120v LED bulbs -- innards

o get a definitive answer on what is REALLY going on inside a typical 120v = LED bulb.

of leds? (and 60hz flicker isn't noticed?)

ve?

s. Certainly there aren't sophisticated drivers in a lamp (maybe just some = higher priced ones?)

try to search google images for: circuit LED bulb

bye delo

try to search google images for: circuit LED bulb

bye delo

to get a definitive answer on what is REALLY going on inside a typical 120= v LED bulb.

k of leds? (and 60hz flicker isn't noticed?)

bove?

ers. Certainly there aren't sophisticated drivers in a lamp (maybe just som= e higher priced ones?)

It probably depends on the manufacturer. The one I got has a transformer and rectifier. Look like a full regulator.

a definitive answer on what is REALLY going on inside a typical 120v LED bulb.

leds? (and 60hz flicker isn't noticed?)

Certainly there aren't sophisticated drivers in a lamp (maybe just some higher priced ones?)

This one:

is a 1uF polyester cap (not mains rated BTW), tiny bridge rectifier, 30 diodes in series and nothing else.

to get a definitive answer on what is REALLY going on inside a typical 120= v LED bulb.

k of leds? (and 60hz flicker isn't noticed?)

bove?

ers. Certainly there aren't sophisticated drivers in a lamp (maybe just som= e higher priced ones?)

If 1 out of 30 failed, ...

I should have mentioned also -- the LED bulbs that are trying to replace conventional medium base bulbs I'm particularly interested in. Popular LED replacements for standard 40w, 60w etc.

conventional medium base bulbs I'm particularly interested in. Popular LED replacements for standard 40w, 60w etc.

B22 is the light bulb standard - at least in OZ. You only asked what they have inside which is pretty irrelevant to what kind of base it has.

This one would easily replace a 40W and perhaps even a 60W. I think the white of the light fools the brain into thinking it is much brighter - in any case it is easy to read under. I think it also comes in ES and if not there is an adapter.

get a definitive answer on what is REALLY going on inside a typical 120v LED bulb.

leds? (and 60hz flicker isn't noticed?)

Certainly there aren't sophisticated drivers in a lamp (maybe just some higher priced ones?)

It's better to have a resistor in series too, so that line spikes don't push a huge amount of current into the LEDs.

John

get a definitive answer on what is REALLY going on inside a typical 120v LED bulb.

leds? (and 60hz flicker isn't noticed?)

Certainly there aren't sophisticated drivers in a lamp (maybe just some higher priced ones?)

I'm fairly sure it didn't. I'll pull the one out of the laundry and check....

Now I have to fix the laundry light fitting.

But no, there is no resistor in series. The one you can see is 560k and in parallel with the 1uF (in the photo it is not the original cap)

"mkr5000"

The schems are never published.

... Phil

Well, this is going to be a really crappy light. it will have a lot of flicker as I assume it generates either 100 or 120 short pulses a second. The better lamps have a switching power supply set up for constant current, and maybe even a PFC circuit that maintains power to the converter through most of the mains cycle. So, it would give constant brightness throughout almost the entire line cycle, with maybe a short dip at the voltage crossing.

That circuitry WILL cost a bit more, but ought to be worth it to the end user. What you describe is basically a strobe light!

Jon

Maybe not by manufacturer of the complete lamps, but the makers of the control chips all publish reference designs that are likely VERY close to what is in the lamps using those particular chips. There are ENTIRE magazines devoted to LED lighting circuits, applications, etc. right now!

Jon

I would like to see a ref design that is very close. Thanks.

John S

With plenty of voltage available (during AC peak) and a relatively high series impedance, why would the conduction angle be very short ?

A white LED has a threshold voltage about 2.7 V, so with 30 LEDs this would be 81 V. With US mains peak voltage of 170 V, the threshold voltage would be about 48 % of peak voltage. Thus, some light would be produced between 30 and 150 degrees each half cycle, thus 2/3 of the time. How does this differ very much from fluorescent lamps with 100/120 pulses/s ?

People also tolerated 50 or 60 pulses/second from CRTs for decades (admittedly at a lower surface brightness).

The 5mm LED ( bluish white) appeared to flicker slightly and the 3mm one ( paper white ) did not visibly flicker at all.

Surprising - no ?

.... Phil

And nothing else - I forgot to mention the 47uF cap filtering after the bridge rectifier. It is in the photo. It makes all the difference but at

I wonder if you could use two parallel strings, one in each direction...... I've done that at lower voltages...

