Patent Publication Number: US-8531107-B2

Title: Control system for fluorescent light fixture

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 12/502,570 (now U.S. Pat. No. 8,120,286), filed Jul. 14, 2009. U.S. patent application Ser. No. 12/502,570 is a continuation of U.S. patent application Ser. No. 11/112,808 (now U.S. Pat. No. 7,560,866), filed Apr. 22, 2005, which claims the benefit of U.S. Provisional Application No. 60/672,250, filed Apr. 18, 2005. The disclosures of the above applications are incorporated herein by reference. 
    
    
     FIELD 
     The present invention relates to fluorescent light fixtures, and more particularly to control systems for fluorescent light fixtures. 
     BACKGROUND 
     Referring now to  FIG. 1 , a fluorescent lamp  10  includes a sealed glass tube  12  that contains a first material such as mercury and a first inert gas such as argon, which are both generally identified at  14 . The tube  12  is pressurized. Phosphor powder  16  may be coated along an inner surface of the tube  12 . The tube  12  includes electrodes  18 A and  18 B (collectively electrodes  18 ) that are located at opposite ends of the tube  12 . Power is supplied to the electrodes  18  by a control system that may include an AC source  22 , a switch  24 , a ballast module  26  and a capacitor  28 . 
     When the switch  24  is closed, the control system supplies power to the electrodes  18 . Electrons migrate through the gas  14  from one end of the tube  12  to the opposite end. Energy from the flowing electrons changes some of the mercury from a liquid to a gas. As electrons and charged atoms move through the tube  12 , some will collide with the gaseous mercury atoms. The collisions excite the atoms and cause electrons to move to a higher state. As the electrons return to a lower energy level they release photons or light. Electrons in mercury atoms release light photons in the ultraviolet wavelength range. The phosphor coating  16  absorbs the ultraviolet photons, which causes electrons in the phosphor coating  16  to jump to a higher level. When the electrons return to a lower energy level, they release photons having a wavelength corresponding to white light. 
     To send current through the tube  12 , the fluorescent light  10  needs free electrons and ions and a difference in charge between the electrodes  18 . Generally, there are few ions and free electrons in the gas  14  because atoms typically maintain a neutral charge. When the fluorescent light  10  is turned on, it needs to introduce new free electrons and ions. 
     The ballast module  26  outputs current through both electrodes  18  during starting. The current flow creates a charge difference between the two electrodes  18 . When the fluorescent light  10  is turned on, both electrode filaments heat up very quickly. Electrons are emitted, which ionizes the gas  14  in the tube  12 . Once the gas is ionized, the voltage difference between the electrodes  18  establishes an electrical arc. The flowing charged particles excite the mercury atoms, which triggers the illumination process. As more electrons and ions flow through a particular area, they bump into more atoms, which frees up electrons and creates more charged particles. Resistance decreases and current increases. The ballast module  26  regulates power both during and after startup. 
     Referring now to  FIG. 2 , some ballast modules  50  include a control module  54 , one or more electrolytic capacitors  56  and other components  58 . The electrolytic capacitors  56  may be used to filter or smooth voltage. Electrolytic capacitors  56  and/or other system components may be sensitive to high operating temperatures. If the operating temperature exceeds a threshold for a sufficient period, the electrolytic capacitor  56  and/or other system components may be damaged and the fluorescent light  10  may become inoperable. 
     SUMMARY 
     A circuit includes a component connected (i) to a rectifier, and (ii) between electrodes of a lamp. The electrodes include a first electrode and a second electrode. A control module is in communication with the rectifier and is configured to receive a temperature signal from a temperature sensor. The temperature signal is indicative of a temperature of the component. The control module is also configured to decrease current to the electrodes for a predetermined period when the temperature of the component is greater than a first predetermined temperature. The control module is further configured to increase the current to the electrodes when the predetermined period expires and independent of the temperature of the component. 
     In other features, a method is provided and includes operating a control module based on an output of a rectifier. A temperature signal is received from a temperature sensor by the control module. The temperature signal is indicative of a temperature of a component. The component is connected (i) to the rectifier, and (ii) between electrodes of a lamp. The electrodes include a first electrode and a second electrode. Current to the electrodes is decreased for a predetermined period via the control module when the temperature of the component is greater than a first predetermined temperature. The current to the electrodes is increased via the control module when the predetermined period expires independent of the temperature of the component. 
