Abstract:
An overvoltage protection device includes a disconnect circuit configured to be coupled to a voltage source having a phase conductor and a neutral conductor, an output voltage connection coupled to the disconnect circuit; and a microprocessor circuit in communication with the disconnect circuit. The disconnect circuit is also configured to detect an overvoltage condition with respect to the phase conductor and the neutral conductor and to provide a first signal to the microprocessor circuit indicating whether the overvoltage condition is detected. The disconnect circuit is further configured to disconnect the phase conductor and the neutral conductor from the output voltage connection in response to a second signal from the microprocessor circuit if the overvoltage condition is detected, and to connect the phase conductor and the neutral conductor to the output voltage connection in response to the second signal if the overvoltage condition is not detected.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS  
       [0001]     This application claims the benefit of U.S. Provisional Application No. 60/641,627, filed Jan. 4, 2005 and entitled “Overvoltage Protection Device,” incorporated herein by reference in its entirety. 
     
    
     BACKGROUND  
       [0002]     The present description relates generally to overvoltage protection devices, and more specifically to overvoltage protection devices configured to protect electrical equipment from power supply voltage surges by automatically disconnecting and reconnecting the power supply.  
         [0003]     Uninterruptible power supplies (UPSs) provide electrical power, such as from a back-up battery, to a connected load in the event of an interruption in the main incoming electrical power source. Voltage surges and overvoltage conditions are a common type of power source disturbance that can impact the performance of both the UPS and the connected load. Surge suppression devices, such as metal-oxide-varistors (MOVs) are commonly used to protect against voltage surges. However, prolonged exposure to voltage surges, or even brief exposures to large overvoltage conditions may damage both the UPS surge suppression circuitry or the connected load, as well as create fire or electrical hazards. Overvoltage protection devices which disconnect the incoming electrical power source during overvoltage conditions have been employed to protect against damage from overvoltage conditions. However, while disconnection of the incoming electrical power source during an overvoltage condition can reduce or even prevent damage, in order to be effective the disconnection device should be fast enough to reduce the amount of exposure to the overvoltage condition, should eliminate any possible paths for the overvoltage condition, and should provide a convenient way to restore power once the overvoltage condition is no longer present.  
         [0004]     There is a need for an overvoltage protection device for use with a UPS or other device that provides improved protection for both the UPS or other device and any connected loads during a detected overvoltage condition. There is also need for an overvoltage protection device that provides a complete disconnect from a power source during a detected overvoltage condition, and automatically reconnects the power source once the overvoltage condition is no longer detected. There is also need for an overvoltage protection device that provides protection for internal surge suppressors and other internal circuitry during an overvoltage condition. There is also need for an overvoltage protection device that provides a quick response and reduces exposure to a detected overvoltage condition.  
         [0005]     Accordingly, there is a need to provide an overvoltage protection device having any one or more of these or other advantageous features.  
       SUMMARY  
       [0006]     According to an exemplary embodiment, an overvoltage protection device includes a disconnect circuit configured to be coupled to a voltage source having a phase conductor and a neutral conductor, an output voltage connection coupled to the disconnect circuit; and a microprocessor circuit in communication with the disconnect circuit. The disconnect circuit is also configured to detect an overvoltage condition with respect to the phase conductor and the neutral conductor and to provide a first signal to the microprocessor circuit indicating whether the overvoltage condition is detected. The disconnect circuit is further configured to disconnect the phase conductor and the neutral conductor from the output voltage connection in response to a second signal from the microprocessor circuit if the overvoltage condition is detected, and to connect the phase conductor and the neutral conductor to the output voltage connection in response to the second signal if the overvoltage condition is not detected.  
         [0007]     According to another exemplary embodiment, a method of providing overvoltage protection includes detecting whether an overvoltage condition is present with respect to a phase conductor and a neutral conductor of a voltage source coupled to a disconnect circuit of an overvoltage protection device, providing a first signal to a microprocessor circuit in communication with the disconnect device indicating whether the overvoltage condition is detected, disconnecting the phase conductor and the neutral conductor from an output voltage connection coupled to the disconnect circuit in response to a second signal from the microprocessor circuit if the overvoltage condition is detected, and connecting the phase conductor and the neutral conductor to the output voltage connection in response to the second signal if the overvoltage condition is not detected.  
