Abstract:
A low let-through voltage surge suppression or protection circuit for protecting hardware or equipment from electrical surges. During operation when no surge condition is present, the circuit allows propagation of signals from a source to a load along a signal path. When a surge is present, the circuit senses and diverts the surge away from the signal path, utilizing common mode and/or differential mode surge protection. An electronic filter is connected in parallel with surge suppression circuit elements for reducing the let through voltage that would otherwise propagate and require a higher power surge suppression circuit element to mitigate. Cascading multiple electronic filters in parallel with surge suppression circuit elements further reduces voltage let through.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit and priority of U.S. Provisional Application No. 61/597,589, entitled Reduced Let Through Voltage Transient Protection or Suppression Circuit, filed on Feb. 10, 2012, the entire contents of which are hereby incorporated by reference herein. 
    
    
     BACKGROUND 
     1. Field 
     The present disclosure relates generally to surge protection circuits and improvements thereof. More particularly, the present disclosure relates to surge protection circuits with reduced voltage let through and improvements thereof. 
     2. Description of the Related Art 
     Communications equipment, computers, home stereo amplifiers, televisions and other electronic devices are increasingly manufactured using a variety of electronic components that are vulnerable to damage from electrical energy surges. Surge variations in power and transmission line voltages, as well as noise, can change the operating frequency range of connected equipment and severely damage or destroy electronic devices. Electronic devices impacted by these surge conditions can be very expensive to repair or replace. Therefore, a cost effective way to protect these devices and components from power surges is needed. 
     Surge protectors help defend electronic equipment from damage due to the large variations in the current and voltage resulting from lightning strikes, switching surges, transients, noise, incorrect connections or other abnormal conditions or malfunctions that travel across power or transmission lines. As the number of electronic systems and equipment increase through both commercial and industrial society, the need for adequate and efficient protection from power surges becomes ever more important. A malfunctioning system or piece of equipment due to an unexpected or unintended surge of electrical power runs the risk of extensive monetary damage to the system or equipment and can even impact human safety. In an effort to reduce these risks, protection circuits or devices have been incorporated as part of or connectible to electrical systems or equipment in order to prevent the propagation of power surges through the electronics or other electrical equipment. 
     Circuit elements such as silicon avalanche diodes (SADs), metal oxide varistors (MOVs), Gas Discharge Tubes (GDTs) and other non-linear circuit components have been used for diverting a surge above a predetermined threshold from a signal line. However, conventional protection circuits can be extremely costly as the power dissipation requirements for a given system increase. Such components can be prohibitively expensive for many applications, particularly when the components must be capable of withstanding significant amounts of voltage and current upon conduction of an overcurrent or overvoltage. Conventional avalanche suppressors produce significant noise and glitches during the avalanche process before reaching a full conduction mode which can upset or damage sensitive protected equipment. Conventional GDT technologies are slow in response time due to the gas ionization/excitation process that is required in order for the energy discharge to occur, and thus they can allow very high let through voltages to propagate to the protected equipment. Similarly, conventional MOV technologies have high parasitic inductances and capacitances in the package causing the slow response time. This let through voltage can be extremely harmful to equipment if left unmitigated and adds additional expense to surge protection circuitry since higher rated surge components must be utilized. 
     Therefore, a surge protection system or circuit is desirable that can reduce the let through voltage to a minimal level when compared to conventional circuit protection technologies and thereby provide a lower clamping voltage with better filtering of surge signals in order to efficiently prevent the propagation of overvoltages or overcurrents to protected systems or hardware. The surge protection system or circuit would also desirably reduce the cost of such protection circuitry due to the reduction of the let through voltage remnant. In addition, the surge protection system or circuit would desirably be capable of easy scalability to a variety of surge protection or suppression power requirements or filtering needs. 
