Abstract:
Triac controlled dimmers and switches often employ a snubber circuit to prevent self-tripping and to reduce radio frequency emissions. Standard snubber circuits allow small amounts of AC current to reach the load even when the dimmer or switch is set to the off position, thereby causing unwanted illumination in certain high efficiency LED lighting. A load-side dynamic snubber circuit is provided for use in dimmers, switches, and similar applications which only activates the snubber circuit when the dimmer or switch is active, thereby preventing current from reaching the load when the dimmer or switch is in the off position.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    I. Field 
         [0002]    The present invention relates to an improved snubber circuit for use in certain electric switches and dimmers. 
         [0003]    II. Background 
         [0004]    In Triac controlled lamp dimmers, a snubber circuit is often used to prevent the Triac from self-triggering as well as to reduce emitted radio-frequency (RF) noise. Reduction of RF noise is of special concern where the snubber circuit is used across a relay switching heavy loads. Standard snubber circuits, such as those used in dimmers and switches, commonly consist of standard resistive and capacitive elements placed in parallel to the Triac or relay in question. However, these configurations allow a small amount of AC current to pass through and be present on the load even when the Triac or relay is de-energized. This current, although small, is sometimes enough to illuminate some high-efficiency LED lighting, despite the fact that the dimmer or switch is “off” and should not allow for illumination of said LED light. 
         [0005]    There is a need for an improved snubber circuit that prevents current from reaching a load even when the Triac or relay associated with said circuit is de-energized. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention meets this and other needs by providing, among other things, techniques for providing a load-side dynamic snubber circuit for use in various devices, including various dimmers and switches. 
         [0007]    An exemplary embodiment of the invention provides a switching device comprising a gate device, a snubber circuit, and a controller. In said embodiment, said gate device is connected in series with said snubber circuit, and said controller is connected to said gate device. Further, said controller is configured to send a first signal to said gate device when said switching device is in a first state, thereby causing said gate device to enter a first state, where said first state of said gate device allows electrical current to flow through said gate device and said snubber circuit. Additionally, said controller is configured to send a second signal to said gate device when said switching device is in a second state, thereby causing said gate device to enter a second state, where said second state of said gate device prevents electrical current from flowing through said gate device and said snubber circuit. 
         [0008]    In another exemplary embodiment, a switching device is provide comprising a first terminal and a second terminal, wherein said first terminal is configured to connect to an AC voltage source and said second terminal is configured to connect to a load. Said device further comprises a user interface, a gate device (where said gate device comprises a first terminal, a second terminal and a control terminal), a snubber circuit, and a controller, wherein said first terminal of said gate element is connected to said first terminal of said switching device, said second terminal of said gate element is connected to said snubber circuit, and said control terminal of said gate element is connected to said controller. In said embodiment, said controller is configured to monitor a state of said user interface, and said first terminal of said switching device, said gate element, said snubber circuit, and said second terminal of said switching device are connected in series. Furthermore, said controller is configured to send a first signal to said gate device when said user interface is in a first state, thereby causing said gate device to enter a first state, wherein said first state of said gate device allows electrical current to flow through said gate device and said snubber circuit to said load; and said controller is configured to send a second signal to said gate device when said user interface is in a second state, thereby causing said gate device to enter a second state, wherein said second state of said gate device prevents electrical current from flowing through said gate device and said snubber circuit to said load. 
         [0009]    In an exemplary embodiment, said switching device is a dimmer. In another exemplary embodiment, said switching device is a switch. 
         [0010]    The images in the drawings are simplified for illustrative purposes and are not depicted to scale. To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the Figures, except that suffixes may be added, when appropriate, to differentiate such elements. 
         [0011]    The appended drawings illustrate exemplary configurations of the invention and, as such, should not be considered as limiting the scope of the invention that may admit to other equally effective configurations. It is contemplated that features of one configuration may be beneficially incorporated in other configurations without further recitation. The above and other objects and features of the present invention will become apparent from the drawings, the description given herein, and the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    For a further understanding of the nature and objects of the present invention, reference should be had to the following description taken in conjunction with the accompanying drawings in which like parts are given like reference numerals. 
           [0013]      FIG. 1  illustrates a load-side dynamic snubber circuit implemented as part of a dimmer. 
           [0014]      FIG. 2  illustrates a load-side dynamic snubber circuit implemented as part of a switch. 
           [0015]      FIG. 3  illustrates a load-side dynamic snubber circuit implemented as part of a dimmer, where an opto-isolated MOSFET solid-state relay is used in lieu of a Triac. 
           [0016]      FIG. 4  illustrates a load-side dynamic snubber circuit implemented as part of a switch, where an opto-isolated MOSFET solid-state relay is used in lieu of a Triac. 
