>>
>>>
>>
>> No. I was pondering why LED light fittings need to have a large
>> electrolytic capacitor with its limited life.
>>
>> I have a couple of small LEDs illuminating an otherwise frequently pitch
>> black corridor. They're powered through a transformer, bridge rectifier
>> and current limiter, with no capacitors at all. They obviously flicker
>> at 100Hz, but it's not visible.
>>
>> So then I was thinking that one could use a buck converter directly off
>> the rectified, but not filtered, mains, hence the voltage requirement.
>>
>> This has not moved past musings at this point, but I was looking at the
>> voltage specs for inductors, hence my comment.
>>
>> Sylvia.
>
> Lots of LED bulbs have a bridge and a linear IC current limiter but no
> cap. A capless switcher is an interesting idea. The LED could run at
> constant current at a very high duty cycle.
>
> An inductor like you showed would be fine at hundreds of volts. Test
> one to breakdown!
>
>
>
>
>

Seems to work in LTSpice at least:

The switch is a stand-in for a digital isolator.

Apart from V6 which is the incoming mains supply, the various voltage
sources would be small amounts of power derived from the rectified
mains. I haven't simulated the fact that this power would not be
available for short periods.

Version 4
SHEET 1 2324 680
WIRE 112 -400 -800 -400
WIRE -640 -352 -672 -352
WIRE -544 -352 -576 -352
WIRE -368 -352 -544 -352
WIRE -160 -352 -368 -352
WIRE -368 -304 -368 -352
WIRE -160 -272 -160 -352
WIRE -416 -240 -432 -240
WIRE 112 -240 112 -400
WIRE -544 -224 -544 -352
WIRE -224 -224 -256 -224
WIRE -672 -192 -672 -352
WIRE -368 -192 -368 -224
WIRE -256 -192 -256 -224
WIRE -256 -192 -368 -192
WIRE 960 -192 432 -192
WIRE -368 -160 -368 -192
WIRE -160 -160 -160 -176
WIRE 64 -160 -160 -160
WIRE -160 -144 -160 -160
WIRE -256 -96 -256 -192
WIRE -224 -96 -256 -96
WIRE 112 -80 112 -144
WIRE 192 -80 112 -80
WIRE 640 -80 272 -80
WIRE 800 -80 800 -96
WIRE 800 -80 640 -80
WIRE 1184 -80 800 -80
WIRE 1216 -80 1184 -80
WIRE -928 -64 -1024 -64
WIRE -800 -64 -800 -400
WIRE -800 -64 -864 -64
WIRE -160 -32 -160 -48
WIRE 112 -32 112 -80
WIRE 112 -32 -160 -32
WIRE -432 -16 -432 -240
WIRE 304 -16 -432 -16
WIRE 640 -16 640 -80
WIRE 800 -16 800 -80
WIRE -1024 32 -1024 -64
WIRE -1008 32 -1024 32
WIRE -928 32 -1008 32
WIRE -720 32 -864 32
WIRE 64 32 -64 32
WIRE 432 32 432 -192
WIRE 432 32 64 32
WIRE -544 48 -544 -160
WIRE -368 48 -368 -80
WIRE -368 48 -544 48
WIRE -160 48 -160 -32
WIRE -160 48 -368 48
WIRE -64 48 -64 32
WIRE 432 48 432 32
WIRE 960 48 960 -192
WIRE 384 80 336 80
WIRE 512 80 512 64
WIRE 512 80 464 80
WIRE 928 80 512 80
WIRE 1120 80 1008 80
WIRE -1024 96 -1024 32
WIRE 400 112 384 112
WIRE 640 112 640 48
WIRE 640 112 464 112
WIRE 800 112 800 64
WIRE 928 112 800 112
WIRE 368 128 352 128
WIRE 64 144 64 32
WIRE 80 144 64 144
WIRE 304 144 304 -16
WIRE 304 144 240 144
WIRE 1216 144 1216 -80
WIRE 32 160 -64 160
WIRE 416 160 416 144
WIRE 432 160 432 144
WIRE 432 160 416 160
WIRE 448 160 448 144
WIRE 448 160 432 160
WIRE 800 160 800 112
WIRE 448 176 448 160
WIRE 944 176 944 144
WIRE 960 176 960 144
WIRE 960 176 944 176
WIRE 976 176 976 144
WIRE 976 176 960 176
WIRE -160 192 -160 48
WIRE -64 192 -64 160
WIRE 32 192 32 160
WIRE 80 192 32 192
WIRE -1024 208 -1024 176
WIRE -928 208 -1024 208
WIRE -800 208 -800 -64
WIRE -800 208 -864 208
WIRE 960 208 960 176
WIRE 32 224 32 192
WIRE 640 224 640 112
WIRE -1024 240 -1024 208
WIRE -1024 304 -1024 240
WIRE -928 304 -1024 304
WIRE -720 304 -720 32
WIRE -720 304 -864 304
WIRE 800 304 800 240
WIRE 32 320 32 288
WIRE 640 320 640 304
WIRE 1616 320 1456 320
WIRE 1856 320 1616 320
WIRE 1456 352 1456 320
WIRE 160 368 160 240
WIRE 240 368 160 368
WIRE 336 368 336 80
WIRE 336 368 304 368
WIRE 1856 368 1856 320
WIRE -864 400 -1040 400
WIRE -640 400 -864 400
WIRE -1040 432 -1040 400
WIRE 32 432 32 384
WIRE 160 432 160 368
WIRE 160 432 32 432
WIRE 240 432 160 432
WIRE 1120 432 1120 80
WIRE 1120 432 304 432
WIRE -640 448 -640 400
WIRE 160 448 160 432
WIRE 1456 480 1456 432
WIRE 1616 480 1456 480
WIRE 1856 480 1856 432
WIRE 1856 480 1616 480
WIRE -160 528 -160 256
WIRE -1040 560 -1040 512
WIRE -880 560 -1040 560
WIRE -640 560 -640 512
WIRE -640 560 -880 560
WIRE 160 560 160 528
WIRE 176 560 160 560
FLAG -64 272 0
FLAG -64 128 0
FLAG 512 -16 0
FLAG 448 176 0
FLAG 160 96 0
FLAG -672 -112 0
FLAG -720 304 0
FLAG 640 320 0
FLAG 800 304 0
FLAG 960 208 0
FLAG 1216 224 0
FLAG 160 560 0
FLAG -160 528 0
FLAG -416 -288 0
FLAG -1008 32 V6P
FLAG -1024 240 V6N
FLAG -880 560 0
FLAG 1616 480 0
FLAG 1184 -80 VO
FLAG -864 400 PI
FLAG 1616 320 PO
SYMBOL Digital\\dflop 160 96 R0
SYMATTR InstName A1
SYMATTR SpiceLine ref=2.5 VHigh=5 Td=60E-9
SYMBOL voltage -64 176 R0
WINDOW 3 24 96 Invisible 2
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR Value PULSE(0 3 0 1E-8 1E-8 9E-6 1E-5 1000000)
SYMATTR InstName V1
SYMBOL voltage -64 32 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V2
SYMATTR Value 5
SYMBOL voltage 512 80 R180
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V3
SYMATTR Value 0.5
SYMBOL Comparators\\LT1711 432 96 M0
SYMATTR InstName U1
SYMBOL nmos 64 -240 R0
SYMATTR InstName M1
SYMATTR Value BSC42DN25NS3
SYMBOL ind 288 -96 R90
WINDOW 0 5 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName L1
SYMATTR Value 1m
SYMATTR SpiceLine Ipk=0.7 Rser=1.65 Rpar=175118 Cpar=0 mfg="Bourns,
Inc." pn="SRR1210-102M"
SYMBOL cap -560 -224 R0
SYMATTR InstName C1
SYMATTR Value 1E-6
SYMBOL voltage -672 -208 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V5
SYMATTR Value 8
SYMBOL diode -640 -336 R270
WINDOW 0 32 32 VTop 2
WINDOW 3 0 32 VBottom 2
SYMATTR InstName D1
SYMATTR Value 1N914
SYMATTR Description Schottky diode
SYMATTR Type schottky
SYMBOL sw -368 -320 R0
SYMATTR InstName S1
SYMATTR Value ""
SYMATTR SpiceModel MySwitch
SYMBOL voltage -1024 80 R0
WINDOW 123 0 0 Left 0
WINDOW 39 24 124 Left 2
WINDOW 3 -118 55 Left 2
SYMATTR SpiceLine Rser=0.1
SYMATTR InstName V6
SYMATTR Value SINE(0 340 50 0 0 0 2)
SYMBOL diode -864 48 M270
WINDOW 0 32 32 VTop 2
WINDOW 3 0 32 VBottom 2
SYMATTR InstName D2
SYMATTR Value RF101L4S
SYMBOL diode -928 192 M90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName D3
SYMATTR Value RF101L4S
SYMBOL diode -928 -80 M90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName D4
SYMATTR Value RF101L4S
SYMBOL diode -864 320 M270
WINDOW 0 32 32 VTop 2
WINDOW 3 0 32 VBottom 2
SYMATTR InstName D5
SYMATTR Value RF101L4S
SYMBOL cap 624 -16 R0
WINDOW 0 22 6 Left 2
SYMATTR InstName C2
SYMATTR Value 10E-6
SYMBOL res 624 208 R0
SYMATTR InstName R1
SYMATTR Value 1.5
SYMBOL res 784 -32 R0
SYMATTR InstName R2
SYMATTR Value 97900
SYMBOL res 784 144 R0
SYMATTR InstName R3
SYMATTR Value 2000
SYMBOL Comparators\\LT1711 960 96 R0
SYMATTR InstName U2
SYMBOL diode 304 352 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 16 -58 VTop 2
SYMATTR InstName D6
SYMATTR Value 1N4148
SYMBOL diode 304 416 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName D7
SYMATTR Value 1N4148
SYMBOL res 1200 128 R0
SYMATTR InstName R5
SYMATTR Value 100
SYMBOL res 144 432 R0
SYMATTR InstName R4
SYMATTR Value 10000
SYMBOL schottky -144 256 R180
WINDOW 0 24 64 Left 2
WINDOW 3 24 0 Left 2
SYMATTR InstName D8
SYMATTR Value 1N5817
SYMATTR Description Diode
SYMATTR Type diode
SYMBOL Digital\\inv 96 224 R90
SYMATTR InstName A2
SYMATTR SpiceLine VHigh=5 ref=2.5
SYMBOL diode 16 320 R0
SYMATTR InstName D9
SYMATTR Value 1N4148
SYMBOL pnp -224 -48 M180
SYMATTR InstName Q1
SYMATTR Value 2N3906
SYMBOL npn -224 -272 R0
SYMATTR InstName Q2
SYMATTR Value 2N2222
SYMBOL res -384 -176 R0
SYMATTR InstName R6
SYMATTR Value 1000
SYMBOL bi -1040 512 R180
WINDOW 0 24 80 Left 2
WINDOW 3 24 0 Left 2
SYMATTR InstName B1
SYMATTR Value I=-(V(V6P) - V(V6N)) * I(V6)
SYMBOL cap -656 448 R0
SYMATTR InstName C3
SYMATTR Value 1
SYMBOL bi 1456 432 R180
WINDOW 0 24 80 Left 2
WINDOW 3 24 0 Left 2
SYMATTR InstName B2
SYMATTR Value I=V(VO) * I(R5)
SYMBOL cap 1840 368 R0
SYMATTR InstName C4
SYMATTR Value 1
TEXT -216 416 Left 2 !.tran 0 25E-3 0 1E-8
TEXT 168 -288 Left 2 !.model MySwitch SW(Ron=.1 Roff=1Meg Vt=2.5 Vh=0.5
Lser=10n Vser=.6)
TEXT 1704 504 Left 2 !.ic V(PO)=0
TEXT -1040 616 Left 2 !.ic V(PI)=0

