Abstract:
A low pollution, low energy consumption, high field effect neon lamp with scanning point selectable, the neon lamp includes a glass tube having at least one section of the outside wall thereof coated with a transparent conductive layer, a pulse width modulation and scanning control circuit connected to the transparent conductive layer, the pulse width modulation and scanning control circuit being controlled to give a high frequency high voltage pulse width variable pulse signal to the transparent conductive coating layer, causing a linearity-variable static electric field to be produced in the glass tube, so that an inert gas in the glass tube is ionized to strike a fluorescent material on the inside wall of the glass tube, causing it to emit light.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to neon lamps, and more particularly to a high field effect neon lamp which consumes less energy, produces low noise, and can be controlled to start scanning from any desired point. The neon lamp uses a pulse width modulated weak signal to control the scanning function. The design is capable of scanning a neon lamp tube of big diameter. 
     2. Description of the Prior Art 
     A regular neon lamp is equipped with positive and negative electrodes, and used with a ferromagnetic transformer of about 450 W or electronic transformer of about 100 ˜ 160 W. This structure of neon lamp consumes much energy. During the operation of the neon lamp, the high voltage transformer produces high noise. When a high voltage is provided to the high voltage electrodes, electric discharge takes place through an inert gas in the glass tube of the neon lamp, thereby causing a fluorescent material to be stricken. Because this structure of neon lamp works with a high voltage, it is not safe for use indoors. Furthermore, because of the installation limitation of the high voltage electrodes, the scanning of the neon lamp must be started from one end (for cost&#39;s sake, it is not practical to install the high voltage electrodes at the center area of the glass tube. 
     SUMMARY OF THE INVENTION 
     The present invention relates to neon lamps, and more particularly to a high field effect neon lamp which consumes less energy, produces low noise, and can be controlled to start scanning from any desired point. The neon lamp uses a pulse width modulated weak signal to control the scanning function. The design is capable of scanning a neon lamp tube of big diameter. 
     The present invention has been accomplished to provide a high field effect neon lamp which eliminates the aforesaid problems. It is one object of the present invention to provide a high field effect neon lamp which consumes less electric energy, and produces low noise. It is another object of the present invention to provide a high field effect neon lamp which can be made to start scanning from any desired point at the glass tube. It is still another object of the present invention to provide a high field effect neon lamp which is safe in use. According to the present invention, a pulse width modulation and scanning control circuit is provided and controlled to give a high frequency high voltage pulse width variable pulse signal to a transparent conductive coating layer, which is coated on desired area(s) at the outside wall of the glass tube of the neon lamp, causing a linearity-variable static electric field to be produced in the glass tube, so that an inert gas in the glass tube is ionized to strike a fluorescent material on the inside wall of the glass tube, causing it to emit light. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross sectional view of a neon lamp tube showing a transparent conductive layer covered on the outside wall of the glass tube according to the present invention; 
     FIG. 1A shows an application example of the present invention where the neon lamp is mounted on a car number plate holder frame and protected by a shade; 
     FIG. 1B shows another application example of the present invention where the neon lamp is made in the form of a Christmas tree and covered within a shade; 
     FIG. 2 is a circuit block diagram of a neon lamp control circuit according to the present invention; 
     FIG. 3 is a circuit diagram of the neon lamp control circuit shown in FIG. 2; 
     FIG. 4 is a circuit block diagram of a pulse width modulation and scanning control circuit according to the present invention; and 
