Abstract:
An electronic device for starting and/or re-starting a power-driven device such as a lamp, bulb or lighting fixture includes an input stage, a rectifier stage, a power factor correction stage with total harmonic distortion correction, and a coil device comprising a wound coil having a primary winding of multistranded wire. The circuit may automatically adjust to a range of loads, and/or it may provide an auto-ranging line voltage. In an embodiment, the input stage accepts an AC input signal, the rectifier stage converts the AC input signal to a DC signal, and the coil device converts the DC signal to an AC output signal. The device may also include a frequency adjustment circuit that adjusts the frequency of the AC output signal to assistance in the performance of a restart function.

Description:
RELATED APPLICATIONS  
       [0001]     This application claims priority to, and incorporates by reference, U.S. provisional patent application No. 60/466,995, filed May 1, 2003, and U.S. provisional patent application No. 60/476,535, filed Jun. 6, 2003. 
     
    
     TECHNICAL FIELD  
       [0002]     This application relates to electronic lighting systems. More specifically, the present invention relates to an electronic controller for striking, restriking and/or dimming a power-driven device such as a lamp, bulb or other lighting fixture.  
       BACKGROUND  
       [0003]     Electronic controllers such as ballasts are commonly used for starting and restarting large lighting fixtures, such as those found in street lights, warehouse stores and the like. To start and/or restart such a lighting fixture, a ballast that delivers a very high current, and thus a very high power, has been required. This requirement significantly increases operating costs, especially when additional power is required to turn on a light. It also reduces the life of the bulb since a high current spike can stress and degrade the filament and/or gas contained within the bulb. Further, the conventional ballast is heavy and must be located near the bulb unless a very substantial wiring system is installed throughout the building or other location in which the bulbs are installed.  
         [0004]     Thus, it is desirable to develop an improved electronic lamp driver system that delivers a low start up current that is still capable of striking and restriking hot a bulb in a large lighting fixture such as lighting fixtures having bulbs in the range of 100 watts to 2000 watts.  
       BRIEF SUMMARY  
       [0005]     A preferred embodiment of the invention provides an electronic device for starting and/or re-starting a power-driven device such as a lamp, bulb or lighting fixture. In an embodiment, the device includes an input stage, a rectifier stage, a power factor correction stage, and a coil device comprising a wound coil having a primary winding of multistranded wire. The circuit may automatically adjust to a range of wattages and/or loads. In an embodiment, the input stage accepts an AC input signal, the rectifier stage converts the AC input signal to a DC voltage level, and the coil device converts the DC signal to an AC output signal.  
         [0006]     The power factor correction stage may include a single-stage or a two-stage power factor correction controller. The device may also include a feedback stage, a filter stage, an output stage including a ballast controller and one or more MOSFETs, and/or a frequency adjustment circuit that adjusts the frequency of the AC output signal. In an embodiment, at least one of the stages includes a thermal cutout component. The power factor correction stage may also include a coil device having a primary winding of multistranded wire.  
         [0007]     The output coil device may be a choke or transformer when the device is used to control the delivery of power to one or more non-fluorescent bulbs. Alternatively, the coil device may include a secondary winding and serve as a transformer for the delivery of power to one or more fluorescent lamps.  
         [0008]     In an embodiment, the circuit may include an input stage, a rectifier stage, and a power factor correction stage, and it may provide an auto-ranging line voltage for the operation of a variety of loads. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  illustrates an embodiment of the present inventive lamp driver, in this illustration showing the driver being used to drive a non-fluorescent lamp, with an optional alternate output for two sets of fluorescent lamps, also shown.  
         [0010]      FIG. 2  illustrates an alternate embodiment of the lamp driver, in this case driving one non-fluorescent lamp and two fluorescent lamps.  
         [0011]      FIG. 3  illustrates input and filter stages of the embodiment of  FIG. 1 .  
         [0012]      FIG. 4  illustrates elements of the DC rectifier stage of  FIG. 1 .  
         [0013]      FIG. 5  illustrates exemplary elements of the power factor correction stage of  FIG. 1  and the high voltage power filter stage of  FIG. 1 .  
         [0014]      FIG. 6  illustrates exemplary elements of the output stage of  FIG. 1 .  
         [0015]      FIG. 7  illustrates a prior art dimming circuit.  
         [0016]      FIG. 8  illustrates an embodiment of the feedback stage of  FIG. 1   
         [0017]      FIG. 9  illustrates an embodiment where the lamp driver drives a non-fluorescent lamp.  
         [0018]      FIG. 10  illustrates an embodiment where the lamp driver drives multiple fluorescent lamps.  
         [0019]      FIG. 11  is a block diagram of a prior art power factor correction circuit. 
