CA1173902A - Standby power unit - Google Patents
Standby power unitInfo
- Publication number
- CA1173902A CA1173902A CA000399682A CA399682A CA1173902A CA 1173902 A CA1173902 A CA 1173902A CA 000399682 A CA000399682 A CA 000399682A CA 399682 A CA399682 A CA 399682A CA 1173902 A CA1173902 A CA 1173902A
- Authority
- CA
- Canada
- Prior art keywords
- battery
- power
- charger
- inverter
- power supply
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04M—TELEPHONIC COMMUNICATION
- H04M19/00—Current supply arrangements for telephone systems
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J9/00—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting
- H02J9/04—Circuit 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
- H02J9/06—Circuit 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, e.g. UPS systems
- H02J9/062—Circuit 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, e.g. UPS systems for AC powered loads
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/30—Systems integrating technologies related to power network operation and communication or information technologies for improving the carbon footprint of the management of residential or tertiary loads, i.e. smart grids as climate change mitigation technology in the buildings sector, including also the last stages of power distribution and the control, monitoring or operating management systems at local level
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
- Y02D30/00—Reducing energy consumption in communication networks
- Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
- Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
- Y04S20/00—Management or operation of end-user stationary applications or the last stages of power distribution; Controlling, monitoring or operating thereof
- Y04S20/20—End-user application control systems
Landscapes
- Engineering & Computer Science (AREA)
- Signal Processing (AREA)
- Business, Economics & Management (AREA)
- Emergency Management (AREA)
- Power Engineering (AREA)
- Stand-By Power Supply Arrangements (AREA)
Abstract
ABSTRACT
Standby power supplies for key telephone systems are known which derive 24 VDC, for charging a battery, from commercial power mains, e.g. 117 VAC, and also derive 10 volt AC
for energizing lamps, bells, and the like in the telephone system.
These systems are bulky and expensive. The present invention, which is smaller and less expensive, is normally powered by 10 volt AC from the key telephone system and this 10 volt AC
is fed to a charger which trickle charges the 24 V battery supply. In the event of a commercial power interruption the charger is automatically disconnected from the 10 volt AC and power is derived from the battery supply which drives a 10 volt AC inverter to power the lamps, etc. in the key system.
Standby power supplies for key telephone systems are known which derive 24 VDC, for charging a battery, from commercial power mains, e.g. 117 VAC, and also derive 10 volt AC
for energizing lamps, bells, and the like in the telephone system.
These systems are bulky and expensive. The present invention, which is smaller and less expensive, is normally powered by 10 volt AC from the key telephone system and this 10 volt AC
is fed to a charger which trickle charges the 24 V battery supply. In the event of a commercial power interruption the charger is automatically disconnected from the 10 volt AC and power is derived from the battery supply which drives a 10 volt AC inverter to power the lamps, etc. in the key system.
Description
~:~739~
This invention relates to a power supply for a key telephone system or PABX.
In key telephone systems, it is sometimes considered essential that the system remain functional despite a commercial power interruption. Some known systems use a converter connected to commercial power mains, e.g. 117 VAC to derive 24 volts DC for charging a battery supply and also to derive 10 volt AC for energizing lamps in the system.
In the event of a commercial power interruption, the telephone system is kept operational by the 24 volt battery supply. An inverter steps up the 24 volts from the battery to 117 VAC which, in turn, is stepped down to 10 VAC for energizing lamps in the telephone system.
These prior art systems, which are designed to recharge the batteries quite quickly when the commercial power (typically 117 VAC) is restored, are bulky and expensive.
Inasmuch as commercial power interruptions in many areas tend to be infrequent and of short duration, an object of this invention is to provide a standby powar supply for a key telephone system which is smaller, simpler and less expensive than prior art systems.
The present invention uses a power supply which is normally powered by the 10 volt AC from the key system and this 10 volt AC is fed to a charger which trickle charges a 24V battery supply. In the event of a commercial power interruption, the charger is automatically disconnected from the 10 volt AC and power is derived from the battery supply which drives a 10 volt AC inverter to power the lamps in the -- 1 -- ,.
. . -, , .
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key system. Fail-safe operation is assured by means of a relay which is energized during normal operation but switches over its contacts in the event of a power failure. Various LED's can be provided to indicate normal operation, over voltage, under voltage or power failure.
