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SMPS Power supply

Other Parts Discussed in Thread: UCC28630, UCC28633, PMP9643, UCC24650

I am working on a new project where i need a dual SMPS power supply with fly-back primary side regulation - 24V@5A and 12V@1A.

I couldn't find any reference design on TI website. Please suggest me any reference design.

  • Somesh,

    The UCC28630-UCC28633 family are worth looking at. They are designed for high power PSR flyback and support CCM operation.

    I assume the AC input range is standard universal mains 90-264 Vac? is a 24 V output at 2.7 A nominal/average, up to 5.5 A peak. This uses UCC28630 with built-in overload timer, this timer prevent continuous operation at peak power, and will time out faster for higher peak level above the nominal.

    If you modify that design to use UCC28633 instead, then you get almost all the same functionality, but without the overload timer, so then it can run all the way to 130 W, assuming the power stage can handle it thermally. This may require bigger heatsinks or maybe bigger power devices. The transformer can handle 130 W (won't saturate), but may need to be made bigger for thermal and/or eff reasons.

    For the 12 V output, you can add another sec winding, or else tap the 24 V winding half-way to get 12 V. Total power for your case is the same as PMP9643.

    UCC28633 also gives you the ability to use the UCC24650 on the secondary side. This is a secondary side voltage monitor and wake-up IC, designed to help overcome the limitation of PSR in the case where the load can step from zero to a high level. Typical PSR at no-load runs at low Fsw min (200 Hz for UCC2863x) for low standby, but heavy load transients can deplete the output cap in between switch cycles, before the primary controller can see the output droop. UCC24650 monitors Vout at every switching cycle, and if a 3% drop occurs with no primary switching, it transmits a wake-up signal back through the power transformer to wake the primary IC early, and react to the load transient immediately. This allows PSR designs to hit very low standby power, yet still compete with opto designs for good transient response from zero-load.

    This app note give a lot more detail and test results:

    I hope this helps you out.

  • Dear Bernard Keogh,

    Thank you for your above details. It was really helpful.