Hi all,
I am looking for an MOSFET driver (low-side) that has an optocoupler which I can feed 3.3V (as from Raspberry Pi) and the circuit should have Vcc 15V.
Can you help me out, please?

Thank you

 

Hi all,
I am looking for an MOSFET driver (low-side) that has an optocoupler which I can feed 3.3V (as from Raspberry Pi) and the circuit should have Vcc 15V.
Can you help me out, please?

Thank you

I don't think there are any chips that combine an opto-coupler and a MOSFET gate driver. I think it has to be two separate parts. Unless you can figure out how to make one part or the other do both jobs.

 

I am looking for an MOSFET driver (low-side) that has an optocoupler

How fast do you need to switch the MOSFET?

 

Hi all,
I am looking for an MOSFET driver (low-side) that has an optocoupler
Thank you

Something like a CPC1002N ?
How much current is required?

 

Something like a CPC1002N ?
How much current is required?

I don't see how a single solid-state relay will be helpful in driving the gate of a MOSFET. What you want is something that will actively drive the GATE to a level well above Vgs(th) and pull it back down to GND. Maybe you could use a pair of them - is that what you had in mind? If you did that you would need to be very careful NOT to switch both on at the same time. It seems entirely too risky to me.

 

My idea is to eliminate the driver if the current is within the specs.

 

My idea is to eliminate the driver if the current is within the specs.

Will the SSR pull the gate up or down?

 

Eliminate the driver meant the SSR does all the work.

 

Eliminate the driver meant the SSR does all the work.

It escapes me how you plan to use the part. Would a schematic be too much trouble?

 

Photovoltaic MOS driver: APV1122A

This does the job, a bit slow to turn on (0.8 MS) , faster to turn off (0.1 MS)
*Assuming a 1000pF gate capacitance.

 

thanks for all the responses! to be more specific:
-switching speed should be <200Hz i think.
-MOSFET load should be around 75W 220VAC rectified to DC /each

in present I have this, however it works pretty good (mosfet doesn't heat up too much when pwm is 50Hz) however when I don't explicitly set RPI's PWM frequency to 50Hz it heats up rapidly. I can not find what is the default frequency it has when using `wiring pi` so I'm not too convinced about the schema, so if you could validate or propose some changes I'll be thankful.
driver is LTV-3120 and MOSFET shcema:



thank you!

 

Maybe something like the NCD57080

 

Your circuit has no return path for the gate current.

You need to connect the FLOATING 15V supply ground to the FET source terminals.
This is where it gets tricky- the 15V MUST be floating as it interconnects with mains voltage.

 

Your circuit has no return path for the gate current.

You need to connect the FLOATING 15V supply ground to the FET source terminals.
This is where it gets tricky- the 15V MUST be floating as it interconnects with mains voltage.

The 100k ohm does that, right?

 

What is the purpose of the 115 ohm resistor in series with the 15V supply?

And as noted by Sensacell, pin 5 of the driver should be connected to the 15V negative terminal and the source connection of the MOSFETs.
And obviously the 15V must be an isolated supply.

 

What is the part-number of your FETs ?
Can your Micro-Controller source 20mA comfortably ?
.
.
.

.

 

Since the LTV-3120 requires only a maximum of 3mA to power the output stage, the 15V supply could conceivably be derived using a simple half-wave diode rectifier with a 15V Zener shunt regulator, since the power from the 230Vac would around a watt.
An 18k, 2W resistor in series with a 1N4006 diode to a 15V Zener to common will provide about 5mA (3mA for the load and 2mA for the Zener).

With the circuit common being the junction of the two MOSFET sources, the current path for the supply return current to the AC is through the MOSFET substrate diode.

 

Your circuit has no return path for the gate current.

You need to connect the FLOATING 15V supply ground to the FET source terminals.
This is where it gets tricky- the 15V MUST be floating as it interconnects with mains voltage.

true, I just missed it in the schema..

 

The 100k ohm does that, right?

i hoped so.. is it the about right value?

 

Im not sure what your 1k does.