As the present invention only trickle charges the batteries, losses in the charging circuitry are low and the circuitry is simplified due to elimination of such items as filters on the rectifier output and voltage regulators. The inverter and charger can be of small capacity since only trickle charging is used. Trickle charging is considered sufficient in many localities where commercial power interruptions are infrequent and of short duration, e.g. about 4 hours maximum.
Thus, in accordance with a broad aspect of the invention there is provided a standby power supply for a key telephone system which is normally powered by commercial AC mains, derives therefrom low voltage AC for powering lights, bells, and the like, and has a battery from which power may be derived in the event of a power interruption, said power supply comprising a battery charger, an inverter, and switching means which, during normal operation, connects an input of said charger to said low voltage AC, connects an output of said charger across said battery to thereby supply charging current to said battery, and disconnects said inverter from said battery and said charger, whereas, in the event of an interruption in power from said mains, said switching means interrupts the output of said charger and connects said inverter across said battery, whereby said inverter ` supplies low voltage AC to said key telephone system.
This invention relates to a power supply for a key telephone system or PABX.
In key telephone systems, it is sometimes considered essential that the system remain functional despite a commercial power interruption. Some known systems use a converter connected to commercial power mains, e.g. 117 VAC to derive 24 volts DC for charging a battery supply and also to derive 10 volt AC for energizing lamps in the system.
In the event of a commercial power interruption, the telephone system is kept operational by the 24 volt battery supply. An inverter steps up the 24 volts from the battery to 117 VAC which, in turn, is stepped down to 10 VAC for energizing lamps in the telephone system.
These prior art systems, which are designed to recharge the batteries quite quickly when the commercial power (typically 117 VAC) is restored, are bulky and expensive.
Inasmuch as commercial power interruptions in many areas tend to be infrequent and of short duration, an object of this invention is to provide a standby powar supply for a key telephone system which is smaller, simpler and less expensive than prior art systems.
The present invention uses a power supply which is normally powered by the 10 volt AC from the key system and this 10 volt AC is fed to a charger which trickle charges a 24V battery supply. In the event of a commercial power interruption, the charger is automatically disconnected from the 10 volt AC and power is derived from the battery supply which drives a 10 volt AC inverter to power the lamps in the -- 1 -- ,.
. . -, , .
.; -73~
key system. Fail-safe operation is assured by means of a relay which is energized during normal operation but switches over its contacts in the event of a power failure. Various LED's can be provided to indicate normal operation, over voltage, under voltage or power failure.
As the present invention only trickle charges the batteries, losses in the charging circuitry are low and the circuitry is simplified due to elimination of such items as filters on the rectifier output and voltage regulators. The inverter and charger can be of small capacity since only trickle charging is used. Trickle charging is considered sufficient in many localities where commercial power interruptions are infrequent and of short duration, e.g. about 4 hours maximum.
Thus, in accordance with a broad aspect of the invention there is provided a standby power supply for a key telephone system which is normally powered by commercial AC mains, derives therefrom low voltage AC for powering lights, bells, and the like, and has a battery from which power may be derived in the event of a power interruption, said power supply comprising a battery charger, an inverter, and switching means which, during normal operation, connects an input of said charger to said low voltage AC, connects an output of said charger across said battery to thereby supply charging current to said battery, and disconnects said inverter from said battery and said charger, whereas, in the event of an interruption in power from said mains, said switching means interrupts the output of said charger and connects said inverter across said battery, whereby said inverter ` supplies low voltage AC to said key telephone system.
- 2 -, ~ .
~17;39~
The invention will now be further described in ; conjunction with the accompanying drawings, in which:
Figure 1 is a partly block, partly schematic, diagram of a standby power unit according to the invention, and Figures 2 and 3, which fit together as shown by Figure 4, are a detailed circuit diagram of the standby power unit according to the invention.
Referring to Figure 1, the standby power unit 10 includes a charger 12 which, under normal working conditions when power is available from a commercial mains supply, derives its power from the 10 VAC output of a conventional, key telephone system (not shown) connected to terminals 3 and 4 of terminal board TB 1. The 10 VAC input at terminals 3 and 4 causes relay Kl to be energized so that it opens its contacts K12, K14 and K16 while it closes its contacts Rll, K13 and K15. Closure of contacts K15 results in connection of the charger 12 to the terminals 6 and 8 of TBl. Charger 1 thus provides a trickle charge to a 24 volt battery, not shown, via terminals 6 and 8.