     SUMMARY 
     An apparatus and method for protecting against a surge condition in an electric circuit by conducting the surge along a signal pathway and reducing the let through voltage that propagates through the remainder of the circuit due to the surge condition. The surge protection apparatus may provide a lower clamping voltage and a better filter for various transient threats. In one implementation, a low let-through voltage surge suppression or protection apparatus may include a housing defining a cavity therein, a first signal port connected to the housing, a second signal port connected to the housing and a ground connection connected to the housing. A first surge protection filtering device is electrically connected between the first signal port and the second signal port for reducing a let through voltage, the first surge protection filtering device including a first silicon avalanche diode, a first capacitor connected to the first silicon avalanche diode and a first resistor connected to the first silicon avalanche diode and the first capacitor. A first surge element is electrically connected between the first signal port and the second signal port in parallel with the first surge protection filtering device. A second surge protection filtering device is electrically connected between the first signal port and the ground connection for reducing a let through voltage, the second surge protection filtering device including a second silicon avalanche diode, a second capacitor connected to the second silicon avalanche diode and a second resistor connected to the second silicon avalanche diode and the second capacitor. A second surge element is electrically connected between the first signal port and the ground connection in parallel with the second surge protection filtering device. A third surge protection filtering device is electrically connected between the second signal port and the ground connection for reducing a let through voltage, the third surge protection filtering device including a third silicon avalanche diode, a third capacitor connected to the third silicon avalanche diode and a third resistor connected to the third silicon avalanche diode and the third capacitor. A third surge element is electrically connected between the second signal port and the ground connection in parallel with the third surge protection filtering device. 
     In another implementation, a low let-through voltage surge suppression or protection apparatus may include a housing defining a cavity therein, a first input port connected to the housing, a second input port connected to the housing, a first output port connected to the housing, a second output port connected to the housing, a first inductor electrically connected between the first input port and the first output port, a second inductor electrically connected between the second input port and the second output port and a ground port connected to the housing. A first surge protection filtering device is electrically connected between the first input port and the second input port for reducing a let through voltage and a first surge element is electrically connected between the first input port and the second input port in parallel with the first surge protection filtering device. A second surge protection filtering device is electrically connected between the first input port and the ground port for reducing a let through voltage and a second surge element is electrically connected between the first input port and the ground port in parallel with the second surge protection filtering device. A third surge protection filtering device is electrically connected between the first output port and the ground port for reducing a let through voltage and a third surge element is electrically connected between the first output port and the ground port in parallel with the third surge protection filtering device. A fourth surge protection filtering device is electrically connected between the second input port and the ground port for reducing a let through voltage and a fourth surge element is electrically connected between the second input port and the ground port in parallel with the fourth surge protection filtering device. A fifth surge protection filtering device is electrically connected between the second output port and the ground port for reducing a let through voltage and a fifth surge element is electrically connected between the second output port and the ground port in parallel with the fifth surge protection filtering device. A sixth surge protection filtering device is electrically connected between the first output port and the second output port for reducing a let through voltage and a sixth surge element is electrically connected between the first output port and the second output port in parallel with the sixth surge protection filtering device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other systems, methods, features, and advantages of the present disclosure will be or will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the present disclosure, and be protected by the accompanying claims. Component parts shown in the drawings are not necessarily to scale, and may be exaggerated to better illustrate the important features of the present disclosure. In the drawings, like reference numerals designate like parts throughout the different views, wherein: 
         FIG. 1  is a schematic circuit diagram of an advanced transient avalanche charger (ATAC) filter as a parallel element for dissipating a surge in an electric circuit in accordance with an embodiment of the present invention; 
         FIG. 2A  is a schematic circuit diagram of a surge protection circuit utilizing a plurality of ATAC filters of  FIG. 1  in accordance with an embodiment of the present invention; 
         FIG. 2B  is a schematic circuit diagram of a two port network surge protection circuit utilizing a plurality of ATAC filters of  FIG. 1  in accordance with an embodiment of the present invention; 
