When repairing or replacing a TV backlight LED strip, one of the first and most critical questions is: what voltage is required? The answer is: it depends. The voltage depends on how many LED chips are in series (or parallel), the forward voltage of each LED, and the design of the backlight driver circuit.
Below is a detailed guide to understanding, estimating, and measuring the working voltage of TV backlight LED strips, along with practical tips and cautions.
An LED (light-emitting diode) exhibits a forward voltage drop (V_f) when conducting current. For white or blue LEDs (commonly used in backlights), this is often in the range of ~3.0 V to ~3.8 V (depending on the LED chip and current).
Because LED current rises sharply beyond its forward voltage threshold, LED circuits are usually designed to use constant current drivers (or current regulation) rather than relying purely on a constant voltage source.
In TV backlights, multiple individual LED chips are often grouped into strips and wired in series strings, so their forward voltages add together. The driver supplies enough voltage to cause the designed current through the entire series string.
Sometimes there are multiple such strings in parallel (or segments that light in sequence). The driver must accommodate that arrangement.
Thus, the required supply voltage is the sum of the forward voltage drops of all the LEDs in one series string, plus a little margin to allow current regulation.
The actual voltage needed can vary widely depending on TV size, the number of LEDs per string, the design of the backlight, and the desired brightness. Here are some real-world examples and ranges:
| Scenario | Approx. LED forward drop per chip | Number in series | Implied strip voltage | Comments / source |
|---|---|---|---|---|
| 32-LED strip (8 per strip × 4 strips) | ~3.6 V | 32 (in a large string) | ~115–120 V at designed current | In one repair attempt, the LED connector was labeled 118 V and current ~260 mA |
| Smaller series of 6 LEDs | ~3.5 V | 6 | ~21 V | From forum advice: “mostly LEDs will illuminate with less than 4 volts across each one, so with a series of six LEDs the supply could be up to 24 V” |
| Mid-size tv strips | ~3.2–3.8 V | 10–20 | 32–76 V | In one case, the backlight supply in a Vestel board was 50 V |
| Edge cases | variable | many | tens to >100 V | Some large TVs with many LEDs in series demand higher voltages |
From repair forums:
“Their voltages have ranged from 24 volts to 28 volts. That is per individual strip after separating any that are connected in series.”
In short: small or segmented strips may run in the 20–50 V range, while full backlight strings for large panels may require 80–150 V or more.
Here is a step-by-step method you can use when faced with an unknown LED strip:
Count the number of LED chips in a single series string (or trace). Sometimes the strip is labeled or the layout reveals this.
Estimate the forward voltage per LED (white LED typical ~3.0–3.7 V, depending on current and chip).
Multiply: Voltage ≈ number_of_LEDs × V_f.
Leave margin: the driver will supply a bit more to regulate the current.
If possible, measure the voltage across a functioning strip in the original TV with a multimeter (taking safety precautions).
Use a current limiting source or adjustable supply at first when testing, to avoid damaging LEDs.
When testing, some repairers apply a low voltage gradually and see the first LEDs light, then ramp up carefully.
Caution: never exceed the designed current or voltage too far — that will shorten LED life or burn them out.
TV size and LED count: Larger screens often have more LEDs, more strips, or longer series chains, so required voltage climbs accordingly.
Brightness and current specifications: Higher brightness means more current, which may push the LED forward voltage slightly upward.
Design of backlight driver: Some designs favor many smaller series strings, others one long chain.
Thermal and aging effects: Over time, LED characteristics drift; driver may compensate within some margin.
Edge-lit vs direct-lit layouts: Edge lighting may use shorter strips and thus lower voltages in some parts.
Because of these factors, the quoted voltage on a power board often does not directly equal the rated strip voltage, but is what the driver outputs under load. (iFixit)
Always drive LED strips with a constant current driver rather than a pure fixed-voltage supply, unless the circuit includes proper current regulation.
Start tests at lower voltage, increase slowly, monitor current and brightness.
Use series resistors or current-limiting circuits when experimenting.
Avoid overheating the strip — excessive brightness or overvoltage can degrade the LEDs or the circuit.
Replace entire matching strips rather than mixing mismatched units.
If you see markings like “94V” on the strip, don’t assume it is the supply voltage — it might be a flammability rating or model code.
If you need to source quality LED backlight strips, StarSharp is a notable option. Their product line includes both direct light strips and edge-entry strips for a wide range of TV sizes (from 24″ up to 85″).
Key advantages:
They offer a large catalog of over 5,000 different specifications and models, facilitating compatibility with many TV brands and models.
Their production capabilities are high (automated lines, mass quantity) which helps with reliable supply and consistent quality.
They hold industry certifications (e.g. ISO, ROHS) and are already a supplier to several domestic TV brands.
If you know the model or strip type you need (series count, tab layout, length), you can contact them for matching parts or replacements.
The required voltage for TV backlight LED strips depends on how many LEDs are in series and the forward voltage of each LED.
In practice, strip voltages often range from ~20 V (for short segments) to ~100 V or more (for full panel strings).
Always use a constant current driver or controlled source, and test gradually.
For reliable replacement strips, consider suppliers like StarSharp, which supports a wide variety of models and specifications.
