another type of switching power supply

[Thunderchild]

ok so i've had this idea for some time not getting along that well with coils and high frequency i thought this up:
first a large condenser to "filter" or act as like a backup for a sudden burst be it needed. then i have a square wave generator that has a duty cycle that can be varied by an inputed voltage (the final output as feedback). this will drive a power transistor followed but a very large condenser and then a coil and another condenser as a very low frequency low pass filter to make it all smoth again. another way i thought would be to use a window comparator instead of the variable duty clyce oscilator that would sense the voltage and switch the power transistor on and off in a very small "window" but i do not know if the ripple would be acceptable but it is simpler than the other way. the only problem is isolation in the case of using the mains as the source as the only precaution i know of there is to make sure that GND (negative) is the neutral of the mains supply that in the presence of the earth connection (theoretically present in all mains sockets nowadays but not so much here in italy) i can identify the neutral and automatically switch polarity.
OK so now u can all tell me how nuts i am ! :!:

 

[Thunderchild]

hm am i too radical at least tell me if i'm nuts trying to do another what has been done so and so for years

 

[Phasor]

hm am i too radical at least tell me if i'm nuts trying to do another what has been done so and so for years

Radical, no. Been done before, yes. Sorry to let you down on that one.

 

[Thunderchild]

it has been done ? if so where can i see a few schematics ? what method is used the window comparator or the PWM. it has also occured that a non power version of the window comparator idea could be turned into a PWModulator.

 

[k7elp60]

If I understand what Thunderchild is saying. Comparing the storage charastics of a capacitor or an inductor. It seems to me that the inductor is the better of the two, as with switching power supplies as you increase the current requirements the capacity of the capacitor has to increase, while the value of the inductance decreases.
Another point is the capacitor when is discharges will only provide the level of charged voltage, while the inductor will supply a higher value of voltage than it was charged with.
I'll bet if one were to compare the cubic area of a storage medium for a specified amount of energy, the inductor for it's physical size will store more energy than the same physical size of capacitor.

 

[Thunderchild]

hey hey we getting out of line here i never mentioned an inductor exept as a low pass filter here i am trying to do a circuit that uses only condensers and no complicated inductor circuits. i am only considering lowering at this moment so i do not need the kick of the inductor as in an inverter.

 

[Roff]

To see some examples, look at Linear Technology's offerings by typing "inductorless" in the search window. Note that 75 items appear, covering 34 products. Probably not all of them fit your description, but some do. Nevertheless, I commend you for creative thinking.

 

[zevon8]

One issue I see is the aging of capacitors. They tend not to do so gracefully. Inductors, when properly designed, tend to vastly outlast an electrolytic capacitor. I would imagine the cost to be less also, for a given efficiency.

Hands up all those who have replaced high ESR electrolytics in a SMPS...
Hands up all those who have replaced a shorted inductor in a SMPS...

The inductors carry...

Good thought thou, ideas are what drive industry... never know when the next one is a winner

 

[Roff]

One issue I see is the aging of capacitors. They tend not to do so gracefully. Inductors, when properly designed, tend to vastly outlast an electrolytic capacitor. I would imagine the cost to be less also, for a given efficiency.

Hands up all those who have replaced high ESR electrolytics in a SMPS...
Hands up all those who have replaced a shorted inductor in a SMPS...

The inductors carry...

Good thought thou, ideas are what drive industry... never know when the next one is a winner

Unfortunately, you can't make a capacitorless switcher - no matter how many inductors you use.

 

[zevon8]

Unfortunately, you can't make a capacitorless switcher - no matter how many inductors you use.

Very true, my main point was the failure of large caps compared to large inductors. Smaller caps subjected to lower ripple currents should last longer than soup can caps getting pounded.

 

[Optikon]

Unfortunately, you can't make a capacitorless switcher - no matter how many inductors you use.

Very true, my main point was the failure of large caps compared to large inductors. Smaller caps subjected to lower ripple currents should last longer than soup can caps getting pounded.

For low to medium power switchers, inductors are not that evil to use.
Sometimes, the best part is an inductor and I agree that it will last longer.

These days, quality inductors can be had that are low cost, small footprint and even shielded if you want.

 

[Thunderchild]

basically itm is like this i find it difficult in frequenzy and inductors so i prefer to design where theory is paracticaly the sme as in practice like in digital logic and comparators. it is more predictable if u see what i mean.
however after i finish my course in industrial automation that might all change. :roll: