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Re: Solid State Voltage and Current Regulator (fwd)
From: Bill Lemieux[SMTP:gomez-at-netherworld-dot-com]
Sent: Wednesday, January 07, 1998 5:22 PM
To: Tesla List
Subject: Re: Solid State Voltage and Current Regulator (fwd)
Richard Wayne wrote:
> Harri's observation about these series pass transistors are analogous
> to large variable resistors is partially correct. Resistor are always
> fully on and are incapable of functioning in a cut off mode. These
> transistors dissapate virtually no power in the full on mode or cutoff
> mode.
Cut off mode I'll believe, but no power dissipation in full on mode?
That's hard to believe. What is their forward drop? Since any BPT is
essentially two back-to-back diodes, the forward drop is usually at
least a few tenths of a volt. That equates to a lot of dissipated power
when they are fully conducting. Are these by any chance Insulated Gate
Bipolar Transistors? I hear that IGBTs have _very_ low forward drop,
and I see them being used in some of the higher-end lighting dimmers in
place of SCRs these days- their ability to turn on at any desired speed
eliminates the need for a filter inductor.
Following this thread with considerable interest,
Gomez
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