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| From | "Don" <g@crcomp.net> |
|---|---|
| Newsgroups | sci.electronics.design |
| Subject | Re: CoB LED filament analysis |
| Date | 2026-04-21 21:05 +0000 |
| Organization | A noiseless patient Spider |
| Message-ID | <20260421c@crcomp.net> (permalink) |
| References | (1 earlier) <20260421a@crcomp.net> <3c6fuk16nn9tfhj24q3ulue347ab93jvh8@4ax.com> <on6fukd6chfua8nm2puqkdc6llb2jbatub@4ax.com> <20260421b@crcomp.net> <10s8dkd$1mbf8$1@dont-email.me> |
Bill Sloman <bill.sloman@ieee.org> wrote:
> On 22/04/2026 2:55 am, Don wrote:
>> john larkin wrote:
>>> john larkin wrote:
>>>> Don wrote:
>>>>> Don wrote:
>
> <snip>
>
>>> No, it lights up with DC, so there's no series cap.
>>
>> ELI the ICE man. The trace of the current curve clearly leads the
>> voltage trace, so the filament must present a capacitive load.
>
> Seems unlikely. It's more likely bad triggering from a
> not-all-that-closely related waveform.
>
>> A silicon device that presents a capacitive load is different from
>> a series capacitor:
>>
>> COB LEDs present capacitive loads through parasitic capacitances
>> inherent to their densely packed chip-on-board structure. These
>> capacitances arise between closely spaced LED dies, bonding
>> wires, and the substrate, affecting driver circuits during
>> switching.
>
> The internal capacitance won't be anything like big enough to show up at
> mains frequency
>
> The likeliest explanation is a bunch of LEDs connected in series with a
> current limiting resistor between each LED. You'd put in four mains
> rated diodes to rectify the current going through the LED/resistor
> string as the applied voltage switched direction.
>
> Close to zero and 180 degrees the mains voltage isn't high enough to
> push any current through the LEDs, but they will start turning on at
> about 20 degrees, and progressively more of the voltage will get soaked
> up by the resistors until the voltage peaks at 90 degrees/270 degrees.
>
> The LEDs and the resistors will heat up a bit during each half cycle -
> more in the middle of the string than at the ends, and that will make
> the current lumpier than you'd expect from a pure sine wave.
>
> It won't make much difference to the resistors but LED forward voltage
> drop is a function of both current and the die temperature, and as the
> junction gets hotter the forward voltage drops by about 2mV/C
>
> The LED/resistor load also going to make current less sinusoidal than
> the mains supplier would like.
The power factor of cheap COB LED filament can drop to as low as 0.55
leading. [1] A power factor of 0.55 corresponds to a phase angle of
about 56.6 degrees, since PF=cos(θ) and θ=cos−1(0.55).
Looking at the current curves from a different perspective, perhaps
peak polarities are opposite. And a narrow negative peak current only
occurs near the tops of positive peak voltage. This roughly corresponds
to Oscillogram 2. [2]
Note.
[1] <https://blog.1000bulbs.com/home/power-factor-explained>
[2] <https://shuttlelighting.com/the-electrical-and-dimming-behaviour-of-led-filament-lamps/>
Danke,
--
73, Don, WD7Q veritas _|_
liberabit |
https://www.qsl.net/wd7q vos |
Back to sci.electronics.design | Previous | Next — Previous in thread | Next in thread | Find similar
CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-12 05:34 +0000
Re: CoB LED filament analysis JM <sunaecoNoChoppedPork@gmail.com> - 2026-04-12 10:45 +0100
Re: CoB LED filament analysis JM <sunaecoNoChoppedPork@gmail.com> - 2026-04-12 10:48 +0100
Re: CoB LED filament analysis JM <sunaecoNoChoppedPork@gmail.com> - 2026-04-12 10:50 +0100
Re: CoB LED filament analysis JM <sunaecoNoChoppedPork@gmail.com> - 2026-04-12 12:03 +0100
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-12 04:44 -0700
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-12 04:19 -0700
Re: CoB LED filament analysis piglet <erichpwagner@hotmail.com> - 2026-04-13 07:40 +0000
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-13 01:46 -0700
Re: CoB LED filament analysis piglet <erichpwagner@hotmail.com> - 2026-04-13 11:40 +0000
Re: CoB LED filament analysis JM <sunaecoNoChoppedPork@gmail.com> - 2026-04-13 14:31 +0100
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-13 06:59 -0700
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-14 12:25 +0000
Re: CoB LED filament analysis JM <sunaecoNoChoppedPork@gmail.com> - 2026-04-14 14:04 +0100
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-14 08:21 -0700
Re: CoB LED filament analysis Bill Sloman <bill.sloman@ieee.org> - 2026-04-15 02:48 +1000
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-14 11:14 -0700
Re: CoB LED filament analysis piglet <erichpwagner@hotmail.com> - 2026-04-14 19:25 +0100
Re: CoB LED filament analysis JM <sunaecoNoChoppedPork@gmail.com> - 2026-04-14 19:43 +0100
Re: CoB LED filament analysis piglet <erichpwagner@hotmail.com> - 2026-04-14 20:19 +0000
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-14 12:54 -0700
Re: CoB LED filament analysis JM <sunaecoNoChoppedPork@gmail.com> - 2026-04-14 19:42 +0100
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-14 12:57 -0700
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-14 13:02 -0700
Re: CoB LED filament analysis piglet <erichpwagner@hotmail.com> - 2026-04-14 21:29 +0100
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-14 19:10 -0700
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-15 11:36 +0000
