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.
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.
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.
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?
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?
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.