Samsung UN32EH4050F with LED backlights

[budm]

I just got this one in today, it has broken LCD panel, so I decide to open it up to see how the TV with LED backlights works. It has 32 white LED hooked up in series to 90V DC power supply.
I will be using as a light table and also as a light source for taking picture.
Not much inside at all, it uses about 50Watts of power but it does not have PFC circuit, the PFC is 0.65 which is very poor.

[ben7]

Re: Samsung UN32EH4050F with LED backlights

As always, lame caps. But, nice find on all the leds, they sure aren't cheap!

[tibimakai]

Re: Samsung UN32EH4050F with LED backlights

So I guess we can measure the output voltages on the trafs? No high voltage going to the LEDs? I assume that the bigger the TV, the output voltage has to increase too, no?
Do you think that it's possible to replace individually those LEDs?
You can make some nice LED strips for you car
I have a Vizio with 2 sec. to black issue(my first LED TV).
I'm back from Costa Rica(Pura Vida), tomorrow I'm getting all my mail(hold) and back on working on the TVs, yeahh.

[tom66]

Re: Samsung UN32EH4050F with LED backlights

There is no need for PFC anyway. Line losses are about 2% in the UK, and they would only slightly fall from using PFC in all devices. That is easily outweighed by the 5-10% efficiency loss from the PFC boost stage.

I have seen Toshiba and Sharp 32" LCD TV, both using chokes for PFC.

[budm]

Re: Samsung UN32EH4050F with LED backlights

By the way line loss is not the reason for requiring PFC, it has to do with Real power and the Reactive power. You can have a power generator running in the garage, but if your load has poor PFC, the generator will still have to put a lot of VA for your low PFC load.
Learn about PFC why the power companies do not like the have user to have large reactive load on the power line with power factor correction.
http://www.energy-in-motion.com/PFC.html
http://www.upe-inc.com/power-factor-...on-capacitors/
http://en.wikipedia.org/wiki/Power_factor

[tom66]

Re: Samsung UN32EH4050F with LED backlights

By the way line loss is not the reason for requiring PFC, it has to do with Real power and the Reactive power. You can have a power generator running in the garage, but if your load has poor PFC, the generator will still have to put a lot of VA for your low PFC load.
Learn about PFC why the power companies do not like the have user to have large reactive load on the power line with power factor correction.
http://www.energy-in-motion.com/PFC.html
http://www.upe-inc.com/power-factor-...on-capacitors/
http://en.wikipedia.org/wiki/Power_factor

Yes, that may be true. However, the additional losses only come from resistance in the generator's windings. It will not cause significantly extra mechanical load on the engine so fuel consumption would only be a bit higher, which again would probably be outweighed by any PFC losses (at least 5%, likely 10% or more, and greater at low line.)

It just adds extra complexity and cost to the design. Also I imagine running a TV off a generator is the manufacturer's least concern, they want it to work well from normal mains power.

Electricity companies don't charge average consumers for reactive power, only real power.

[budm]

Re: Samsung UN32EH4050F with LED backlights

it is not may be ture, it is true since reactive load will always require more VA to opreate even if every other factors are zero, if you only have pure resistive load then the power companies will not have to waste so much power.
Right now the consumer is not paying for VA yet, but with Smart meter, they will be charging the consumer base on VA since now the meter can calculate the PFC on each home since old mechanical meter cannot do. Power company are already proposing to charge home user base on VA which I will not be surprise if it will become the rules.

[tom66]

Re: Samsung UN32EH4050F with LED backlights

Current legislation does not permit companies to charge for VA. If they did so in a modern household, bills would skyrocket - imagine the cheap CFLs, for example. Their PFC is abysmal, around 0.5. Old computers don't have PFC. Iron core transformers in audio equipment would be the next victim, as the current is significantly out of phase due to high inductance. Also, as would a lot of old equipment - such as my old oscilloscopes, and my bench power supply (35V @ 3A - draws as much as 200W in certain configurations.) In general it would be a bad idea - but I suppose it wouldn't matter to the government as they've already screwed me over as a student!

I do wonder what the actual losses come down to. As I said, the line losses in the UK are a good example, about 2%. If you look at a mains waveform here, you will see it flat-topping very sharply due to the high current draws at the peaks from equipment. So I'd imagine the PF is quite poor but it isn't causing much losses.

