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Pulse Assisted Silicon Controlled Rectifier Gate

IP.com Disclosure Number: IPCOM000112018D
Original Publication Date: 1994-Apr-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 2 page(s) / 70K

Publishing Venue

IBM

Related People

Malloy, SJ: AUTHOR [+2]

Abstract

The "gate" input of a Silicon-Controlled Rectifier (SCR) is used to turn the SCR on and off. SCRs have the additional characteristic that they will not turn off as long as a voltage is applied and electrical current is passing through the device. Switching of AC power lines can be accomplished using SCRs as conduction devices and a suitable control circuit to operate the gate signals [1,2].

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Pulse Assisted Silicon Controlled Rectifier Gate

      The "gate" input of a Silicon-Controlled Rectifier (SCR) is
used to turn the SCR on and off.  SCRs have the additional
characteristic that they will not turn off as long as a voltage is
applied and electrical current is passing through the device.
Switching of AC power lines can be accomplished using SCRs as
conduction devices and a suitable control circuit to operate the gate
signals [1,2].

      A referenced DC voltage is sufficient to activate a SCR gate
and to maintain the SCR operation through current outages such as
those experienced in an AC power line.  A simple DC voltage, however,
may not be economical, or may not provide the desired turn-on speed.
This is because the amount of energy needed to activate the SCR gate
is much less than that required to maintain the gate.  Therefore, a
DC-powered gate with sufficient charge to activate the gate will be
oversized once conduction has begun.  Conversely, if the gate drive
is sized for maintenance of the gate signal, it will be insufficient
to activate the gate quickly during turn-on.

      A similar situation occurs when a SCR gate is deactivated.  In
this case, the SCR will continue to conduct current while a positive
bias exists.  Some SCR switching applications, however, call for
turning ON a corollary SCR immediately following the deactivation of
the first SCR.   Residual charge on the first SCR's gate may allow
reconduction to occur, essentially shorting the two power supplies
and possibly causing considerable equipment damage.

      In this case ...