Auxiliary controller

[0002] This invention relates to an auxiliary lighting controller for a lighting system.

[0003] 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.

[0004] 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.

[0005] 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.

[0006] 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.

[0007] 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.

[0008] 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.

[0009] 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.

[0010] 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.

[0011] 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.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] FIG. 1 is a block schematic diagram of a lighting system.

[0018] FIGS. 2-4 are schematic diagrams of the lighting system of FIG. 1.

[0019] FIG. 5 is a flow chart of a procedure for operating the auxiliary lamp using the lighting system of FIG. 1.

[0020] FIG. 6 is a schematic diagram of a timer circuit for the lighting system of FIG. 1.

[0021] Like reference symbols in the various drawings indicate like elements.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.