Brightness control system for decorative light strings

Apparatus and associated methods relate to providing a constant-brightness lighting power to one or more interconnected light strings. A light string power controller draws operating power from a power source that has a variable voltage. The light string power controller supplies constant-brightness lighting power to the one or more interconnected light strings connected thereto. The power controller can send a load-query signal the one or more interconnected light strings connected thereto. The connected light strings respond to the query with a load-response signal, which is indicative of a power level corresponding to an illumination value of the one or more interconnected light strings. The load-response signal can be indicative of a total number of lighting elements of the one or more interconnected light strings, for example. Similarly, the load-response signal can be indicative of a desired power level for a predetermined illumination level of the one or more interconnected light strings.

BACKGROUND

Decorative light strings are used to communicate a joy of a holiday season, to draw attention to merchandise, or to simply decorate or adorn an object. Decorative light strings have been used to adorn trees, shrubs, and houses. Decorative light strings are used both indoors and outdoors. In some lighting situations, power sources for such decorative light strings are difficult to tap or unavailable altogether. In such lighting situations, batteries can be used to provide power to light strings and to other decorative lights.

Batteries, however, may have a power supply capability that changes in response to changes in battery charge, ambient temperature, number of charge cycles, etc. When used to provide lighting power to decorative light strings, variations in the power supply capability of batteries can be manifest by variations in brightness of the decorative light strings. For example, the brightness of the decorative light string may decrease in response to charge depletion of the battery over time. The decorative light string may thus become less decorative over time.

SUMMARY

Apparatus and associated methods relate a system for providing constant-brightness to light elements of one or more connected decorative light strings. The system includes a light-string load detector configured to provide, via an electrically-conductive path, a load-query signal to the one or more a connected light strings. The light-string load detector is further configured to detect, via the electrically-conductive path, a load-response signal from the one or more connected decorative light strings. The load-response signal is indicative of a power level corresponding to an illumination value of the one or more connected decorative light strings. The system also includes a power converter configured to draw operating power from a power source. The power converter is further configured to provide, via the electrically-conductive path, power to the one or more connected decorative light strings. The power is provided at the power level indicated by the detected load-response signal.

Some embodiments relate to a decorative light string configured for use with a modular constant-brightness lighting system. The decorative light string includes a first electrical connector located at a first end of the decorative light string. The first electrical connector has first and second contacts. The first electrical connector is configured to receive power via the first and second contacts of the first electrical connector. The decorative light string includes a second electrical connector at a second end of the decorative light string. The second electrical connector has first and second contacts. The second electrical connector is configured to provide power via the first and second contacts of the second electrical connector. The decorative light string includes a first conductor electrically coupled to and extending between the first contact of the first electrical connector and the first contact of the second electrical connector. The decorative light string includes a second conductor electrically coupled to and extending between the second contact of the first electrical connector and the second contact of the second electrical connector. The decorative light string includes a plurality of lighting elements distributed along the decorative light string and configured to receive operating power via the first and second conductors. The decorative light string also includes a load-query responder electrically connected between the first and second conductors. The load-query responder is configured to receive a load-query signal and to provide a load-response signal in response to the received load-query signal. The load-response signal is indicative of a power level corresponding to an illumination value of the plurality of lighting elements.

Some embodiments relate to a battery module. The battery module includes a battery receiver configured to receive one or more batteries. The battery module includes an input power connector configured to mechanically and electrically couple to an upstream battery module in a series fashion. The battery module includes an output connector configured to mechanically an electrically couple to either a downstream battery module in a series fashion or to a modular constant-brightness lighting system. If the battery module is connected to the modular constant-brightness lighting system, power is provided to the constant-brightness light controller, the provided power having a voltage equal to the sum of voltages provided by connected upstream battery modules and voltage of the battery module connected to the modular constant-brightness lighting system.

DETAILED DESCRIPTION

FIG. 1is a schematic view of a home decorated with various decorative light strings controlled by an exemplary lighting controller providing for constant brightness. InFIG. 1, home10has garden12with tree14and shrubs16,18,20. Tree14is decorated with decorative light string22and decorative illuminated star24. Shrubs16,18,20are decorated with decorative light strings26,28,30, respectively. Battery modules32,34are interconnected with each other, and battery modules32,34are coupled to lighting controller36. Decorative light strings22,26,28,30and decorative illuminated star24are interconnected with one another, and interconnected decorative light strings22,26,28,30and decorative illuminated star24are coupled to lighting controller36.

