mosfet switching need help

[jegandren]

Hi all,
i have attached a circuit, the circuit actually compares a voltage output to a reference voltage, say the Vref is 24.9V and Vout is 25V then the switich of the mosfet is off, when the Vout goes below 24.9 Vref, so the mosfet switch should be turned on, the signal control is given by the PIC microcontroller,,,,

Is this method applicable. please advise...

 

[ghydda]

Hi jegandren,

Your idea is not the most widespread way of controlling a converter, but it should work provided you implement enough features in software.

Simply turning the mosfet on when output voltage is too low and turning it off when it is high enough is not recommended. The reason is that you have no way limit the maximum on-time.
And in converter designs this is usually very bad. Should the current in the inductors get too high they will saturate and then there is nothing to control the output voltage.


Cheers,
/Ghydda

 

[jegandren]

hi ghydda,

Actually the reason for the auxiliarry switch (VISI) as attached is for switching when there is a transient drop, during steady state condition the auxiliary switch (VISI) is switched off...when there is a step up of load there would be a slight voltage drop, so based on simulations when an auxiliary switch is given so an additional current would flow to the load and recover the transient undershoot....so i would like to implement it on hardware..

 

[srinu9009]

Hi

i think that your circuit may not work.I saw your zip file .You connected to converters in parallel.if any change in output voltage that will effect both converters.are you tested this?if working please reply to my mail.