Патент USA US3076140код для вставки
i Jan. 29, 1963 R. P. FARNswoRTH ETAL POWER SUPPLY CIRCUIT Filed Sept. 29, 1958 „EnNM 3,076,135 ice 3,dlli,l35 ¿Datenteel dan. 29, lgâêi 9 ad independent of temperature and ageing of the amplifying 3,tl76,i35 Rohert i’. Farnsworth, Los Angeles, and Leonard Azar, elements in the circuit. It is a still further object of this invention to provide a PGV/lili Sillery? Cil-mill? fast acting power supply utilizing transistors which will #Culver City, tïalil‘., assignors to Hughes Aircraft Corn not only completely disconnect the source from the load during an overload condition when operating at full rated power but will return to supplying full rated power upon removal of the overload condition. This invention relates to power supplies and partic Another object of this invention is to provide a tran ularly to a direct-current power supply utilizing a fast 10 sistor power supply having a simplified overload protec acting overload protection circuit. tion circuit for protecting both the power supply and the supplied circuitry, and which operates to disconnect the ln the prior art, DC. (direct current) power supplies power supply at a predetermined rated current independent were used in connection with vacuum tubes and delivered relatively high output voltages and could operate with of changes of characteristics of the transistor due to age pany, GCulver City, Cali, a corporation ot‘ Delaware Filed Sept. 2.9, 1953, der. No. 765,693 1l Claims. (Qi. 323-22) relatively high output impedances. However, with tran sistor circuitry, power supplies may be required to supply relatively low output voltages while supplying current of 15 ing and temperature. The output impedance of the power According to one feature of this invention, a power supply receives unregulated direct current voltage from a transformer and rectifier arrangement, and supplies it to supply may be required to be less than l0"3 ohms. These a load through a series connected regulating, or control, 25 amperes or more. problems have been solved by utilizing power supplies 20 transistor which varies in static impedance in response to with high power transistors for regulation and low for ward resistance diodes for rectiiication. “ìhe low output impedance from these power supplies changes of its base current. A voltage comparator in~ cluding a i'lrst diilerential anipliñer and a voltage divider both connected across the load, is utilized to control a current signal in response to changes in the load voltage that of protecting the power supply and the load against 25 or potential diiierence. A second differential ampliñer has created new problems, the most formidable one being short-circuits or accidental overloads. During a short circuit or accidental overload condition, destruction of. the transistors and rectiiiers of the power supply as well as is connected to the base of the control transistor and is connected to the lirst differential amplifier for responding to the changes of the current signal to maintain the con stant load voltage. An overload control circuit is pro destruction of the transistor circuitry being supplied with power occurs at a fast rate. The time required for de 30 vided including a resistor connected from a terminal of the control transistor and in series with the load to form struction may be in the order of 100 microseconds under a ñrst voltage divider and including a second voltage severe conditions. Conventional fuses or mechanical dis divider connected from the same terminal of the control connections require 2G to 30 milliseconds to open, which transistor to the other side oi the load. A signal~forming operation is far too slow to protect transistors. Some elec tronic disconnect circuitry of the prior art samples signal 35 transistor is connected between the ñrst and the second voltage dividers so as to respond to a predetermined current in a regulator loop and provide turmoil of the sup polarity of potential dilierence indicating maximum rated ply when the signal current reaches a preset value. The load. The signal forming transistor is connected to shunt out the current from the tirst differential amplilier in stages of the supply, which gain is dependent upon ageing 40 response to the predetermined polarity which in turn biases the regulating transistor out of conduction to etîec and temperature oi the circuit elements, as well as upon tively disconnect the source from the load. A leakage supply voltages. Thus, the turn-oft current is variable .shortcoming of this system is that the signal current is related to the load current by the gain of one or more path across the control transistor maintains this discon nected condition by supplying a small current through the 45 first and second voltage dividers. When the overload con load current. dition is removed the potential difference between the Also, some conventional power supplies having auto lirst and second voltage dividers returns to a polarity to matic turn-oit characteristics follow a turn-oit path which bias the signal-forming transistor out oi conduction, thus a though allowing them to turn on under full load añter allowing the voltage comparator circuit to continue its removal of a short circuit condition, will also allow them regulating operation at any load up to maximum load. to exceed maximum dissipations under partial short cir The novel features of this invention, as well as the cuit. Other conventional power supplies follow a path invention itself, both as to its organization and method of which allows them to