Is it possible to design a buck converter using a charged capacitor to get regulated voltage output? When the capacitor voltage falls below some threshold value the inductor should be able to provide output across the load resistance(during this time the source capacitor will be charged).
Electronic – Powering buck converter using charged capacitor
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Related Solutions
The basic answer to your misunderstanding is that the load and the input voltage are NOT connected directly when the switch is closed. The inductor is between the two.
Voltage accross a inductor can change quickly, but current only changes proportional to the applied voltage. In other words, the current will ramp up slowly. The load only sees the current coming out of the inductor. If the switch were to remain closed, that current would eventually build up too much voltage on the capacitor. However, the switch is only closed for short periods and with a average duty cycle so that the average current coming thru the inductor is exactly what is needed to maintain the desired voltage on the output capacitor.
But a Low Pass filter is the one that attenuates frequencies higher than a desired frequency and passes the lower frequencies. So How does this definition fit in this case?
The important thing you haven't grasped is that the on-off square wave has an average level that is totally dependent on the duty cycle. This mathematically average level gets converted to a real dc level by the L and C low pass filter action.
Here's a square wave that rises to 3V from 0V (gold trace): -
The blue trace has a little bit of low pass filtering applied - can you see that if a lot more low pass filtering were applied, the blue trace would be almost a constant DC level of 1.5 volts?
Best Answer
Yea, of course it is.
In a buck converter, the switch (you have drawn) opens and closes at a certain rate and duty cycle. Current is only consumed from the input (capacitor) during the on-time of this switch. What happens during the off-time is irrelevant, and you could use that to recharge the capacitor.
This is not necessarily a good idea; you need additional switches, and in most circumstances, it doesn't perform any better than just leaving the input voltage source permanently attached.