     In other features, a ballast module for a fluorescent light is provided and includes an electrolytic capacitance element. A temperature sensor senses a temperature of the electrolytic capacitance element. A control module communicates the temperature sensor and adjusts power output to the fluorescent light when the sensed temperature exceeds a predetermined threshold. 
     In other features, the control module reduces the power output to the fluorescent light. The control module reduces the power output for a predetermined period. The control module increases power output to the fluorescent light after the predetermined period. The control module turns off the power output to the fluorescent light. The control module turns off the power output for a predetermined period. The control module increases power output to the fluorescent light after the predetermined period. The control module modulates the power output based on the sensed temperature. 
     In other features, a system is provided and includes the ballast module and a switch that selectively provides power to the control module. The switch is a three-way switch. A rectifier module has an input that selectively communicates with a voltage source. The electrolytic capacitance element and the control module communicate with an output of the rectifier module. 
     In other features, the ballast module further includes a first power transistor having a first terminal that communicates with a first output terminal of the rectifier and a control terminal that communicates with the control module. A second power transistor has a first terminal that communicates with a second terminal of the first power transistor, and a control terminal that communicates with the control module. A second capacitance element communicates with the first and second terminals of the first power transistor. An inductance element has one end that communicates with the second terminal of the first power transistor and an opposite end that communicates with an electrode of the fluorescent light. 
     In other features, a system is provided and includes the ballast module and the fluorescent light having first and second pairs of electrodes. A third capacitance element communicates with one of the first pair of electrodes and one of the second pair of electrodes. In other features, a system is provided and includes the ballast module and the fluorescent light having first and second pairs of electrodes. A fourth capacitance element communicates with one of the first pair of electrodes and the second capacitance element. 
     In other features, a ballast module for a fluorescent light is provided and includes an electrolytic capacitance means for providing capacitance. Temperature sensing means senses a temperature of the electrolytic capacitance means. Control means communicates with the temperature sensing means for adjusting power output to the fluorescent light when the sensed temperature exceeds a predetermined threshold. 
     In other features, the control means reduces the power output to the fluorescent light. The control means reduces the power output for a predetermined period. The control means increases power output to the fluorescent light after the predetermined period. The control means turns off the power output to the fluorescent light. The control means turns off the power output for a predetermined period. The control means increases power output to the fluorescent light after the predetermined period. The control means modulates the power output based on the sensed temperature. 
     In other features, a system is provided and includes the ballast module and switching means for selectively providing power to the control means. The switching means is a three-way switching means. Rectifier means for rectifying has an input that selectively communicates with a voltage source. The electrolytic capacitance means and the control means communicate with an output of the rectifier means. First power switching means for switching has a first terminal that communicates with a first output terminal of the rectifier and a control terminal that communicates with the control means. Second power switching means for switching has a first terminal that communicates with a second terminal of the first power switching means, and a control terminal that communicates with the control means. Second capacitance means for providing capacitance communicates with the first and second terminals of the first power switching means. Inductance means for providing inductance has one end that communicates with the second terminal of the first power switching means and an opposite end that communicates with an electrode of the fluorescent light. 
     In other features, a system is provided and includes the ballast module and the fluorescent light having first and second pairs of electrodes. Third capacitance means for providing capacitance communicates with one of the first pair of electrodes and one of the second pair of electrodes. In other features, a system is provided and includes the ballast module and the fluorescent light having first and second pairs of electrodes. Fourth capacitance means for providing capacitance and that communicates with one of the first pair of electrodes and the second capacitance means. 
     In other features, a method for operating a ballast module for a fluorescent light is provided and includes providing an electrolytic capacitance element in the ballast module; sensing a temperature of the electrolytic capacitance element; and adjusting power output to the fluorescent light when the sensed temperature exceeds a predetermined threshold. 
     In other features, the method includes reducing the power output to the fluorescent light. The method includes reducing the power output for a predetermined period. The method includes increasing power output to the fluorescent light after the predetermined period. The method includes turning off the power output to the fluorescent light. The method includes turning off the power output for a predetermined period. The method includes increasing power output to the fluorescent light after the predetermined period. The method includes modulating the power output based on the sensed temperature. The method includes selectively providing power to the control module. 
     In other features, a control system for a fluorescent light is provided and includes a first electrical component. A temperature sensor senses a temperature of the first electrical component. A control module communicates with the temperature sensor and adjusts power output to the fluorescent light when the sensed temperature exceeds a predetermined threshold. 