           [0017]      FIG. 5  illustrates a timing diagram graphically depicting the logic used to control a dimmer comprising a load-side dynamic snubber circuit. 
           [0018]      FIG. 6  illustrates a timing diagram graphically depicting the logic used to control a switch comprising a load-side dynamic snubber circuit. 
       
    
    
       [0019]    The images in the drawings are simplified for illustrative purposes and are not depicted to scale. Within the descriptions of the figures, similar elements are provided similar names and reference numerals as those of the previous figure(s). Where a later figure utilizes the same element or a similar element in a different context or with different functionality, the element is provided a different leading numeral representative of the figure number (e.g., 1xx for  FIG. 1  and 2xx for  FIG. 2 ). The specific numerals assigned to the elements are provided solely to aid in the description and are not meant to imply any limitations (structural or functional) on the invention. 
         [0020]    The appended drawings illustrate exemplary configurations of the invention and, as such, should not be considered as limiting the scope of the invention that may admit to other equally effective configurations. It is contemplated that features of one configuration may be beneficially incorporated in other configurations without further recitation. 
       DETAILED DESCRIPTION 
       [0021]    The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any configuration or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other configurations or designs. 
         [0022]    The present invention solves the problem of inadvertent current passing through to a load even when a dimmer or switch is de-energized by providing a load-side dynamic snubber circuit.  FIG. 1  shows an exemplary embodiment of the present invention implemented in a dimmer, wherein dimmer  100  includes a dynamic snubber circuit  101 . Dynamic snubber circuit  101  comprises a microprocessor-controlled Triac  110  in series with snubber circuit  115 , where snubber circuit  115  is comprised of resistor  120  connected in series with capacitor  125 . This arrangement allows for selective activation of snubber circuit  115 . 
         [0023]    More specifically, dimmer  100  comprises dynamic snubber control Triac  110 , wherein terminal  111  of Triac  110  is connected to node A (where node A is connected to AC voltage source  102 ), terminal  112  of Triac  110  is connected to a first terminal of resistor  120 , and gate  113  of Triac  110  is connected to node C. A second terminal of resistor  120 , which is connected in series with terminal  112  of Triac  110 , is connected to a first terminal of capacitor  125 ; and, a second terminal of capacitor  125  is connected to node B. In an exemplary embodiment, AC voltage source  102  is a typical residential 120 V AC power supply, resistor  120  has a resistive value of 1000Ω, and capacitor  125  has a capacitance of 0.01 μF. In the embodiment depicted in  FIG. 1 , node A is shown as being connected to “device ground” simply as a reference voltage and not to signify any connection to any external grounding point. 
         [0024]    Also in series with Triac  110 , resistor  120 , and capacitor  125  is inductive element  130 , wherein a first terminal of inductor  130  is connected to node B, and a second terminal of inductor  130  is connected to the switched load  105 . In an exemplary embodiment, inductor  130  has a value of 23 μH. 
         [0025]    Also connected with Triac  110  are resistors  135  and  140 , where a first terminal of resistor  135  is connected to node A, and a second terminal of resistor  135  is connected to node C; and, where a first terminal of resistor  140  is connected to node C and a second terminal of resistor  140  is connected to node F. Node C is also connected directly to gate terminal  113 . Node F is connected to output port  181  of microcontroller  180 . In an exemplary embodiment, resistor  135  has a value of 10,000Ω, resistor  140  has a value of 620Ω, and microcontroller  180  is a STM Microcontroller model STM8L1013T6. 
         [0026]    In parallel with dynamic snubber circuit  101  is main dimming Triac circuit  150 , comprising Triac  151 , Triac  152  and resistor  153 . Terminal  154  of Triac  151  is connected to node A, terminal  155  of Triac  151  is connected to node B, and gate terminal  156  of Triac  151  is connected to terminal  157  of Triac  152 . Terminal  158  of Triac  152  is connected to a first terminal of resistor  153 , and a second terminal of resistor  153  is connected to node B. In an exemplary embodiment, resistor  153  has a value of 200Ω. It would be understood to a person of skill in the art that main dimming Triac circuit  150  may be replaced by any comparable dimming circuit capable of limiting the amount of power delivered to a load based on the state of the dimmer input. 
         [0027]    Gate terminal  159  of Triac  152  is connected to node D, where node D is connected to a first terminal of resistor  162  and a first terminal of resistor  164 . A second terminal of resistor  162  is connected to node A, and a second terminal of resistor  164  is connected to output  182  of microcontroller  180 . In an alternative embodiment (not shown), Triac  151  is controlled by a microcontroller different from the microcontroller controlling Triac  110 . In an exemplary embodiment, resistor  162  has a value of 10,000Ω, and resistor  164  has a value of 330Ω. 
