Mid-power supply deign with/without PFC using UCC28600

Is there any rule to tune parameters at QR Simulator for matching output current?

BR

W.H.

1. The requirement to have PFC is mandated by regulations and was once really only required for high power industrial applications but has since moved to lower power levels that affect residential and commercial applications.  IEC61000-3-2 sets mandatory standards for supplies sold in the EU, there are voluntary standards for North America. The U.S. Department of Energy’s Energy Star Computer Specification includes “80 Plus” power-supply requirements for desktop computers, servers, and laptops.  The UCC28600 will operate fine without a PFC front end but there will be the typical harmonics  that will not meet regulatory specifications at power levels that are 75W or more. 

2. To use the Design Calculator with a PFC front end, do exactly as it states on the Instruction page: "For PFC systems that have a fixed bulk voltage, estimate the PFC output voltage at the peak of its ripple.  Calculate the equivalent ac voltage to achieve that maximum voltage level.  Enter that ac voltage as the VAC(max) level.  Enter the minimum operational ac line voltage as the VAC(min) level because the QR Flyback must power up correctly in order to start the PFC stage."

And also re-stated on the QR Design Tool page: "For systems with a PFC front end, the VAC(max) value entered into cell C15 should be equivalent to the maximum regulated output voltage of the PFC stage divided by SQRT(2), as calculated by the USER, otherwise, for systems that DO NOT have a PFC input stage, enter the maximum AC line input voltage. (enter, in VAC, in cell C15)"  

So you must convert the regulated DC output of the PFC stage into what would be it's equivalent peak AC voltage.  For example: if the PFC output stage has a 390Vdc output, then you should enter 275 in the VAC(max) input.  You must enter the minimum RMS AC line voltage in the VAC(min) cell as the UCC28600 will always start up with the PFC front end disabled (by virtue of the STATUS pin) and so the power stage of the UCC28600 must be designed to start at minimum line voltage (85 Vrms would be entered into the VAC(min) cell for a design using Universal input range even if there is a PFC front end used)

3. You should calculate the desired 90W to 100W design using the design calculated based upon your specific design requirements and not assume the 65W design would be appropriate.  The input capacitor used on the 65W design would be far too small for a 90W design and the primary inductance that is used on the 65W design is much too large for a 90W design.  Please use values that are recommended in the design calculator so that the switching frequency at minimum line voltage, maximum load does not switch less than 80kHz so that the on-time does not exceed the internal QR-done signal. The calculator is designed to output recommended values that will generate a design that meets all of the internal timing and threshold values of the UCC28600.

4. The MOSFET must meet the Vds  stress and Drain current requirements shown in the design calculator, QR Design Tool page under SUMMARY of Ideal Converter Components.  Also consider the peak primary current shown on the same sheet at max load minimum Vbulk (cell G101).  When the MOSFET is selected to meet these calculated Vds, Idrain peak and RMS values, be sure to enter the MOSFET parameters of VDS(max)rating, Coss, Ciss, and Qg into the QR Design Tool spreadsheet as these parameters are required for calculations of switching frequency, turns ratios, etc.

In regards to:

Is there any rule to tune parameters at QR Simulator for matching output current?

I don't quite understand the question...The QR simulator page is designed to show you what the operating parameters are based upon the Design Tool inputs so they are a function of the output power at the output voltage level for your design.

Dear Lisa,

My application is applied on industrial communication equipment, that need to satisfy IEC61000-4-2, IEC61000-4-4, IEC61000-4-5. I think that I should use PFC function. 

1. For your knowledge, is there any TI product for AC/DC converter without having PFC that still can match IEC61000-4-X standard for industrial equipment? 

2. UCC28501(PFC) + UCC286000(Flyback QM Controller) , is this combination suitable for above IEC standard? Or you have better solution and not too expensive than this combination? 

3. 120W EVM is based on above solution, could I base on this scheme to do that if above solution is fine to me? 

4. Follow your suggestion to enter MOSFET parameters of  VDS(max)rating, Coss, Ciss, and Qg into the QR Design Tool spreadsheet as these parameters are required for calculations of switching frequency, turns ratios, etc. 

But one thing still confused me is the output current is higher than my request. I mean 3A output current is my expected, but QR simulator shown up to 10A. What parameters could I do modification? 

And is there any limitation for the switching frequency? Or I need to keep the range between 40kHz and 130kHz for UCC286000?

 Thanks

W.H.

1.  Not that I know of, which is why we make PFC controllers

2.  The UCC28501 and UCC28600 would be a good choice

3. You still need to verify the component values , turns ratio, etc by using the design calculator with your specific requirements but chances are it is a much closer match for your application

4. Completing the input cells as accurately as possible will always increase your first-pass success rate.

I'm not seeing where the output current is listed as 10A (I have enclosed my spreadsheet with 90W, 28V output filled in and preferred values used).  The simulator will show the peak primary side current which looks like 4.65A peak...but I' not seeing 10A.  Did you update the turns ratios, primary inductance, and Rcs, Rpl, Rovp1, and Rovp2 resistor values on the simulator page also?  The design tool tells you what you should use based upon your design requirement inputs BUT you must fill in the BLUE cells on the simulator page as to what you ACTUALLY use to get the simulator results.  It calculates the results based upon the actual values that you use (the blue cells).  This is so you can see what happens using the CLOSEST STANDARD VALUE resistor or have to make concessions with the transformer based upon manufacturability, etc. 

Thanks very much, your example is workable to me after I enter my requirement.

I found an issue about Design Calculator downloaded from TI web site, when first time open this file, and file would link to some address. If we move/copy it to another location, it would make some trouble and would not update user's entering data.

But I am not pure sure what's going on, whether is something about security setup in my computer?

BR

W.H.

Dear Lisa,

I saw the datasheet of UCC28501 described that it provides all of the control functions necessary for an active power-factor-corrected preregulator and a second-stage DC-to-DC converter.

I think that it may have two solutions which is suitable for my application:
1. Only use UCC28501
2. PFC preregulator with UCC28051 and DC-DC converter with UCC28600

Could you help to confirm above two solutions is good for 90W, industrial communication equipment?

By the way, is there any Design Calculator for UCC28501 like UCC28600?

BR
W.H.

Dear Lisa,

For setup VBIAS, is the output of the Aux winding of the Flyback Transforme, we need to consider two things for designing with PFC:
1. UVLO of UCC28600,
   turn-on threshold=13V and turn-off threshold=8V

2. Start up voltage of the PFC controller
   UCC28051: turn-on threshold=12.5V and turn-off threshold=9.7V

That means VBIAS need to large than 13V, and also need to add the forward voltage of rectifier. How about let VBIAS=19.4V?

BR

Using a bias voltage of 19.4V for UCC28600 is okay but I would recommend putting a zener on it so you don't exceed the absolute maximum rating of VDD and keep in mind that fault response is dependent upon the VDD falling below the UVLO turn off threshold so as VDD increases, the hiccup response will be delayed. 

There is a MathCAD design calculator for the UCC28050 that would be applicable with minor modifications to be used for the UCC28051.  I don't think there is an Excel based tool for that device.