Generating uni-polar PWM signal using IR2113

Ng Jing Xi · Dec 29, 2013

These are the waveforms I got after connecting up the IGBTs.

1. The probe I used is connected across both the Vout.
2. The second photo is the red probe connected to Vout while the black probe is connected to GND. [For reference for Vout(10ms).jpg, Vout(10us).jpg, L0(10ms).jpg]

Do you know what is the problem here? I am not getting a nice waveform for the output.
It appears to be distorted.

audioguru · Dec 29, 2013

I do not see any PWM. Maybe the power supply voltage is bouncing too much.

Ng Jing Xi · Jan 1, 2014

audioguru said:
I do not see any PWM. Maybe the power supply voltage is bouncing too much.

So any idea on how to get the IGBT to switch with my PWM signal?

When I measured the Vg1s, the waveform shows a 0v DC. [Probe between the Vs and IGBT Q1 Gate]
However, when I meansured the Vg2s, the waveform is a distorted waveform. [Probe between Vs and IGBT Q2 Gate]

audioguru · Jan 1, 2014

You need a better power supply that produces steady output voltages.

Ng Jing Xi · Jan 1, 2014

audioguru said:
You need a better power supply that produces steady output voltages.

Currently, I am taking the input voltage from a DC power supply. Isnt that stable enough?

However, I am planning to use a DC-DC converter to regulate the power supply in the actual circuit

audioguru · Jan 1, 2014

Your 'scope photo in post #81 shows the voltage of -VDC jumping all over the place instead of being steady.

Ng Jing Xi · Jan 1, 2014

But is there a problem with my schematic?

Ng Jing Xi · Jan 1, 2014

audioguru said:
Your 'scope photo in post #81 shows the voltage of -VDC jumping all over the place instead of being steady.

I realised that my power supply for all the chips are fine.
However, the +VDC and -VDC connected to the IGBT are showing unsteady voltage. Does it require a filter or something?

audioguru · Jan 1, 2014

Sorry, I do not have time to see what is your power supply.
I also do not have time to look up application notes for the IR2113 to see if the com voltage for the low side IGBT must be the same as the COM voltage as I suspect or if it is allowed to be a negative voltage like you have.
Also, I suspect that the input pulses to the IR2113 both must be in phase but yours are out-of-phase.

JoeJester · Jan 1, 2014

Can we assume you familized yourself with DT04-04 and AN-078?

The Ten 5-2422 DC to DC convertor only supplies 250mA ... what does your circuit actually draw? Have you checked it with a DC power supply that is capable of whatever power your design actually requires? Is the DC input to the Ten 5 within the specifications required by the datasheet?

Ng Jing Xi · Jan 2, 2014

JoeJester said:
Can we assume you familized yourself with DT04-04 and AN-078?

The Ten 5-2422 DC to DC convertor only supplies 250mA ... what does your circuit actually draw? Have you checked it with a DC power supply that is capable of whatever power your design actually requires? Is the DC input to the Ten 5 within the specifications required by the datasheet?

I am not entirely familiar with DT04-04 as my lecturer has not taught us anything regarding this area. This is part of final-year project.
The DC-DC converter supplies 250mA which is able to power up the IC chips[TL072, LM741, IR2113] in my circuit.

As for the DC input to the Ten 5, the max voltage from the PV is 44V while the max voltage TEN 5 can handle is 50v.

JoeJester · Jan 3, 2014

Let me get this straight ....

You are modulating the PWM with 50 Hz and your triangle wave frequency is 100 kHz. Don't you think that is a little excessive? You will have a hard time to see that with an oscilloscope to see the variance in the pulse widths. When you view one cycle of the 50 Hz, that is 2000 square waves (full screen) or 200 square waves per cm on the oscilloscope.

If your doing this to demonstrate, in the classroom, I would reduce the triangle wave to no more than 50 times the highest modulating frequency.

I recommend you review TI's Analog Pulse Width Modulation, SLAU508. It should give you some insight to your triangle wave generator design.

My next recommendation is to add test points to your schematic. Then when you upload pictures, you can title the picture with the test point's name. That way everyone can be on the same page.

