TRADUCTION NON-DISPONIBLE

SWITCHING DEVICE

Abrégé anglais

Abstract of the Disclosure.
According to the invention, a switching device based
on an active switching element is built around an operatio-
nal amplifier featuring two switching components connected
in series in the negative feedback circuit. The positive
feedback circuit of the operational amplifier comprises a
voltage divider having two resistors and an operational am-
plifier whose non-inverting input is coupled to the centre
tap of the power sources of both operational amplifiers and
the output busbar. The inverting input of the operational am-
plifier of the voltage divider is connected to the non-inven-
ting input of the operational amplifier of the active switch-
ing element whose output is coupled to the output of the ope-
rational amplifier of the voltage divider via series-connec-
ted resistors. One of the resistors is connected between the
output and the non-inverting input of the operational ampli-
fier of the active switching element.
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Revendications

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A switching device based on an active switching
element, comprising:
(a) a first operational amplifier having a negative
feedback circuit and a positive feedback circuit, an inverting
and a non-inverting inputs and an output;
(b) an input busbar;
(c) a control busbar;
(d) first and second switching components connected in
series and connected to said negative feedback circuit of said
first operational amplifier, said first and second switching
components having control inputs connected to said control busbar
and a centre tap of said first and second switching components
being connected to said input busbar;
(e) a voltage divider connected to said positive feed-
back circuit of said first operational amplifier;
(f) a first resistor in said voltage divider, said
first resistor being connected between said output and said
non-inverting input of said first operational amplifier;
(g) a second resistor in said voltage divider and
connected in series with said first resistor;
(h) a second operational amplifier in said voltage
divider and having a non-inverting input and an inverting input
and an output, said output of said second operational amplifier
being connected through first resistor and said second resistor
in series to said output of said first operational amplifier;
said inverting input of said second operational amplifier being
connected to said non-inverting input of said first operational
amplifier;
(i) an output busbar;
(j) a first power source and a second power source

for said first operational amplifier and said second operational
amplifier, said first and second power sources having a centre
tap connected to said output busbar and said non-inverting
input of said second operational amplifier.

Description

6~4
.
This invention relates to means of electric signal
switching and, in particular, to a switching device.
; The invention can be used in multistage switchgear
installations.
There is known a switching device (U.S.S.R. Inventor's
Certificate No. 427,473, published May 5, 1974) which is an active
switching element built around an operational amplifier with
two series-connected switching components in the negative feed-
back circuit and a voltage divider in the positive feed-back
circuit. The voltage divider comprises two series-connected
potentiometers, the slide of the first potentiometer being
connected to the output of the operational amplifier via a
capacitor, whereas the slide of the second potentiometer is
connected to its non-inverting input. When switching elements
are turned on, the operational amplifier is enveloped by negative
and positive feedback circuits and the transient resistance of
the switching element is reduced to an insignificant value.
However, the value and instability of the transient resistance
grow considerably with the variation of the frequency of the
switched electric signal. This drawback causes errors in
switching-, when the frequency of the switched signal changes,
and limits the area of application of switching devices base on
an active switching element featuring two feedback circuits.
The object of the invention is to increase the accura-
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changing within a wide frequency range.
According to the present invention there is provided
a switching device based on an active switching element,
comprising: a first operational amplifier having a negative
feedback circuit and a positive feedback circuit, an inverting
and a non-inverting inputs and an output; an input busbar; a
control busbar; first and second switching components connected
in series and connected to said negative feedback circuit of
said first operational amplifier, said first and second switching
components having control inputs connected to said control
busbar and a centre tap of said first and second switching
components being connected to said input busbar; a voltage
divider connected to said positive feedback circuit of said
first operational amplifier; a first resistor in said voltage
divider, said first resistor being connected between said output
and said non-inverting input of said first operational amplifier;
a second resistor in said voltage divider and connected in
series with said first resistor; a second operational amplifier
in said voltaye divider and having a non-inverting input and an
inverting input and an output, said output of said second
operational amplifier being connected through first resistor and
said second resistor in series to said output of said first
operational amplifier; said inverting input of said second
operational amplifier being connected to said non-inverting
input of said operational amplifier; an output busbar; a first
power source and a second power source for said first operational
amplifier and said second operational amplifier; said first
and second power sources having a centre tap connected to said
output busbar and said non-inverting input of said second oper-
ational amplifier~
The invention will now be described in more detail,
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B

by way of example only, with re~erence to the accompanying
drawings, in which the single figure is a circuit diagram of a
switching device in accordance with one embodiment of the
invention.
A switching device, according to the invention, based
on an active switching element is built around an operatio-
.
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6 O~ ~
nal amplifier 1 whose negative feedback circuit comprises
series-connected switching compone~ts 2 and 3. ~he positive
~eedback circuit comprises a voltage dividex having an
operational ampli~ier 4 ~hose non-inverting input 5 is ccn-
nected to an output busbar 6 and a center tap 7 of power
sources 8 and 9 of the operational amplifiers 1 and 4. 3e-
sides, the voltage divider ha.s two series-connected resis-
tors 10 and 11, the resistor lO being placed between a non-
inverting input 12 and an output 13 of the operational am-
plifier 1, which is also connected to an output 14 ol the
operational amplifier 4 via t~e resistors 10 and 11. An in-
verting input 15 o~ the operational amplifier 4 is connected
to the non-inverting input 12 of the operational amplifier 1.
An input busbar 16 of the device is coupled to the switching
components 2 and 3 connected ~n the center tap 17 and their
control electrodes 18 and 19 are connected to a control bus-
bar 20.
~he switching device operates as follows.
~ he signal supplied fro~ the control busbar 20 closes the
switching components 2 and 3. A certain transient resistance
is set between the input busbar 16 and the OUbput busbar 6.
~he output voltage of the operational amplifier 1 is applied
via the voltage divider, its one leg being the resistor 10
and the other being the ~requency dep~ndent resistance of the
circuit comprising the operational amplifier 4 featuring the
resistor 11 in the negative feedback circuit, to the non-in-
verting input 12 of the operational amplifier 1. ~he frequency
function of the voltage divider transmission ratio is opposite
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to the frequency fu~ction of the voltage transmission ratioo~ the operational ampli~ier 1. ~hat is why the output volt-
age of the operational ampli~ier 1 is maintained constant
through a wide fre~uency range. As the output voltage of the
operational amplifier 1 is constant, the transient resistance
between the input and output busbars of the device is also
kept constant and close to zero. As a result the accurac~ of
commutation is increased with variations o~ the frequency of
the electric signals within a w~e range.
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