Body
Good post onielson! The first one was fine.
protecting the Gate is very important, maybe a ~20 volt Zener, diode, (or back to back Zeners) and resistor. Seem to work for me.I still like the PVI5050 as (Gate input) it is stand alone and can be run with a micro-controller. It is much slower..
On Thursday, July 5, 2018, 4:50:36 p.m. MDT, [email protected] [EVGRAY] <[email protected]> wrote:
The message got truncated and the attachment discarded!
Here's another try.
Hi Sven,
Don't put ferrite beads on the gate circuit as they add inductance. Try to avoid inductance by making the distance between the gate driver and the gate as small as possible an minimize any area between the wires that act like a coil winding adding inductance. The gate-source is a capacitor. Adding inductance makes it an LC-tank which makes oscillations when storing energy. The oscillations are amplified at the drain. Also the inductive kickback from any inductance can go above the gate-source breakdown voltage which degrades and destroys the MOSFET sooner or later. By adding extra capacitance in parallel to the gate-source capacitance slows down the MOSFET as the drain signal follows the gate signal. The series resistor at the gate is for absorbing the energy of the formed LC-tank to prevent oscillations of the gate and thus also oscillations on the drain.
Opto couplers are slow devices. The TLP250 has a delay of 0.5 us and a max frequency of 25 kHz.
A fuse normally isn't fast enough to protect semiconductors from destruction. Use an electronic protection that removes the gate signal to shut off the device. For over voltage protection use some kind of snubber active or passive. A crowbar protection made by using a thyristor (SCR) that shorts out the voltage supply rails and blows a fuse is an effective way to prevent over voltages.
'Fundamentals of MOSFET and IGBT Gate Driver Circuits:' (http://www.ti.com/lit/ml/slua618/slua618.pdf).
Just follow those rules to make a good gate driver. If not doing that all kinds of trouble may arise.
If the impedance of the capacitors are less than that of B2 the current mainly takes the path shown. If R2 is omitted this may cause ringing when charging the gate capacitance. R2 has to absorb the energy to prevent oscillations in the tank formed by the inductance of the two loops and the capacitance of the gate-source capacitor. For fast response R2 is chosen for critical damping which means no ringing.
Regards
Ole
---In [email protected], <onielsen@...> wrote :
Hi Sven,
Don't put ferrite beads on the gate circuit as they addinductance. Try to avoid inductance by making the distance between thegate driver and the gate as small as possible an minimize any areabetween the wires that act like a coil winding adding inductance. Thegate-source is a capacitor. Adding inductance makes it an LC-tank whichmakes oscillations when storing energy. The oscillations are amplifiedat the drain. Also the inductive kickback from any inductance can goabove the gate-source breakdown voltage which degrades and destroys theMOSFET sooner or later. By adding extra capacitance in parallel to thegate-source capacitance slows down the MOSFET as the drain signalfollows the gate signal. The series resistor at the gate is forabsorbing the energy of the formed LC-tank to prevent oscillations ofthe gate and thus also oscillations on the drain.
Opto couplers are slow devices. The TLP250 has a delay of 0.5 us and a max frequency of 25 kHz.
Afuse normally isn't fast enough to protect semiconductors fromdestruction. Use an electronic protection that removes the gate signalto shut off the device. For over voltage protection use some kind ofsnubber active or passive. A crowbar protection made by using athyristor (SCR) that shorts out the voltage supply rails and blows afuse is an effective way to prevent over voltages.
'Fundamentals of MOSFET and IGBT Gate Driver Circuits:' (http://www.ti.com/lit/ml/slua618/slua618.pdf).
Just follow those rules to make a good gate driver. If not doing that all kinds of trouble may arise.
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