         FIG. 3A  is a plot of the current through an ATAC filter and the voltage let-through of the ATAC filter in accordance with an embodiment of the present invention; 
         FIG. 3B  is a plot of the current through a Silicon Avalanche Diode (SAD) and the voltage let-through of the SAD in accordance with an embodiment of the present invention; 
         FIG. 3C  is a plot of the current through a Metal Oxide Varistor (MOV) and the voltage let-through of the MOV in accordance with an embodiment of the present invention; 
         FIG. 3D  is a plot of the current through a Gas Discharge Tube (GDT) and the voltage let-through of the GDT in accordance with an embodiment of the present invention; 
         FIG. 4A  is a disassembled front perspective view of a surge protection device incorporating an ATAC filter in accordance with an embodiment of the present invention; and 
         FIG. 4B  is a disassembled rear perspective view of the surge protection device of  FIG. 4A  incorporating an ATAC filter in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , a schematic circuit diagram of an advanced transient avalanche charger (ATAC) filter  100  is shown. The ATAC filter  100  operates to reduce the let through voltage when encountering a surge condition, especially when compared to traditional or conventional surge suppression or protection techniques connected in parallel. The ATAC filter  100  is a time domain notch filter and includes a silicon avalanche diode (SAD)  110 , and a Resistor-Capacitor (RC) circuit  160 . The SAD  110  has a first terminal  112  and a second terminal  114 . The RC circuit  160  includes a resistor  120  and a capacitor  130 . The resistor  120  has a first terminal  122  and a second terminal  124 . The capacitor  130  also has a first terminal  132  and a second terminal  134 . In  FIG. 1 , the RC circuit  160  is a parallel RC circuit, having the resistor  120  and the capacitor  130  connected in parallel. 
     The ATAC filter  100  is formed by a series combination of the SAD  110  with the RC circuit  150 , as shown. In other words, the second terminal  114  of the SAD  110  is electrically connected to the first terminal  122  of the resistor  120  and the first terminal  132  of the capacitor  130 . The second terminal  124  of the resistor  120  is electrically connected to the second terminal  134  of the capacitor  130 . The first terminal  112  of the SAD  110  may be electrically connected to a signal line  102  or other form of input port and the second terminals ( 124 ,  134 ) of the resistor and capacitor, respectively, may be electrically connected to a ground  140  through a second SAD  160 . Thus, upon encountering a surge present on the signal line  102 , at least a portion of the surge voltage or current is dissipated through the ATAC filter  100  to ground  140  with reduced let through energy, thereby aiding in the protection of any electrical systems or equipment that may be connected to the ATAC filter  100  along the signal line  102 . 
     The ATAC filter  100  significantly reduces the let through voltage and associated current (e.g., by half) of a surge propagating on the signal line  102  when compared to conventional surge protection elements or schemes and provides a low clamping voltage in order to more efficiently protect any sensitive connected equipment from all types of transient threats. When a surge is introduced along the signal line  102  to which the ATAC filter  100  is connected, the SAD  110  begins to conduct in order to divert at least some of the surge voltage and/or current off of the signal line  102  to the ground  140 . 
     In a conventional surge protection circuit utilizing conventional surge diversion elements, the let through voltage of such surge diversion elements would continue to propagate along the signal line  102  and potentially cause damage to any connected electrical systems or equipment. The ATAC filter  100  is capable of quickly diverting more current to ground  140  and with less high frequency noise due to the resistor  120  and capacitor  130  connections. Thus, the ATAC filter  100  quickly chops out the surge current by building it across the capacitor  130  instead of permitting remnants to flow along the signal line  102 . Subsequent surge elements in parallel may thus encounter lower surge energy levels and thus have lower power ratings than might otherwise be necessary. 
     After the surge event, the capacitor  130  may be charged to its full potential. The resistor  120  acts as a bleeding resistor to safely discharge the capacitor  130  without propagating the surge current into the signal line  102 . 
     A second SAD  160  is connected in series between the RC circuit  150  and the ground  140 . The second SAD  160  functions similar to the SAD  110  to provide protection against bidirectional surge events. 
     In an alternative implementation, different surge diverting or protection elements (e.g., metal oxide varistors (MOVs), gas discharge tubes (GDTs), etc.) may be used in place of or in addition to the SADs  110  and/or  160  of the ATAC filter  100  to provide varying surge suppression characteristics for a desired design. Because the ATAC filter  100  utilizes the protection elements connected in series, the protection elements can be configured or customized for a desired let-through voltage level. Furthermore, for systems or equipment that require higher surge current handling or lower voltage clamping, a plurality of ATAC filters  100  can be cascaded in parallel with each other. Each cascaded ATAC filter  100  stage thus reduces the let through energy further from the previous ATAC filter  100  stage. In this manner, less expensive surge protection elements may be utilized in a given surge protection circuit since the let through voltage is significantly reduced. Such a configuration may permit surge protection on previously prohibitively expensive systems that might encounter very high power surges. 