     FIG. 5 is a circuit diagram of the pulse width modulation and scanning control circuit shown in FIG.  4 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIGS. 1,  1 A and  1 B, the outside wall of the glass tube  1  for a neon lamp in accordance with the present invention is coated with a layer of transparent conductive coating (for example, stannic peroxide)  3 . The glass tube  1  is preferably molded from rigid tungsten glass for the advantages of high machinery strength, high melting point, high plasticity, and high durability. After the glass tube  1  has been molded subject to the desired pattern, it is put in an oven and heated to a predetermined temperature, and then a prepared stannic chloride solution is blown into the oven, enabling a uniform spray of stannic chloride solution to be adhered to the outside wall of the glass tube  1 , and therefore a transparent conductive layer  3  is permanently covered on the outside wall of the glass tube  1  after an oxidation reduction reaction. The effective covering area of the transparent conductive layer  3  on the glass tube  1  is determined subject to the desired function. For example, when an area of about 10-20 mm long at the geometric center of the glass tube  1  is shielded from coating and maintained in blank and electrical wires are adhered to opposite ends of the transparent conductive layer  3  by a conductive glue, thus a neon lamp tube is obtained in which scanning is achieved from the center area of the lamp tube toward its both ends (the electric circuit will be described further). The neon lamp which is mounted on a car number plate holder frame is an example of this design. The initial scanning point can be at any desired point, or multiple initial scanning points can be set as desired. When the glass tube  1  is processed into a vacuum state, a certain amount of an inert gas and a small amount of mercury are filled in the glass tube  1 , and then a scan circuit is connected to the glass tube  1 , and a uniform scanning effect from the geometric center of the pattern (of the glass tube) toward opposite ends is thus achieved. If the transparent conductive layer  3  on the glass tube  1  is separated into several separated sections, a low radiation voltage normal lighting lamp is thus obtained. Changing the effective area of the transparent conductive layer  3  simultaneously changes the impedance of the lamp tube, thereby causing the light emitting point of the circuit to be relatively changed. FIGS. 1A and 1B show two neon lamps constructed according to the present invention. The neon lamp shown in FIG. 1A is mounted on a car number plate holder frame around a car number plate. The neon lamp shown in FIG. 1B is made to show the pattern of a Christmas tree. Furthermore, a plastic shade or transparent silicon rubber shade  2  is provided and covered around the glass tube to protect the transparent conductive layer of the neon lamp. 
     A neon lamp control circuit in accordance with the present invention, as shown in FIGS. 2 and 3 (FIG. 2 is a circuit block diagram of the neon lamp control circuit; FIG. 3 is a detailed circuit diagram of the neon lamp control circuit) is generally comprised of a power input circuit  1 , a EMI (electromagnetic interference) eliminator circuit  2 , a rectifier circuit  3 , a power factor compensation circuit  4 , a function controller  5 , an oscillator  6 , an exiting circuit  7 , a protective circuit  8 , a high frequency switch  9 , and an output circuit  10 . The power input circuit  1  is comprised of fuse means and pressure sensitive resistor means (TNR), and operated to inhibit surge voltage and surge current. The fuse means of the input protection circuit  1  is broken to cut off power supply when the circuit is abnormal. The EMI eliminator circuit  2  is comprised of L 1 ;C 1 ;C 2 ;C 3 ;C 4 , and operated to eliminate noises. The rectifier circuit  3  is a bridge rectifier comprised D 1   ˜ D 4 , and operated to rectify AC power supply into DC power supply. The power factor compensation circuit  4  is a non-source power factor compensation circuit comprised of C 5 ;C 6 ;D 6 ;D 7 . The power factor of the power factor compensation circuit  4  is over 0.9. The function control circuit  5  is comprised of IC 1 ;G 01 ;R 14 ;D 8  and an external control panel, and used for controlling the working status of the oscillator  6  by means of a photoelectric coupling method. The photoelectric coupling method greatly improves the reliability of the control of the function control circuit  5 . In comparison with the high voltage function control circuit for prior art neon lamps, the function control circuit  5  greatly reduces the manufacturing cost of the neon lamp control circuit, improves its reliability, prohibits the occurrence of high surge current, eliminates circuit stress, and achieves a high insulative effect. The oscillator  6  is comprised of IC 1 ;R 2 ;C 8 , and operated to produce a high frequency pulse signal. The exciting circuit  7  is comprised of IC 1 ;R 3 ;C 9 ;B 1 ;R 4 ;R 5 ;R 7 ;R 8 , and controlled to provide a two-way reverse phase signal. The high frequency switch  9  is an excited semi-bridge circuit comprised of G 1 ;G 2 ;C 10 ;C 11 ;R 9 ;R 10 ;R 6 ;B 2 . This high frequency switch design is stable, and can be conveniently controlled. Because metal-oxide-semiconductor field effect transistors are used, the switching efficiency of the high frequency switch  9  is greatly improved. The output circuit  10  is comprised of B 2 . The protective circuit  8  is comprised of R 10 ;R 11 ;R 12 ;C 12 ;CR 1 ;R 13 ; D 9 . Upon an overcurrent, the protective circuit  8  immediately cuts off power supply from the oscillator  6 , so as to stop voltage output. 
