lchplsnw
Newbie level 3
Hello,
Recently, I've been playing with flyback SMPS topology for fun but also
to make a reference design for eventual future use in commercial products.
Specifically, what I am experimenting with is a capacitor charger (those
things for which one usually uses a LT3750 or LT3751) and I want to charge
the biggest possible cap in the shortest possible time. Power and efficiency.
One thing I learnt is that when you need higher output voltage, and you
don't have a suitable transformer, ie. when you need high duty cycles, you
start finding that leakage inductance and other problems play a bigger
role. Consider also that I pretend to do all the experiments in software,
on a EF PIC32, and when you use a transformer with 10uH primary inductance,
you are very short in time, especially during the discharge phase of a high
duty cycle when you want to do things like zero-voltage (valley) switching.
Anyhow, experimenting brought me towards the implementation of a two-switch
topology of flyback SMPS, something I had overlooked before. I now understand
the beauty and usefulness of this topology. This way, the transil/snubber is
gone, the MOSFETs can be much lower voltage, and I have a chance (not verified
yet) to measure discharge current with much higher precision and ease (while
measuring discharge current is not necessary, I think I can do some interesting
things if I can measure it).
To experiment (but always with eventual, future, production design in mind)
with it I need a low side and high side driver for the 2 MOSFETs, which do
turn ON and OFF simultaneously albeit on two different "rails", and I want
to drive them directly via a MPU pin, ie. logic level (for my ease and for
containing noise even in imperfect PCB), but I can't find any suitable IC
for this task.
Is there one, or can any of you suggest some smart/clever solutions to drive
with as few components as possible (also to reduce board space and interference
as I'll be switching tens of Amperes, maybe in continuous mode, not even
discontinuos) both MOSFETs simultaneously, considering the ~12V difference
between them?
One a side note: I noticed that the "primary" part of two-switch flyback and
two-switch forward converters are identical, the only difference is on the
secondary side. What are the benefits of implementing a type of secondary
(flyback) or the other (forward)?
Thank you.
Chers,
lchplsnw
Recently, I've been playing with flyback SMPS topology for fun but also
to make a reference design for eventual future use in commercial products.
Specifically, what I am experimenting with is a capacitor charger (those
things for which one usually uses a LT3750 or LT3751) and I want to charge
the biggest possible cap in the shortest possible time. Power and efficiency.
One thing I learnt is that when you need higher output voltage, and you
don't have a suitable transformer, ie. when you need high duty cycles, you
start finding that leakage inductance and other problems play a bigger
role. Consider also that I pretend to do all the experiments in software,
on a EF PIC32, and when you use a transformer with 10uH primary inductance,
you are very short in time, especially during the discharge phase of a high
duty cycle when you want to do things like zero-voltage (valley) switching.
Anyhow, experimenting brought me towards the implementation of a two-switch
topology of flyback SMPS, something I had overlooked before. I now understand
the beauty and usefulness of this topology. This way, the transil/snubber is
gone, the MOSFETs can be much lower voltage, and I have a chance (not verified
yet) to measure discharge current with much higher precision and ease (while
measuring discharge current is not necessary, I think I can do some interesting
things if I can measure it).
To experiment (but always with eventual, future, production design in mind)
with it I need a low side and high side driver for the 2 MOSFETs, which do
turn ON and OFF simultaneously albeit on two different "rails", and I want
to drive them directly via a MPU pin, ie. logic level (for my ease and for
containing noise even in imperfect PCB), but I can't find any suitable IC
for this task.
Is there one, or can any of you suggest some smart/clever solutions to drive
with as few components as possible (also to reduce board space and interference
as I'll be switching tens of Amperes, maybe in continuous mode, not even
discontinuos) both MOSFETs simultaneously, considering the ~12V difference
between them?
One a side note: I noticed that the "primary" part of two-switch flyback and
two-switch forward converters are identical, the only difference is on the
secondary side. What are the benefits of implementing a type of secondary
(flyback) or the other (forward)?
Thank you.
Chers,
lchplsnw