Abstract:
A system and method for conditioning a power transmission, thereby eliminating adverse characteristics from the power transmission. The system selectively includes a voltage surge protector, an EMI/RFI filter and at least one inrush current suppressor integrally formed into a single system. To condition an incoming power transmission, the power transmission is passed through the voltage surge protector to eliminate any abnormal voltage spikes. The power transmission is then passed through an improved EMI/RFI filter having a dual output. The outputs of the EMI/RFI filter lead into a first inrush current suppressor. The inrush current suppressor limits the amperage of the power transmission for a predetermined period of time and then permits unrestricted current flow.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     In general, the present invention relates to systems that filter out adverse characteristics that may be present in a power transmission from a power supply. More particularly, the present invention relates to the systems that provide voltage surge protection, EMI/RFI protection and/or in-rush current suppression to a power transmission. 
     2. Prior Art Statement 
     The prior art is replete with different types of devices and circuits that filter out undesired electrical characteristics from an incoming source of electricity. In the United States of America, most every home and business is supplied with power from a utility company. Typically, the power supplied from the utility company passes through a transformer and is supplied to a building with an alternation current of 120 volts and a nominal frequency of 60 Hz. Although the power at the utility company is generated at these voltages and frequency values, the actual power received at a particular home or business can vary widely depending upon both how the power is transmitted and how the power is used. 
     Power transmission lines emanating from utility companies are commonly exposed to the elements as they travel from the utility company to a home or business. As such, the power transmission lines are subject to lightning strikes, interference from sun flares, storm damage and the like. All of these occurrences can create abnormalities in the characteristics of the power being transmitted in the transmission line. For example, a lightning strike in a power transmission line can create a large voltage spike in the power being transmitted. If this voltage spike is received by a home or business, the voltage spike can cause damage to many electronic items that experience the voltage spike. Alternatively, power can be disrupted if the spike causes a circuit breaker to trip. 
     Similarly, power transmission lines can receive electromagnetic interference (EMI) and/or radio frequency interference (RFI) from natural and manmade sources. The resulting EMI/RFI signals cause noise in the characteristics of the power transmission that can disrupt sensitive electronic circuits that receive such power transmissions. 
     Power transmissions with undesirable characteristics can also be created by the way power is used in a home or business. Many electronic devices draw a higher current when they are first turned on. This is because the circuits in the electronic device are cold and the capacitors in the circuits are not charged. However, soon after the circuit is powered, the current drawn by that circuit can decrease dramatically. As a result, when an electronic device is first turned on, there is an inrush of current, thereby causing a current spike. If multiple electrical devices are all turned on at once, the inrush current spike can be quite large and either cause a circuit breaker to trip or cause damage to the electronic components of those devices that experience the current spike. 
     In the prior art, there are many different filtering devices that are used to eliminate adverse characteristics from a power supply. However, many of these filters are designed to filter out only one type of adverse characteristic. For example, there are many types of commercially available surge protector items that can eliminate voltage spikes caused by lightning. Such prior art surge protectors are exemplified U.S. Pat. No. 4,870,534 to Harford, entitled Power Line Surge Protector. However, such prior art surge protection devices do not protect from EMI/RFI signal interference or incidents of inrush current. 
     Similarly, devices exist in the prior art record that are designed to filter EMI/RFI signal interference from power supplies. Such prior art filters are exemplified by U.S. Pat. No. 5,530,396 to Vlatkovic, entitled EMI Input Filter Power Factor Correction Circuits. However, such prior art devices do not filter out voltage surges or inrush current surges. 
     Lastly, devices exist in the prior art that are designed to eliminate inrush current surges. Such prior art devices are exemplified by U.S. Pat. No. 4,573,113 to Bauman, entitled Surge Protection System For A D-C Power Supply During Power-up, and U.S. Pat. No. 5,930,130 to Katyl, entitled Inrush Protection Circuit. However, such prior art devices do not filter out EMI/RFI signal interference or voltage surges. 
     A need therefore exists for an improved filtering system that is capable of eliminating voltage surges, EMI/RFI signal interference and inrush current spikes from a power source. This need is met by the present invention as described and claimed below. 
     SUMMARY OF THE INVENTION 
     The present invention is a system and method for conditioning a power transmission, thereby eliminating adverse characteristics from the power transmission. The system includes a voltage surge protector, an EMI/RFI filter and at least one inrush current suppressor integrally formed into a single system. To condition an incoming power transmission, the power transmission is first passed through the voltage surge protector to eliminate any abnormal voltage spikes. The power transmission is then passed through an improved EMI/RFI filter having a dual output. The outputs of the EMI/RFI filter lead into a first inrush current suppressor. The inrush current suppressor limits the amperage of the power transmission for a predetermined period of time and then permits unrestricted current flow. The inrush current suppressor also can be used as an on/off switch to stop the power transmission. The on/off state of the inrush current suppressor is dependent upon the receipt of an external control signal by the inrush current suppressor. 