     Turning next to  FIG. 2A , a surge protection circuit  200  is shown utilizing a plurality of ATAC filters which may be the same or similar to the ATAC filter previously described for  FIG. 1 . The surge protection circuit  200  operates to protect any connected electrical equipment from a surge condition sensed by the surge protection circuit  200 . The surge protection circuit  200  includes a first signal port  201 , a second signal port  202  and a ground connection  204 . The first signal port  201  and the second signal port  202  may be connected in a parallel configuration with an electrical system so that the electrical system is protected from a surge condition present upon a signal line connected to either the first signal port  201  or the second signal port  202 . Thus, upon the presence of a surge at either the first signal port  201  or the second signal port  202 , a number of different electrical components, such as capacitors, resistors, diodes, and surge elements operate to aid in preventing the propagation of such a surge from continuing along the signal lines to cause damage to the connected system, as described in more detail herein. For illustrative purposes, the surge protection circuit  200  will be described with reference to such capacitor, resistor, diode and surge elements, but it is not required that the exact circuit elements described be used in the present disclosure. Thus, the capacitors, resistors, diodes and surge elements are merely used to illustrate an implementation of the disclosure and not to limit the present disclosure. 
     The surge protection circuit  200  may be implemented as a surge protection or suppression device. In one implementation, the surge protection circuit  200  may be formed as part of or included within a housing or other enclosure for allowing a user to physically connect the surge protection or suppression device to a system of the user. The enclosure may have a cavity contained or formed therein for placement of the various circuit elements of the surge protection circuit  200 , either connected to a printed circuit board secured within the cavity or otherwise fastened within the enclosure. The first and second signal ports ( 201 ,  202 ) may be configured to mate or otherwise interface with signal carrying conductors, for example, coaxial cables. 
     By electrically connecting the surge protection circuit  200  in parallel with a system to be protected, an electrical surge that could otherwise damage or destroy the connected system will instead be dissipated through the surge protection circuit  200 , as discussed in greater detail herein. The surge protection circuit  200  incorporates both common mode and differential mode surge protection between the first signal port  201 , the second signal port  202  and the ground connection  204 . The ground connection  204  may be a signal line configured to be connected to an exterior ground via a connector port or may be incorporated as part of an exterior housing of a surge protection device incorporating the surge protection circuit  200 . 
     Turning more specifically to the various components used in the surge protection circuit  200 , three ATAC filters ( 210 ,  220 ,  230 ) are provided. The first ATAC filter  210  is electrically connected between the first signal port  201  and the second signal port  202 . The first ATAC filter includes a first SAD  211 , a second SAD  214 , and a first resistor  212  connected in parallel with a first capacitor  213 . The second ATAC filter  220  is electrically connected between the first signal port  201  and the ground connection  204 . The second ATAC filter  220  includes a third SAD  221 , a fourth SAD  224 , and a second resistor  222  connected in parallel with a second capacitor  223 . The third ATAC filter  230  is electrically connected between the second signal port  202  and the ground connection  204 . The third ATAC filter  230  includes a fifth SAD  231 , a sixth SAD  234 , and a third resistor  232  connected in parallel with a third capacitor  233 . 
     The surge protection circuit  200  also includes a set  240  of surge elements for dissipating a surge present at either the first signal port  201  or the second signal port  202 . A first surge element  241  is electrically connected between the first signal port  201  and the second signal port  202 , in parallel with the first ATAC filter  210 . A second surge element  242  is electrically connected between the first signal port  201  and the ground connection  204 , in parallel with the second ATAC filter  220 . A third surge element  243  is electrically connected between the second signal port  202  and the ground connection  204 , in parallel with the third ATAC filter  230 . Thus, the ATAC filters ( 210 ,  220 ,  230 ) operate to substantially reduce the let through voltage of a surge condition at the first signal port  201  or the second signal port  202  and coordinate with the surge element ( 241 ,  242 ,  243 ) in parallel therewith to efficiently dissipate a surge before it can encounter any connected systems or equipment. 
