IGBT Interface to 8051

[bgpavan]

Hello ,

I am trying to Interface IGBT NGB8245N from ON semiconductor to an 8051 microcontroller ,My question is can i connect the output pin of the microcontroller directly to the gate of the IGBT .Will I need to have any kind of isolation cktry like opto isolator or any drive cktry to drive the IGBT .Please help


Thanks,
Regards
BG

 

[Tahmid]

Will you just be having on/off action or is the output PWM? How fast/frequently will the switching be done? Anyways, it's better to use a simple driver. Many many drivers are available, even in 8-pin DIP packages.

Hope this helps.
Tahmid.

 

[bgpavan]

Will you just be having on/off action or is the output PWM? How fast/frequently will the switching be done? Anyways, it's better to use a simple driver. Many many drivers are available, even in 8-pin DIP packages.

Hope this helps.
Tahmid.

Hi Tahmid .

I will be using the IGBT to just turn on/off action .The gate of the IGBT will be triggered depending on an event on the microcontroller pin.There will not be any fast switching .Please suggest me with a part no for driver if its required for my application.


Thanks,
Regards,
BG

 

[Tahmid]

Since it is just for on/off action, you can make do with a transistor-based driver circuit.

You can use one of these circuits:

You can also use one of many driver chips. You may use the common TLP250. Or you may even use drivers such as TC427.

Hope this helps.
Tahmid.

 

[goldsmith]

Hello ,

I am trying to Interface IGBT NGB8245N from ON semiconductor to an 8051 microcontroller ,My question is can i connect the output pin of the microcontroller directly to the gate of the IGBT .Will I need to have any kind of isolation cktry like opto isolator or any drive cktry to drive the IGBT .Please help

Dear bgpavan
Hi
You can use a simple ICL7667 as your driver and if you need isolation you should tell the frequency of operation .

Hi dear Tahmid
A short comment about your latest post :
I think you have used Q6 to convert 5 volt input , to 15 volt ( or Q2 ) , right ? if yes , i don't think this way is a good way ! did you see the out put wave , ever ? as you probably know , if the RC be high , the out put wave will be relax . so you have to decrease it's value , but if you want use this way , you should use a current source instead of RC . thus the result will be agreeable .
Best Regards
Goldsmith

 

[Tahmid]

At the Q6 collector where there is the high resistance, the capacitance is very small. And bgpavan has said that there will be no fast switching. So, there shouldn't be a problem.

 

[goldsmith]

How much is the frequency of operation ? he didn't mention it . and about converting 5 volts to 15 volts why not just Q3 and Q4 ? those are enough . and about R2 and R3 , those are a bit high , and it will consequence lower , instantaneous current capability .

 

[Tahmid]

How much is the frequency of operation ? he didn't mention it . and about converting 5 volts to 15 volts why not just Q3 and Q4 ? those are enough . and about R2 and R3 , those are a bit high , and it will consequence lower , instantaneous current capability .

Go through posts 2 and 3. You will find that I asked him about switching and frequency. He said that there will be no quick switching. Just on/off action. So that would be like what a relay is used for. Instead he opts for a solid state solution. So, not too much current will be required to drive the IGBT.

I don't think you can convert to 15V with just Q3 and Q4. Since the PNP transistor is sourcing the current, to turn this off, you would need >14.3V. You can't get that from microcontroller output. And if you rely only on pull-up for this, the 15V will damage the microcontroller pin. That's why Q2 is used.

Hope this helps.
Tahmid.

 

[goldsmith]

No my mean was not q4 and q 3 in that arrangement ! i thought you got the idea , see below , please:

Good luck
Goldsmith

 

[Tahmid]

The problem with that is that the output signal is inverted. You would need to send 1 to turn off IGBT and 0 to turn on. If that is required, a simple transistor inverter may suffice in this situation. No need for the PNP transistor. Connect a resistor between gate and +ve volt. Since speed is not a requirement here. However, don't you think, it's better that the signal is not inverted?

