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WAYON High-Voltage Super Junction MOSFET, Solving LED Power Surge with Ease

As a new lighting source, LED has various advantages such as high energy efficiency and long lifespan. It has been widely used in various lighting scenarios such as LED display, automotive electronics, lifestyle lighting, etc. LED constant current driving characteristics require a specific AC/DC constant current driving power supply. Generally, in order to improve the energy efficiency, a single-stage PFC topology is used by LED driving power supply.


Figure 1 Single-stage PFC topology

As shown in figure 1, there is no high-capacity electrolytic capacitors between the rectifier bridge at the input end and high-voltage MOSFETs in single-stage PFC topology. In the event of a lightning surge, the surge energy is easily transmitted to the MOSFET, and the VDS of the high-voltage MOSFET is easily exceeded, at which point the MOSFET is prone to avalanche. In switching power supplies, R&D engineer requires MOSFETs to have as few or no avalanches as possible.

Avalanche of a MOSFET is a phenomenon where the voltage exceeds the rated withstand voltage of the drain-source terminal and breakdown occurs. Figure 2 shows the schematic diagram of the safe operating area of a 600V MOSFET, with the red line marking the right boundary of the safe operating area. When the avalanche occurs, the voltage across the drain source exceeds the rated BVDSS and is accompanied by current flowing through the drain source, at which point the MOSFET operates in the right area of this boundary, beyond the safe operating area (SOA).


Figure 2 SOA of a 600V MOSFET

Figure 3 shows the avalanche measurement circuit and waveform. Once the safe operating area is exceeded, the MOSFET power consumption will increase greatly. The left figure shows the standard circuit for avalanche testing, and the right one shows the operating waveform during an avalanche. MOSFETs enter an avalanche state during shutdown due to high VDS voltages. During the avalanche, the drain-source voltage and current exist simultaneously, and the resulting transient power consumption reaches several KW, which can greatly affect the reliability of the entire power supply. Moreover, during the avalanche, it must be ensured that its channel temperature does not exceed the rated channel temperature, otherwise it will easily lead to over-temperature failure of the device.


Figure 3 Avalanche Measurement Circuit and Waveform

So, how can avalanche damage be avoided by MOSFET application? From the surge protection point of view, power supply engineers can increase the specifications of the AC input surge protection components, for example: increasing the size of varistor, choosing for lower residual voltage varistor or increasing the RCD surge absorption circuit, so that the AC front-end protection components can absorb most of the surge energy and reduce the surge residual voltage. Moreover, choosing MOSFETs with higher ID or higher voltage withstand can avoid its own avalanche. However, higher ID often means higher costs, that makes the choice of higher voltage withstand a simpler, safer and more cost-effective solution.



Figure 4 800V MOSFET Surge Test Waveform
CH2 VDS (Blue 200V/div)
CH3 IDS (Purple 1A/div)


Figure 5 650V MOSFET Surge Test Waveform
CH2 VDS (Blue 200V/div)
CH3 IDS (Purple 1A/div)

Figure 4 shows the waveform of LED driving power supply with 800V MOSFET and figure 5 the waveform of 50W LED drive power supply with 650V MOSFET when surge occurs. The surge test conditions of both are identical. The moment when the VDS waveform suddenly rises in figure 4 and figure 5 is the moment when surge occurs. The maximum VDS voltage in figure 4 is 848 V and the maximum VDS voltage in figure 5 is 776 V. The avalanche consumes energy from the surge. This phenomenon is more obvious during the 650V MOSFET shutdown in figure 5 where there is still a large drain source current flowing through. The 800V MOSFET in figure 4 has zero current during shutdown and no avalanche occurs, indicating that the surge energy transferred to the device is not sufficient to cause an avalanche. It can be seen that the use of MOSFETs with 800V withstand voltage in this power supply greatly improves the surge safety margin and prevents the device from avalanche.

In applications such as LED driver power supplies and industrial control auxiliary power supplies, power supply engineers can choose MOSFETs with higher withstand voltages when designing surge protection. Devices with high withstand voltages can block surge energy at the AC input, allowing the input port's MOV protection device to absorb it and avoid MOSFETs exceeding the safe operating area. This can greatly improve the surge protection capability of the entire power supply.

As a green lighting product in the 21st century, LEDs are replacing traditional light sources in large quantities. Relying on the huge LED market, domestic devices in the field of SJ MOSFETs have great potential to replace imported brands. Combined with the needs of the market and customers, WAYON is continuing innovate in product process and packaging and has achieved more complete product series and specifications by aiming at the common specifications of more than 800V voltage withstand in LED lighting field.




In the above table, 03N80M3 and 05N80M3 can be used in auxiliary power supplies with high surge requirements, such as 3-5W auxiliary power supplies for industrial 380VAC input. Compared with 650V specifications, its surge capability is significantly improved; compared with the flat process 2N80 specifications, the on-state resistance is significantly reduced, and the thermal rise and efficiency are significantly improved.