turn completely off when an over operation, will best be understood from the accompanying load condition occurs under full load but requires partial and changes under these conditions so as to not consis tently disconnect the power supply at a ñxed maximum removal of the full load to turn on after the overload or 55 description, taken in connection with the accompanying drawings, in which: short circuit condition has been corrected. rîhese turn on and turn-od characteristics may result from the non linearities of the system components. A system which would provide tast operating overload protection, that PIG. l is a schematic diagram of the power supply circuit of this invention; and FlG. 2 is a graph to illustrate the operation of the circuit of FIG. l. would provide overload protection at a fixed maximum 60 Referring iirst to FIG. l, a schematic circuit diagram load current independent oi the gain of the circuit ele is shown of the power supply circuit including the over ments, and which would turn both completely oli and load protection arrangement of this invention. The power completely on when a short circuit condition occurs and supply of this invention receives unregulated voltage, is removed at full load, would have wide use, especially which may be -32 volts, from an unregulated voltage with transistor circuitry. lt is, therefore, an object of this invention to provide a power supply which rapidly disconnects from its load upon the occurrence ot a short circuit or an overload condition. it is a further object of this invention to provide a transistor power supply which turns ott under an overload condition and turns on upon removal of the overload condition at a consistent maximum load current value, 65 source 2@ comprising a transformer and alternating cur rent voltage source 22 connected to a terminal 2S which may be at ground potential and a rectitler 2d connected to the transformer and voltage source 22. rihe unregulat ed voltage source Ztl supplies power through a regulating transistor 26 of a regulating element circuit 32. to a load 34, which may include a resistor RL, and is connected to the terminal 25 through a ground lead lith. The regu 3,076,135 3 4 lating element circuit 32 also includes a driver transistor 128 which is connected to the lead 84 and has a collector 130 which is connected to the lead 9@ at a junction 132. Thus, it can be seen that current passes into the junction 132 either from the transistor 12t- or from the transistor 64 of the current amplifier circuit 66. The lead 103 is also connected to the base ‘le of the regulating transistor 26 by'way of a biasing resistor 136 which acts to pass leakage current from the base 44 to maintain the regulat 38. The regulating transistor 26 which may be of the PNP type has a base 46, an emitter 42 and a collector 4t), and the driver transistor 318 which may be of the NPN type has a base Sti, an emitter 4S, and a collector 46. The collector ‘ttl of the regulating transistor 26 is con nected to the rectifier 24 and the base de of the regulating transistor 26 is connected to the collector ¿i6 of the driver transistor 33. The emitter d8 of the driver transistor 33 ing transistor 26 biased when in its nonconducting state, is connected to the collector ¿itl of the regulating transistor 10 as will be explained subsequently. 26 to provide a return path for current from the base 44 The voltage comparator circuit 96 includes transistors of the regulating transistor 26, as will be explained sub 138 and 146y arranged as a second differential amplifier sequently. A leakage resistor 54 is connected between the circuit. The transistors 1355 and 146 may be of the PNP collector d@ and the emitter ¿t2 of the regulating transistor type. The transistor 138 has a base 14€), an emitter 162, 26 and, as will be explained hereinafter, passes a current to maintain the circuit disconnected during an overload and a collector 144, and the transistor 166 has a base condition. The base 56 of the driver transistor 38 is connected to a current-amplifier circuit 6d which utilizes a differen tial amplifier ior controlling the current passed into the 20 base Sil of the driver transistor 38. The diiferential amplifier includes a transistor 64 and a transistor 66 both of which may be of the PNP type. The transistor 64 has a base 66, an emitter 7d, and a collector 72, and the transistor 66 has a base 74, an emitter 76, and a collector 25 '76. The collector 72 of the transistor 64 is connected to the base 5t! of the transistor 36 and the collector 7S of the transistor 66 is connected to the collector 46 of the regulating transistor 26. A biasing resistor Si) is con nected between the collector ’72 of the transistor 64 and 30 the collector 78 of the transistor 66 to provide a leakage current path from the base Sil of the transistor 38 when the transistor 38 is biased out of conduction, as will be explained subsequently. The emitters 70 and 76 of the transistors 64 and 66 are connected by way of a current limiting resistor 32 to a lead 84. The lead 3d is con ected to a terminal 88 which may be connected to a -|-l5 voltage unregulated source (not shown), which provides "î a bias for maintaining operation of the circuit during an overload condition. The base 68 of the transistor 64 is connected to a lead 99 and the base ’74 of the transistor 66 is connected to a lead 92 through which leads, control current passes, as will be explained subsequently. Thus, the current ampliiier circuit 66 is connected for control ling the regulating element circuit 32. The current