On 11/29/2014 12:02 AM, rickman wrote:
On 11/28/2014 11:46 PM, Jerry Stuckle wrote:
On 11/28/2014 11:16 PM, rickman wrote:
On 11/28/2014 11:01 PM, Jerry Stuckle wrote:
On 11/28/2014 10:39 PM, rickman wrote:
On 11/28/2014 8:52 PM, Jerry Stuckle wrote:
On 11/28/2014 7:05 PM, rickman wrote:
On 11/28/2014 6:16 PM, Jerry Stuckle wrote:
On 11/28/2014 5:24 PM, wrote:
In rec.radio.amateur.boatanchors Jerry Stuckle
wrote:
On 11/28/2014 4:11 PM, wrote:
In rec.radio.amateur.boatanchors Michael Black
wrote:
On Fri, 28 Nov 2014, wrote:

In rec.radio.amateur.boatanchors gareth
wrote:
These LED replacements for 240V mains lamps; if one were to
open them, would one find a high voltage regulator
suitable for
some of our valve experiments and repairs?

As the regulators are potted in and would be difficult to
remove,
and
since LED's run on voltages on the order of 2-3 volts, no.

How many 3 volt valves can you name?

I think that point was that if a regulator was used to drop the
line
voltage to those 3volts, it could handle high voltage
input. The
probably
false assumption is that the regulator would be variable from
some
very
high output voltage to some very low output voltage, so one
could
use it
for tubes by making that adjustment.

Given that manufacturers want the least cost in a product,
and the
regulator in a light bulb would have no need for a variable
regulator,
and that these things are made in the millions, it would be
extremely
silly to assume that the regulator is anything other than a
fixed
regulator for LED's and is designed to handle the load of some
fixed
number of LED's.


Once again, incorrect. Have you ever heard of "dimmable LED
bulbs"?
How do you dim without an adjustable regulator?

You do realize that a dimmable light bulb is dimmed by
changeing the
supply voltage and not by anything else connected to the bulb?


For incandescent, yes. But not for LED bulbs. If that were the
case,
why would some LED bulbs be dimmable and others not?

To specifically answer your question, you design a regulator who's
output
is some precentage of the raw input as opposed to a regulator
who's
output is always equal to some reference voltage.


Again, it all depends.

And to be yet more specific, since LED brightness is
proportional to
current and resistors would waste power, the regulator would be a
current regulator with an average current output proportional
to the
raw input voltage.


Then why can't you use standard incandescent dimmers with LED
bulbs?

A lot of IC regulators can't handle high voltage. If nothing
else, nobody
saw the need, it was the solid state age. So dissipation
issues
aside,
most regulators expect at most a relatively low DC voltage
input.

True for IC regulators. Hoever high voltage transistors exist
these
days which makes designing a high voltage regulator pretty
trivial.


Sure. But how do you handle the current requirements without
some
kind
of transformer?

Well, assuming you want some voltage greater than the wall plug
maximum,
the need for a transformer is pretty much a given unless some
sort of
voltage multiplying rectifier is sufficient for the need, which is
where the current requirement becomes relevant.

However, the subject was high voltage regulators, not where
does the
raw high voltage come from.


And where do you get the current necessary to supply the LEDs in
the
bulbs? A typical LED required around 3V (usually 2.7V to 3.3V,
depending on the LED)? A 9 watt LED would require 3 amps of
current.
Or, if the LEDs were in series, something less. But without a
transformer, the current would still exceed that of an incandescent
bulb.

You obviously are unfamiliar with the structure of LED bulbs.

You two are both speculating and have limited information to base
either
of your opinions on. Jim says,


Sorry, but lighting control has been my job for much of the last 11
years. I am considered an expert in it by many of my peers and teach
courses on it. We also install many different lighting systems,
including LED.

You do realize that a dimmable light bulb is dimmed by changeing
the
supply voltage and not by anything else connected to the bulb?

which is not correct in that most dimmers work by reducing the phase
angle of the applied AC or to reduce noise some simply don't turn
on for
entire half cycles.

Jerry says,

Then why can't you use standard incandescent dimmers with LED
bulbs?

Which is wrong because you can use "standard" dimmers, but the LED
bulb
has to be designed for it.


Which they aren't for many reasons that I won't get into here.

Really? So the standard dimmers in my home can't work with the
dimmable
LED bulbs they are connected to and seem to control just fine?


Try reading a little...

http://www.ledsmagazine.com/articles...-magazine.html






This article is sorely lacking in facts. Notice the title: "LED
lighting must work with legacy dimming technologies".

There are a number of problems with dimmable LED bulbs and the
standard
triac dimmer. See above. And I suggest you read more reliable
information. LED bulb manufacturer's information is a better start.

How do you explain the several LED bulbs I have working on standard
dimmers in my home?