     The operation of the neon lamp control circuit is outlined hereinafter with reference to FIGS. 2 and 3. The power input circuit  1 , the EMI eliminator circuit  2 , the rectifier circuit  3  and the power factor compensation circuit  4  form a power supply circuit, which changes AC220V or AC110V to a DC voltage. The DC voltage is then shunt through R 1 ;W 1 ;C 7  into about a DC1-2V working voltage. The working voltage thus obtained is provided to the function control circuit  5 , the oscillator  6 , the exciting circuit  7  and the protective circuit  8 . 
     When the function control panel outputs a high potential signal “1”, it is transmitted to pins  1  and  2  of G 01 , thereby causing pin  3  of G 01  to output a low potential signal “0”. On the contrary, When the function control panel outputs a low potential signal “0”, pin  3  of G 01  is driven to output a high potential signal “1”. The output signal from pin  3  of G 01  is then transmitted to pin  11  of IC 1  through D 10 , causing pin  10  of IC 1  to output a reversed signal to control the oscillator, which is formed of IC 1 ;C 8 ;R 2 . When the function control panel outputs a high potential signal “1”, the oscillator is driven output high frequency signal. On the contrary, when the unction control panel outputs a low potential signal “0”, the oscillator does no work. Upon receipt of a high frequency signal by the oscillator, pins  2 ,  4  and  6  of IC 1  output a reversed phase signal to the frequency compensation circuit, which is formed of R 3 ;C 9 , enabling its frequency characteristics to be improved. The output signal from IC 1  is then transmitted to an insulating transformer B 1 , causing the primary and secondary ends of the insulating transformer B 1  to output high frequency signals of reversed phase and equal amplitude value to drive the metal-oxide-semiconductor field effect transistors G 1 ;G 2 , causing G 1 ;G 2  to be alternatively turned on/off. When G 1 ;G 2  are alternatively turned on/off, a high frequency square wave signal is produced at the primary end of the booster transformer B 2 , causing the secondary end of the booster transformer B 2  to output a component high frequency square wave to the conductive coating layer of the neon lamp tube, therefore a static electric field is produced inside the neon lamp tube to ionize the inert gas. When the inert gas is ionized, the fluorescent material inside the neon lamp tube is stricken to emit light. 
     When electric current is increased at G 1 ;G 2  due an overload or an abnormality of the circuit, the sampling voltage at R 10  is relatively increased. When the value of the electric current surpasses the grid electrode voltage of SCR 1 , namely, 0.7V, SCR 1  is turned on to output a low voltage through its anode electrode. The low voltage from SCR 1  is transmitted through D 9  to pin  9  of IC 1 , causing the oscillator to stop working, and therefore output voltage is cut off. When returning the circuit to normal operation, AC power supply must be cut off before examining the circuit and the load. 
     A pulse width modulation and scanning control circuit in accordance with the present invention, as shown in FIGS. 4 and 5 (FIG. 4 is a circuit block diagram of the pulse width modulating and scanning control circuit; FIG. 5 is a detailed circuit diagram of the pulse width modulation and scanning control circuit) is generally comprised of a scanning cycle generator  11 , an oblique wave generator  12 , a pulse width modulator  13 , an input circuit  14 , a high frequency switch  15 , an output circuit  16 , and a power supply unit  17 . 
