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UCC28740 Reference Design PMP9204

Martin Kirstein
Prodigy 190 points
Other Parts Discussed in Thread: UCC28740

Hello,

i want to use the UCC28740 for my Application (230V AC/5V DC 2A Out). The Demo Board PMP9204  is a good reference.

Now i noticed that the Test Data of the Device for Iin and Efficiency starts at ~200mA.

My application should startup at 50~100mA. So does the device start at 200mA load, or why is this graph made?

Are there any other alternatives for my application, in case this device does not working out?

Greets

  • 0
    TI__Genius 15910 points

    The supply will start up and regulate under no load (0A, open output) conditions all the way up to full load, note the standby power (no load conditions) results reported in section 2 of the test report and the current limit 0plot in section 4 that shows output voltage regulation of 5V at 0.0A at start up and only goes to 0V at current limit conditions in constant current mode.  The dat was not specifically reported in the efficiency section as efficiency is reported at 10% load and above for most requirements.  Output voltage regulation will be well within the 5V range at 50mA load current.

  • 0 in reply to Lisa Dinwoodie
    Prodigy 190 points

    Hey Lisa,

    thank you very much. The Section 4 is a bit strange to me. I can see a straight line at y~=5V, and another line underneath that ramps up from 0V to 2V. How to interpretate?

    Greets

  • 0 in reply to Martin Kirstein
    TI__Genius 15910 points

    The voltage as a function of load plot shows that as the load demand is increased from 0A to full load (approximately 2.2A) the converter is in Constant Voltage (CV)  Mode (meaning it regulates at a constant output voltage of 5V for this design all the way from no load up to full overload current of 2.2A).  As the load demand is increased (the resistance of the electronic load is further reduced so that more current is demanded) the converter transistions into Constant Current (CC) mode meaning that despite the decreasing resistance on the output (an overload condition) the converter will still supply a constant current of 2.2A, no more than that.  This constant output current will remain as the output voltage falls to its minimum voltage (2V as designed by the Aux winding turns ratio) where regulation is no longer possible and the supply will cylcle off. (sse enclosed)

    This is the basic control algorithm of our Constant Voltage, Constant Current controllers. 

    regulation profile.docx
  • 0 in reply to Lisa Dinwoodie
    Prodigy 190 points

    Ahhh =) Amazing!

    Thank you very much.

    Greets from Germany

  • 0 in reply to Martin Kirstein
    TI__Genius 15910 points

    You are most welcome.  This device offers great output short circuit protection because of this control algorithm, not easily achieved in a "normal" flyback.  Let me know if you need any help with designing with this device.

  • 0 in reply to Lisa Dinwoodie
    Prodigy 190 points

    Thank you.

    Well... The most annoying thing in this application is the transformer. I have seen two types of transformers in reference designs: 7508111111 by würth and RLTI-1067 by Renco. Now the problem is, the würth part is not for sale (at least not in stock). And i dont know about the Renco. Any other ideas for good transformers for my 230V AC input / 5V 2A output configuration?

    Greeings

  • 0 in reply to Martin Kirstein
    TI__Genius 15910 points

    Flyback transformers are almost always custom to fit the specific application.  Both Renco and Wurth are very responsive when it comes to providing transformer samples to fit specific applications. 

    Is your input 230VAC, 50 Hz or is it for Univeersal range (covering both nominal 115VAC, 60 Hz and 230VAC, 50 Hz ranges)?  The power stage is designed based upon the minimum bulk voltage so if you are not targeting the 115V range, the transformer design would be different than this reference design.

    You can use the design calculator and get the inductance, turns ratios, etc. for your application or you can email me directly to discuss this opportunity: lisa_dinwoodie@ti.com 

  • 0 in reply to Lisa Dinwoodie
    Prodigy 190 points

    Huhu,

    its mainly planed for 230VAC 50Hz, but i would not say no to universal range, at least there are already transformers suggested.... Already checked that calculator out, but i d love to get some transformers out of the box, because i am not planing to wind them by myself hehe.

    Greets