Patent Publication Number: US-8981656-B2

Title: Relamping circuit for fluorescent ballasts

Description:
FIELD OF THE INVENTION 
     The present disclosure relates to a lighting system and more particularly to a system and method for detecting relamping and igniting the new lamp. 
     BACKGROUND OF THE INVENTION 
     Fluorescent lamps include filaments or electrodes at each end of a glass tube, an ionizable gas, and a phosphor coating on the inside of the glass tube. When current is supplied to the filaments a voltage is induced ionizing the gas and forming an electric arc between the filaments. The electric arc generates a flow of electric current through the ionized gas causing electrons to be excited and producing light emissions. Typically, the filaments are coated with an emission mix to facilitate electron emission. The use of a ballast in a fluorescent lamp system extends the life of the lamps by preheating the filaments to mitigate the depletion of the emission mix coating. 
     A lamp reaches an end-of-life stage when the emission mix becomes depleted on a filament causing the lamp to draw more voltage to continue normal operation. This higher voltage results in an increase in lamp temperature which may damage the lamp or the lamp socket. A lamp at the end-of-life stage, can be replaced or, as it is sometimes technically called, relamped. 
     During relamping, the system can detect that the new lamp has been inserted. Conventionally, such detection has required that each lamp have a corresponding relamping detector and timing circuit. Including a separate relamping detector and timing circuit for each lamp creates extensive circuitry. Such circuitry requires a substantial footprint on a printed circuit board, a relatively large ballast, and adds to the complexity and cost of the circuitry. 
     In another conventional approach, all outputs of the relamping detectors are coupled to separate terminals of a timing circuit, which determines when relamping occurs. However, this arrangement also increases the complexity, size, and cost of the timing circuit. 
     BRIEF DESCRIPTION OF THE INVENTION 
     This disclosure is directed to an improved system and method for controlling a light system after relamping. Embodiments of the system and method offer one or more differences and/or advantages over prior systems and methods. For example, it has been discovered that a lighting system does not need an individual timing circuit for each and every lamp, as conventionally taught. Instead, and in contrast to prior systems and methods, embodiments of the invention combine a plurality of lamp insertion detector outputs, one for each lamp, into a single input of a common timing circuit, and arrange the timing circuit to output a signal of predetermined duration to a ballast driver circuit. By eliminating multiple timing circuits, one for each lamp, that prior systems require, embodiments of the invention are characterized by more compact circuitry that uses less space on a printed circuit board. Upon receipt of the timing circuit output, the ballast driver circuit operates to provide a high voltage for the predetermined duration of the timing circuit output. This high voltage is sufficient to start the new lamp. 
     One exemplary aspect of the present disclosure is directed to a lighting system. The lighting system includes a ballast having a ballast driver circuit and a timing circuit. The lighting system further includes a plurality of lamp sockets coupled to the ballast driver circuit and a plurality of lamp insertion detectors. Each lamp insertion detector is associated with at least one of the plurality of lamp sockets. Each of the lamp insertions detectors is configured to provide an output associated with lamp insertion into one of the plurality of lamp sockets. The outputs of the plurality of lamp insertion detectors are combined to form an input of the timing circuit. The timing circuit is configured to provide a control output to the ballast driver circuit based at least in part on the combined outputs received at the input of the timing circuit. 
     Another exemplary aspect of the present disclosure is directed to a method for controlling a lighting system. The method includes providing an output from each of a plurality of lamp insertion detectors. Each lamp insertion detector is associated with at least one of the plurality of lamp sockets. Each output is associated with lamp insertion into one of the plurality of lamp sockets. The method further includes combining the output from each of the plurality of lamp insertion detectors at an input received at a timing circuit and providing a control output from the timing circuit to a ballast driver circuit based at least in part on the combined outputs received at the input of the timing circuit. 
     These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Reference is now made briefly to the accompanying drawings in which: 
         FIG. 1  provides a block diagram of an exemplary lighting system according to an exemplary embodiment of the present disclosure; 
         FIG. 2  provides a circuit diagram of an exemplary lighting system according to an exemplary embodiment of the present disclosure; 
         FIG. 3  provides a timing diagram of an exemplary lighting system according to an exemplary embodiment of the present disclosure; 
         FIG. 4  provides a flow chart of an exemplary method of controlling a lighting system according to an exemplary embodiment of the present disclosure; 
         FIG. 5  provides a block diagram of an exemplary lighting system according to another exemplary embodiment of the present disclosure; and 
         FIG. 6  provides a block diagram of an exemplary lighting system according to another exemplary embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents. 
