Design and application of LED and LED driver

LED has been widely used in lighting and decorative lighting products. When designing LED lights, it is necessary to consider what kind of LED driver to use , and the LED as the serial-parallel connection of the load, and reasonable design to ensure the normal operation of the LED.

1, LED uses all series

The LED driver is required to output a higher voltage. When the consistency of the LEDs is large, the voltages distributed across the different LEDs are different. The current through each LED is the same, and the brightness of the LEDs is the same.

When a certain LED is poorly short-circuited, if a regulated drive is used (such as the commonly used RC mode), since the output voltage of the driver does not change, the voltage across the remaining LEDs will rise and the driver output current will increase. Will increase, resulting in easy damage to all remaining LEDs. If constant-current LED driving is used, when a certain LED is poor in quality, the output current of the driver will remain unchanged, and the remaining LEDs will not be affected.

When the quality of a certain LED is broken, the LEDs connected in series will not light up. The solution is to connect a Zener tube in parallel with each LED. Of course, the conduction voltage of the Zener tube needs to be higher than the LED's conduction voltage, otherwise the LED will not light up.

2, LED adopts all parallel mode

The LED driver is required to output a large current with a low load voltage. The voltages distributed across all LEDs are the same. When the LEDs have a large difference in consistency, the current through each LED is inconsistent and the brightness of the LEDs is different. LEDs with better consistency can be selected for products with lower power supply voltages (such as solar or battery powered).

When a certain LED is poorly disconnected, if a regulated LED driver (such as a regulated switching power supply) is used, the driver output current will be reduced without affecting the rest of the remaining LEDs. If a constant current LED driver is used, since the output current of the driver remains unchanged, the current distributed to the remaining LED will increase, resulting in easy damage to all LEDs. The solution is to connect LEDs as much as possible. When one LED is disconnected, the remaining LED current is not large enough to affect the normal operation of the remaining LEDs. Therefore, when the power LED is used as a parallel load, it is not suitable to use a constant current driver.

When a certain LED is poorly short-circuited, then all the LEDs will not light up, but if there are more LEDs in parallel, the short-circuited LED current is large enough to burn the short-circuited LEDs.

3, LED adopts hybrid mode

In products that require more LEDs, if all LEDs are connected in series, the LED driver will be required to output a higher voltage. If all LEDs are connected in parallel, the LED driver is required to output a large current. Connecting all or three LEDs in parallel not only limits the amount of LEDs used, but also increases the load current of the parallel LEDs and increases the cost of the drivers. The solution is to use a hybrid approach.