     
    
     DETAILED DESCRIPTION  
       [0020]     An embodiment of the present inventive lamp driver system is illustrated in  FIG. 1 . As indicated in  FIG. 1 , the exemplary system  100  may include as many as seven stages or more, each of which may provide additional features for the system.  
         [0021]     Referring to  FIG. 1 , in the illustrated embodiment the first stage of the device  10  receives an input voltage and operates as an AC power supply. The input stage  10  may accept an input voltage that is at least between the range of 80 and 300 volts, with signal frequencies at approximately 50 to 60 kHz, although other voltages and frequencies are possible depending on the application. The second stage  20  functions as electromagnetic interference (EMI) filter. The third stage  30  functions as a DC rectifier, converting the AC input voltage to a DC voltage, with a connection to a feedback circuit. The fourth stage  40  operates as a power factor correction stage. The fifth stage  50  operates as a high-voltage power filter. The sixth stage  60  operates as the output stage to deliver power to one or more lamps or other devices. The seventh stage  70  is a general feedback stage. Although  FIG. 1  as illustrated defines a boundary for the feedback stage  70 , the boundary is only intended to illustrate a portion of the feedback stage  70 . In fact, feedback is typically provided to each of stages  30 ,  40 ,  50  and  60 .  
         [0022]     As illustrated in  FIG. 2 , in an alternate embodiment an external power source  110  that is not generally considered to be a stage of the device  100  may be provided. In the embodiment of  FIG. 2 , power source  110  provides a low-voltage power source for the electronic devices in device  100 .  FIG. 2  illustrates stages in a manner using a numbering system showing their correspondence to  FIG. 1 .  
         [0023]      FIG. 3  through  FIG. 10  provide additional detail of embodiments of the individual stages described above and illustrated in  FIG. 1 . The values listed below for individual elements are exemplary values only and should not be interpreted as limiting. Persons skilled in the art will recognize that other values are possible without departing from the spirit and scope of the invention.  
         [0024]     Exemplary elements of input stage  10  and second stage  20  are illustrated in  FIG. 3 . Referring to  FIG. 3 , input stage  10  includes a power source, optionally between 80 and 300 volts and at signal frequencies between about 50 and about 60 kHz, or plug  16  at AC inputs  11 A and  11 B, a line fuse  12 , and two varistors  13  and  14 . In the illustrated embodiment, the power source may be a 120V, 50/60 kHz voltage source, and the line fuse  12  may be a 1.5 A fuse for a driver for a 150 watt lamp. When the circuit is used to light higher intensity lamps, larger fuses may be needed, such as a 5 amp fuse for a 400 watt bulb. Varistors or zener diodes  13  and  14  may function as surge protection devices connected between each of the AC inputs and ground  17 . When a power surge or voltage spike is exhibited on the AC inputs, the resistance of varistors or zener diodes  13  and  14  may quickly decrease, creating a shunt path for the over-voltage. In this way, other components in the device may be protected from power surges.  
         [0025]     The EMI filter stage  20  of the device may function as a noise filter. In the filter stage, an LC filter may be replicated between each AC input  11 A and  11 B and ground. The LC filters operate as noise filters to remove unwanted frequencies from the AC voltage input source. The LC filters may be composed of optional inductors  21  and  22  (not shown in  FIG. 3 , but shown in the embodiment of  FIG. 2 ), and capacitors  23  and  24 . In an embodiment, the inductors  21  and  22  may have an inductance of approximately 600 nH, and capacitors  23  and  24  may have a capacitance of approximately 2.2 nF. Capacitor  25  may have a capacitance of 0.15 μF. Other values are possible without departing from the spirit and scope of the invention.  
         [0026]     The DC rectifier stage  30  may convert the AC input signal into a DC voltage. Exemplary elements of the DC rectifier stage  30  are illustrated in  FIG. 4 . Diode bridge  31  functions as a full wave bridge and converts the AC input voltage into a DC output voltage. Diode bridge  31  may be made of a full wave rectifier, or it may be four separate diodes, such as 4-amp diodes. The use of separate diodes instead of a rectifier is preferred for higher wattage drivers. Diode bridge  31  may be connected to the feedback stage  70  via the ground plane. The connection between diode bridge  31  and ground may stabilize the voltage differential across the bridge. Optional thermal cutout component  32  may operate as a temperature-sensitive, protective device to shut down the operation of diode bridge  31  in certain thermal conditions. For example, thermal component  32  may trigger a shut down when it senses an external temperature of 105° C., which may indicate a fire.  
