Hi electronic experts, does a MOS-FET like this one IRF 3708 where the datasheet shows that it has an internal freewheeling-diode need a additional external freewheeling diode for effective protection against flyback-voltage-spikes caused by inductive loads? [grafik] best regards Stefan

That internal diode exists with every MOSFET. In most cases it can not replace an external diode over the inductive load.

In a single MOSFET circuit the body diode (as its called) is useless for protection since the free-wheel diode needs to go across the load. In an H-bridge circuit the diodes are useful as each diode protects another MOSFET. Sometimes for extra efficiency external Schottky diodes are added to an H-…

[image] MarkT: Sometimes for extra efficiency external Schottky diodes are added It depends on what "efficiency" means to you. Diodes allow the current to persist, for some time, for smooth use with PWM. For fast turn-off time instead RC snubbers perform better.

[image] DrDiettrich: It depends on what "efficiency" means to you. Well for instance the engineers designing large power converters really like to see 98.5% efficiency over 97.5% efficiency(*) because that's a huge 40% reduction in heat to get rid off - thermal management is a large proporti…

[image] MarkT: engineers designing large power converters That "efficiency" is not applicable to PWM applications. Please read and understand what I wrote in #5.

[image] StefanL38: does a MOS-FET like this one IRF 3708 where the datasheet shows that it has an internal freewheeling-diode Just to underline what the others have said: that is NOT a freewheeling diode. It cannot perform that function.

In what application has a snubber better efficiency than a H-bridge?

Whenever fast turn-off is required.

And that is? Assuming you are driving inductive load H-bridge can return the energy to the supply. RC Snubber dissipates it in the resistor.

Does a MOS-FET with integrated freewheeling-diode need another external freewheeling diode

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Paul_B January 10, 2022, 10:02pm 3

Stefan, you apparently do not understand what a "freewheeling-diode" does.

Perhaps you need to research it a bit - this thread and this may I hope, help.

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Does a MOS-FET with integrated freewheeling-diode need another external freewheeling diode

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