UCC28070A: One phase inductor current making problem

Hello Aaqib, 

Thank you for your question on using the UCC28070A PFC controller. 

Since you have swapped inductors and tried new one with the same result, we can conclude that the inductor design is not the problem.
Also, since one phase does work with the correct current wave-shape, we can infer that the non-working phase has some problem with the current control. 

Your schematic diagram image is fuzzy but I can see that the design of the two phases is symmetrical and if one side works we can expect the other side to work as well. 
Therefore I suggest that possibly the current sense in the phase with Inductor 2 (let us call it Phase 2) is not working correctly. 
It is possible that some component(s) on the board do not match the design on the schematic because of an assembly error. 

Please the orientation of the 1N4148 diodes located in the current-sense path of Phase 2.  Make sure they are installed with the correct polarity. 
If those are okay, check the values of the resistors and capacitors in that path. 
If the values are okay, check that the soldering of each component is good, and look for possible open-circuit (bad solder joint) or short-circuit (unwanted solder blob or piece of wire) at the component pads.  

Regards,
Ulrich

Hello Ulrich Goerke,

Thanks for your Information. I found one mistake in my soldering and reconnect it and that problem was solved. Now I am facing new problem. I have attached a video of that Problem. Whenever I try to up from 85 Volts, My both inductor starts vibrating and not just constant vibration but increase or decrease as shown in the video and both inductor current become unstable. Please let me know where I am doing mistake. 

Hello Aaqib, 

I'm glad you solved the first problem.  I'll try to help you solve the next one. 

As I mentioned before, the schematic image that you posted is fuzzy (low resolution) and so it difficult to read the component values. 
Please post a clear PDF file of your schematic diagram.  Also please post the UCC28070 Excel design tool that you filled out to obtain your component values.  What is your boost inductance value?  

From the video it looks like the PFC converter is attempting to start up and then gets shut down, then tries to restart, repeatedly. 
From the Functional Block Diagram in the UCC28070A datasheet (page 13), only 3 faults can trigger a RESTART:  UVLO on VCC, VSENSE voltage pulled below 0.60V, and internal thermal shutdown (Tj > 160C).  I don't think low VSENSE or high Tj are credible faults, in this case. 

I suspect UVLO shutdown on VCC.  On your schematic, it looks like you have a connector CN1 for an external voltage source, a resistor (I can't read the value), and a 22uF capacitor for VCC, plus a 13-V zener diode to clamp it.  I think UVLO can happen in 3 ways:
a) Your external source is set to a low value of current limit, such as maybe 10mA or something like that.  Raise the current limit to 100mA.
b) You set the source too close to UVLO threshold and have long thin wires from the source to the PFC board, that drops voltage when the VCC current rises.  Raise the VCC voltage to 15V, use at least 0.5mm diameter wire, use twisted pair and keep length short.  Remove the 13-V zener diode. 
c) The resistor between CN1 and C12 (22uF) has too high value and drops volts when VCC and gate-drive current rises.  Reduce the value of this resistor. 
If any of these 3 possibilities are true, you can solve the restart problem. 

There is still the high peak inductor current problem.  Each time the PFC tries to restart, there comes a very high peak current at the beginning of each line half-cycle.  I think this happens because the CAOx outputs are saturated to 5V.  They saturate because the IMO signal is higher than the internal synthesized CSx signal (OutA nd OutB) near the line zero-crossing and this forces the outputs to 5V and commands maximum duty cycle until the amplifiers can come out of saturation.  
I think maybe that your soft-start is too fast.  It looks like you have 1uF on SS.  Make sure that the value of the cap on the board is 1uF.  If it is, please try increasing this value to 2.2uF or 3.3uF or higher for a slower soft-start.

Another way to reduce the current spike is to increase the offset voltage at the CSA and CSB inputs.  Your current sense resistors appear to be 39R.  The offset resistors to VCC (R26, R29) are 2.4K.  At VCC = 12V, the offset voltage should be 12V * 39R / 2439R = 192mV.  At VCC = 15V, the offset should be 240mV.  A higher offset voltage should reduce or eliminate the spikes but it will introduce a flat 0-A interval in the input current at the zero-crossing. 
You may consider doing this temporarily to eliminate the current spikes and then debug the rest of your PFC system.   
After everything works okay at full power, you can go back to reducing the offset and improving THDi. 

In the video, I see three massive load resistor blocks with 5 of 6 resistors connected in series. What is the value of this load resistance?   
Full power would be around 150R, but the watt-meter shows only about 85W load.  

Finally, what is your AC source?  Is it an electronic AC source with output isolated from the building power, or are you plugged into a non-isolated variable transformer which is plugged into building power?  I strongly urge you to use an isolated source for AC for safety and to make debug easier.
Isolating voltage probes for the oscilloscope do not work well at high frequencies and will distort your signals.
When your AC source output is isolated from earth-ground, you can use ordinary scope probes to view PFC control signals with respect to PFC GND.

Regards,
Ulrich

1.Schematic Prints (Control).pdf2.Schematic Prints (Power).pdf

Mathcad - UCC28070 Design Tool (167uH) .pdfHello Ulrich Goerke , 

Hope you are doing Well. Your above mentioned solution works well. Finally I got some results. I just recheck the voltage of VCC and component values and it works well. I also changed the Css to 2.2uF. peak inductor current problem is also solved. I will attach the Schematic of this project.

Now I am facing the next problem. I am getting 370 output voltage with good waveforms of Input, Inductor L1 and Inductor L2 as shown in Figure but not getting the 390 output voltage. Whenever I crossed the 200 input voltage, My waveforms were not good and fluctuating output voltage. It again starts and restarts as shown in figure.

 At 120 Input Voltage 

 At 180 Input Voltage 

At 210 Input Voltage 

After This Level, It starts fluctuation (starts and restart).   

Hello Ulrich Goerke ,

Hope you will be Fine. Thanks for your Information about the output voltage resistance. I just replace that 24k Ohm resistance with 23.2k ohm resistance

and my output voltage is almost 390 Volts. Now, I am only facing the problem of DCM current of both inductors. I have rechecked the inductor values.

Even I have increased the both inductor values to 170uH but they are still in the DCM Mode. 

You asked me some questions in your previous answers. 

I am using Programmable AC/DC Power Supply (KP3000S) to provide the Variable AC Source as input. 

Input Voltage.pdf