The reason why LEDs are so popular in the market is that they are widely used in display lighting and signal indicators because of their high efficiency and low energy consumption. However, the wide range of application fields also poses challenges to the environmental adaptability of the LED itself. When working outdoors, the driving circuit of the LED is very susceptible to the impact of overvoltage and overcurrent, which can cause malfunction or damage, and cause damage to property and personnel. Therefore, when producing an LED power supply, the complexity of its working environment must be considered, and a protective design should be made to reduce the incidence of failure. WINSOK made a simple discussion on how to protect the LED drive circuit.

Friends who are familiar with LED circuits must know that LED drive circuits generally consist of the following parts, including AC input, rectification, DC/DC conversion, and other modules. The protection measures need to be adjusted according to different modules. For example, each module and current need different effective protection measures in the case of surges.

LED drive circuit surge protection application

The surge protection scheme at the AC input end of the AC power supply can be designed with a varistor (MOV) or a gas discharge tube (GDT/SPG) combination. In the case of grounding, the concept of simultaneous protection of differential common mode can be adopted, and a varistor (MOV) in parallel between LN can effectively suppress the surge overvoltage generated by differential mode and protect the subsequent circuit , Using MOV or MOV+GDT/SPG to ground circuit connection between L/N-PE can effectively discharge the common-mode surge energy to the ground, preventing the surge from being introduced to the subsequent circuit and causing damage; If the power supply does not have a ground wire, a varistor can be directly connected in parallel between the LN wires for differential mode protection.

In order to avoid the possibility of short-circuit failure and ignition of the MOV protection element after the protection fails, TMOV or PMOV can be used for protection. The AC withstand voltage of the above MOV should be at least 1.2~1.4 times higher than the maximum AC working voltage of the line to avoid misoperation. When the discharge tube GDT/SPG is used at the same time, the lower limit of the discharge tube breakdown voltage must be at least Higher than the maximum peak voltage of the circuit, the withstand current must be selected according to the requirements of its own surge level to meet the requirements of the surge test standard.