At this time, no power is supplied by charger 12 to the inverter 14 because contacts K16 are open. Similarly, there is no connection to terminal 5 of TB 1 because contacts K14 are open.
Should the commercial power supply fail, the ten volt AC
applied to terminals 3 and 4 from the key telephone system will disappear and AC relay Kl will release and switch its contacts to the conditions shown in Figure 1. The output of the charger 12 is now disconnected because of the opening of contacts K15 but the 24 volt battery connected to terminals 6 and 8 ~ .
.. . . .
- ' ' .~. , li739ยข?Z
of TB 1 is connected to the 10 volt AC inverter 14 because of the closure of contacts K16. The inverter 14 now supplies 10 volt AC power to the key telephone system via terminals 1 and 2 of TB 1 through closed contacts K12 of relay Kl. The operation of the inverter may be indicated by an LED 15 connected across its output through a resistor 16 and an anti-parallel diode 17 which provides reverse bias protection.
It will be noted that a commercial power supply failure can be simulated by pressing a test switch 20 in series with relay Kl. Opening of test switch 20 interrupts the current to relay Kl which releases its contacts in the same manner as if a power failure had occurred.
Battery operation is continuously monitored by voltage monitor and alarm circuit 25. Provision is made for visible alarm indications either locally and/or remotely for low/ high or no battery conditions. This is accomplished by voltage monitor and alarm circuit 25 activating, over line 26, a relay driver 27 which drives a relay K2 having contacts K21 to K24 connected to a terminal board TB2 as shown at the upper right of Figure 1.
~ The power failure sensing relay Kl also provides the power transfer function, from mains to battery, as will be evident from the preceding description. The power failure sensing relay Kl and alarm relay K2 are operated in a fail-safe mode to provide immediate indication of relay failure.
The charger 12 and inverter 14 preferably incorporate self-limiting current functions for protection against short circuit conditions.
The strap 30 between terminals 2 and 3 of TB 1 is used ~739~
to provide direct charging from the key telephone installation but, if a separate 10 VAC source is used for charging, the strap 30 is removed and the separate source is connected to terminals 3 and 4 of terminal board TB 1.
Terminal 7 of TB 1 allows connections to primary -24V
plants that cannot tolerate back feed voltage conditions.
This connection isolates the power supply from the battery source.
The power unit preferably incorporates fuses Fl and F2 for protection.
Referring now to Figures 2 and 3, it is assumed that, for normal operation, 10 volts AC is applied from the key system to terminals 3 and 4, thus energizing relay Kl and applying power to the primary of transformer T3. A rectifier bridge 30 is connected to the secondary of transformer T3 and capacitors C8 and C9 provide filtering. The voltage across capacitors C8 and C9 is applied to a constant voltage, current limited, regulator IC2 which derives a reference voltage across resistors R20 and R22, R22 being adjustable to set the charger output voltage level.
Diode CR14 provides reverse voltage protection for the input of regulator IC2 and diode CR15 provides reverse voltage protection for the output. Filter Cll is a filter capacitor.
During normal operation, contacts K15 are closed, thus connecting the negative output terminal of the charger to terminal 8 of TBl. Thus, the charger supplies a trickle charge to the battery (not shown) connected across terminals 6 and 8 of TBl.
At the same time, however, contacts K14 are open, so that no 24 VDC
signal is supplied by the charger to terminals 5 and 6. Of course, contacts K13 are closed at this time so that the battery is ~; .
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connected across terminals 5 and 6 to provide 24 VDC to the key telephone system.
If there is a power interruption, the 10 volt AC signal across terminals 3 and 4 disappears and relay Kl releases. This opens contacts K15, disconnecting the charger. Contacts K16 close, however, to connect negative battery from terminal 8 of TBl to the inverter generally indicated at 14 (Figure 3). Positive battery is already supplied from terminal 6 of TBl.