Lighting controller36may have an internal power source, but can also draw operating power from battery modules32,34coupled to lighting controller36. Lighting controller36can provide constant-brightness lighting power to interconnected decorative light strings22,26,28,30and decorative illuminated star24. Each of interconnected decorative light strings26,28,30is depicted as having first light-string connector38and second light-string connector40on opposite ends of light strings26,28,30. First light-string connectors38, second light-string connector40or both first and second light-string connectors38,40may have additional connection ports to which additional light strings or other decorative lighting elements can be connected.

If additional decorative lighting elements are connected to interconnected decorative light strings22,26,28,30and decorative illuminated star24, then lighting controller36adaptively provides additional power to the interconnected decorative light strings22,26,28,30and decorative illuminated star24having such additional decorative lighting elements. Lighting controller36can sense a power drawn by interconnected decorative light strings22,26,28,30and decorative illuminated star24having such additional decorative lighting elements. Lighting controller36can then source additional power to interconnected decorative light strings22,26,28,30and decorative illuminated star24having such additional decorative lighting elements.

The amount of additional power sourced by lighting controller36is sufficient to maintain a constant brightness of interconnected decorative light strings22,26,28,30and decorative illuminated star24. In other words, the power level provides by lighting controller36to light strings22,26,28,30and decorative illuminated star34is maintained even though additional lighting elements are added. This maintained power level to light strings22,26,28,30and decorative illuminated star34is achieved by lighting controller36sourcing additional lighting power.

FIG. 2is a block diagram of an exemplary modular lighting system. InFIG. 2modular lighting system42include lighting controller36, first light-string30, second light string28, first battery module32, and second battery module34. First and second light strings30,28are interconnected one to another. First and second light string30,28each has first light-string connector38and second light-string connector40. Second light-string connector40of first light string30is electrically connected to first light-string connector38of second light string28.

First and second battery modules32,34are interconnected to one another in a similar manner to the manner in which first and second light strings30,28are interconnected to one another. In some embodiments, battery modules32,34can be interconnected in a serial fashion. In some embodiments, battery modules32,34can be interconnected in a parallel fashion. In some embodiments, battery modules32,34can be interconnected in a daisy-chain fashion.

Lighting controller36includes: light string interface44; battery module interface46, battery compartment48; power conversion and distribution module50; light string power controller52; light string current sense module54; timer56; and user interface60. Interconnected first and second light strings30,28are connected to lighting controller36via light string interface44and first light-string connector38of first light string30. Interconnected first and second battery modules32,34are connected to lighting controller36via battery module interface46.

Battery compartment48can receive one or more batteries. Power conversion and distribution module50receives power from interconnected first and second battery modules32,34or from battery compartment48or from both interconnected first and second battery modules32,34and battery compartment48. Power distribution and control module50then generates one or more supply levels for use by various components of lighting controller36.

Light string power controller52receives operating power from power conversion and distribution module50. Light string power controller52provides constant-brightness lighting power to interconnected first and second light strings30,28via light string interface44. The constant-brightness lighting power is substantially independent of a first voltage that varies with a charge of a battery received in battery compartment48, and independent of a second voltage that varies with a charge of first and second battery modules32,34, and independent of a number (e.g., two in the depicted embodiment), up to a predetermined maximum number, of interconnected light strings connected to the light-string connector. In some embodiments, the predetermined maximum number of interconnected light strings to which lighting module36can supply constant-brightness lighting power is constrained by a maximum power rating of light string power controller52. In various embodiments the maximum power rating of light string power controller52is capable of providing illuminative power to 2, 3, 5, 8 or 10 light strings.

Constant-brightness lighting power is defined to mean lighting power that is within a limited range of predetermined power level. For example, constant-brightness lighting power can mean a lighting power within plus or minus 15%, 10%, 6%, or about 3% of a target lighting power, for example. In some embodiments, constant-brightness lighting power can mean lighting voltage within plus or minus 12%, 10%, 5%, or about 3% of a target lighting voltage, for example.

Light string current sensor54can sense a current drawn by interconnected first and second light strings30,28. Light string current sensor can then generate a signal indicative of the sensed current drawn by interconnected first and second light strings30,28. Light string current sensor can then output the generated signal indicative of the sensed current drawn by interconnected first and second light strings30,28to light string power controller52. Light string power controller52can then change, if necessary, a lighting power so as to maintain the constant-brightness lighting power provided to the first and second light strings30,28.

Such adaptive control of lighting power can maintain constant brightness of first and second light strings30,28even should some LEDs of first and second light strings fail. Such adaptive control of lighting power can maintain constant brightness of first and second light strings30,28even should additional light strings be added. Such adaptive control of lighting power can maintain constant brightness of first and second light strings30,28even should one of first and second light strings30,28be removed.

