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Патент USA US3079553

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Feb. 26, 1963
D. L. DECKER
OVERLOAD AND ‘SHORT CIRCUIT PROTECTOR FOR
3,079,543
TRANSISTOR VOLTAGE REGULATOR
Filed March 31, 1960
SIGMA:
FIEI
5) awm.
__
27
INVENTOR.
0/: VIP A. D?t'A’E/P
BY Q/(wm 14w
arrests
Patented Feb. 26, 1963
2.
OVERLOAD
Ann _
_
3,%“79,543
SHGRT CIRCUIT PRGTECTUR
, FUR IRANSETQR ‘VQLTAGE REGULATQR
Davidfil. Decker, Cedar'Rapids, Iowa, assignor to Qoliin's
RadioCompany, Cedar Rapids,’ Iowa, a corporation of
Iowa
Filed Mar. 31,-196tt, SenNo. 18,922
1 Claim. (U. 323~22)
the appended claims, it being. understood that such
changes in the precise embodiments of the herein dis
closed information may be submitted as come within the
scope of the claims.
The accompanying drawings illustrate two complete
examples of two embodiments of the invention construct
ed according to the best mode so far devised for the
practical application of the principles'thereof, and in
which:
This invention relates to an voverload and short circuit 10
FIGURE '1 is a schematic circuit diagram of a voltage
protector device and more particularly to a device for
and current regulator having the protector device-of this
use‘ in voltage and current regulators of the type utilizing
semi-conductors to protect the components of the regula
tor against damage due to heavy overloads or shorts in
the output circuit of the regulator.
Voltage and current regulators are well knownin the
art and in the past commonly utilized at least one power
invention incorporated and illustrated as a part thereof;
and"
FIGURE 2 is a schematic circuit diagram of a modi?ed
voltage and'current regulator having. a modi?ed‘protec
tor device incorporated and illustrated as a part thereof.
Referring now to the'd'rawings in'which'like numerals
have been used to identify like characters ‘throughout, the
While it was desirable to protect the regulator, and es
numeral 3' designates generally a voltage and current regu
pecially the power tube, against damage, which sometimes 20 lator, which may be of! conventional type, in which the
required the use of protector devices, thenecessity of such
protector device 4" of this’ invention may be utilized to
aprotector device has. been accented in recent years [due
protect the regulatoragainst damage should a short cir
to the developmentand use of semi-conductors in voltage
cuit or a heavy overload be" connectcd'into its output
and current regulators. This is’ ‘due'to the fact that a
circuit.
semi-‘conductor is far more susceptible to severe damage 25
As shown in‘PIGUR'E 1, Voltage and current regulating
due to the heat produced during excessive conduction of
device 3 may include a power ampli?er 6,‘ which is pref
current than is a vacuum tube.
7
erab‘ly a transistor, andsignal sampling me‘ans'7 to regu
various protector devices have heretofore been sug
late vthe conduction of transistor 6 by controlling the bias
gested and utilized to protect the components, and es;
thereof.
pecially the semi-conductors, used‘ in the voltage and
As ‘shown in they drawings, transistor 6 may ‘be of'the
current reguilato-r against ‘damage due to a short in the
PNPtype' (as shown in FIGURE 1) or of‘ the _NPN' type
output circuit since this obviously would cause heavy
(as shown in FIGURE 2 and designated with the nu
current conduction through the regulator and damage
meral 1%) so long as‘ other circuitry of the‘ regulator is
its components severely in a very short time.
clfianged
accordingly as‘ brought out‘morte'fully herein
Providing a protector device that merely guards against
a ter.
a short in the output circuit, however, is not sufficient,
As‘ shown in FIGURE 1, transistor 6 may have its
of itself, to adequately protect a voltage and current regu
emitter connected with‘ the positive output of a source
lator since a short'in the output circuit is only one pos
of unregulated direct current signal 8 by means of a
sible occurrence which can cause damage to the regulator.
lead it}, its collector connected with a variable output
An additional, and very real possibility of damage, also 40 circuit load 12 by means of regulated output circuit lead
exists in the event that a heavy overload is connected into
14, and its base connected with the negative output of
the output circuit of the regulator, since this too will
source 8 through bias resistor 16' by means of leads 18
amplifying tube to provide the desired regulated output.
cause excessive current conduction‘therethrough.
and 15‘ which are connected to ends 2% and 21, respec
It is therefore an object of'this invention to provide
tively of bias resistor'16. To complete the output circuit,
simple, yet reliable means to protect a voltage and cur
load l2 may also be connected to lead 19 by means of
rent regulator against damage due to either a short or
lead 22. If desired, stabilizing-capacitor 23" may be con
a heavy'overload‘ in the output circuit of the regulator.
nected across output'leads l4 and 22 to prevent'oscillation.
