PMOS drives PTC heating, MOS heats and smokes

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Hello team, I'm designing a product using Infineon's PMOS (IRFR6215TRLPBF). MOS is a DC switch to drive the PTC heater for a long time. The PTC heater parameters are 24VDC, 80W. The schematic diagram is as follows. Now the PMOS gate voltage is controlled with an optocoupler. A few seconds after opening, the MOS starts to smoke and get hot. Change the voltage divider resistor R16 to 3K, and the problem still exists. Can you help me analyze the problem or make some comments, thank you team.

smartconx_target@Q!w2e3r4t5y6u7i8o9p0||/t5/MOSFET-Si-SiC/PMOS%E9%A9%B1%E5%8A%A8PTC%E5%8A%A0%E7%83%AD-MOS%E5%8F%91%E7%83%AB%E5%86%92%E7%83%9F/td-p/646827

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Hello @yanxiaoxiao,

The driving current of the Mosfet is too small, and it works in the linear region for too long, and the conduction resistance in this range is very large, so the heating is serious. You can use an oscilloscope to measure the Mosfet's Vgs and Vds waveforms.

smartconx_target@Q!w2e3r4t5y6u7i8o9p0||/t5/MOSFET-Si-SiC/PMOS%E9%A9%B1%E5%8A%A8PTC%E5%8A%A0%E7%83%AD-MOS%E5%8F%91%E7%83%AB%E5%86%92%E7%83%9F/m-p/647399

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Translation_Bot
Community Manager
Community Manager
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Hello @yanxiaoxiao,

The driving current of the Mosfet is too small, and it works in the linear region for too long, and the conduction resistance in this range is very large, so the heating is serious. You can use an oscilloscope to measure the Mosfet's Vgs and Vds waveforms.

smartconx_target@Q!w2e3r4t5y6u7i8o9p0||/t5/MOSFET-Si-SiC/PMOS%E9%A9%B1%E5%8A%A8PTC%E5%8A%A0%E7%83%AD-MOS%E5%8F%91%E7%83%AB%E5%86%92%E7%83%9F/m-p/647399

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