DRIVE A MOSFET FOR DC SWITCH

Thread Starter

Mousivandhossein

Joined Dec 8, 2020
34
Hi friends

I want to switch load 5 A by MOSFET, I designed a circuit but, I don't know it's OK.
Please let me know of anything that is necessary.

Load: a resistance (PF=1)
Voltage 110VDC
The interval of switching is 1 minute and there is not fast switching

1671981159832.png
 

Papabravo

Joined Feb 24, 2006
19,845
That is quite a few parts for an apparently simple application. What is the source of the "command" signal that goes to pin 3 of the Ir2104?
What kind of diode is D01?
Why does the "C" underneath D01 have two values?

You say there is not fast switching, but there should be for a device that does not want to spend an excessive amount of time in the linear region.
How do you plan to implement Res1 so that it can dissipate 550 watts?

Did you engineer this design or are you cutting and pasting?
 

Thread Starter

Mousivandhossein

Joined Dec 8, 2020
34
That is quite a few parts for an apparently simple application. What is the source of the "command" signal that goes to pin 3 of the Ir2104?
What kind of diode is D01?
Why does the "C" underneath D01 have two values?

You say there is not fast switching, but there should be for a device that does not want to spend an excessive amount of time in the linear region.
How do you plan to implement Res1 so that it can dissipate 550 watts?

Did you engineer this design or are you cutting and pasting?
The source of command is a 74HC541 and before that is a microcontroller.
the D01 is 1n4148.
I calculated that 1-10 microseconds is proper for the time of turn on MOSFET and it is safe for MOSFET.
I tried to reduce spike voltage with an increase in the turning on time.
Yes, Res01 is our load.
I engineered the circuit and I don't know that all thing is true.
 

Thread Starter

Mousivandhossein

Joined Dec 8, 2020
34
I assume R? is the load.
Place the IC near the MOSFET and remove most of the Gate parts. Reduce R2 but probably not important.
If you have a resistive load you do not need the RCD snubber. Maybe just the diode across the load as shown if you think the load will have some inductance.
View attachment 283870
Thank you, If we want to switch 4 MOSFETs by a driver and the distance on the PCB is approx 10 cm, in your opinion I must change the circuit
 

DickCappels

Joined Aug 21, 2008
9,619
If the connection to your load is very long or if your load is inductive the spike you mentioned might be capacitive coupling of the gate signal into the drain. An image of the spike compared in time with the gate drive signal would tell you a lot.
 

BobTPH

Joined Jun 5, 2013
6,293
I find it odd to use a gate driver, whose purpose is to supply lots of current for fast switching, then limit the current out to 25mA to slow down switching.
 

Thread Starter

Mousivandhossein

Joined Dec 8, 2020
34
If the connection to your load is very long or if your load is inductive the spike you mentioned might be capacitive coupling of the gate signal into the drain. An image of the spike compared in time with the gate drive signal would tell you a lot.
The connection is a little long and the load is a heater and the entire path of the load circuit is approx 1 meter.
 

Thread Starter

Mousivandhossein

Joined Dec 8, 2020
34
100V 200mA diode seems small. I would have used a 200V 1A fast diode.

If you are switching with 470 ohms of gate resistance, the turn off speed is slow and there probably won't be any spike.
Because the current of gate is small we choose 1n4148 and it's enough fast, in your opinion why is necessary 1A diode?
Exactly, we would like no spike voltage to occur and we limit current the gate current to reduce the speed of turning on
 
Last edited:

Irving

Joined Jan 30, 2016
3,308
A good driver for this is Infineon 1ED44171N01B in a SOT23-5 case. It has 2.6A of drive, so easily good for driving 4x MOSFETs. A single MOSFET with 12v drive will dissipate 1.4W driving a 500W load, so only a small heatsink would be required. The reason your previous MOSFETs overheated was probably driving them with a combnation of one or more of: too slow a rise time, too little gate current or too low a gate voltage.

1672090203031.png


Driving 4 MOSFETs:

1672091258078.png
 
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