US3571691A

US3571691A - Regulated dc power supply

Info

Publication number: US3571691A
Application number: US764235A
Authority: US
Inventors: Koji Iwata; Kenjiro Yokoyama
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 1967-10-02
Filing date: 1968-10-01
Publication date: 1971-03-23
Anticipated expiration: 1988-03-23

Abstract

A regulated DC power supply consisting of a voltage regulating circuit which supplies the load with a current just to compensate the variation in the load current and another circuit connected in parallel to said voltage regulating circuit which supplies the remaining and constant portion of the load current, thereby making it possible to reduce the necessary current bearing capacity of the regulating components.

Description

United States Patent [72] Inventors Kojilwata;

Kenjiro Yokoyama, Hitachi-shi, Japan [21 Appl. No. 764,235 [22] Filed Oct. 1, 1968 [45] Patented Mar. 23, 1971 [73] Assignee Hitachi, Ltd.

Tokyo, Japan [32] Priority Oct. 2, 1967, Oct. 20, 1967 J p [31] 42/63047 and 42/67242 [54] REGULATED DC POWER SUPPLY 3,356,927 12/1967 Barron 321/18 3,443,203 5/1969 Krayenbrink... 323/38X 2,092,891 9/1937 Overbeck 307/58X 2,495,783 1/1950 Sorensen 307/58 2,872,636 2/1959 Wheatley 321/27 3,281,652 10/1966 Perrins 323/19 3,289,069 11/1966 Todd 321/18 3,375,428 3/1968 Mitchell 323/22(SGR) 3,408,559 10/1968 Bambace et al. 323/22(t) 3,447,062 5/1969 Bixby 321/5 FOREIGN PATENTS 718,594 11/1954 Great Britain 321/27 Primary ExaminerWilliam M. Shoop, Jr. Att0rneyCraig, Antonelli, Stewart & Hill ABSTRACT: A regulated DC power supply consisting of a voltage regulating circuit which supplies the load with a current just to compensate the variation in the load current and another circuit connected in parallel to said voltage regulating circuit which supplies the remaining and constant portion of the load current, thereby making it possible to reduce the necessary current bearing capacity of the regulating components.

APPS

PATENTED HAR23 l9?! SHEET 2 [IF 2 INVENTORS koa/ llvnrn kmva/Ro Para mwn u E Z m 1 lu N a 1 7w. H a I A ATTORNEYS REGULATEE EEC POWER SUPPLY BACKGROUND OF THE INVENTION This invention relates to a regulated DC power supply which is especially effective as a DC power supply for a large current load such as an electronic computer or the electronic telephone exchanger and which is characterized in that a separate supply circuit is provided in parallel to the ordinary voltage regulating circuit. An object of this invention is to obtain a compact and economical regulated power supply by making the regulating circuit to deal only with the variable component of the load current.

Another object of this invention is to provide a transistorized regulated voltage supply of a large current capacity with a regulating circuit of a small current capacity, by supplying only one portion of the load current through the regulating circuit and regulating the remaining portion of the load current by said one portion.

A conventional regulated DC power supply comprises a variable resistance element between the source and the load, and means for detecting the output voltage from the regulated power supply per se, resistivity of said variable resistance element being controlled in response to the voltage detected by said detecting means, and the output voltage being regulated by the voltage drop across said variable resistance element.

An example of the known regulated power supply is shown in FlG. l. The operation of the circuit shown in FIG. B will be described hereunder. The AC current from an AC power source E is rectified through a transformer T, and a diode D charging a capacity C,. The rectified current i is fed to a capacity C, connected across the output terminals. Assuming that the terminal voltage of the capacity C is V, and that of the capacity C, is the voltage V, must be higher than the voltage V by a value corresponding to the voltage drop across the variable resistance element VR as the current i flows through the element VR.

The voltage V is constantly compared with the reference voltage l by a comparator C which detects any variation in the voltage V and automatically varies the resistance of the element VR so as to maintain the voltage V at a fixed value. The voltage regulating circuit represented by the variable resistance element VR and the comparator C is usually constructed as shown in FIG. 2.