On Mon, 7 Mar 2022 19:03:14 +1100, Sylvia Else <sylvia@email.invalid>
wrote:

>On 06-Mar-22 2:12 pm, jlarkin@highlandsniptechnology.com wrote:
>> On Sun, 6 Mar 2022 12:21:09 +1100, Sylvia Else <sylvia@email.invalid>
>> wrote:
>>
>>> On 06-Mar-22 10:59 am, jlarkin@highlandsniptechnology.com wrote:
>>>> On Sun, 6 Mar 2022 10:23:29 +1100, Sylvia Else <sylvia@email.invalid>
>>>> wrote:
>>>>
>>>>> I've looked at a number of data sheets, and they never seem to give a
>>>>> voltage rating.
>>>>>
>>>>> Of course, applying any significant DC voltage across an inductor is
>>>>> unlikely to have a good outcome, but one can certainly put a significant
>>>>> voltage across one for a short period, and it would be nice to know what
>>>>> the limits are.
>>>>>
>>>>> As a random example
>>>>>
>>>>> https://www.farnell.com/datasheets/1870387.pdf
>>>>
>>>> Powdered iron can get lossy if you drive it hard. Then it gets hot and
>>>> everything gets worse. KoolMu or Sendust has become affordable.
>>>>
>>>>>
>>>>> The obvious concerns here are breakdown of the insulation between the
>>>>> wire and the core, and between windings at the two ends where they are
>>>>> close together.
>>>>>
>>>>> Sylvia.
>>>>
>>>> I think a few of the Coilcraft parts have voltage ratings, but it's
>>>> rare. The dual-winding guys, like DRQ127, are probably bifalar and
>>>> have more ways to arc.
>>>>
>>>> I usually test them.
>>>>
>>>> How much voltage were you considering? That toroid looks pretty good.
>>>>
>>>> Class D amp?
>>>>
>>>>
>>>>
>>>
>>> No. I was pondering why LED light fittings need to have a large
>>> electrolytic capacitor with its limited life.
>>>
>>> I have a couple of small LEDs illuminating an otherwise frequently pitch
>>> black corridor. They're powered through a transformer, bridge rectifier
>>> and current limiter, with no capacitors at all. They obviously flicker
>>> at 100Hz, but it's not visible.
>>>
>>> So then I was thinking that one could use a buck converter directly off
>>> the rectified, but not filtered, mains, hence the voltage requirement.
>>>
>>> This has not moved past musings at this point, but I was looking at the
>>> voltage specs for inductors, hence my comment.
>>>
>>> Sylvia.
>>
>> Lots of LED bulbs have a bridge and a linear IC current limiter but no
>> cap. A capless switcher is an interesting idea. The LED could run at
>> constant current at a very high duty cycle.
>>
>> An inductor like you showed would be fine at hundreds of volts. Test
>> one to breakdown!
>>
>>
>>
>>
>>
>
>Seems to work in LTSpice at least:
>
>The switch is a stand-in for a digital isolator.
>
>Apart from V6 which is the incoming mains supply, the various voltage
>sources would be small amounts of power derived from the rectified
>mains. I haven't simulated the fact that this power would not be
>available for short periods.
>
<snip>

LTspice IV threw a 'singular matrix node error' here, but only if
the Philips models for 2N2222 and 2N3906 were used. NSC models
allowed the simulation to run.