         [0028]    Dimmer  100  further comprises switches  170 ,  171 ,  172  and  173 , wherein said switches can be programmed to perform various functions. For example, in an exemplary embodiment, switch  170  is a hard on/off switch which bypasses the dimmer functionality. In another embodiment, switch  171  is a toggle which reverses the functionality of the dimmer (i.e., reversing the direction of brightness versus dimness controlled by a given manipulation of dimmer  100 ). In other embodiments, these switches may serve other functions; or, alternatively, said switches may be disabled or omitted from the device. 
         [0029]    Dimmer  100  further comprises zero-crossing detector  190 , the input of which is connected to the AC power system neutral, where said detector  190  detects when the AC power waveform has an amplitude of zero volts. In the embodiment shown in  FIG. 1 , the output of detector  190  is connected to input  183  of microcontroller  180 . Dimmer  100  further comprises internal DC power supply  195 . 
         [0030]    In an exemplary embodiment, dimmer  100  further comprises radio frequency transceiver  198 , which is connected to input/output port  184  of microcontroller  180  and which allows for radio frequency remote control of dimmer  100 . It is also understood that dimmer  100  includes a user interface (not shown) whereby a user can adjust the amount of power delivered to the load by dimmer  100 , where such user interface could be a knob, slider, toggle, or any digital equivalent which allows for variation in the amount of power allowed to pass through the dimmer  100  to load  105 . 
         [0031]      FIG. 2  shows an implementation of a dynamic snubber circuit in a microprocessor-controlled switch (as compared to the dimmer shown in  FIG. 1 ). Switch  200  is essentially identical to dimmer  100 , except that switch  200  lacks components comparable to main dimming Triac circuit  150 , and instead includes relay  250 . Just as in  FIG. 1 , dynamic snubber circuit  201  comprises a microprocessor-controlled Triac  210  in series with snubber circuit  215 , where snubber circuit  215  is comprised of resistor  220  connected in series with capacitor  225 . 
         [0032]    Specifically, switch  200  includes dynamic snubbing circuit  201 , which circuit comprises Triac  210 , wherein terminal  211  of Triac  210  is connected to node A (where node A is connected to AC voltage source  202 ), terminal  212  of Triac  210  is connected to a first terminal of resistor  220 , and gate  213  of Triac  210  is connected to node C. A second terminal of resistor  220 , which is connected in series with terminal  212  of Triac  210 , is connected to a first terminal of capacitor  225 ; and, a second terminal of capacitor  225  is connected to node B. In an exemplary embodiment, AC voltage source  202  is a typical residential 120 V AC power supply, resistor  220  has a resistive value of 1000Ω, and capacitor  225  has a capacitance of 0.01 μF. In the embodiment depicted in  FIG. 2 , node A is shown as being connected to “device ground” simply as a reference voltage, and not to signify any connection to any external grounding point. 
         [0033]    Also connected with Triac  210  are resistors  235  and  240 , where a first terminal of resistor  235  is connected to node A, and a second terminal of resistor  235  is connected to node C; and, where a first terminal of resistor  240  is connected to node C and a second terminal of resistor  240  is connected to microcontroller  280  at output port  282 . Node C is also connected directly to gate terminal  213 . In an exemplary embodiment, resistor  235  has a value of 10,000Ω, resistor  240  has a value of 620Ω, and microcontroller  280  is a STM Microcontroller model STM8L1013T6. 
         [0034]    Switch  200  further comprises relay  250 , where a first terminal  251  of relay  250  is connected to node B (which is also connected to switched load  205 ), a second terminal  252  of relay  250  is connected to node A, and activation coil  253  of relay  250  is connected to output  281  of microcontroller  280 . Note that particular output ports of the microcontroller shown in each embodiment described herein may vary from embodiment to embodiment, and it would be known to a person of skill in the art that the output ports of such a microcontroller are generally configurable. 
         [0035]    Switch  200  further comprises: switches  270 ,  271 ,  272  and  273  which are similar to switches  170 - 173  described above; zero-crossing detector  290 , which is similar to zero-crossing detector  190  described above; internal power supply  295 , which is similar to internal power supply  195  described above; and, radio frequency transceiver  298 , which is similar to radio frequency transceiver  198  described above. 
         [0036]      FIG. 3  shows an alternative embodiment of a dynamic snubber circuit implemented in a dimmer. Specifically, dimmer  300  is similar to dimmer  100 , except that instead of using a Triac (such as Triac  110 ) to dynamically activate snubber circuit  315 , dimmer  300  instead uses opto-isolated MOSFET solid-state relay  310 , where relay  310  is controlled by output  381  of controller  380 . 
