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Analysis of LED Lighting Protection Technology for AC Power Supply


The new heat dissipation enhanced MOV can illustrate the protection of many low power systems from over-current, over-temperature and over-voltage failures, including lightning stroke, ESD surge, neutral loss, incorrect input voltage and power induction. These devices help protect the AC power LED lighting system, as shown in Figure 1.



Integrated devices help reduce the number of components

Under normal operating conditions, the AC line voltage applied on MOV will not exceed the maximum AC root-mean-square voltage (VAC RMS) rating of the device, and it is assumed that as long as the transient energy does not exceed the maximum rating of MOV, short-term transient events can be clamped at an appropriate voltage level. However, persistent abnormal overvoltage/limited current conditions (such as neutral loss) may cause MOV to enter a thermal runaway state.

A thermal cut-off (TCO) device is usually placed in series with the MOV to protect the MOV from overheating damage. Typical line voltage transient protection schemes can also integrate an overcurrent protection element (such as a fuse) to protect the system from damage caused by overcurrent overload beyond a predetermined level.
Overflow conditions and thermal runaway
Tyco Electronics's AC 2Pro. device integrates a Polymer Positive Temperature Coefficient (PPTC) component and a MOV component into a thermal protection device to provide a redesignable function under overcurrent or overvoltage. This integrated device method can help manufacturers meet the requirements of IEC61000-4-5 and IEC60950 industries.

Unprotected standard MOV components are usually limited to 275 VAC RMS for general input voltage range. In the case of neutral losses, they may have negative consequences due to overheating, even if fuses or power resistors are used upstream of the circuit.

PPTC components in AC 2Pro devices help to prevent thermal runaway, keep the surface temperature of the rheostat below 150 degree C and prevent the device from reaching unsafe temperature caused by overvoltage transient.

Working principle

Although the AC line voltage applied to a MOV usually does not exceed the maximum sustained operating voltage rating of the device, overvoltage transients beyond these limits may occur. 2Pro device integrates PPTC technology with MOV. When MOV is under continuous overvoltage for a long time, it can improve the overcurrent and thermal protection capability.

In the case of overvoltage transient, the neutral loss event shown in Figure 2 will cause PPTC components in 2Pro devices to heat up, jump off and enter a high impedance state, which indicates that the risk of failure of MOV devices is reduced.



Yiwu Fuwei e-commerce firm (IACS Co., Limited) is a very professional Led manufacturer who produces high quality outdoor led light. Our popular products are solar led lights, UFO lights, underwater lights and so on. If you have any question about the led product, please feel free to contact us.