Led lamp

[ericgibbs]

Please explain: at what part of the cycle the electrolytic gets "all this extra energy" to deliver it to the LEDs.

You know exactly how it works, so please stop playing games in attempt to disrupt this thread.

If you dont, do as I suggested earlier Google for it.

 

[tvtech]

Please explain: at what part of the cycle the electrolytic gets "all this extra energy" to deliver it to the LEDs.

Sigh. The 22uF does a little smoothing. Thus reducing the flicker. Simple.

tvtech

 

[colin55]

Sigh. The 22uF does a little smoothing. Thus reducing the flicker. Simple.

The 22u does not do any smoothing. It has no effect on improving the performance.

With the 22uF present during the negative half cycle, the 22uF supplies a lower holding current to the LED's so they do not go completely off.

This is completely wrong.

I have fully explained how the circuit works on my website under "Spot the Mistake, P13."
No-one has been able to explain how the circuit works.
Both ericgibbs and tvtech have got it wrong.

 

[tvtech]

Post redundant. Issue resolved.

 

[alec_t]

From running a sim based on the one in post #39, both with and without the zener and 22u cap present, I conclude that :-

1) The zener has two functions.
(a) Firstly when reverse-biased it clamps the voltage across the LED string to 48V minus a diode drop. This has the side effect that 16 LEDs with a Vf >=3V will pass very little current. Without the zener that voltage rises to ~52V (dependent on LED type) and allows a greater LED current.
(b) Secondly when forward-biased it allows essential reverse current to flow through the 220n cap on mains negative half cycles.

2) Without the 22u cap the LED current is ~90 deg phase-shifted with respect to the mains voltage. Current peaks occur at the zero-crossings of the mains waveform. LED current starts to rise from zero when the mains voltage is ~48-52V above the negative peak and drops to zero at the mains positive peak. With the 22u cap present the LED current peak coincides (~) with the mains positive peak and the LED minimum current (no longer zero) coincides (~) with the mains negative peak. Increasing the cap value increases the minimum LED current and hence reduces (but doesn't eliminate) current ripple.

 

[tvtech]

Post redundant. Issue resolved.

 

[ericgibbs]

hi alec,

Many thanks for that impartial report.

It does support mine and tvtech's posts regarding the function of the zener and 22uF capacitor.

E.

EDIT:
BTW: Alec , try it with a 1N4007 in place of the 48V zener diode.

E.

 

[rocky01]

Hi all,
Though I am replying to tvtech, this goes for all of you guys who are discussing so intensely on my post. first of all, I salute to all of you for such technical inputs which really helped me a lot in understanding things since i am a novice. once again thank you each one personally for your valuable inputs.

 

[rocky01]

hi guys,

i have a problem here. i am not able to procure 0.22 uf 630 volt. i only have 0.22 uf 275 volt. now how can i use this 275 volt capacitor instead of the original one?

 

[ericgibbs]

hi guys,

i have a problem here. i am not able to procure 0.22 uf 630 volt. i only have 0.22 uf 275 volt. now how can i use this 275 volt capacitor instead of the original one?

hi rocky,
Do you have a type number for the 220nF that you have.??

We could double check the specification, ideally X2 class ratings are recommended for mains projects.

E.

 

[colin55]

275v is a bit low as the voltage of the 240v mains is 345v peak.

The normal X2 capacitor is 400v.

Try it with the 100R safety resistor. If it shorts, the resistor will burn out.

 

[alec_t]

275V rating is too low, as stated above. For safety the cap should be X2 400V rated as Colin says.

 

[tvtech]

275V rating is too low, as stated above. For safety the cap should be X2 400V rated as Colin says.

First of all no arguments please. Hi guys.

X2 mains rated caps are specified @ 275VAC to 305VAC. Depending on Manufacturer.

They are the the guys that sit permanently across your Mains supply and are part of EMI suppression. These caps work 24/7 from birth. You will find them in all SMPS applications. They are the last thing to pack up ever in a blown SMPS.

And they handle everything that is thrown at them. Including the odd lightning strike. When all else is destroyed in the SMPS.

Thank you

tvtech

 

[alec_t]

No argument with that; but the OP didn't say his 275V cap was X2 rated. For all we know it's 275VDC

 

[tvtech]

No argument with that; but the OP didn't say his 275V cap was X2 rated. For all we know it's 275VDC

Never mind Alec. See you tomorrow.

Kind regards,

tvtech

 

[colin55]

If the capacitor is X2 - the rating 275v is suitable for 240v mains as the rating is "AC mains rating."

 

[alec_t]

Rocky, you've hijacked someone else's thread. Start your own thread and you may get some help.

 

[rocky01]

Dear alec_t
just go to page 1 to see who started the thread.

 

[alec_t]

Apologies. My bad (the shift in topic threw me)

Hi Alec,
To make it clear to other posters, I have moved this change of Topic for Rocky here.

https://www.electro-tech-online.com/threads/help-with-prebuilt-led-lamp.127616/

Eric