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UCC28810: Connection doubts

Part Number: UCC28810
Other Parts Discussed in Thread: TL431, PMP

Dear Sir / Madam,

                                I am  new to power electronics, currently I am also doing the same circuit PFC + Flyback using UCC28810, I have some queries regarding the circuit connection,

1. There are two VDD tags ( next to C7 and R25 ) in the circuit, do i need to connect each other?

2. Like wise, on the transformer secondary side there also 2 VDC tags ( Next to R100 and D11 ), do I need to connect that also?

3. Subject to availability I have used 1N4148 instead of MMSD914 and 1N4007 instead of USK1K -13, I would like to know is it fine to use these alternatives in this circuit ?

I would be very grateful if some could help me with requested information

Reference Design ( page 1 ) : www.ti.com/.../slur512.pdf

 

Thanks in Advance

 

Kind Regards

George Thomas

  • 1. There are two VDD tags ( next to C7 and R25 ) in the circuit, do i need to connect each other?
    [Repy] Yes, they need to connect together.

    2. Like wise, on the transformer secondary side there also 2 VDC tags ( Next to R100 and D11 ), do I need to connect that also?
    [Repy] Yes, they need to connect together.

    3. Subject to availability I have used 1N4148 instead of MMSD914 and 1N4007 instead of USK1K -13, I would like to know is it fine to use these alternatives in this circuit ?
    [Repy] MMSD914 package and footprint is different from 1N4148. If you are ok with 1N4148 package and footprint, then it is ok.
    I cannot find USK1K-13 in the design, and also cannot find its datasheet by searching the web so not sure if ok to replace it with 1N4007.
  • Dear Hong Huang,

                          Thank you for the reply, sorry, there is a correction its US1k-13 ( D6 ) instead of that I am using 1n4007.  And also I would like to know where should I connect the load? Is it across VDC TP3  OR   VDC and VAUX.       ??

     

    Thanks In advance

    Regards

    Novin George Thomas

  • You can use 1N4007 to substitute US1K-13 if you can accept the 1N4007 package and footprint.

    Connect the load between TP1 and TP3 (110V between TP1 and TP3)

  • Dear Hong Huang,

                                  Thanks for the reply, even though problem are there, the output voltage is 63VDC, so i connected a 60VDC 300mA LED string across the output, it glowed brightly and faded to dim the voltage got reduced to 53Vdc, when i remove the load it will rise to 63Vdc. kindly find the other observation and changes i made

    1.  Voltage across IC pin 8 (VDD) and pin 6 (GND) is fluctuating from 15.6V to 10.2V rapidly

    2. Voltage across IC pin 3(VINS) and GND is 1V

    3. Voltage across IC pin 1(VSENSE) and GND is 1.6V,

    Note : Subject to availability I used  820K  for R14 and R15 and 47K 1W for R2 and R5.

    The output voltage is increasing from 0 - 63Vdc very slowly only.

    The transformer is made locally as per the specification below.

    Kindly look into these issues please,  and transformer details are blow

    The transformer winding and inductance details   G095026LF r 6.pdf

  • Are you testing PMP4862? If not, please provide your full schematics for review.

  • Dear Sir,

               Yes I am testing PMP4862 , for a better clarity I am attaching the circuit schematic  which i made the prototype, below. I do believe that is the circuit for PMP4862.1 (Output Voltage 1)

     

    ie: Vin (Min) : (V)85,  Vin (Max): (V)265,  Vout (Nom):  (V)100, Iout (Max):  (A)1.2, Output Power: (W)120,  Isolated/Non-Isolated: Isolated, Input Type : AC , Topology: Flyback- PFC

     

    Kind find the pdf below

     

    3817.Page 1.pdf

     

  • The page 1 circuit output between TP1 and TP3 should be 110V so if you connect a 60V LED string, the string is likely to be burn out.

    The first thing is to make no load output voltage (TP1 to TP3) is at about 110V before you connect LED string. If you want to connect a 60V LED string, then the output voltage needs to adjust to 60V.

    But since you are testing PMP4862, it is better to keep the same output 110V.

    Please disconnect LED Driver A, B and C from the circuit of Page 1 (PFC/Flyback converter). So only test page 1 circuit. At no load, page 1 circuit output voltage between TP1 and TP3 should be about 110Vdc, with ac input 115Vac or 220Vac. Please let me know your test result.

  • Dear sir,

           Thank you for the reply,  I made the prototype of the Page 1 circuit only., I will update the test result tomorrow, need some more time to recheck,

    Kind Regards

    Novin George Thomas

  • Dear Sir,

             Still the output voltage is around 73.5V

    and the irony is Vgs = 0V, Vds: 300V I don't know how the output is getting to  73V that also slowing increasing from 0 to 73V. it will take around 4 mins to reach that level

    Voltages on IC PINS

    Pin 1: Vsense : 1.52 -1.68 V (Fluctuating)

    Pin 2: EAout : 0- 4.9V ( Fluctuating )

    Pin 3: Vinsense: 1- 1.3 ( Fluctuating )

    Pin 4:  Visense: 0V  Pin5: TZE : 0.5V ( Fluctuating )

    Pin 6: GND

    Pin 7: GDRV : 0V

    Pin 8: VDD : 11.10 - 15.20Vdc ( Fluctuating )

    • The previous LED load didn't get damaged !

    My Queries

    1. What may be reason for fluctuating Vdd? Vsense, Vdd & Vinsense is stable when IC is removed
    2. What all are the factors of Output Current ?
  • The output voltage VDC between TP1 and TP3 is controlled by R23 and R28 through TL431 (U3). If  VDC is not at about 110V, you may need to adjust R28 smaller. What are the values of R23, R28, and R9? Please double check and let me know so I can suggest how to adjust these values.

    When you measure Vgs and Vds, you need to use an oscilloscope to measure the waveform. If you use a multimeter, you won't see waveform and the measurement is an averaged voltage. So please use an oscilloscope to measure Vgs and Vds and provide the waveform to me for a review. You also need to use an oscilloscope to measure pin 7. 

  • Dear Sir,

                Thanks for the reply. Here are the values of the requested resistors, below and tomorrow I will try to capture and send the waveform of Gdrv ( IC Pin 7 )

    • R23 : 22K 1/4W
    • R28 : 1M   1/4W
    • R9   : 56E 1/4W


    And also I have another doubt Sir, today I found another reference design ( PMP 4530 ) of LED driver with UCC28810 which has output of 80V 2A ( http://www.ti.com/lit/df/slur337/slur337.pdf

  • I suspect your U3 TL431 has a higher bias current. can you try to reduce R23 from 22k to 20k, so the output voltage should increase from 73V to about 80V? This will confirm your U3 TL431 has a higher bias current so we need to adjust your design other parameters.
  • Dear Sir,

                 At the Gdrv ( pin 7 ) , Vgs  I couldn't find any waveform in DSO. I also suspect one thing, what happens if I used MMBT3906 instead of MMBT2709 ( Q3 )?

  • DRV should have switching waveform otherwise how the converter can have output voltage?
  • Dear Sir,
    I will ensure again tomorrow, What about the query about Q3, can I use MMBT3906 instead of MMBT2907?