     Each of the surge elements ( 241 ,  242 ,  243 ) may be any of a variety of surge diverting or conducting components, such as SADs, MOVs, GDTs, or other non-linear circuit elements. Different surge elements may provide varying surge dissipation characteristics. The inclusion of the ATAC filters ( 210 ,  220 ,  230 ) in parallel with the surge elements ( 241 ,  242 ,  243 ) reduces the let-through energy seen by the surge elements ( 241 ,  242 ,  243 ), thus permitting lower rated and potentially fewer surge elements to be needed for a given circuit. In an alternative implementation, additional ATAC filters may be provided in parallel with any of the first ATAC filter  210 , the second ATAC filter  220  or the third ATAC filter  230  to further reduce the let through voltage. Such additional ATAC filters further reduce the let through surge energy for further surge reduction and cost savings. For example, a 10 kA surge may require 20 k Watts worth of silicon in a single SAD surge element to appropriately divert the surge. By cascading one or more ATAC filters in parallel, a SAD surge element with lower power requirements may be used or utilized at a cheaper cost. 
     Turning next to  FIG. 2B , a two-port network surge protection circuit  250  is shown utilizing a plurality of ATAC filters, which may be the same or similar to the ATAC filter previously described for  FIG. 1 . Generally, the surge protection circuit  250  may have certain structure and functional features that are similar to those of the surge protection circuit  200 , previously described for  FIG. 2A . Notwithstanding these similar features, the surge protection circuit  250  may be distinguished from the surge protection circuit  200  based primarily on its dual-port or differential configuration. 
     The surge protection circuit  250  includes a first input port  251 , a first output port  253 , a second input port  252  and a second output port  254 . In certain implementations, the surge protection circuit  250  may operate bi-directionally such that the input ports may act as output ports or vice versa. The surge protection circuit  250  operates to protect any connected electrical equipment connected at either the first output port  253  or the second output port  254  from a surge condition present at either the first input port  251  or the second input port  252 . Similarly, a surge at the first output port  253  or the second output port  254  may also be prevented from transmitting to any power supplies or other equipment connected at the first input port  251  or the second input port  252 . Instead, a surge sensed by the surge protection circuit  250  is diverted through a variety of electrical components, such as capacitors, resistors, diodes and other surge elements that operate to divert the surge before it can disrupt or cause damage any connected equipment, as discussed in greater detail herein. For illustrative purposes, the surge protection circuit  250  will be described with reference to such capacitors, resistors, diodes and surge elements, but it is not required that the exact circuit elements described be used in the present disclosure. Thus, the capacitors, resistors, diodes and surge elements are merely used to illustrate an implementation of the disclosure and not to limit the present disclosure. 
     Similar to the surge protection circuit  200 , the surge protection circuit  250  may also be implemented as a surge protection or suppression device including a housing or other enclosure for containing one or more electrical components mounted therein. The various electrical components may be mounted to the housing itself within a cavity of the housing or may be connected to a printed circuit board disposed within the cavity or otherwise secured with the housing. The input and output ports ( 251 ,  252 ,  253 ,  254 ) are connected to various electrical components and are configured to mate or otherwise interface with signal carrying conductors to facilitate connection with a user&#39;s system. 
     The surge protection circuit  250  includes a first inductor  255  connected along a signal pathway between the first input port  251  to the first output port  253 . Similarly, a second inductor  256  is connected along a signal pathway from the second input port  252  to the second output port  254 . The inductors ( 255 ,  256 ) help maintain isolation of the input ports ( 251 ,  252 ) from the output ports ( 253 ,  254 ) for surge signals that should instead desirably be conducted via various ATAC filters or surge elements, as described in greater detail herein. In addition, because the portion of the circuit to the left of the inductors ( 255 ,  256 ) (i.e., a first stage) is independent from the portion of the circuit to the right of the inductors (i.e., a second stage), the two stages of the surge protection circuit  250  can be coordinated for any given electrical application to control the clamping voltage during a surge event to a level that is nominally above, but very close to, the operating voltage of the electrical application. 