I'm not sure that you're going to find a 'digital isolator' that's
designed for PWM - they're usually pretty slow. You might consider
an integrated gate driver + discrete nmos as a lower-parts-count
solution.

If you check the input current, or the current in the freewheeling
diode (probably not included inside the digital isolator, by the way),
you'll see diode current spikes occurring when it turns off and the
switch turns on. The amplitude of these spikes will vary with diode
type and nmos switching speed (slower speeds are generated if a
series gate resistor is present on M1).

These spikes are not simulation artifacts, they are modeling attempts
to simulate schottky capacitance or rectifier reverse recovery.
200V schottkeys are rare beasts, but there are fast recovery
rectifiers offered in the standard LTspice distribution selection
lists.

The Bourns data sheet gives a flux density calculation in gauss
using K * L * dI with a frequency-dependent core loss chart
specific to the SRR1210 series.

In a ripple-regulated circuit dI will vary with frequency - in
the sim it's between 200 and 400mAppk.

In a regulated circuit, the peak to peak flux swing in the choke is
determined by Bppk = V * t / ( N * A)
where
Bppk = peak to peak flux density (Teslas)
V = Vout + Vdfreewheel (volts)
t = Tfreewheel (seconds)
N = number of turns on the choke
A = xsectional area of choke

If you've got a table for the choke's material, you can work
out core loss (W/m^3 - mW/cm^3) and apply that to the volume
of the core geometry being used.

Voltage is present in that equation. For peak or surge, it's
either saturation or turn/terminal breakdown limited. Some
core structures, when impressed with low impedance surges,
will try to turn themselves inside out, in the attempt to
force changes in the magnetic length/area ratio.

Lighting ballast design for the domestic market is not the easiest
road to fame and fortune.

Considering the efficiencies of LED sources and the dominance
of standard hardware formats, it turns into a marketing exercise.

RL

On Sun, 6 Mar 2022 12:21:09 +1100, Sylvia Else <sylvia@email.invalid>
wrote:

>On 06-Mar-22 10:59 am, jlarkin@highlandsniptechnology.com wrote:
>> On Sun, 6 Mar 2022 10:23:29 +1100, Sylvia Else <sylvia@email.invalid>
>> wrote:
>>
>>> I've looked at a number of data sheets, and they never seem to give a
>>> voltage rating.
>>>
>>> Of course, applying any significant DC voltage across an inductor is
>>> unlikely to have a good outcome, but one can certainly put a significant
>>> voltage across one for a short period, and it would be nice to know what
>>> the limits are.
>>>
>>> As a random example
>>>
>>> https://www.farnell.com/datasheets/1870387.pdf
>>
>> Powdered iron can get lossy if you drive it hard. Then it gets hot and
>> everything gets worse. KoolMu or Sendust has become affordable.
>>
>>>
>>> The obvious concerns here are breakdown of the insulation between the
>>> wire and the core, and between windings at the two ends where they are
>>> close together.
>>>
>>> Sylvia.
>>
>> I think a few of the Coilcraft parts have voltage ratings, but it's
>> rare. The dual-winding guys, like DRQ127, are probably bifalar and
>> have more ways to arc.
>>
>> I usually test them.
>>
>> How much voltage were you considering? That toroid looks pretty good.
>>
>> Class D amp?
>>
>>
>>
>
>No. I was pondering why LED light fittings need to have a large
>electrolytic capacitor with its limited life.
>
>I have a couple of small LEDs illuminating an otherwise frequently pitch
>black corridor. They're powered through a transformer, bridge rectifier
>and current limiter, with no capacitors at all. They obviously flicker
>at 100Hz, but it's not visible.
>
>So then I was thinking that one could use a buck converter directly off
>the rectified, but not filtered, mains, hence the voltage requirement.
>
>This has not moved past musings at this point, but I was looking at the
>voltage specs for inductors, hence my comment.
>
>Sylvia.

In any event, new luminaires do tend to try to build into the hardware
any type of ballasting and safety barrier that may be required for
direct sale.

RL

On Sun, 6 Mar 2022 10:23:29 +1100, Sylvia Else <sylvia@email.invalid>
wrote:

>I've looked at a number of data sheets, and they never seem to give a
>voltage rating.
>
>Of course, applying any significant DC voltage across an inductor is
>unlikely to have a good outcome, but one can certainly put a significant
>voltage across one for a short period, and it would be nice to know what
>the limits are.
>
>As a random example
>
>https://www.farnell.com/datasheets/1870387.pdf
>
>The obvious concerns here are breakdown of the insulation between the
>wire and the core, and between windings at the two ends where they are
>close together.
>
>Sylvia.
Voltage rating can be complicated. For instance, to be CE compliant,
Transformer/Coil needs two different insulators between mains (230V
AC) and low voltage side. And so on. I have noticed that there is
usually a reason for those rules, but they are not very obvious and
don't come by accident. And then there is China Export standards.

On Monday, 7 March 2022 at 18:31:20 UTC, LM wrote:

> Voltage rating can be complicated. For instance, to be CE compliant,
> Transformer/Coil needs two different insulators between mains (230V
> AC) and low voltage side. And so on. I have noticed that there is
> usually a reason for those rules, but they are not very obvious and
> don't come by accident. And then there is China Export standards.

Two different insulators or one thicker one called "reinforced insulation"
if its a class 2 (double insulated) product.

John

LM wrote:
------------------
>
> Voltage rating can be complicated. For instance, to be CE compliant,
> Transformer/Coil needs two different insulators between mains (230V
> AC) and low voltage side.
>

** Not just " different" but must be ones specified in the relevant standard.

The enamel coating on copper wire is the first, the second needs to be a non hygroscopic, high softening temp insulator with good stability over decades. Various plastics comply as does fiber sheet and treated cardboard.

> I have noticed that there is usually a reason for those rules, but they are not very obvious and
> don't come by accident.

** Correct - they are the result of hard won experience.

> And then there is China Export standards.

