i'm planning to build a bench power supply, it takes from mains and a transformer brings it down to 22v ac which i'd rectify into DC. for that matter whether it is rms we'd set it aside for the moment.

And to convert that 22v (possibly higher if the specs is after all rms), i'm intending to use buck converters to convert (dc-dc) it down to lower voltages.

Hence, i started doing some spice simulations to anticipate what to expect.

here is the model i'm using for my buck converter simulation

View attachment buck1.cir

i'm rather surprised by the long settling times when i wanted 3 volts out of 22 volts, and i'm using a rather low 10 ohm load resistance.

if i change that 10 ohm load to 100 ohm, (e.g. for small mcu, even tens of milliamps is plenty), the settling time stretch out extremely and this same chart is still well above 15 volts at the end of that 3ms.

the other thing is as the buck converter start settling from 22v VIN, at 22v it would probably blow semiconductors, mcus e.g. for those 3v ones some of which won't be able to take a voltage any higher than 3.6v

any idea what could be a better way to deal with very small loads (e.g. tens of milliamps ) or even possibly disconnected - no load, and large dropout to small voltages, as well as the high initial voltage ?

And to convert that 22v (possibly higher if the specs is after all rms), i'm intending to use buck converters to convert (dc-dc) it down to lower voltages.

Hence, i started doing some spice simulations to anticipate what to expect.

here is the model i'm using for my buck converter simulation

View attachment buck1.cir

i'm rather surprised by the long settling times when i wanted 3 volts out of 22 volts, and i'm using a rather low 10 ohm load resistance.

if i change that 10 ohm load to 100 ohm, (e.g. for small mcu, even tens of milliamps is plenty), the settling time stretch out extremely and this same chart is still well above 15 volts at the end of that 3ms.

the other thing is as the buck converter start settling from 22v VIN, at 22v it would probably blow semiconductors, mcus e.g. for those 3v ones some of which won't be able to take a voltage any higher than 3.6v

any idea what could be a better way to deal with very small loads (e.g. tens of milliamps ) or even possibly disconnected - no load, and large dropout to small voltages, as well as the high initial voltage ?

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