     The surge protection circuit  250  incorporates both common mode and differential mode surge protection between the first input port  251 , the second input port  252 , the first output port  253 , the second output port  254  and a ground or return connection  257 . The ground or return connection  257  may be a signal line configured to be connected to an exterior ground via a connection port connected to a housing or may be incorporated as part of an exterior housing of a surge protection device incorporating the surge protection circuit  250 . 
     Turning more specifically to the various components used in the surge protection circuit  250 , six ATAC filters ( 260 ,  265 ,  270 ,  275 ,  280 ,  285 ) are provided. The first two ATAC filters ( 260 ,  265 ) are provided between input and output ports, as described below. The first ATAC filter  260  is electrically connected between the first input port  251  and the second input port  252 . The first ATAC filter includes a first SAD  261 , a second SAD  264 , a first resistor  262 , and a first capacitor  263 . The second ATAC filter  265  is electrically connected between the first output port  253  and the second output port  254 . The second ATAC filter  265  includes a third SAD  266 , a fourth SAD  269 , and a second resistor  267 , and a second capacitor  268 . 
     The remaining four ATAC filters ( 270 ,  275 ,  280 ,  285 ) are provided between either input or output ports and ground, as described below. The third ATAC filter  270  is electrically connected between the first input port  251  and the ground connection  257 . The third ATAC filter  270  includes a fifth SAD  271 , a sixth SAD  274 , a third resistor  272 , and a third capacitor  273 . The fourth ATAC filter  275  is electrically connected between the first output port  253  and the ground connection  257 . The fourth ATAC filter  275  includes a seventh SAD  276 , an eighth SAD  279 , a fourth resistor  277 , and a fourth capacitor  278 . The fifth ATAC filter  280  is electrically connected between the second input port  252  and the ground connection  257 . The fifth ATAC filter  280  includes a ninth SAD  281 , a tenth SAD  284 , a fifth resistor  282 , and a fifth capacitor  283 . The sixth ATAC filter  285  is electrically connected between the second output port  254  and the ground connection  257 . The sixth ATAC filter  285  includes a eleventh SAD  286 , a twelfth SAD  289 , a sixth resistor  287 , and a sixth capacitor  288 . 
     The surge protection circuit  250  also includes two sets ( 290 ,  295 ) of surge elements for dissipating a surge present at any of the first input port  251 , the second input port  252 , the first output port  253  or the second output port  254 . A first surge element  292  is electrically connected between the first input port  251  and the second input port  252 , in parallel with the first ATAC filter  260 . A second surge element  297  is electrically connected between the first output port  253  and the second output port  254 , in parallel with the second ATAC filter  265 . A third surge element  291  is electrically connected between the first input port  251  and the ground connection  257 , in parallel with the third ATAC filter  270 . A fourth surge element  296  is electrically connected between the first output port  253  and the ground connection  257 , in parallel with the fourth ATAC filter  275 . A fifth surge element  293  is electrically connected between the second input port  252  and the ground connection  257 , in parallel with the fifth ATAC filter  280 . A sixth surge element  298  is electrically connected between the second output port  254  and the ground connection  257 , in parallel with the sixth ATAC filter  285 . Thus, the ATAC filters ( 260 ,  265 ,  270 ,  275 ,  280 ,  285 ) operate to substantially reduce the let through voltage of a surge condition at the first input port  251 , the second input port  252 , the first output port  253  or the second output port  254  and coordinate with the surge element ( 291 ,  292 ,  293 ,  294 ,  295 ,  296 ,  297 ,  298 ) in parallel therewith to efficiently dissipate a surge. 
