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ELECTRIC-SUPPLY EQUIPMENT FOR
CAMERA
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to electric-supply equipment. More particularly, the present invention pertains to electric-supply equipment which is suitable for supplying electricity to small-sized portable electronic equipment such as a camera.
2. Description of the Related Art
The conventional camera uses a primary battery or a secondary battery as a power source. There is proposed electronic-supply equipment which uses a solar battery as an auxiliary battery to charge a secondary battery built in a camera (Japanese Patent Provisional Publication No. 63-91641).
In the case of the conventional camera which uses the primary battery as a power source, however, if a manganese primary battery is used, a plurality of cells must be used in order to provide a high voltage because the manganese cell has a low voltage. There is another problem in that it takes too long to charge a condenser of an electronic flash because of the large amount of current required. Thus manganese primary battery is not suitable for the recently-developed camera which has a zoom motor, etc. and requires high current. On the other hand, a lithium primary battery is able to provide a high voltage and a large amount of current, but has a disadvantage in that the battery is expensive and can damage the environment when discarded. Furthermore, if the battery has been consumed, the user cannot use the camera until the battery is replaced with a new one, or the user must carry an extra battery. If is sometimes difficult to get the lithium primary battery when traveling overseas, etc.
In the case of the conventional camera which uses a secondary battery as a power source, the charging method is restricted in many ways, and excessive charging and discharging can take place. For this reason, an expensive special charging device is required. In addition, if secondary battery is a nickel-cadmium battery, it will spontaneously discharge a large amount of electricity (a self-discharging rate is between 5% and 10% per month), and its capacity decreases if the battery is not used for a long period of time. For this reason, the battery must be recharged every time its capacity has decreased, and the battery sometimes deteriorates due to the excessive discharging and cannot be used any longer. Moreover, the user cannot use the camera while the secondary battery is being charged, or the user must carry an extra battery.
The electric-supply equipment using the solar battery has a disadvantage in that the solar battery is expensive, and the equipment must be placed under a high luminance. Thus, there is a possibility that the equipment temperature will increase and that the equipment will fail. Further, if the secondary battery is quickly consumed, the camera cannot be used for a long time, because the solar battery generates only a small amount of electricity, and it takes much time to charge the secondary battery.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide electricsupply equipment, in which a large amount of high-voltage high current can be supplied from a main battery to an electricity consuming apparatus, and if a power source has been consumed, only an auxiliary battery, which is inexpensive and easy to get, is replaced with a new one.
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It is another object of the present invention to provide electric-supply equipment for a camera, in which even if the auxiliary battery has been consumed, the shooting can be continued for a while without replacing the auxiliary battery.
5 In order to achieve the above-mentioned objects, electricsupply equipment of the present invention comprises: a rechargeable main battery for supplying electricity to an apparatus connected to the electric-supply equipment; an auxiliary battery housing section in which an auxiliary
10 battery is removably mounted; and a charging means using as a charging power source the auxiliary battery housed in the auxiliary battery housing section so as to charge the main battery. Hence, if the power source has been consumed, only the auxiliary battery (an AA battery for example), which is
15 inexpensive and easy to get, is replaced, and it is more economical and friendlier to the environment when compared to the case where the main battery is replaced. In particular, because a metal lithium secondary battery is used as the main battery, a large amount of high current can be
20 supplied from the main battery to the apparatus and the main battery spontaneously discharges only a small amount of electricity. For this reason, the apparatus can be used even after a long period of non-use.
Moreover, the charging means charges every time the
25 voltage of the main battery has reached a predetermined minimum value or electricity of the main battery has been consumed to a predetermined extent, transferring electric energy from the auxiliary battery to the main battery until the main battery is charged completely. Thereby, the electric
30 energy is supplied from the auxiliary battery to the main battery according to the electricity consumption of the main battery, so that the main battery can be kept charged. Thus, there is no possibility that the excessive discharging will cause the main battery to deteriorate, and the main battery is
35 easy to handle. Moreover, even if the auxiliary battery has been consumed, the main battery still has a charge, so that the apparatus can be used until the main battery is consumed. The apparatus may be used while the auxiliary battery is being replaced.
40 Furthermore, the electric-supply equipment for a camera according to the present invention comprises: a rechargeable main battery for supplying electricity to electricity consuming means within the camera connected to the electricsupply equipment; an auxiliary battery housing section in
45 which an auxiliary battery is removably mounted; a charging means which charges every time a voltage of the main battery has reached a predetermined minimum value or electricity of the main battery has been consumed to a predetermined extent, transferring electric energy from the
50 auxiliary battery to the main battery until the main battery is charged completely; and a display means for displaying an available amount of electric energy in the auxiliary battery, and after the auxiliary battery is consumed, displaying a number of shots which can be taken by means of available
55 electric energy remaining in the main battery. Hence, the auxiliary battery supplies the main battery with the electric energy according to the electricity consumption in the main battery as is the case in the above-described electric-supply equipment, so that the main battery can be kept charged and
60 there is no possibility that the excessive discharging will cause the main battery to deteriorate. Furthermore, even if the auxiliary battery has been consumed, the main battery still has a charge and the camera can be used until the main battery has been consumed. In particular, the number of
65 shots which can be taken without replacing the auxiliary battery can be confirmed by the display on the display means.
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BRIEF DESCRIPTION OF THE DRAWINGS
The nature of this invention, as well as other objects and advantages thereof, will be explained in the following with reference to the accompanying drawings, in which like reference characters designate the same or similar parts 5 throughout the figures and wherein:
FIG. 1 is a front view including an inner perspective diagram, showing a camera provided with electricity-supply equipment according to the present invention;.