Adaptive control of lighting power has other advantages. For example, adaptive control of lighting power can maintain a constant brightness of light strings30,28through changes in an ambient temperature. For example, a current-voltage relation in a light string can change in response to a changing ambient temperature. If the current-voltage relation of a light string changes, open loop power control can result in non-constant brightness of the light string. But by sensing both a current drawn by the light string and a voltage across the light string, a power can be measured. In some embodiments, the power can then be adaptively controlled to maintain constant brightness in the light string.

Timer56can generate timing signals and provide such timing signals to light string power controller52. Light string power controller52can respond to such timing signals, for example, by turning on first and second light strings30,28, turning off first and second light strings30,28, dimming first and second light strings30,28, etc. Such timing signals may be used to change colors of first and second light strings30,28, for example. In some embodiments, such timing signals may be used to make first and second light strings30,28flash on and off in some predetermined fashion. Timer56may generate a command signal indicative of a specific lighting command and/or function.

User interface60may include user output devices and/or user input devices. Examples of output devices can include a display device, a sound card, a video graphics card, a speaker, a cathode ray tube (CRT) monitor, a liquid crystal display (LCD), a light emitting diode (LED) display, an organic light emitting diode (OLED) display, or other type of device for outputting information in a form understandable to users or machines. Examples of input device(s)48can include a mouse, a keyboard, a microphone, a camera device, a presence-sensitive and/or touch-sensitive display, or other type of device configured to receive input from a user.

In some embodiments, user interface60may be in a form of a communications port. User interface60, in one example, utilizes one or more communication devices to communicate with external devices via one or more networks, such as one or more wireless or wired networks or both. User interface60can be a network interface card, such as an Ethernet card, an optical transceiver, a radio frequency transceiver, or any other type of device that can send and receive information. Other examples of such network interfaces can include Bluetooth, 3G, 4G, and WiFi radio computing devices as well as Universal Serial Bus (USB).

FIG. 3is a circuit schematic diagram of an exemplary constant-brightness decorative lighting system. InFIG. 3, light string power controller52includes battery B1, LED lighting controller U1, switching power supply U2, current sense resistor RSENSE, and light string LS. Output VOUTof switching power supply U2provides operating power to light string LS. Output VOUTof switching power supply U2is also coupled to node VSENSEof LED lighting controller U1. A voltage across current sensing resistor RSENSEis indicative of the current through light string LS. The voltage across RSENSEis provided to node ISENSEof LED lighting controller U1and node ISENSEof switching power supply U2. In some embodiments, switching power supply U2uses the ISENSEsignal for fast, closed-loop control of the LED current. In some embodiments, lighting controller U1uses the signal for fine-tuning of the LED current and/or to detect low-battery charge conditions.

LED lighting controller U1generates control signal VCTRL, based on the signals received on nodes VSENSEand/or ISENSE. The generated control signal VCTRLis then output to input pin VINof switching power supply U2. Control signal VCTRLis indicative of a desired lighting power. Switching power supply U2receives the control signal VCTRLindicative of the desired lighting power on node VIN. Switching power supply U2generates a constant-brightness lighting power and supplies the constant-brightness lighting power to light string LS via output node VOUT. Both switching power supply U2and LED lighting controller U1receive operating power from battery B1.

Various embodiments can use various means for providing constant-brightness lighting power to an interconnected number of light strings. In some embodiments, light string power controller52can generate and provide constant-brightness lighting power. In some embodiments, light string power controller52can include any one or more of a microprocessor, a controller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other equivalent discrete or integrated logic circuitry. In some embodiments, light string power controller52may generate a digital signal indicative of a constant-brightness lighting power. A digital-to-analog converter can then convert the digital signal indicative of the constant-brightness lighting power to an analog power signal supplying the constant-brightness lighting power.

FIG. 4is a block diagram of an exemplary constant-brightness lighting system. The constant-brightness lighting system depicted inFIG. 4is a simplified version compared with the modular lighting system depicted inFIG. 2. InFIG. 4, constant-brightness lighting system54includes light string56and light-string controller58. Light string56is connected to light-string controller58at first end60of light string56. At second end62of light string56is light string connector64. Light string connector64is configured to connect to additional interconnected lighting elements.

Light-string controller58has battery compartment configured to receive one or more batteries. The received batteries can provide operating power to light-string controller58which provides a portion of such operating power to light string56in the form of lighting power. Light-string controller58includes switching supply66, load sensor68, and memory module70. Switching supply66and load sensor68are in electrical communication with light string56. Load sensor68is configured to sense a signal indicative of a brightness of light string56. Load sensor68may provide the sensed signal indicative of the brightness of light string56to switching supply66. In some embodiments, load sensor68can generate a new signal indicative of the brightness of light string56and provide the generated new signal to switching supply66. For example, load sensor may amplify and/or filter the sensed signal before providing the generated new signal to switching supply66.

