GB1559788A - Power supply apparatus - Google Patents

Power supply apparatus Download PDF

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Publication number
GB1559788A
GB1559788A GB1559775A GB1559775A GB1559788A GB 1559788 A GB1559788 A GB 1559788A GB 1559775 A GB1559775 A GB 1559775A GB 1559775 A GB1559775 A GB 1559775A GB 1559788 A GB1559788 A GB 1559788A
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United Kingdom
Prior art keywords
means
power supply
connected
voltage
re
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Expired
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GB1559775A
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Post Office
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Post Office
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Priority to GB1559775A priority Critical patent/GB1559788A/en
Publication of GB1559788A publication Critical patent/GB1559788A/en
Application status is Expired legal-status Critical

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Classifications

    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02JCIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J9/00Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting
    • H02J9/04Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source
    • H02J9/06Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source with automatic change-over
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04MTELEPHONIC COMMUNICATION
    • H04M19/00Current supply arrangements for telephone systems

Description

(54) POWER SUPPLY APPARATUS (71) We, THE POST OFFICE, a British corporation established by Statute, of 23, Howland Street, London, W1P 6HQ, do hereby declare the invention, for which we pray that a patent may be granted to us.

and the method by which it is to be per- formed, to be particularly described in and by the following statement: This invention relates to power supply apparatus. In particular, but not exclusively, it relates to power supply apparatus for tele phone exchanges.

It is obviously desirable for telephone Cx- change power supplies to be independent of the public electricity supply: in the event of a failure of the public electricity supply it is clearly advantageous for telephones, telex, private circuits and television systems to con tinue their normal functions. Much effort is directed towards designing means for main taining the telephone exchange electricity power supply during breaks in the public electricity supply. It is also desirable to en sure that, as far as possible, any failures of component parts of the telephone exchange power supply apparatus shall not cause the telephone exchange to cease operation.

In our UK Patent Specification 1,266,353 a power supply system which needed com mon control equipment and which employed what is known to those skilled in the art at end-cell switching was described. An alterna tive approach would be to use a system with an integral control system and transistor re gulation, this would have economic advan tages in some situations.

It is also desirable that, when lead/acid batteries are to be used in a power supply apparatus, the batteries should be kept in what is known to those skilled in the art as the "trickle charge" state when not supply ing power. This state is achieved by main taining a potential of about 2.3V across each cell of the battery. In the trickIe charge state the cells do not lose their charge because of internal discharging.

It is therefore an object of the present invention to provide an economic electrical power supply apparatus which may be used in telephone exchanges.

According to the invention there is provided a power supply apparatus including a first and a second re-chargeable electrical power storage means connected in series so that the second terminal of the first re-chargeable storage means is connected to the first terminal of said second re-chargeable storage means, first and second output terminals, a first main source of electrical power connected across said first and second re-chargeable power storage means, a second main source of electrical power connected across said output terminals, current regulation means connected between the second terminal of said second re-chargeable storage means and the first output terminal, said current regulation means normally being non-conductive and being arranged to change to a conductive state when the voltage across said output terminals falls to a predetermined value so as to maintain the voltage across said output terminals substantially constant, and a first unidirectionally conductive means connected between said first output terminal and the junction of said first and second re-chargeable storage means and poled so that like poles of said first rechargeable electrical power storage means and said first unidirectionally conductive means are connected, the first terminal of said first rechargeable electrical power storage means being connected to said second output terminal.

One embodiment of the present invention will now be described by way of example with reference to the accompanying drawing which shows diagrammatically a power supply apparatus according to the invention. Referring now to the drawing, the apparatus includes first power supply means 1, which is supplied by public electricity supply 14 and transforms, rectifies and smoothes the alternating current input to produce a direct current output. There is also provided a second power supply means 2, which is supplied by public electricity supply 15 and which is similar in construction to said first power supply means 1. On installation, the output voltages of said first and said second power supply means 1 and 2 are adjusted, respectively, to 59V and 51.5V. There is further provided a rechargeable battery of cells 13 of the Plant, otherwise called lead/acid, type.