** The rules there is to do whatever you can get away with.

........ Phil

mandag den 7. marts 2022 kl. 22.46.34 UTC+1 skrev palli...@gmail.com:
> LM wrote:
> ------------------
> >
> > Voltage rating can be complicated. For instance, to be CE compliant,
> > Transformer/Coil needs two different insulators between mains (230V
> > AC) and low voltage side.
> >
> ** Not just " different" but must be ones specified in the relevant standard.
>
> The enamel coating on copper wire is the first, the second needs to be a non hygroscopic, high softening temp insulator with good stability over decades. Various plastics comply as does fiber sheet and treated cardboard.
> > I have noticed that there is usually a reason for those rules, but they are not very obvious and
> > don't come by accident.
> ** Correct - they are the result of hard won experience.
> > And then there is China Export standards.
> ** The rules there is to do whatever you can get away with.

as an example: https://youtu.be/w-p3GXXFfQw?t=688

On 08-Mar-22 1:02 am, legg wrote:
> On Mon, 7 Mar 2022 19:03:14 +1100, Sylvia Else <sylvia@email.invalid>
> wrote:
>
>> On 06-Mar-22 2:12 pm, jlarkin@highlandsniptechnology.com wrote:
>>> On Sun, 6 Mar 2022 12:21:09 +1100, Sylvia Else <sylvia@email.invalid>
>>> wrote:
>>>
>>>> On 06-Mar-22 10:59 am, jlarkin@highlandsniptechnology.com wrote:
>>>>> On Sun, 6 Mar 2022 10:23:29 +1100, Sylvia Else <sylvia@email.invalid>
>>>>> wrote:
>>>>>
>>>>>> I've looked at a number of data sheets, and they never seem to give a
>>>>>> voltage rating.
>>>>>>
>>>>>> Of course, applying any significant DC voltage across an inductor is
>>>>>> unlikely to have a good outcome, but one can certainly put a significant
>>>>>> voltage across one for a short period, and it would be nice to know what
>>>>>> the limits are.
>>>>>>
>>>>>> As a random example
>>>>>>
>>>>>> https://www.farnell.com/datasheets/1870387.pdf
>>>>>
>>>>> Powdered iron can get lossy if you drive it hard. Then it gets hot and
>>>>> everything gets worse. KoolMu or Sendust has become affordable.
>>>>>
>>>>>>
>>>>>> The obvious concerns here are breakdown of the insulation between the
>>>>>> wire and the core, and between windings at the two ends where they are
>>>>>> close together.
>>>>>>
>>>>>> Sylvia.
>>>>>
>>>>> I think a few of the Coilcraft parts have voltage ratings, but it's
>>>>> rare. The dual-winding guys, like DRQ127, are probably bifalar and
>>>>> have more ways to arc.
>>>>>
>>>>> I usually test them.
>>>>>
>>>>> How much voltage were you considering? That toroid looks pretty good.
>>>>>
>>>>> Class D amp?
>>>>>
>>>>>
>>>>>
>>>>
>>>> No. I was pondering why LED light fittings need to have a large
>>>> electrolytic capacitor with its limited life.
>>>>
>>>> I have a couple of small LEDs illuminating an otherwise frequently pitch
>>>> black corridor. They're powered through a transformer, bridge rectifier
>>>> and current limiter, with no capacitors at all. They obviously flicker
>>>> at 100Hz, but it's not visible.
>>>>
>>>> So then I was thinking that one could use a buck converter directly off
>>>> the rectified, but not filtered, mains, hence the voltage requirement.
>>>>
>>>> This has not moved past musings at this point, but I was looking at the
>>>> voltage specs for inductors, hence my comment.
>>>>
>>>> Sylvia.
>>>
>>> Lots of LED bulbs have a bridge and a linear IC current limiter but no
>>> cap. A capless switcher is an interesting idea. The LED could run at
>>> constant current at a very high duty cycle.
>>>
>>> An inductor like you showed would be fine at hundreds of volts. Test
>>> one to breakdown!
>>>
>>>
>>>
>>>
>>>
>>
>> Seems to work in LTSpice at least:
>>
>> The switch is a stand-in for a digital isolator.
>>
>> Apart from V6 which is the incoming mains supply, the various voltage
>> sources would be small amounts of power derived from the rectified
>> mains. I haven't simulated the fact that this power would not be
>> available for short periods.
>>
> <snip>
>
> LTspice IV threw a 'singular matrix node error' here, but only if
> the Philips models for 2N2222 and 2N3906 were used. NSC models
> allowed the simulation to run.
>
> I'm not sure that you're going to find a 'digital isolator' that's
> designed for PWM - they're usually pretty slow. You might consider
> an integrated gate driver + discrete nmos as a lower-parts-count
> solution.
>
> If you check the input current, or the current in the freewheeling
> diode (probably not included inside the digital isolator, by the way),
> you'll see diode current spikes occurring when it turns off and the
> switch turns on. The amplitude of these spikes will vary with diode
> type and nmos switching speed (slower speeds are generated if a
> series gate resistor is present on M1).
>
> These spikes are not simulation artifacts, they are modeling attempts
> to simulate schottky capacitance or rectifier reverse recovery.
> 200V schottkeys are rare beasts, but there are fast recovery
> rectifiers offered in the standard LTspice distribution selection
> lists.
>
> The Bourns data sheet gives a flux density calculation in gauss
> using K * L * dI with a frequency-dependent core loss chart
> specific to the SRR1210 series.
>
> In a ripple-regulated circuit dI will vary with frequency - in
> the sim it's between 200 and 400mAppk.
>
>
> In a regulated circuit, the peak to peak flux swing in the choke is
> determined by Bppk = V * t / ( N * A)
> where
> Bppk = peak to peak flux density (Teslas)
> V = Vout + Vdfreewheel (volts)
> t = Tfreewheel (seconds)
> N = number of turns on the choke
> A = xsectional area of choke
>
> If you've got a table for the choke's material, you can work
> out core loss (W/m^3 - mW/cm^3) and apply that to the volume
> of the core geometry being used.
>
> Voltage is present in that equation. For peak or surge, it's
> either saturation or turn/terminal breakdown limited. Some
> core structures, when impressed with low impedance surges,
> will try to turn themselves inside out, in the attempt to
> force changes in the magnetic length/area ratio.
>
> Lighting ballast design for the domestic market is not the easiest
> road to fame and fortune.
>
> Considering the efficiencies of LED sources and the dominance
> of standard hardware formats, it turns into a marketing exercise.
>
> RL

Thanks for taking a look. In the end this was never going to be more
than an academic exercise. I don't even intend to attempt to build one.
To be remotely viable commercially, most of the electronics would have
to be bundled into an IC, and I don't see that happening.

While eliminating the electrolytic capacitor could benefit the consumer
(assuming the high voltages don't produce other reductions in life),
it's of little interest to manufacturers - even those making the
hypothetical IC.

Sylvia.

