> Hello,

> I designing a DC/DC with LM3477. The data sheet specifies that the duty
> cycle of the PWM output is about D=Vout/Vin which is independent on the
> output current (see page 13,
> http://www.microchip.com/1010/suppdoc/appnote/all/picref2/index.htm).

> If the duty cycle is fixed and independent of the output current, then
> how is the regulation done when for example the  load increse its
> current consumption ?

> Thanks,

> Tal

If Vin remains constant under the increased load, then no increase is
needed in the duty cycle. This will not happen in real life; Vin will drop
which is why a regulator is needed. As Vin decreases, D will need to
increase to compensate for this, keeping the equation accurate.

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