Hi everyone.

Let’s say you need to build a three-phase inverter with the standard 48V DC bus, and that you need to drive MOSFETs at a frequency matching that of the control algorithm (let’s say 40 kHz field oriented control). Let us also assume that the current in the phases is less than 5A.

There are so many gate drivers out there, and I’m finding it a bit difficult to understand the differences and which one is best suited to my needs.

Let’s take a look at these two: 2EDL8124G vs ISL78434

The main features I compared are:
- voltage class
- Voltage HI, LI and supply Vcc
- Isource and Isink
- Turn on/off propagation delay (from LI to LO and from HI to HO)
- qualification (automotive etc.)
- thermal parameters (Rth_jc etc.)
- features: shoot-through, UVLO, dead time control etc.

Since this is the first time I’m dealing with gate drivers and given that these two gate drivers seem very similar to me, so I’m not sure which one to choose.

Can you help me?
What other information do I need to provide?

 

Maybe I should already know this, but do the gate signals need to be isolated?

 

Maybe I should already know this, but do the gate signals need to be isolated?

That’s a good question – no, they don’t need to be insulated (I forgot to mention that)

 

I have not used either part. The EiceDRIVER™ 2EDL8x2x is simple and I know how it works very well. I have been using parts in the 350V to 800V range.

Now I see how the ISL78434 works. There is a pull up pin and a different pull-down pin. They can be tied together. Or you can have a turn on resistor and a turn off Gate resistor. I have used that at high-speed switching, you are running at only 40khz. There is an enable pin.

I think both parts have the option to turn on both MOSFETs at the same time. There is no override to stop "shoot through". This worries me.

I would choose the 2EDL8 only because of less pins. But if you need enable use the other part.

How are you making the waveforms?

 

I have not used either part. The EiceDRIVER™ 2EDL8x2x is simple and I know how it works very well. I have been using parts in the 350V to 800V range.

Now I see how the ISL78434 works. There is a pull up pin and a different pull-down pin. They can be tied together. Or you can have a turn on resistor and a turn off Gate resistor. I have used that at high-speed switching, you are running at only 40khz. There is an enable pin.

I think both parts have the option to turn on both MOSFETs at the same time. There is no override to stop "shoot through". This worries me.

I would choose the 2EDL8 only because of less pins. But if you need enable use the other part.

How are you making the waveforms?

Hi, thanks for the answer.

1) With "pull-up" and "pull-down" resistors you mean LO_H and LO_L? ..and HO_H and HO_L


If the answer is yes, in what situations are those pins useful?
In other words, under what conditions is it necessary to split the turn-on and turn-off paths of the MOSFET gate?

In my case, I have a 48V DC bus with 4–5A on the motor phases, and I think I’ll use this MOSFET (or something very similar) and with 40kHz frequency ... so I think I do not need them, right?

2) You said "I think both parts have the option to turn on both MOSFETs at the same time. There is no override to stop "shoot through". This worries me."
In che senso?
The ISL78434 datasheet states: (read the last sentence)


3) "How are you making the waveforms?"
If you mean PWM signals at the input, I generate them using a Texas Instruments microcontroller

 

If the answer is yes, in what situations are those pins useful?
In other words, under what conditions is it necessary to split the turn-on and turn-off paths of the MOSFET gate?

There are many different type of switching power supplies. When you get into resonant and the many different type of that resonant things can be different. With out getting into that right now, if you have two different Gate Resistors then you can set the turn on and turn off speed independently. One of the types I have built we turn on the MOSFET when there is 0V from D-S. There is no switching loss on that edge. There is also no need to try to make the MOSFET turn on fast. The other edge might be the one we are struggling with.

Another example is a discontinues flyback supply. The MOSFET turns off at a high current. But the turn on is at zero current. So, the turn on does not need to be very fast.

For years people used a diode and Roff to speed up the turn off edge in this type of supply. With the new low Gate voltage MOSFETs and GaN MOSFETs the turn on voltage is very low. The loss in voltage from the diode is a big problem.

If you mean PWM signals at the input, I generate them using a Texas Instruments microcontroller

At the university every year the students think "software PWM" that is easy. They sometimes leave the MOSFETs all on during power up. (until the software us up and running) Sometimes as they load the registers in the computer, the frequency or phase is very wrong for a short time. I teach to make the hardware keep all the MOSFETS off when the IO pins are in tri-state. (yet no one listens) I also want the MOSFETS off until the PWM values are all loaded.

2) You said "I think both parts have the option to turn on both MOSFETs at the same time. There is no override to stop "shoot through". This worries me."

Here are parts I have used many times. On the front end there is logic so both MOSFETs cannot be on at the same time. There are some parts that have a fixed dead time or have a pin to program how may nS of dead time there is between turn off and turn on.

 

I'll second the use of the SkyWorks parts; I've used Si8233 Hi/Lo-side 4.0A drivers in a 3-phase inverter. Price competitive at 10+ parts and one of the few good for 800v+. Only downside is no (LT)Spice model for them (or no official one AFAIK).

 

What other information do I need to provide?

I can only assume you use 6-MOSFET bridge (based on the chips you looked up) but not what is going to drive the gate drivers? Which MOSFET or IGBT? I have used IR2136, available everywhere and still DIP can be found for prototyping