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Патент USA US3051856

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Aug. 28, 1962
1.. J. MlNTZ ETAL
3,051,852
TRANSISTORIZED CIRCUIT BREAKER NETWORK
Filed Nov. 19
1958
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Aug. 28, 1962
3,051,852
L. J. MINTZ ETAL
TRANSISTORIZED CIRCUIT BREAKER NETWORK
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INVENTORS.
LEON J. Mmrz
ROLAND Yi i
BY 66; 7%,“.
Aug. 28, 1962
3,051,852
L. J. MINTZ ETAL
TRANSISTORIZED CIRCUIT BREAKER NETWORK
Filed Nov. l9,_1958
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LEON
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United ttes Patent 0 f
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3,651,352
TRANSISTORIZED CIRQUHT EREAKER NETWURK
Leon J. Mintz, Brooklyn, N.Y., and Roland Yii, West
Chester, Pa., assignors to Burroughs Corporation, De
troit, Mich, a corporation of Michigan
Filed Nov. 19, 1958, Ser. No. 774,979
11 Claims. (Cl. 307-835)
3,051,852
Patented Aug. 28, 1962
2
a predetermined value. A quick-acting switch means,
selectively activated by the current sensitive means, elec
trically decouples the regulated transistorized power sup
ply from the load impedance when the current sensitive
means changes its state of conductivity. If a bistable net
work is utilized as the quick acting switch means it will
insure positive decoupling of the load impedance from the
regulated transistorized power supply before permanent
damage can be sustained by the transistors in the regulated
This invention relates generally to an electrical overload
protective network and more particularly to a quick acting 10 power supply.
tran-sistorized circuit breaker network which can protect
a regulated transistorized power supply from permanent
damage due to the occurrence of a short in the load circuit.
With reference to FIG. 1, there is illustrated in accord
ance with the principles of this invention a transistorized
circuit breaker incorporated within a regulated transis
torized power supply network. A transformer 10 supports
Regulated transistorized power supply networks are sim
{ple in design, economical to build, and reliable in opera 15 a primary winding 12 and a center tapped secondary wind
ing 14. The primary winding is connected to a source of
tion. Unfortunately, however, extraordinary care must be
A.C. potential through input terminals 16 and 18. A ?rst
exercised to prevent the occurrence of a short in the load
crystal diode 20 is positioned between one end of the
circuit as the large current drain through the power supply
secondary winding 14 and a terminal ‘24, and another
will frequently destroy the power transistor; even when
crystal diode 22 is positioned between the other end of
the power supply is protected by a fuse.
the secondary winding 14 and terminal 24. In this ?gure,
Presently, fuses are utilized within regulated transis
the diodes 20 and 22 are oriented to permit the passage of
torized power supplies to protect the components from de
a negative potential signal to the terminal 24 relative to
struction due to an overload condition. However, a fuse
the potential signal on the center tapped terminal 46 of the
will not operate or blow to interrupt the ?ow of current
through a circuit unless exposed to an overload condition 25 secondary winding vl4.
A power transistor 28 designated as a PNP type supports
for a speci?c interval of time. This condition can be
a collector terminal 26, an emitter terminal 32, and a base
referred to as a thermal lag, the time required before the
terminal 30. The collector terminal 26 is coupled to the
conductive fuse element reaches its melting point. Ex
terminal 24, the emitter terminal 32 is coupled to a ground
perience has shown that when an overload condition oc
terminal through a tapped reference resistor 34 positioned
curs, such as is caused by the presence of a short or partial
short in a load circuit, the large current drawn will usually
destroy the transistor before the fuse will “blow.”
in shunt with the load impedance 36, and the base terminal
30 is connected to a collector terminal 38 of a transistor
40 designated as a PNP type. The transistor 40 also sup
ports a base terminal 44 which is coupled to the sliding
modi?ed by decreasing the time delay or thermal lag
which must occur between the instant of occurrence of the 35 contact of a reference resistor 34; and an emitter terminal
42 which is coupled to a ground terminal through a source
overload condition and the blowing of the fuse, then the
of reference potential or Zener diode 45.
power transistor of a regulated transistorized power sup
If the operating characteristics of the fuse element are
ply will be adequately protected if a short develops in the
load circuit, but unfortunately, the fuse will blow and the
The two transistors ‘28 and 40, in combination with the
source of reference potential 45 and tapped reference re
circuit will become inoperative each time it is ?rst activated 40 sistor 34 regulate the negative potential fed to the load im
pedance 36 from the terminal 24.