It is another object of this invention to'provide means
Signal sampling means 7, as above-stated, regulates
responsive to the regulator output voltage to bias the
thebias on transistor 6' to therebycontrol the conduction
power ampli?er of the regulator to cutoff whenever a
50 of-the same so that a regulated output is supplied by the
heavy overload or short appears in‘ the output circuit of
regulator. As shown by the drawings, signal'sampl-ing
the regulator to thereby protect said regulator against
means '7 includes a voltage divider 2E which may include
damage due‘ to excessive current ?ow therethrough.
a ?xed resistor 26 and a1 variable resistor 27 serially con
More particularly it is an object of this invention to
nectedrtbetween leads 141a‘n'd22. As shown in FIGURE
provide protector means including a transistor normally
1, the variable tap-23 of resistor 27 may be connected to
biased to cuto? so that said means is operable only when
the b'aseof atransistor'iidof'the NPN type through cur
the regulated output voltage of the regulator drops below
a‘predetermined and preset level to thereafter preclude
further conduction of current through the regulator.
rent limiting resistor Slandf diode 32, which is, or’ course,
connected so that low resistance-is o?ered to base‘ current
?ow.
'It is still another object of this invention to provide
The emitter of'transistor"3tt is connected'to leads 19
60
protector means operable to preclude current flow
and 22 through a breakdown junction or Zener diode
through the regulator after a heavy overload or short is
35, which diode is also connected to input lead 10 through
connected into the output circuit of such a regulator and
bias resistor 36. Diode 35is orientated so that the volt
to‘ maintain said regulator in’ its inoperative state until
age applied to the emitter of-transis‘tor 30 is maintained
such time as the heavy overload or short is removed from
at the breakdown voltage of the diode.
65
the output circuit and the input signal to the regulator
The collector of transistor 36 isconnected to- the base
is thereafter removed and then reapplied.
of - a 'PNP' type transistor 4t} through cur-rent limiting vIre
With these and other objects in view which will become
sistor 41 while the collector of transistor 40 is, in'turn,
apparent to one skilled in the art as the description pro
connected to-side 200i resistor ‘16,- which, as'brought out
ceeds, this invention resides in the novel construction,
provides bias for‘ transistor 6. The emitter
combination and arrangementcf parts substantially as 70 hereinbefore,
of transistor 4% is directly connected to input lead'lu‘by
hereinafter described and more particularly de?ned by
means of leads 45 and 46,‘ and-resistor 1'61 is'therefoi'e
aosaeae
d)
also in the output circuit of transistor 4t}. Forward bias
for transistor 4% is provided by resistor 48 which con
nects the emitter and base of said transistor.
The protector device 4 of this invention includes a
voltage divider 53 which may include ?xed resistance 54‘,
and variable resistance 56, the variable tap 57 of which
viders 25 and 53. It is to be noted that the same decrease
in voltage drop across these dividers occurs in the case
of a short circuit although it is usually much more pro
nounced and acts to short out the dividers completely.
When such a heavy overload or short appears in the out
put circuit of the regulator, the regulator normally tries
may be directly connected to the base of a PNP type tran
sistor 69, as shown in FIGURE 1. The emitter of tran
to supply the necessary voltage to return the output to
is to bias transistor 6 to cutoff as brought out hereinbelow.
' in operation, the voltage and current regulator shown
to the emitter. This causes transistor 3d to conduct at an
increased rate and causes a greater voltage drop across
its former level.
This, of course, can cause excessive
conduction and severe damage through excessive heat to
sister as may be connected with input lead it} through
resistor 52 and connecting leads 46 and 63. A breakdown 10 the components of the regulator and especially to the
power transistor. The protector device of this invention
junction or Zener diode 64 is ‘connected between leads
prevents this excessive conduction in the -following
19 and 63 to maintain the voltage of the emitter of tran
manner.
sistor ed at the breakdown voltage of the diode. In addi
When a heavy overload or a short ?rst appears in the
tion, a capacitor 65 is connected in parallel with diode
output circuit, transistor 6d, which, as brought out here
6d, and this capacitor along with resistor 62 provides an
inbeiore is normally biased to cutoff, will immediately
RC. time constant the purpose of which is hereinafter
start to conduct because of the decreased voltage im
brought out.
pressed upon its base to make it negative with respect to
The collector of transistor 6%} is connected to the base
the emitter. Collector current from transistor so is ap
of transistor 30 through limiting resistor 66 and due to
plied to the base of transistor 3h causing the base of NPN
the orientation of diode 32, collector circuit current must
type transistor 34? to become more positive with respect
be applied to the base of transistor 3%, the result of which
in FIGURE I normally operates in the following manner.