     Electronic equipment receives the power transmission through the circuitry of the inrush current suppressor. Multiple inrush current suppressors can be arranged in a cascading system to power many different collections of electronic equipment. As one inrush current suppressor is activated, it generates a time delayed control signal that can be used to activate a subsequent inrush current suppressor. In this manner, different collections of equipment can be turned on in a controlled sequence that does not surpass the amperage rating of the circuit breaker through which the power transmission is passed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a better understanding of the present invention, reference is made to the following description of exemplary embodiments thereof, considered in conjunction with the accompanying drawings, in which: 
     FIG. 1 is schematic of an exemplary embodiment of a power conditioning system in accordance with the present invention; 
     FIG. 2 is a schematic of an exemplary embodiment of an EMI/RFI filtering circuit for use in the present invention power conditioning system; and 
     FIG. 3 is a schematic of an exemplary embodiment of an inrush current suppressor circuit containing control circuitry for use in producing an automatically cascading system. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Although the present invention power conditioning system can be created as internal circuitry within many different types of electronic equipment, the present invention power conditioning system is particularly well suited for use as a self-contained unit. In this manner, the present invention power conditioning system can be used to condition incoming electrical power and any separate electronic device can then be connected to the power conditioning system to receive the conditioned power. Accordingly, in the exemplary embodiment of the invention that is shown, the present invention power conditioning system is shown as a self-contained unit that is separate from the electronic equipment that receives electrical power through the power conditioning system. 
     Referring to FIG. 1, a schematic of the present invention power conditioning system  10  is shown. In the embodiment, the power conditioning system  10  is connected to utility power lines  12  and receives power from the local utility company  14 . The power conditioning system  10  removes adverse characteristics that may be present in the incoming electrical power transmission and presents the conditioned power to at least one output port  20 . The output port  20  can be the circuit breaker box of a building, thereby providing filtered power to every receptacle in the building. Alternatively, the output port  20  can be a single receptacle that supplies filtered power to a single piece of electrical equipment  22  that is plugged into the power conditioning system  10 . 
     In the power conditioning system  10  there are three types of circuits that are used to condition the power transmission received from the utility company  14 . Each type of circuit filters a particular adverse electrical characteristic from the received power. The first of the circuits, is a voltage surge protector  24 . The voltage surge protector circuit  24  eliminates voltage spikes in the received power transmission that may be caused by lightning strikes, shorted transformers or the like. In the prior art, there exist many different types of voltage surge protector circuits that can eliminate voltage spikes. Many of these prior art circuits can be adapted for use in the present invention filtering system. However, the surge protector circuitry found in U.S. Pat. No. 4,870,528 to Harford, entitled Power Line Surge Protector is particularly advantageous and is preferred in the exemplary embodiment of the invention. Accordingly, the disclosure of U.S. Pat. No. 4,870,528 to Harford is therefore incorporated into this specification by reference. 
     The second type of power condition circuit, embodied by the present invention system, includes an EMI/RFI filter  26 . The output of the voltage surge protector  24  is received by an EMI/RFI filter  26 . Due to the presence of the voltage surge protector  24 , any voltage spikes in the received power signal have been removed. However, EMI and/or RFI signal noise can still be present in the power signal. The EMI/RFI filter  26  reduces noise present in the power signal transmission that can be categorized as either electromagnetic interference or radio frequency interference. In the prior art, there exist many types of EMI/RFI filters. Many of these prior art filters can be adapted for use as part of the present invention power condition system  10 . However, a specific EMI/RFI filter  26  is preferred in the exemplary embodiment. This circuit will later be described with reference to FIG.  2 . 
     The output of the EMI/RFI filter  26  is then received by at least one inrush current suppressor  28 . It is the inrush current suppressor  28  that is the third power conditioning circuit of the present invention system  10 . As such, by the time the power transmission is received by the inrush current suppressor  28 , the power transmission has already been filtered of voltage spikes and EMI/RFI noise. At least one inrush current suppressor is present in the power conditioning system  10 . However, as is shown in FIG. 1, any plurality of separate inrush current suppressors  28  can be used. As will later be explained, the various inrush current suppressors  28  can be arranged in a cascading array. As such, each of inrush current suppressors  28  is activated after the previous inrush current suppressor  28  has finished powering up. In this manner, separated groupings of electronic equipment  22  can be kept on the same circuit without surpassing the amperage rating for that circuit when the various groupings of equipment are first turned on. 
