Patent Publication Number: US-6703795-B2

Title: Auxiliary controller

Description:
TECHNICAL FIELD 
     This invention relates to an auxiliary lighting controller for a lighting system. 
     BACKGROUND 
     An auxiliary lighting system may illuminate an auxiliary lamp to supplement a high intensity discharge (HID) lamp from the time that the HID lamp is activated until the HID lamp achieves full illumination, which may require several minutes. Whenever the HID lamp is deenergized by, for example, a momentary power failure, the HID lamp requires several minutes to cool off before it can be turned back on to provide illumination. 
     A circuit to control an auxiliary lamp may use a current transformer to sense the HID lamp current in order to determine whether the HID lamp is “on.” The current transformer actuates a mechanical relay to provide power to the auxiliary lamp as appropriate. 
     SUMMARY 
     In one general aspect, a lighting system includes a primary lamp circuit, an auxiliary lamp circuit, and an auxiliary controller. The auxiliary controller is connected between the primary lamp circuit and the auxiliary lamp circuit and is operable to sense a voltage of the primary lamp circuit. The auxiliary lamp circuit includes an auxiliary lamp. The auxiliary controller operates to extinguish the auxiliary lamp when the voltage of the primary lamp circuit exceeds a threshold voltage. 
     Implementations may include one or more of the following features. For example, the primary lamp circuit may include an impedance element in series connection with a discharge lamp. The impedance element may be a ballast capacitor or a ballast reactor. 
     The primary lamp circuit also may include a high intensity discharge lamp, such as a gas vapor lamp. The auxiliary lamp may be an incandescent lamp. 
     The auxiliary controller may have output leads that are connected to the auxiliary lamp. The auxiliary controller also may have input leads that are connected across the impedance element. 
     In another general aspect, an auxiliary controller for a lighting system includes a power supply circuit, a switching circuit, and a coupling circuit that connects the power supply circuit to the switching circuit. The power supply circuit has input and output voltages and the switching circuit has open and closed states. An increase in the input voltage beyond a certain threshold causes an increase in the output voltage that biases the switching circuit in the open state. 
     The power supply circuit may have input terminals for connection to an alternating current voltage. An impedance capacitor may be connected in series with one of the input terminals to provide impedance to the alternating current voltage. A diode bridge may be connected to the impedance capacitor and to the input terminals. The diode bridge may produce unfiltered direct current voltage from the alternating current voltage. 
     A filter capacitor may be connected across the diode bridge to remove ripple voltages and produces a steady direct current voltage. A zener diode may be connected across the filter capacitor to clamp the direct current voltage to a predetermined level. Output terminals may be connected across the zener diode, and a current limiting resistor may be connected in series with the output terminals. 
     The coupling circuit of the auxiliary controller may have an optically isolated triac that has open and closed states. Increasing the power supply circuit input voltage above a threshold voltage may increase the power supply output voltage to bias the optically isolated triac in the closed state. 
     The switching circuit of the auxiliary controller may have a voltage divider that is connected to the coupling circuit. A triac may be connected to the voltage divider by a diac. The triac may be triggered into conduction when a breakover voltage on the diac is exceeded. 
     In another general aspect, operating a lighting system includes providing a primary lamp circuit, providing an auxiliary lamp circuit, connecting an auxiliary controller between the primary lamp circuit and the auxiliary lamp circuit, sensing a primary lamp circuit voltage, and extinguishing an auxiliary lamp when the primary lamp circuit voltage exceeds a threshold voltage. The primary lamp circuit, the auxiliary lamp circuit, and the auxiliary controller may have some or all of the features described above. 
     The current implementation eliminates the need for a current transformer from the auxiliary lighting system, which can reduce costs, weight, and bulk, and can improve performance. 
     The details of one or more implementations are set forth in the drawings and the description. Other features and advantages will be apparent from the description, including the drawings and the claims. 
    
    
     DESCRIPTION OF DRAWINGS 
     FIG. 1 is a block schematic diagram of a lighting system. 
     FIGS. 2-4 are schematic diagrams of the lighting system of FIG.  1 . 
     FIG. 5 is a flow chart of a procedure for operating the auxiliary lamp using the lighting system of FIG.  1 . 
     FIG. 6 is a schematic diagram of a timer circuit for the lighting system of FIG.  1 . 
     Like reference symbols in the various drawings indicate like elements. 
    
