# Curent Fed Inverter / Voltage Fed inverter

Discussion in 'Electronic Basics' started by srg, Mar 11, 2006.

1. ### srgGuest

Dear Group,

Could someone please kindly explain the topology of current fed inverters.
I wish to drive a parallel tank circuit with the out put of the inverter.
What I do not understand is the topology of the source circuit ie :-
As I understand it ---
A voltage fed inverter users a 240 AC line into a bridge rectifier which
converts to DC that is then fed to a cap for smoothing which then supplies
the inverter.
A current fed inverter users a 240v AC line into a bridge rectifier which
converts to DC that is then fed to an inductor in series which then supplies
the inverter.
How does one calculate the value for the inductor?

Regards
Steve

2. ### Paul MathewsGuest

When you switch the power stage of a switchmode converter, something
has to limit the current into the output capacitors. Normally, an
inductance does the job. You can have inductance on the primary side,
on the secondary side, or both. When you put the inductance mostly on
the primary side, this is called "current fed". One way to calculate
the desired inductance: for the lowest voltage across the inductor
(i.e., low line conditions) and the longest allowable switching
interval (on-time), the inductance should not limit the change of
current to less than what is required to deliver rated power through
the converter:

V = L di/dt

A vague answer for a vague question.

Paul Mathews