The center tapped terminal 46 of the secondary winding
It is a primary object of this invention to provide a de
by the initially occurring large transient condition.
vice which can protect transistors from destruction due to
overloading.
14 is coupled to a ground terminal through a small im
pedance 43 which supports ‘a sliding contact 50. A control
It is another object of this invention to provide a tran 45 transistor 56, illustrated as a PNP type supports an emitter
terminal 54, ‘a base terminal 58, and a collector terminal
sistorized circuit breaker which can differentiate between
60. The sliding contact 50 is coupled through a diode 52
an overload state caused by a short in the load circuit and
to the emitter terminal 54. The base terminal 58 is con~
a transient state which occurs when the circuit being pro
nected to a ground terminal, and the collector terminal 60
tected is ?rst activated.
It is still another object of this invention to provide a 50 is coupled directly to the collector terminal 62 of a tran
sistor 64, designated as a PNP type, which also supports an
transistorized circuit breaker which is not self destructive,
emitter terminal 66 and a base terminal 68.
is economical to build, and is reliable in operation.
A transistor '70, designated as a PNP type supports a
Other objects and many of the attendant advantages of
base terminal 72, a collector terminal 74, and an emitter
this invention will be readily appreciated as the apparatus
becomes better understood by reference to the following 55 terminal 76. The base terminal 72 is coupled through
a resistor 73 to the collector terminal 62. The emitter
detailed description when considered in connection with
terminal 32 of the power transistor 28 is coupled to the
the accompanying drawings wherein:
collector terminal 62 through a resistor 80.
FIGS. 1 and 2 illustrate schematically two embodiments
The collector terminal 74 of transistor 70 is coupled
of a transistorized circuit breaker in accordance with the
through a resistor 82 to the base terminal 68, and to the
principles of this invention incorporated within a negative
terminal 24 through two resistors 84 and 86 connected
potential regulated transistorized power supply; and
in series. The junction terminal positioned between the
FIG. 3 is a schematic diagram of a positive potential
two resistors 84 and 86 is coupled to a ‘ground terminal
regulated transistorized power supply incorporating a tran
through a capacitor 88. A source of positive potential 90
sistorized circuit breaker in accordance with the principles
is coupled to the base terminal 72 through a resistor 92,
of this invention.
Similar reference characters refer to similar parts 65 and to the base terminal 68 through a resistor 94. :The
throughout the several views of the drawings.
emitter terminal '76 is coupled to the emitter terminal 96
Brie?y, in a regulated transistorized power supply, the
of a transistor 93 designated as a PNP type which also
current fed to a load impedance is metered by a current
sensitive means. The current sensitive means is precondi
supports a collector terminal 100 and a base terminal 102.
A source of positive potential 93 is coupled to feed a
tioned to change its state of conductivity abruptly when 70 signal directly to the emitter terminals 76 and 96, and
through an impedance 95 to the emitter terminal 66.
the current ?owing through the load impedance exceeds
3,051,852
3
4
The collector terminal 1% is connected to the base ter
and is fed to the base terminal 30 of transistor 28 to drive
minal 30 of transistor 28; and the base terminal 102 is
coupled to the base terminal 68 of transistor 64. The
base terminal 30 is coupled to the collector terminal 26
through two resistors 104 and 1% connected in series.
it to a non-conductive or cut off state.
-
The junction of the two resistors 104 and 1% is cou
pled to a ground terminal through a capacitor 1%.
In this manner
a short circuited load impedance is electrically isolated
from the regulated transistorized power supply, and the
power transistor 23 is protected from destruction which
would result from the passage of a large current.
The sliding contact 50 on the variable resistor 48 is
The base terminal 72 of transistor 70 is coupled to the
positioned to receive and feed a signal having a magnitude
terminal 24 through the series combination of a capacitor
suf?cient to activate the diode 52 and the transistor 56
110, a resistor 112, and a normally open switch 114. A 10 when the magnitude of the current which ?ows through
capacitor 116 connected between the terminal 24 and a
the resistor (and, therefore, the load impedance 36)
ground terminal. A relay
the primary winding 12 of
the operation of a pair of
positioned to deactivate the
exceeds a preselected value. The ohmic value of the
winding 118 coupled across
the transformer 19 controls
normally open contacts 120
transistor 28 by shorting the 15
collector terminal 26 to the emitter terminal 32.