     Generally, the subject matter of the present disclosure relates to a system and method of controlling a lighting system having a ballast including a ballast driver circuit. Lamp insertion detectors are included with the lighting system to detect when lamp insertion occurs. The outputs of the lamp insertion detectors are combined into a single input of the timing circuit. After receiving an output indicative of lamp insertion from the lamp insertion detectors, the timing circuit produces a pulse of a predetermined duration to the ballast driver circuit. The ballast driver circuit then applies a high voltage to the corresponding lamp socket for a predetermined time interval to ignite the new lamp. 
       FIG. 1  illustrates a lighting system  100  that includes a power source  110 , a ballast  120 , and lamp sockets  161 ,  161 N. Lamp sockets  161 ,  161 N are configured to receive and power lamps  160 ,  160 N. Any number of lamp and/or lamp sockets can be included in lamp system  100 . Lamps  160 ,  160 N can be fluorescent lamps or any other type of lamp that utilizes a ballast for ignition and/or control. 
     Power source  110  supplies power to operate the lighting system  100 . The power source can be any type of power source such as a typical 2-phase 240V alternating current (AC) signal. Alternatively, power source  110  can be a 3-phase AC signal, a generator source, a battery, any type of DC power source or other suitable power source. 
     Ballast  120  can include a ballast driver circuit  130  and a timing circuit  140 . In addition, ballast  120  can also include a DC power circuit and rectifier (not shown) to condition power received from the power source  110 . The ballast  120  can also include a DC-DC converter if the power source  110  is a DC source or if an alternative voltage level is desired. 
     When manufactured, sold and/or shipped, embodiments of the lighting system  100  may include only the ballast  120 , preferably with one or more of its sub-components, ballast driver circuit  130  timing circuit  140 , and lamp insertion detectors  150 ,  150 N, or may include the ballast  120  and the lamp sockets  161 ,  161 N, with or without one or more lamps  160 ,  160 N installed therein. One or more of the sub-components, including, ballast driver circuit  130  timing circuit  140 , and lamp insertion detectors  150 ,  150 N, may be formed on a printed circuit board (PCB). This PCB may be manufactured, shipped and/or sold separately or together with the ballast  120  and/or the light sockets  161 ,  161 N. Alternatively, one or all of the sub-components may be separate devices. For example, the lamp insertion detectors  150 ,  150 N may be separate components but coupled to the ballast  120 . There may be any number of lamps  160 ,  160 N included in lamp system  100 . 
     Ballast driver circuit  130  can include any elements or devices for driving the lamps such as an inverter, switching elements, a voltage regulator, ballast capacitors and/or a ballast inductor. In addition, the ballast driver circuit  130  can include a warm-up circuit to warm the lamp electrodes prior to ignition to prevent disproportional depletion of the emission coating. Further, ballast driver circuit  130  can include a microprocessor that may include a memory and microprocessor, CPU or the like, such as a general or special purpose microprocessor operable to execute programming instructions or micro-control code associated with light system control. The memory may represent random access memory such as DRAM, or read only memory such as ROM or FLASH. In one embodiment, the processor can execute programming instructions stored in memory. If ballast driver circuit  130  includes a memory, the memory may be a separate component from the processor or may be included onboard within the processor. 
     The lighting system  100  can also include a plurality of lamp insertion detectors  150 ,  150 N. The lamp insertion detectors  150 ,  150 N can be part of or separate from the ballast  120 . Each lamp insertion detector  150 ,  150 N is associated with one of the lamp sockets  160 ,  160 N. For instance, a single lamp insertion detector  150 ,  150 N can be associated with a single lamp socket  160 ,  160 N. 
     The lamp insertion detectors  150 ,  150 N are configured to monitor lamp insertion into their corresponding lamp sockets  161 ,  161 N. For instance, when a new lamp is inserted into one of the plurality of lamp sockets  161 ,  161 N, the lamp insertion detector  150 ,  150 N can detect a change in state of the lamp socket  160 ,  160 N. An output signal is generated by the lamp insertion detector  150 ,  150 N indicative of the change of state and the signal is transmitted to the timing circuit  140  via one of the output terminals  152 ,  152 N. 
     According to aspects of the present disclosure, the outputs of the lamp insertion detectors  150 ,  150 N are combined to form an input of the timing circuit  140 . For instance, all of the outputs terminals  152 ,  152 N of lamp insertion detectors  150 ,  150 N can be coupled to an input  153  of a timing circuit  140 . The input can be a single input terminal of the timing circuit  140 . 