Said re-chargeable battery of cells 13 is connected in parallel across said first power supply means 1, and said re-chargeable battery of cells 13 is divided into two parts labelled 3 and 4 in Fig. 1. Said part 3 of said re-chargeable battery of cells 13 contains four cells and said part 4 of said rechargeable battery of cells 13 contains 22 cells. There is further provided current regulation means 10 connected between outputs of like polarity of said first power supply means 1 and said second power supply means 2. Said current regulation means is connected to potential sensing lead 11. There are further provided output terminals 16 and 17.

which are connected, respectively to the two outputs of said second power supply means 2. Said potential sensing lead 11 is connected to the output terminals 17. There is further provided a first unidirectionally conductive means 8 which is a diode of semi conductive material connected between out put terminal 16 and point 5, where point 5 is the junction between said part 3 of said re-chargeable battery of cells 13 and said part 4 of said re-chargeable battery of cells 13.

There is shown diagrammatically in Fig.

1 load 9, which in a telephone exchange would be the apparatus which it was desired to supply with electrical power, and fuse 12 which diagrammatically represents the fuses in series with the apparatus. The series arrangement of said load 9 and said fuse 12 is connected across said output terminals 16 and 17. Said current regulation means 10 may conveniently control the current by a Darlingron arrangement of a pair of transistors, several such arrangements being connected in parallel if the current required is too great for one arrangement alone.

There is further provided second unidirec tionally conductive means 18, which is a diode of semiconductive material connectable in parallel with said current regulation means 10. Said current regulation means 10 is adapted to detect the current flowing through itself and to be able to limit this current to a level such as will not damage itself.

The operation of the apparatus shown in the drawing will now be described.

The operation when the public electricity supply is working, which will be termed in this Specification the "normal" State, will first be described. When the public electricity supply is applied, said first power supply means 1 will supply current to charge said battery of re-chargeable cells 13 to 59V, and since said battery of re-chargeable cells 13 has 26 cells, therein, the potential across each cell will be 2.27V. A lead/acid battery, when kept under these conditions, is in what is known to those skilled in the art as a "trickle charge" state5 in which state a small current flows through the battery which keeps the battery charged as well as offsetting the losses due to internal discharge. Under these conditions a lead/acid battery can be preserved in a good working state for many years.In the normal state the potential difference between point 5 and point 6 will be 49.92V.

Still considering the normal state of operation said second power supply means 2 will supply 51.5V to the output terminals 16 and 17, thus applying electrical power to the load 9 through the fuse 12. The potential difference between point 6 and point 7 will be 51.5V and thus the potential difference across the unidirectionally conductive means 8 will be about 1.5V and the potential across the unidirectionally conductive means 18 will be 7.5V. The direction of these potential differences is such as to reverse bias said unidirectionally conductive means 8 and 18 which are therefore biased into a non-conducting state. The current regulation means 10 is set to be non-conducting when the voltage sensed across the output terminals 16 and 17 is greater than 51V.In the normal state therefore said current regulation means 10 is non-con ducting. The operation of the power supply in the normal state may thus be summarised as follows: The first power supply means 1 main tains the battery of re-chargeable cells 13 in a trickle charge state, while the second power supply means 2 supplies the load 9 with electrical power.

The first change from the normal state which will be considered is the failure of the public electricity supply. When the public electricity supplies 14 and 15 to the first and the second power supply means 1 and 2 fail.

the output from both the first and the second power supply means 1 and 2 will cease. The current regulation means 10 will sense the fall of output voltage through the sensing lead 11 and the current regulation means 10 is arranged to conduct when the voltage be tween the output terminals 16 and 17 has fallen to 51V.

Using the electricity supply from the rechargeable battery of cells 13 the current regulation means 10 will pass a current sufficient to maintain the voltage between the output terminals 16 and 17 at 51V, so long as the output voltage of the re-chargeable battery of cells 13 is greater than 53V; when this output voltage falls below 53V the cur rent regulation means 10 will maintain a potential of 2V less than the output voltage of the re-chargeable battery of cells 13 across the output terminals 16 and 17. As the output voltage of the re-chargeable battery of cells 13 falls further, so the potential across the output terminals 16 and 17 will fall; for telephone exchanges the minimum working voltage is 46V.

