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TPS55010: Is adjusted Output Voltage "Voltage at no load"? or ""vout at load ?

Masaharu Takahashi
Expert 4170 points
Part Number: TPS55010

Hi, Team.

i've been asked by Customer as below.

in datasheet, it shows Vout equation , is it "at no load" or "with some load"?

the reason why customer asked me is...

basically Vout would be decreased from no load to light load.

customer uses LDO which has limitation Vdrop , if the voltage in its datasheet mentioned, customer just places some load as "pre load" to be stable.

and , is there any equation to know the voltage at no load and some load from equation ?

  • 0
    TI__Guru**** 191445 points

    Takahashi-san,

    Equation 1 is for the nominal ideal primary voltage needed to get the nominal ideal output voltage using the ideal turns ratio and nominal forward voltage drop of the diode of equation 2. It is independent of load current. As you can see by the load regulation graph of figure 27, tho voltage vs load current regulation for this topology is not particularly tight. You may see a large variation with load current.  Calculation of the load regulation is probably not simple.

  • 0 in reply to JohnTucker
    TI__Guru**** 191445 points
    Takahashi-san,

    For a Flyb-uck converter the primary side voltage is regulated by the closed loop control loop. The isolated output voltage is achieved by rectifying the the output of the secondary winding when the low side FET is ON. Checking the available literature, the load regulation is affected by the winding leakage inductance, winding resistances, rectifying diode drop and low side FET RDSon. At higher loads, the diode drop and winding resistance dominate so long as the leakage inductance is low. I do not see an equation for it. It could be derived, but probably not today.
  • 0 in reply to JohnTucker
    TI__Guru**** 191445 points
    Takahashi-san,

    You may also want to consider a pre-load resistor to ensure you are operating in the more linear region.