How to use IC DRIVER HI/LO SIDE HV L6387E

[joker12]

I'm trying to use this high voltage half bridge mosfet driver (L6387E). I've attached a file that shows how I have connected the circuit. I'm just trying to drive two stacked nmos with a small capacitor connected between so I can charge it to my high voltage and discharge it very quickly.

My circuit works fine up to 150V sometimes. I've had the circuit break at 100V and 300V (two different drivers). The driver doesn't work after that. It's rated for 625V. Why won't it work with higher voltage?

The datasheet shows a capacitor between the Vcc pin and the supply voltage. Do I need that? Anything else wrong?

 

[keith1200rs]

My guess is that the problem is to do with shorting the high and low side switches together (pin 6 - OUT). OUT can only be 18V below Vboot. I think that you may be pulling it to ground through the NMOS, but I am not sure (I have not used those sort of chips).

Keith.

 

[joker12]

I think the top source and bottom drain are supposed to be connected. That's the point -- at least for this application and some others. You either pull your load up to HV or down to ground and only one transistor is on at once.

Vboot is rated up to 618V, so OUT is rated to 600V.

I thought of a different solution for my needs, but I still don't know why this chip does not work.

 

[keith1200rs]

Sorry, I think I misinterpreted the data sheet.

Could something be pulling the output above (Vboot-18)? I guess Cboot is supposed to stop that. There was an application note I saw about these types of chip from another manufacturer which listed all the potential problems withthem - I will try to find it.

Keith.

Added after 1 minutes:

Here it is:

https://www.fairchildsemi.com/an/AN/AN-6076.pdf

Keith.

 

[sec]

What is your working frequency.
Which transistor you are driving
The circuit looks ok, (but i don't like the 90pF) be SURE to not drive the hi side and lo side at the same time (there's an internal logic but no deadtime)
Depending on the mosfet, I would use a 0,1uF or 0,33uF as decoupling capacitor and CBoot capacitor.
keep the distance as low as possible, the trace lenght kickback some current in the driver and may blow it !! (it happened to me)
to have good result you may want to track the temperature, the current of your system and the spike created be the mosfet.
Be carfull with the spike, use a differential probe to keep your oscilloscope safe.

 

[Tahmid]

Hi,
Keith, OUT for these chips is equivalent to VS in IR2110, that provides the floating voltage.
Joker12, place a 1k resistor between each MOSFET gate and source and I think you won't have this problem. I think you need to get rid of the 90pF.

Hope this helps.
Tahmid.

 

[~MJS]

place a 1k resistor between each MOSFET gate and source and I think you won't have this problem.

I agree that a gate resistor is a good idea, (and maybe I am wrong here) but 1k seems really high.

Switching losses: P≈Vds*Id*fs*(ton+toff)*1/2, and I think 1k will drastically increase ton and toff. With Vds of several 100V and fs=100kHz, it could mean high switching losses.

The equation I use to determine gate resistance is: Qg/ton=Igate=Vcc/Rgate.