ampliñer circuit 6i) is controlled by an 146, and emitter 156, and a collector 152. The collector 144 of the transistor 138 is connected to the lead 162 by way of a biasing resistor 156 and the collector 152 of the transistor 146 is connected to the lead 102 by way of a biasing resistor 158. The emitters 142 and 150 of the transistors 138 and 146 are connected to ground lead 108 by way of a current limiting resistor 159. The base 148 of the transistor 146 is connected to a lead 162 by way of an impedance-matching resistor 16d. The lead 162 is connected to the ground lead 106 by way of a resistor 166 and is connected to the cathode of a diode 168, which may be a Zener type diode. The anode of the diode 168 is connected to the lead 102 to provide a potential to the base 14S of the transistor 146 which follows the variation ot' the load potential on the lead 102. It is to be noted that the resistor 164 is utilized to match the impedance out of the base 14S of the transistor 146 to the impedance out of the base 1d@ of the transistor 136. The base 146 of the transistor 13S is connected by a variable tap 172 to a resistor 174, one end of which is connected to the lead 102 by way of a resistor 176 and the other end of which is connected to ground lead 168 by way of a resistor 178. The resistors 174, 176, and 178 thus are a voltage divider of the potential diñerence -acrossthe load 34 for dividing out a potential to control the conduction of the transistor 138. The collector 144 of the transistor 138 is connected to the lead 92 which, ` in turn controls the conduction of the transistor 66, as will be explained subsequently. The collector 152 of they transistor 146 is connected to a lead 182 which, in turn is connected to the junction 132 for receiivng current overload control circuit 94 and a voltage comparator from either the transistor 64 during normal regulation circuit 96. The overload control circuit 94 includes a or from the transistor 124 during an overload condition, resistor R1 having one end connected to a junction 100 as will also be explained subsequently. A capacitor 180 which, in turn, is connected to the emitter d2 of the regu 50 is coupled across the leads 102 and 166 to stabilize the lating transistor 26. The other end of the resistor R1 circuit for providing a low output impedance to signals is connected through a lead 162 to the resistor RL of the , on the lead 102 at a frequency above the frequency re load 34. The load current lL is indicated by an arrow sponse of the transistors. in the circuit, as is well known 101. The resistor R1 in combination with the resistor RL in the art. of the load 313i provides a first voltage divider, as will be 55 The operation of the voltage regulator of this inven explained subsequently. The junction 100 is also con tion includes both normal voltage regulation of the load nected through a lead 103 to a resistor R2 which in turn voltage on the lead 102 to maintain a regulated voltage is connected to one end of a resistor R3 by Way of a lead and overload protection during operation when, for ex 166. r[he other end of the resistor R3 is connected to ample, a fault such as a short circuit of the load 34 occurs. 60 the ground lead 168. The lead 102 is connected to the During normal regulation, the regulating circuit controls cathode of a diode 112 which has its anode connected to the current through the series element which is the tran one end of a resistor 114 by lead 116. The other end of sistor» 26, to correct variations of the regulated potential the resistor 114 is connected to the lead 84. on the lead 102 caused either by voltage fluctuations A signal transistor 117 which may be of the NPN type of the source 2t) or by small variations of the effective has a base 118, an emitter 126, and a collector 122 with 65 resistance of the load 3.4. A rise of potential on the the base 118 connected to the lead 116 and the emitter collector 40 from a positive-goingfluctuation of the un 126 connected to the lead 106. As will be explained subsequently, the difference in potential drop across the regulated potential from source 26` decreases the emitter torcollector potential of the regulating transistor 26 and resistor R1 and the diode, 112 and across the Aresistor R2, atgthe value of> the current determined by the potential which potential difference appears betweenthe leads 116 70 on the b-ase 44, results in a small decrease in collector and 166, determines whether transistor 117 is biased into current. This decrease oi collector current is accom conduction. rlîhe collector 122 of the transistor 117 is panied by a decrease of the current passing through load connected to the base 126 of a transistor 124. which may RL, which results in a rise in potential on the lead 102. be of the PNP type. I The transistor 124 has an emitter 75 This rise in potential is sensed by thev voltage comparator 3,076,135 5 circuit 96 and, as will be described, >acts to lower the po tential on base liti. This condition decreases the static impedance of the transistor 23.6 to slightly increase the load current so as to increase the potential drop across the resistor RL and to restore the regulated potential on the lead 162. A decrease of the effective value of the resistor RL the potential on the lead luz is regulated to -25 volts by the action of a servo loop including a voltage corn parator 96 and the path to the ‘oase ¿la of the regulating transistor 2o. An increase of potential on the lead le?. resulting from a Voltage variation ot the source 2d or a srnall decrease in the value