    
     DETAILED DESCRIPTION 
     Referring to FIG. 1, a lighting system  100  includes a power supply  104 , a primary lighting system  106 , an auxiliary controller  108 , an auxiliary lamp  110 , and an auxiliary power supply  112 . The power supplies typically are 120-volt alternating current (a.c.) sources. 
     The power supply  104  is connected to the primary lighting system  106  and energizes the primary lighting system  106 . The auxiliary controller  108  is connected by input leads  122  to the primary lighting system  106  to monitor the condition of the primary lighting system  106 . In the event that auxiliary lighting is desired, the auxiliary controller  108  provides a conductive path through output leads  124  to allow the auxiliary power supply  112  to energize the auxiliary lamp  110 . 
     Referring to FIG. 2, the primary lighting system  106  includes an HID lamp  114 . The primary lighting system  106  also includes a ballast component. In the implementation shown in FIG. 2, the power supply  104  is connected to a ballast primary  116  of a ballast transformer  117 , and the ballast secondary  118  of the ballast transformer  117  is connected to a ballast capacitor  120  that is in series with the HID lamp  114 . The ballast transformer  117  transforms the voltage provided by the power supply  104  to permit use on a system with a different voltage from what is required to properly operate the HID lamp  114 . 
     The HID lamp  114  has an inner gas-filled tube through which an arc path strikes or starts the lamp. Once the arc has been established, the HID lamp  114  can have a “negative” resistance since the voltage drops as the current increases. The ballast  117  in conjunction with the capacitor  120  controls and limits the current flow to prevent a runaway current condition. 
     As shown in FIG. 2, the ballast transformer  117  is an autotransformer having a common winding. In other implementations, the ballast transformer  117  may be eliminated, may have isolated primary and secondary windings, or may have three windings. In a further implementation, the ballast capacitor  120  may be replaced by another component, such as, for example, a choke coil. A starter circuit (not shown) also may be employed to provide a high-voltage, low-power pulse to strike the arc and start the HID lamp  114 . 
     Referring to FIG. 3, the input leads  122  of the auxiliary controller  108  are connected across the ballast capacitor. One output lead  124  is connected to a tap  125  on the ballast primary  114 . The other output lead is connected to the auxiliary lamp  110 , which is connected to the power supply neutral  127  to provide the auxiliary power source  112 . In the implementation shown in FIG. 3, the auxiliary lamp  110  is a quartz lamp. In other implementations, the auxiliary lamp  110  may be another type of lamp having instant-on characteristics, such as, for example, an incandescent lamp. 
     Referring to FIG. 4, the auxiliary controller  108  may be implemented as a solid-state circuit with three sub-circuits that include a power supply circuit  126  that is connected by a coupling circuit  128  to a switching circuit  130 . The power supply circuit  126  includes a capacitor  132 , diodes  134 , a filter capacitor  138 , a zener diode  140 , and a current limiting resistor  142 . The power supply circuit  126  uses the input leads  122  as an ac voltage source. The diodes  134  are configured in a bridge in order to convert the ac voltage to a fluctuating (unfiltered) direct current (d.c.) voltage. The filter capacitor  138  removes ripple voltages  138  for a steady d.c. voltage, and the zener diode  140  clamps the d.c. voltage to a predetermined output level. 
     The d.c. voltage from the power supply circuit  126  is applied to terminals of the coupler circuit  128 . The coupler circuit  128  is an opto-electronic triac  146  that provides isolation between the power supply circuit  126  and the switching circuit  130 . As shown in FIG. 4, a light emitting diode  148  drives the triac  146  between open and closed states. Application of d.c. voltage that exceeds a threshold level causes the triac  146  to go from open to closed states. Thus, the triac terminals  150  act as a closed switch in the switching circuit  130  as the voltage on the diode  148  exceeds the threshold voltage. 
     The switching circuit  130  includes capacitors  152 ,  154 , a diac  156 , and a triac  158 . The capacitors  152 ,  154  act as a voltage divider that controls the voltage on the diac  156 . In turn, the diac  156  drives the triac  158  between open and closed states depending on the voltage level on the diac. Closing the opto-coupled triac  146  in the coupling circuit  128  causes the input voltage of the diac  156  to drop to ground or reference voltage, which causes the triac  158  to open. The output leads  124  across the triac  158  are connected in series with the auxiliary power source  112  and the auxiliary lamp  110 . Thus, the open and closed switching action of the triac  158  extinguishes or illuminates the auxiliary lamp  110 . 
     Referring to FIG. 5, a procedure for operating a lighting system includes providing a lighting system having primary and auxiliary lamp circuits (step  210 ), providing an auxiliary controller (step  220 ), connecting the auxiliary controller between the primary and the auxiliary lamp circuits (step  230 ), sensing a voltage on a primary lamp circuit component with the auxiliary controller (step  240 ), and extinguishing an auxiliary lamp when the component voltage exceeds a threshold voltage (step  250 ). Examples of the primary lamp circuit, the auxiliary lamp circuit, and the auxiliary controller include those discussed above with respect to FIGS. 1-4. Connecting the auxiliary controller (step  230 ) includes connecting the auxiliary controller  108  across a component in series with the HID lamp  114 , such as, for example, the ballast capacitor  120  as shown above with respect to FIG.  3 . In other implementations, the auxiliary controller is connected across a choke coil that is in a series connection with the HID lamp  114 . 
     Sensing a voltage across the lamp circuit (step  240 ) may include sensing a voltage across the ballast capacitor  120 . Since the capacitor  120  is in series with the HID lamp  114 , no voltage will appear across the capacitor unless the lamp  114  is in conduction. Thus, sensing the voltage across the capacitor ( 240 ) provides an indication of the HID lamp operation. Extinguishing the auxiliary lamp (step  250 ) occurs as the voltage across the capacitor exceeds the threshold, indicating that the HID lamp  114  is illuminated. 
     Referring to FIG. 6, a timer circuit  300  can be added to the lighting system with auxiliary controller  100 . The timer circuit includes a timer microchip  304 , resistors  306 ,  308 ,  310 , and a capacitor  312 . The timer circuit  300  includes an automatic power-on reset. The timer circuit  300  can be installed between the power supply circuit  126  and the coupling circuit. When the HID lamp  114  first begins to conduct, the timer will initialize and begin to time. At the end of a pre-selected time period, power is applied to the coupling circuit  128 , which turns off the auxiliary lamp  110 . The timer chip  304  may be an MC14541B programmable timer manufactured by On Semiconductor or the chip  304  may be another type of timer, such as, for example, a 4541-timer chip made by other semiconductor industry manufacturers. 
     A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made. For example, the auxiliary controller could be configured to control any a.c. load or device that could operate other types of auxiliary equipment. Accordingly, other implementations are within the scope of the following claims.