On Tue, 8 Mar 2022 09:41:51 +1100, Sylvia Else <sylvia@email.invalid>
wrote:

>On 08-Mar-22 1:02 am, legg wrote:
>> On Mon, 7 Mar 2022 19:03:14 +1100, Sylvia Else <sylvia@email.invalid>
>> wrote:
>>
>>> On 06-Mar-22 2:12 pm, jlarkin@highlandsniptechnology.com wrote:
>>>> On Sun, 6 Mar 2022 12:21:09 +1100, Sylvia Else <sylvia@email.invalid>
>>>> wrote:
>>>>
>>>>> On 06-Mar-22 10:59 am, jlarkin@highlandsniptechnology.com wrote:
>>>>>> On Sun, 6 Mar 2022 10:23:29 +1100, Sylvia Else <sylvia@email.invalid>
>>>>>> wrote:
>>>>>>
>>>>>>> I've looked at a number of data sheets, and they never seem to give a
>>>>>>> voltage rating.
>>>>>>>
>>>>>>> Of course, applying any significant DC voltage across an inductor is
>>>>>>> unlikely to have a good outcome, but one can certainly put a significant
>>>>>>> voltage across one for a short period, and it would be nice to know what
>>>>>>> the limits are.
>>>>>>>
>>>>>>> As a random example
>>>>>>>
>>>>>>> https://www.farnell.com/datasheets/1870387.pdf
>>>>>>
>>>>>> Powdered iron can get lossy if you drive it hard. Then it gets hot and
>>>>>> everything gets worse. KoolMu or Sendust has become affordable.
>>>>>>
>>>>>>>
>>>>>>> The obvious concerns here are breakdown of the insulation between the
>>>>>>> wire and the core, and between windings at the two ends where they are
>>>>>>> close together.
>>>>>>>
>>>>>>> Sylvia.
>>>>>>
>>>>>> I think a few of the Coilcraft parts have voltage ratings, but it's
>>>>>> rare. The dual-winding guys, like DRQ127, are probably bifalar and
>>>>>> have more ways to arc.
>>>>>>
>>>>>> I usually test them.
>>>>>>
>>>>>> How much voltage were you considering? That toroid looks pretty good.
>>>>>>
>>>>>> Class D amp?
>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>> No. I was pondering why LED light fittings need to have a large
>>>>> electrolytic capacitor with its limited life.
>>>>>
>>>>> I have a couple of small LEDs illuminating an otherwise frequently pitch
>>>>> black corridor. They're powered through a transformer, bridge rectifier
>>>>> and current limiter, with no capacitors at all. They obviously flicker
>>>>> at 100Hz, but it's not visible.
>>>>>
>>>>> So then I was thinking that one could use a buck converter directly off
>>>>> the rectified, but not filtered, mains, hence the voltage requirement.
>>>>>
>>>>> This has not moved past musings at this point, but I was looking at the
>>>>> voltage specs for inductors, hence my comment.
>>>>>
>>>>> Sylvia.
>>>>
>>>> Lots of LED bulbs have a bridge and a linear IC current limiter but no
>>>> cap. A capless switcher is an interesting idea. The LED could run at
>>>> constant current at a very high duty cycle.
>>>>
>>>> An inductor like you showed would be fine at hundreds of volts. Test
>>>> one to breakdown!
>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>> Seems to work in LTSpice at least:
>>>
>>> The switch is a stand-in for a digital isolator.
>>>
>>> Apart from V6 which is the incoming mains supply, the various voltage
>>> sources would be small amounts of power derived from the rectified
>>> mains. I haven't simulated the fact that this power would not be
>>> available for short periods.
>>>
>> <snip>
>>
>> LTspice IV threw a 'singular matrix node error' here, but only if
>> the Philips models for 2N2222 and 2N3906 were used. NSC models
>> allowed the simulation to run.
>>
>> I'm not sure that you're going to find a 'digital isolator' that's
>> designed for PWM - they're usually pretty slow. You might consider
>> an integrated gate driver + discrete nmos as a lower-parts-count
>> solution.
>>
>> If you check the input current, or the current in the freewheeling
>> diode (probably not included inside the digital isolator, by the way),
>> you'll see diode current spikes occurring when it turns off and the
>> switch turns on. The amplitude of these spikes will vary with diode
>> type and nmos switching speed (slower speeds are generated if a
>> series gate resistor is present on M1).
>>
>> These spikes are not simulation artifacts, they are modeling attempts
>> to simulate schottky capacitance or rectifier reverse recovery.
>> 200V schottkeys are rare beasts, but there are fast recovery
>> rectifiers offered in the standard LTspice distribution selection
>> lists.
>>
>> The Bourns data sheet gives a flux density calculation in gauss
>> using K * L * dI with a frequency-dependent core loss chart
>> specific to the SRR1210 series.
>>
>> In a ripple-regulated circuit dI will vary with frequency - in
>> the sim it's between 200 and 400mAppk.
>>
>>
>> In a regulated circuit, the peak to peak flux swing in the choke is
>> determined by Bppk = V * t / ( N * A)
>> where
>> Bppk = peak to peak flux density (Teslas)
>> V = Vout + Vdfreewheel (volts)
>> t = Tfreewheel (seconds)
>> N = number of turns on the choke
>> A = xsectional area of choke
>>
>> If you've got a table for the choke's material, you can work
>> out core loss (W/m^3 - mW/cm^3) and apply that to the volume
>> of the core geometry being used.
>>
>> Voltage is present in that equation. For peak or surge, it's
>> either saturation or turn/terminal breakdown limited. Some
>> core structures, when impressed with low impedance surges,
>> will try to turn themselves inside out, in the attempt to
>> force changes in the magnetic length/area ratio.
>>
>> Lighting ballast design for the domestic market is not the easiest
>> road to fame and fortune.
>>
>> Considering the efficiencies of LED sources and the dominance
>> of standard hardware formats, it turns into a marketing exercise.
>>
>> RL
>
>Thanks for taking a look. In the end this was never going to be more
>than an academic exercise. I don't even intend to attempt to build one.
>To be remotely viable commercially, most of the electronics would have
>to be bundled into an IC, and I don't see that happening.
>
>While eliminating the electrolytic capacitor could benefit the consumer
>(assuming the high voltages don't produce other reductions in life),
>it's of little interest to manufacturers - even those making the
>hypothetical IC.
>
>Sylvia.

Well, they wouldn't tell you, if they were, but there ARE application-
specific ICs showing up in SEA - they just don't crow about it, or
have any interest in the North American market.

That flat-topped line current waveform isn't any easier, w/r to
harmonic distortion on the transformer-coupled grid, than the
capacitive rectifier peak, but it is 'loss-reduced'. The linear
LED lamps have a similar profile, when caps are removed.

