There are many types of light-emitting diodes, according to the type of color and brightness voltage is different, a single voltage in the 1.5V-9V range, we in the daily use of LED light-emitting diodes, need to be equipped with a driving power supply, because our daily life is used in 220V voltage. If it is used for testing, it is very convenient to use an adjustable power supply to perform a transformer test.

LED is divided into two kinds of constant current source and constant voltage source, constant current is the current extra, the voltage can be shaken within a certain range, the lamp bead is not affected, so the commonly used LED is a constant current source.

The power supply, that is, the regulated power supply, the power supply wavering has a greater impact on the LED. In the series circuit, because of the impact of the production process, it is impossible for each LED LED resistance is exactly the same, so it is difficult to ensure that the voltage of each lamp bead is common, it is simple to burn the lamp bead with small resistance, so it is generally not used.