in a low voltage power supply, the variable resistance element VR in EEG. l is often comprised of transistors Tr Tr and Tr,,,,..... Tr,,,,,. These transistors are connected all in parallel through the respective emitter resistors R R, and El R Variation of the output voltage V is detected after being divided by the resistors R, and R and is compared with the reference voltage V The comparator C provides the transistors with a bias current depending on the difference between the detected voltage and the reference voltage, thereby varying the internal resistances of the transistors "in, Tr and Tr,,,, Tr,,,,,. The transistors Tr and Tr serve to amplify the bias currents which are supplied to the transistors Tr Tr, belonging to the transistor group Tr i and the transistors Tr Tr belonging to the transistor group Tr respectively. Accordingly, the emitter to collector resistance of the transistors Tr Tr, and Tr,,,, Tr is varied depending on the variation of the output voltage V so as to suppress said variation of the output voltage.

in a low voltage and large capacity power supply used in a large electronic computer or electronic telephone exchanger, the number of transistors connected in parallel to constitute the variable resistance element as mentioned above, is otten as many as several hundred. For example, in a large electronic computer which takes a DC current of 500 to I000 A, the number of said transistors usually reaches the order of two hundred, though the number varies more or less depending on the capacity of the transistors used. Such a power supply unit is inevitably very builry, and no attempt to reduce the size of such a unit has yet succeeded whereas there is a general tendency toward miniaturized computing circuits and memories with the aid of integrated circuits.

According to this invention, the number of transistors which constitute the variable resistance element as described above can be drastically reduced, thus reducing the size of the power unit, by controlling said variable resistance unit VR only with a current corresponding to the varied portion of the output voltage.

BRlEF DESCRIPTlON OF THE DRAWINGS FIGS. l and 2 relate to a conventional regulated DC power supply as described above;

FIG. 3 is a circuit diagram of an embodiment of the regulated DC power supply according to this invention;

FIG. 4 is a diagram for explaining the operation characteristics of the circuit shown in FIG. 3;

FIGS. 5 to 9 show various embodiments of this invention; and

MG. 10 is a diagram showing a waveform related to the operation of the circuit shown in FIG. 9.

Throughout FIGS. 3 to 10, corresponding components are indicated by similar reference marks.

DESCRIPTION OF THE PREFERRED EMBODIMENT Now, referring to FIG. 3, AC current from an AC power source E is rectified by diodes D and D through transformers T and T to charge capacitors C and C respectively.

The voltage regulating unit which consists of the variable resistance element VR and the comparator C as shown in FIG. l and is constituted as shown in FIG. 2, operates so as to maintain the terminal voltage of the capacitor C, at a fixed level. Across the capacitor C is connected the DC load to which DC current from the voltage regulating unit AVR and DC current from the diode D and the capacitor C are supplied, the latter current through a resistor R. Thus, the load current i is a sum of the current i, from the regulating unit AVR and the current i from the resistor R. Hereunder, an explanation will be made about the manner in which the circuit shown in H6. 3 operates when the load current i varies as shown in H6. 4 as a result of the change in the load.

When the load current 1' assumes a minimum value, the whole current i is supplied through the resistor R, no current being supplied from the regulating unit AVR. if the load current i increases from the value i at an instant I, as shown in H6. 4, the increment i,,=ii i, is supplied from the unit AVR. The resistance of the variable resistance element VR included in the regulating unit AVR is adjusted depending on the terminal voltage l of the capacitor C, so as to be kept at V,,,-,,,,,/i,,, V, being the terminal voltage of the capacitor C Now, assuming that the load current 1' decreases at an instant t the current i from the regulating unit AVR decreases from i u to 1' the resistance of the unit AVR changing to V,,,-

V /M112. Thus, when the load current i varies from the maximum value i to the minimum value i,,,,,,, the current i, supplied through the regulating unit AVR varies from zero to t so as to maintain the terminal voltage V of the capacitor C at a constant level, while a constant current i, is supplied to the load through the resistor R.

Further, a circuit as shown in Fit]. 5 also is constructed according to this invention, in which each pair of two transformers T and T two diodes D, and D and two capacitors C, and C shown in FlG. 3 is made into a single unit respectively, thus the current i, and i being supplied from the single rectifier unit.

in the embodiments shown in FIGS. 3 and 5, as described above, the voltage regulating unit AVR only must have a current capacity sufficient to draw the current i-i corresponding to the current variation in the load current i. That is, in the regulated DC power supply of this invention, it is suhicient for the voltage regulating unit to have a current capacity of a value corresponding to the expected maximum variation in the total load current, whereas in the conventional regulated DC power supply, the voltage regulating circuit must have a current capacity for the total load current. Therefore, according to this invention, a current flowing through the components which comprise the variable resistance element can be limited to a very small value.