RL

On Tue, 8 Mar 2022 09:41:51 +1100, Sylvia Else <sylvia@email.invalid>
wrote:

>On 08-Mar-22 1:02 am, legg wrote:
>> On Mon, 7 Mar 2022 19:03:14 +1100, Sylvia Else <sylvia@email.invalid>
>> wrote:
>>
>>> On 06-Mar-22 2:12 pm, jlarkin@highlandsniptechnology.com wrote:
>>>> On Sun, 6 Mar 2022 12:21:09 +1100, Sylvia Else <sylvia@email.invalid>
>>>> wrote:
>>>>
>>>>> On 06-Mar-22 10:59 am, jlarkin@highlandsniptechnology.com wrote:
>>>>>> On Sun, 6 Mar 2022 10:23:29 +1100, Sylvia Else <sylvia@email.invalid>
>>>>>> wrote:
>>>>>>
>>>>>>> I've looked at a number of data sheets, and they never seem to give a
>>>>>>> voltage rating.
>>>>>>>
>>>>>>> Of course, applying any significant DC voltage across an inductor is
>>>>>>> unlikely to have a good outcome, but one can certainly put a significant
>>>>>>> voltage across one for a short period, and it would be nice to know what
>>>>>>> the limits are.
>>>>>>>
>>>>>>> As a random example
>>>>>>>
>>>>>>> https://www.farnell.com/datasheets/1870387.pdf
>>>>>>
>>>>>> Powdered iron can get lossy if you drive it hard. Then it gets hot and
>>>>>> everything gets worse. KoolMu or Sendust has become affordable.
>>>>>>
>>>>>>>
>>>>>>> The obvious concerns here are breakdown of the insulation between the
>>>>>>> wire and the core, and between windings at the two ends where they are
>>>>>>> close together.
>>>>>>>
>>>>>>> Sylvia.
>>>>>>
>>>>>> I think a few of the Coilcraft parts have voltage ratings, but it's
>>>>>> rare. The dual-winding guys, like DRQ127, are probably bifalar and
>>>>>> have more ways to arc.
>>>>>>
>>>>>> I usually test them.
>>>>>>
>>>>>> How much voltage were you considering? That toroid looks pretty good.
>>>>>>
>>>>>> Class D amp?
>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>> No. I was pondering why LED light fittings need to have a large
>>>>> electrolytic capacitor with its limited life.
>>>>>
>>>>> I have a couple of small LEDs illuminating an otherwise frequently pitch
>>>>> black corridor. They're powered through a transformer, bridge rectifier
>>>>> and current limiter, with no capacitors at all. They obviously flicker
>>>>> at 100Hz, but it's not visible.
>>>>>
>>>>> So then I was thinking that one could use a buck converter directly off
>>>>> the rectified, but not filtered, mains, hence the voltage requirement.
>>>>>
>>>>> This has not moved past musings at this point, but I was looking at the
>>>>> voltage specs for inductors, hence my comment.
>>>>>
>>>>> Sylvia.
>>>>
>>>> Lots of LED bulbs have a bridge and a linear IC current limiter but no
>>>> cap. A capless switcher is an interesting idea. The LED could run at
>>>> constant current at a very high duty cycle.
>>>>
>>>> An inductor like you showed would be fine at hundreds of volts. Test
>>>> one to breakdown!
>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>> Seems to work in LTSpice at least:
>>>
>>> The switch is a stand-in for a digital isolator.
>>>
>>> Apart from V6 which is the incoming mains supply, the various voltage
>>> sources would be small amounts of power derived from the rectified
>>> mains. I haven't simulated the fact that this power would not be
>>> available for short periods.
>>>
>> <snip>
>>
>> LTspice IV threw a 'singular matrix node error' here, but only if
>> the Philips models for 2N2222 and 2N3906 were used. NSC models
>> allowed the simulation to run.
>>
>> I'm not sure that you're going to find a 'digital isolator' that's
>> designed for PWM - they're usually pretty slow. You might consider
>> an integrated gate driver + discrete nmos as a lower-parts-count
>> solution.
>>
>> If you check the input current, or the current in the freewheeling
>> diode (probably not included inside the digital isolator, by the way),
>> you'll see diode current spikes occurring when it turns off and the
>> switch turns on. The amplitude of these spikes will vary with diode
>> type and nmos switching speed (slower speeds are generated if a
>> series gate resistor is present on M1).
>>
>> These spikes are not simulation artifacts, they are modeling attempts
>> to simulate schottky capacitance or rectifier reverse recovery.
>> 200V schottkeys are rare beasts, but there are fast recovery
>> rectifiers offered in the standard LTspice distribution selection
>> lists.
>>
>> The Bourns data sheet gives a flux density calculation in gauss
>> using K * L * dI with a frequency-dependent core loss chart
>> specific to the SRR1210 series.
>>
>> In a ripple-regulated circuit dI will vary with frequency - in
>> the sim it's between 200 and 400mAppk.
>>
>>
>> In a regulated circuit, the peak to peak flux swing in the choke is
>> determined by Bppk = V * t / ( N * A)
>> where
>> Bppk = peak to peak flux density (Teslas)
>> V = Vout + Vdfreewheel (volts)
>> t = Tfreewheel (seconds)
>> N = number of turns on the choke
>> A = xsectional area of choke
>>
>> If you've got a table for the choke's material, you can work
>> out core loss (W/m^3 - mW/cm^3) and apply that to the volume
>> of the core geometry being used.
>>
>> Voltage is present in that equation. For peak or surge, it's
>> either saturation or turn/terminal breakdown limited. Some
>> core structures, when impressed with low impedance surges,
>> will try to turn themselves inside out, in the attempt to
>> force changes in the magnetic length/area ratio.
>>
>> Lighting ballast design for the domestic market is not the easiest
>> road to fame and fortune.
>>
>> Considering the efficiencies of LED sources and the dominance
>> of standard hardware formats, it turns into a marketing exercise.
>>
>> RL
>
>Thanks for taking a look. In the end this was never going to be more
>than an academic exercise. I don't even intend to attempt to build one.
>To be remotely viable commercially, most of the electronics would have
>to be bundled into an IC, and I don't see that happening.

The real challenge would be to do it with 12 cents worth of discrete
parts.

--

If a man will begin with certainties, he shall end with doubts,
but if he will be content to begin with doubts he shall end in certainties.
Francis Bacon