     As is shown in FIG. 1, each inrush current suppressor  28  supplies power to a separate grouping of electronic equipment  22 . The first of the inrush current suppressors  28  may also be optionally coupled to a remote activation unit  30 . As will later be explained, the remote activation unit  30  enables the first of the inrush current suppressors  28  to be selectively activated when needed and/or desired. 
     Accordingly, the present invention power conditioning system  10  takes the power transmission from the utility company, removes voltage spikes, EMI/RFI noise and inrush current spikes prior to that power being presented to an electronic device  22 . 
     Referring now to FIG. 2, an exemplary embodiment of an EMI/RFI filter  26  is shown that can be used in the present invention power conditioning system  10 . The EMI/RFI filter  26  receives a power transmission from the voltage surge suppressor  24  (FIG.  1 ). The EMI/RFI filter  26  contains a mutual inductor  32 , sometimes referred to as a common-mode choke. The mutual inductor  32  provides mode attenuation to EMI noise and RFI noise. Two ferrite beads  34 ,  36  are used on the leads that leave the mutual inductor  32 . The presence of the ferrite beads  34 ,  36  provides series impedance to the power signal, thereby attenuating EMI noise and RFI noise. The presence of the ferrite beads  34  also prevents the EMI/RFI filter  26  from ringing and helps control filter characteristics. The EMI/RFI filter  26  also contains three capacitors. The first capacitor  37  is for when the filter is operating in normal mode, wherein the capacitor  37  provides low impedance to EMI noise and RFI noise. The second and third capacitors  38 ,  39  are arranged across the outputs of the filter  26  and provide low impedance to EMI noise and RFI noise when the filter operates in a common mode. 
     The EMI/RFI filter  26  shown in FIG. 2 has two outputs  40 . These outputs  40  are received by the inrush current suppressor  28 , which is shown in FIG.  3 . Referring to FIG. 3, it will be understood that the output of the EMI/RFI filter  26  is 120 volts AC. However, EMI/RFI noise has been removed and voltage spikes have been eliminated. The outputs  40  of the EMI/RFI filter  26  are supplied to the inrush current suppressor at two points. At the first point, the incoming power passes into a first relay  42 . At the second point, the incoming power passes into a second relay  44 . If either the first or second relay  42 ,  44  is closed, the power passes through to an output port  46 . It is this output port  46  that is coupled to external electronic equipment  22  (FIG.  1 ). 
     The operation of the first and second relays  42 ,  44  is dependent upon an integrated control circuit containing three transistors  47 ,  48 ,  49 . The integrated control circuit has two control signal input ports  43 ,  52  that are used to trigger the operation of the circuit. The first control signal input port  43  is coupled directly to the common DC voltage  50 . A first resistor  45  is disposed within the connection pathway. The second control signal input port  52  is coupled to the base of the first transistor  47 . A second resistor  51  is disposed in this pathway. 
     The collector of the first transistor  47  and the emitters of the second and third transistors  48 ,  49  are connected to a common DC voltage  50 . A third resistor  53  is present between the base of the first transistor  47  and ground. A fourth resistor  54  is present between the collector of the first transistor  47  and the common DC voltage  50 . 
     The base of the second transistor  48  is coupled to the collector of the first transistor  47 . However, a first capacitor  55  and a fifth resistor  56  are positioned in series between these two points. A sixth resistor  57  is positioned between the base of the second transistor  48  and the DC voltage source  50 , wherein the sixth resistor  57  is in series with both the fifth resistor  56  and the first capacitor  55 . 
     The base of the third transistor  49  is coupled to the collector of the first transistor  47 . However, a seventh resistor  58  and an eighth resistor  59  are positioned in series between these two points. A ninth resistor  60  is positioned between the base of the third transistor  49  and the common DC voltage  50 , wherein the ninth resistor  60  is in series with both the seventh resistor  58  and the eighth resistor  59 . A second capacitor  61  is placed in parallel with the eighth and ninth resistors  59 ,  60 , respectively. 
     The operation of the various transistors  47 ,  48 ,  49  and thus the first and second relays  42 ,  44  are controlled by the selective application of a control input voltage. The control input voltage is received at the control signal input port  52  and can be between 5 volts and 30 volts DC. Alternatively, the circuit can be controlled by a contact closure between the first control signal input port  43  and the second control signal input port  52 , wherein the second control signal input port is directly coupled to the common DC voltage  50 . 
     When a control input voltage is received that is over 5 volts DC, the first relay  42  is energized and the power supply signal is transmitted directly from the input ports  40  to the output port  46  through a high energy surge resistor  62 . 
