GB2190551A

GB2190551A - Standby power supply

Info

Publication number: GB2190551A
Application number: GB08611105A
Authority: GB
Inventors: Ka Duk Lam
Original assignee: Sealand Ind Co Ltd
Current assignee: Sealand Ind Co Ltd
Priority date: 1986-05-07
Filing date: 1986-05-07
Publication date: 1987-11-18
Also published as: GB8611105D0

Abstract

In a power supply for an air pump 5, mains electricity 1 is normally supplied to the pump 5 through a relay-operated changeover switch 3, and also charges up an emergency battery 11, through transformer 7 and rectifier 9. If the mains supply 1 fails, switch 3 changes state and a DC/AC inverter 15 powered by the battery 11 then drives the pump. The output of the rectifier 9 also provides a control signal to operate both the relay switch 3 and a second relay-switch 13 between the battery 11 and inverter 15. <IMAGE>

Description

SPECIFICATION Power supply apparatus The present invention relates to a power supply arrangement for use with a mains source of AC and a back-up source of current, more particularly for a powersupplyarrangementforan air pump for use with a mains source of AC and a back-up source of current.

At present most power supply arrangements for use with air pumps and the like comprise two different systems, a mains AC power supply system and a power supply system driven by a source of DC such as a battery.

The AC power supply system comprises a input of 240V of AC, normallyfrom a mains source, which input is fed by way of a solenoid to two air pumps, thereby driving the air pumps.

The alternative system comprises the use of a dry battery to feed direct current into a motorwhich drives a single air pump. Two orfour dry batterys are normally used.

The major disadvantage of the current power supply systems is that they are not interchangeable, that is DC power supply systems can only work on DC from a dry battery, to supply a motor, while AC power supply systems only workwith AC power, usually from a mains AC source, to supply air pumps directly. Furthermore the DC power supply system drives only one air pump, and the battery has to be replaced atregularintervals.

According to the present invention there is provided a power supply arrangement for an electrically operable apparatus, the power supply arrangement comprising a first alternating current supply, means capable to connectthefirst alternating current supply to the electrically operable apparatus, a second alternating current supply, means to sense a lack of current from the first alternating current supply and adapted to control the means capable of connecting the first alternating current supply to the apparatus, to disconnectthe first alternating current supply from, and to connect the second alternatig currentsupplyto,the electrically operable apparatus.

Preferably the first alternating current supply is a mains electricity source.

Preferably, the second alternating current supply comprises a battery and a direct currentto alternating current converter, to convert the direct current produced by the battery to alternating currentfor use by the electrically operable apparatus. More preferably the battery is rechargeable, and most preferably the battery may be recharged by means of a connection between the battery and a mains electricity supply,which connection may be by way of a transformer, to alter the voltage appropriately, and a rectifier, to convert the alternating currentfrom the mains to direct current,with which to recharge the battery.

Preferably the means capable of connecting the first alternating current supply to the electrically operable apparatus and the means to sense a lack of current in the first alternating current supply, and adapted to control said connecting means, to disconnect said first alternating currentsupplyfrom, and connect the second alternating current supply to, the apparatus, are combined in at least one solenoid switch. More preferably the solenoid switch is a relay from a rectifier which feeds current into a rechargeable battery.

In orderthatthe present invention may be more readily understood and so thatfurtherfeatures thereof may be appreciated, the invention will now be described by way of example, with reference to the accompanying drawings in which: Figure 7 is a block diagram of one embodiment of a power supply arrangement according to the present invention; Figure2 is a circuit diagram ofthe DC to AC convertershown in Figure 1; and Figure 3 is a circuit diagram of the transformer, rectifier and relay as shown in Figure 1.

Referring now to the drawings Figure 1 shows a blockdiagram of a powersupplyarrangement according to the present invention 1. A mains AC source 1 is normally connected through a switch 3, which is constituted by a solenoid switch, to an air pump 5. The mains source 1 is also connected, by way of a transformer 7 and a rectifier 9 to a rechargeable battery 11. The rechargeable battery 11 may be connected through a normally open switch, constituted by a second solenoid 13 to a DC/AC converter 15. The output of the DC/AC converter 15 is connected to a second terminal ofthe first solenoid switch 3 so that when this solenoid switch moves from its normal position, the output of the DC/AC converter 15 is connected to drive the pump 5.

A lead 17 extends from the output of the rectifier9 to the control terminals of each of the solenoid switches 3 and 13 to provide power to retain those solenoid switches in their normal conditions whenever mains power is present at the mains source 1.

In normal use the alternating current flow is fed from the mains sourcel throughthefirstsolenoid switch 3 to the pump 5. The alternating current is also fed from the mains AC source 1 through the transformer7, which converts the 240V alternating currentto 1 2V alternating current. The output of the transformer7 is supplied to the rectifier 9, which converts the 12VAC current into 5V DC current,the resulting DC current being fed into the rechargeable battery 11. Thus, in normal operation, the battery is fully charged up. The DC current from the rectifier 9 also passes byway of the lead 17, from the rectifier9 to the control terminals of the solenoids 3 and 13.

When the AC current is being fed from the mains AC source 1 the solenoid switch 3 is actuated to connect the mains source 1 with the pump 5, and the solenoid switch 13 is actuated to break the connection between the rechargeable battery 11 and the DC/AC converter 15.

When the current from the mains supply 1 is interrupted in any way, current ceases to flow through the transformer 7, and the rectifier 9. Thus, no current passes through the lead 17, to the control terminals of the two solenoid switches 3 and 13. The cessation of current causes the first solenoid 3 to switch to a second position wherein it disconnects the main AC source 1 from the pump 5, and connects the DC/AC converter 15 to the pump 5. The solenoid switch 13 also changes position on the cessation of currentflowto connect the rechargeable battery 11 with the DC/AC converter 15.