' In the operation of the network disclosed in FIG. 1,
resistor is dependent upon the magnitude of the potential
required to activate the diode 52 and the transistor 56,
and also on the magnitude of the maximum allowable
current that can be drawn by the load impedance. Gen
erally, the resistor 118 will have a value in the order of
one ohm.
the transformer 10, the diodes 20, 22, and 45, the resistor
Thus, the potential drop across the resistor '48 will be
34, and the transistors 28, and 4t} cooperate to provide
a negative potential regulated transistorized power supply 20 very small and will not affect the output potential of the
regulated power supply. To insure rapid action of the
designed to maintain a constant value of voltage across
the load impedance 36.
current sensitive means the diode 52 and the transistor 56
should exhibit sharp turn-on characteristics. The diode
To protect the power transistor from an overload con
52 should be of the silicon type to present ‘forward oper
dition such as a short circuit in the load impedance, a
current sensitive means, and a switch means is provided. 25 ating characteristics which will be substantially independ
The current sensitive means meters the current that flows
ent of variations in temperature.
through the load impedance. The switch means, when
selectively activated by the current sensitive means dis
connects the regulated transistorized power supply from
perature adversely aifects the forward characteristics of
the load impedance.
‘An examination of FIG. 1 will indicate that resistor
If variations in tem
the transistor 56, then one or more diodes should be
coupled in series with the diode 52. In this manner,
variations in temperature will not affect adversely the for
ward characteristics of the transistor.
48, positioned between terminal 46 and a ground terminal,
is in series with the load impedance. Therefore, since all
The normally opened switch 114 coupled in series with
quickly and accurately determined at every instant by
merely measuring the potential drop present across the
resistor 48. The diode 52 and transistor 56 co-operates
ing and feeding a sharp spike pulse signal to the base
terminal 72 of transistor 70. Since only a sharp spike
pulse signal is utilized to reset the multivibrator, the reg
ulated transistorized power supply cannot be damaged
if the switch 114 is accidently closed, and held closed
before the defect in the load circuit has been corrected.
the resistor 112 and the capacitor 110 is used to manu
ally reset the bistable multivibrator after the short in the
the current which passes through the load impedance
must also pass through the resistor 48, the magnitude of 35 load circuit has been removed.
The reset means resets the multivibrator by generat
the current passed through the load impedance can be
with the sliding contact 5th on the resistor 48 to feed a
signal to the switch means when the potential which
appears across the resistor 48 (and therefore the current
In this invention, as the impedance of the load de
creases the magnitude of the load current increases.
exceeds a pedetermined safe limit.
45 When the current fed to the load impedance approaches
The transistor 56 and the diode 52 are cut off during
a predetermined maximum value the circuit breaker au
drawn from the regulated transistorized power supply)
normal operation of the regulated transistorized power
supply. However, if a short occurs in the load impedance
36 the current fed to the load impedance from the power
tomatically decouples the regulated transistorized power
supply from the load impedance before any of the com
ponents of the power supply can be destroyed by the
supply will increase. The current through, and the volt 50 large current drain. However, if the impedance of the
age across the resistor 4% will also increase.
When the
current through the load impedance exceeds a specified
value the voltage that appears between the sliding contact
50 and the ground terminal will increase to a value suf
ficient to permit the diode 52 and the transistor 56 to
become conductive and feed a signal from the collector
terminal 60 of transistor 56 to the collector terminal 62
of transistor 64. This signal activates the switch means
to decouple the power supply from the load impedance.
The switch means illustrated is a transistorized bistable
multivibrator formed by the transistors 64 and 70. Dur
ing normal operation of the regulated transistorized power
supply the transistor 6K1 is in a non-conductive state, and
load circuit was decreased suddenly to zero by the oc
currence of a short circuit, then it would be possible that
the collector voltage fed to the transistors might be re
duced substantially to prevent the proper operation of
the bistable multivibrator. To correct this condition the
external collector resistance has been divided into two
components represented by resistors 84 and 86. The ca
pacitor 88 couples the junction of these two resistors with
a ground terminal.
