RECHARGEABLE BACK-UP BATTERY DEVICE

TECHNICAL FIELD

The present invention relates to a rechargeable back-up battery device for an electronic device such as a cellular telephone, a Personal Digital Assistant (PDA), portable PC, camera or any other electronic device comprising a contact connected to a rechargeable battery via a control circuit.

BACKGROUND OF THE INVENTION

It is an indisputable fact that even though electronic devices are presently supplied with relatively good rechargeable batteries with a long usage time and a long operative waiting time (so-called stand-by time), it is still a common experience to run out of battery capacity. In this case the solution is either to carry a spare battery or to find a suitable place to charge the battery, which in turn depends on having a battery charger available and being in the vicinity of an electric contact point with suitable voltage, etc. In many situations it is impractical to carry a spare battery or charger, in addition to which in many situations it will be necessary to e.g. reestablish the connection via cellular telephone immediately, for example in emergency situations or during important conversations, which are interrupted on account of deficient battery capacity.

A back-up battery device suitable for recharging the batteries of electronic devices are disclosed in US 6,709,784, which hereby is incorporated by reference in its entirety.

Amongst previously known solutions, mention may be made of various generally known solutions, which "ration" a part of the battery capacity for an emergency situation. However, this does not cover the need for a general increase in battery capacity when the situation has reached the stage when the user has a depleted battery and still needs an operative electronic device. It is also known to connect an external battery (spare battery) to a suitable device with an electronic circuit, which spare battery gives the electronic device additional operative time through increased battery capacity. The solution is illustrated, amongst other places, in U.S. Pat. No. 5,977,747. The solution will be expensive, involving a connection point and an electronic circuit, which in addition will always have to be available. In the solution in the present invention, the object is to avoid this by providing a universal solution, which employs the electronic device's own control, thus avoiding the need for any extra equipment apart from only the back-up battery, which can then be purchased anywhere and employed immediately.

In U.S. Pat. No. 5,786,106, moreover, a solution is disclosed where different electrical devices such as a torch or the like can be connected to a cellular telephone battery through suitable connection points. In this case it will also be possible to connect the cellular telephone battery to an additional battery in parallel connection. The disadvantage, of course, is that the connected battery has to be specially adapted to the cellular telephone's battery with regard to voltage level, etc., which in turn makes the solution inflexible. Moreover, an electronic control circuit for the connection is preferable. Another type of battery use system for portable electric equipment comprising a switch control circuit is shown in EP 0 657 982.

It shall be noted that cellular phones comprises an inboard control circuit between the charger contact and the rechargeable battery. The inboard control circuit controls the voltage level and/or current level to protect the battery from damaging overvoltages or other voltage/current levels that may deteriorate its operating life. In Wireless Week, the December 2000 issue, it was described an instant power charger for a cell phone which can be recharged by means of a battery charger. No back-up battery is mentioned or shown and no control circuit is described. The same product is mentioned in article by Yardena Arar in PCWorld, dated November 15. 2000. The article describes a battery which draws oxygen from the atmosphere to generate electrical power. The battery is available for mobile phones and can be recharged by means of a recharging kit.

On www.zentecom.com it is described a rechargeable portable cellular charger comprising a battery and a cable for connecting the battery to the cell phone.

In US 5,200,688 it is shown a vehicular battery operated charger for charging an electronic device such as a radio. The charger and its control circuit is rather complex and consequently costly. Further, the charger is directly connected to the rechargeable radio battery for charging.

In US 5,568,038 it is shown a battery use system for a battery-driven portable electronic device comprising a first chargeable battery and a second battery connected in parallel to the first battery through a switch. The switch is closed to charge the first battery by the second battery when the output voltage from the first battery becomes smaller than a predetermined value, i.e. a voltage drop occurs.

In GB 2 249 677 it is shown a battery charger for a mobile apparatus comprising a battery charged from a vehicle battery. A timer is supplied by the voltage of the outside battery via a diode and sets a charging time. In order to prevent the battery from being overcharged, for example because the timer is reset when the starter motor reduces the voltage of the electrical system temporally, the timer is arranged

to be powered from the battery via a transistor during such temporal voltage reductions.

In US 5,396,162 it is shown a portable battery charger for rechargeable battery powered appliances comprising a housing, batteries that is inserted into the housing, connection means for connecting the poles of the batteries to the poles of the direct current power system of the battery powered appliance. There is no circuitry to control or adjust the output voltage to the battery powered appliance.

In EP 0 907 234 A2 it is shown a battery charging system where a charging battery comprising a number of n+ m cells is charging a working battery comprising a number of n cells. It shall be noted that the charging battery is directly connected to the working battery.

In WO 00/69013 it is shown a rechargeable battery pack suitable for cellular phones or other electronic devices, comprising at least one rechargeable cell, at least one primary cell (typical a conventional battery of size AAA) and a rechargeable cell recharger including a voltage converter. The voltage converter receives an output voltage from the primary cell and converts it to a second voltage suitable for recharging the rechargeable cell. A disadvantage here is that the voltage converter is rather complex and expensive. Further, the primary cell must be replaced when emptied, which may cause unnecessary consumption of such batteries. Of course there exist rechargeable batteries of conventional sizes, but then yet another recharger is needed.

Thus it is an object of the rechargeable back-up battery device according to the present invention to provide a solution which gives an electronic device extra battery capacity in a simple manner. It is a further object that the solution should be small, reasonably priced, and easy to use and designed in such a manner that a user can employ the back-up battery device intuitively. Of course, the rechargeable backup battery device should give output voltage/current values adapted to the threshold values of the inboard control device of the electronic device.