Assuming that the load 12 is increased by an amount not
considered excessive, the voltage potential between leads
14 and 22 will decrease thus decreasing the voltage drop
across voltage divider 25. This means that a lower, or
more negative, voltage is impressed upon the base of
transistor 39, and since it is a transistor of the NPN type, 30
‘conduction inthe base circuit decreases causing a corre
sponding decrease in conduction in the collector circuit.
resistor 48, which‘, in turn causes the emitter of PNP type
transistor 40 to become more positive with respect to the
base. This causes transistor 4% to conduct at an increased
rate and causes a greater voltage drop across resistor 21
which, in turn, causes a greater voltage to be impressed
on the base of transistor 6 biasing the same to cutoff and
thereby rendering the regulator inoperative.
When protector device 4 is caused to operate and bias
transistor 6 to cuto?‘, the voltage regulator will remain
inoperative until such time as the input voltage is re
moved from the regulator. When this voltage is reap
in the voltage drop across bias resistor 48 which is in the
collector circuit of transistor 30. The decreased voltage 35 plied the R.C. time constant provided by resistor 62 and
capacitor 65 is such so as to allow the output to build up
drop across resistor 43 causes the emitter of transistor at}
and bias transistor 64] to cutoff before full voltage is ap
to become less positive with respect to the base so that
plied to the emitter of transistor 69. If, of course, the
conduction in the base-emitter circuit of PNP type tran—
heavy overload or short circuit has not been removed,
sister 40 is decreased. The collector current of transistor
4t) will, of course, likewise be decreased, and since re 40 however, the protective device will again immediately bias
This decrease in current flow, of course, causes a decrease
sistor 16, which provides bias for transistor 6, is also in
the collector circuit of transistor 40, there will be a de
crease in the voltage dropped across this resistor.‘ This
decreased voltage drop across resistor 16 is impressed
upon the input circuit of transistor 6 so that the base of
transistor s to cutoff and render the regulator inoperative.
It is to be appreciated that the protector device of this
invention may be modi?ed by using a transistor of the
NPN type, if the circuitry of the voltage and current regu
lator in which it is utilized so requires, without departing
from the spirit or scope of this invention.
FIGURE 2 illustrates, for example, a voltage and cur
rent regulator 193 utilizing a transistor of the NPN type
sistor 6.
_
in place of PNP type transistors 6 and 40 and a PNP
When the output voltage of the regulator is substantially
type transistor in place of NPN type transistor 3b as
returned to its former level, the bias of transistor d, which
shown in FIGURE 1. The protector device 1% in this
is controlled by the output level, will, of course, be altered
case may utilize a transistor of the NPN type in place of
accordingly to decrease the conduction of transistor 6 to
the PNP type transistor 60 as shown in FIGURE 1.
maintain the output at a predetermined regulated level.
As shown in FIGURE 2, a negative lead 11% is con
The protector device of this invention is normally in
nected to the emitter of transistor 1% while positive lead
operative during the above described normal operation of
119 is connected to the emitter of transistor 1% while
the regulator since this protective network is needed only
positive lead 119 is connected to the base of transistor,
in case of a heavy overload or a short in the output cir
1%. In addition, lead its is a negative output circuit
cuit. This is accomplished by biasing transistor dtl to
lead and is connected with the collector of transistor ltld,
cuto? for normal operation by adjusting variable tap 57
while lead 1212 is the positive output circuit lead and is
of resistor 56 (which is a part of voltage divider 53) so
connected to lead 119. It can therefore be readily appre
that a higher positive voltage is impressed upon the base
ciated that the circuit will operate in much the same
of PNP type transistor do than is present on the emitter.
manner as that of FIGURE 1, but the voltage polarities
Thus the protector device can be preset to become opera
vwill be reversed. For this reason, Zener diodes 35 and
tive at any predetermined output potential by adjusting
65 64 must, of course, be reversed and the same is true of
variable tap 57.
'
diode 32..
From the foregoing it will be appreciated that the pro
in operation, when an increased load, not considered
tector device of this invention will be inoperative until
excessive, is applied to output circuit load 12, the voltage
the potential between output leads lid and 22 decreases
potential between leads All and 122 will be decreased.
to a value that causes the voltage impressed upon the
.base of transistor as to be more negative than the emitter 70 This, of course, causes a decrease in voltage drop across
voltage divider 25 and causes a decrease in the voltage
voltage.
applied‘to- the base of PNP type transistor 13d. it is to
When, for example, output circuit load 12. is increased
‘be-remembered, however, that the emitter of transistor
to such an extent that it constitutes a heavy overload, the
13% is also negative so that a decrease in negative voltage
potential between leads l4 and 22 will be decreased caus
ing a corresponding decrease in voltage drop across di 75 on the base decreases the difference in potential between
transistor 6 becomes less positive, or more negative, than
the emitter, and results in increased conduction by tran
5
the emitter and base.