It would be much easier to charge for VA; measure rms current and multiply by rms voltage which could be accomplished using simple RMS-to-DC converter ICs, or basic software routines on a DSP. Currently, the meters have to continuously measure voltage and current, calculate the product, and calculate rms from this to get real power, and they have to do it very accurately, meaning fast sampling rates. Older mechanical meters in fact used two coils, which turned the dial at a variable rate depending on the current-voltage product.

[budm]

Re: Samsung UN32EH4050F with LED backlights

That's right, why do you think they are pushing for Smart Meter? They already asking the home owner to allow them to install Smart Thermo stat so they can control the HVAC, Fridge, etc. during the peak load (I refuse to participate for my option to let them do it for my house). The Government are working hand in hand with power companies (lobbying/bribe) to get as much money from taxes (higher the bill, higher the tax).
Big brother is every where, I do not know about the policies in UK, but it is getting worst in the US. it is gonna get worst not better.
By the way, they are already charging at what time of day I use the power, so right now I have to use my washer and dryer at night, if i use them before 6PM, I will be charged more!

[tom66]

Re: Samsung UN32EH4050F with LED backlights

Well, we still use a dumb digital meter here, top-up payment instead of paying monthly. Electric companies love and hate it. One good thing is precise metering, never inaccurate, can work both ways though! Bad thing for them is unpredictable demand; they can't charge you for average usage, you only are charged for what you actually use.

I don't think PFC will solve the problem though. The main reason PFC was introduced as a requirement was to reduce line noise and harmonics, not VA. The standards explicitly limit line noise in the 3rd and 5th harmonics - with a high power device such a plasma TV, you simply must have a PFC circuit to eliminate these, without resorting to a massive line choke. However, in smaller TVs, such as 32" and below, they can get away with just a choke, because it effectively reduces the noise sufficiently. And that's less components to fail, plus the TV costs less to make. That's good.

---

We already have day/night rates in the UK. You must use a meter which supports "Economy7", basically after 7pm you get cheaper electricity. It's a good system. You get rates approximately 50-60% cheaper at night, so it encourages demand to be spread across the day. The problem with electric demand is you must always be capable of supplying the peak load, not the average. This means more generation equipment needs to be built, and it needs to be always ready to start (spinning reserve - usually running and consuming fuel continuously, ready to connect when needed.)

Getting off topic though one thing that does intrigue me is something called Dynamic Demand. The idea is for equipment which can delay itself (electric heating, fridges, freezers, etc) to add a few minutes of delay between their thermostat cycles (which doesn't really matter to them as the temperature will still remain within tolerance) but only if there is more demand on the line. The way demand is measured is through the AC line frequency. The frequency will fall under heavy demand and rise under light demand. The goal of this is to have the system self-regulate - load reduces under heavy demand and increases under light demand, which means less redundancy is required on the network.

You can test the theory with most digitising oscilloscopes with AC line trigger and frequency counter. Set the line trigger on, and watch the frequency change very much with minute-long cycles as the power company regulates the supply and demand. I've seen it drop as low as 49.88Hz here very briefly but it normally averages 50 Hz +/- 0.04Hz.

[BlueEastern]

Rather than start a new thread, I thought it may be best to reply here. If not I can start a new thread . I came across this when Googling the model number, I have the same tv. I was trying to just confirm what type of panel this is. I'm sure it's not an ips. Is it a TN panel? I understand it's a LCD type and LED backlit, but what is the panel itself? I also Googled each of the barcode numbers in the photos but nothing came up. I also went through the manual specifications it has a lot of technical details on it but nothing about the panel I could find . thanks

[nomoresonys]

Probably this, combined with the viewing angle deal where ips is better than va: Gently tap the panel of a TV. If the panel is a VA type (or TN computer monitor) you will see a little flash and change where you touch with your finger. It may look like a flash. If this happens the TV should be using a VA panel. If you see nothing, the TV is likely using an IPS type panel.

[BlueEastern]

Probably this, combined with the viewing angle deal where ips is better than va: Gently tap the panel of a TV. If the panel is a VA type (or TN computer monitor) you will see a little flash and change where you touch with your finger. It may look like a flash. If this happens the TV should be using a VA panel. If you see nothing, the TV is likely using an IPS type panel.

Just tapped the screen while turned on, .... Visible white flash each time. Must be a VA. Thanks so much!