Hi,

Attached you can find BJTs pair used as gate driver for that MOSFET. Is that reliable over the gate drivers chips nowadays like TC4427, FOD3120, and much more over there?

 

Today's gate drivers have lots of protections, read the feature set on this
one -

http://www.ti.com/product/ucc27712

Regards, Dana.

 

Today's gate drivers have lots of protections, read the feature set on this
one -

http://www.ti.com/product/ucc27712

Regards, Dana.

Briefly looking into the specs it says
"High-Side Low-Side Gate Driver", what does it mean by high and low side in that case? How can I use that IC to drive a power DC motor? Also, some gate drivers have isolation, when do I decide to use a gate driver with isolation or not?

 

High/Low side, think bridge for changing current direction thru load.

Insofar as isolation, take a look at this description - https://www.mouser.com/applications/motor-gate-drive-isolation/


Regards, Dana.

 

High/Low side, think bridge for changing current direction thru load.

Insofar as isolation, take a look at this description - https://www.mouser.com/applications/motor-gate-drive-isolation/


Regards, Dana.

Thank you. For now I do not want to control direction. I just want the motor in one direction.

 

Thank you. For now I do not want to control direction. I just want the motor in one direction.

An excellent driver to use in your applications would be the MC34151. You can control up to two Mosfets with it, and is capable of performing high frequency PWM if you want.

 

An excellent driver to use in your applications would be the MC34151. You can control up to two Mosfets with it, and is capable of performing high frequency PWM if you want.

Is there a chip which only have one gate driver? The MC34151 contais two, that is, dual mosfet drivers. Mostly I see they always include two drivers. But if I'm using just one, then the other is unused.

 

There are some single gate drivers. The Fairchild FAN3111 is one such driver in an SOT23-5 package. Don't know if it is obsolete. Use the parametric search on DigiKey.com.

You will find many IC's (logic in particular) that have many more identical units than you need. If size is not critical, there is no disadvantage to getting them and often they are cheaper.

 

Thank you. One last question: different gate drives chips have different output current capability. In my design, how do I decide which one should I choose? Does it depend on the transistor that I'm going to use? Do I have to look into the transistor datasheet and see gate current so that I can choose the proper gate driver?

 

Thank you. One last question: different gate drives chips have different output current capability. In my design, how do I decide which one should I choose? Does it depend on the transistor that I'm going to use? Do I have to look into the transistor datasheet and see gate current so that I can choose the proper gate driver?

Yes, it can depend on the mosfet you are using (i.e, gate capacitance). Assume you have a gate resister (Rg), then the turn on time can be calculated from the equation for charging a capacitor. Typically for what I was doing, the drivers were rated at 3A or 6A. The FAN3111 at 1 A will probably be OK for many mosfets that are not switched particularly fast. It is a whole lot better than the 25 mA available from a typical MCU.

One of your early schematics shows a 22 Ω gate resistor. At 10V, that will allow a little less than 0.5 A.

 

Yes, it can depend on the mosfet you are using (i.e, gate capacitance). Assume you have a gate resister (Rg), then the turn on time can be calculated from the equation for charging a capacitor. Typically for what I was doing, the drivers were rated at 3A or 6A. The FAN3111 at 1 A will probably be OK for many mosfets that are not switched particularly fast. It is a whole lot better than the 25 mA available from a typical MCU.

One of your early schematics shows a 22 Ω gate resistor. At 10V, that will allow a little less than 0.5 A.

Thank you. When you say "The FAN3111 at 1 A will probably be OK for many mosfets that are not switched particularly fast", you mean the PWM frequency, right?. As for Motor control I've seen low pwm frequency like 50-100 Hz and higher ones like 20-30 kHz. That's another thing I have to consider in my design.

 

I've seen low pwm frequency like 50-100 Hz and higher ones like 20-30 kHz.

Even 30kHz is relatively slow for switching a MOSFET by today's standards.

 

Thank you. When you say "The FAN3111 at 1 A will probably be OK for many mosfets that are not switched particularly fast", you mean the PWM frequency, right?. As for Motor control I've seen low pwm frequency like 50-100 Hz and higher ones like 20-30 kHz. That's another thing I have to consider in my design.

One often avoids the audible range because of the noise. Motors become little speakers.

 

Selecting a gate driver -

https://www.electronicproducts.com/Analog_Mixed_Signal_ICs/Selecting_the_right_MOSFET_driver.aspx

http://www.powerguru.org/simple-tools-for-mosfet-driver-selection/

https://www.google.com/url?sa=t&rct...10069cb90f49&usg=AOvVaw1Bg8LlePSwgAFuFA4GOFxj

https://www.google.com/url?sa=t&rct.../slua618.pdf&usg=AOvVaw2iuo-DEdY01npKFn-UdmVA

Regards, Dana.

 

Sage advice, jpanhalt -- I designed a pwm LED dimmer for an RV shop.
In showing the prototype, an office clerk popped into the door with "What's that screaming noise"?
I powered the proto down and she went "Ah, Better" Then, powered back up was "Ouch, it's back".
I'd set the pwm freq at ~ 16k, WAY above what I can hear (drag racing etc)
Pretty easy fix, put freq @ 26k.

So, Any driven object can find ways to emanate circuit generated frequencies.
Just make them Well above audible.... <<<)))

 

Selecting a gate driver -

https://www.electronicproducts.com/Analog_Mixed_Signal_ICs/Selecting_the_right_MOSFET_driver.aspx

http://www.powerguru.org/simple-tools-for-mosfet-driver-selection/

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&cad=rja&uact=8&ved=0ahUKEwis8sTWlKfbAhXBzlMKHd55Bk8QFghUMAM&url=https://www.infineon.com/dgdl/Infineon-Selection_Guide_Gate_Driver_ICs-SG-v01_00-EN.pdf?fileId=5546d46250cc1fdf015110069cb90f49&usg=AOvVaw1Bg8LlePSwgAFuFA4GOFxj

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=7&cad=rja&uact=8&ved=0ahUKEwis8sTWlKfbAhXBzlMKHd55Bk8QFgh8MAY&url=http://www.ti.com/lit/ml/slua618/slua618.pdf&usg=AOvVaw2iuo-DEdY01npKFn-UdmVA

Regards, Dana.

Thanks, I will read them.

A question.. some gate drivers have optoisolation, when should I consider a gate driver with isolation included?

 

Its a safety issue, keep user isolated from motor buss voltages.

I always saw it in 440V systems, most of the time in 220, sometimes in 110.
In any system where you do not want galvanic ground currents from different
ground domains. Or where there is a potential for that to happen.

Regards, Dana.