         [0008]     According to another exemplary embodiment, an overvoltage protection device includes means for detecting whether an overvoltage condition is present with respect to a phase conductor and a neutral conductor of a voltage source coupled to a disconnect circuit of an overvoltage protection device. The overvoltage protection device also includes means for providing a first signal to a microprocessor circuit in communication with the disconnect device indicating whether the overvoltage condition is detected. The overvoltage protection device also includes means for disconnecting the phase conductor and the neutral conductor from an output voltage connection coupled to the disconnect circuit in response to a second signal from the microprocessor circuit if the overvoltage condition is detected, and means for connecting the phase conductor and the neutral conductor to the output voltage connection in response to the second signal if the overvoltage condition is not detected.  
         [0009]     Other features and advantages of the present invention will become apparent from the following detailed description and accompanying drawings. It should be understood, however, that the detailed description and specific examples are given by way of illustration and not limitation. Many modifications and changes within the scope of the present invention may be made without departing from the spirit thereof, and the invention includes all such modifications.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     The exemplary embodiments will hereafter be described with reference to the accompanying drawings, wherein like numerals depict like elements, and:  
         [0011]      FIG. 1  is a diagram schematically illustrating an overvoltage protection device according to an exemplary embodiment;  
         [0012]      FIG. 2  is a diagram schematically illustrating the disconnect circuit of  FIG. 1  according to an exemplary embodiment;  
         [0013]      FIG. 3  is an annotated wiring diagram schematically illustrating the overvoltage protection device of  FIG. 1  in detail according to an exemplary embodiment;  
         [0014]      FIG. 4  is a block diagram schematically illustrating an embodiment of the overvoltage protection device shown in  FIG. 3 ; and  
         [0015]      FIG. 5  is an annotated diagram schematically illustrating the disconnect circuit of  FIG. 1  and  FIG. 2  in detail according to an exemplary embodiment. 
     
    
     DETAILED DESCRIPTION  
       [0016]     In the following description, for the purposes of explanation, numerous details are set forth in order to provide a thorough understanding of the present invention. It will be evident to one skilled in the art, however, that the exemplary embodiments may be practiced without these specific details. In other instances, structures and device are shown in diagram form in order to facilitate description of the exemplary embodiments.  
         [0017]      FIG. 1  is a diagram schematically illustrating an overvoltage protection device  100  according to an exemplary embodiment. Overvoltage protection device  100  may be incorporated as part of an uninterruptible power supply (UPS) as shown in  FIG. 1 , a surge suppressor, or other similar devices. As illustrated in  FIG. 1 , overvoltage protection device  100  includes a voltage source input  110 , output voltage connections  120  and  122 , a transformer  130 , a battery  140 , a microprocessor circuit  150 , and a disconnect circuit  160 . Overvoltage protection device  100  is generally configured to provide protection against damage from overvoltage conditions in commercial, industrial, or residential electrical systems. Such overvoltage conditions may be caused by, for example, wiring errors or crossed wires in an electrical system, an open-neutral utility fault in an electrical distribution system, etc. More specifically, overvoltage protection device  100  is intended to protect both itself and any electrical equipment connected to it from damage from overvoltage conditions by automatically disconnecting and reconnecting the voltage source.  
         [0018]     Voltage source input  110  is configured to facilitate coupling of overvoltage protection device  100  to a voltage source (e.g., a removable plug, a “hard-wired” connection, etc.). For example, in the illustrated embodiment, voltage source input  110  is illustrated as a standard three-prong grounded plug for removably coupling overvoltage protection device  100  to an AC voltage source having a phase conductor  112 , a neutral conductor  114 , and a ground conductor  116 . According to an exemplary embodiment, overvoltage protection device  100  is configured to be coupled to an AC voltage source having a rated voltage of 120 volts RMS at 60 Hertz. According to various other embodiments, voltage sources of other types may be used. A circuit breaker  118  may also be provided in line with phase conductor  112 .  
         [0019]     Output voltage connections  120  and  122  are configured to facilitate connection of a load to overvoltage protection device  100 , such as a piece of electrical equipment powered by a voltage source to which overvoltage protection device  100  is coupled. For example, in the illustrated embodiment, output voltage connections  120  and  122  are illustrated as standard three-prong grounded outlets for removably coupling an AC load to overvoltage protection device  100 . According to various other embodiments, output voltage connections of other types may be used.  