The inverter circuit 14 comprises a square wave oscillator IC3 and associated external resistors and capacitors. For example, resistors R23 and R24 and capacitor C13 comprise a timing network for the square wave oscillator IC3. CR16 is a zener diode rated at 12 volts to supply voltage to IC3 and C12 is a DC filter capacitor. The output of IC3 is fed to an inverter IC5 which, in turn, feeds a frequency divider IC4. The output of IC4 comprises pulses which are fed via inverters 40, 41 and 42, resistors R25 and R26 to the bases of transistors Q5 and Q4. The signal applied to the base of Q4 is opposite in phase -to that applied to the base of Q5 because of the two inverters 41 and 42 vs the single inverter 40 connected to the base of Q5. Transistors Q5 and Q4 drive the primary of a transformer T2.
C15 and C16 and associated resistors R25 and R26 comprise a CR network to slow the rise and decay times of the pulses applied to the bases of driver transistors Q4 and Q5. Diodes CRl8 and CRl7 provide reverse voltage protection for the transistors Q4 and Q5. Capacitor C5 and resistor R17 comprise a "snubber"
network to prevent overshoot on turn on or turn off of Q4 and Q5.
Capacitor C6 connected across the secondary of transformer T2 ,. . ,, . ~, . , ~:1739~'2 creates a resonating circuit, the output of which drives transistors Q2 and Q3. When Q2 is on, Q3 is off and vice versa.
Capacitor C7 and resistor R18, connected between the collectors of Q2 and Q3 comprises a further "snubber" network to prevent overshoot on turn on or turn off of Q2 and Q3. The transistors Q2 and Q3 alternately conduct through the top and bottom halves, respectively, of the primary of transformer Tl and the secondary of Tl feeds 10 volts AC to output terminals 1 and 2 of TBl, it being recalled that contacts K12 are closed at this time.
The voltage monitor and alarm circuitry 25 is shown in Figure 3. Reverse voltage protection is provided by diode CR20 and a 15 volt reference voltage is provided by zener diode CRl in series with resistor Rl. Cl, C2 and C3 are AC bypass capacitors.
The variable tap ~0 on resistor R9, in series with R8 and R10, provides a reference voltage for one input of each of comparators 51, 52 and 53. One input of comparator 50 is derived from the junction between resistors R29 and R31 while the other is derived from the junction between resistors R28 and R30. If there is a battery fault, the output of comparator 50 goes low ~0 causing diode CRl9 to conduct which, in turn, turns on comparator 53. Conduction of comparator 53 turns off transistor Ql which releases alarm relay K2 to indicate a battery fault via the contacts on TB2.
A low voltage results in comparator 51 going low, which causes LED CR5 to conduct and emit a visible indication .~
of low voltage A high voltage causes comparator 52 to go low which ~` drives LED CR6. Comparators 51 and 52 going low cause diodes CR3 , 39~Z
and CR2, respectively, to conduct which again, via comparator 53 and transistor Ql, activates relay K2.
Diode CR4 is a reverse voltage diode protection for . transistor Ql.
During normal operation, transistor Ql conducts through LED CR7 which provides a visible indication of normal operation, and through relay K2 which switches its contacts (TB2)~
. ~
``:
' . , : .
~17;39~
The invention will now be further described in ; conjunction with the accompanying drawings, in which:
Figure 1 is a partly block, partly schematic, diagram of a standby power unit according to the invention, and Figures 2 and 3, which fit together as shown by Figure 4, are a detailed circuit diagram of the standby power unit according to the invention.
Referring to Figure 1, the standby power unit 10 includes a charger 12 which, under normal working conditions when power is available from a commercial mains supply, derives its power from the 10 VAC output of a conventional, key telephone system (not shown) connected to terminals 3 and 4 of terminal board TB 1. The 10 VAC input at terminals 3 and 4 causes relay Kl to be energized so that it opens its contacts K12, K14 and K16 while it closes its contacts Rll, K13 and K15. Closure of contacts K15 results in connection of the charger 12 to the terminals 6 and 8 of TBl. Charger 1 thus provides a trickle charge to a 24 volt battery, not shown, via terminals 6 and 8.
At this time, no power is supplied by charger 12 to the inverter 14 because contacts K16 are open. Similarly, there is no connection to terminal 5 of TB 1 because contacts K14 are open.
