Electrical transmission or interconnection systems – Plural load circuit systems – Selectively connected or controlled load circuits
Reexamination Certificate
1999-03-04
2001-02-13
Ballato, Josie (Department: 2836)
Electrical transmission or interconnection systems
Plural load circuit systems
Selectively connected or controlled load circuits
C320S134000
Reexamination Certificate
active
06188142
ABSTRACT:
METHOD AND ARRANGEMENT FOR DISCONNECTING LOADS
This invention relates to a method and an arrangement for disconnecting loads connected to a voltage source, for example, a direct-current voltage source. For the purposes of the present invention, loads are in particular power consuming devices which are contained in usually mobile apparatus known in the art and powered by solar cells, primary or secondary batteries and which include, for example, electronic circuits, motors, microprocessors or the like.
From DE 41 31 981 A1 and DE 42 41 066 A1 circuit configurations are known in which a voltage discriminator determines the voltage of a battery. After the voltage has achieved a pre-determined value, current flow through a load connected to the battery is reduced to zero value continuously or in steps by means of a control circuitry. However, in these circuit configurations only the load on the battery caused by the device consuming the greatest share of the current is reduced. Other system components as, for example, the control circuitry itself, continue to deplete the battery, though at a slower rate.
From DE 41 16 318 A1 a circuit configuration for protecting a storage battery from deep discharges is known, having an electronic switching device which disconnects the connected load from the storage battery when the storage battery's voltage drops to a value below a definable threshold value.
Hence, in the circuit configurations known in the art, the connected loads are either disconnected from the battery instantly or the supply of power is adjusted downward within a predetermined period of time when the battery voltage decreases as discharging of the battery is proceeding, thereby avoiding deep discharging of the battery. This is of importance in particular in the use of lithium secondary batteries to prevent damage to the battery.
The present invention is based on the realization that an electrical apparatus frequently has different loads some of which can be disconnected instantly when one or several shutdown conditions are met, whilst for some other loads it is desirable that the supply of power be adjusted downward at a slow rate for safety or psychological reasons.
By way of example an electrical household appliance is referred to, in particular a battery-powered shaver, which has a motor whose power needs to be reduced slowly when a shutdown condition is satisfied in order to prevent beard hairs from being pinched painfully. By contrast, for example, a micro-controller or a measuring circuit can be turned off instantly.
However, also in systems which normally would permit an instant shutdown, a gradual reduction in the intensity of perceivable function indicators as, for example, the intensity of light or sound, is apt to indicate to the user that the secondary battery is discharged, whereas, by contrast, an abrupt abortion of the function could suggest a defect.
According to the method indicated in claim
1
of the present invention, loads connected to a voltage source are disconnected from the voltage source in two steps after at least one shutdown condition is met, the first step involving a reduction in the current supplied to those loads for which a slow downward adjustment is appropriate, and the subsequent step involving disconnection of the remaining loads.
Because the various loads are disconnected successively in time, particularly those systems that are needed for effecting the slow downward adjustment of the power supplied to the loads continue to be operable until the process of downward adjustment is completed. Then these systems are turned off as well.
According to present invention, the current supplied to the loads to be subjected to the downward adjustment is reduced to a presettable value, for example, zero value. By the subsequent shutdown of the loads to be disconnected, preferably the loads that already have been subjected to the downward adjustment are also disconnected from the voltage source. This is necessary particularly in cases in which the presettable value referred to above is unequal to zero.
In cases in which the shutdown condition is defined by the magnitude of the voltage of a voltage source, it is particularly advantageous to use voltage sensors with a digital output so that the sensors′ output signal changes from a LOW to a HIGH level or vice versa in the presence of a selectable threshold value. This makes it possible, by selection of the threshold value, to adapt the circuit arrangement of the present invention to the voltages of a wide variety of voltage sources including, for example, any type of battery Dr solar cell.
However, the shutdown condition is also determinable by the temperature or other measured quantities as, for example, speed, current, brightness or sound, which are detected by appropriate sensors.
According to the present invention, the process of downward adjustment of a load needing to be subjected to downward adjustment does not start until the output signal of a first voltage sensor detects that the voltage UBATT supplied by the voltage source has fallen below a predetermined threshold value UBATTmin or until some other shutdown condition has occurred. In a solar cell, for example, this is the case when dusk sets in, and in a secondary battery when discharging continues progressively. The process of downward adjustment is considered completed when a second voltage sensor detects that the supply voltage UV residing at the loads to be subjected to the downward adjustment has dropped below a predetermined threshold value UVmin, or when a prescribed period of time has expired which is assumed to be of a duration sufficiently long to execute the downward adjustment. Only after these conditions are satisfied are the loads allowing instant shutdown and, for safety reasons, preferably also the loads that are already downward adjusted, disconnected from the voltage source.
When the voltage of the voltage source rises again above this threshold value UBATTmin or some other threshold value UBATTmin′, current supply to the loads is resumed. The increase in voltage can be due to, for example, the replacement or recharging of the secondary battery or the connection of a power supply.
With the power supply appropriately designed, the loads can be operated in the two-way mode in a manner known in the art, meaning that power is supplied to the loads from the power supply and, if applicable, the secondary batteries are recharged. This makes it possible to operate the loads also in the event of a depleted secondary battery.
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patent: 5804894 (1998-09-01), Leeson et al.
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“Battery Fail-Safe Mechanism for Personal Computer”, IBM Technical Bulletin, vol. 33, No. 10A Mar. 1991, pp. 440-442.
Ballato Josie
Braun GmbH
DeBeradinis Robert L.
Fish & Richardson P.C.
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