     The scanning cycle generator  11  is comprised of IC 2 ;R 51 ;R 52 ;R 53 ;D 52 ;C 52 , and controlled to generate the desired scanning cycle and reversing time signal. The reversing time is changeable through R 51 . The scanning cycle is changeable through R 52 ;R 53 . C 52  can be operated to adjust the reversing time as well as the scanning time. The oblique wave generator  12  is comprised of R 56 ;R 57 ;R 58 ;R 59 ;R 60 ;R 61 ;R 62 ;W 51 ;Q 51 ;Q 52 ; Q 53 ;C 56 . Q 52 ;R 57 ;R 58 ;R 59 ;C 56  form a constant current charging circuit. W 51  controls the maximum pulse width. C 56  produces an oblique wave voltage of good linearity to control the pulse width modulator  13 . The pulse width modulator  13  is comprised of IC 2 ;R 54 ;R 55 ;D 53 ;C 53 ;C 55 . The pulse signal which comes from the oblique wave generator  12  and modulated by the pulse width modulator  13  is then sent through the input circuit  14 , which is comprised of D 54 ;R 57 , to excite the high frequency switch  15 , thereby causing the output circuit  16  to output a high frequency pulse signal to the neon lamp tube, and therefore the neon lamp is driven to emit light. The high frequency switch is formed of metal-oxide-semiconductor field effect transistors for the advantage of good switching characteristics. The variation of pulse width achieves the scanning function of the neon lamp tube. The circuit is controlled by switching to provide three function status: (1) normal lighting, (2) scanning function, and (3) flashing function. The power supply unit  17  can be a DC power supply device, or an AC adapter which rectifies AC power supply into the desired voltage level. 
     The scanning cycle generator  11  which is comprised of IC 2 ;R 51 ;R 52 ;R 53 ;D 52 ;C 52  provides an adjustable square wave signal through pin  5  of IC, switch K 1 -b and R 56  to control opening/closing of Q 51 , so as to further control charging/discharging of C 56 . When pin  5  of IC 2  outputs a low voltage, Q 51  is off, a constant current from a constant current source, which is formed of Q 52 ;R 60 ;R 58 ;R 59 , is provided to K 1 -C, causing it to charge C 56 . When C 56  is charged, the base of Q 53  obtains an oblique wave voltage, thereby causing the emitter of Q 53  to output a voltage, enabling the voltage to be shunt by R 62 ;R 51 , and then sent to pin  11  of IC 2 . IC 2 ;R 54 ;R 55 ; D 53 ;C 53 ;C 55 ;R 62  form a pressure control oscillator. When the control voltage is changed within a limited range, the variation of electric induction of C 53  (i.e., pulse width variation) during charging time is greater than that during discharging time. Therefore, when the voltage linearity of pin  11  of IC 2  is changed, pin  9  of IC 2  outputs a pulse width variable pulse signal to the grid electrode of switching transistor Q 54  via the input circuit, causing Q 54  to be turned on/off, and therefore a high frequency high voltage pulse width variable pulse signal is given to the transparent conductive coating layer of the glass tube of the neon lamp. When a high frequency high voltage pulse width variable pulse signal is given to the transparent conductive coating layer of the glass tube of the neon lamp, a static electric field with a variable linearity is produced inside the neon lamp tube to ionize the inert gas, causing the fluorescent material inside the neon lamp tube to be stricken to emit light. Because the linearity of the static electric field is variable, the linearity of the area where the inert gas is ionized is variable, therefore the lighting length of the neon lamp tube varies with the pulse width. 
     As indicated above, the present invention controls the scanning function of the neon lamp by means of weak signal, and decides the initial scanning point of the neon lamp by changing the arrangement of the transparent conductive coating layer on the glass tube of the neon lamp. 
     It will be understood that each of the elements described above, or two or more together may also find a useful application in other types of methods differing from the type described above. 
     While certain novel features of this invention have been shown and described and are pointed out in the annexed claim, it is not intended to be limited to the details above, since it will be understood that various omissions, modifications, substitutions and changes in the forms and details of the device illustrated and in its operation can be made by those skilled in the art without departing in any way from the spirit of the present invention. 
     Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.