 

[goldsmith]

Thamid why inversion for a single IGBT or mosfet is important for you ? it is not any difference between inverted and non inverted for a single switch .
And do you know the action of PNP transistor in my circuit ? i have used this circuit for frequencies nearby 12MHZ , as well . this action is the same with ways that we using in digital gates . impedance of current source is high , and current is high too .

 

[bgpavan]

Hello All ,

Thanks Tahmid and thanks all for your suggestion
Tahmid you have guessed it right , my idea is to replace the electromechanical relay with a solidstate switch like an IGBT or a Mosfet .


regards,
Bg

 

[Tahmid]

Thamid why inversion for a single IGBT or mosfet is important for you ? it is not any difference between inverted and non inverted for a single switch .
And do you know the action of PNP transistor in my circuit ? i have used this circuit for frequencies nearby 12MHZ , as well . this action is the same with ways that we using in digital gates . impedance of current source is high , and current is high too .

It would make things hassle-free for the programmer to keep the IGBT off with 0 and on with 1. However, this can be worked around. But maintaining the phase makes it easier and hassle-free for the programmer.

The OP has mentioned he does not require any high-frequency switching. So, no need to add that. If phase inversion is used, a simple NPN transistor with resistor will suffice. The two additional PNP transistors aren't required. If phase is to be maintained, one NPN and one PNP transistor as shown in 2nd diagram in post #4 will do.

 

[goldsmith]

Hi Tahmid
I think you know if rise time and fall time be higher the dissipation will increase ? ok ?
So , a designer should keep Tr and Tf as low as possible however when the frequency is low , the problem is lower , but i prefer safe design .
Best Wishes
Goldsmith

 

[Tahmid]

He'll be using it instead of a relay. So it'll be on for a reasonably long time and off for so as well. So, the loss due to rise and fall will be insignificant. Imagine this scenario: he needs to turn on the IGBT, keep it on for 10 seconds, then turn off and keep off for 20 seconds. Here, it's quite clear the rise and fall losses won't be significant, since once the IGBT has turned on, it'll be on for a rather long time and the significant loss is the conduction loss only.

 

[goldsmith]

keep it on for 10 seconds, then turn off and keep off for 20 seconds.

If the time is as large as you said , yes you are quite right .

 

[godfreyl]

If phase is to be maintained, one NPN and one PNP transistor as shown in 2nd diagram in post #4 will do.

As an alternative, one could do the same thing with two NPN transistors as shown below. (It uses one less resistor too, for the penny-pinchers).

btw, Is the gate stopper resistor really needed? I know they're important to prevent oscillation when MOSFETs are used as linear amplifying devices, but I wouldn't have thought oscillation could be a problem in a simple switching application. Am I missing something?

 

[goldsmith]

"btw, Is the gate stopper resistor really needed?"
Hi dear Godfreyl
What do you mean by gate stopper resistor ?
Respectfully
Goldsmith

 

[Tahmid]

As an alternative, one could do the same thing with two NPN transistors as shown below. (It uses one less resistor too, for the penny-pinchers).

btw, Is the gate stopper resistor really needed? I know they're important to prevent oscillation when MOSFETs are used as linear amplifying devices, but I wouldn't have thought oscillation could be a problem in a simple switching application. Am I missing something?

It is used here as "safety" to make sure the IGBT doesn't turn on accidentally. It happens usually with high voltage but can sometimes happen at low voltage as well. If you search on Edaboard, you'll find lots of threads complaining of problems such as damaged MOSFETs/IGBTs, where the solution was that one resistor.

 

[godfreyl]

What do you mean by gate stopper resistor ?

The resistor connected to the gate of the IGBT (R5 in this picture).

It is used here as "safety" to make sure the IGBT doesn't turn on accidentally.

Surely that is the purpose of R2? I was wondering about R5.