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5V, 5W isolated power supply requirement with 10 to 20VAc, 45 to 60Hz input

prabhakara vittala
Prodigy 30 points
Other Parts Discussed in Thread: UCC2800

Hello,

Need to design AC to DC converter with following specifications.

AC input voltage : 10 to 20VAC, 45 to 60Hz

Output voltage: 5V

Output power = 5 to 10 watts

Isolation = 4KVrms

This power supply has to work only at low voltage mode (10 to 20Vac) and should not function when the ac line is at high power (110 to 230Vac, ) mode.

The AC lines are coming from the inverter which can operate at low and high power mode.

looking for your suggestions to design for the above requirement.

Thanks and regards,

Prabhakara

  • 0
    TI__Mastermind 31580 points
    Hi Prabhakara,

    The UCC2800 family of PWM controllers can operate down to low Vcc levels so are ideal for these input voltage ranges.

    TI's webench tool may also provide a range of paper designs that you can choose from.

    It is unlikely that TI has an existing AC/DC designs at this input voltage level. Prehaps one could be adpated from a dc/dc solution with some modification to the transformer design to provide the required safety rating.

    Regards

    Peter
  • 0 in reply to Peter Meaney
    Prodigy 30 points

    Hi Peter, 

    Thanks for the update.

    I would like to know will this chip will function with input AC voltage range of 10 to 265V also?

    Also would like to know if have taken the design from the TI webench, what is the success rate of the suggested design?

    Is there any tool with TI for selecting the transformer?

    Regards,

    Prabhakara

  • 0 in reply to prabhakara vittala
    TI__Mastermind 31580 points

    Hi Prabhakara,

    The IC will work over a wide range on input voltages provided its Vcc pin is connected to a circuit that provides it with the correct voltage range. In the circuit above the Vcc pin is fed through a resistor chain from the rectified AC input. The resistor chain forms an RC time constant with the Vcc cap so start-up times will vary with AC line voltage.

    So the controller can be used over a wide range of input voltages if the requirements of the Vcc pin are met. The usual limitation is the power stage capability to work over wide input voltage ranges, we have designs that work over 1:10 input voltage range eg, 100V to 1000V, but 10V to 265V is 1:26.5 which will not be possible to achieve with a single stage design.

    In general some optimistaion will have to be done with the circuit values to tune the performance of the design based on the Webench design. TI has a power stage designer tool which will help with the basic specs of the transformer, then you can contact vendors like Wurth-midcom or Renco who can supply sample transformers for prototype development.

    TI has a lot of technical articles on power supply design like this one which covers the flyback transformer design,

    However TI does not have a transformer design tool.

    Regards

    Peter

  • 0 in reply to Peter Meaney
    Prodigy 30 points
    Hi,

    Where can i find the all design calculation?

    Regards,
    Prabhakara
  • 0 in reply to prabhakara vittala
    TI__Mastermind 31580 points
    Hi Prabhakara,

    The datasheet for the controllers have a step by step design guide that takes you through the design calculations.

    See section 10 of the UCC2800 datasheet as an example.

    Regards

    Peter