Rick,

How do you explain the manufacturer of dimmers says standard dimmers
cannot be used reliably?

I don't see where they said that. They are only talking about their own
products.


"No, unlike incandescent bulbs that work with almost any dimmer, LED and
CFL bulbs perform differently depending on the dimmer you install. You
will need to select a dimmer designed specifically for dimmable LED/CFL
bulbs."

That seems to indicate they won't work reliably.

And yet I have units in my home that work...reliably. Rather than cite
dimmer companies, why not cite the bulb companies? That is what we are
discussing.


But since you want the details, here is a start. There are a number of
problems with standard incandescent dimmers. Since they cut off the
initial phase of the positive and negative phases, when they start
conducting there is a large surge of power. This surge causes
additional heat buildup in a switching power supply and can cause
premature failure of the bulb and/or dimmer.

Dealing with this heat would be part of the design requirements for a
"dimmable" LED bulb, no?


Not when used with a non-LED bulb dimmer.

Simple LED dimmers use MOSFETs to trim the trailing part of the
waveform, eliminating the surge.

You can argue design all you want. But the fact is this surge current
creates heat - which wastes energy, making the bulb less efficient. And
adding what is necessary to handle the extra current would add cost,
raising the price. Both make the product less competitive.

I never said anything about "wasted" energy or competitiveness. I said
LED bulbs can are are designed that work with existing dimmers.


If you look at travel adapters for running U.S. devices on European
voltages, you'll find two different types - electronic switching and
standard transformer. You will notice the electronic switching
supplies
are higher powered have cautions not to use them with electronic loads
such as radios and TV's. This is for the same reason as dimmers on
LEDs
- the dimmer does not put out a clean waveform.

Transformer-based travel adapters have no such limitation because they
put out a clean signal, but have lower power ratings.

There are other problems, also. Conventional dimmers having a minimum
load (minimum current flowing through triacs). If the minimum load to
maintain conduction is 10W, a 15W LED will only dim to 2/3 power before
turning off.

Dimmable LED bulbs are also very sensitive to voltage fluctuations, and
can flicker with variations in the line voltage. This is especially
true when operating near that cutoff voltage noted above.

Again, this is a design issue and one that is present even when not
being dimmed.


No, they do not flicker at full power. They may dim a bit, but they
will not flicker. LED dimmers provide a stable voltage to the bulb,
eliminating flicker.

There is nothing inherent in a phase angle dimmer that causes flickering
in a properly designed bulb. A few uF capacitance takes care of that.


Also, since LED's respond immediately to current changes (unlike
incandescent, which have a high thermal inertia), there is a tendency
for them to flicker when the wrong dimmer is used. Sure, it's 120 hz
flicker - but some people are sensitive to it and can suffer headaches.
Worst case, but fortunately very rare, the flash can cause epileptic
seizures those sensitive to it.

I have seen no information that 120 Hz flicker is in any way noticeable
or that anyone is sensitive to it. Monitors have flickered at much
lower rates for a very long time. Plus... again, this is an issue
without dimmers.


You haven't been reading the medical engineering data. It is not so
much an issue without dimmers because there is a slight inertial effect
in the switching supply (capacitors) such that the bulb doesn't dim to
0, even at zero crossing. However, when you start cutting the AC cycle
going to the bulb, the capacitors totally discharge and you get a
relatively long period when the LEDs are completely black.

Unless you add a bit more capacitance... again a bulb design issue.


Which the non-dimmable bulbs have.


Monitors are not a problem because they work completely differently.
First of all, the original CRTs had a phosphor, which had a certain
amount of persistence. Newer LCD monitors (even "LED" monitors are LCD
monitors, just with an LED backlight) do not turn pixels on and off at a
scan rate.

Lol. Monitors do flicker and have always flickered. At 60 Hz most
monitors bother me a lot. At 80 Hz not at all. I don't know anyone or
have read anything that says 120 Hz is not sufficient to preclude the
perception of flicker.


Yes, CRTs flicker. They do not go out all together. And there is
significant medical evidence that some people are susceptible to the
on/off flicker at at 120 Hz. That's why companies have come out with
phase width dimmers which operate at higher frequencies, such as 480 hz.

If there weren't a need and a market for them, the manufacturers
wouldn't spend the time and money developing the product.


These are some of the most serious problems with using conventional
dimmers with LED bulbs. It's also why manufacturers spend a lot of
money developing special dimmers for LED bulbs.

I would also recommend you check other manufacturer's of LED bulb
dimmers. You will find they all have the same cautions. But since
these pages are intended for consumers, they obviously leave out the
technical details. Those are available to dealers, though, either
through dealer-only pages or dealer support.

And yet, I have dimmers that work...


See above - and check other manufactures of LED dimmers, also. They all
say the same thing. Argue with them, not me.

Ok, I guess we are done then.


I suggest you check your facts. And get your information from reliable
resources.

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