On 08-Mar-22 12:11 pm, legg wrote:
> On Tue, 8 Mar 2022 09:41:51 +1100, Sylvia Else <sylvia@email.invalid>
> wrote:
>
>> On 08-Mar-22 1:02 am, legg wrote:
>>> On Mon, 7 Mar 2022 19:03:14 +1100, Sylvia Else <sylvia@email.invalid>
>>> wrote:
>>>
>>>> On 06-Mar-22 2:12 pm, jlarkin@highlandsniptechnology.com wrote:
>>>>> On Sun, 6 Mar 2022 12:21:09 +1100, Sylvia Else <sylvia@email.invalid>
>>>>> wrote:
>>>>>
>>>>>> On 06-Mar-22 10:59 am, jlarkin@highlandsniptechnology.com wrote:
>>>>>>> On Sun, 6 Mar 2022 10:23:29 +1100, Sylvia Else <sylvia@email.invalid>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> I've looked at a number of data sheets, and they never seem to give a
>>>>>>>> voltage rating.
>>>>>>>>
>>>>>>>> Of course, applying any significant DC voltage across an inductor is
>>>>>>>> unlikely to have a good outcome, but one can certainly put a significant
>>>>>>>> voltage across one for a short period, and it would be nice to know what
>>>>>>>> the limits are.
>>>>>>>>
>>>>>>>> As a random example
>>>>>>>>
>>>>>>>> https://www.farnell.com/datasheets/1870387.pdf
>>>>>>>
>>>>>>> Powdered iron can get lossy if you drive it hard. Then it gets hot and
>>>>>>> everything gets worse. KoolMu or Sendust has become affordable.
>>>>>>>
>>>>>>>>
>>>>>>>> The obvious concerns here are breakdown of the insulation between the
>>>>>>>> wire and the core, and between windings at the two ends where they are
>>>>>>>> close together.
>>>>>>>>
>>>>>>>> Sylvia.
>>>>>>>
>>>>>>> I think a few of the Coilcraft parts have voltage ratings, but it's
>>>>>>> rare. The dual-winding guys, like DRQ127, are probably bifalar and
>>>>>>> have more ways to arc.
>>>>>>>
>>>>>>> I usually test them.
>>>>>>>
>>>>>>> How much voltage were you considering? That toroid looks pretty good.
>>>>>>>
>>>>>>> Class D amp?
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>> No. I was pondering why LED light fittings need to have a large
>>>>>> electrolytic capacitor with its limited life.
>>>>>>
>>>>>> I have a couple of small LEDs illuminating an otherwise frequently pitch
>>>>>> black corridor. They're powered through a transformer, bridge rectifier
>>>>>> and current limiter, with no capacitors at all. They obviously flicker
>>>>>> at 100Hz, but it's not visible.
>>>>>>
>>>>>> So then I was thinking that one could use a buck converter directly off
>>>>>> the rectified, but not filtered, mains, hence the voltage requirement.
>>>>>>
>>>>>> This has not moved past musings at this point, but I was looking at the
>>>>>> voltage specs for inductors, hence my comment.
>>>>>>
>>>>>> Sylvia.
>>>>>
>>>>> Lots of LED bulbs have a bridge and a linear IC current limiter but no
>>>>> cap. A capless switcher is an interesting idea. The LED could run at
>>>>> constant current at a very high duty cycle.
>>>>>
>>>>> An inductor like you showed would be fine at hundreds of volts. Test
>>>>> one to breakdown!
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>> Seems to work in LTSpice at least:
>>>>
>>>> The switch is a stand-in for a digital isolator.
>>>>
>>>> Apart from V6 which is the incoming mains supply, the various voltage
>>>> sources would be small amounts of power derived from the rectified
>>>> mains. I haven't simulated the fact that this power would not be
>>>> available for short periods.
>>>>
>>> <snip>
>>>
>>> LTspice IV threw a 'singular matrix node error' here, but only if
>>> the Philips models for 2N2222 and 2N3906 were used. NSC models
>>> allowed the simulation to run.
>>>
>>> I'm not sure that you're going to find a 'digital isolator' that's
>>> designed for PWM - they're usually pretty slow. You might consider
>>> an integrated gate driver + discrete nmos as a lower-parts-count
>>> solution.
>>>
>>> If you check the input current, or the current in the freewheeling
>>> diode (probably not included inside the digital isolator, by the way),
>>> you'll see diode current spikes occurring when it turns off and the
>>> switch turns on. The amplitude of these spikes will vary with diode
>>> type and nmos switching speed (slower speeds are generated if a
>>> series gate resistor is present on M1).
>>>
>>> These spikes are not simulation artifacts, they are modeling attempts
>>> to simulate schottky capacitance or rectifier reverse recovery.
>>> 200V schottkeys are rare beasts, but there are fast recovery
>>> rectifiers offered in the standard LTspice distribution selection
>>> lists.
>>>
>>> The Bourns data sheet gives a flux density calculation in gauss
>>> using K * L * dI with a frequency-dependent core loss chart
>>> specific to the SRR1210 series.
>>>
>>> In a ripple-regulated circuit dI will vary with frequency - in
>>> the sim it's between 200 and 400mAppk.
>>>
>>>
>>> In a regulated circuit, the peak to peak flux swing in the choke is
>>> determined by Bppk = V * t / ( N * A)
>>> where
>>> Bppk = peak to peak flux density (Teslas)
>>> V = Vout + Vdfreewheel (volts)
>>> t = Tfreewheel (seconds)
>>> N = number of turns on the choke
>>> A = xsectional area of choke
>>>
>>> If you've got a table for the choke's material, you can work
>>> out core loss (W/m^3 - mW/cm^3) and apply that to the volume
>>> of the core geometry being used.
>>>
>>> Voltage is present in that equation. For peak or surge, it's
>>> either saturation or turn/terminal breakdown limited. Some
>>> core structures, when impressed with low impedance surges,
>>> will try to turn themselves inside out, in the attempt to
>>> force changes in the magnetic length/area ratio.
>>>
>>> Lighting ballast design for the domestic market is not the easiest
>>> road to fame and fortune.
>>>
>>> Considering the efficiencies of LED sources and the dominance
>>> of standard hardware formats, it turns into a marketing exercise.
>>>
>>> RL
>>
>> Thanks for taking a look. In the end this was never going to be more
>> than an academic exercise. I don't even intend to attempt to build one.
>> To be remotely viable commercially, most of the electronics would have
>> to be bundled into an IC, and I don't see that happening.
>>
>> While eliminating the electrolytic capacitor could benefit the consumer
>> (assuming the high voltages don't produce other reductions in life),
>> it's of little interest to manufacturers - even those making the
>> hypothetical IC.
>>
>> Sylvia.
>
> Well, they wouldn't tell you, if they were, but there ARE application-
> specific ICs showing up in SEA - they just don't crow about it, or
> have any interest in the North American market.
>
> That flat-topped line current waveform isn't any easier, w/r to
> harmonic distortion on the transformer-coupled grid, than the
> capacitive rectifier peak, but it is 'loss-reduced'. The linear
> LED lamps have a similar profile, when caps are removed.
>
> RL

My own home is illuminated almost entirely by low voltage lamps.
Probably someone in the past fell for the notion that low voltage means
low power consumption.

On a sunny day (Mon, 07 Mar 2022 20:11:59 -0500) it happened legg
<legg@nospam.magma.ca> wrote in <uuad2hpo887r2jdban5a8mghujpq5md96t@4ax.com>:

>That flat-topped line current waveform isn't any easier, w/r to
>harmonic distortion on the transformer-coupled grid, than the
>capacitive rectifier peak, but it is 'loss-reduced'. The linear
>LED lamps have a similar profile, when caps are removed.
>
>RL

The Chinese LED lamps from ebay I have use a much smaller electrolytic
capacitor that you could probably leave out:
circuit:
http://panteltje.com/pub/LED_light_circuit_diagram_IMG_6925.JPG

A look inside :
http://panteltje.com/pub/LED_light_fix_IMG_6918.JPG
The current is limited by the 1 uF cap in series with the AC.
The voltage on the eletrolytics is limited by the LEDs working as zeners.

simple...
Some LEDs died
Transients on the mains commom here.