For example, a conventional regulated DC power supply intended for a load which consumes a current of 500 to L000 amperes is required to have a current bearing capacity of l ,000 amperes; while in the power supply of this invention, the voltage regulating circuit is only required to have a current capacity of 500 amperes if the variable portion of the load current is 500 amperes. Thus, the number of the transistors constituting the variable resistance element of the power supply can be reduced to one-half of that in the conventional device.

in the aforegoing description, the voltage of the AC power source "1d,, was assumed to be constant. If this voltage varies, the collector loss P of the transistors in the variable resistance element must be taken into consideration.

When the emitter to collector voltage of the transistors in the variable resistance element is indicated by V and the total collector current of said transistors I then it will be understood that the product V I must be less than the collector loss P Therefore, if the voltage of the AC power source E increases by AV,,,, the following relation must be maintained:

Accordingly, the upper limit of the collector current will be lowered.

The above disadvantage is overcome in the embodiment shown in H6. 6. Referring to the FIG, a parallel and reversely connected pair of thyristors SCR is phase-controlled to adjust the output of the AC power source E Reference marks T, and T indicate transformers, D, and D diodes, CH, and CH choking coils, and C, and C capacitors, respectively. The phase-controlled AC power is rectified through a transformer T,, diodes D, and choking coil Cl-l, to charge a capacitor C,, and at the same time, said AC power is rectified through a transformer T diodes D and choking coil CH to charge a capacitor C An automatic pulse position shifter APPS controls the ignition point of the thyristor-s SCR depending on the terminal voltage of the capacitor C With this feedback control, the input voltage V, of the voltage regulating circuit is maintained at a constant level. It will be understood that the input voltage of said automatic pulse position shifter APPS may be taken from the terminal of the capacitor C, instead of the capacitor C,. p

in the embodiment shown in FIG. 7, two transformers T, and T in the embodiment shown in FlG. 6 are combined into a single transformer T,. Operation of the device of HO. 7 is similar to that of lFlG. d.

ln the embodiment shown in FIG. 8, the respective pairs of transformers, diodes, choking coils and capacitors in the embodiment shown in FIG. 6 are made into respective single components indicated by marks 1",, D,, CH, and C,. in this arrangement too, the feedback circuit including the pulse shifter APPS acts so as to keep the input voltage to the regulating unit AVR constant.

As described above in connection with H68. 6 to 8, in the regulated DC power supply of this invention which comprises a first circuit for supplying a DC current i, to the load through the voltage regulating unit AVR, a second circuit for supplying the remaining portion i, of the load current through the resistor R, said voltage regulating unit AVR being operated in response to the output voltage, and a rectifying circuit phasecontrolled so as to maintain the input voltage to said regulat ing unit at a constant level, the required current capacity of the variable resistance element in the voltage regulating unit can be drastically curtailed. Thus, if the variable resistance element consists of transistors, the transistors to be connected in parallel can be reduced by as many in number, thereby providing a compact and economical regulated power supply.

Next, another embodiment of this invention will be described referring to H6. 9.

in this embodiment of the invention, the constant component i of the load current i is obtained through a thyristor SCR which is phase-controlled by the automatic pulse position shifter APPS which generates igniting pulses at a phase angle depending on the difference between the variable component i, of the load current i and a reference current i,,. That is, if the current i, tends to increase, the igniting angle of the thyristor SCR is shifted by means of the pulse position shifter APPS so as to increase the current 1 Reference marking C' indicates a comparator for providing a signal corresponding to the difference between the current i, and a reference current i,,.

The operation of the circuit shown in FlG. will be described hereunder with reference to FIG. it).

it is assumed that the load current i decreases by A1 at an instant t, as shown in FIG. iii. The comparator C detects the rise in the output voltage V due to the decrease of the load current i and controls the variable resistance element VR accordingly. Consequently, the current i, tends to drop to i, Ai at the same instant t,. The comparator C detects said drop of the current i, and phase-controls the thyristor SCR according to the difference between the current i, and the reference current i thereby to decrease the current i, by an amount corresponding to said decrease in the current i In the above operation, the current i, responds to the variation of the load current i at the instant t, without delay, as the comparator C and the variable resistance element'VR have been selected so as to have a high speed of response. However, the response of the current i will be delayed at least one-half cycle period, because the current i, is phase-controlled through the thyristor SCR. Therefore, if the load current i varies by Ar, the current i, immediately varies so as to compensate said variation Ai, and then the current i varies to take over said variation Ai, thus the current i, is restored to the predetermined constant level. For example, if the load current i decreases at the instant t,, the current i, decreases at the same time, and then the current decreases sensing the drop in the current i, during the period At, while the current i, returns to the original level.

