Hello,
I’m trying to trouble shoot my circuit. As it stand right I have no signal at the gate of the high side mosfet. To find out what was the issue I started to dig down to the IC circuitery of the ir2110 and investigate what I was doing wrong in my connections. To do this I decided to scale down my circuit abd removed the mosfet and the signal component.

Experimental setup:
Right now all that is appliyed is +12.5v dc (from a lead battery) at the voltage regulator 7805. This will power the Vcc pin of the ir2110 with +12.5v and the Vdd pin of the ir2110 with +5v. There is no signal that is appliyed at HIN and LI on this setup. See attached schematic.

Question:
Why when probing with a voltmeter between grnd and Vs I’m reading a just little less then 12v (11.98v to be precise), while between Grnd and Vb I’m reading my full 12.5V from the lead battery ? Is this normal to read a voltage between Vs and Grnd?

Thank you for the assistance.

Schematic:
Mod: Lightened your image.

 

Where is your Vboost rectifier?
http://tahmidmc.blogspot.com/2013/01/using-high-low-side-driver-ir2110-with.html

 

The diode is there in the schematic between Vcc and Vb. Not sure if this is what you are refering to?

 

If I remember correctly, these chips need to be continuously pulsed to generate the high side boost voltage so you cannot run then in a static circuit.
Try again with pulsed inputs.

 

@dendad
I will try to provide input to HIN and LIN in addition to my provided setup.
Yesterday everything was connected but HO was not outputing any signal that could mean anything. That why I started to disconnect mosfet and put the ir2110 isolated like this. Could this still be a viable setup without the mosfet connected but providing signal to HIN and LIN ?

 

No, the capacitor that provides the gate voltage for the upper is charged through the lower MOSFET when it is on.

 

Ok.
I’ve connected back everything back the way it was.
Here is screenshot of low side gate mosfet (LO).
…and screenshot of high side gate mosfet (HO). As you can see its “radio-silence” :/
Note. No gate-source resistances are not connected yet.

 

Connect the FETs back to the IR2110 as a full circuit. Add link the loadD.
Although SD has an internal pull down, hook it to 0V. And HIN to 0V also.
Then pulse LIN at maybe 1kHz and measure to see if VB rises.
VS must switch to 0V for the boost capacitor to charge from Vcc via the diode so I think a full circuit is needed to make it work, not just the IC alone.

 

Have you got a load on that test setup? If the load is open, the top FET will do nothing. one of the uses for this IC is in an H bridge so the "load" is actually a short while the real load is connected between two of these circuits.
Maybe this series of articles can help...
https://microcontrollerslab.com/how-to-make-h-bridge-using-ir2110/

 

@dendad, connecting HIN to 0v ? But if I do so I will not get any further, my problem is at HO. No HIN = No HO isn’t it ?
Ack for SD to 0V.

 

Update … I decided to short low side source and high side drain. I managed to get signal at the high side gate. I’m confused now.

 

I trust you are running this on a current limited power supply.
It was to test the boost is working, connect the "Load" outputs together. With just LIN pulsing, and HIN LOW, connect a load (even 1K for a test) from +V to VS Now, you should see about Vccx2 on VB.

I have only used these chips in an H bridge circuit, and that was some years ago so I'm just going from memory. How you use them not in an H bridge configuration I'm not sure.

 

Could this still be a viable setup without the mosfet connected but providing signal to HIN and LIN ?

Below is the LTspice simulation of a test circuit for the IR2110 outputs that needs no MOSFETs:
The same signal is sent to both inputs to simulate the normal inversion of the low-side MOSFET drain signal at VS.
Note that the HO output (yellow trace) is 24V, showing the bootstrap increase from D1 to drive the high-side gate.

 

@dendad
Yes its the plan to use it in half bridge config.
I’m runing it now on a current limites power supply and not on the battery anymore… otherwise I risk to fry something. Drawn amperage is almost negligeable “see 0”.
Here is a screen shot of both HO and LO together after shorting high side drain and low side sourse.
Still trying to understand what is going on.

 

Update … I decided to short low side source and high side drain. I managed to get signal at the high side gate. I’m confused now.

You do need the lower side to be connected via a load or short and switching to work. The top is floating so if the low side FET is open, you will not see anything from the top as it is in effect disconnected.
When the low FET switches on, the top FET VS is pulled to 0V and the boost cap charges via the diode.
Then, when the low FET is off, the top FET can be turned on using the charge in the cap to supply the gate drive. But, this charge will go away quickly so the top FET must be turned off again and the low FET pulsed to replenish the cap.
You must continuously pulse it to work, unless an isolated gate supply is added between VS and VB.
If you do add this supply, the top FET can be driven with a load to 0V independantly of the low FET, and in a similar manner, the low FET can switch a load connected to a +V power supply.

 

Thanks alot for the assistance.
So my take away is that a resistance between high side drain and low side source needs to be connected.

On the data sheet they represent a capacitor in that area. Maybe that is what I’m missing.

 

No, the caps are not it. There is a power bypass cap COM to VCC and you do need that for stability. Another cap for bypassing on the logic side, and the boost cap that is for the top FET gate drive.
I think the data sheet is a bit confusing. It makes more sense to me to short the "TO LOAD" pins together and run it as a half bridge.
What is your power supply voltage and the application you are aiming for?

 

@dendad
Thank you so much for your help.
High side fet is now working as it should
Right now just powering this on 30v for demonstration. Circuitery is powered through lead battery.
Oscilloscope probe is on x10 for proper display.
My main issue was one of my solder that lacked connection. That joint was between low side fet drain and high side source. The theory explained above lead me to investigate in that vincity.
I now have a half-bridge setup thar I can use for various project and connect to an LLC network in the future.

 

I do try to be of help if I can. Electronics has been my interest and work life for the last 55 years or so in telecommunications and industrial control. It is a great field to be in and there is so much you can do nowadays. I've a proto board using these chips somewhere that I went to my shed to find to show you a picture but it is "somewhere" and not where I thought it would be. My shed is an accumulation of many years of not throwing things out.......
I do hope you have success with your project.