         [0037]    Similarly,  FIG. 4  shows an alternative embodiment of a dynamic snubber circuit implemented in a switch. Specifically, switch  400  is similar to switch  200 , except that instead of using a Triac (such as Triac  210 ) to dynamically activate snubber circuit  415 , switch  400  instead uses opto-isolated MOSFET solid-state relay  410 , where relay  410  is controlled by output  481  of controller  480 . 
         [0038]      FIGS. 5 and 6  shown timing diagrams which graphically demonstrate the logic used by the microcontroller to control the dimmers and switches described above, respectively. 
         [0039]      FIG. 5  shows a timing diagram depicting logic associated with the operation of dimmers  100  and  300  (for the remainder of the description of  FIG. 5 ,  FIG. 1  will be referenced, but the description applies equally to the embodiment shown in  FIG. 3 ). Line  520  shows the 120 V AC line voltage, such as that provided by voltage source  102 . Demarcation line  505  shows the point in time where the dimmer is “activated” (for example, the dimmer is manipulated by a user, via a user interface, to activate load  105 ). Shaded areas  515  show the portion of the V AC cycle wherein the dimmer allows power to reach load  105 , thereby “dimming” the light provided by said load. Line  540  shows the output of zero-cross detector  190 , which is connected to microcontroller input  183 . Line  560  shows output  182  of microcontroller  180  which controls main dimming Triac circuit  150 . Finally, line  580  shows output  181  of microcontroller  180  which controls Triac  110 , thereby controlling dynamic snubber circuit  115 . 
         [0040]    Further referencing the logic depicted in  FIG. 5 , when dimmer  100  is in the “off” state (i.e., the load  105  should not receive any power and thus not illuminate), both the main switching Triac  151  and the dynamic snubber Triac  110  are in the “off” state (i.e., no current passes through either Triac). When dimmer  100  is switched to the “on” state, the dynamic snubber Triac  110  is switched “on” by the microprocessor at least one AC cycle (16 msec) prior to the start of the operation of Triac  151 . While dimmer  100  remains in the “on” state, the dynamic snubber Triac  110  remains “on”. When dimmer  100  is switched “off”, the dynamic snubber Triac  110  is switched “off” at least one AC cycle (16 msec) after Triac  151  in the “off” state. While not shown, in ah alternative embodiment, the microcontroller may also be configured to periodically energize the dynamic snubber Triac  110  for short periods of time (for example, 16 msec) in the event that inductive or capacitive loads trigger Triac  110  or Triac  151 . 
         [0041]      FIG. 6  shows a timing diagram depicting logic associated with the operation of switches  200  and  400  (for the remainder of the description of  FIG. 6 ,  FIG. 2  will be referenced, but the description applies equally to the embodiment shown in  FIG. 4 ). Line  620  shows the 120 V AC line voltage, such as that provided by voltage source  202 . Demarcation line  605  shows the point in time where the switch is “activated” (for example, the switch is manipulated by a user, via a user interface, to activate load  205 ). Shaded areas  615  show the portion of the V AC cycle wherein the switch allows power to reach load  205  (so, as opposed to dimmer  100 , switch  200  allows power to reach the load the entire time the switch is “on”). Line  660  shows output  281  of microcontroller  280  which controls relay  250 . Finally, line  680  shows output  282  of microcontroller  280  which controls Triac  210 , thereby controlling dynamic snubber circuit  215 . 
         [0042]    Further referencing the logic depicted in  FIG. 6 , when switch  200  is turned “on” or “off”, the dynamic snubber Triac  210  is turned on at least one AC cycle (16 msec) prior to the state change of relay  250 . Once the state of relay  250  has changed, either from on to off or vice-versa, the dynamic snubber Triac  210  is de-energized at least one AC cycle (16 msec) after relay  250  has finished changing state. 
         [0043]    For the purposes of this application, the term “gate element” means a Triac, an opto-isolated MOSFET solid-state relay, electromechanical relay, or any other device which can serve as a dynamic switch allowing or preventing the passage of electrical current along a given circuit path based on a control signal input to said device (where said control signal can be electrical, optical, or any other form of control signal regardless of the communication medium). 
         [0044]    For the purposes of this application, when components or nodes are referred to as being “connected” or “connected in series”, such connection may include one or more intervening components. 
         [0045]    In one or more exemplary configurations, one or more of the functions described may be implemented in hardware, software, firmware, or any combination thereof. 
         [0046]    The previous description of the disclosed configurations is provided to enable any person skilled in the art to make or use the disclosure. Various modifications to these configurations will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other configurations without departing from the spirit or scope of the disclosure. Thus, the disclosure is not intended to be limited to the configurations shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.