     The timing circuit  140  provides a control signal (or control output) that controls the ballast driver circuit  130  to apply an ignition voltage to start the new lamp. Specifically, the timing circuit  140  generates a triggering pulse that has a predetermined time interval or duration. The triggering pulse is provided to the ballast driver circuit  130 . The triggering pulse controls the ballast driver circuit  130  to apply an ignition voltage (i.e. higher voltage) to lamp sockets  161 ,  161 N for the predetermined time interval. After the predetermined time interval, a voltage applied to the lamp sockets  161 ,  161 N is reduced to a normal operating voltage which is different from and can be less than the ignition voltage. 
     In a particular implementation, timing capacitors C, C N  can be coupled between the lamp insertion detectors  150  and the input  153  of the timing circuit  140  to prevent false output pulses to the timing circuit  140  and to provide timing for the outputs received from the plurality of lamp insertion detector  150 ,  150 N to the timing circuit  140 . 
       FIG. 2  illustrates an exemplary configuration of lamp insertion detectors  150 ,  150 N within lighting system  100 . Each lamp insertion detector  150 ,  150 N includes a power source Vcc to power the detector, resistive elements R 1 , R 2 , a lamp electrode  155 ,  155 N, and a sensing capacitor C 2 . The lamp electrode  155 ,  155 N represents one end of the lamp coupled in a lamp socket  161 ,  161 N where the lamp socket  161 ,  161 N is coupled to the lamp insertion detector  150 ,  150 N. In addition, a secondary cathode heat transformer T 1  and capacitor C 1  are included to deliver an ignition voltage to the lamp socket  161 ,  161 N. Lamp V AC  is an input signal provided from the ballast driver circuit  130  to provide an AC signal to power a lamp in the lamp socket  161 ,  161 N. When diode D 1  is included in the lamp insertion detection circuits  150 ,  150 N, the AC signal supplied by Lamp V AC  is rectified into a DC signal. This prevents falsely triggering a pulse to the timing circuit  140  during normal operation of the lamp. 
     As will be discussed with reference to  FIG. 3  below, when no lamp is installed within the lamp socket  161 ,  161 N, C 1  charges to maximum capacity and an open circuit is created in the lamp insertion detector  150  preventing current from flowing through diode D 1  to resistor R 2  and sensing capacitor C 2 . After a lamp is inserted into the lighting system, current is conducted from Vcc through resistor R 1 , lamp electrode, and diode D 1  to resistor R 2  and sensing capacitor C 2 . As current passes through sensing capacitor C 2 , a voltage is induced on sensing capacitor C 2  and charge begins to be stored. 
       FIG. 3  is a timing diagram of an exemplary configuration of the lighting system shown at three different points I, II, and III in  FIG. 2 . The time periods illustrated in  FIG. 3  are exemplary timing intervals derived from times t 1 , t 2 , t 3 , t 4  and may not represent exact timing intervals. Referring to the first graph (I) of  FIG. 3 , when a lamp  160 ,  160 N is removed from the lighting system prior to t 1  (e.g. a lamp is not inserted into a respective lamp socket), a low voltage output, such as 0V, is provided by lamp insertion detector  150 , as shown by waveform  310 . In particular, when no lamp is installed within the lamp socket  161 ,  161 N, C 1  charges to maximum capacity and an open circuit is created in the lamp insertion detector  150  preventing current from flowing through diode D 1  to resistor R 2  and sensing capacitor C 2 . 
     Referring still to graph (I), a new lamp is inserted into a lamp socket  161 ,  161 N of the system at t 1  and a high signal is provided by the lamp insertion detectors  150 ,  150 N. In particular, after a lamp is inserted into the lighting system, a circuit is created and current is conducted from Vcc through resistor R 1 , lamp electrode, and diode D 1  to resistor R 2  and sensing capacitor C 2 . As current passes through sensing capacitor C 2 , a voltage is induced on sensing capacitor C 2  and charge begins to be stored. 
     The output signals  152 ,  152 N of the lamp insertion detectors  150 ,  150 N can be combined into a single output signal provided to the timing circuit  140  as shown in waveform  320  of graph (II). After timing capacitors C, C N  reach a threshold capacity, a signal can be sent from timing circuit  140  to ballast driver circuit  130  as shown in the third graph (III) by waveform  330 . This triggering pulse, shown as waveform  330 , has a predetermined time interval or pulse width. The triggering pulse can control the ballast driver circuit  130  to provide an ignition voltage to the lamp sockets  161 ,  161 N for a predetermined time period. 
