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TPS62110: About isolation application of non-isolated DC/DC? (Another question)

Pokkun
Genius 4695 points
Part Number: TPS62110
Other Parts Discussed in Thread: TPS55010, TPS62135

Hi, team.

My customer is looking for an alternative to BD7F100EFJ-LBE2 (made by ROHM).

This application's specification is "12V(2W@MAX)⇒ISO DCDC⇒12 V".

But, my customer is considering diversion to another application, too.

(Its specification is "12V⇒ISO DCDC⇒5V")

I have been introducing TPS62110RSAR with reference to the document of PMP20450, but please let me teach because got a question from the customer.

※If you can answer "usable" it seems that the considering will be progressing.

<Customer Question>

TPS62110 is a normal synchronous rectifier converter.

① I think that this IC is not an insulation dedicated IC, but can it be used?

If the answer is "YES" please tell me following under.

② Difference in internal structure with DC-DC dedicated for insulation by competitor product

③ The risks (demerit) when used for isolation.

④ Installation result used for isolation.

Could you help me?

Best regards,

Masumi Sekiguchi

  • 0
    TI__Guru**** 150650 points
    Correct. The TPS62110 is not somehow specially designed for isolated applications. It is a standard step-down (non-isolated) converter. With its forced PWM mode, it can be used in a flybuck topology as in PMP20450.

    Neither a flybuck topology nor the Rohm device have anything special regarding isolation. Both circuits are entirely referenced to the primary side of the transformer, with no active feedback from the secondary side.
  • 0 in reply to Chris Glaser
    Genius 4695 points
    Thank you for your response.

    To propose a synchronous rectification step-down converter to insulation applications,I understand that there is no problem.

    However, in that there is not much difference from the usual Flybuck power supply,
    Please let me ask you a question.

    Question: While there are plenty of TI's 5V step down converters,
    Why is it to commercialize insulation dedicated DC / DC like TPS55010?

    ＜Background of questions＞
    The customer is saying…
    ・Special consideration for isolation applications is required so are you developed and selled it as a separate product?

    Please tell me.
    Masumi
  • 0 in reply to Pokkun
    TI__Mastermind 23695 points
    Some changes were needed to make it a better solution for the isolated supply application. Making the low side sinking current lower (more negative) allows more output power.

    Best Regards,
    David
  • 0 in reply to David_Daniels
    Genius 4695 points

    ①If you use an IC without "low side sinking current lower" for the isoulation solution (with the usual synchronous rectification step-down converter),

    what kind of characteristics will be affected to ?

    ②Also, what kind of applications did you use Document "PMP20450" on a worldwide market?

    Best regards,

    Masumi Sekiguchi

  • 0 in reply to Pokkun
    TI__Guru**** 150650 points
    I think section 8.4 in the TPS55010 D/S does a good job as explaining the basics of the flybuck topology. As described there, the actual power transfer to the secondary only occurs when the current through the transformer primary is negative. Having a current limit closer to 0 therefore limits the output power.

    This design is useful when you need an isolated supply that can support some power. One example is the gate driver for a higher power isolated supply.

    Instead of the TPS62110, you might look at the TPS62135 which can perform the same function. It also has a forced PWM mode.