     Each of the surge elements ( 291 ,  292 ,  293 ,  294 ,  295 ,  296 ,  297 ,  298 ) may be any of a variety of surge diverting or conducting components, such as SADs, MOVs, GDTs, or other non-linear circuit elements. Different surge elements may provide varying surge dissipation characteristics. In an alternative implementation, one or more of the sets ( 290 ,  295 ) of surge elements or one or more of the surge elements ( 291 ,  292 ,  293 ,  294 ,  295 ,  296 ,  297 ,  298 ) may not be needed, for example if surge protection is only needed on one of an input end or an output end of a network. An alternative implementation may utilize additional ATAC filters in parallel with any of the first ATAC filter  260 , the second ATAC filter  265 , the third ATAC filter  270 , the fourth ATAC filter  275 , the fifth ATAC filter  280  or the sixth ATAC filter  285  to further reduce the let through voltage. Similar to the previous discussion for  FIG. 2A , such additional ATAC filters may allow for surge protection at a lower cost, particularly for systems or equipment operating at higher voltage or current levels. 
     The surge protection circuits  200  or  250  described above may be modified or alternately designed with differing circuit element values or with different, additional, or fewer circuit elements to achieve the same or similar functionality. The surge protection circuits  200  or  250  may be designed with components to facilitate AC functionality or DC functionality. The surge protection circuits  200  or  250  may also be scaled for an application having any desired voltage or current operating levels. As such, the surge protection circuits  200  or  250  may be configured for ranges of typical or commonly expected surge levels or may be designed and constructed as a custom configuration to meet the requirements of a particular system or setup. 
     The circuit elements of the surge protection circuits  200  or  250  may be discrete elements positioned within an enclosure or housing and/or may be mounted or electrically connected with a printed circuit board. An enclosure used may have input and/or output ports for allowing user-installation of the circuit to their own systems or equipment. In certain implementations, the enclosure may be a connector, the various circuit elements integrated within the connector. 
     Turning now to  FIGS. 3A-3D , plots of the current and voltage let through are shown for a variety of surge suppression or protection devices.  FIGS. 3A-3D  depict 10 KA 8/20 μs surge performances. In  FIG. 3A , the plot  300  demonstrates the current and voltage characteristics for an ATAC filter (e.g., the current flowing through the ATAC filter.) As will be seen in later described plots for  FIGS. 3B-3D , the current waveform remains similar between the plots to facilitate a comparison of let through voltages for various surge protection techniques. Signal  304  shows a waveform of a let through voltage that propagates past the ATAC filter upon the current signal  302  flowing through the ATAC filter. As can be seen, the signal  304  has a peak voltage of only 142 volts. 
       FIG. 3B  shows a plot  320  of current and voltage let through, similar to  FIG. 3A , but instead utilizing a conventional SAD surge protection element without any ATAC filtering. The signal  322 , representing a current flowing through the SAD is similar to the signal  302  for  FIG. 3A . However, the signal  324 , representing the voltage let through of the SAD upon the current signal  322  flowing through the SAD, is a significantly higher voltage level of 236 volts. Thus, for similar current values, the ATAC filter response shown in  FIG. 3A  has resulted in roughly a 40% drop in peak surge voltage that is let through compared to a conventional SAD surge protection element. 
     Similarly,  FIG. 3C  shows a plot  340  of current and voltage let through, but utilizing a conventional MOV surge protection element without any ATAC filtering. The signal  342 , representing a current flowing through the MOV is again similar to the signal  302  for  FIG. 3A . However, the signal  344 , representing the voltage let through of the MOV upon the current signal  322  flowing through the MOV, is also a significantly higher voltage level of 372 volts. Thus, for similar current values, the ATAC filter response shown in  FIG. 3A  has resulted in roughly a 62% drop in peak surge voltage that is let through compared to a conventional MOV surge protection element. 
     Likewise,  FIG. 3D  shows a plot  360  of current and voltage let through, but utilizing a conventional GDT surge protection element without any ATAC filtering. The signal  362 , representing a current flowing through the GDT is also similar to the signal  302  for  FIG. 3A . However, the signal  364 , representing the voltage let through of the GDT upon the current signal  362  flowing through the GDT, is again a significantly higher voltage level of 346 volts. Thus, for similar current values, the ATAC filter response shown in  FIG. 3A  has resulted in roughly a 59% drop in peak surge voltage that is let through compared to a conventional GDT surge protection element. 
