• State
  • Locked Locked
  • Replies 4 replies
  • Subscribers 63 subscribers
  • Views 1096 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

UCC28710: No Power comes at out put end

Sachin Bhise93
Prodigy 175 points
Part Number: UCC28710
Other Parts Discussed in Thread: UCC28722, UCC28711EVM-160

Hello,

We are working on Universal input SMPS design using PWM controller UCC28710.

We get reference design from Web bench tool for input Ac of 90-460 Volt  and out put of 12 VDC/2 Amps(24 Watt's)

From tool design suggested components we arranged and assembled on PCB.Except custom part Dsnub and D3 fixed IN4007 and S3M (Diotec).

Recent we have tested power supply with given input supply of 230 Volt Ac, We seen that across pulse transformer input side DC voltage generate.

So what could be the reason for no power comes at secondary side.    

webench_design_4344335_13_455074632.pdf

  • 0
    TI__Expert 7395 points
    Sachin,
    Thanks for your interest in TI here. Have you read through this debug guide for this family of controllers?: www.ti.com/.../slua783.pdf

    Take a look through that and if you would like to discuss further please send us another message.

    Regards
    John
  • 0 in reply to John Stevens
    Prodigy 175 points

    Dear Sir,

    Thank you very much for given troubleshooting document.

    First I have decreased VDD input capacitor and resistor. Cdd comes at 100uF, Rdd at 10E.

    Positive thing is that we got VDD voltage before it didn't come but it's variable in nature from 8-20 Volt continuously.

    Still no power at out put end.

  • 0 in reply to Sachin Bhise93
    TI__Expert 7395 points
    Sachin,
    Thank you for the update. I'll get an applications engineer to help you here more soon.
    Regards,
    John
  • 0 in reply to Sachin Bhise93
    TI__Guru 65945 points
    Hello Sachin,
    The UCC28710 has trickle charge current source to charge the VDD capacitor. The capacitance generally used could be between 1 and 4.7 uF.
    When the UCC28710 reaches UVLO turn on it will give three gate driver pules to sample the output voltage and input voltage. If a fault is detected it will stop gate driver pules and the UCC28722 will discharge the VDD pin to UVLO turn off is reached. This process will repeat until the fault is cleared.
    Faults that can turn off the device are
    1. Output overvoltage fault
    2. Input undervoltage fault
    3. Internal over temperature fault
    4. Primary overcurrent fault
    5. CS pin fault
    6. VS pin fault

    Most likely your fault is 1 or 2. You can figure this out by studying the aux winding, VDD, CS and the flyback input bulk voltage with an oscilloscope.
    1. OVP Trips at VS of roughly 4.6V
    a. Don’t probe the VS pin directly
    b. You can use aux winding and VS divider to calculate.
    2. Input Under Voltage
    a. When the switch is turned on is sensed through the resistor on the high side of the VS divider (RS1)
    b. |VRS1| > IVSL(RUN)*RS1 = 225uA*RS1

    For the UCC28710 to work correctly it is very critical to have a clean auxiliary signal waveform. Please note excessive ringing on the auxiliary waveform can cause the output not to regulate correctly or trip an OVP. Please read the last paragraph on page 13 of the UCC28710 data sheet. It will give guide lines to what the auxiliary waveform should look like. This paragraph refers to figure 15. Please note that OVP can trip after the leakage spike blanking has timed out (tLK_REST).

    Once you have determined why the device is not starting up we will be able to make more recommendations on how to fix and troubleshoot your circuit.

    You also might want to order the UCC28711EVM-160 85V to 265V RMS to 5V evaluation module to use as a reference. www.ti.com/.../sluua12

    Regards,

    Mike