High side PFET drive is optmised?

[treez]

Hello,
Do you have any improvements for the attached PFET high side drive?
The LTspice simulation is attached, plus schematic.

The high side PFET is getting turned ON/OFF at 20KHz.

 

[Audioguru]

Nothing limits the LED current. The tiny bonding wires in an LED might burn out. Then the LEDs will not light anymore.

 

[Orson Cart]

Q1, is too big and may not switch properly with the level of drive you are providing, there is nothing limiting the current in the LEDS when M3 is on, the 2N7002 id 60V rated, might be a little light for 48V in? Q2 is only 40V C-E (base open), otherwise it might work, what freq?

 

[FvM]

Depends on how fast you want to switch the FET. Gate rise and fall times will suffer from Z-diode capacitance and relative high driver circuit impedance. An active pulse forming circuit, e.g. a CMOS gate or dedicated gate driver at the high side potential would be preferred. Average current consumption is low (Qg*fs + driver quiescent current), so it can be powered by a resistor Z-diode combination.

 

[treez]

Thanks, we will sort out the situation with the led current.
FvM I have changed it to as you suggested...
So regarding the high side drive, do you think this is now the optimal solution?..
(LTspice simulation and schematic attached)

The pfet just has to switch on within one microsecond or so.

 

[treez]

Hello,
This question is related to the above, so I placed it here...

Hello ,


We are using the TC1411 gate driver IC as in the attached circuit, to drive a high side FET at 20KHz. (LTspice simulation also attached).
Due to the way that the common base stage works in translating the gate drive signal to the high side, the actual gate driver input is going between –1V and 10V.

Will the negative input voltage be OK?….The datasheet says the input can spike negative to –5V and still the chip will survive, but does this include the actual gate drive (low) voltage going negative? (to –1V)

TC1411 inverting gate driver datasheet:
**broken link removed**