         [0020]     Transformer  130  is configured to provide voltage regulation functions such that the voltage provided at output voltage connection  120  is maintained within a predetermined range around a nominal voltage. For example, according to an exemplary embodiment, transformer  130  is a 60 Hertz power transformer configured to regulate the voltage provided at output voltage connection  120  to within approximately 10% of a nominal AC output voltage of 120 volts RMS. According to various other embodiments, transformers of other types and ratings may be used. Battery  140  is configured to provide battery back-up power to a load connected to output voltage connection  120 , as well as to microprocessor circuit  150  and other components within overvoltage protection device  100  in the event of an overvoltage condition.  
         [0021]     Microprocessor circuit  150  includes microprocessor  152  and is coupled to output voltage connection  120 , transformer  130 , battery  140 , and disconnect circuit  160 . Microprocessor circuit  150  is configured to use conventional microprocessor control to control the overall operation of overvoltage protection device  100 . For example, microprocessor circuit  150  is configured to respond to a detected overvoltage condition by automatically disconnecting and reconnecting the voltage source from overvoltage protection device  100  in response to the overvoltage condition, and to switch output voltage connection  120  to battery back-up power during an overvoltage condition. According to an exemplary embodiment, microprocessor circuit  150  is also configured to provide automatic voltage regulation of the voltage at output voltage connection  120  (e.g., using transformer  130 , etc.).  
         [0022]     Disconnect circuit  160  is coupled to voltage source input  110 , output voltage connection  122 , and microprocessor circuit  150 . Disconnect circuit  160  is configured to detect an overvoltage condition at voltage source input  110 , and to provide a signal to microprocessor circuit  150  indicating the overvoltage condition. Disconnect circuit  160  is also configured to respond to a signal from microprocessor circuit  150  by disconnecting or reconnecting the voltage source from overvoltage protection device  100  in response to an overvoltage condition.  
         [0023]      FIG. 2  is a diagram schematically illustrating disconnect circuit  160  according to an exemplary embodiment. In the illustrated embodiment, disconnect circuit  160  includes a voltage detection circuit  210 , an auxiliary power circuit  220 , a switch control circuit  230 , a switch control circuit  240 , a switch control circuit  250 , and surge suppressors  260 . Disconnect circuit  160  is coupled to phase conductor  112 , neutral conductor  114 , and ground conductor  116  as shown in  FIG. 2 . Disconnect circuit  160  is also coupled to output voltage connection  122  at nodes  261  and  262 . Disconnect circuit  160  is coupled to microprocessor circuit  150  via a connector  263 .  
         [0024]     The connection between neutral conductor  114  and disconnect circuit  160  is coupled to a neutral reference  264  (indicated by an enclosed triangular symbol in  FIG. 2 ), which is also used as a neutral reference for voltage detection circuit  210  and auxiliary power circuit  220 . Disconnect circuit  160  also includes a secondary ground reference  265  (indicated by triangular symbol comprising horizontal lines in  FIG. 2 ) that is electrically isolated from neutral reference  264 . Secondary ground reference  265  is used as a ground reference for switch control circuit  230 , switch control circuit  240 , and switch control circuit  250 , as well as for microprocessor circuit  150 . Disconnect circuit  160  utilizes electrically isolated neutral reference  264  and secondary ground reference  265  in order to allow microprocessor circuit  150  to remain powered and to continue to respond to voltage detection circuit  210  during an overvoltage condition as will be described below.  
         [0025]     Voltage detection circuit  210  is configured to monitor the voltage across phase conductor  112  and neutral conductor  114  (i.e., neutral reference  264 ) in order to detect the presence or absence of an overvoltage condition as a function of a predetermined voltage threshold. For example, according to an exemplary embodiment, voltage detection circuit  210  is configured to monitor a nominal AC voltage of 120 volts RMS across phase conductor  112  and neutral conductor  114  in order to detect an overvoltage of approximately 15 percent greater than the nominal voltage. Switches  212  and  214  in voltage detection circuit  210  respond to the voltage across phase conductor  112  and neutral conductor  114  by switching optical isolation switch  216  either ON or OFF based on the detected presence or absence of an overvoltage condition (i.e., a voltage greater than the predetermined threshold). Accordingly, optical coupler  216  provides a signal to microprocessor circuit  150  indicating the presence or absence of an overvoltage condition. Optical coupler  216  also maintains electrical isolation between voltage detection circuit  210  and microprocessor circuit  150  in order to allow microprocessor circuit  150  to remain powered and to continue to respond to voltage detection circuit  210  during an overvoltage condition.  