     To lower the let through voltage, all surge elements must be in full conducting modes before the peak of the surge event. For an 8/20 μs waveform for instance, the current (di/dt) peak is at 8 μs. A GDT, for example, may not turn on fast enough to divert the surge current at the peak of the surge event to ground, resulting in a higher let through voltage. A GDT is slow in response time due to the gas ionization/excitation process. The GDT response time may be further increased because of the low potential voltage across its terminals when connected in parallel with another surge element. An ATAC filter has a faster response time. 
       FIG. 4A  shows a disassembled front perspective view of a surge protection device  400  incorporating an ATAC filter. Similarly,  FIG. 4B  shows a disassembled rear perspective view of the surge protection device  400  incorporating an ATAC filter. In certain implementations, the surge protection device  400  may be configured to accommodate any of a variety of surge protection circuits, for example the surge protection circuits described for  FIG. 2A  or  2 B. With reference to both  FIGS. 4A and 4B , the surge protection device  400  includes an enclosure cover  410  having a plurality of openings  412  for facilitating connection to a base, as described in greater detail herein. The enclosure cover  410  defines a cavity within for the placement of surge protection circuit elements, such as an ATAC filter. 
     A printed circuit board (PCB)  420  fits within the cavity of the enclosure cover  410  and has a first surface and a second surface substantially parallel to the first surface. The printed circuit board is connected to conductive connection terminals ( 441 ,  442 ,  443 ,  444 ). These connection terminals ( 441 ,  442 ,  443 ,  444 ) are protruding conductive contacts that may be plugged into corresponding receptacles of a mother board or other device for mating the surge protection device  400  with a user&#39;s system or other hardware. The connection terminals ( 441 ,  442 ,  443 ,  444 ) may be disposed along a plane on one side of the PCB  420 . An alternative implementation may use greater or fewer connection terminals of the same or a different type and oriented in varying configurations. A plurality of capacitors ( 422 ,  424 ,  426 ) are connected to the first surface of the PCB  420  and are electrically connected, either directly or through other circuit elements, to one or more of the connection terminals ( 441 ,  442 ,  443 ,  444 ). In addition, a bridge rectifier element  428  is connected to the first surface of the PCB  420  for rectifying AC signals to DC. 
     On the second surface of the PCB  420 , a plurality of SAD elements ( 430 ,  432 ,  434 ) are connected to the PCB  420 . Electrical traces on the PCB  420  electrically connect certain of the SAD elements ( 430 ,  432 ,  434 ) to certain other circuit components on the PCB  420 , such as the capacitors ( 422 ,  424 ,  426 ), the bridge rectifier element  428  or the connection terminals ( 441 ,  442 ,  443 ,  444 ). By electrically connecting one or more of the SAD elements ( 430 ,  432 ,  434 ) with the capacitors ( 422 ,  424 ,  426 ), one or more ATAC filters may be formed for lowering the let through voltage of a surge signal entering the surge protection device  400 . A support base  450  is disposed adjacent to and contacting certain circuit elements or structural geometry of the PCB  420 . The connection terminals ( 441 ,  442 ,  443 ,  444 ) of the PCB  420  extend through a plurality of slots  452  in the support base  450  to facilitate external connection of the surge protection device  400 . The support base  450  includes a plurality of clips  454  disposed along a perimeter of the support base  450  that cooperate with the plurality of openings  412  of the cover enclosure  410  to form a secure and stable outer housing of the surge protection device  400 . The various protrusions and recessions of the support base  450  operate to safely keep the PCB  420  in place when the surge protection device  400  is being manipulated by a user, for example when plugging in or removing the surge protection device  400  from a backplane or motherboard. 
     Exemplary implementations of this disclosure have been disclosed in an illustrative style. Accordingly, the terminology employed throughout should be read in a non-limiting manner. Although minor modifications to the teachings herein will occur to those well versed in the art, it shall be understood that what is intended to be circumscribed within the scope of the patent warranted hereon are all such implementations that reasonably fall within the scope of the advancement to the art hereby contributed, and that that scope shall not be restricted, except in light of the appended claims and their equivalents.