LED power supply protection scheme and common causes of damage

As a new green lighting technology, high-power white LED has the advantages of high light conversion efficiency, low energy consumption, long service life, and no need for maintenance, and is gradually being applied in various lighting fields. The long lifespan of LED is based on its safe working environment. For LED lighting, there are two main threats that affect its lifespan: first, overvoltage shock, which means that the current applied to the LED exceeds the maximum rated current specified in the LED technical data manual, including overvoltage caused by overvoltage; Another type is overheating damage. These damages can manifest as immediate device failure or occur long after an overcurrent impact event, shortening the lifespan of the LED.

The causes of damage to LED lighting fixtures

The failure of LED lighting fixtures is due to the failure of the power supply and driver, as well as the failure of the LED components themselves. Usually, the damage to LED driver power supply and driver comes from the over current shock (EOS) of the input power supply and the open circuit fault at the load end. The overvoltage impact of the input power supply often causes damage to the driving chip in the driving circuit, as well as breakdown damage to passive components such as capacitors. A short circuit fault at the load end may cause overcurrent driving in the driving circuit, which may result in short circuit damage or overheating damage caused by short circuit faults. The failure of LED devices themselves mainly occurs in the following situations.

1. Electrostatic discharge events

Electrostatic discharge (ESD) damage is currently the most common transient overvoltage hazard in the manufacturing, transportation, and application of highly integrated semiconductor devices, and LED lighting systems must meet the "human electrostatic discharge mode" 8kV contact discharge standard of IEC61000-4-2 to prevent the system from potentially causing overvoltage shock failure during electrostatic discharge.

The performance of the LED PN junction array will decrease or be damaged, as shown in Figure 2. The internal failure of LED chips caused by the discharge path of ESD events may only be partial functional damage, and in severe cases, it can also lead to permanent damage to the LED.

2. Transient overcurrent events

Transient overcurrent events refer to the current flowing through an LED exceeding the maximum rated current specified in the LED technical data manual. This may be caused directly by high current or indirectly by high voltage, such as transient lightning strikes, transient switching noise from switching power supplies, and overvoltage events caused by grid fluctuations. These events are transient and have extremely short duration, commonly referred to as spikes, such as "current spikes" or "voltage spikes". The situations that cause transient overcurrent events also include LED power on or transient overcurrent during live plugging and unplugging.

For LED lighting in cars, The transient load surge impact of ISO7637-2 is an important threat to its normal operation.

The failure mode of LED after being subjected to electric shock is not fixed, but it usually leads to damage to the welding wire, as shown in Figure 1. This type of damage is usually caused by significant transient overcurrent. In addition to causing the welding line to burn out, it may also cause damage to other parts near the welding line, such as sealing materials.

Common causes of damage to LED lighting fixtures and protection measures

For LED lighting designs where nearly 80% of energy is converted into heat, heat pipes