of the load 3ft impedance, as discussed, impresses the increase of potential through the constant voltage Zener diode lod to develop across also causes an increase of potential on the lead i162. lt the resistor lío for application to the 'oase 14S of the is to be noted that this condition causes only a small in crease of collector current of the regulating transistor Z6 10 transistor lido, as a potential increase substantially similar in amplitude to the increase on the lead li’lZ. The as determine by the potential on the base da. The increase transistor 146 is thus biased so as to decrease its con of potential on the lead Teil2 is sensed by the voltage duction and this decreased current iiow through the re comparator circuit 9o and, as will be described, acts to sistor 153 results in a decrease of the potential on the lower the potential on the base ¿i4 of the regulating collector lSZ, which decrease is impressed on the base transistor 26 so as to decrease the static impedance of 65 of the transistor 64 to increase its conduction. At the transistor 26 and to increase the current from emitter the same time, a small increase of potential is impressed 42 to collector ¿tu a required amount. rthis increase of on the base lati of the transistor 13S from the tap 172. collector current increases the current passing through the However, because of the large decrease or" current through load RL and causes a fall in potential on the lead lilZ, the transistor ldd and through the resistor läd, the cur thus restoring the regulated potential on the lead lûZ. rent passing through the transistor 133 is increased. This The operation of the voltage comparator' circuit 96 increase of current results from the diiierential action and the current amplifier circuit oli during norrnal voltage of a constant current passing through the current limiting regulation will now be described. During normal voltage resistor l59. Thus, there is an increase of potential on regulation, the transistor il? is biased out of conduction to interrupt the current path through the transistor 124 25 the collector lll-4i- of the transistor 13S which is impressed on the ’oase 711i of the transistor do to bias it further out to the junction 132. Thus, the potential developed on of conduction. As a result of this action, the potential the collector 152 of the transistor 146 from current pass~ ing through the transistor ldd and the resistor 158 is impressed through the lead lil?! to the base ed to control conduction »of the transistor ed. An increase (positive going) of potential at the base ldd oi the transistor M6 on the collector '.72 of the transistor ed is increased be cause of the decrease of potential on the base eff; to bias the transistor 38 into further conduction and to decrease the potential on the base or" the transistor' 26. in response to t‘ne decrease of potential on the base from the lead lo?. results in a decrease of potential on 4d, the static impedance of the transistor 25 is decreased the collector 152 of the transistor ido. This decrease (negative-going) of potential is impressed on the base 68 35 and increased current passes through the load RL to decrease the potential on the lead so as to correct to increase the conduction of the transistor 64, and to in the original rise in potentie. lt is to be noted that crease the potential on the base Sil of the transistor Tail. this operation is continuous. Also, a potential decrease The transistor 33 is thus biased into further conduction on the lead lo?. is corrected in a similar but opposite and the potential on the hase of the transistor 26 is manner. decreased to increase the ernitter to collector current New that the norrnal regulating action of the power through the transistor 26. The potential impressed on the base ldd ot the tran sistor i353 is also determined by the load potential on the lead im, which potential acts to Vary the current passed from the emitter i142 to the collector ldd of the transistor T138. An increase of potential on the base lé-iâ results in an increase of potential on the collector les? of the transistor i3d because of the differential ampliiier action, as will be described, which potential is impressed supply has been explained, the action of the overload control circuit 9d resulting from an overload condition such as a short circuit of the load 34, will be describe . rthe ratio oi the value of resistor R1 to that of the re sistor RL of the load to the ratio oí the value of re sistor R2 to that of the resistor R3 is the relation which determines the condition when an overload condition, such as a short circuit, or" the load 3d is present. it is to ‘oe noted that a short circuit of the load 34 results on the base 74 of the transistor od to decrease its con 50 in the resistance RL being effectively reduced in value duction. rlfhus, the potentials on the collectors ltd-4l» and i152 are impressed through the leads 92 and i182 to the bases 7d and 68 oiî the transistors 6d and ed. The differential amplifier arrangement is utilized so that changes of gain characteristics of the transistors ed, 55 66, i3d and lele have a very sinall eiiect on the regulat and a current il, larger than rated current being sup plied. The transistor fir? is biased out of conduction during the normal regulating action when the voltage drop across the resistor R1 is less than the voltage drop across the resistor However, when the voltage drop across the resistor R1 is greater than the voltage drop ing action. A. substantially constant current passes across the resistor