Now, since the potential across a
capacitor cannot be changed instantaneously the col
lector terminal of the transistor 70 will receive a poten~
tial adequate to insure its operation if a short circuit de
velops suddenly in the load circuit, and the multivibrator
the transistor 70 is in a conductive state. Generation of
will respond to sudden shorts which develop in the load
a signal on the collector terminal 66* of transistor S? 65 circuit to decouple immediately the load circuit from the
triggers the bistable multivibrator to ?ip the transistor 64
to a conductive state and the transistor 7% to a non
regulated transistorized power supply.
The resistor 80 can be coupled between the collector
conductive state. Transistor 98 is connected in parallel
terminal 62 of the transistor 64 and any one of several
with transistor 64. Therefore, when the transistor 64 is
other points in the circuit that exhibit negative potential
switched to a conductive state, the transistor 98 is also 70 having an amplitude su?icient to be utilized as the collec
switched to a conductive state.
tor supply potential. The removal of the collector sup
The magnitude of the potential present on the collector
ply potential from transistor 64} when a short circuit de
100 of transistor 93 approximates the magnitude of the
velops in the load circuit will not impede the operation
signal from the source of positive potential 93 when the
of the bistable multivibrator.
transistor 93 is in a fully conductive or saturated state, 75 The source of positive potential 93 fed to the emitter
3,051,852
5
terminals of the transistors 701 and 64 is necessary to in
sure the cut off of the power transistor 28 when the tran
sistor 98 is saturated.
Whenever the current fed to the load circuit exceeds
a preselected value the transistorized circuit breaker is
activated to decouple the regulated transistorized power
supply from the load circuit. In many instances a large
6
bypasses the transistor 28 by limiting the maximum cur
rent that can be drawn.
Naturally, the entire system should also be protected
by a fuse 128 coupled in series with the primary winding
12 of the transformer 10.
The position of the resistor 48 and the transisor 56
is not restricted to the position shown in FIG. 1, but can
be located anywhere in the circuit where the load current
surge current will be fed to the load circuit when the
?ows and the transistor collector junction can be biased
power supply is ?rst activated. This surge current, while
larger in magnitude than the preselected value selected to 10 properly.
With reference to FIG. 2, there is shown a negative
initiate operation of the circuit breaker, will not damage
power supply which utilizes an NPN transistor instead of
the power supply. However, the circuit breaker network
can only sense the magnitude of the current fed through
a PNP transistor in the current sensitive means. Since
FIG. 2 is identical to FIG. 1, except for the type and po
the load circuit, it cannot determine the cause of a large
current.
sition of the transistor which forms a portion ‘of the cur
This being so, the large surge current which can occur
rent sensitive means, only the current sensitive means will
each time the power supply is turned on will initiate ac
be referred to in detail. The emitter terminal 32 of tran
tivation of the circuit breaker network to decouple the
sistor 28 is coupled through a resistor 126 which sup
power supply from the load circuit. The resistors 84,
ports a sliding contact 128 to the base terminal 138 of
and 86, and the capacitor 88 corrects this situation by 20 an NPN transistor 13%, and then to the resistor 34, and
maintaining the transistor 70 in an inactive state until
load impedance 36. The emitter terminal 132 of the
the regulated transistorized power supply reaches its
transistor 136 is coupled to the sliding contact 128
steady state operating conditions. The capacitor 88 re
through a diode 136; and the collector terminal 134 is
quires a certain duration of time to become charged
coupled to the base terminal 63 of transistor 64. The
through the resistor 36. Therefore, the bistable multi~ 25 operation of the structure of FIG. 2 is the same as the
vibrator is not activated when the power supply is ?rst
operation of the structure of FIG. 1 described previously.
activated, but remains in a cut off state until the capaci
With reference to FIG. 3, there is illustrated a circuit
tor 38 is charged to a certain potential. The time re
breaker for utilization with a regulated transistorized
quired ‘for the capacitor 88 to receive the desired change
power supply which furnishes an output signal having a
is adjusted to be slightly longer than the time required
for the power supply to reach its steady state operating
condition.
