Electricity: battery or capacitor charging or discharging – Serially connected batteries or cells – With discharge of cells or batteries
Patent
1983-03-14
1986-10-07
Hickey, R. J.
Electricity: battery or capacitor charging or discharging
Serially connected batteries or cells
With discharge of cells or batteries
363 62, 368204, G04C 1000, G04G 100, H02J 700
Patent
active
046161678
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an electronic apparatus, and more specifically a small portable apparatus having a long life solid state battery, more particularly still to a lithium-iodine battery, an integrated circuit and either a liquid crystal display, a light emitting diode display or a motor driven analog display. An advantage of such apparatus is that they work for example up to 10 years without changing the battery. However, in order to attain even small dimensions the power supply circuit must be optimalized. The internal resistance of the batteries is relatively high so that they cannot directly deliver current peaks such as those which occur during switching processes and more particularly during the driving pulses of a stepping motor or during intermittent switching on of a light emitting diode, without requiring a prohibitive increase of the active surface of the battery.
It is known that long life solid state batteries have a voltage of 2.8 V and a characteristic of voltage which depends on the ratio of the internal resistance to the load resistance. The internal resistance is very high to prevent self discharge which is a decisive feature of these batteries. The most favourable practical resistance lies at about 50 kOhm. With regard to this point, reference is made to the indications of the manufacturing company Catalyst Research Corp. and its U.S. Pat. Nos. 3,660,163, 3,674,562 and 3,723,183.
It is well known that the kind of integrated circuit manufacturing which is the most favorable of practical use in the above, the working voltage is about 1.5 V. The average operating current for the applications mentioned alone lies at about 2-5 .mu.A so that with a capacity after battery of 300-400 mAh, a service life of more than 10 years may be realized. Although the functions of integrated circuits does not change at higher voltages, one obtain a very high increase in current higher voltages, up to 50 uA which practically obviates the utilization of long life batteries.
A lay out of an integrated circuit for an operating voltage of 2.8 V would lead to the further disadvantage that all production lines for calculators or watches would have to be modified and further that the quality would decrease. Further a separate function would become necessary for those types of integrated circuits which presuppose a relatively small internal resistance power supply such as conventional batteries, as opposed to a lithium-iodine battery with solid electrolyte. Because of the above indicated reasons, so called long life batteries are not capable of practical use in the above mentioned applications. In order to avoid misunderstanding it is further mentioned that lithium-iodine batteries with liquid electrolyte are also available. They have a unique capability to deliver very great amounts of energy for short periods of time. However like all batteries with liquid electrolyte, they share the disadvantage of a short service life.
The object of the present invention is to facilitate a breakthrough in the utilization of long life solid state batteries such as for example lithium-iodine batteries, for electronic small apparatus like calculators or watches.
The electronic apparatus according to the present invention is characterized in that power is supplied at least for integrated circuits through a resistor having a voltage drop of at least about 1.3 V and in that a capacitor, having a capacity of 5 to 10 .mu.F, is provided for delivering peaks of current. This provides an adaptation of the voltage of the battery to the voltage of the integrated circuit and the peaks of current are delivered by the capacitor in such a way that no breakdown of the voltage at the integrated circuit and no disturbing of the function of the latter will occur. It is known that the internal resistance increases in accordance with the discharge time of the battery. Nevertheless, in order to provide a constant operating voltage, at least for integrated circuits it is preferable to choose a resistance having a value many times greater than
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