R2, resulting from a niaximurn load through the current limiting resistor ‘£59 and through current passing through the resistor R1 and the junc the parallel resistors iSv-i and ldd. Thus, changes of tion lilo, the transistor ll‘î is biased into conduction. the gain characteristics due to ageing or temperature 60 Under these conditions, the ratio of R1 to RL is greater changes, for example, of the transistors i3d and M6 has than the ratio of R2 to R3 indicating a decrease of the a relatively small eiiect on the difference in potential on eiiective value ot the load resistor R . the collectors las and 152. The difference in potential effective load resistance lìmmm) is equal to on the leads 92 and ld?. is the value which controls the amount of conduction of the transistors 66 and ed and, 65 in turn, the impedance oi the regulating transistor Zd. The current-limiting resistor d2 passing a constant cur rent into the transistors 64 and ed of the iirst difierential The minimum R2 Titus, tl e maximum current if (mx) which is equal to ampliíier circuit, cancels changes oi gain characteristics of the transistors 6d and on in a similar manner. rl`hus, 70 RL(mln) the differential amplilier arrangements of transistors i353, may be expressed as follows: 145, 64 and do is utilized to provide reliable regulation independent of temperature changes or ageing of the -TL( mtlX >=MEOR2 RIRS transistors, for example. During the regulating operation of the power supply, 75 where E9 is equal to the potential on the lead 152 which 3,078,135, 7, is the regulated voltage for determining the maximum load current at which the overload control circuit 9d becomes operative. When the load current IL increases above the maximum rated value so that the voltage drop across the resistor R1 is greater than the voltage drop across R2, the transistor 117’ is biased into full con duction. Thus, the transistor 124 is biased into conduc tion, passing current from the emitter 12S to the coi lector 13@ and into the junction 132 and to the lead 132. The positive potential from the lead 34 is im pressed through the transistor 124i- and upon the base d8 of the transistor de to bias it out of conduction. When the transistor 64 is biased out of conduction, the driver transistor 3S is biased out of conduction and, in turn, the regulating transistor 26 is biased out of con duction to develop a high impedance to flow of load current IL. Thus, the source 20 is effectively discon nected from the load 34 under this overload condition. The foregoing overload condition with the transistor 8 rent of l ampere to a grounded load from a -32 volt unregulated source: Transistor Transistor Transistor Transistor 2d, Delco (GM) _____________ __ 3S, Sylvania _________________ ..„ de, General Electric ___________ __ de, General Electric ___________ __. Transistor lli?, Transistor 121i, Transistor i3d, Transisto-r'ildá, General Electric _________ __ 4jD4A5 Philco __________________ __ T 1275 Hughes _________________ __ HA-7550 Hughes _________________ _- IHA-7550 Terminal d8 ____________________ „volts“ Resistor ____________________ „ohms“ Resistor dit _____________________ __do____ Resistor 82 --------------------- „d0“-` Resistor i312» ____________________ __do_..__. Resistor R1 _____________________ „do_„„_ Resistor Resistor Resistor 3.1"/ biased in a conductive state is maintained by a small 20 Resistor R2 _____________________ __do„_„_ R3 _____________________ „_do__-„ Rmmm) _________________ „_do____ il@ ____________________ __do_-__ current flow through the leakage resistor 5ft or by a small Resistor 156 ____________________ .__d0_„__ leakage current through the transistor 2d. it is to be Resistor 153 ____________________ __do___.. noted that when the transistor Zd is of a type with a small Resistor 159 ____________________ _-do_.._.. leakage current, the leakage resistor 5d is not required. „Resistor 16t- ____________________ __do____ This leakage current passes from the resistor RL through Resistor lied ____________________ __do-..__ the resistor R1 as well as through the resistors R3 and R2 Resistor 174 ____________________ __do____ to the junction litt) to maintain a potential ditterence from Resistor 176 ____________________ __do____ the base 118 to the emitter i2@ of the signal transistor Resistor 17S ____________________ __do__.._ li?. The potential drop across the resistor R2 is greater Capacitor ld@ ____________ __microfarads__ than the drop across the resistor R2 because of their- 30 Diode i12, Hughes _____________________ __ relative values. The base lid of the transistor 1l? is .Diode 168, Hoffman ___________________ _.- biased by current passing from the +15 volt unregulated source at the terminal 88 through the resistor i114, through 2N173 2Nl42 2N123 2N123 +15 2,000 10o 10,000 l0 2 909 11,300 25 39,009 5,110 5,110 8,060 560 1,690 200 75() 1,580 350 6,007 iN 430A lt is to be noted that although the power supply has been described as supplying negative potentials relative to the diode M2 and through the leakage resistor 5d. It is to be noted that current through the resistor 1M acts 35 ground potential, it may be easily arranged to supply posi tive potential relative to ground potential by reversing all to maintain the diode H2 forward biased during both voltages and changing the transistor types. normal regulation and an overload condition. Also, the Referring now to FIG. 2, which is a graph of load transistor i24- is biased into conduction during an over load condition by the +15 volt potential from the termi nal 3S to apply the biasing potential