In telecommunications, it has long been the philosophy to rely on fuses to protect the equipment in an exchange from excessive currents should a fault occur in the equip ment which causes a short circuit or, in some cases, which causes a continuous current.

Such a philosophy relies on the power supply to the exchange having the ability to provide a very large current indeed (many hundreds of amperes) for a short time, in order to blow the fuse in an acceptably short period. The ability of the present power supply apparatus to provide a very large current to blow a fuse has to be specially provided since the current regulation means 10 and the power supply means 2 each have a maximum current which they can pass in safety and each is designed to restrict the current passing through itself to the particular value. The first unidirectionally conductive means 8 provides the ability to blow a fuse.When a short circuit occurs in the load 9, the current supplied by the regulation means 10 will increase in order to attempt to maintain the voltage across output terminals 16 and 17 at 51V As the current rises the current limiting ability of the current regulation means 10 will come into effect and the current will fall below that value which is required to maintain the voltage across the output terminals 16 and 17 at 51V. When this current limiting comes into effect the voltage at point 7, which is of course at the same potential as the output terminal 16 (apart from a small voltage drop in the connecting wire) and point 6 will fall below 51V, and will eventually fall so far as to forward bias the unidirectionally con ductive means 8.

When the unidirectionally conductive means 8 is forward biased it appears, as far as the part 4 of the re-chargeable battery of cells 13 is concerned, as a very low resistance and thus said part 4 of the re-chargeable battery of cells 13 sees the short circuit in the load 9 directly. Sufficient current can now pass, for a short time, from the part 4 of the re-chargeable battery of cells 13 through the unidirec tionally conductive means 8 to blow the fuse 12 and thus isolate the part of the load 9 which was short circuited. When the fuse 12 has blown the circuit will restore to its condition before the fault had occurred, with the unidirectionally conductive means 8 and in its non-conducting state.

It will be appreciated by those skilled in the art that there are further advantages in the embodiment shown in the drawing. For example, where the public electricity supply does not fall, but power supply means 2 is unable to supply the full load or a fault has occurred therein, the re-chargeable battery of cells 13 and the power supply means 1, in conjunction with the current regulation means 10 are quite capable of maintaining the supply of electrical power to the telephone exchange for a very long time. It will be further appreciated by those skilled in the art, that if the current regulation means 10 should fail in addition to the second power supply means 2, then the first power supply means 1 is able, by gassing the 4 cells which comprise part 3 of re-chargeable battery of cells 13, to maintain the electricity supply to the load 9.The gassing of any cells in a lead/acid battery is undesirable as a regular practice, but in an emergency, in order to maintain public telecommunications facilities, it is acceptable.

The second unidirectionally conductive means 18 connected in parallel with the current regulation means 10 is provided in order to prevent damage to the semi-conductive devices in the current regulation means 10. It is found, in practice, that in telephone exchanges it is possible to generate large voltage "spikes", where a very high voltage appears for a very short time, especially when high currents are broken in the apparatus in the exchange. If no protective means were provided these voltage spikes would be applied to the current regulation means 10 in the opposite polarity to that in which it normally works, and this could well damage the components of the current regulation means 10.The second semiconductive means 18 provides a low resistance shunt to voltage of this opposite polarity and therefore provides protection for the current regulation means 10.

Again, those skilled in the art will appreciate that the first unidirectionally conductive means 8 ensures that the maximum potential difference developed across the current regulation means 10 is equal to the sum of the potential difference across the part 3 of the rechargeable battery of cells 13 and the small potential difference across the first unidirectionally conductive means 8. Also, it will be appreciated by those skilled in the art that the unidirectionally conductive means 8 can, when the current limiting ability of the current regulation means 10 is in operation pass a continuous current and thus provide the power supply apparatus with the ability to carry an overload continuously without damage to itself. Of course, it will be appreciated that the current rating of unidirectionally conductive means 8 must be chosen to take this ability into account.

Furthermore, those skilled in the art will also appreciate that second unidirectionally conductive means 18 permits the second power supply means 2 to re-charge the rechargeable battery of cells 13, if the first power supply means is inoperative, to a maximum voltage of 51V.

