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Diode protection for mosfet and ic

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Nihaludeen

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I am working on bldc controller, I knew that flyback diode should be used across the mosfet( drain to sourse).
1. But how can I choose the diode, is in4148 is enough? 2. And for mosfet's gate protection ,can we use zener diode across gate to sourse?
3. And for ir2110 , diode parallel with resistor is enough? For ic protection from mosfet.
4. Inverter circuit has 3 pairs of mosfet's ( high and low), each pair gives output phase for bldc motor. What should be kept between the mosfet phase and bldc motor phase?
5. And Is optocoupler is better to use on micro controller output to gate driver? Or any other method is there for controller protection?
Sry if I am asked anything wrong, advance thanks

Motor spec:
36v 10amp

images.png
 

Hi,

1. But how can I choose the diode, is in4148 is enough?
I wonder why you choose a "big" 1F4007 diode for driving the gate....which needs only some mA of average current.
..and on the other side you want to choose a "small" 300mA signal diode as flyback diode on a 10A rated motor....

1) --> flyback diode: it needs to widthstand peak motor current as repititive peak diode current. And it needs to widthstand motor_power_supply voltage plus some headroom.
Please check if your BLDC windings are connected inside the motor. Depending on internal wiring the "open" winding may produce some voltage that must not be shorted externally by a freewheel diode. In this case better use a zener across the MOSFET (rated with higher than twice the motor_power_supply voltage)

2) --> mosfet protection: in your circuit it is not needed.
* But you need a good PCB layout for low impedance loops:
* GND - COM - LO - GATE - SOURCE - GND
* GND - VS - HO - GATE - SOURCE - GND
*...and I recommend to increase 1k --> 10k.

3) --> the UF4007 diode is not needed for the IR2110. It is needed to quickly discharge the gate. Usually in half bridge configuration to avoid cross conducting of high side FET and low side FET. You may omit the UF4007 diodes here. It is no protection diode.

4) --> your circuit shows low side MOSFETs only. Show your complete circuit.

5) --> optocoupler is for isolation (it is no driver). If you need isolation, then use an optocoupler
--> driver is fro driving a MOSFET´s gate. Use it in any case.
--> controller protection: nothing needed. What is your concern?

Don´t rely on hobbyist´s circuits you find in the internet. Go to the MOSSFET_manufacturer or driver_manufacturer´s internet pages and look for: datasheets, application notes, reference designs. Please read through them. They explain everything you need to know. Maybe you find it boring but the professionals need to read them, too.

Klaus
 

Thank you Klaus for your response. I am clear with the first 2 answers.
3. In4001(50v) may be useful right?
4. Φ1 to ΦA ...I am connected this directly. But if back emf will come from motor's phase, so what we connect between phase 1 to phase A
5. I want to make isolation between ir2110 and controller, for controller protection. Or any method is available for reverse protection for controller ?
 

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Hi,

3) Now you show a half bridge circuit. Different. Thus you need a diode that can handle the driver´s peak current (what value do you expect?) for the repetitive diode_peak_current (look into the diode datasheet. I won´t read it for you).

4) Now you show a half bridge circuit. Different. Look into the MOSFET´s datasheet. There are diodes already. Usually you need no external ones unless your integrated diodes are slow and your switching is very fast.

5) Isolation or protection?
* Isolation: You need isolation (and optocouplers) only if you need galvanic isolation of microcontroller and power circuit. I see no reason for this in your circuit. Tell us why.
* Protection: Again: protection usually is not needed. The mcrocontroller´s drive capability is well enough to drive the IR2110´s inputs. If you think it is needed, then say why.

Klaus
 

For reverse voltage or current will damage the controller.
So I thought of protection the controller using optocoupler.
Correct me Klaus if I am wrong.
 

Hi.

For reverse voltage or current will damage the controller.
True. But where do you expect this "reverse voltage or current" comes from?

I don´t see this for the microcontroller pins.

If you see this --> please use a pencil and a paper and show it to us ... instead asking a vague question. I picture can say more than thousand words.

Klaus
 

In case if gate driver get damaged, then the back emf will touch the controller, so I thought like that. Sry if am wrong.
Ok Klaus , I have attached a image of 3 methods, can you explain me which method is right and why?
 

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Hi,

In case if gate driver get damaged, then the back emf will touch the controller, so I thought like that. Sry if am wrong.
If the driver gets damaged, then most likely the mosfets get damaged, too, causing smoke, vaporized PCB traces, maybe fire. I assume then a broken microcontroller isn´t your biggest problem.

*****
Picture:
1) external diodes. I assume you don´t need them. In detail it depends on the speed of the internal diodes and the swtiching speed.

2) capacitor: no good idea at a high speed switching signal.

3) no extra protection: I assume this is all you need.

***
Maybe you should look for a ready to buy BLDC module.
Or at least some integrated driver IC like DRV8332. It includes overcurrent protection and overtemperature protection.

Klaus
 

I got it Klaus, but i like to make a bldc controller. So I may get some knowledge. I go by 3 method.
Can Arduino's analog able sense the current, for eg: I want to check the load which is of 10amp. By dividing the current using resistor. If possible , then how?
 

Hi,

I want to travel. Is a train good for?
* A train is not suitable for traveling from my village to the next village, because no village has a station.
* A train is not suitable for traveling from Paris to New York City, because there´s the sea.
But there are many cases where a train is suitable....

You know what I mean: It depends. Thus we need suitable information first.

What current?
* Power supply current pulses
* Power supply current average
* Motor winding current pulses
* Motor winding current low pass filtered

What do you like to do with the current signal?

Klaus
 

I want sense,
1. Dc bus current
2. Winding current of motor
Using Arduino as controller and how to give the feedback to the controller
 

Hi,

DC bus current is simple:
Use a "current monitoring amplifier".
I'd use it this way: power supply input -> capacitor -> current monitor -> capacitor --> halfbridges
This helps to reduce the current ripple.
An additional low pass filter may be useful at the current monitor output...to further reduce the ripple.

Motor winding current.
Is way more complicated.
* Because the voltage at this node is swiching. The sharp voltage edges makes it difficult to measure.
* And because the winding current is positive and negative.
Here I recommend to look for dedicated application notes because it's too complicated to explain from scratch.
Additionally it mainly depends on what you want to do with this signal, which is totally unclear.

Klaus
 

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Thank you Klaus.
Now I want to limit the current if it exceed (say: 10amp), so I want to make current sensing circuit using op amp. Can you guide me..,
 

Hi,

This is not a new idea... therefore you find a lot of information here in this forum, at the semiconductor manufacturers and in the internet.
Many possible solutions. Go through them and find out what you need and what/how you want to design it.

Again my recommendation from post #8: "Or at least some integrated driver IC like DRV8332. It includes overcurrent protection and overtemperature protection".
Why re-inventing the wheel? It consumes time, money, fails, damaged parts...

Klaus
 

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