to the junction £32 and the base 68 of the transistor Thus, the +15 volt terminal dit is required to maintain the transistors potential versus load current, as well as referring to FiG. l, the operation of the voltage regulator will be explained in further detail. The constant regulator dissipation line 184i is shown to indicate the power capabilities of the regulating transistor 26. The regulated potential is shown T17 and 124 biased in conduction during an overload condition. as -25 volts, and the maximum load current is shown The transistor lll'í and the diode i12 are of similar type 45 as 1 ampere which is equal to materials, so that an increase in impedance characteristics EuRz of the diode 112 and the transistor lill’î from temperature RlRa changes, for example, is similar. Thus, an increase of impedance characteristics resulting in an increased po Thus, the voltage regulator can operate anywhere on a tential diiTerence for biasing the transistor M7 into con -25 volt line T83. When an overload condition occurs duction is cancelled by an increase of potential drop at the maximum load current of 1 ampere, the return across the diode 112. Therer’ore, the ratio of potential path of the load potential E0 and the load current IL drop across the resistors R1 and R2 for biasing the tran is shown by the turn-oliC curve T36 which is a straight sister M7 into conduction remains constant and the maxi line. This straight line results from the linear relation mum load current lL at which the overload protection cir 55 between the resistors R1, R2 and R3 in relation to the cuit becomes operative remains constant. voltage En and ground potential. The slope 'When the load 34 returns to a condition such that there is a voltage drop across resistor RL indicating a required load current of maximum load current or less to cause a En E decreased voltage En to be impressed on the lead Th2, 60 of the turn-ofi line may be expressed by the following the potential drop across resistor R1 will be less than the relation when the transistor 117 is biased into conduc potential drop across the resistor R2. Thus, the tran» tion upon the occurrence of an overload condition: sistor lil? is biased out of conduction, the transistor 124 is biased out of conduction, and the transistor d-i- is biased IL- R2 into conduction to cause the» transistors 38 and 26 to be 65 Thus, the return path of the load current and the load biased into conduction. Thus, the normal regulating ac tion of the voltage comparator circuit 96, as previously described, 'will continue. While it will be understood that the circuit specifica tion of the power supply of the invention may vary ac cording to the design of any particular- application, the following circuit speciíications for a power supply are in cluded, by way of example only, suitable to supply a voltage is determined only by the values of the resistors R1, R2 and R3 in the two voltage divider circuits. i This linear turn-on' curve ide allows the voltage regulator to 70 turn completely oli when an overload condition at maxi mum load current occurs and to turn completely on to supply maximum load upon removal or" the overload condition. The operation of the circuit when turning on to supply a load which is less than maximum is shown by regulated voltage ofA ~--25 volts at a maximum load cur" 75 a line> t‘ßtl. _lt_ isA to be noted that conventional voltage adsense il impedance element and a load connected between ter minals of said source, a comparator loop coupled in par allel with said load for developing a signal proportional to minor variations in Voltage across said load and means for connecting said proportional signal to a control ter minal of said variable impedance element to overcome said minor variations when said loop is operative, com prising first impedance means coupled between said varia ble impedance element and said load for developing a i2 when said regulating element is disconnected, and a source oi biasing potential coupled to said overload means for biasing said overload means to maintain said disconnect ing signal when said load is in a condition to pass current which exceeds said maximum value. ß. A voltage regulator circuit for supplying current from an unregulated source through a load, comprising regulating means controlled to vary in impedance to load current coupled between one terminal of said source and iirst potential, second impedance means coupled from 10 said load and having a control terminal, voltage compar one side of said load at a point between said Variable impedance element and said iirst impedance means to the opposite side of said load for developing a second poten tial proportional to the voltage across said load, and switching means coupled from between said first imp-ed ance means and said load to said second impedance means to be rendered conductive or nonconductive in response ing means including a ñrst differential ampliñer con» nected to develop a signal proportional to minor varia tions of potential across said load and including a second differential amplifier connected to said control terminal for responding to said proportional signal to control said regulating means for correcting said minor variations, iirst voltage dividing means coupled between said regulat ing means and said load, second voltage dividing means coupled from one side of said load at a point between and including means coupled to said comparator loop for 20 said regulating means and said first voltage dividing means applyingk an overload signal to bias said switching