[moved] problem with IR2118 mosfet driver in PSPICE.

[mohammadmother]

Hi
I simulate this circuit in PSPICE


but i get this error. I download the IR2118 PSPICE model.


please help!

 

[BradtheRad]

Your timestep appears to be 5E-18. That is tiny. I believe you can try larger values. A reasonable starting value is so 1000 timesteps fit within one frequency cycle.

 

[FvM]

You know that the IR2118 circuit is incomplete? Missing bootstrap diode and capacitor.

Also the power circuit must be grounded.

 

[mohammadmother]

Thanks for your help
I changed my circuit. However, this error yet exist.


How I can change time step and insert bootstrap diode?

- - - Updated - - -

Excuse me I changed my circuit to this and error was solved


But when the PWM is '1' (=when LIN='1'), the voltage between VB and HO is always 0. so the mosfet is off

 

[KlausST]

Hi,

But when the PWM is '1' (=when LIN='1'), the voltage between VB and HO is always 0

That's the way it works.

...the voltage between VB and HO is always 0. so the mosfet is off

To be exact: A MOSFET is OFF, when the voltage between gate and source is 0.
What's this V_gs?

Klaus

 

[mohammadmother]

my means that the mosfet is always OFF.
this driver, IR2118, does not work.

- - - Updated - - -

I connect the driver pin according to the its datasheet.
http://www.irf.com/product-info/datasheets/data/ir2117.pdf

 

[FvM]

I connect the driver pin according to the its datasheet.

Not in the posted schematics.

In the latest schematic, when you added the bootstrap diode, you also mixed up the previously correct HO and VS connection.

Try once more.

 

[mohammadmother]

Now, I changed my convert(boost instead of buck) driver and use IR2113.my circuit is :


but I have this error :

 

[FvM]

Please compare

 

[mohammadmother]

Thanks, I do your work and the error was solved and vout appear. but the vout is 2 v (this is a boost converter!).
anyway I changed my converter to the buck to test your manner(my main target is driving P-mosfet with IR2113 in Buck converter). However the out put voltage was not correct. (we know in the P-channel mosfet the voltage of GS should be negative).

- - - Updated - - -

First I simulate this circuit without any driver.

 

[FvM]

IR2110 and similar drivers aren't design to drive PMOS transistors.

I must confess that I didn't completely realize the change form buck to boost converter, the ground referred transistor can be driven by a low-side driver without bootstrap circuit, the circuit suggested in post #9 should work nevertheless.

 

[mohammadmother]

Thank you for your reply. but I'm really confused!
assume the converter is buck and the mosfet is N-channel. how we can driver it with IR2113?

Thanks a lot

 

[KlausST]

Hi,

but the vout is 2 v (this is a boost converter!).

I don´t see how this can be a boost converter.

Klaus

 

[mohammadmother]

the boost is for former post.
Now I want to drive a buck converter with IR2113 and mosfet is N-channel . I want to use Bootstrap technique. My circuit is but I have error!:sad:

 

[KlausST]

Hi,

please consider how to charge the bootstrap capacitor. Maybe you need an extra low side mosfet (VS=Drain, GND=sorce, LO = gate) just to charge the bootstrap capacitor.

100p is way too low for a bootstrap capacitor.

Add the recommended capacitor at VDD as well as VCC (at least one is missing)

In any case:
Datasheet says:
"All voltage parameters are absolute voltages referenced to COM"
So COM is the reference for all voltages and should be connected to GND.

Klaus

 

[mohammadmother]

Thanks a lot. I did what you said. my error was solved. but the mosfet doesn't drived and it is still always OFF.
my new circuit is:

 

[KlausST]

Hi,

Again:

lease consider how to charge the bootstrap capacitor. Maybe you need an extra low side mosfet (VS=Drain, GND=sorce, LO = gate) just to charge the bootstrap capacitor.

Klaus

 

[mohammadmother]

I did your work. but it is not good idea!

 

[KlausST]

Hi,

It won't work as long as the bootstrap capacitor isn't charged.

Klaus

 

[mohammadmother]

So, What should I do!?