         [0027]     Exemplary elements of the power factor correction stage  40  are illustrated in  FIG. 5 . A coil device  41  operates to boost the output voltage based on the lamp or lamps (or other device or devices) attached to the output of device  100 . A coil device  41  using multistranded wire is described in co-pending U.S. patent application Ser. No. 10/______, entitled “Coil Device”, filed Apr. 29, 2004, which is incorporated herein by reference in its entirety. Other coil devices are possible without departing from the spirit and scope of the invention. The coil device preferably includes a secondary winding when it is used as a power circuit for the ballast. The power factor correction circuit may be used to make a nonlinear load operate like a resistive load by putting it into phase. This correction may also help to reduce total harmonic distortion. In one embodiment, the power factor correction controller  42  may be a Fairchild Semiconductor FAN7527 or similar device. The power factor correction controller  42  may be used along with one or more resistors  44 - 48 ; one or more capacitors  49 ,  141  and  144 ; one or more diodes  142  and  143 ; a coil device  41 ; and MOSFET  145  to create a power factor correction circuit.  
         [0028]     In one embodiment corresponding to  FIG. 2 , resistors  43 ,  44 ,  45 ,  46 ,  47  and  48  may have resistances of approximately 150 kΩ, 47 Ω, 22 kΩ, 2.1 MΩ, 14.7 kΩ and 1 Ω, respectively, and capacitors  49 ,  141  and  144  may have capacitances of approximately 0.01 μF, 100 MF and 0.22 μF, respectively with capacitor  145  and its corresponding wiring not being present. In an alternate embodiment corresponding to  FIG. 1 , resistors  43 ,  44 ,  45 ,  46 ,  47  and  48  may have values of approximately 180 Ω, 10 Ω, 22 kΩ, 2.2 MΩ, 27 kΩ, and 0.25 Ω, respectively, while capacitors  49 ,  141 ,  144  and  145  may have values of approximately 1 nf, 0.47 μF, 1 μF and 1 MF, respectively. The embodiment shown in  FIGS. 1 and 5  may also include a diode  151 .  
         [0029]     In the embodiment illustrated in  FIG. 5 , the power factor correction device  42  includes a two-stage power factor correction microchip. An example of such a microchip is the FAN7527B supplied by Fairchild Semiconductor. Unlike the prior art, which used three-stage or other microchips, the two-stage microchip provides several advantages in that it uses substantially the same frequency for pre-startup heating and actual startup, thus providing a power saving advantage. The pre-startup heating and actual startup frequency may each be, for example, approximately three times normal operating frequency. The operation of a prior power factor correction circuit is described in Fairchild Application Note AN4107, published May 2000, and is illustrated in  FIG. 11 .  
         [0030]     Exemplary elements of a high voltage power filter stage  50  are also illustrated in  FIG. 5 . For a 150 watt unit, stage  50  may incorporate resistor  51  and variable resistor  52 . In an embodiment, resistor  51  may have a resistance of about 1.1 MΩ, and variable resistor  52  may have a peak resistance of about 10 kΩ. The optional variable resistor  52  may be used to adjust the frequency of the output signal by changing its voltage, since a higher voltage will result in a higher frequency. A higher frequency may also change the wavelength of the output signal. Optional resistor  148 , such as a 6 kΩ resistor, may also be used. In an embodiment, the frequency of the output signal may be varied so that the lamp or lamps connected to the output of the ballast device may create light emissions of varying wavelengths, selected based on the attributes of the bulb or load to be driven. For example, a high pressure sodium bulb may handle a lower frequency, such as 20-40 kHz, while a xenon bulb may require a higher frequency, such as 150 kHz or more. In an alternate embodiment, the variable resistor may be set to a constant value to achieve a known frequency and create light emissions of a known wavelength. Capacitor  53  illustrated in  FIG. 5  may have a resistance of between 47 MF and 100 MF. Other values are possible.  
         [0031]     Preferred elements of an output stage  60  are illustrated in  FIG. 6 . Referring to  FIG. 6 , a controller  61  may be implemented by a ballast controller such as a Fairchild Semiconductor KA7540 or KA7541 or a similar device. The controller  61  is used to produce the high output voltage required to drive the output MOSFETs  62  and  63  in conjunction with a standard gate driver  64 . The MOSFETs  62  and  63  blend the injected frequency component output from stage  50  and the high voltage driven from the standard gate driver  64  to produce the proper signal to the lamps and/or bulbs. The drain port of MOSFET  62  is driven by stage  50  at a high voltage (such as 400 volts) and receives a pulse input at a frequency determined by the variable resistor  52 . The resulting output of MOSFETs  62  and  63  may be a switching DC square wave or substantially square wave.  
         [0032]     Preferred, although not required, values for various elements in  FIG. 6  are that resistors  263 ,  65 ,  66 ,  67 ,  68  and  69  may be approximately 51 Ω, 51 Ω, 150 KΩ, 22 KΩ, 51 Ω and 51 Ω, respectively. Variable resistors  261  and  262  may each have values of up to 1 KΩ. Capacitors  162 ,  163 ,  164 , and  165  may be approximately 100 pF, 0.22 μF, 47 MF, and 0.27 μF, respectively. Varistor  167  may be a 15 volt Zener diode. Diodes  265 ,  266 ,  267  and  268  may be, for example, 300 volt diodes. In each case, other values are possible.  
