MOsfet Driver ir2112 circuit not working with Spwm from pic16f877a

Hi,

i had done simulation on proteus for pure sine wave inverter using pic16f877A and ir2112 it was working fine till the ir2112 output but givig out transient error for the complete inverter output . After reading some articles and blogs i found that it is the problem with proteus. hence i moved towards hardware part, The output from pic is going great but when i connect ir2112 the output from ir2112 is not proper.
i had given floating input to ir2112 = 12v dc
vcc =5v dc

please help me.

image of the circuit
https://obrazki.elektroda.pl/1897433900_1490436534.png

IR2112 can't be driven by 5V logic level, review datasheet. Use dual supply IR2110 instead with 5V VDD and 12-15V VCC.

dual supply IR2110 is the general IR2110 ?? or a different ic. If possible can you please provide the basic circuit for the same. Can i connect logic supply ground nad floating ground pins togather with other gnd pins ??

Hi,

Circuit is given in the IR2110 datasheet.
Floating GND description and the limitations are given in the datasheet.

What exactely do you need from us?

Klaus

dual supply IR2110 is the general IR2110 ?? or a different ic. If possible can you please provide the basic circuit for the same. Can i connect logic supply ground nad floating ground pins togather with other gnd pins ??

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Hi Klaus,
As i described in my post the simulation with ir2112 was working but not the hardware. So firstly i would like to know for pure sine wave inverter circuit is it possible to use ir2112 as mosfet driver if yes then how?
A proper practical diagram of mosfet driver will help me to understand better as i am a newbie. Also how to select bootstrap components. As my PWm frequency is 10KHz.

your help is very much appreciated thanks in advance.

Hi,

Again: all is written in the datasheet.

You have to follow the rules of the datasheet. Simulation should be less reliable.

See parameter VIH.
Your PIC can´t satisfy this.
We recommended to use another driver with 5V compatible inputs. --> It seems you don´t want this.
You could use a microcontroller which satisfies Vih of the driver. --> not easy to find
You could use a level shifter --> much effort

Schematic --> I still refer to the schematic in the datasheet.
Component seclection --> I still refer to the datasheet.

MOSFET driver, related circuits and related problems are the most discussed problems here.
But if you read through them you will find that the answers are almost the same: You have to follow the rules of the datasheet.

The driver IC manufacturers provide a lot of additional information and documents like application notes.

Klaus

Can I connect logic supply ground and floating ground pins together with other gnd pins ??

Click to expand...

IR2110 has separate logic (VSS) and output (COM) ground pins. They will be usually connected to the same ground net, but sometimes at different places to improve noise suppression. The datasheet allows for a certain "logic supply offset voltage", although it's rarely utilized in usual IR2110 circuits.

Regarding connection of "floating ground pin" Vs. It can be connected to COM if the high side driver is used as low side driver, in the standard bootstrap driver circuit, it must be of course floating and is connected to half bridge output rather than ground.

After reading all of your comments, what i got is IR2112 cannot be used or it is difficult to use with pic16f877a so i can go with IR2110 which can do the job. Circuit will be designed based on datasheet of IR2110 and application notes AN-978. I hope i got your point if i am wrong anywhere plese do guide me. I am very greatful for your help.

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I was Studying AN 978 apllication note for IR2110. In the the bootstrap component selection part an equation is provided for Capacitor selection. There are few parametrs I did not understand.
1) bootstrap capacitor leakage current :: from where to get this value, if it is from data sheet then i dont know the suitabe capacitor yet, to have the datasheet.
2)Forward voltage drop accross boot strap diode
3)Voltage drop accross low side FET ....... iam using IRF840N MoSFET
4)Minimum voltage between Vb and Vs.

Hi,

for usual applications:
1) don´t care about it. Other parameters will have much more influence.
2) diode datsheet. (<1V for Si diodes, <0.7V for schottky diodes)
3) mosfet_Rds_on * low side current. (I assume < 0.5V)
4) driver high_side_undervoltage_threshold

***
In many "hobbyist" projects I see relatively low ohmic resistors connected across G and S of a MOSFET.
The benefit of MOSFETs is the low gate current .. but with the external resistor they kill this benefit.
The resistor drains out the bootstrap capacitor.

I don´t know why they use it.
I don´t see that less than 10k is useful .. to prevent from floating gate.
The appliction notes and datasheets often don´t show it at all.

Klaus

Hi Klaus,

So the 1k resistor used between G and S is not required.

Please help me in the selection of bootstrap capacitors and diode as refering to application notes iam stuck at the equation provided by it.

Hi,

look at the formula... and then give all values you have.

I won´t go through all the datasheets..
Do your job.

Klaus

thats what i asked you i am not clear about some the parameters in the formula
1) bootstrap capacitor leakage current :: from where to get this value, if it is from data sheet then i dont know the suitabe capacitor yet, to have the datasheet.

"see parameter vih " what does this mean ? what is this vih parameter ? this is new for me.

Hi,

I can only repeat:
* leakage current: sometimes you may find it in the capacitor datasheet, but not always. It has only a small influence on botstrap capacitor size, therefore I recommended you not to care about it.

Generally how to find informations:
"Capacitor leakage current" :
* "Capacitor" is the device --> open the capacitor datasheet
* "leakage current" is the parameter --> use the "search" function to find this itim in the datasheet.

The same applies to "VIH"
* i told you "all is written in the datasheet" --> open the datasheet.
* "see VIH" --> use the search function to find the item in the datasheet.

Datasheet says "Logic 1 Input Voltage" in the "parameter definition" column.
* "logic 1" = HIGH
* "input voltage" = voltage at it's signal inputs
* the specified value is " min 9.5V"
In other words: IR2112 needs at least 9.5V at it's input to recognize a valid HIGH logic level.

A forum can not replace a good book, a tutorial, a school...therefore you need to understand that it us impossible to explain every item in detail. You need to learn the basics on your own.

Btw: the problem with IR2112 (and other mosfet drivers) input levels has been discussed here that many times. I assume more than 100 times. Read existing discussions, that's how a forum is meant to work.

And - as already written - search the driver IC manufacturer's internet sites. They provide a lot of informations, very detailed.

Klaus

i got it this time about the problem with ir2112

Look at these two drivers capable of driving MOSFET from TTL/CMOS logic inputs. LTC4440, MC34152

If you want to check if IR2112 is working or not just give input to LIN and check output in LO to COM and give input to HIN and check output between HO and VS. Then you will know by yourself. Dont't connect the MOSFET or bootstrap capacitor.

ihad checked that it is not working as klausST said VIH parameter is not matching with pic16f877a so now i am going to try with ir2110 with +5v logic input and 12v floating input
thanks for your help i will get back here and will share my experience