On Mon, 07 Mar 2022 17:20:22 -0800, John Larkin
<jlarkin@highland_atwork_technology.com> wrote:

>On Tue, 8 Mar 2022 09:41:51 +1100, Sylvia Else <sylvia@email.invalid>
>wrote:
>
>>On 08-Mar-22 1:02 am, legg wrote:
>>> On Mon, 7 Mar 2022 19:03:14 +1100, Sylvia Else <sylvia@email.invalid>
>>> wrote:
>>>
>>>> On 06-Mar-22 2:12 pm, jlarkin@highlandsniptechnology.com wrote:
>>>>> On Sun, 6 Mar 2022 12:21:09 +1100, Sylvia Else <sylvia@email.invalid>
>>>>> wrote:
>>>>>
>>>>>> On 06-Mar-22 10:59 am, jlarkin@highlandsniptechnology.com wrote:
>>>>>>> On Sun, 6 Mar 2022 10:23:29 +1100, Sylvia Else <sylvia@email.invalid>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> I've looked at a number of data sheets, and they never seem to give a
>>>>>>>> voltage rating.
>>>>>>>>
>>>>>>>> Of course, applying any significant DC voltage across an inductor is
>>>>>>>> unlikely to have a good outcome, but one can certainly put a significant
>>>>>>>> voltage across one for a short period, and it would be nice to know what
>>>>>>>> the limits are.
>>>>>>>>
>>>>>>>> As a random example
>>>>>>>>
>>>>>>>> https://www.farnell.com/datasheets/1870387.pdf
>>>>>>>
>>>>>>> Powdered iron can get lossy if you drive it hard. Then it gets hot and
>>>>>>> everything gets worse. KoolMu or Sendust has become affordable.
>>>>>>>
>>>>>>>>
>>>>>>>> The obvious concerns here are breakdown of the insulation between the
>>>>>>>> wire and the core, and between windings at the two ends where they are
>>>>>>>> close together.
>>>>>>>>
>>>>>>>> Sylvia.
>>>>>>>
>>>>>>> I think a few of the Coilcraft parts have voltage ratings, but it's
>>>>>>> rare. The dual-winding guys, like DRQ127, are probably bifalar and
>>>>>>> have more ways to arc.
>>>>>>>
>>>>>>> I usually test them.
>>>>>>>
>>>>>>> How much voltage were you considering? That toroid looks pretty good.
>>>>>>>
>>>>>>> Class D amp?
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>> No. I was pondering why LED light fittings need to have a large
>>>>>> electrolytic capacitor with its limited life.
>>>>>>
>>>>>> I have a couple of small LEDs illuminating an otherwise frequently pitch
>>>>>> black corridor. They're powered through a transformer, bridge rectifier
>>>>>> and current limiter, with no capacitors at all. They obviously flicker
>>>>>> at 100Hz, but it's not visible.
>>>>>>
>>>>>> So then I was thinking that one could use a buck converter directly off
>>>>>> the rectified, but not filtered, mains, hence the voltage requirement.
>>>>>>
>>>>>> This has not moved past musings at this point, but I was looking at the
>>>>>> voltage specs for inductors, hence my comment.
>>>>>>
>>>>>> Sylvia.
>>>>>
>>>>> Lots of LED bulbs have a bridge and a linear IC current limiter but no
>>>>> cap. A capless switcher is an interesting idea. The LED could run at
>>>>> constant current at a very high duty cycle.
>>>>>
>>>>> An inductor like you showed would be fine at hundreds of volts. Test
>>>>> one to breakdown!
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>> Seems to work in LTSpice at least:
>>>>
>>>> The switch is a stand-in for a digital isolator.
>>>>
>>>> Apart from V6 which is the incoming mains supply, the various voltage
>>>> sources would be small amounts of power derived from the rectified
>>>> mains. I haven't simulated the fact that this power would not be
>>>> available for short periods.
>>>>
>>> <snip>
>>>
>>> LTspice IV threw a 'singular matrix node error' here, but only if
>>> the Philips models for 2N2222 and 2N3906 were used. NSC models
>>> allowed the simulation to run.
>>>
>>> I'm not sure that you're going to find a 'digital isolator' that's
>>> designed for PWM - they're usually pretty slow. You might consider
>>> an integrated gate driver + discrete nmos as a lower-parts-count
>>> solution.
>>>
>>> If you check the input current, or the current in the freewheeling
>>> diode (probably not included inside the digital isolator, by the way),
>>> you'll see diode current spikes occurring when it turns off and the
>>> switch turns on. The amplitude of these spikes will vary with diode
>>> type and nmos switching speed (slower speeds are generated if a
>>> series gate resistor is present on M1).
>>>
>>> These spikes are not simulation artifacts, they are modeling attempts
>>> to simulate schottky capacitance or rectifier reverse recovery.
>>> 200V schottkeys are rare beasts, but there are fast recovery
>>> rectifiers offered in the standard LTspice distribution selection
>>> lists.
>>>
>>> The Bourns data sheet gives a flux density calculation in gauss
>>> using K * L * dI with a frequency-dependent core loss chart
>>> specific to the SRR1210 series.
>>>
>>> In a ripple-regulated circuit dI will vary with frequency - in
>>> the sim it's between 200 and 400mAppk.
>>>
>>>
>>> In a regulated circuit, the peak to peak flux swing in the choke is
>>> determined by Bppk = V * t / ( N * A)
>>> where
>>> Bppk = peak to peak flux density (Teslas)
>>> V = Vout + Vdfreewheel (volts)
>>> t = Tfreewheel (seconds)
>>> N = number of turns on the choke
>>> A = xsectional area of choke
>>>
>>> If you've got a table for the choke's material, you can work
>>> out core loss (W/m^3 - mW/cm^3) and apply that to the volume
>>> of the core geometry being used.
>>>
>>> Voltage is present in that equation. For peak or surge, it's
>>> either saturation or turn/terminal breakdown limited. Some
>>> core structures, when impressed with low impedance surges,
>>> will try to turn themselves inside out, in the attempt to
>>> force changes in the magnetic length/area ratio.
>>>
>>> Lighting ballast design for the domestic market is not the easiest
>>> road to fame and fortune.
>>>
>>> Considering the efficiencies of LED sources and the dominance
>>> of standard hardware formats, it turns into a marketing exercise.
>>>
>>> RL
>>
>>Thanks for taking a look. In the end this was never going to be more
>>than an academic exercise. I don't even intend to attempt to build one.
>>To be remotely viable commercially, most of the electronics would have
>>to be bundled into an IC, and I don't see that happening.
>
>The real challenge would be to do it with 12 cents worth of discrete
>parts.

You might be surprised. I recall being totally demoralized by an
0.08 transformer quote in 2008. If you stick to the right commodity
materials, it's a completely different market, or perhaps the
demoralization was intentional. I'm being paranoid here.

I visualize being paid to use parts, under corporate, tax or political
circumstances, that I'd really rather not consider . . .

RL

On 09-Mar-22 3:07 am, Skittles wrote:
> On Sun, 6 Mar 2022 10:23:29 +1100, Sylvia Else <sylvia@email.invalid>
> wrote:
>
>> I've looked at a number of data sheets, and they never seem to give a
>> voltage rating.
>>
>> Of course, applying any significant DC voltage across an inductor is
>> unlikely to have a good outcome, but one can certainly put a significant
>> voltage across one for a short period, and it would be nice to know what
>> the limits are.
>>
>> As a random example
>>
>> https://www.farnell.com/datasheets/1870387.pdf
>>
>> The obvious concerns here are breakdown of the insulation between the
>> wire and the core, and between windings at the two ends where they are
>> close together.
>>
>> Sylvia.
>
>
> If your inductor has a decent Q value (low resistance) then the DC
> voltage drop across the inductor is almost zero. Should be no DC
> arcing within the inductor itself.
>
> Skittles

Yes. The issue related to short pulses.

Sylvia.