Hi All,

I am wondering if this is a sufficient way to provide power to Vdd for this gate drive IC. Just using a Zener diode and cap for transient response support for the gate drive.

 

2N7002 doesn't need much gate drive. What's the spec on your 1H inductor as that will determine how much gate drive is needed.

 

Series resistance of the inductor is important. Otherwise the current will keep increasing for ever (or until the 2N7000 vapourises)

 

I apologize, that is not the correct PN for the FET. I am using a power MOSFET

 

I apologize, that is not the correct PN for the FET. I am using a power MOSFET

Without any series resistance, it will just take longer before it vapourises.

 

What MOSFET? But spec of inductor is critical as is your expected frequency of switching. Without that info,can't advise.

 

Thanks all for the input, here is an updated schematic with the correct part numbers for the gate driver and fet along with the inductance and internal resistance. I am mostly concerned with the 15Vzener and cap being able to properly supply the gate drive.

 

What speed is the PWM. The diode 1N4007 is very slow 2uS. Look at the UF4002 50nS. I know it is not in production now but look for something like it. You only need 100V diode not 1000V.

 

The current required for the driver is approximately equal to the driver’s quiescent current, plus the product of the MOSFET’s gate charge and the switching frequency.
if that current is less than the current through your 1k resistor, you are OK, but don’t forget that the zener has to pass the rest of the current and will dissipate some power.

 

Put a 0.1uF ceramic capacitor across pins 5-8 on U2. C1 is not good for high current.
I often use a 0.01uF at the IC, A 1 to 10uF ceramic close and an ele cap anywhere.

 

Why have you chosen that MOSFET? Do you really need a 1700v device?

 

All we can do is guess until the questions in post #6 are answered. It could be that no gate driver is necessary.

 

The current required for the driver is approximately equal to the driver’s quiescent current, plus the product of the MOSFET’s gate charge and the switching frequency.

Exactly this. That’s why I bolded the statement.
With high gate charge Mosfets, like high voltage devices, and high switching frequencies, I have measured currents close to 100 mA.

 

Why have you chosen that MOSFET? Do you really need a 1700v device?

In terms of spec, it's about the furthest you can possibly get from the 2N7002!

 

In terms of spec, it's about the furthest you can possibly get from the 2N7002!

Its an awful device. 450mOhm Rds(on), 5A Id continuous, and, oddly for a TO-247 package, a 1.8°C/W junction to case thermal resistance (most are around 0.2°C/W).

I can't make their SPICE model work.

 

Put a 0.1uF ceramic capacitor across pins 5-8 on U2. C1 is not good for high current.
I often use a 0.01uF at the IC, A 1 to 10uF ceramic close and an ele cap anywhere.

highest switching speed will be 500Hz, and pulse width about 10%, what does the cap between 5 and 8 do? maybe a 1000uF for C1?

 

Here is the updated schematic, realized cap on 5-8 is a bypass cap

 

highest switching speed will be 500Hz, and pulse width about 10%, what does the cap between 5 and 8 do? maybe a 1000uF for C1?

Then you probably don’t need a gate driver if you pick an appropriate MOSFET.

What is the voltage and current capability of the PWM input?

 

if I don't use a gate driver will that not affect the FET's ton and toff?

 

if I don't use a gate driver will that not affect the FET's ton and toff?

Not if you have sufficient drive and choose a sensible MOSFET with a reasonably low gate charge. What is the source of your PWM signal?