         [0026]     Auxiliary power circuit  220  is configured to continuously provide power to voltage detection circuit  210  at node  222  (e.g., a DC voltage of approximately 12 volts) such that voltage detection circuit  210  may monitor the voltage across phase conductor  112  and neutral conductor  114 . Auxiliary power circuit  220  includes a voltage regulator  224 . Voltage regulator  224  may be any voltage regulator having an input voltage range suitable for continuous operation during both the presence and absence of an overvoltage condition.  
         [0027]     Switch control circuit  230 , switch control circuit  240 , and switch control circuit  250  are configured to open or close a switched device in response to a signal from microprocessor circuit  150  such that phase conductor  112  and neutral conductor  114  may be disconnected from or reconnected to overvoltage protection device  100  in response to the presence or absence of an overvoltage condition. For example, in the illustrated embodiment, switch control circuit  230  includes a relay coil  232  configured to open or close a relay contact  234  in response to a signal from microprocessor circuit  150  such that neutral conductor  114  may be disconnected from or reconnected to overvoltage protection device  100  in response to the presence or absence of an overvoltage condition. Similarly, switch control circuit  240  and switch control circuit  250  include respective relay coils  242  and  252  configured to open or close respective relay contacts  244  and  254  in response to a signal from microprocessor circuit  150  such that phase conductor  112  may be disconnected from or reconnected to overvoltage protection device  100  in response to the presence or absence of an overvoltage condition.  
         [0028]     Surge suppressors  260  are configured to provide protection from transient voltage surges at voltage source input  110 . Surge suppressors  260  may be any suitable type of surge suppressor component. According to an exemplary embodiment, surge suppressors  260  are metal-oxide-varistors (MOVs). Surge suppressors  260  are positioned between voltage source input  110  and output voltage connections  120  and  122  in order to provide protection from transient voltage surges at voltage source input  110 . Surge suppressors  260  are also separated from voltage source input  110  by switches controlled by switch control circuit  230 , switch control circuit  240 , and switch control circuit  250 . For example, as shown in  FIG. 2 , surge suppressors  260  are located within disconnect circuit  160  such that they are separated from phase conductor  112  and neutral conductor  114  by relay contacts  234 ,  244 , and  254  respectively controlled by switch control circuit  230 , switch control circuit  240 , and switch control circuit  250 . Accordingly, surge suppressors  260  are protected from damage from an overvoltage condition when the switches controlled by switch control circuit  230 , switch control circuit  240 , and switch control circuit  250  are opened in response to a signal from microprocessor circuit  150  such that phase conductor  112  and neutral conductor  114  are disconnected.  
         [0029]     The operation of overvoltage protection device  100  will now be described with reference to  FIG. 1  and  FIG. 2 . Voltage detection circuit  210  is powered by auxiliary power circuit  220  and monitors the voltage across phase conductor  112  and neutral conductor  114  in order to detect the presence or absence of an overvoltage condition as a function of a predetermined voltage threshold. Switches  212  and  214  in voltage detection circuit  210  respond to the voltage across phase conductor  112  and neutral conductor  114  by switching optical isolation switch  216  either ON or OFF based on the detected presence or absence of an overvoltage condition (i.e., a voltage greater than the predetermined threshold). Optical isolation switch  216  provides a signal to microprocessor circuit  150  indicating the presence or absence of an overvoltage condition. When no overvoltage condition is detected, microprocessor circuit  150  provides signals to switch control circuit  230 , switch control circuit  240 , and switch control circuit  250  so that their respective switches remain closed. Phase conductor  112  and neutral conductor  114  are connected to disconnect circuit  160  via these switches so that power from voltage source input  110  is provided at output voltage connection  120 .  