       FIG. 4  illustrates a flow chart of an exemplary method  400  according to an exemplary embodiment of the present disclosure. The method  400  will be discussed with reference to the exemplary lighting system discussed with reference to  FIGS. 1-3 . However, the method  400  can be implemented with any suitable lighting control system. In addition, although  FIG. 4  depicts steps performed in a particular order for purposes of illustration and discussion, the methods discussed herein are not limited to any particular order or arrangement. One skilled in the art, using the disclosures provided herein, will appreciate that various steps of the methods can be omitted, rearranged, combined and/or adapted in various ways. 
     At ( 410 ), the timing circuit system monitors insertion of lamps in the lamp sockets  161 ,  161 N with lamp insertion detectors  150 ,  150 N. The method determines if a lamp has been inserted based on the outputs of the lamp insertion detectors at ( 420 ). If so, the outputs of the lamp insertion detectors  150 ,  150 N are combined and provided to the timing circuit  140  at ( 430 ). For instance, the outputs of the lamp insertion detectors  150 ,  150 N can be combined and applied to a common input terminal of the timing circuit  140 . 
     At ( 440 ), a pulse is sent from the timing circuit  140  to the ballast driver circuit  130  based on the combined outputs of the lamp insertion detectors  150 ,  150 N. As discussed above, the pulse can have a predetermined time interval. At ( 450 ), the ballast driver circuit  130  controls the voltage applied to the lamp sockets  161 ,  161 N based on the triggering pulse generated by the timing circuit  140 . For instance, the ballast driver circuit  130  can provide an ignition voltage to the lamp sockets  161 ,  161 N for the duration of the time interval and can provide a normal operating voltage to the lamp sockets  161 ,  161 N upon the expiration of the predetermined time interval. 
       FIG. 5  is a block diagram of a lighting system according to another embodiment of the present disclosure. Lighting system  500  can include a power source  510 , a ballast  520 , and a plurality of lamps  560 ,  560 N corresponding to lamp sockets  561 ,  561 N. The ballast can include a ballast driver circuit  530  and a timing circuit  540 . The lighting system  500  can further include lamp insertion detectors  550 ,  550 N configured to monitor lamp insertion into the lamp sockets  561 ,  561 N. The various components of lighting system  500  can be similar to the components of the lighting system  100  discussed and described with reference to  FIG. 1 . 
     Referring to  FIG. 5 , the outputs  552 ,  552 N of the lamp insertion detectors  550 ,  550 N can be combined to form an input of timing circuit  540 . Timing circuit  540  is coupled to an input  542  of the ballast driver circuit  530  and provides a control output from the timing circuit  540  to the ballast driver circuit  530  based on the combined outputs  553  received from the lamp insertion detectors  550 ,  550 N. 
     Timing capacitors C, C N  can be provided between the lamp insertion detectors and the common input  553  of the timing circuit  540 . In addition, resistors R 51 , R 52 , R 53 , R 54  and R 55  can be coupled between lamp signal detectors  550  and timing capacitors C, C N , and/or coupled between timing capacitors C, C N  and timing circuit  540  to prevent false output triggering pulses to the timing circuit  540  and to adjust signal timing for the output triggering pulse from the plurality of lamp insertion detector  550 ,  550 N to the timing circuit  540 . The resistors do not change the fundamental operation of the circuit, but rather affects the timing of the signals. For example, how fast or slow the signals are communicated within the system. In other words, the timing can be modified based on the use of resistors. 
       FIG. 6  is a block diagram of a lighting system according to another embodiment of the present disclosure. Similar to the lighting system  100  of  FIG. 1 , the lighting system  600  of  FIG. 6  includes a power source  610 , a ballast  620 , and a plurality of lamps  660 ,  660 N corresponding to lamp sockets  661 ,  661 N. The plurality of lamps sockets  661 ,  661 N can be associated with lamp insertion detectors  650 ,  650 N. The outputs  652 ,  652 N of the lamp insertion detectors  650 ,  650 N can be combined to form an input of a timing circuit  640 . Timing circuit  640  is coupled to an input  642  of a ballast driver circuit  630  and provides a control output to the ballast driver circuit  630  based on the combined outputs received from the lamp insertion detectors  650 ,  650 N. 
     As illustrated, lighting system  600  further includes a filtering element including a filtering capacitor C F  and filtering resistor R F  coupled to at least one output  652 N of lamp insertion detectors  650 ,  650 N. While the filtering capacitor C F  and filtering resistor R F  are illustrated as only being associated with output  652 N, the filtering capacitor C F  and filtering resistor R F  can be associated with any or all outputs of the lamp insertion detectors  650 ,  650 N. The filtering element can be included as part of the timing circuit or it can be a separate element. While the filtering element, shown in  FIG. 6 , is coupled to ground, it may alternatively be coupled to a DC voltage. When coupled with a DC voltage, a voltage level shift would occur in the trigger pulse. 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.