In this way, when AC currentflowsfrom mains source 1 itserves to drive the pump 5. The current also passes via the transformer7 and rectifier9,to the rechargeable battery 11, thereby charging the battery 11. The DC current from the rectifierfurther serves to hold the first solenoid switch 3 in a position wherebythe mains AC source 1 is connected to the pump 5, thereby ensuring that cu rrentflows from the mains AC source 1 to the pump 5 and prevents any connection between DC/AC converter 15 and the pump 5.The second solenoid switch 13 is held open, thereby preventing any currentflowing from the battery 11 to the DC/AC converter 1Sthus allowing the battery 11 to be charged by DC currentfed from the rectifier 9 without any charge being lostfrom the battery 11 to the DC/AC converter 15.

When current ceases to be fed from the mains AC source 1 thetwosolenoidswitch3and 13 are actuated, the second solenoid switch 13 connects the rechargeable battery 11 with the DC/AC converter 15 allowing currentto flow from the battery 11 to the converter 15, and the first solenoid switch 3 breaks the connection between the mains source 1 and the pump 5, and makes the connection between the DC/AC converter 15 and the pump 5.

In thiswaywhen the mains AC source 1 is operating, it serves to drive the pump 5 and charge the battery 11 atthe sametime, and, as soon as the current ceases to be fed from the mains AC source 1, the operation of the solenoid switches 3 and 13 cause the rechargeable battery to be connected viathe DC/AC converter 15 to the pump 5,therefore allowing the pump 5to be driven bythe battery 11. In this way there is little or no interruption in the working ofthe pump 5, and the battery 11 is kept charged at all times whilst the mains source 1 is operational.

When the mains AC source 1 operates again, currentflows from the rectifier 9 to the solenoid switches 3, 13 switching the circuit backto its initial state. The battery 11 is then re-charged by the direct currentflowing from the rectifier 9.

Figure 2 shows a AC/DC convertercircuitwhich may be used in the present invention. It is a standard circuit, and any standard AC/DC converter can be used.

Figure 3 shows the circuit diagram of a transformer 7, rectifier 9, and relay 17 as used in Figure 1. The transformer is a standard step-down transformerfrom220Vto 12V,comprising afirst winding 19, the first winding 19 being fed from the mains source 1, and a second winding 21. The second winding 21 of transformer 7 is connected to the rectifier 9. The windings are on a common core.

The rectifier 9 comprises a first diode 23 (500mA, IN4001) connected in series with the winding 21 to maintain the current flow in a single direction, therebyto convert the AC to DC. In parallel with the winding 21 and the first diode 23 is positioned a capacitor 25 (100mf, 16V) which "smooths out" the pulsed direct current being emitted from the first diode 23. In parallel with the capacitor 25 is a red light emitting diode 27, and a first resistor 29 (1 OK). The light emitting diode 29 is used to indicate thatthe rectifier9 is in use. Between the capacitor andthe rechargeable battery 11 is a second diode 31 (IN4001) and a second resistor 33 (33Q,2W) to further "smooth" the current. The lead 17 is connected to the terminals ofthe capacitor 25.

Claims

1. A power supply arrangement for an electrically operable apparatus, the power supply arrangement comprising a first alternating current supply, means capable to connectthe first alternating current supplytothe electrically operable apparatus, a second alternating current supply, means to sense a lack of current from the first alternating current supply and adapted to control the means capable of connecting the first alternating current supply to the apparatus, to disconnect the first alternating current supply from, and to connect the second alternating current supplyto, the electrically operable apparatus.

2. A power supply arrangement according to Claim 1, wherein the first alternating current supply is a mains electricity source.

3. Apowersupply arrangement according to either of Claims 1 or 2, wherein the second alternating current supply comprises a battery and a direct current to alternating current converter.

4. A power supply arrangement according to Claim 3, wherein the battery is rechargeable.

5. A power supply arrangement according to Claim 4, wherein the arrangement is adapted to recharge the batteryfrom the first alternating current supply.

6. A power supply arrangement according to Claim 5, wherein the alternating current is passed through a transformer and a rectifier before recharging the battery.

7. A power supply arrangement according to any ofthe preceding claims, wherein said connection means comprise a controllable switch to connect either the first or the second current supply to said apparatus.

8. A powersupply arrangement according to Claim 7, wherein said controllable switch is operated in response to a signal derived from said first supply.

9. A power supply arrangement according to Claim 8, wherein said signal is a DC signal obtained from said first supply by rectification.

10. A power supply arrangement according to Claim 9, wherein said controllable switch is a solenoid switch.

11. A power supply arrangement according to any one of the preceding claims, wherein said second supply is activated only when the second supply is connected to the said apparatus.

12. Apowersupplyarrangementaccordingto Claim 3, or any of Claims 4to 10 dependentthereon, wherein a second controllable switch connects the battery to the direct cu rrent to alternating current converter when the second supply is connected to said apparatus.

13. A power supply arrangement according to Claim 12, wherein said second controllable switch is operated in response to a DC signal obtained from said first supply by rectification.

14. A power supply arrangement according to Claim 9 or Claim 13 as dependent on Claim 6, wherein the or each DC signal is derived fromthe said transformer and rectifier.

15. A power supply arrangement according to any one of the preceding claims, wherein said electrically operable apparatus comprises at least one air pump.

16. A power supply arrangement substantially as hereinbefore described with reference to, and as described in, the accompanying drawings.

17. An air pump comprising a powersupply arrangement substantially as hereinbefore described with reference to, and as described in, the accompanying drawings.

18. Any novel feature or combination of features described herein.