         [0030]     When the voltage across phase conductor  112  and neutral conductor  114  crosses the predetermined threshold, switches  212  and  214  in voltage detection circuit  210  respond by switching optical isolation switch  216  such that optical isolation switch  216  provides a signal to microprocessor circuit  150  indicating the presence of the overvoltage condition. In response to the detected overvoltage condition, microprocessor circuit  150  provides signals to switch control circuit  230 , switch control circuit  240 , and switch control circuit  250  so that their respective switches are opened. Phase conductor  112  and neutral conductor  114  are disconnected from disconnect circuit  160  via these switches so that power from voltage source input  110  is no longer provided at output voltage connections  120  and  122 . Instead, microprocessor circuit  150  causes power from battery  140  to be provided at output voltage connections  120  and  122 . According to an exemplary embodiment, overvoltage protection device  100  is configured to respond to a detected overvoltage condition by opening the switches controlled by switch control circuit  230 , switch control circuit  240 , and switch control circuit  250  within approximately one half of an AC voltage cycle once the overvoltage condition is detected. According to another exemplary embodiment, the overvoltage protection device may be configured to respond at another speed suited for use with the intended loads.  
         [0031]     During the detected overvoltage condition, phase conductor  112  remains connected to voltage detection circuit  210  and auxiliary power circuit  220  such that auxiliary power circuit  220  may continue to provide power to voltage detection circuit  210 , and so that voltage detection circuit  210  may continue to monitor the voltage across phase conductor  112  and neutral conductor  114 . Battery power is used to power microprocessor circuit  150 . Electrically isolated neutral reference  264  and secondary ground reference  265  allow microprocessor circuit  150  to remain powered and to continue to respond to voltage detection circuit  210  during the overvoltage condition. Optical coupler  216  also maintains electrical isolation between voltage detection circuit  210  and microprocessor circuit  150  while providing the signal indicating the presence of the overvoltage condition in order to allow microprocessor circuit  150  to remain powered and to continue to respond to voltage detection circuit  210  during the overvoltage condition.  
         [0032]     When the overvoltage condition is no longer detected by voltage detection circuit  210 , overvoltage protection device  100  is automatically reset to provide power from voltage source input  110  at output voltage connections  120  and  122 . Optical isolation switch  216  provides a signal to microprocessor circuit  150  indicating that the overvoltage condition is no longer present. In response, microprocessor circuit  150  provides signals to switch control circuit  230 , switch control circuit  240 , and switch control circuit  250  so that their respective switches are closed. Phase conductor  112  and neutral conductor  114  are reconnected to disconnect circuit  160  via these switches so that power from voltage source input  110  is again provided at output voltage connections  120  and  122 .  
         [0033]      FIG. 3  is an annotated wiring diagram schematically illustrating overvoltage protection device  100  in detail according to an exemplary embodiment.  FIG. 4  is a block diagram schematically illustrating an embodiment of overvoltage protection device  100  shown in  FIG. 3  in a more simplified manner. The embodiment of the overvoltage protection device shown in  FIGS. 3 and 4  is generally configured to implement the operation of overvoltage protection device  100  as described above with reference to  FIG. 1  and  FIG. 2 . The microprocessor circuit  150  shown in  FIGS. 3 and 4  implements microprocessor control techniques of a conventional type and is preferably configured to respond to a detected overvoltage condition within approximately one half of an AC voltage cycle once the overvoltage condition is detected.  FIG. 5  is an annotated diagram, including exemplary component values, that schematically illustrates disconnect circuit  160  in detail according to an exemplary embodiment.  
         [0034]     The overvoltage protection device as described herein thus provides improved protection for both itself and any connected loads during a detected overvoltage condition. The overvoltage protection device provides a complete disconnect by disconnecting both the phase and neutral conductors during the detected overvoltage condition, which prevents voltage surges from routing over the neutral and ground conductors. The optical coupler circuit in the overvoltage protection device allows the microprocessor circuit to remain electrically isolated during the overvoltage condition such that it may continue to monitor the input voltage of the voltage source and automatically reconnect the phase and neutral conductors once the overvoltage condition is no longer detected. The surge suppressors in the overvoltage protection device are also protected during an overvoltage condition, which may reduce or prevent damage to the overvoltage protection device, as well as reduce or prevent electrical fire hazards. The overvoltage device may also provide a quicker response and reduce exposure to a detected overvoltage condition by disconnecting both the phase and neutral conductors within approximately one half of an AC voltage cycle once the overvoltage condition is detected.  
         [0035]     It is important to note that the construction and arrangement of the elements of the overvoltage protection device as shown in the exemplary embodiments is illustrative only. Although only a few embodiments of the present inventions have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible without materially departing from the novel teachings and advantages of the subject matter recited. Accordingly, all such modifications are intended to be included within the scope of the present inventions. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. Any means-plus-function clause is intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. Other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the preferred and other exemplary embodiments without departing from the spirit of the present invention.