Generating uni-polar PWM signal using IR2113

[audioguru]

But only the Lin should be PWMed. If there is no constant DC on the Hin, there is no voltage to control the bootstrap part of the circuit.

I think you are WRONG.
The high-side IGBT must be driven so that its source charges the capacitor to a voltage ABOVE the supply voltage so that the gate voltage pulse is about 10V higher than the source voltage.
It is a charge-pump.

The power supply is a mess and I don't know why it is not fixed or replaced.
I have a suspicion that the L-in must not be inverted because when it goes high you want the low-side IGBT to turn on and pull the output down.

 

[Ng Jing Xi]

Your circuit cannot work properly with your defective power supply. Fix it or replace it.

Since you do not have a dual channel 'scope then we cannot see what HI and LO are doing at the same time or what the the two driver circuits are doing at the same time.

I tried changing the power supply and the same issue occurs. Could it be that the boostrap capacitor is not of the correct sizing?

I will post up the waveform of the Ho and Lo later

 

[audioguru]

Your circuit inverts the Lo signal that might be wrong, then the IGBTs might be both turned on at the same time and are shorting the power supply.
The datasheet should explain the calculation for the value of the bootstrap capacitor. If its value is too low then it will not cause your problems and odd waveforms.

 

[JoeJester]

Ok,

You have VS connected to +Vout. VS is the VB return. You need to draw whatever your going to load with this thing to give us a complete drawing.

If you use a dual trace scope, the HO should, except with a slight delay, follow the HIN signal. Same applies to the Low side.

 

[Ng Jing Xi]

These are the waveforms that I manage to capture. The channel 1 shows the TP(IGBT1HIGH), while channel 2 shows TP(IGBT1LOW),

 

[Ng Jing Xi]

Ok,

You have VS connected to +Vout. VS is the VB return. You need to draw whatever your going to load with this thing to give us a complete drawing.

If you use a dual trace scope, the HO should, except with a slight delay, follow the HIN signal. Same applies to the Low side.

The rough idea is this drawing below. The Vout will be connected to a filter circuit to get a 50Hz sine wave

 

[alec_t]

Could you please shrink your image file size down before posting? For people on capped data tariffs or with slow internet connections large files are inconvenient.

 

[JoeJester]

The rough idea is this drawing below. The Vout will be connected to a filter circuit to get a 50Hz sine wave.

Ok, your going from a low level 50 Hz sine wave to a 12 V PWM, to a larger level PWM, and back to a larger level 50 Hz.

Now, your diagram doesn't indicate the part numbers for Q1 through Q4. I assume there is a junction where Q1/Q2 connection crosses the +V out line.

I also see +VDC and -VDC ... what are those values?

 

[audioguru]

The digital 'scope makes a big mess of the PWM waveforms.
I expected to see a 50Hz sinewave there but I see only 800Hz very rough mountains.
The PWM rectangular waves are not even rectangular, instead they are a mess.
I wonder why the HIGH has half the amplitude of the LOW and has a lot of DC on it?
I wonder if the power supply voltages are still jumping up and down?

 

[audioguru]

Could you please shrink your image file size down before posting? For people on capped data tariffs or with slow internet connections large files are inconvenient.

The size of the file is HUGE because it has a dark grey background instead of white. It seems to be a photo taken in moonlight.

 

[JoeJester]

At 250 uS/cm with a 68 kHz Triangle wave, I'm not surprised the PWM signal looks terrible. We are looking at 0.015th of the modulating frequency and 17 cycles of the triangle wave per cm.

 

[shortbus=]

I think you are WRONG.
The high-side IGBT must be driven so that its source charges the capacitor to a voltage ABOVE the supply voltage so that the gate voltage pulse is about 10V higher than the source voltage.
It is a charge-pump.

Thats what I'm trying to say. Just don't have the literary skills to get it a crossed.

If the high side is off at the same time the low side is off, the boot strap won't charge. He is controlling the Hin and Lin on the same gate driver with the same signal.

 

[audioguru]

Lin is Hin that is inverted. Then maybe the output is trying to go high and low at the same time which messes up everything, especially the power supply voltages.

 

[Ng Jing Xi]

Ok, your going from a low level 50 Hz sine wave to a 12 V PWM, to a larger level PWM, and back to a larger level 50 Hz.

Now, your diagram doesn't indicate the part numbers for Q1 through Q4. I assume there is a junction where Q1/Q2 connection crosses the +V out line.

I also see +VDC and -VDC ... what are those values?

The inverter should produce a 12V unfiltered waveform.
For the IGBT, i am using TO-220FP, STGP10NC60KD.

Sorry, What do you mean by "where Q1/Q2 connection crosses the +V out line."

For the +VDC and -VDC, i am using a +12V from the DC-DC converter. But This DC-DC converter is also powering up the IC chips in the circuit. Is it wrong?

 

[Ng Jing Xi]

The digital 'scope makes a big mess of the PWM waveforms.
I expected to see a 50Hz sinewave there but I see only 800Hz very rough mountains.
The PWM rectangular waves are not even rectangular, instead they are a mess.
I wonder why the HIGH has half the amplitude of the LOW and has a lot of DC on it?
I wonder if the power supply voltages are still jumping up and down?

Actually my DC supply is okay but whenever I connect it to the IGBT, it just get messed up. I think it's because of the driver circuit that is causing this effect.
When I connect the -VDC of the IGBT to the GND of the overall circuit, the power supply goes haywire.

 

[Ng Jing Xi]

The size of the file is HUGE because it has a dark grey background instead of white. It seems to be a photo taken in moonlight.

I am sorry for the large file. I got no idea why the file is so big. I took the picture under the white light. Hence, I got no idea why is there a dark grey background.

 

[audioguru]

Can you post a photo of the two-channels 'scope showing the high frequency gate signal at the HIGH IGBT and the high frequency gate signal at the LOW IGBT at the same time to see if both are turned on at the same time?

 

[Ng Jing Xi]

Can you post a photo of the two-channels 'scope showing the high frequency gate signal at the HIGH IGBT and the high frequency gate signal at the LOW IGBT at the same time to see if both are turned on at the same time?

For your better overview of the waveforms, I increased the sine wave to 5kHz so that you can view the PWM signal more accurately.
Channel 1: IGBT 1 Gate Signal
Channel 2: IGBT 2 Gate Signal

 

[audioguru]

I was correct from the beginning. The IGBT's are fighting each other. Both are turned on at the same time with one pulling high and the other pulling low causing very high power supply current but no signal at the output. No wonder the power supply voltages are messed up.
Also it looks like something is reducing the level of the HIGH gate drive signal.

The IR2113 must already be inverting one input but you are also inverting the LOW input.
If you do not invert the LOW input it will be fixed except it will have no dead time between switching the output high and low.

 

[Ng Jing Xi]

I was correct from the beginning. The IGBT's are fighting each other. Both are turned on at the same time with one pulling high and the other pulling low causing very high power supply current but no signal at the output. No wonder the power supply voltages are messed up.
Also it looks like something is reducing the level of the HIGH gate drive signal.

The IR2113 must already be inverting one input but you are also inverting the LOW input.
If you do not invert the LOW input it will be fixed except it will have no dead time between switching the output high and low.

But is the dead time necessary for the H-bridge inverter.
Let me try that out and I'll get back to you.