Since you altering both the switch and the bulb, it would be much easier to put all the circuicity at the switch and run DC to the bulb, with only LEDs in the bulb. Simpler, cheaper, more reliable.
...unless the PFC is because they cant put big electrolytics after the mains diode bridge due to the way triac dimmers interact with filter inductors and big electrolytics?
What PFC correction circuitry are you referring too?
All I am familiar with is the simple multistage RF and line noise dampening filters on most every solid state power supply I have ever taken apart.
I can't see how a few .1 uf capacitors and MOV's connecting the lines to common and ground and one or two small RF chokes could do much to change the overall power factor on one of these power supplies?
Am I missing something here in their design or are they designed to different specs where you are?
Power factor correction has to do with making a "computer power supply" look like a resistive load. Most things like a TV only take power at the very peak of the sign wave. The current waveform is "pulsed" not sign wave. The current is very high for 20% of the sign wave.
A resistive load has a current waveform that matches the voltage waveform (sign wave). The power company wants a resistive load.
What PFC correction circuitry are you referring too?
All I am familiar with is the simple multistage RF and line noise dampening filters on most every solid state power supply I have ever taken apart.
I can't see how a few .1 uf capacitors and MOV's connecting the lines to common and ground and one or two small RF chokes could do much to change the overall power factor on one of these power supplies?
What PFC correction circuitry are you referring too?
All I am familiar with is the simple multistage RF and line noise dampening filters on most every solid state power supply I have ever taken apart.
In light bulbs the PFC is very simple. There is not two stage switcher in most I looked at. The design posted above, the IC watches the line voltage. When the voltage is at the peak of the sign wave the PWM runs at full current. When the line voltage is less than peak, then the current in the MOSFET is also less by that amount. They added a multiplier to the output of the error amplifier. error out * line voltage = duty cycle
There is not a second inductor, second (IC + FET + diode). The major change is in silicon.
I just picked up a 2012 Vizio HD LCD TV for cheap because it supposedly had a blown power supply. (Bad micro fuse on the 24 volt power for the backlighting driver board)
I didn't see anything out of the ordinary in its primary power supply design. Standard layout from what I know SMPS input circuitry as.
I just picked up a 2012 Vizio HD LCD TV for cheap because it supposedly had a blown power supply. (Bad micro fuse on the 24 volt power for the backlighting driver board)
I didn't see anything out of the ordinary in its primary power supply design. Standard layout from what I know SMPS input circuitry as.
No I don't. What I saw was the standard input circuity that consists of a fuse followed by an inductor a set of small AC snubber capacitors and Varasitors ending at the main rectifier and large 400 volt capacitor.
Everything after that was directly related to the SMPS control systems. All around I considered it a rather common and easy circuit to read and find out where the micro fuse was for the 24 VDC feed on the backlighting drive board while doing live voltage readings going out from the DC side of the system.
None of it jumped out at me as being extra or additional components on the AC input side.
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I deal mostly with large power systems so to me PF control has always been an AC side control process.
Looking at the schematics of the linked circuit I see how they are doing it and the circuit is considerably different that what I found in my Vizio TV. The power supply it has went directly from the main bridge rectifier right into the main HV DC rail with a several hundred uf 400 VDC electrolytic capacitor.
I don't see how any PFC adjustment could be made in that design given the reasonably low average ripple the large capacitor would provide.
Here's a screen dump (sorry about the lack of detail) of part of a PSU from a2009 Sony KDL32W5800 - this is typical of all European TV's in recent years.
I know the USA tends to be rather slow in their technology, or perhaps it's just your lower standards for emissions and environmental issues?.
Just to show it's not just decent makes, I presume Vizio is a cheap junk make? - here's the PSU manual for a typical Vestel set, who make many of the cheap junk supermarket etc. TV's in Europe.
From a 20W bulb with a PF of 0.99.
The input current is close to a sign wave.
They did not have to add many parts to get PFC.
MOSFET current and voltage.
132 VAC, 60 Hz. Power line.
Upper: ID7, 1 A / div. Output diode current.
Lower: VD7, 20 V, 2 ms / div. Output diode voltage.
Picture on right. Expanded waveform
Upper: ID7, 1 A / div.
Lower: VD7, 20 V / div., 5 s / div.
Around here PFC adjustment is largely done by the power company on their side of the systems. We customers don't need to worry about it on our end. It is likely why I am not familiar with seeing it on anything that has less than a few KVA rating in the devices I tend to work with.
As far as what I buy goes I could care less about who made it or how "green" it is. I have cheapo LCD TVs and computer monitors and I have high end ones too and almost all of them came to me cheap or free because they didn't work.
If you could score a 1 year old 26" HD LCD TV that retails for around $350 new for $50 because it needed a new 1 amp fuse would you really care about what its PF was?
I know the USA tends to be rather slow in their technology, or perhaps it's just your lower standards for emissions and environmental issues?.
Hey now we waste more money and fuel than any other country in the world on emissions regulations!
Does any other country burn twice as much fuel as necessary getting from point A to point B to meet politically motivated and all around poorly though up emission standards? I think not!