LED is a solid semiconductor light source. Its principle of luminescence is essentially the transition of electrons. As a light source with rich colors, LEDs are small in size, high in brightness, long in life, low in voltage, high in safety and fast in response, and at the same time, the output brightness can be adjusted in a wide range. Therefore, it is widely used in daily life, such as billboards, various electronic products, various equipment, handheld devices, etc.

Many LED products now use constant current driving methods to drive LEDs. LED connection methods are also different according to the actual circuit needs. Generally, there are four types of series, parallel, hybrid and array.

1. Series Connection Method

The circuit of this series connection is relatively simple. The current flowing through the LED is consistent and stable when it is working. Since the LED is a current-type device, it can basically ensure that the luminous intensity of each LED is consistent. The circuit adopting this LED connection method is simple and convenient to connect. But there is also a fatal shortcoming, that is, when one of the LEDs has an open-circuit failure, it will cause the entire LED string to go out, which affects the reliability of use. This needs to ensure that the quality of each LED is excellent, so that the reliability will be improved accordingly.

It is worth noting that if the LED constant voltage drive power supply is used to drive the LED, when a certain LED is short-circuited, the circuit current will increase. When a certain value is reached, the LED will be damaged, which will cause all the subsequent LEDs to be damaged. However, if the LED constant current drive power supply is used to drive the LEDs, when a short-circuit occurs in a certain LED, the current remains basically unchanged, which has no effect on the subsequent LEDs.

2. Parallel Connection Method

When the LEDs are connected in parallel, the voltage on each LED is equal. But the current is not necessarily equal, even if it is the same model, the same specification and batch of LEDs. This is due to the manufacturing process and other reasons. This kind of parallel connection circuit is relatively simple, but the reliability is not high, especially when the number of LEDs is large, the possibility of failure is higher.

It is worth noting that the voltage required for the parallel connection is lower, but because the forward voltage drop of each LED is different, the brightness of each LED is different. In addition, if one LED is short-circuited, the entire circuit will be short-circuited, and the other LEDs will not work properly. For a certain LED open circuit, if a constant current drive is used, the current distributed to the remaining LEDs will increase, which may cause damage to the remaining LEDs. However, the use of constant voltage drive will not affect the normal operation of the entire LED circuit.

3. Hybrid Connection Method

Hybrid connection refers to a combination of series and parallel connections. First connect several LEDs in series, and then connect them in parallel to both ends of the LED drive power supply. When the LEDs are basically consistent, using such a connection method makes the voltages of all branches basically the same, and the current flowing through each branch is basically the same.

It is worth noting that the use of the hybrid method is mainly used in the case of a large number of LEDs. Because this method ensures that the LED failure in each branch only affects the normal light emission of the branch at most, it improves the reliability compared to the simple series and parallel forms. At present, many high-power LED lamps generally adopt this method, which achieves a very practical effect.

4. Array Connection Method

The main structure of the array mode is as follows: the branch is composed of 3 LEDs as a group, and they are respectively connected to the Ua, Ub and Uc output terminals of the driver. When all 3 LEDs in a branch are normal, the 3 LEDs emit light at the same time. Once one or two of the LEDs fail and open circuit, at least one of the LEDs can be guaranteed to work normally. In this way, the reliability of each group of LEDs can be greatly improved, and the overall reliability of the entire LED can be improved. Using this method requires multiple sets of input power sources, the purpose is to improve the reliability of the LED work, reduce the overall circuit failure rate.