Can you make a boost (or buck) converter using a capacitor instead of an inductor?

Thread Starter

jayeshshetty

Joined Jul 3, 2020
2
Forgive my electronics ineptitude if this is a stupid question, but I was thinking that if capacitors are used to store the energy supplied by the bridge rectifier in unregulated AC power supplies then what means they can't be used to store the energy in a boost converter (or buck converter) while the MOSFET (or whatever's switching) is turned off? I looked and couldn't find if this has been done before, so if it's not possible could someone explain to my why? Thanks in advance.
 

jpanhalt

Joined Jan 18, 2008
9,784
Welcome to AAC.

Note that while both component's store energy, the inductor can boost voltage; whereas, the capacitor can boost current, but not voltage.

This link address that: https://electronics.stackexchange.com/questions/451438/what-happens-if-i-interchange-the-position-of-the-inductor-and-capacitor-in-this

As for the "low-pass" filter nature of a boost converter mentioned in the above link, a capacitor would not conduct DC.

Now, using different topologies, you can increase voltage with a capacitor and no inductor:
1) Cockcroft-Walton voltage doubler (https://en.wikipedia.org/wiki/Cockcroft–Walton_generator )
2) A related, switching capacitor voltage doubler: ICL7660 and related charge pumps (https://pdfserv.maximintegrated.com/en/ds/ICL7660-MAX1044.pdf ).
However, those capacitor-based devices are suitable for low currents only.

EDIT: I forgot to mention a common use for capacitors to boost or to invert voltage is to provide bias voltage to LCD displays. All you need is a square wave (such as produced by an MCU). Input goes to C1:

1593771129159.png

Source: http://ww1.microchip.com/downloads/en/DeviceDoc/01146B.pdf
 
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Papabravo

Joined Feb 24, 2006
13,967

Thread Starter

jayeshshetty

Joined Jul 3, 2020
2
Forgive my electronics ineptitude if this is a stupid question, but I was thinking that if capacitors are used to store the energy supplied by the bridge rectifier in unregulated AC power supplies then what means they can't be used to store the energy in a boost converter (or buck converter) while the MOSFET (or whatever's switching) is turned off? I looked and couldn't find if this has been done before, so if it's not possible could someone explain to my why? Thanks in advance.

Thank You So Much
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