3,079,543
This causes a decrease in con
duction in the input circuit and will, therefore, decrease
6
ponents from excessive conduction through the regulator
due to a heavy overload or a short in the output circuit
current conduction in the collector circuit. This causes
a decrease in the voltage drop across bias resistor 48 and
of the regulator.
because of the polarity of this voltage drop makes the
A transistorized voltage and current regulating device
of the type having output overload and short circuit pro
emitter of NPN type transistor 140' less negative with re
spect to the base and causes decreased conduction in its
output circuit. This, in turn, causes a decreased voltage
drop across bias resistor 16 and, due to the polarity of
What is claimed as my invention is:
tector means and requiring no operating power other than
that from an unregulated D.C. source, said regulating de
vice comprising: power amplifying means having an in
this voltage drop, the voltage impressed upon the base of 10 put circuit and an output circuit, said input circuit in
NPN type transistor 106 makes the base less negative, or
cluding resistance means for biasing said power ‘amplify
more positive, with respect to the emitter and causes in
creased conduction in the output circuit to return the volt
age potential between output leads 114 to 122 to the de
sired level.
If, however, a short or a heavy overload is connected
into the output circuit of the regulator, protector device
104, which has been modi?ed by replacing the PNP type
transistor shown in FIGURE 1 with a transistor of the
NPN type as brought out hereinabove, will conduct to
bias transistor 106 to cutotf and render the regulator
ing means and said output circuit including voltage di
vider means; means adapting said input circuit for con
nection with an unregulated D.C. power source; means
adapting said output circuit for connection with a load so
that said load is in parallel with said voltage divider
means; output voltage sampling means connected be
tween said voltage divider means and said resistance
means to determine and regulate the bias on said power
amplifying means; a transistor having an input electrode,
inoperative. This is accomplished by applying the col
a control electrode, and an output electrode; a Zener
As described in connection with FIGURE 1, the regu
ing said output electrode with said voltage sampling means
for coupling an output signal thereto while said transis
diode connected with said input circuit and with said in
lector current of transistor 160 to the base of transistor
put electrode for assuring that a constant voltage is ap
130 in the same manner as that described in connection
plied to said input electrode; means for applying direct
with the protector device shown in FIGURE 1. This 25 voltage from said voltage divider means to said control
impressed voltage causes increased conduction in PNP
electrode to normally bias said transistor to cutoff, said
type transistor 130, which in turn causes increased con
transistor remaining in a nonconductive state until a
duction in transistor 140. The resulting increased volt
load connected with said output circuit draws excessive
age drop across resistor 16 impresses a more negative
current causing said transistor to conduct, said transistor
voltage on the base of NPN type transmitter 106 and 30 then remaining in said conductive state until the power
causes the same to be biased to cutoff.
lator shown in‘ FIGURE 2 will likewise remain in a non
from the unregulated source is removed; means connect
operative state until such time as the input signal from
tor is in a conductive state to bias said power amplifying
source 9 is removed from the input leads 110 and 119 35 means to cutoff; and an RC. network including a capaci
and then reapplied since the emitter of transistor 160 will
tor in parallel with said Zener diode and a resistor hav
remain more negative than the base until the signal is ?rst
ing one end connected to said input electrode and the
removed from this emitter.
other end connected to said input circuit whereby said
While two speci?c examples have been shown and illus
R.C. network prevents the application of breakdown volt
trated herein to adapt the protector device of this inven 40 age to the input electrode of said transistor for a pre
tion to a speci?c voltage and current regulator, it is to
determined time interval immediately after power from
be appreciated, of course, that the protector device of
the unregulated source is coupled to said regulating de
this invention might be modi?ed to meet other speci?c
vice to thereby allow cuto? bias to ?rst be impressed
circuitry requirements without departing ‘from the spirit
upon the control electrode of said transistor.
or scope of this invention.
References Cited in the ?le of this patent
In view of the foregoing it should be obvious to those
skilled in the art that the protector device of this inven
UNITED STATES PATENTS
tion provides simple yet reliable means for protecting a
2,915,693
Harrison _____________ __ Dec. 1, 1959
voltage and current regulator against damage to its com
2,922,945
Norris et a1. _________ __ Jan. 26, 1960
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