     In other features, the control module reduces the power output to the fluorescent light. The control module reduces the power output for a predetermined period. The control module increases power output to the fluorescent light after the predetermined period. The control module turns off the power output to the fluorescent light. The control module turns off the power output for a predetermined period. The control module increases power output to the fluorescent light after the predetermined period. The control module modulates the power output based on the sensed temperature. 
     The control system further includes a switch that selectively provides power to the control module. The switch is a three-way switch. A rectifier module has an input that selectively communicates with a voltage source. The electrolytic capacitance element and the control module communicate with an output of the rectifier module. 
     In other features, the control system further includes a first power transistor having a first terminal that communicates with a first output terminal of the rectifier and a control terminal that communicates with the control module. A second power transistor has a first terminal that communicates with a second terminal of the first power transistor, and a control terminal that communicates with the control module. A second capacitance element communicates with the first and second terminals of the first power transistor. An inductance element has one end that communicates with the second terminal of the first power transistor and an opposite end that communicates with an electrode of the fluorescent light. 
     The control system further includes the fluorescent light having first and second pairs of electrodes. A third capacitance element communicates with one of the first pair of electrodes and one of the second pair of electrodes. The control system further includes the fluorescent light having first and second pairs of electrodes. A fourth capacitance element communicates with one of the first pair of electrodes and the second capacitance element. 
     In other features, a control system for a fluorescent light is provided and includes first means for providing a first electrical function. Temperature sensing means senses a temperature of the first means. Control means communicates with the temperature sensing means for adjusting power output to the fluorescent light when the sensed temperature exceeds a predetermined threshold. 
     In other features, the control means reduces the power output to the fluorescent light. The control means reduces the power output for a predetermined period. The control means increases power output to the fluorescent light after the predetermined period. The control means turns off the power output to the fluorescent light. The control means turns off the power output for a predetermined period. The control means increases power output to the fluorescent light after the predetermined period. The control means modulates the power output based on the sensed temperature. 
     The control system further includes switching means for selectively providing power to the control means. The switching means is a three-way switching means. Rectifier means for rectifying has an input that selectively communicates with a voltage source. The electrolytic capacitance means and the control means communicate with an output of the rectifier means. First power switching means for switching has a first terminal that communicates with a first output terminal of the rectifier and a control terminal that communicates with the control means. Second power switching means for switching has a first terminal that communicates with a second terminal of the first power switching means, and a control terminal that communicates with the control means. Second capacitance means for providing capacitance communicates with the first and second terminals of the first power switching means. Inductance means for providing inductance has one end that communicates with the second terminal of the first power switching means and an opposite end that communicates with an electrode of the fluorescent light. 
     The control system further includes the fluorescent light having first and second pairs of electrodes. Third capacitance means for providing capacitance communicates with one of the first pair of electrodes and one of the second pair of electrodes. The control system further includes the fluorescent light having first and second pairs of electrodes. Fourth capacitance means for providing capacitance and that communicates with one of the first pair of electrodes and the second capacitance means. 
     In other features, a method for operating a control system for a fluorescent light is provided and includes providing a first electrical component; sensing a temperature of the first electrical component; and adjusting power output to the fluorescent light when the sensed temperature exceeds a predetermined threshold. 
     In other features, the method includes reducing the power output to the fluorescent light. The method includes reducing the power output for a predetermined period. The method includes increasing power output to the fluorescent light after the predetermined period. The method includes turning off the power output to the fluorescent light. The method includes turning off the power output for a predetermined period. The method includes increasing power output to the fluorescent light after the predetermined period. The method includes modulating the power output based on the sensed temperature. The method includes selectively providing power to the control module. 
     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a functional block diagram of an exemplary control system for a fluorescent light according to the prior art; 
         FIG. 2  is a more detailed functional block diagram of the control system for the fluorescent light of  FIG. 1 ; 
         FIG. 3  is a functional block diagram of an improved control system for a fluorescent light according to the present invention; 
         FIG. 4  is an electrical schematic and functional block diagram of an exemplary implementation of the control system of  FIG. 3 ; 
         FIG. 5  is a first exemplary flowchart illustrating steps for operating the control system of  FIG. 3 ; 
         FIG. 6  is a second exemplary flowchart illustrating steps for operating the control system of  FIG. 3 ; and 
         FIG. 7  is a third exemplary flowchart illustrating steps for operating the control system of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. As used herein, the term module refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. 