means to the other side of said load and responsive to the volt~ into conduction for controlling said comparator loop to age developed across said load, overload means con be inoperative and to increase the impedance of said im trollable to be biased into a first state of conduction or to the diíîerence in potential of said first and second po tentials across said first and second impedance means pedance element to disconnect said source from said load into a second state of nonconductin and coupled between when said current through said load exceeds a predeter 25 said first and second voltage dividing means responsive mined value. to a potential difference having a polarity indicative of a 6. A regulator circuit comprising an unregulated volt maximum load current for being biased to said iirst state age source having first and second terminal, a series cir to apply an overload signal to said second dilierential cuit including in relative order a variable impedance amplifier for disconnecting said regulating means, a cur coupled to said first terminal, a iixed impedance and a 30 rent leakage path coupled in parallel with said regulating load coupled to said second terminal, means connected element to conduct current for maintaining said potential in parallel with said load including a differential amplifier difference when said regulating element is disconnected, to develop a proportional signal in response to minor and a source of biasing potential for biasing said overload variations of potential across said load and including means to maintain said overload signal when said polarity means for coupling said proportional signal to a control 35 is indicative of said maximum load current. terminal of said variable impedance to overcome said 9. A regulator circuit to supply current at a constant minor variations, voltage divider means coupled from potential from an unregulated source through a load between said variable impedance and said iixed imped coupled between terminals of said source and comprising ance to said second terminal, switching means having a regulating transistor having an emitter-collector path either a first state of conduction or a second state of non 40 coupled between said source and said load and having a conduction and coupled from between said fixed imped~ base, an impedance coupled between said ernitter-col~ ance and said load to said voltage divider means to be lector path and said load to form a first voltage divider responsive to the difference in potential across said fixed with said load, a second voltage divider coupled from impedance and said load and across said voltage divider between said regulating transistor and said impedance means to supp-ly a disconnecting signal to said variable 45 across said load for responding to variations of potential impedance when current through said load exceeds a pre across said load, a comparator circuit including a first determined Value to bias said switching means to said differential amplifier coupled across said load for develop ñrst state, and a leakage path across said variable imped~ ing a signal proportional to variations of potential across ance for conducting a current to maintain said discon said load, a source of maintaining potential, a second dif necting signal while said load is in a condition to pass 50 ‘erential amplifier coupled between said base of said regu~ a current which exceeds said predetermined value. lating transistor and said source of maintaining potential 7. A voltage regulator comprising an unregulated and connected to respond to said proportional signal for source, a series circuit including a regulating element and controlling the impedance of said regulating transistor to a load coupled between terminals of said source, a feed correct said variations of potential, a first overload tran» back loopl coupled to develop a signal proportional to variations of potential across said load and including sistor having a base coupled to said iirst voltage divider and having an emitter-collector path coupled to said sec ond voltage divider, a second overload transistor having a base coupled to the emitter-collector path of said first impedance means coupled between said regulating ele overload transistor and having an emitter-collector path ment and said load for forming a first Voltage divider 60 coupled between said source of maintaining potential and with said load, a second voltage divider coupled from said second differential amplifier to overcome said pro between said regulating element and said ñrst voltage portional signal and disconnect said regulating transistor divider across said load, overload means having a ñrst when said first overload transistor is biased into conduc amplifying means for coupling said proportional signal to a control terminal of said regulating element, a first state where said overload means is conductive and a sec tion in response to a predetermined polarity of a poten~ ond state where said overloadV means is nonconductive 65 tial difference between said first and second voltage di~ and coupled to said íirst and second voltage dividers to viders indicative of a greater than maximum load current, be responsive to the diderence in potential between said first and second voltage dividers for developing a discon and a leakage path across said emitter-collector path of when current through said load exceeds a maximum value than maximum current would pass through said load. 10. A power supply circuit to provide load current at said regulating transistor for passing