Also at the instant t if the load current i decreases, the current i, decreases immediately, being followed by the decrease of the current i and the consequent restoration of the current i,. During this regulating operation, the relation represented by i i, i is maintained among the currents.

Now, assuming that the load current i increases at an instant t the comparator C detects a drop in the output voltage V, due to the increase of the load current and acts so as to decrease the resistance of the variable resistance element VR, thus increasing the current i,. The comparator C detects the increase of the current i, over the reference current i and controls the pulse position shifter APPS so as to increase the conducting angle of the thyristor and therefore to increase the current i Increase of the current i, and i raises the output voltage V, above the reference voltage, which in turn increases the resistance of the variable resistance element VB, thus returning the current i, to the normal level. That is, an increase in the load current i immediately causes a corresponding increase in the current i,, being followed by an increase in the current i, and the consequent restoration of the current i, to the reference level i Generally speaking, the load current in an electronic computer or an electronic telephone exchanger varies in steps as is seen in the current i shown in FlG. W, with a comparably small variation in each step. For such a use, the power supply of this invention is especially advantageous. That is, the variable resistance element VR is only required to have a current capacity equivalent to the sum of the reference current i,, and the momentary rise of the load current; and if the variation of the load current at an instant, i.e., one step of the variation is small, the necessary capacity of the variable resistance element VR becomes considerably small. Therefore, according to this invention, a compact and economical regulated DC power supply is obtained.

We claim:

1. A regulated DC power supply for supplying a load with DC power, including a voltage regulating circuit having an input and an output which comprises:

means for rectifying an AC input voltage supplied to said input;

variable impedance means for receiving said rectified AC input voltage and for producing a current, the magnitude of which is controlled by the variation of said variable impedance means, said current being supplied to said output;

means for controlling the variation of said variable impedance means in response to the difference between the voltage at said output and a reference voltage;

means for controlling the magnitude of said AC input voltage including a phase-controlled rectifier which is phase controlled in response to the difference between the current produced by said variable impedance means and a reference current, to thereby supply said load with a controlled current, a portion of which is supplied by said phase-controlled rectifier; and

a fixed impedance element connected between said phasecontrolled rectifier and said output through which said portion of said controlled current is supplied.

2. A regulated DC power supply for supplying a load with DC power comprising:

first and second circuits mutually connected in parallel between an AC power source and a load, wherein said first circuit comprises a means for rectifying the voltage produced by said AC power source;

variable impedance means including at least one transistor circuit responsive to said rectified voltage for supplying a current to said load, the magnitude of which is varied according to the difference between the terminal voltage across the load and a reference voltage; and

said second circuit comprising a phase-controlled rectifier receiving a voltage from said AC power source, responsive to the difference between the output of said variable impedance means and a reference current for controlling the magnitude of said AC voltage and for supplying said load with a controlled current in addition to the current supplied by said variable impedance means.

Claims

1. A regulated DC power supply for supplying a load with DC power, including a voltage regulating circuit having an input and an output which comprises: means for rectifying an AC input voltage supplied to said input; variable impedance means for receiving said rectified AC input voltage and for producing a current, the magnitude of which is controlled by the variation of said variable impedance means, said current being supplied to said output; means for controlling the variation of said variable impedance means in response to the difference between the voltage at said output and a reference voltage; means for controlling the magnitude of said AC input voltage including a phase-controlled rectifier which is phase controlled in response to the difference between the current produced by said variable impedance means and a reference current, to thereby supply said load with a controlled current, a portion of which is supplied by said phase-controlled rectifier; and a fixed impedance element connected between said phasecontrolled rectifier and said output through which said portion of said controlled current is supplied.

2. A regulated DC power supply for supplying a load with DC power comprising: first and second circuits mutually connected in parallel between an AC power source and a load, wherein said first circuit comprises a means for rectifying the voltage produced by said AC power source; variable impedance means including at least one transistor circuit responsive to said rectified voltage for supplying a current to said load, the magnitude of which is varied according to the difference between the terminal voltage across the load and a reference voltage; and said second circuit comprising a phase-controlled rectifier receiving a voltage from said AC power source, responsive to the difference between the output of said variable impedance means and a reference current for controlling the magnitude of said AC voltage and for supplying said load with a controlled current in addition to the current supplied by said variable impedance means.