     When an appropriate voltage is applied to the control signal input port  52 , the voltage is immediately experienced by the second resistor  51  and the first transistor  47  is switched on. Once the first transistor  47  is switched on, the voltage at the fourth resistor  54  and seventh resistor  58  are pulled low. The first capacitor  55  is initially uncharged. Accordingly, when the first transistor  47  is turned on, the voltage across the fifth resistor  56  is pulled down. This turns on the second transistor  48 . The activation of the second transistor  48  enables the first rely  42  to be energized, thereby enabling electricity to flow from the first of the input ports  40  to the output port  46 . However, the AC current flowing through the first relay  42  passes through the high energy surge resistor  62  that limits the inrush current to a maximum of 25 amps. 
     Simultaneously, as the first transistor  47  turns on and the seventh resistor  58  is pulled low, the second capacitor  61  charges. The second capacitor  61  is initially uncharged and therefore prevents the voltage on the eighth resistor  59  from being pulled low. As the voltage on the eighth resistor  59  rises, the third transistor  49  turns on. However, this takes about one half of a second to occur. This period of time can be selectively adjusted between 0.1 seconds and 1.0 second by varying the values associated with the eighth resistor  59  and second capacitor  61 . Once the third transistor  49  is turned on, the second relay  44  is energized. When the second relay  44  is energized, the high energy surge resistor  62  is bypassed and current flows directly to the output port  46  unrestricted. 
     As the first capacitor  55  continues to charge, the voltage on the fifth resistor  56  rises. After between a one second and a five second delay, the second transistor  48  turns off. This de-energizes the first relay  42 , thereby disconnecting the high energy surge resistor  62  from the load. This protects the high energy surge resistor  62  from overheating or burning out should the second relay  44  fail to energize. 
     An optional third relay  70  can also be used within the circuitry of the power conditioning system  10 . The third relay  70  has a coil that is wired in parallel to the coil of the second relay  44 . Accordingly, when the third transistor  49  is activated, both the second relay  44  and the third relay  70  are energized. When the third relay  70  is energized, at least one new circuit is closed. A control voltage can be sent through the circuit that is closed by the third relay  70 . This circuit can be interconnected to the control signal input ports of a second inrush current suppressor circuit that is identical to the one shown in FIG.  3 . As has been previously described, the third transistor  49  does not activate until approximately one half second after the activation of the first transistor  47 . Accordingly, since the third relay  70  is controlled by the third transistor  49 , the third relay  70  does not energize until approximately a one half second delay has occurred. 
     By interconnecting the contacts of the third relay  70  of one inrush current suppressor  28  to the control signal input ports of a subsequent inrush current suppressor, a cascading system can be created. In the cascading system, any number of inrush current suppressors can be activated one after another with an approximate one half second delay in activations. 
     Referring back to FIG. 1, multiple inrush current suppressors  28  are shown to illustrate that any number of inrush current suppressors  28  can be arranged in a cascading system. However, since the inrush current suppressors  28  can be used to directly activate electronic equipment  22 , the activation of the first inrush current suppressor is preferably selectively controlled. It is for this reason that a remote activation unit  30  can be provided. The remote activation unit  30  can be a wall switch, a control panel switch or any other manually or remotely activated switch that can be selectively thrown by a user. Alternatively, the remote activation unit  30  can be any source capable of providing a DC voltage to the second control signal input port  52  of between 5 volts and thirty volts. Once the remote activation unit  30  is activated, the first inrush current suppressor  28  is activated and the subsequent inrush current suppressors are automatically activated by the cascading effect. 
     Returning to FIG. 1, the power condition system  10  is shown having three major circuits, which are the voltage surge protector  24 , the EMI/RFI filter  26  and the inrush current suppressor  28 . The use of all three circuits in the stated order is merely exemplary. The present power condition system  10  may include any two of the circuits. Accordingly, the power condition system  10  may include a voltage surge protector  28  with either an EMI/RFI filter  26  or an inrush current suppressor  26 . Similarly, the power condition system  10  may include an EMI/RFI filter  26  with either a voltage surge protector  24  or an inrush current suppressor  26 . 
     Furthermore, the sequence in which the various circuits are used in the power conditioning system  10  can be selectively altered. In FIG. 1, the incoming power passes through the voltage purge protector  24 , EMI/RFI filter  26  and then the inrush current suppressor. This sequence can be selectively changed into any alternate order. 
     It will be understood that the embodiments of the present invention system described and illustrated are merely exemplary and a person skilled in the art can make many variations to the shown embodiment. For example, a circuit designer can create many circuits that perform the same functions as the circuits specifically illustrated. All such alternate embodiments and modifications are intended to be included within the scope of the present invention as defined below in the claims.