Switching supply66can compare the received signal indicative of the brightness with a target signal72. Target signal72can be retrieved from memory58and/or it can be calculated by switching supply66. In some embodiments, target signal72can be calculated based on the received signal indicative of the lighting brightness. For example, the signal indicative of the lighting brightness may include a signal indicative of a number of lighting elements. The target brightness may be calculated to vary in response to the number of lighting elements, for example. For example, a sensed voltage can be indicative of a lighting brightness, and a sensed current can be indicative of a number of lighting elements.

FIG. 5is a block diagram of an embodiment of a light string power controller. InFIG. 5, constant-brightness controller74draws operating power from power source76and provides lighting power to series-connected light string(s)78. Constant-brightness controller74includes power interface80, power converter82, power detector84, light-string load detector86, and light-string interface88. Series-connected light string(s)78is electrically connected to power detector84, power converter82and light string load detector86via light string interface88. In some embodiments, light string interface88is a wired interface and series-connected light string(s)78is fixedly and electrically coupled to constant-brightness controller74. In such an embodiment, series-connected light string(s)78can have an electrical connector at a distal end configured to couple to additional light strings, for example. In other embodiments, light string interface88is an electrical connector configured to removably couple to series-connected light string(s)78.

Light-string load detector86is configured to provide a load-query signal to series-connected light string(s)78. Series-connected light string(s)78receives the load-query signal and provides a load-response signal in response to the received load-query signal. The load-response signal is indicative of a power level corresponding to an illumination value of series-connected light string(s)78. For example, if series-connected light string(s)78includes only one light string, then the load-response signal is indicative of a power level corresponding to the power that will cause each of the lighting elements of the one light string to illuminate at the illumination value indicated by the load-response signal. If, however, series-connected light string(s)78includes more than one light string, then the load-response signal will be indicative of a power level corresponding to the power that will cause each of the lighting elements of the more than one light string to illuminate at the illumination value indicated by the load-response signal.

Power detector84senses the power provided by power convertor82and provided to series-connected light string(s)78via light string interface88. Power detector84also generates a signal indicative of the sensed power level provided to series-connected light string(s)78. Power converter82then compares the signal indicative of the sensed power level with the power level indicated by the load-response signal. Power converter82controls the power provided to series-connected light string(s)78so as to be substantially equal to the power level indicated by the load-response signal. In some embodiments the power provided to series-connected light string(s)78can be within plus or minus 10% or within plus or minus 5% of the power level indicated by the load-response signal.

Power converter82receives operating power from power source76via power interface80. In some embodiments, power interface80can be a wired interface and power source76can be fixedly and electrically coupled to constant-brightness controller74. In other embodiments, power interface80can be an electrically connector configured to removeably coupled to power source76. In either of these embodiments, power source76can be an electrical power converter, such as an AC to DC converter and/or a battery source.

In some embodiments, the operating power received, via power interface80, can have a voltage operating range between a minimum operating voltage and a maximum operating voltage. Power converter82can be configured to provide power to series-connected light string(s)78at the power level indicated by the detected load-response signal while drawing operating power within the voltage operating range, wherein a ratio of the maximum operating voltage to the minimum operating voltage is greater than eight or ten. Power converter82can provide a constant power, as indicated by the detected load-response signal, independent of the voltage of the received operating power.

FIG. 6is a schematic diagram of an embodiment of a decorative light string for use with a constant-brightness decorative lighting system. InFIG. 6, decorative light string90includes first electrical connector92, second electrical connector94, first conductor96, second conductor98, plurality of lighting elements100, and load-query responder102. First electrical connector92has first and second contacts104A and104B. First electrical connector92is configured to receive power from a power source connected thereto via first and second contacts104A and104B. Second electrical connector94has first and second contacts106A and106B. Second electrical connector94is configured to provide power to other light strings connected thereto via first and second contacts106A and106B.

Conductor96is electrically coupled to and extends between first contact104A of first electrical connector92and first contact106A of second electrical connector94. Conductor98is electrically coupled to and extends between second contact104B of first electrical connector92and second contact106B of second electrical connector94. Conductors96and98conduct power received via first electrical connector92to power provided via second electrical connector98as well as delivering operating power to plurality of lighting elements100.

