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Re[2]: [Discuss-gnuradio] DC-DC converter

From: Cory Papenfuss
Subject: Re[2]: [Discuss-gnuradio] DC-DC converter
Date: Mon, 6 Dec 2004 11:09:09 -0500 (EST)

My  concern  would be how the inductors tend to smack the diodes. Once
the  diode  gives  in  to  being  smacked around by the inductor, your
4702/4707  is  the  next  target.  If you pull/break the diode on many
simple   charge  pump  circuits,  it  simply  stops  working.  If  you
pull/break the diode on the inductive buck circuit, it tends to create
what  ever  voltage  the inductor desires. The inductors are defiantly
better  for  the  power output. The charge pump definitely can't touch
the 3 amps.

Best regards,

Jared Harvey                        HAM KB1GTT

You are both right and wrong. A *properly designed* power electronic circuit does not abuse any device except as a second-order effect (requiring snubbers, limiting di/dt and dv/dt, etc). If you do not design it correctly and have "shoot-through" faults (for a voltage-source converger, i.e. capacitor) or "open" faults (for a current-source, i.e. inductor) then you will destroy the devices. A switched capacitor circuit abuses the devices as a *first-order* operating parameter (i.e. connecting capacitors directly across voltage sources/sinks means *huge* current spikes.) A proper power electronics circuit simply passes the "baton" (voltage to inductors and current to capacitors) gracefully.

For the buck circuit you mentioned it's true that if you remove the diode the switch will blow up. That is the "open" fault to be avoided for the current-source converter. If the circuit is properly designed, the diode won't fail.


* Cory Papenfuss                                                        *
* Electrical Engineering candidate Ph.D. graduate student               *
* Virginia Polytechnic Institute and State University                   *

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