Should the commercial power supply fail, the ten volt AC
applied to terminals 3 and 4 from the key telephone system will disappear and AC relay Kl will release and switch its contacts to the conditions shown in Figure 1. The output of the charger 12 is now disconnected because of the opening of contacts K15 but the 24 volt battery connected to terminals 6 and 8 ~ .
.. . . .
- ' ' .~. , li739ยข?Z
of TB 1 is connected to the 10 volt AC inverter 14 because of the closure of contacts K16. The inverter 14 now supplies 10 volt AC power to the key telephone system via terminals 1 and 2 of TB 1 through closed contacts K12 of relay Kl. The operation of the inverter may be indicated by an LED 15 connected across its output through a resistor 16 and an anti-parallel diode 17 which provides reverse bias protection.
It will be noted that a commercial power supply failure can be simulated by pressing a test switch 20 in series with relay Kl. Opening of test switch 20 interrupts the current to relay Kl which releases its contacts in the same manner as if a power failure had occurred.
Battery operation is continuously monitored by voltage monitor and alarm circuit 25. Provision is made for visible alarm indications either locally and/or remotely for low/ high or no battery conditions. This is accomplished by voltage monitor and alarm circuit 25 activating, over line 26, a relay driver 27 which drives a relay K2 having contacts K21 to K24 connected to a terminal board TB2 as shown at the upper right of Figure 1.
~ The power failure sensing relay Kl also provides the power transfer function, from mains to battery, as will be evident from the preceding description. The power failure sensing relay Kl and alarm relay K2 are operated in a fail-safe mode to provide immediate indication of relay failure.
The charger 12 and inverter 14 preferably incorporate self-limiting current functions for protection against short circuit conditions.
The strap 30 between terminals 2 and 3 of TB 1 is used ~739~
to provide direct charging from the key telephone installation but, if a separate 10 VAC source is used for charging, the strap 30 is removed and the separate source is connected to terminals 3 and 4 of terminal board TB 1.
Terminal 7 of TB 1 allows connections to primary -24V
plants that cannot tolerate back feed voltage conditions.
This connection isolates the power supply from the battery source.
The power unit preferably incorporates fuses Fl and F2 for protection.
Referring now to Figures 2 and 3, it is assumed that, for normal operation, 10 volts AC is applied from the key system to terminals 3 and 4, thus energizing relay Kl and applying power to the primary of transformer T3. A rectifier bridge 30 is connected to the secondary of transformer T3 and capacitors C8 and C9 provide filtering. The voltage across capacitors C8 and C9 is applied to a constant voltage, current limited, regulator IC2 which derives a reference voltage across resistors R20 and R22, R22 being adjustable to set the charger output voltage level.
Diode CR14 provides reverse voltage protection for the input of regulator IC2 and diode CR15 provides reverse voltage protection for the output. Filter Cll is a filter capacitor.
During normal operation, contacts K15 are closed, thus connecting the negative output terminal of the charger to terminal 8 of TBl. Thus, the charger supplies a trickle charge to the battery (not shown) connected across terminals 6 and 8 of TBl.
At the same time, however, contacts K14 are open, so that no 24 VDC
signal is supplied by the charger to terminals 5 and 6. Of course, contacts K13 are closed at this time so that the battery is ~; .
~73~
connected across terminals 5 and 6 to provide 24 VDC to the key telephone system.
If there is a power interruption, the 10 volt AC signal across terminals 3 and 4 disappears and relay Kl releases. This opens contacts K15, disconnecting the charger. Contacts K16 close, however, to connect negative battery from terminal 8 of TBl to the inverter generally indicated at 14 (Figure 3). Positive battery is already supplied from terminal 6 of TBl.
The inverter circuit 14 comprises a square wave oscillator IC3 and associated external resistors and capacitors. For example, resistors R23 and R24 and capacitor C13 comprise a timing network for the square wave oscillator IC3. CR16 is a zener diode rated at 12 volts to supply voltage to IC3 and C12 is a DC filter capacitor. The output of IC3 is fed to an inverter IC5 which, in turn, feeds a frequency divider IC4. The output of IC4 comprises pulses which are fed via inverters 40, 41 and 42, resistors R25 and R26 to the bases of transistors Q5 and Q4. The signal applied to the base of Q4 is opposite in phase -to that applied to the base of Q5 because of the two inverters 41 and 42 vs the single inverter 40 connected to the base of Q5. Transistors Q5 and Q4 drive the primary of a transformer T2.