FIG. 2 is a block diagram of an embodiment of the electricity-supply equipment according to the present invention;
FIG. 3 is a circuit diagram of an embodiment of a step-up circuit in FIG. 2; 15
FIG. 4 is a graph showing a state in that electric energy of an auxiliary battery is transferred to a main battery by a charging circuit in FIG. 4;
FIGS. 5 (A) and 5 (B) are plan views showing the display on a liquid crystal display in FIG. 2; 20
FIG. 6 is a top view of a camera provided with electricsupply equipment according to the present invention, including an inner perspective diagram of the camera;
FIG. 7 is a front view of a camera in FIG. 6, including an inner perspective diagram of the camera; and 25
FIG. 8 is a perspective view showing another embodiment of electric-supply equipment according to the present invention.
DETAILED DESCRIPTION OF THE 30
PREFERRED EMBODIMENTS
FIG. 1 is a front view of a camera which is provided with electric-supply equipment according to the present invention, including an inner perspective diagram of the 35 camera. In FIG. 1, reference numeral 10 is the electricsupply equipment, 12 is a taking lens, 14 is a finder, and 16 is an electronic flash.
The electric-supply equipment 10 is composed mainly of: a main battery 20; an auxiliary battery housing section 32 in ^ which an auxiliary battery 30 is removably mounted; and a charging circuit 40. The main battery 20 supplies electricity to the electronic flash 16, motors such as a zoom motor and a film feed motor, a camera controlling circuit, etc.
The main battery 20, which is used exclusively for 45 cameras, is rechargeable and hardly discharges spontaneously. For example, the spontaneous discharging rate is less than 5%/yr, and the voltage is 3.2 V if the battery has been charged properly.
A detailed explanation will hereunder be given about the 50 main battery. The positive pole active material of the main battery is preferably composed of manganese dioxide, and more suitably manganese dioxide synthesized by electroextraction or chemically-synthesized manganese dioxide. The negative pole active material is preferably composed of 55 lithium or lithium alloy (any kind of metal which makes the alloy with lithium may be used. Al, Mn, Sn, Mg, Cd and In are preferable. The alloy including Al is the best.)
A conductive agent, a binding agent, a filler, etc. may be added to an electrode mixture. As the conductive agent, any 60 electronic conductive material which does not cause a chemical change in the battery may be used. The additional amount is not particularly restricted; however, it is preferably between 1 wt % and 50 wt %, and more suitably between 2 wt % and 30 wt %. 65
Examples of the binding agent include: polysaccharide; thermoplastic resin; a sort of polymer having rubber elas
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ticity; and a mixture of them. The additional amount of the binding agent is not particularly restricted; however, it is preferably between 1 wt % and 50 wt %, and more suitably between 2 wt % and 30 wt %.
As the filler, any fibrous material which does not cause a chemical change in the battery may be used. Usually, the fiber such as olefinic polymer such as polypropylene and polyethylene; glass; and carbon is used. The additional amount of the filler is not particularly restricted; however, it is preferably between 0 wt % and 30 wt %.
Nonaqueous electrolyte ordinarily consists of a solvent and lithium salt (anion and lithium cation) soluble in the solvent. The electrolyte is preferably a mixture of propylene carbonate and/or butylene carbonate and 1,2dimethoxyethane and/or diethyl carbonate, including LiCF3S03, IJCIO4, LiBF4 and/or LiPF6. The amount of the electrolyte added to the battery is not particularly restricted. The additional amount of the electrolyte depends on the amount of the positive pole active material and the negative pole active material, and the size of the battery.
The volume ratio of the solvent is not particularly restricted; however, in the case of the mixture of propylene carbonate and/or butylene carbonate and 1,2dimethoxyethane, the ratio is preferably between 0.4:0.6 and 0.6:0.4. The density of supporting electrolyte is not particularly restricted; however, the supporting electrolyte is preferably between 0.2 moles and 0.3 moles per one litter of the electrolyte solution.
The auxiliary battery housing section 32 in FIG. 1 is formed in such a manner as to house one AA battery for example. An AA dry battery as the auxiliary battery 30 is housed in the auxiliary battery housing section 32. Another battery (a secondary battery) having the same shape as the AA battery may be used as the auxiliary battery.
The charging circuit 40 consists of a charge controlling circuit 42 and a step-up circuit 44 as shown in FIG. 2. The charge controlling circuit 42 measures the voltage Vcs of the main battery 20 and the voltage VE of the auxiliary battery 30. For example, if the voltage VCT of the main battery 20 is lower than 3.0 V, and the voltage VE of the auxiliary battery 30 is 0.9 V (the final voltage of the auxiliary battery 30) or higher, the charge controlling circuit 42 activates the step-up circuit 44 to charge the main battery 20.
On the other hand, if the main battery 20 has been charged completely (the voltage WCR reaches 3.2 V), or if the auxiliary battery 30 has been consumed to such an extent that the voltage V£ is lower than 0.9 V, the charge controlling circuit 42 stops the step-up circuit 44. Further, in order to display an available amount of electric energy in the auxiliary battery 30 on a liquid crystal display (LCD) 50, the charge controlling circuit 42 outputs a signal representing the voltage of the auxiliary battery 30 to a display controlling circuit 52 in the camera. A detailed description will be given later about the display on the LCD 50. The charge controlling circuit 42 is supplied with the driving power by the main battery 20.
Next, the step-up circuit 44 will be explained. FIG. 3 is a circuit diagram of an embodiment of the step-up circuit 44. As shown in FIG. 3, the step-up circuit 44 is of a push-pull type, and converts direct current supplied by the auxiliary battery 30 into alternating current by means of transistors Ql and Q2 which are turned on interchangeably by the charge controlling circuit 42. The step-up circuit 44 steps up the voltage with a transformer T, and then rectifies the current by a rectifier 45, thereby converting the direct current supplied
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