Further, it is an object of the invention that the rechargeable back-up battery device can be recharged using the charger of the electronic device. It is an object of the invention that such a charger can recharge both the rechargeable back-up battery device and the rechargeable battery of the electronic device at the same time. Preferably another type of charger type can be used, such as an USB-cable connected to a computer, a cable connected to the cigarette lighter socket in a car etc.

SUMMARY OF THE INVENTION

The invention is defined in the enclosed claims. Preferred embodiments of the invention are defined in the dependent claims.

DETAILED DESCRIPTION An exemplified embodiment according to the present invention is further described with reference to the attached drawings, where:

Fig. 1 is a perspective view of a cellular telephone with a rechargeable back-up battery device according to the invention;

Fig. 2 is an illustration of the different components of the embodiment in fig. 1.

Fig. 1 illustrates a cellular telephone 1 with a rechargeable battery, which cellular telephone 1 comprises a contact 2 for connecting to a battery charger. An inboard control circuit (not shown) is connected between the contact 2 and the rechargeable battery. The main purpose of the inboard control circuit of the cellular telephone 1 is to protect the rechargeable battery and to provide a desired voltage and/or current to the rechargeable battery. Therefore, the inboard control circuit controls whether the voltage and/or current supplied by the charger is within certain acceptable boundaries. In the present embodiment the inbound control circuit defines a lower threshold value and an upper threshold value for the input voltage of the contact 2. If the output voltage of the charger is below the lower threshold value or above the upper threshold value, no charging of the battery will occur.

Fig. 1 further illustrates a rechargeable back-up battery device 3 according to the invention. The rechargeable back-up battery device 3 comprises a plug 4 adapted to be connected to the contact 2 of the cellular telephone 1. Further, the rechargeable back-up battery device 3 comprises a first contact 5 and preferably also a second contact 6, both contacts being adapted to be connected to a charger (not shown).

The first contact 5 is corresponding to the contact 2 of the cellular telephone 1. Consequently, the original charger belonging to the telephone 1 can be used also to charge the rechargeable back-up battery device 3. The second contact 6 is adapted to a second type of charger or power source, for example an USB-cable (USB: Universal Serial Bus) connected to a computer (a 5.5 V DC voltage). Alternatively

the second contact 6 is adapted to a cigarette lighter socket of a car (a 12 V DC voltage).

It is of course possible to provide the device 3 with only one contact 5, and then use an adapter/wire for connection to different power sources, such as the original telephone charger, the USB cable or the cable to the cigarette lighter socket. The adapter/wire may also comprise a transformer to transform the input voltage of the device 3 to the desired voltage level.

The rechargeable back-up battery device 3 will now be described with reference to fig. 2, where it is shown that the rechargeable back-up battery device 3 comprises a rechargeable battery 8 and a control circuit 7.

The rechargeable battery 8 comprises one or more rechargeable battery cells and is connected between the plug 4 and the control device 7. The rechargeable battery 8 can be of any rechargeable type which is currently available. However, it will be advantageous to employ one or more small battery cells in order that the total back- up battery should be small in size and of the desired shape. The batteries or cells can be connected in parallel or in serial in order to obtain increased capacity or increased voltage respectively between the terminals of the rechargeable battery 8.

The control circuit 7 is further connected to the first connector 5 and the second connector 6. The control circuit 7 is preferably also connected to a LED indicator 9 (LED: Light Emitting Diode). The control circuit 7 performs the following operations:

- When a fully charged rechargeable back-up battery device 3 becomes connected to the cellular telephone 1 having an empty or almost empty battery, the rechargeable battery 8 will instantly start charging the empty battery provided that the output voltage of the plug 4 is within the boundaries of the inbound control device of the cellular telephone 1. Consequently, a current sensing element of the control circuit 7 is sensing a current, which indicates a charging operation. Preferably, the LED indicator 9 is switched ON to indicate the charging operation. - When the battery voltage of the cellular telephone 1 is approximately equal to the voltage of the rechargeable battery 8, the battery of the cellular telephone 1 is fully recharged. The current sensing element will sense a reduction of the current and the LED indicator is switched OFF to indicate a non-charging operation. - When the rechargeable back-up battery device 3 is connected to a charger, a current sensing element senses a current and the LED indicator is switched ON again. In the same way, when the voltage of the rechargeable battery 8 is

approximately equal to the charger voltage, the rechargeable battery 8 is fully recharged. The current sensing element will sense a reduction or drop of the current and the LED indicator is switched OFF to indicate a non- charging operation. - When the rechargeable back-up battery device 3 is connected both to the cellular telephone 1 and to the charger, both batteries will be charged simultaneously.

The device 3 preferably also comprises a switch (not shown) which needs to be activated by the user too make the device 3 start recharging the cellular phone battery.

An important feature of the present invention is that the output of the device 3 is never directly connected to the input contacts 5, 6. The control circuit 7 is always controlling the output voltage and/or current delivered to the cellular phone.

The control circuit preferably comprises a voltage booster or DC-DC converter, which increases/decreases the output voltage level of the rechargeable back-up battery device 3 when the output voltage level is lower/higher than the lower threshold voltage of the inboard control circuit of the cellular phone.

The rechargeable back-up battery device 3 preferably comprises a protective cover 10, to protect the plug 4 for example from being bent if it is kept in a pocket, or to protect it from dust and humidity. The cover 10 can be removable fastened to the rechargeable back-up battery device 3 by means of a fastening device (not shown). Preferably, the protective cover 10 is transparent, so the user can see that the plug 4 fits his/hers cellular telephone.

Many modifications and adjustments of the present invention will appear as natural for a man skilled in the art, either by interpretation of the abovementioned detailed description of the invention or by putting the invention into practice. The different producers of cellular phones use different voltage levels for their batteries and input threshold values, and the design of the rechargeable back-up battery device 3 according to the invention must be adapted accordingly.