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LCD TVs - LED

How to lower backlight voltage

Juanjo cortes
hace 5 años
hace 5 años
Hello dear technicians ... I ask this question because I have repaired several LEDs in the backlight part but at the same time they fall under the guarantee for the same theme ... the same LEDs do not burn in many cases ... and the idea This question is because I have seen on the internet some videos in which the backlight output voltage goes down, my problem is where it specifically puts a certain resistance to lower voltage ... if someone protects it in any other way I hope to contribute the idea. .since already thank you ..
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seekude
seekude
seekude
2.085
hace 5 años
hace 5 años
I explain. The backlight driver is basically a step up source, it raises a continuous voltage to that required and configured, the IC driver has protections against over voltage, over current, and, open circuit, short circuit in the LED array. Now, generally, the backlight ICs have a pin that senses the current (ISNS) that returns from the backlight, said pin is connected by a resistance to the source of the return switching mosfet, in turn this is connected to GND by means of resistors ( these are usually low ohmic and put several in parallel), if you realize we have a splitter, if I add the resistance between source and GND, more current will go to ISNS, and as the ic driver feels current, it adjusts and modifies its output based on that reference, will lower the voltage, thus circulating less current. So what is done is to eliminate some resistance (s) between source and gnd, and, as they are in parallel, in this way we increase resistance.
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Juanjo cortes
hace 5 años

Thank you very much friend for your great explanation ... you have dried up a tremendous doubt ... because to the workshop 70 percent of the failures that come are backlight in particular ... that is going to be that my repairs improve ... anything I consult you ..very thankful ..

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JoseO
JoseO
JoseO
1.634
hace 5 años

Best explanation impossible ...

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JoseO
JoseO
JoseO
1.634
hace 5 años
hace 5 años
What I can tell you is that it is in the return of the LEDs, and it does not put resistance, rather some (s) are removed or you replace the set with some other of the suitable ohmiaje until reaching the necessary voltage, they are several connected in parallel in the area of the return, there you can guide yourself since telling you exactly is not possible since it varies on each TV, generally the values to be achieved vary between 2 and 4 ohms depending on the case. There is a very good video of Electronica Nuñez where it explains very well the process keep in mind that if you lower the voltage a lot you will impoverish the image.
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ruben dario
hace 5 años

Tell the customer to use the brightness of the TV more than 70 x percent. that gives durability to the led

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JoseO
JoseO
JoseO
1.634
hace 5 años

Friend so adjust the brightness in half the voltage to the led is the same, I know because I have already done those tests

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Juanjo cortes
hace 5 años

The friend is right ... I told customers about the brightness but at the same time they fall the same ... and the electronic video Núñez I saw it ... the resistance puts it from the third leg of the MOSFET of the negative backlight line and the other stops the resistance I know where it is going to stop .. I don't see that well ..

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JoseO
JoseO
JoseO
1.634
hace 5 años

OK, well the other leg goes directly to GND, if you are going to do this remember that you must disconnect the set of resistors that the TV already has on the third leg of the mosfet that you say if you leave them connected the voltage rather rises and you can burn the complete strips, do it with due caution.

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Juanjo cortes
hace 5 años

Okay..

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Juanjo cortes
hace 5 años

One last question, friend, because reason is not added resistance ... if I am adding ohm to treat voltage ... and actually it is replaced ... it is not the same to add resistance to change it to a larger one ...?

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seekude
seekude
seekude
2.085
hace 5 años

If they are in parallel when adding resistance "does not add" but lowers the ohmiaje.

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nel294
nel294
nel294
83
hace 5 años

Good evening, and watched some Núñez electronic videos but in most cases he replaces low-value resistors with higher-value ones, so we remove or add him?

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Emiliano Barros2
hace 5 años
hace 5 años
Excellent contribution. Thank you very much and I will do it, the objective is to lower the voltage and thus make the LEDs last longer.
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