The first scope presentation is 100 kHz triangle wave. The second is 2.5 kHz triangle wave. The diagram is the test setup. The voltage levels were set to what we are expecting in your schematic. Vcc is +12V

shortbus= · Jan 4, 2014

Ng Jing Xi said:
Hi,

So I was able to generate a PWM signal. However, when I pass it through the IR2113, the Ho only shows a constant DC line while the Lo shows the PWM signal. Anyone has any idea on why the high side is unable to work?

The waveform shown below are taken before connecting to the IGBT, [After R9, R10]
The red line indicates the 0V reference line

I may be wrong here but, are you saying that you are giving PWM to both high and low sides at the same time? It is my understanding that in a H-bridge using PWM you only give the PWM to the low side. If both high and low switches are off at the same time the boot strap circuit/capacitor won't get charged.

Ng Jing Xi · Jan 6, 2014

JoeJester said:
Let me get this straight ....

You are modulating the PWM with 50 Hz and your triangle wave frequency is 100 kHz. Don't you think that is a little excessive? You will have a hard time to see that with an oscilloscope to see the variance in the pulse widths. When you view one cycle of the 50 Hz, that is 2000 square waves (full screen) or 200 square waves per cm on the oscilloscope.

If your doing this to demonstrate, in the classroom, I would reduce the triangle wave to no more than 50 times the highest modulating frequency.

I recommend you review TI's Analog Pulse Width Modulation, SLAU508. It should give you some insight to your triangle wave generator design.

My next recommendation is to add test points to your schematic. Then when you upload pictures, you can title the picture with the test point's name. That way everyone can be on the same page.

The first scope presentation is 100 kHz triangle wave. The second is 2.5 kHz triangle wave. The diagram is the test setup. The voltage levels were set to what we are expecting in your schematic. Vcc is +12V

Thanks Joe, noted!

Technically currently my triangle wave freq is 66kHz. The reason why I choose such high frequency is for me to be able to filter off all the higher harmonics at the filter circuit.

However the issue now is that my driver circuit is having problem. When the +/-VDC for the IGBT is not connected, when I measured at the TP(-VDC2), this is the waveform I got.
For your reference, I also insert my waveform for the PWM signal inputs to the driver.
*For a better reference of the PWM signal, I increased the sine wave t0 5kHz*

I referred to the notes that you mentioned, dt04-4. For the sizing of the bootstrap capacitor, I am unable to calculate it cause I can't find all the complete info from the datasheets. The IGBT that I am using is STGF10NC60KD. And the driver is IR2113.

audioguru · Jan 6, 2014

Again, the -VDC2 voltage is jumping all over the place. It is supposed to be STEADY DC. I can't remember what voltage it is supposed to be and it is not listed on your schematic.
Is +VDC also jumping all over the place?

audioguru · Jan 6, 2014

Your schematic is missing dots (solder joints) at +Vout and -Vout.
Why are you measuring TP(-VDC2) when the +/-VDC for the IGBT is not connected?

You do not understand that the Bootstrapping does not work when the IGBTs are not working.

Ng Jing Xi · Jan 6, 2014

audioguru said:
Again, the -VDC2 voltage is jumping all over the place. It is supposed to be STEADY DC. I can't remember what voltage it is supposed to be and it is not listed on your schematic.
Is +VDC also jumping all over the place?

Sorry, my bad. The solder points are to be connected but I left it out in my schematic. When I measured the DC source directly, it is a 12V DC line. But when I connect it to the IGBT, it became unsteady. I am using a +12VDC for the IGBT.

Ng Jing Xi · Jan 6, 2014

shortbus= said:
I may be wrong here but, are you saying that you are giving PWM to both high and low sides at the same time? It is my understanding that in a H-bridge using PWM you only give the PWM to the low side. If both high and low switches are off at the same time the boot strap circuit/capacitor won't get charged.

Nope. Because my PWM signal are inverted and has a deadtime between the Hin and Lin signal

audioguru · Jan 7, 2014

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.

shortbus= · Jan 7, 2014

Ng Jing Xi said:
Nope. Because my PWM signal are inverted and has a deadtime between the Hin and Lin signal

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.

Generating uni-polar PWM signal using IR2113

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