"David Lesher" wrote in message news:jcube0$8vf$ snipped-for-privacy@reader1.panix.com...

Might be risky if one LED in one string opens.

The real problem with the circuit using a series capacitor is the high = surge=20 at turn-on (depending on phase angle), and line voltage surges. Plus the = LED=20 current varies quite a bit with input voltage. Why not use a FWB and a=20 simple current regulator? One circuit that should work is as follows. It =

uses a high voltage MOSFET but it's probably cheaper than a big film=20 capacitor. For instance, the BSP125 is 600V 120mA for about $0.35 = each/100.=20 I simulated a string of white LEDs with zeners and one LED. For greater=20 efficiency and usability at lower voltages a switching supply with = inductors=20 may be required. But a circuit like this is dimmable, at least with a=20 variable transformer type control. TRIACs and SCRs, not so much.

Paul

=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

Version 4 SHEET 1 1208 680 WIRE 416 16 208 16 WIRE -64 64 -112 64 WIRE -32 64 -64 64 WIRE 64 64 32 64 WIRE 144 64 64 64 WIRE 208 64 208 16 WIRE 208 64 144 64 WIRE 240 64 208 64 WIRE 336 64 304 64 WIRE 144 96 144 64 WIRE 400 112 400 64 WIRE 400 112 208 112 WIRE -32 144 -48 144 WIRE 64 144 64 64 WIRE 64 144 32 144 WIRE -112 160 -112 64 WIRE 416 160 416 16 WIRE 208 192 208 176 WIRE 48 224 32 224 WIRE 144 224 144 176 WIRE 144 224 112 224 WIRE -64 256 -64 64 WIRE -32 256 -64 256 WIRE 32 256 32 224 WIRE 144 272 144 224 WIRE 160 272 144 272 WIRE 32 304 32 256 WIRE 48 304 32 304 WIRE 208 304 208 288 WIRE 208 304 128 304 WIRE 272 304 208 304 WIRE 416 304 416 224 WIRE 416 304 272 304 WIRE -112 352 -112 240 WIRE -48 352 -48 144 WIRE -48 352 -112 352 WIRE -32 352 -48 352 WIRE 32 352 32 304 WIRE 272 368 272 304 FLAG 272 368 0 SYMBOL LED 192 112 R0 SYMATTR InstName D1 SYMATTR Value NSSWS108T SYMATTR Description Diode SYMATTR Type diode SYMBOL voltage -112 144 R0 WINDOW 3 -53 -83 VRight 2 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V1 SYMATTR Value SINE(0 200 60 50m 0 0 60) SYMBOL nmos 160 192 R0 SYMATTR InstName M1 SYMATTR Value STP8NM60 SYMBOL res 144 288 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R1 SYMATTR Value 270 SYMBOL zener 48 240 R270 WINDOW 0 36 32 VTop 2 WINDOW 3 -4 32 VBottom 2 SYMATTR InstName D2 SYMATTR Value BZX84C6V2L SYMATTR Description Diode SYMATTR Type diode SYMBOL diode -32 80 R270 WINDOW 0 32 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName D3 SYMATTR Value UPSC600 SYMBOL diode -32 160 R270 WINDOW 0 32 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName D4 SYMATTR Value UPSC600 SYMBOL diode 32 272 M270 WINDOW 0 32 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName D5 SYMATTR Value UPSC600 SYMBOL diode 32 368 M270 WINDOW 0 32 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName D6 SYMATTR Value UPSC600 SYMBOL res 160 192 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R2 SYMATTR Value 100k SYMBOL zener 304 48 R90 WINDOW 0 -4 32 VBottom 2 WINDOW 3 36 32 VTop 2 SYMATTR InstName D7 SYMATTR Value 1N5373B SYMATTR Description Diode SYMATTR Type diode SYMBOL zener 400 48 R90 WINDOW 0 -4 32 VBottom 2 WINDOW 3 36 32 VTop 2 SYMATTR InstName D8 SYMATTR Value 1N5373B SYMATTR Description Diode SYMATTR Type diode SYMBOL cap 400 160 R0 SYMATTR InstName C1 SYMATTR Value 4.7=B5 SYMATTR SpiceLine V=3D300 TEXT -180 402 Left 2 !.tran 1 startup TEXT 424 72 Left 2 ;Without C1:\n250V P-P R1=3D100 R2=3D100k Input 1.4W = Output=20