Sharp LC-70LE650U LED Voltage & Current per channel

[mp3car]

I have a 70" sharp LCD and I am scrapping it for parts... Bad panel...

I'll probably sell the PS board, main, and t-con boards on eBay, but I salvaged the LED strip and backlighting components...

I sadly didn't think to take voltage or current measurements of the drive to the LEDs. I assume it is current regulated, adjusted with brightness. Can anyone give me any specifications on the maximum forward voltage and maximum current of an LED "channel" (64 LEDs per strip, called LED1, LED2, LED 3 on the PS board).

Thank you!!!

[budm]

Re: Sharp LC-70LE650U LED Voltage & Current per channel

64 LED x about 3.5V = Required Voltage, LED is current device so current limiter is needed.

[mp3car]

Re: Sharp LC-70LE650U LED Voltage & Current per channel

Yeah, I'm aware current limiting is needed, which is why I said the power supply board driving the LEDs would likely be current regulated... Perhaps I should have said a fixed current drive as the brightness changed... I have know idea what these LEDs are rated for as far as maximum current; am I dealing with 64 elements or 128, because it appears as though each of the 64 may be a "dual element" built into a single package, which would likely be in series, so then it'd be 128 elements... I want to get as much out of the strip as I can, but I don't want to overdrive it... But without knowing the exact part number of the LED, likely not made by Sharp, I am wondering if anyone had access to the specs of the current and/or voltage specs...

Even if someone could tell me the normal "voltage" measurement of each LED channel, that'd be a start! Based on the size, I'm guessing the max fwd current is at least 500mA if not 1A or so... I am guessing it's going to be in the 150-200VDC range per channel, just wondering if I can get a rough idea, but as you mention, the ideal quantity to know would be what is the min/max current On each channel with respect to full bright and minimum brightness, but the voltage the power supply drives each channel with would help as well...

[budm]

Re: Sharp LC-70LE650U LED Voltage & Current per channel

If you have constant current source, it does not have to be anything in the 100's range, for testing to see which one has open LED in the string you can go as low as 30~50mA range using the constant current source that can put out enough high Voltage to at the total Vf, finding constant current source that can put out enough Voltage is the problem.
Is this the board?
http://assets.shopjimmy.com/media/ca...31wjqz-top.jpg
As you can see from the board layouts, all the Cathode of the LED1, 2, and 3 are all tied together and connected to the Drain pin of PWM driven Power MOSFET Q7202, the Source pin is connected to the LED current sensing resistor which is then return to Ground.
Q7201 is the MOSFET for the boost converter circuit, D7216 is part of the boost converter, cap C7229A in parallel with cap C7229B are connected to the Cathode of D7216 they are the filter caps for the output of the boost converter, that 18-pin SMD IC is the LED driver controller.

[mp3car]

Re: Sharp LC-70LE650U LED Voltage & Current per channel

How would hooking it up tell me which one has an open since they're in series?

Doesn't matter though because they all work, the panel is what was failed (more specifically one of the row/column IC's).

I want to use the LED strips for another purpose, and wish to drive them close to their maximum current... I just don't know what that is, and of course they'll get warm even when being driven within spec...

[budm]

Re: Sharp LC-70LE650U LED Voltage & Current per channel

How would hooking it up tell me which one has an open since they're in series?

Doesn't matter though because they all work, the panel is what was failed (more specifically one of the row/column IC's).

I want to use the LED strips for another purpose, and wish to drive them close to their maximum current... I just don't know what that is, and of course they'll get warm even when being driven within spec...

My reply: As you can see from the board layouts, all the Cathode of the LED1, 2, and 3 are all tied together and connected to the Drain pin of PWM driven Power MOSFET Q7202, the Source pin is connected to the LED current sensing resistor which is then return to Ground. All the CATHODE are tied together, for it to be series connection the The ANODE of the first string will have to be connected to the Boosted out put then the Cathode of the first string will be connected to the Anode of the second and so on for the third string, that is called series connection.

Post 95: https://www.badcaps.net/forum/showth...t=25810&page=5
Post 107: https://www.badcaps.net/forum/showth...t=25810&page=6

"they'll get warm even when being driven within spec.." They get HOT and that is why thermal management is VERY important but so far none of the panel makers seem to care because the LED backlghts are failing like crazy.