current through said necting signal for increasing the impedance of said regu~ first and second voltage dividers to maintain said poten lating element to disconnect said source from said load 70 tial diiïerence when said polarity is indicative that greater and said overload means is biased to said first state, a cur rent leakage path coupled in parallel to said regulating element for passing a current through said first and second a constant potential from an unregulated source to a load to disconnect said source from said load during an voltage dividers to maintain said difference in potential 515 >and overload condition when said> load currentexceeds a pre 8,076,135 13 determined value, comprising a regulating transistor hav ing a load current path coupled between said source and said load and having a base terminal, signal amplitier means coupled to said base terminal for controlling the impedance of said regulating transistor and having a con trol terminal, a voltage comparator coupled across said load to respond to potential variations and coupled to said control terminal of said amplilier means for correct ing said potential variations, a iirst resistor coupled between said load current path of said regulating transistor and said load for forming a first voltage divider with said load, a second voltage divider coupled from one 14 pliiier coupled to develop a signal proportional to the potential variation across said load and including a sec~ ond differential amplifier coupled between said base ter minal and a source of biasing potential being positive rela. tive to said positive terminal of said source for responding to said proportional signal developed by said comparator loop to vary the impedance of said regulating transistor for correcting said potential variation, a first control tran. sistor having a base coupled to said first voltage divider and to said source of biasing potential and having an emitter-collector path with one end coupled to said sec ond voltage divider for responding to the potential de veloped thereby, a second control transistor having a base coupled to the other end of said emitter-collector path of path of said regulating element and said lirst resistor to the other side of said load for responding to the potential 15 said first control transistor and having an emitter-col lector path coupled between said source of biasing po across said load, a tirst signal forming transistor having tential and said second dilferential amplifier, said first a base coupled to said tirst voltage divider and having control transistor responding to the potential difference an emitter-collector path coupled to said second voltage across said first and second voltage dividers for being divider, a second signal forming transistor coupled be tween said emitter-collector path of said first signal fortn 20 biased into conduction to in turn bias said second control transistor into conduction to develop an overload signal ing transistor and said amplifier means and being biased for disconnecting said regulating transistor in response to into »conduction for developing an overload signal in re an overload current condition, said source of biasing po sponse to a predetermined polarity of potential between tential maintaining said overload signal, and a leakage said first and second voltage dividers for biasing said iirst signal forming transistor into conduction indicative of 25 path across said regulating transistor for passing current from said first and second voltage dividers to render them an overload condition causing said load current to exceed responsive for maintaining said control transistor biased said predetermined value, said overload signal acting to in conduction during said overload condition. increase the impedance of said regulating element to de side of said load at a point between said load current crease said load current to a maintaining current having a small value relative to said predetermined value, said 30 maintaining current passing through said first and second voltage dividers to maintain said overload signal for dis connecting said source from said load during the occur rence of said overload condition. 11. A circuit connected between the positive and nega 35 tive terminals of an unregulated source to supply current through a load at a constant potential, comprising a regu lating transistor having an emitter-collector path coupled References Cited in the iile of this patent UNITED STATES PATENTS 825,023 2,832,900 2,888,633 2,896,151 2,904,742 2,915,693 2,922,945 Marantette ___________ __ Feb. 25, Ford ________________ __ Apr. 29, Carter ______________ __ May 26, Zelinka _____________ __ July 21, Chase ______________ .__ Sept. 15, Harrison _____________ __ Dec. 1, Norris et al ___________ __ I an. 26, 1958 1958 1959 1959 1959 1959 1960 between said negative terminal of said source and said OTHER REFERENCES load and having a base terminal, a resistor coupled be 40 tween said regulating transistor and said load to form a “The Emitter-Coupled Dilïerential Amplifier,” Slaugh first voltage divider with said load, a second voltage di ter, IRE Transactions, March 1956, pp. 51-53. vider coupled between said regulating transistor and said Dodge: “A Transistorized Overload-Proof Electronic resistor to said positive terminal for developing a poten Regulator,” Transistor and Solid State Circuit Conference, tial proportional to the potential developed across said load, a comparator loop including a íirst diiierential arn Digest of Technical Papers, Feb. 2G, 1958, pp. 35-36.