C15 and C16 and associated resistors R25 and R26 comprise a CR network to slow the rise and decay times of the pulses applied to the bases of driver transistors Q4 and Q5. Diodes CRl8 and CRl7 provide reverse voltage protection for the transistors Q4 and Q5. Capacitor C5 and resistor R17 comprise a "snubber"
network to prevent overshoot on turn on or turn off of Q4 and Q5.
Capacitor C6 connected across the secondary of transformer T2 ,. . ,, . ~, . , ~:1739~'2 creates a resonating circuit, the output of which drives transistors Q2 and Q3. When Q2 is on, Q3 is off and vice versa.
Capacitor C7 and resistor R18, connected between the collectors of Q2 and Q3 comprises a further "snubber" network to prevent overshoot on turn on or turn off of Q2 and Q3. The transistors Q2 and Q3 alternately conduct through the top and bottom halves, respectively, of the primary of transformer Tl and the secondary of Tl feeds 10 volts AC to output terminals 1 and 2 of TBl, it being recalled that contacts K12 are closed at this time.
The voltage monitor and alarm circuitry 25 is shown in Figure 3. Reverse voltage protection is provided by diode CR20 and a 15 volt reference voltage is provided by zener diode CRl in series with resistor Rl. Cl, C2 and C3 are AC bypass capacitors.
The variable tap ~0 on resistor R9, in series with R8 and R10, provides a reference voltage for one input of each of comparators 51, 52 and 53. One input of comparator 50 is derived from the junction between resistors R29 and R31 while the other is derived from the junction between resistors R28 and R30. If there is a battery fault, the output of comparator 50 goes low ~0 causing diode CRl9 to conduct which, in turn, turns on comparator 53. Conduction of comparator 53 turns off transistor Ql which releases alarm relay K2 to indicate a battery fault via the contacts on TB2.
A low voltage results in comparator 51 going low, which causes LED CR5 to conduct and emit a visible indication .~
of low voltage A high voltage causes comparator 52 to go low which ~` drives LED CR6. Comparators 51 and 52 going low cause diodes CR3 , 39~Z
and CR2, respectively, to conduct which again, via comparator 53 and transistor Ql, activates relay K2.
Diode CR4 is a reverse voltage diode protection for . transistor Ql.
During normal operation, transistor Ql conducts through LED CR7 which provides a visible indication of normal operation, and through relay K2 which switches its contacts (TB2)~
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Claims (5)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A standby power supply for a key telephone system which is normally powered by commercial AC mains, derives therefrom low voltage AC for powering lights, bells, and the like, and has a battery from which power may be derived in the even-t of a mains power interruption, said power supply comprising a battery charger, an inverter, and switching means which, during normal operation, connects an input of said charger to said low voltage AC, connects an output of said charger across said battery to thereby supply charging current to said battery, and disconnects said inverter from said battery and said charger, whereas, in the event of an interruption in power from said mains, said switching means interrupts the output of said charger and connects said inverter across said battery, whereby said inverter supplies low voltage AC to said key telephone system.
2. A power supply as claimed in claim 1 wherein said switching means comprises an AC relay adapted to be energized by low voltage AC from said key telephone system.
3. A power supply as claimed in claim 2 including means for monitoring overvoltage and undervoltage conditions and providing alarm indications in the event of over or under voltage.
4. A power supply as claimed in claim 3 including a test button in series with said relay, said test button having normally closed contacts whereby pushing said test button interrupts current to the relay to simulate an interruption of power from the mains.
q
q
5. A power supply as claimed in claim 4 including means for indicating operation of said inverter and hence indicating an interruption of power from the mains.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000399682A CA1173902A (en) | 1982-03-29 | 1982-03-29 | Standby power unit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000399682A CA1173902A (en) | 1982-03-29 | 1982-03-29 | Standby power unit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1173902A true CA1173902A (en) | 1984-09-04 |
Family
ID=4122437
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000399682A Expired CA1173902A (en) | 1982-03-29 | 1982-03-29 | Standby power unit |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1173902A (en) |
-
1982
- 1982-03-29 CA CA000399682A patent/CA1173902A/en not_active Expired
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