It will be realised that in use in a telephone exchange a power supply apparatus of the type described will only infrequently be required to operate to maintain the electricity supply to the exchange when the public electricity supply fails. It is very desirable to be able to detect a fault in a component which is only brought into operation when the public electricity supply fails.

Some protection against undetected faults of this nature can be provided by a voltage monitoring device connected across the first unidirectionally conductive means 8, and arranged to provide an alarm when the voltage across the first unidirectionally conductive means 8 falls to zero.

In practice, the second power supply means 2 is unable to respond immediately to sudden increases in load. Also it is found in practice that the public electricity supply suffers from minor breaks and interruptions of short duration, when of course, the second power supply means 2 is also unable to supply the load. In circumstances where the second power supply means 2 cannot supply all or part of the load and current regulation means 10 is brought into operation, as previously described. If the current regulation means 10 is faulty when called into operation, the load can still be supplied above 46V by part 4 of rechargeable battery of cells 13 alone for a short time, as the output voltage falls to allow conduction of first unidirectionally con ductive means 8.As the bias on the first uni directionally conductive means 8 changes direction it will pass through zero and this will be detected by the voltage monitoring device and an alarm will be given.

Since a short break in the public electricity supply or a sudden increase in load is more probable than a long break in the public electricity supply, it is highly problable that a fault in the current regulation means 10 will be detected before a prolonged public elec tricity supply failure; as has been previously said, the power supply apparatus can still supply the load above 46V during a short break in the public electricity supply even if the current regulation means 10 is faulty.

The voltage monitoring device wiU also give an alarm if the load demanded is greater than the combined potential capacities of the second power supply means 2 and the cur rent regulation means 10. Also, an alarm will be given if the battery voltage exceeds a gassing potential of 2.36V per cell with the output at the normal value of 51.5V.

WHAT WE CLAIM IS:- 1. A power supply apparatus including a first and a second re-chargeable electrical power storage means connected in series so that the second terminal of the first re-chargeable storage means is connected to the first terminal of said second re-chargeable storage means, first and second output terminals, a first main source of electrical power connected across said first and second re-chargeable power storage means, a second main source of electrical power conected across said output terminals, current regulation means connected between the second terminal of said second re-chargeable storage means and the first output terminal, said current regulation means normally being non-conductive and being arranged to change to a conductive state when the voltage across said output terminals falls to a predetermined value so as to maintain the voltage across said output terminals substantially constant, and a first unidirectionally conductive means connected between said first output terminal and the junction of said first and second re-chargeable storage means and poled so that like poles of said first rechargeable electrical power storage means and said first unidirectionally conductive means are connected, the first terminal of said first rechargeable electrical power storage means being connected to said second output ter final 2.A power supply apparatus as claimed in claim 1 wherein said current regulation means comprises a plurality of transistors arranged as one or more Darlington pairs in parallel.

3. A power supply apparatus as claimed in Claim 1 or Claim 2 wherein a second unidirectionally conductive means is connected in parallel with the current regulation means and is poled so that unlike poles of said first and said second unidirectionally conductive means are directly connected.

4; A power supply apparatus as claimed in any preceding Claim in which said first and said second re-chargeable electrical power storage means are each a plurality of lead/acid cells.

5. A power supply apparatus as claimed in any preceding claim in which said first and second power supply means are each con nectable to receive an electrical power supply from the public electric main.