However, another special situation is created if the
positive potential. The slight diiferences apparent in the
arrangement of the components of the regulated transis
torized power supply of FIG. 3 over the arrangement of
the components of the regulated transistorized power sup
plies of FIGS. 1 and 2 is necessary due to the vfact that
bistable multivibrator is in a deactivated state when the
power supply is ?rst turned on. For example, if a short 35 the power supply of FIG. 3 delivers a positive potential
is present in the load circuit before the power supply is
at its output terminals while the power supplies of FIGS.
energized, then when the regulated transistorized power
1 and 2 deliver negative potentials at their output termi
supply is energized it will be damaged by the large cur
nals. In this embodiment, the resistor 86 and capacitor
rent it is required to pass during that interval of time be
88 is eliminated, the upper terminals of the resistors 84
tween the activation of the regulated transistorized power 40 and 8d are coupled to a ground terminal, and the current
supply and the activation of the bistable multivibrator.
sensitive means is interposed between the transistor 28
This special situation can be corrected by coupling a
and the load impedance 36. The collector terminal 26
pair of normally closed relay contact points 120 between
of transistor 23 is coupled through the resistor 48 to the
the collector terminal 26 and the emitter terminal 32 of
load impedance 36 and to the base terminal 58 of tran
the transistor 28, and by coupling the winding of the 45 sistor 56. It should also be noted that transistor 40 of
relay across the primary winding 12 of the transformer
the PNP type has been replaced with ‘a transistor 41 desig
10. In operation, the operating time delay of the relay
prevents the relay contacts 120 from opening for a few
nated as the NPN type and connected as shown. In this
embodiment the magnitude of the source of positive po
milliseconds immediately after the regulated transistor
tential 93 must be greater than the magnitude of the
ized power supply is ?rst activated. This time interval 50 source of positive potential 9%. The sliding contact 50
is su?‘lcient to protect the transistor 28 by providing a
of the resistor 48 is coupled through the diode 52 to the
very low resistance path around the transistor 28 until
emitter terminal 54 of the transistor 56; and the collector
the capacitor 88 charges to a desired value to permit the
terminal 60 of the transistor 56 is coupled to the collector
transistor 70 to become activated.
terminal 62 of transistor 64.
Occasionally, a surge current condition will be cre 55
The slight variations in the arrangement of the com
ponents of the circuit breaker and the regulated tran~
ated when the regulated transistorized power supply is
sistorized power supply illustrated in FIG. 3 over that
?rst energized. The surge current, when sensed by the
illustrated in FIG. 1 exists because the embodiment of
resistor 48 will appear as an overload condition and de
FIG. 3 supplies a positive potential while the embodiment
A second set of normally closed relay contacts 124 ac 60 of FIG. 1 supplies a negative potential. However, in
operation, the structure of FIG. 3 performs in a manner
tivated by the relay winding 118 are connected across
similar to the operation of the structure of FIG. 1 de
the resistor 48. These contacts provide a short circuit
scribed previously in detail.
path across the resistor 48 to prevent the generation of
'With reference to FIGS. 1, 2, and 3, if the switch net—
a trigger potential by the surge current. In this manner
65 work or means is altered by substituting a monostable
the surge current cannot trigger the multivibrator which,
multivibrator for the bistable multivibrator, then the
in turn, would decouple the power supply from the load.
reset network can be eliminated. In this embodiment, it
couple the power supply from the load.
Thus, the trigger potential used to change the state of
a short circuit occurs in the load impedance the mono
the multivibrator is eliminated temporarily. The charac
stable multivibrator will ?ip from its stable state to its
teristics of the relay selected determine the time delay 70 quasi-stable state, and decouple the load impedance from
between the energization of the power supply and the
the power supply. After a short interval of time the
opening of the two sets of contacts 120 and 124 to allow
multivibrator will automatically reset itself by ?opping
the power supply to operate normally. A small resistor
back to its stable state, ‘and again couple the load im
126 should be added in series with the relay contacts 120
pedance to the power supply. It the short circuit is still
to protect the recti?er diodes when the ?ow of current 75 present, the current through the load impedance will in
3,051,852
crease rapidly and the multivibrator will again flip to its
quasi-stable state and again decouple the load impedance
lated voltage from a power transistor to a load impedance,
a transistorized circuit breaker comprising shorting means
from the power supply.
coupled to short the power transistor for a preselected
Thus, as long as the load is short circuited the multi
interval of time when the transistorized power supply is
vibrator will continue to oscillate, and alternately couple 5 ?rst activated, a resistor coupled to meter the current
and decouple the load impedance to and from the power
fed to the load impedance, a ?rst transistor coupled to
supply to limit the average power dissipated in the power
change its state of conductivity when the current through
transistor to a safe value.