         [0033]     The use of a Fairchild Semiconductor KA7540 as controller  60  may allow for enhanced restriking capability when the circuit is used for non-fluorescent bulbs. However, in an alternate embodiment, a different controller  61  such as a Fairchild Semiconductor KA7541 may be used. In such a case, one skilled in the art will recognize that the dimming circuit inside the KA7540 is not present in the KA7541, and that such dimming capability may need to be replicated or otherwise added to the lamp driver in order to restrike a non-fluorescent bulb. An illustration of the prior art dimming circuit of the KA7450, as presented in the Fairchild Semiconductor product specification, is presented in  FIG. 7 . Another option may be to include a capacitor which will allow a high starting current with gradual dimming.  
         [0034]     Referring to  FIG. 8 , feedback stage  70  is a general feedback stage in which the output voltage level is transmitted to other stages to permit for corrections in the total voltage differential in the circuit. Referring to  FIG. 8 , exemplary values for resistors  71 ,  72 ,  73 ,  74 ,  75 ,  76 ,  77  and  78  are maybe 10 KΩ, 100 KΩ, 442 KΩ, 220 KΩ, 180 KΩ, 10 KΩ, 200 KΩ and 442 KΩ, respectively, while exemplary values of capacitors  171 ,  172 , and  173  may be 1 nF, 1 mF and 1 nF, respectively. Other values are possible. Optional indicator light  177  may provide an indication of when the bulb is restriking. The feedback stage  70  may also serve as a circuit to turn off MOSFETs  62  and  63  when a bulb is not installed in the system. Although  FIG. 8  illustrates a boundary for the feedback stage  70 , the boundary is only intended to illustrate a portion of the feedback stage  70 . In fact, feedback is typically provided to each of stages  30 ,  40 ,  50  and  60 .  
         [0035]     The output waveform of the device may drive one or more lamps, one or more bulbs, or any combination of the two or other devices. Referring to  FIG. 9 , if one or more non-fluorescent bulbs  91  are driven, a coil device  82  similar to the one illustrated in stage  40  may be used to convert the DC square wave output from stage  60  of the ballast device into an AC sine wave. An exemplary coil device  82  is the multistranded wire device with a secondary winding as illustrated in pending U.S. patent application Ser. No. 10/______, filed Apr. 29, 2004, entitled “Coil Device”, which is incorporated herein by reference in its entirety. Such a device may include a primary winding of multistranded wire, such as that commonly known as litz wire. The coil device includes a conductive core positioned inside the primary winding and outside the primary winding. The core that is positioned inside the primary winding may include an air gap. The primary winding is preferably covered by an insulating layer. In this case, a secondary winding may not be required and the device may be used as a choke.  
         [0036]     Referring again to  FIG. 9 , exemplary values for capacitors  95  and  96  are 0.68 μF (for a 400 volt line) and 0.012 μF, respectively.  
         [0037]     Referring to  FIG. 10 , if one or more fluorescent lamps  90 A- 90 D are driven, the coil device  81  illustrated in co-pending U.S. patent application Ser. No. 10/______, entitled “Coil Device”, filed Apr. 29, 2004, may also be used. An optional secondary winding may also be provided around the primary winding to allow the device to operate as a transformer. Optionally, the secondary winding may also be made of multistranded wire.  
         [0038]     If two or more fluorescent lamps are connected, they may be connected in series as illustrated in  FIG. 10 . Each combination of two fluorescent lamps preferably has a single associated coil device. If two or more non-fluorescent bulbs are used (such as metal halide bulbs), each non-fluorescent bulb preferably has its own coil device as illustrated in  FIG. 9 . Additional configurations with additional lamps are possible.  
         [0039]     The present inventive ballasts may be used to light a variety of bulbs, and in an embodiment the ballasts automatically adjust to the value of the load. Thus, one ballast can be used to operate lamps of varying wattages, such as those ranging from 150 watts to 400 watts in an embodiment. Optionally, it may also be lighter in weight than many conventional ballasts.  
         [0040]     In examples, in one embodiment the lamp driver was used in connection with a ballast controller to light a metal halide lamp, and it was found that the device automatically adjusted to a 1-amp current flow for a 150-watt lamp and a 3.4-amp current flow for a 400-watt lamp. Certain embodiments of the lamp driver may be separated from the lamp by a wire distance of as much as 200 feet or more without any significant loss of output.  
         [0041]     It is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in this description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Hence, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.  
         [0042]     As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods, and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.