     Referring now to  FIG. 3 , a functional block diagram of a control system  98  for the fluorescent light  10  is shown. A ballast module  100  includes a control module  104 , one or more electrolytic capacitors  108 , and one or more other components generally identified at  110 . The ballast module  100  includes one or more temperature sensing modules  112  and  114  that sense operating temperatures of components of the ballast module  100  and/or of the control system of the florescent light  10 . In some implementations, the temperature sensor  112  senses an operating temperature of the electrolytic capacitor  108  and the temperature sensor  114  senses an operating temperature of one or more other components  110  of the ballast module  100  and/or the control system. 
     The control module  104  adjusts operation of the fluorescent light  10  based on one or more of the sensed operating temperatures. For example, the control module  104  shuts off the florescent light  10  when the operating temperature of the electrolytic capacitor  56  exceeds a predetermined temperature threshold. Alternately, the control module  104  turns off the florescent light  10  for a predetermined period, until reset, indefinitely and/or using other criteria. In other implementations, the control module  104  lowers an output voltage and/or current of the ballast module  100  for a predetermined period, indefinitely, until reset and/or using other criteria. 
     Referring now to  FIG. 4 , an exemplary implementation of the ballast module  100  is shown to include a full or half-wave rectifier  120 , the electrolytic capacitor  106  and the control module  104 . A first terminal of a power transistor  126  is connected to a first output of the rectifier  120 . A second terminal is connected to the control module  104  and to a first terminal of a power transistor  128 . The control module  104  switches the power transistors on and off to vary current and/or voltage to the florescent light  10  during startup and/or operation. 
     A capacitor C 1  may be connected to the first output of the rectifier  120 , the second terminal of the power transistor  126 , the first terminal of the power transistor  128  and one end of an inductor L. An opposite end of the inductor L may communicate with one end of the electrode  18 A. An opposite end of the electrode  18 A is coupled by a capacitor C 3  to one end of the electrode  18 B. The first output of the rectifier  120  is coupled by a capacitor C 2  to an opposite end of the electrode  18 B. 
     Referring now to  FIG. 5 , a flowchart illustrating steps for operating the control system of  FIG. 3  is shown. Control begins with step  200 . In step  204 , control determines whether the switch  24  is on. If false, control returns to step  204 . If step  204  is true, control determines whether the florescent light  10  is already on. If true, control continues with step  208  and determines whether a sensed temperature is greater than a threshold temperature. The sensed temperature may relate to the electrolytic capacitor  56  and/or other components of the ballast module  100  and/or other components of the control system. If step  206  is false, control starts the light in step  214  continues with step  208 . If step  208  is false and the threshold temperature has not been exceeded, control determines whether the switch  24  is off in step  210 . If the switch  24  is not off, control returns to step  204 . 
     When step  208  is true, control turns off the switch  24  and/or florescent light  10  in step  216 . In some implementations, the switch  24  may be controlled by the control module  104 . Alternately, the control module  104  may turn off the florescent light  10  independent from a position of the switch  24 . Alternately, the control module  104  may operate as a three way switch in conjunction with a three-way switch  24 . When step  210  is true and the switch  24  is off, control turns off the florescent light  10  in step  218 . 
     Referring now to  FIG. 6 , a flowchart illustrating alternate steps for operating the control system of  FIG. 3  is shown. When step  208  is false, control returns to step  204 . When step  208  is true, control turns off the florescent light  10  in step  242 . In step  246 , control starts a timer. In step  250 , control determines whether the timer is up. If step  250  is true, control returns to step  204 . Otherwise, control returns to step  250 . 
     Referring now to  FIG. 7 , a flowchart illustrating alternative steps for operating the control system of  FIG. 3  is shown. When step  208  is true, control reduces power that is output to the florescent light  10  in step  282 . Reducing power output to the florescent light  10  may include reducing voltage and/or current output by the ballast module  100 . The florescent light  10  may be operated in this mode until reset using the switch  24 . Alternately in step  286 , control starts a timer. In step  290 , control determines whether the timer is up. If step  290  is true, control returns to step  204 . Otherwise, control returns to step  290 . 
     Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present invention can be implemented in a variety of forms. For example, the temperature of a component can be sensed and the power output can be modulated accordingly. Hysteresis, averaging and/or other techniques can be used to reduce flicker and/or other noticeable changes in light intensity that may occur. Therefore, while this invention has been described in connection with particular examples thereof, the true scope of the invention should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification and the following claims.