Re: CoB LED filament analysis piglet <erichpwagner@hotmail.com> - 2026-04-15 12:35 +0000
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-21 14:39 +0000
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-21 08:41 -0700
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-21 08:54 -0700
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-21 16:55 +0000
Re: CoB LED filament analysis Bill Sloman <bill.sloman@ieee.org> - 2026-04-22 03:54 +1000
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-21 21:05 +0000
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-21 17:03 -0700
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-21 12:26 -0700
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-22 01:44 +0000
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-21 19:16 -0700
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-24 13:37 +0000
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-24 07:55 -0700
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-24 08:04 -0700
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-24 16:43 +0000
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-24 20:15 +0000
Re: CoB LED filament analysis Bill Sloman <bill.sloman@ieee.org> - 2026-04-26 03:45 +1000
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-25 11:14 -0700
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-25 22:56 +0000
Re: CoB LED filament analysis ehsjr <ehsjr@verizon.net> - 2026-04-25 21:33 -0400
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-26 02:18 +0000
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-25 20:08 -0700
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-26 04:44 +0000
Re: CoB LED filament analysis Arie de Muijnck <noreply@ademu.nl> - 2026-04-26 13:03 +0200
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-26 11:35 +0000
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-26 11:43 +0000
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-26 16:44 +0000
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-26 10:17 -0700
Re: CoB LED filament analysis Arie de Muijnck <noreply@ademu.nl> - 2026-04-26 19:58 +0200
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-26 19:22 +0000
Re: CoB LED filament analysis Jeroen Belleman <jeroen@nospam.please> - 2026-04-26 20:30 +0200
Re: CoB LED filament analysis JM <sunaecoNoChoppedPork@gmail.com> - 2026-04-26 18:24 +0100
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-26 17:52 +0000
Re: CoB LED filament analysis piglet <erichpwagner@hotmail.com> - 2026-04-26 19:17 +0000
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-25 20:10 -0700
Re: CoB LED filament analysis Jeroen Belleman <jeroen@nospam.please> - 2026-04-24 22:23 +0200
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-24 15:42 -0700
Re: CoB LED filament analysis Jeroen Belleman <jeroen@nospam.please> - 2026-04-25 10:53 +0200
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-26 12:05 -0700
Re: CoB LED filament analysis piglet <erichpwagner@hotmail.com> - 2026-04-26 19:20 +0000
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-27 12:49 -0700
Re: CoB LED filament analysis Bill Sloman <bill.sloman@ieee.org> - 2026-04-27 17:04 +1000
Re: CoB LED filament analysis Jeroen Belleman <jeroen@nospam.please> - 2026-04-27 10:59 +0200
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-27 08:11 -0700
Re: CoB LED filament analysis Bill Sloman <bill.sloman@ieee.org> - 2026-04-28 01:51 +1000
Re: CoB LED filament analysis Jeroen Belleman <jeroen@nospam.please> - 2026-04-27 21:40 +0200
Re: CoB LED filament analysis JM <sunaecoNoChoppedPork@gmail.com> - 2026-04-22 16:36 +0100
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-22 17:10 +0000
Re: CoB LED filament analysis JM <sunaecoNoChoppedPork@gmail.com> - 2026-04-22 18:17 +0100
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-22 17:31 +0000
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-22 18:14 +0000
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-22 11:23 -0700
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-22 18:43 +0000
Re: CoB LED filament analysis Jeroen Belleman <jeroen@nospam.please> - 2026-04-22 23:50 +0200
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-22 11:24 -0700
Re: CoB LED filament analysis Bill Sloman <bill.sloman@ieee.org> - 2026-04-23 17:22 +1000
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-23 07:58 -0700
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-23 17:15 +0000
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-23 21:26 +0000
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-24 02:53 +0000
Re: CoB LED filament analysis John R Walliker <jrwalliker@gmail.com> - 2026-04-24 18:19 +0100
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-24 10:39 -0700
Re: CoB LED filament analysis John R Walliker <jrwalliker@gmail.com> - 2026-04-24 21:39 +0100
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-24 15:19 -0700
Re: CoB LED filament analysis Bill Sloman <bill.sloman@ieee.org> - 2026-04-25 15:23 +1000
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-24 17:45 +0000
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-24 11:12 -0700
Re: CoB LED filament analysis Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2026-04-24 18:30 +0000
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-24 11:42 -0700
Re: CoB LED filament analysis Bill Sloman <bill.sloman@ieee.org> - 2026-04-25 15:49 +1000
Re: CoB LED filament analysis Bill Sloman <bill.sloman@ieee.org> - 2026-04-25 15:47 +1000
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