LEDs vs CFLs

[JohnW2]

This means if the LED is current regulated using a simple capacitor ...

You keep mentioning this, but I can't see how it could work (unless there were a lot more than just the capacitor). (Forward) current 'control' with just a capacitor would obviously only work if the LED were being fed with AC, and if that were the case, the maximum PIV of the LED would be exceeded during the 'reverse-biased' half-cycles, which I would have thought would kill it. What am I missing?

Kind Regards, John

 

[ericmark]

OK a little more than just a single capacitor, but the current regulation relies on what can pass through the capacitor there is no regulator as such, I have a replacement for a quartz halogen tube with a voltage range of 85 ~ 250 volt, this clearly has a PWM chip in it and gives out the full 100 lumen per watt, the replacement for my 65W fluorescent tube states 230 volt, but since it will work with same output if the ballast is left in place or taken out again clearly a PWM driver again 100 lumen per watt, since the new 58W fluorescent with a HF ballast is around 95 lumen per watt, and lasts the same time, unless it does give a 100 lumen per watt it is no better than the fluorescent it replaces.

However although there were cold cathode GU10 bulbs they were not very good, and the bulbs with E27, E14 and BA22d were also rather poor, so even at 75 lumen per watt the LED replacement bulb is better than most fluorescent bulbs. And using capacitors as current limiters, means the bulb can be easy dimmed, so in the main the cheap LED bulb is only around the 75 lumen per watt. Personally I have used cheap bulbs throughout the house, I am not really worried if only 75 lumen per watt.

However to compare with fluorescent we must accept in the main the LED in a bulb is rather cheap and nasty.

 

[winston1]

You keep mentioning this, but I can't see how it could work (unless there were a lot more than just the capacitor). (Forward) current 'control' with just a capacitor would obviously only work if the LED were being fed with AC, and if that were the case, the maximum PIV of the LED would be exceeded during the 'reverse-biased' half-cycles, which I would have thought would kill it. What am I missing?

Kind Regards, John

You are missing the bridge rectifier that goes between the capacitor and LED.

 

[JohnW2]

You are missing the bridge rectifier that goes between the capacitor and LED

It was not so much a case of my missing it as of Eric not mentioning it. As I implied, I could understand it working if it were 'more than just a capacitor'.

Kind Regards, John

 

[ericmark]

You are missing the bridge rectifier that goes between the capacitor and LED.

Thanks it was that report I had seen before, the point I noted was no regulation and also they have a bleed resistor I would guess to allow use of dimmer with no neutral so total lumen per watt only around 75.

Mine can't be quite same design, as noted they make the fan in the same room look as if it's turning slowly, so don't think they have the smoothing capacitor. I think I have just one CFL bulb replacement left in service, in the garage so not used much, however I also have a folded tube reading lamp. It uses a PLS Compact Fluorescent Lamp 11 watt Warm White 830 these are still considered as CFL even though only one fold in the tube,

these are rated 900 lumen so around 82 lumen per watt, with a 11W Phillips LED bulb you can get 1055 lumen 96 lumen per watt, but many are a lot lower output, with the scrolled tube an 11W is down to 600 lumen so with the standard CFL the LED wins, but with the one shown it still gives the LED a good run for the money.