Abstract:
An uninterruptible power supply with energy control includes a source of direct current (DC) voltage and current with a battery coupled to an inverter. The output from the inverter is applied to a computer or other loads. A charger is disposed between power line input and the battery as a component of the direct current source.

Description:
[0001]    Priority claimed Based on Ser. No. 60-281,839 filed Apr. 6, 2001. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to the field of power circuits and particularly to an uninterruptable power supply (UPS) inserted between a source of AC power and a load such as a computer monitor or other computer peripherals designed to supply power to the load in the event the source of AC power should be interrupted for some predetermined period of time. This concept provides for a UPS unit inserted between a source of AC line power and its load in order to draw only a fixed amount of power from the AC power source.  
           [0004]    2. Description of Prior Art  
           [0005]    There are a great number of uninterruptable power supplies on the market today and can be divided into two basic types. The first type of circuit continues to supply power when the power fails. The second type of circuit supplies the power continuously to a selected load from a battery which is continuously charged while the power line signal is present. With this circuit, no switching is required. The latter type is not as efficient as the former since it must operate continuously whereas the former type draws power directly from the power line unless there is a failure. A third type of uninterruptable power supply is disclosed in U.S. Pat. No. 5,737,209, issued on Apr. 7, 1998, wherein a direct current output is presented to the load by the uninterruptable supply.  
           [0006]    Therefore, a need has existed to provide a UPS circuit to a load when no interruption from an AC source is present when the load requires more power than a predetermined amount.  
         SUMMARY OF THE INVENTION  
         [0007]    The subject invention deals with the second type of uninterruptable supply noted above which provides a circuit having a limit on the amount of power that can be drawn from an AC power line forcing a battery to supply that additional power whenever power it is needed and allowing the battery or batteries to be recharged when the power from the line is not needed.  
           [0008]    Therefore, it is an object of this invention to control the amount of energy that is drawn from a AC power source such that it will not exceed a predetermined amount.  
           [0009]    Another object of the invention is to incorporate changes in existing UPS devices to accomplish a peak energy control.  
           [0010]    Yet another object in this invention is to do all of these things in a manner that is economical and that would be commercially accepted  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The present invention, both as to it organization and manner of operation, together with further objects and advantages thereof, may best be understood with reference to the following description, taken in connection with the accompanying drawings in which:  
         [0012]    [0012]FIG. 1 is a basic block diagram of a UPS installation;  
         [0013]    [0013]FIG. 2 is a block diagram of the internal components in the UPS installation shown in FIG. 1;  
         [0014]    [0014]FIG. 3 is a complete circuit diagram of the UPS installation; and  
         [0015]    [0015]FIG. 4 is a graph illustrating the amount of power drawn from the power line including current limiting.  
     
    
     DESCRIPTION OF PREFERRED EMBODIMENT  
       [0016]    [0016]FIG. 1 depicts a UPS installation where AC power enters on lines  1  and  2  to an uninterruptible power supply  3  which contains a battery  4 . Uninterrupted AC power is fed from lines  5  and  6  to a computer and/or peripherals or other loads  7 .  
         [0017]    [0017]FIG. 2 is a block diagram of the internal components of the UPS indicated by numeral  3  in FIG. 1. Input power enters on lines  1  and  2  and supplies a battery charger  11 . Power from the battery charger is fed through lines  12  and  13  to charge battery  14  and supply power to an inverter  17 . Inverter  17  generates AC power which outputs on lines  18  and  20  to a socket  21  into which any item or load needing uninterruptible AC power may be plugged.  
         [0018]    [0018]FIG. 4 is a graphic representation of the power usage. The amount of energy allowed to be drawn from the power line is set a certain amount, in this case  40  watts.  
         [0019]    Referring now to the circuit shown in FIG. 3, the power enters as before on lines  1  and  2  and is introduced to the primary  23  of a transformer  22 . The secondary output of transformer  22  is rectified to a DC voltage by a pair of diodes  28  and  30  operating as a center tapped bridge net work with a center tap point  27  forming a common bus  29 . Filtering is accomplished by capacitor  31 . Any form on DC power supplied to filter capacitor  31  will supply the necessary voltage and current for a transistor  33  and a resistor  32 . Transistor  33  is a series charging current regulator which controls both the voltage and current supplied to battery  14  by charger output line  12  and through a current sensor resistor  47  back to the common bus  29 . Transistor  33  is biased “on” by current flowing through resistor  32  unless that current is caused to flow into either an operational amplifier  38  or  40 . Operational amplifier  38  serves to shut down transistor  33  by drawing off the drive current whenever the voltage on battery  14  reaches or exceeds a predetermined amount. This amount is set by the values of voltage dividers  45  and  46  flowing in on the negative input of the operational amplifier. This voltage is compared to the voltage on a zener diode  44  which is biased to a predetermined amount by the current flowing through a resistor  43 . As long as voltage on battery  14  is below this preset amount, transistor  33  will be “on” unless operational amplifier  40  turns it “off”.  
         [0020]    If the charging current in battery  14  exceeds a certain amount, the voltage across a current sensor resistor  47  will rise and it is presented, via resistor  51 , to input  52  of operational amplifier  40 . When the current into the battery and load combination becomes too high, the voltage across resistor  47  exceeds the voltage on an input  53  which is set by voltage dividers  48  and  51 , using the zener diode  44  reference voltage, the transistor is turned “off”. When the load plugged into socket  21  of FIG. 2 draws power from the inverter  17  of FIG. 2, the inverter will draw power from battery  14 . This will reduce its voltage causing transistor  33  to turn “on”. However, if the current exceeds a preset amount, operational amplifier  40  will override and limit the current in transistor  33  and the battery will be forced to supply the additional energy directly.  
         [0021]    The previous description is of a series pass regulator functioning as the battery charger  11  that limits the power flowing into the battery and load combination to a predetermined amount.  
         [0022]    Referring further to FIG. 4, with current limiting as described above, it can be seen that no more than the specified amount of power may be drawn from the power line. When the load is drawing less than the allowed amount then the rest of the power may be used to replace the power used from the battery (recharge) when the load needed more power than the allowed amount.  
         [0023]    While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from this invention in its broader aspects and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.