Driving Type of LED Controller

                                                                                                         Driving Type of LED Controller

The LED controller is specially used to drive the LED to emit light. The LED is a current-driven component. If it drives fewer LEDs, it can be connected to the power supply in series with the current limiting resistor. If more LEDs are driven, the LEDs will be controlled by means of constant current output, the LEDs will be connected in series, the current flowing through the LEDs will be the same, and the brightness of the LEDs will be basically the same. The two schemes of constant voltage and constant current are described below.

1 Constant voltage series drive theory

Constant voltage drive can be divided into constant voltage series drive and constant voltage parallel drive.

Since LEDs will generate a forward voltage drop during normal operation, the more LEDs connected in series, the greater the overall voltage drop, so constant voltage series connection is suitable for high input voltage. The following figure is the circuit diagram of constant voltage series drive.

When using this method, it is necessary to calculate the forward voltage drop and the resistance of the current limiting resistor according to the number of LEDs to ensure that the current flowing through the LEDs is appropriate. The disadvantage of this scheme is that if one LED is damaged, all LEDs will not work.

In our daily application, the constant voltage is to drive LED strip, LED profile light or or other CV type light

2 Constant voltage parallel drive theory

This method is to connect multiple sets of constant voltage series circuits in parallel, and each path has a current limiting resistor. The realization circuit of this principle is shown in the figure below.

Each group of branches is independent of each other. When the LED of one branch fails, it will not affect the other parallel branches. This principle applies to the case where the input voltage is relatively small. The advantage is that the branches do not affect each other (except for short circuits).

3 Constant current drive theory

This principle is the most commonly used LED driving method. The LED controller outputs a current signal. Multiple LEDs are connected in series to form a loop. The current flowing through each LED is the same, so the brightness of the LED is relatively uniform. This principle is most used in the LED lighting industry. Its typical implementation principle is shown in the following figure.

In our daily application, the constant voltage is to drive LED panel light(CC type), LED spot light or other CC type light.

The above picture is a simple constant current source circuit built with a three-terminal voltage regulator. The LEDs are connected in series in the loop, the current flowing is the same, and the brightness remains uniform. But the disadvantage is obvious that as long as one LED is damaged, the other LEDs cannot work.

4 Comparison of advantages and disadvantages of the above three schemes

Constant voltage series drive is suitable for the case of high input voltage. The advantage is that the circuit is simple to implement. The disadvantage is that the LED has to generate a forward voltage drop, and as long as one has an open circuit fault, the other LEDs will be extinguished.

Constant voltage parallel drive is suitable for low input voltage. The advantage is that each LED is independent of each other. After any branch circuit breaks, the normal operation of other branches will not be affected.

The application of constant current drive is the most common. It can drive a large number of LEDs with consistent brightness. The disadvantage is that as long as one fails, all the LEDs cannot work normally.