Internal Schematic and Voltage Specifications of LED Strip Light

This article examines the internal circuitry and mechanisms of an LED strip light. This information is intended for engineering discussions and is not essential for typical users interested in standard LED strip usage.
 

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The designated voltage of an LED strip, such as 12V or 24V, is predominantly dictated by:
1) The designated voltage of the LEDs and components utilised, and
The arrangement of the LEDs on the LED strip.
LEDs are generally 3-volt components. A 3-volt differential applied across the positive and negative terminals of an LED will illuminate it.
What occurs when multiple LEDs are arranged in a series configuration, sequentially? The individual LED voltages are aggregated.
Consequently, three LEDs in series necessitate a forward voltage of 9 volts (3 volts x 3 LEDs), while six LEDs in series require a forward voltage of 18 volts (3 volts x 6 LEDs).
Alongside the LEDs, one or more current-limiting resistors are essential to prevent the LED strip from entering overcurrent mode. The resistor is connected in series with the LEDs, and its resistance is determined to draw approximately 3 volts as well.
Three LEDs in series necessitate 9 volts for the LEDs and 3 volts for the resistor, totalling 12 volts.
Six LEDs in series necessitate 18 volts for the LEDs and 3 volts per resistor (x2), totalling 24 volts.
These constitute the fundamental components for each cluster of LEDs on an LED strip. The configuration on the LED strip is illustrated in the graphic below:
What occurs to LEDs when connected in parallel? The voltage remains constant while the current is evenly distributed across each parallel circuit. Consequently, if three parallel groups each draw 50 mA at 24 volts, the cumulative power consumption amounts to 150 mA, also at 24 volts.
These two instances of 3 LEDs and 6 LEDs illustrate the configuration of a standard 12 and 24 volt LED strip. The LED strips employ 3-volt LED components and are designed with multiple parallel configurations of 3 or 6 LEDs.

Must the voltage provided be precisely as specified?

One might question whether 12 volts signifies precisely 12.0 volts or if 11.9 volts would suffice. The positive aspect is that there is considerable flexibility in the power provided to an LED strip.
The following chart from an LED datasheet illustrates the current flow through an LED as a function of volt
At 3.0V, this specific LED will draw approximately 120 mA. Reducing the voltage to 2.9V will result in the LED drawing approximately 80 mA. Increasing the voltage to 3.1V will result in the LED drawing approximately 160 mA.
In a 12V LED strip comprising three LEDs and a resistor in series, providing 11V instead of 12V effectively reduces the voltage across each LED by 0.25V.
Will the LEDs operate at 2.75V? According to the chart above, the current draw is projected to decrease from 120 mA per LED to approximately 40 mA.
Although this represents a considerable decrease, the LEDs will function adequately, albeit at a substantially reduced brightness level.
What would occur if we provided only 10V to a 12V LED strip? In this instance, we are decreasing the voltage for each LED by 0.5V. According to the chart, at 2.5V, the LEDs will draw minimal current.
 

At this voltage level, you will probably observe a faint LED strip.

All voltages below the LED strip's rated capacity are safe, as they will consistently draw less current, thereby mitigating any risk of damage or overheating. What is the status of voltage levels exceeding 12V?
Let us examine the provision of 12.8V to a 12V LED strip. This elevates the voltage for each LED by 0.20V.
The LED is currently operated at 3.2V, exhibiting a current draw of 200 mA as indicated by the chart.
The maximum current rating specified by the manufacturer is 200 mA. Exceeding this level may jeopardise the integrity of the LED.
It is important to note that each LED possesses a distinct rating, and inherent manufacturing variability may influence the permissible voltage ranges for a specific LED strip.
We have demonstrated that a 12V LED strip transitions from off to overdriven within a limited voltage range of 10V to 12.8V.
Although it is feasible to provide a voltage that deviates slightly from the specified rating, meticulous attention is required to prevent any potential damage to the LEDs.
 

How can one dim an LED strip?

One method to reduce the brightness of an LED strip is to lower the input voltage beneath its specified rating, as previously demonstrated. In actuality, power electronics are ineffective at diminishing the voltage output in this manner.
The optimal technique involves employing PWM (pulse width modulation), wherein the LEDs are activated and deactivated at a high frequency. Modifying the duty cycle by altering the ratio of time on to time off can adjust the perceived brightness of an LED strip's light output.