the resistor exceeds a preselected value, a diode inter~
Obviously, many modi?cations and variation of the
posed between said resistor and said ?rst transistor, second
present invention are possible in the light of the above 10 and third transistors coupled together to form a multi
teachings. ‘It is therefore to be understood that within
vibrator coupled to said transistorized power supply and
the scope of the appended claims the invention may be
fed by said ?rst transistor to decouple said transistorized
practiced otherwise than as speci?cally described.
power supply from said load impedance when the metered
What is claimed is:
current exceeds a preselected value, and a resistor-ca
1. In a transistorized power supply which feeds regu
pacitor reset network coupled to said multivibrator.
lated voltage to a load impedance, a transistorized circuit
6. In a transistorized power supply which feeds regu
breaker comprising a resistor coupled to meter the cur
lated voltage from a power transistor to a load impedance,
rent fed to the load impedance, a ?rst transistor coupled
a transistorized circuit breaker comprising ?rst shorting
to change its state of conductivity when the current
means coupled to short the power transistor for a pre~
through the resistor exceeds a preselected value, a diode 20 selected interval of time when the transistorized power
interposed between said resistor and said ?rst transistor,
supply is ?rst activated, a resistor coupled to meter the
second and third transistors coupled together to form a
current fed to the load impedance, a ?rst transistor
multivibrator coupled to said transistorized power supply
coupled to change its state of conductivity when the cur
and fed by said ?rst transistor to decouple said transis
rent through the resistor exceeds a preselected value, a
torized power supply from said load impedance when 25 diode interposed between said resistor and said ?rst tran
the metered current exceeds a preselected value, and a
resistor-capacitor reset network coupled to said multivi
sistor, a second shorting means coupled to short said re
sistor for a preselected interval of time when the tran
brator.
sistorized power supply is ?rst activated, a bistable multi
'2. In a transistorized power supply which feeds regu
vibrator coupled to said transistorized power supply and
lated voltage to a load impedance, a transistorized circuit 30 fed by said ?rst transistor to decouple said transistorized
breaker comprising a resistor coupled to meter the cur
power supply from said load impedance when the metered
rent fed to the load impedance, a transistor coupled to
current exceeds a preselected value, and reset means
change its state of conductivity when the current through
coupled to said bistable multivibrator.
the resistor exceeds a preselected value, a diode inter
7. In a transistorized power supply which feeds regu
posed between said resistor and said transistor, shorting 35 lated voltage from a power transistor to a load impedance,
means coupled to short said resistor for a preselected in
a transistorized circuit breaker comprising ?rst shorting
terval of time when the transistorized power supply is
means coupled to short the power transistor for a pre
?rst activated, a bistable multivibrator coupled to said
selected interval of time when the transistorized power
transistorized power supply and fed by said transistor to
supply is ?rst activated, a resistor coupled to meter the
decouple said transistorized power supply from said load 40 current fed to the load impedance, a ?rst transistor
impedance when the metered current exceeds a pre
coupled to change its state of conductivity when the cur
selected value, and ‘reset means coupled to said bistable
rent through the resistor exceeds a preselected value, a
multivibrator.
diode interposed between said resistor and said ?rst tran
3. In a transistorized power supply which feeds regu
sistor, second shorting means coupled to short said re
lated voltage to a load impedance, a transistorized circuit 45 sistor for a preselected interval of time when the tran
breaker comprising a resistor coupled to meter the cur
sistorized power supply is ?rst activated, a second and
rent fed to the load impedance, a ?rst transistor coupled
third transistors coupled together to form a multivibrator
to change its state of conductivity when the current
coupled to said transistorized power supply and fed by said
through the resistor exceeds a preselected value, a diode
?rst transistor to decouple said transistorized power supply
interposed between said resistor and said ?rst transistor, 50 from said load impedance when the metered current ex
shorting means coupled to short said resistor for a pre
ceeds a preselected value, and a resistor-capacitor reset
selected interval of time when the transistorized power
network coupled to said multivibrator.
