### Author Topic: Universal LED TV board - LED driver low voltage  (Read 149 times)

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#### gojunnyo

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##### Universal LED TV board - LED driver low voltage
« on: April 10, 2020, 09:13:12 am »
The TV Backlight has 4 strips with 9 LEDS all connected in series. My rough estimation ( 9 * 4 * 3.3  = 118.2VDC) assuming the LED consumes 3.3V, so I expected the LED driver to output such voltage but in turns out to output 52 volts on standby and 57 volts when the tv is turned on. I can't find the schematic online, but the board has a model no. of TP.V56.PB801

Any tips on where to start is much appreciated! I need to be enlightened by your experiences.

#### Haenk

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##### Re: Universal LED TV board - LED driver low voltage
« Reply #1 on: April 10, 2020, 09:55:39 am »

The voltage stated matches your measurements, so that board is probably OK.

#### gojunnyo

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##### Re: Universal LED TV board - LED driver low voltage
« Reply #2 on: April 10, 2020, 11:22:43 am »

The voltage stated matches your measurements, so that board is probably OK.

Interesting, the strips are connected in series, and hooked each strip on my bench power supply, It is surely bright at around 27 volts, unless I modify the whole strip connection into series-parallel

#### shakalnokturn

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##### Re: Universal LED TV board - LED driver low voltage
« Reply #3 on: April 10, 2020, 12:45:57 pm »
I don't have that much experience with TV LED string supplies, in theory a LED supply should be current regulated.
Of course the maximum voltage the LED supply can deliver is one limitation.

Maybe you can get away with 2 series 2 parallel wiring although the string voltage will be close to the maximum that the supply will deliver.
If you try 4 parallel strings and the supply will accept to run at that voltage the next problem is getting enough current to each string to achieve sufficient brightness. Maybe you have some adjustment for that.

In any case when paralleling strings the minimum would be to add a little series resistance on each branch to the effect of Vf imbalances.

Smf