Principle, understanding, and related computing of Light Emitting Diode

1. Principle

The light-emitting second-level tube is also a diode. The diode requires a certain forward voltage to be turned on. After being turned on, it can be considered as a conductor.

So to make the LED light, we must first have a forward pressure drop, which is generally 2-3 V.

At the same time, the current must be ensured for brightness.

The relationship between voltage and current cannot be directly calculated because the light emitting diode is not a normal resistor.

The manual generally gives the operating voltage and current. Our principle is:

When the operating current is ensured, the series resistance is calculated.

 

2. Calculate the series resistance

If the LED requires 3 V conduction and the operating current is 20ma, the resistance value is

R = (Power Supply Voltage-3 V)/0.02.

The calculation principle is that 3 V is the partial pressure of the LED, the power supply voltage-3 V is the partial pressure of the resistance, and 0.02 is the current of the resistance and the LED branch, so that the required resistance value is calculated.

In this resistance value, 3 V is added to the LED, and the power supply voltage-3 V is added to the resistor. The current is 20ma, and the circuit works normally.

 

The following is a detailed description of the calculation method.

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