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SELV input power supply

John Samperi
Prodigy 120 points
Other Parts Discussed in Thread: LM2588

1st post here.

I have been trying to get this kind of power supply running for a while but I could not get enough stable specifications until recently.

I have tried to get help from a couple of power supply chip manufacturers but did not get anywhere as everyone seem to

cater for off main supply.

=====================

Isolated input to output.

Input voltage: 35Vac-46Vac or wider

50 Hz (47-63 Hz preferred)

Output voltage: 50V 1.2A centre tapped (+25V 0 -25V)

Sine-wave current draw

Power factor between 0.9 capacitive and 0.95 inductive

Temperature range of -5°C to +60°C

=====================

Any hints, design notes ect. appreciated. The magnetics are a bit of a nightmare I guess.  :(

  • 0
    TI__Guru 73215 points

    It looks the ac input will need a ac-dc rectifier and if you have power factor requirement, you would need PFC pre-regulator. You could use a single stage PFC, or use two stage PFC + dc down stream.

  • 0 in reply to Hong Huang
    Prodigy 120 points

    Thanks for the reply.

    I have been thinkering along the same lines for a while ie preregulator with PFC and then a "normal" DC-DC converter , something along the lines of the LM2588, which unfortunately doesn't have a high enough voltage rating but very close application notes, or (excuse the language) a LT3748 with 100V rating.

    So I'm hoping for a more concrete answer, eitheir publicly or in private. Which preregulator with PFC  would be suitable for the above? You have 69 devices coming up as "power correction".

    Entering the min and max voltages upsets Webench or the other calculator. Any assistance with the magnetics? I can probably get some help locally from a company specialising in magnetics. But yes, I DO NEED quite a bit of handholding with this.

     Everything in a particular industry I'm involved with is changing over from off mains (which pretty much all application notes refer to) to a nominal 42V SELV, so there is likely to be several designs required in the near future with different power and voltage requirements but the same input AC voltage.

    I'm touching bases with a few chip manufaturers who may come up with a suitable design.

  • 0 in reply to John Samperi
    TI__Guru 73215 points

    There can be some reduction of the numbers for example, you do not need dual or multi-phase, and you may prefer DCM operation. Also, you may need to decide if fixed frequency or the frequency can be designed. Besides, usually you may want to use newer released ICs. After a couple of such type of exclusions, the number of ICs can be reduced a lot.