6. A power supply apparatus as claimed in any preceding Claim wherein a voltage sensitive detector is arranged to give an alarm if the voltage across the first unidirectionally conductive means falls to zero.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. It will be realised that in use in a telephone exchange a power supply apparatus of the type described will only infrequently be required to operate to maintain the electricity supply to the exchange when the public electricity supply fails. It is very desirable to be able to detect a fault in a component which is only brought into operation when the public electricity supply fails. Some protection against undetected faults of this nature can be provided by a voltage monitoring device connected across the first unidirectionally conductive means 8, and arranged to provide an alarm when the voltage across the first unidirectionally conductive means 8 falls to zero. In practice, the second power supply means 2 is unable to respond immediately to sudden increases in load. Also it is found in practice that the public electricity supply suffers from minor breaks and interruptions of short duration, when of course, the second power supply means 2 is also unable to supply the load. In circumstances where the second power supply means 2 cannot supply all or part of the load and current regulation means 10 is brought into operation, as previously described. If the current regulation means 10 is faulty when called into operation, the load can still be supplied above 46V by part 4 of rechargeable battery of cells 13 alone for a short time, as the output voltage falls to allow conduction of first unidirectionally con ductive means 8.As the bias on the first uni directionally conductive means 8 changes direction it will pass through zero and this will be detected by the voltage monitoring device and an alarm will be given. Since a short break in the public electricity supply or a sudden increase in load is more probable than a long break in the public electricity supply, it is highly problable that a fault in the current regulation means 10 will be detected before a prolonged public elec tricity supply failure; as has been previously said, the power supply apparatus can still supply the load above 46V during a short break in the public electricity supply even if the current regulation means 10 is faulty. The voltage monitoring device wiU also give an alarm if the load demanded is greater than the combined potential capacities of the second power supply means 2 and the cur rent regulation means 10. Also, an alarm will be given if the battery voltage exceeds a gassing potential of 2.36V per cell with the output at the normal value of 51.5V. WHAT WE CLAIM IS:-
1. A power supply apparatus including a first and a second re-chargeable electrical power storage means connected in series so that the second terminal of the first re-chargeable storage means is connected to the first terminal of said second re-chargeable storage means, first and second output terminals, a first main source of electrical power connected across said first and second re-chargeable power storage means, a second main source of electrical power conected across said output terminals, current regulation means connected between the second terminal of said second re-chargeable storage means and the first output terminal, said current regulation means normally being non-conductive and being arranged to change to a conductive state when the voltage across said output terminals falls to a predetermined value so as to maintain the voltage across said output terminals substantially constant, and a first unidirectionally conductive means connected between said first output terminal and the junction of said first and second re-chargeable storage means and poled so that like poles of said first rechargeable electrical power storage means and said first unidirectionally conductive means are connected, the first terminal of said first rechargeable electrical power storage means being connected to said second output ter final
2.A power supply apparatus as claimed in claim 1 wherein said current regulation means comprises a plurality of transistors arranged as one or more Darlington pairs in parallel.
3. A power supply apparatus as claimed in Claim 1 or Claim 2 wherein a second unidirectionally conductive means is connected in parallel with the current regulation means and is poled so that unlike poles of said first and said second unidirectionally conductive means are directly connected.
4; A power supply apparatus as claimed in any preceding Claim in which said first and said second re-chargeable electrical power storage means are each a plurality of lead/acid cells.
5. A power supply apparatus as claimed in any preceding claim in which said first and second power supply means are each con nectable to receive an electrical power supply from the public electric main.
6. A power supply apparatus as claimed in any preceding Claim wherein a voltage sensitive detector is arranged to give an alarm if the voltage across the first unidirectionally conductive means falls to zero.
7. A power supply apparatus as claimed in
any preceding Claim in which the first unidirectionally conductive means is a semiconductive device.
8. A power supply apparatus substantially as hereinbefore described with reference to the accompanying drawing.
GB1559775A 1976-07-05 1976-07-05 Power supply apparatus Expired GB1559788A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB1559775A GB1559788A (en) 1976-07-05 1976-07-05 Power supply apparatus

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB1559775A GB1559788A (en) 1976-07-05 1976-07-05 Power supply apparatus

Publications (1)

Publication Number Publication Date
GB1559788A true GB1559788A (en) 1980-01-23

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Family Applications (1)

Application Number Title Priority Date Filing Date
GB1559775A Expired GB1559788A (en) 1976-07-05 1976-07-05 Power supply apparatus

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0243061A2 (en) * 1986-04-17 1987-10-28 AT&T Corp. Off-line switcher with battery reserve

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0243061A2 (en) * 1986-04-17 1987-10-28 AT&T Corp. Off-line switcher with battery reserve
EP0243061A3 (en) * 1986-04-17 1989-08-02 American Telephone And Telegraph Company Off-line switcher with battery reserve

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Legal Events

Date Code Title Description
PS Patent sealed
746 Register noted 'licences of right' (sect. 46/1977)
732 Registration of transactions, instruments or events in the register (sect. 32/1977)
PCNP Patent ceased through non-payment of renewal fee

Effective date: 19950705