Patent Publication Number: US-2004051475-A1

Title: Instant start of series lamp combination

Description:
TECHNICAL FIELD  
       [0001] The present invention generally relates to fluorescent lamps. The present invention specifically relates to an operation of a sequential ignition of two fluorescent lamps.  
       BACKGROUND AND SUMMARY OF THE INVENTION  
       [0002]FIG. 1 illustrates a known illumination circuit  10  between a SUPPLY and a RETURN. The illumination circuit  10  has a capacitor C B  (representative of a ballast) coupled to a node N 1  and a node N 2 , with the SUPPLY being coupled to the node N 1 . A parallel coupling of a lamp  20   a  and a capacitor C S  are coupled to the node N 2  and a node N 3 . And, a lamp  20   b  is coupled to the node N 3  and the RETURN.  
       [0003] In operation, lamps  20   a  and  20   b  are sequentially ignited. Specifically, upon a supply voltage V SS  being applied to the node N 1 , the capacitor C S1  acts as a short to thereby establish a lamp current path I P1 , for igniting the lamp  20   b  whereby a magnitude of a lamp voltage V L1  across the lamp  20   a  is zero (0) volts and a magnitude of a lamp voltage V L2  across the lamp  20   b  approximates a ballast output voltage V B  applied to the node N 2 . After an ignition of the lamp  20   b,  the lamp voltage V L1  across the lamp  20   a  increases to a difference between the supply voltage V SS  and the lamp voltage V L2  (i.e., V SS −V L2 ) to thereby sequentially ignite the lamp  20   a.  After both lamps  20   a  and  20   b  have been ignited, current flowing through the lamps  20   a  and  20   b  along a current path I P2  is controlled by the capacitor C B .  
       [0004] A drawback of the FIG. 1 illumination circuit  10  is a capacitance of the capacitor C S1 , must equate or be greater than a capacitance of the capacitor C B  in order to guarantee ignition of the lamp  20   b.  However, after ignition of the lamps  20   a  and  20   b,  current flowing through the capacitor C S1  is parasitic and therefore does not contribute to the light output of the lamps  20   a  and  20   b  during normal operation. The present invention addresses the aforementioned drawback of FIG. 1.  
       [0005] Various aspects of the present invention are novel, non-obvious, and provide various advantages. While the actual nature of the present invention covered herein can only be determined with reference to the claims appended hereto, certain features, which are characteristic of the embodiments disclosed herein, are described briefly as follows.  
       [0006] The present invention is an illumination circuit comprising a ballast, a capacitor, a first lamp and a second lamp. In one form, the ballast and the capacitor are coupled to a first node, the capacitor and the pair of lamps are coupled to a second node, and the ballast is further coupled to the first lamp. In a second form, a series coupling of the ballast and the first lamp is coupled in parallel to the capacitor, and the second lamp is coupled to the parallel coupling of the series coupling and the capacitor. In a third form, an operative current path for igniting the second lamp consists of the capacitor and the second lamp, and an operative current path for igniting the first lamp consists of the ballast and the pair of lamps.  
       [0007] The foregoing forms as well as other forms, features and advantages of the present invention will become further apparent from the following detailed description of the presently preferred embodiments, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the present invention rather than limiting, the scope of the present invention being defined by the appended claims and equivalents thereof.  
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0008]FIG. 1 illustrates a diagram of an illumination circuit known in the art;  
     [0009]FIG. 2 illustrates a diagram of an illumination circuit in accordance with the present invention;  
     [0010]FIG. 3 illustrates an exemplary signal waveform indicative of an ignition time of lamps by the FIG. 1 illumination circuit; and  
     [0011]FIG. 4 illustrates an exemplary signal waveform indicative of an ignition time of lamps by the FIG. 3 illumination circuit. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0012]FIG. 2 illustrates an illumination circuit  11  in accordance with the present invention. In lieu of capacitor C S1  (FIG. 1), the illumination circuit  11  has a capacitor C S2  coupled to the node N 1  and the node N 3 . The capacitor C B  (again, representative of a ballast) is coupled to the lamp  20   a,  which is coupled to the node N 3 . And, the lamp  20   b  is coupled to the node N 3  and the RETURN.  
     [0013] In operation, lamps  20   a  and  20   b  are sequentially ignited. Specifically, upon the supply voltage V SS  being applied to the node N 1 , the capacitor C S2  acts as a short to thereby establish a lamp current path I P3  for igniting the lamp  20   b  whereby a magnitude of a lamp voltage V L3  across the lamp  20   a  is zero (0) volts and a magnitude of a lamp voltage V L4  across the lamp  20   b  approximates the supply voltage V SS . After an ignition of the lamp  20   b,  the voltage V L3  across the lamp  20   a  increases to a difference between the supply voltage V SS  and the lamp voltage V L4  (i.e., V SS −V L4 ) to thereby sequentially ignite the lamp  20   a.  After both lamps  20   a  and  20   b  have been ignited, current flowing through the lamps  20   a  and  20   b  along a current path I P4  is controlled by the capacitor C B  and a current through flowing the capacitor C S2  along the current path I P3  is negligible.  
     [0014]FIG. 3 illustrates an exemplary signal waveform of an ignition time of approximately 500 ms for the lamps  20   a  and  20   b  as employed in the illumination circuit  10  (FIG. 1). FIG. 4 illustrates an exemplary signal waveform of an ignition time of approximately 180 ms for lamps  20   a  and  20   b  as employed in the illumination circuit  11  (FIG. 2). From FIGS. 3 and 4, those having ordinary skill in the art will appreciate that the illumination circuit  11  is an unique combination of an instant start series combination of lamps  20   a  and  20   b  which results in longer lamp life by a decrease in the ignition time of the lamps  20   a  and  20   b.    
     [0015] The illustrated couplings of the various components of illumination circuit  11  can be achieved in many ways (e.g., optically, magnetically, acoustically, and preferably, electrically via conductors). Also, alternative embodiments of the illumination circuit  11  can include additional components to enhance the functionality of the illumination circuit  11  without any altering the illustrated couplings in FIG. 2.  
     [0016] While the embodiments of the present invention disclosed herein are presently considered to be preferred, various changes and modifications can be made without departing from the spirit and scope of the present invention. The scope of the present invention is indicated in the appended claims, and all changes that come within the meaning and range of equivalents are intended to be embraced therein.  
     IN THE SPECIFICATION  
     [0017] The present invention generally relates to fluorescent lamps. The present invention specifically relates to an operation of athe sequential ignition of two series connected fluorescent lamps. Page  4 , in the paragraph beginning on line  12 , please amend as follows:  
     [0018]FIG. 4 illustrates an exemplary signal waveform indicative of an ignition time of lamps by the FIG. 32 illumination circuit. Page  5 , in the paragraph beginning on line  15 , please amend as follows:  
     [0019] The illustrated couplings of the various components of illumination circuit  11  can be achieved in many ways (e.g., optically, magnetically, acoustically, and preferably, electrically via conductors). Also, alternative embodiments of the illumination circuit  11  can include additional components to enhance the functionality of the illumination circuit  11  without any altering alteration of the illustrated couplings in FIG. 2.