supply is ?rst activated, second and third transistors
8. :In a transistorized power supply which feeds regu
coupled together to form a multivibrator coupled to said
lated voltage from a power transistor to a load impedance,
transistorized power supply and fed by said ?rst transistor
a circuit breaker comprising a resistor coupled to meter
to decouple said transistorized power supply from said
the current fed to the load impedance, a ?rst transistor
load impedance when the metered current exceeds a pre
coupled to change its state of conductivity when the
selected value, and a resistor-capacitor reset network
current through the resistor exceeds a preselected value,
coupled to said multivibrator.
a diode interposed between said resistor and said ?rst
4. In a transisorized power supply which feeds regu
transistor, a ?rst set of normally closed relay contacts
lated voltage from a power transistor to a load impedance,
coupled to short said power transistor, a second set of
a transistorized circuit breaker comprising shorting means
normally closed relay contacts coupled to short said
coupled to short the power transistor for a preselected
resistor, a relay winding energized when the transistorized
interval of time when the transistorized power supply is
power supply is energized coupled to open said ?rst and
?rst activated, a resistor coupled to meter the current 65 second sets of normally closed relay contacts after a pre
fed to the load impedance, a transistor coupled to change
determined time delay, a bistable multivibrator coupled to
its state of conductivity when the current through the re
said transistorized power supply and fed by said ?rst
sistor exceeds a preselected value, a diode interposed be
transistor to decouple said transistorized power supply
tween said resistor and said transistor, a bistable multi
from said load impedance when the metered current ex
vibrator coupled to said transistorized power supply and
ceeds a preselected value, and reset means coupled to
fed by said transistor to decouple said transistorized power
said bistable multivibrator.
supply from said load impedance when the metered
9. In a transistorized power supply which feeds regu
current exceeds a preselected value, and reset means
lated voltage from a power transistor to a load impedance,
coupled to said bistable multivibrator.
a circuit breaker comprising a resistor coupled to meter
5. In a transistorized power supply which feeds regu 75 the current fed to the load impedance, a ?rst transistor
3,051,852
10
coupled to change its state of conductivity when the cur
rent through the resistor exceeds a preselected value, a
diode interposed between said resistor and said ?rst tran
sistor, a ?rst set of normally closed relay contacts coupled
to short said power transistor, a second set of normally
closed relay contacts coupled to short said resistor, a
is changed by the passage of a current through said im
pedance element exceeding said preselected value.
11. A power supply for a. load, comprising, a power
transistor connected to said load, an impedance element
connected in series with said power transistor for pro
ducing a voltage drop ‘across said impedance element in
accordance with the current through said power transis
tor, a control transistor coupled to said impedance ele
supply is energized and coupled to open said ?rst and
ment to change its state of conductivity when the current
second sets of normally closed relay contacts after a pre
determined time delay, second and third transistors cou 10 through said impedance element exceeds a preselected
value, a multivibrator coupled to said control transistor
pled together to form a multivibrator coupled to said
and adapted when actuated to decouple said power tran
transistorized power supply and fed by said ?rst transistor
sistor from said load, means for actuating said multivibra
to decouple said transistorized power supply from said
tor when the conductivity of said control transistor is
load impedance when the metered current exceeds a pre
selected value, and a resistor-capacitor reset network cou 15 changed by the passage of a current through said im—
pedance element exceeding said preselected value, a re
pled to said multivibrator.
sistor-capacitor network for generating a reset pulse,
10. A power supply for a load, comprising, a power
and means for applying said reset pulse to said multivibra
transistor connected to said load, an impedance element
tor to recouple said power transistor to said load.
connected in series with said power transistor for produc
ing a voltage ‘drop across said impedance element in 20
References Cited in the ?le of this patent
accordance with the current through said power transis
UNITED STATES PATENTS
tor, a control transistor coupled to said impedance ele
relay winding energized when the transistorized power
ment to change its state of conductivity when the cur
rent through said impedance element exceeds a preselected
value, a multivibrator coupled to said control transistor 25
and adapted when actuated to decouple said power tran
sistor from said load, and means for actuating said mul
tivibrator when the conductivity of said control transistor
2,776,382
Jensen _______________ __ Jan. 1, 1957
2,832,900
2,969,498
Ford _______________ __ Apr. 29, 1958
Stenudd _____________ __ Jan. 24, 1961
OTHER REFERENCES
Publication: “Transistor Power Supply,” Electronics,
June 20, 1958.
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