Individual lighting elements of plurality of lighting elements100are distributed along decorative light string90and are configured to receive operating power via first and second conductors96and98. In the depicted embodiment, plurality of lighting elements100is arranged in series-parallel fashion. Series-wired lighting elements104R,104B, and104G are wired in parallel via conductors96and98. Series-wired lighting elements104R include six red LEDs R1, R2, R3, R4, R5and R6. Series-wired lighting elements104B include four blue LEDs B1, B2, B3, and B4. Series-wired lighting elements104G include five green LEDs G1, G2, G3, G4, and G5. A voltage drop across each of red LEDs R1, R2, R3, R4, R5and R6results from a current provided to series-wired lighting elements104R. Similarly, voltage drops across each of blue LEDS B1, B2, B3, and B4result from a current provided to series-wired lighting elements104B. Voltage drops across each of green LEDS G1, G2, G3, G4, and G5result from a current provided to series-wired lighting elements104G.

An applied voltage across conductors96and98will cause currents to flow in each of series-wired lighting elements104R,104B, and104G. The number of LEDs in each of series-wired lighting elements104R,104B, and104G can be selected to cause individual lighting elements R1, R2, R3, R4, R5, R6, B1, B2, B3, B4, G1, G2, G3, G4and G5to have a desired current flowing therethrough. The current flowing through each of series-wired lighting elements104R,104B, and104G corresponds to a brightness of individual lighting elements R1, R2, R3, R4, R5, R6, B1, B2, B3, B4, G1, G2, G3, G4and G5. In some embodiments, the number of series-connected lighting elements is selected to normalize the brightness of the differently colored elements. Red LED R1, for example might require a 0.7V drop across it for a desired brightness level, while blue LED B1might require a 0.95V drop across it for the corresponding desired brightness level.

Load query responder102is connected between conductors96and98. Load query responder102can be configured to receive a load-query signal (e.g., from constant-brightness controller74depicted inFIG. 5) and to provide a load-response signal in response to the received load-query signal. The load-response signal can be indicative of a power level corresponding to an illumination value of the plurality of lighting elements. In some embodiments, load query responder102includes a capacitor. In such an embodiment, the capacitance of load query responder102can be indicative of the number of lighting elements in decorative light string90, for example.

As more light strings are connected to one another, each of which having load query responder102sized to indicate the number of lighting element therein, the total capacitance between conductors96and98increases. Constant-brightness controller74can determine the total number of lighting elements by measuring the total capacitance between conductors96and98. For example, constant-brightness controller74can generate a small-signal AC voltage on conductors96and98. The capacitance of load-query responders102then draw a small-signal AC current in response to the supplied small-signal AC voltage. Constant-brightness controller74can then detect and/or measure the AC current conducted, via conductors96and98, to determine the total load of the series-connected light strings.

In some embodiments, load-query responder102can be a resistor. In such an embodiment, a small voltage, below a level which causes the lighting elements to conduct significant current, can be applied across conductors96and98. The conducted current response can then indicate to constant-brightness controller74a power level corresponding to an illumination value of the one or more connected decorative light strings.

In some embodiments, the load-query signal is generated at a start-up time. In some embodiments, the load-query signal is generated if constant-brightness controller74detects a change in the electrical load connected thereto. In some embodiments, the constant brightness controller periodically generates the load-query signal.

FIG. 7is a circuit schematic diagram of an exemplary constant-brightness decorative lighting system. InFIG. 7, constant-brightness controller74includes input voltage converter104, and output voltage converter106. Input voltage converter104receives operating power via input pins J2and J3. The received operating power can have a voltage over a broad range. For example, in the depicted embodiment, the power source can be between 2 and 9 series connected NiMH batteries, each of which can deliver power between 1.5 volts down to 0.8 volts. Thus, the input voltage range can be between 1.6 volts up to 13.5 volts, for example. Such a voltage range has a dynamic range of greater than eight to one. In other embodiment, even higher dynamic ranges can be obtained. The received operating power is then converted by voltage regulator U2to an internal operating voltage (e.g., 2.5 volts).

Output voltage converter104converts the received power from the internal operating voltage level to a level indicated a query-response signal received by one or more connected light strings attached to pins J4and J5. In the depicted embodiment, a capacitance between pins J4and J5is measured to determine the query-response signal. The measured query-response signal is indicative of a power level corresponding to a desired brightness level for the attached one or more connected light strings. A measurement of the actual power delivered to the one or more connected light strings attached to pins J4and J5is also measured. Power controller U1then compares the actual power delivered to the one or more connected light strings with the power level corresponding to the desired brightness level indicated by the query response signal. Power controller U1then adjusts the actual power delivered to the one or more connected light strings connected via pins J4and J5so as to match the power level corresponding to the desired brightness level indicated by the query response signal.