INTENSITY CONTROL OF LEDS, CONNECTED TO A THREE-PIN SOCKET

Abstract

A “light-emitting diode (LED - Light-Emitting Diode)” illuminator (100) configured to receive signals from a first input voltage line (120A) and a second input voltage line (120B), wherein the LED illuminator (100) comprises: an LED bank (155) with one or more LEDs; a detection circuit (220) configured to detect whether the first and second input voltage lines (120A, 120B) are active and to generate first and second detection signals (225A, 225B), wherein the first detection signal (225A) indicates the first input voltage and the second detection signal (225B) indicates the second input voltage; a decoding circuit (230) comprising a resistance divider configured to receive the first and second detection signals (225A, 225B) and, in response to a short circuit of various sections of the resistance divider, generates a DC voltage signal (235) based on the first and second detection signals (225A, 225B); and an LED control device (210) configured to detect whether the first and second input voltage lines (120A, 120B) are active and to provide a regulated current to the LED bank (155), wherein the LED control device (210) is configured to: Providing a regulated output current with a first level to a first part of the LED bank (155) in response to a detection that the first input voltage line (120A) is active and the second input voltage line (120B) is not active; Providing a regulated output current with a second level to a second part of the LED bank (155) in response to a detection that the second input voltage line (120B) is active and the first input voltage line (120A) is inactive, wherein the second part of the LED bank (155) at least partially overlaps the first part; and Providing a regulated output current with a third level to a third part of the LED bank (155) in response to a detection that the first and second input voltage lines (120A, 120B) are active, wherein the third part of the LED bank (155) at least partially overlaps the first and second parts; wherein the LED control device (210) is configured to detect, whether the first and second input voltage lines (120A, 120B) are active based on the DC voltage signal (235), wherein the LED control device (210) is configured to select one of the three levels corresponding to one of three values ​​of the DC voltage signal (235), and wherein the third level is greater than the sum of the first level and the second level.

Description

BACKGROUND 1. Field of the invention

[0001] The present invention relates to controlling light-emitting diode (LED) lighting fixtures, and more particularly to controlling a light intensity of LED lighting fixtures that interface with three-way sockets or are connected to sockets with three terminals. 2. Description of the state of the art

[0002] LEDs are adopted in a wide variety of applications in electronics, for example, architectural lighting, headlights and taillights in vehicles, backlights for liquid crystal displays, flashlights, etc. Compared with traditional light sources, such as incandescent lamps and fluorescent lamps, LEDs have significant advantages, including high efficiency, good directionality, color stability, high reliability, long lifetime, small size, and environmental safety.

[0003] The use of LEDs in lighting applications is expected to increase due to their significant advantages over incandescent lamps (incandescent bulbs) in terms of power efficiency (lumens per watt) and spectral quality. Furthermore, LED lighting fixtures represent a lower environmental impact compared to fluorescent lighting systems (fluorescent ballast combined with fluorescent lamp), which can cause mercury contamination as a result of fluorescent lamp disposal.

[0004] Conventional three-way incandescent bulbs contain two filaments: a low-wattage filament and a high-wattage filament. A three-way Edison base controls the lamp's output light intensity using two AC input wires. Specifically, a low-intensity setting is created by activating only the first input wire, which is connected to the bulb's low-wattage filament. For a medium-intensity setting, the three-way base activates the second input wire, which is connected to the high-wattage filament. For a high-intensity setting, both input wires are activated.

[0005] However, when an LED lighting fixture in a three-way socket is used instead of a conventional incandescent lamp, multiple filaments are not available to provide different output light intensities. One solution to this compatibility problem uses two banks of LEDs, each connected to the output of a different single-channel LED controller or to another output of a multi-channel LED controller. The LED controller(s) takes input voltage lines from the three-way socket and supplies power to the LED banks. However, the additional wire used to connect one of the LED banks to the second input line increases the manufacturing cost of the LED lighting fixture. Furthermore, lighting the different LED banks for different intensity settings causes uneven light distribution.Light can be redistributed using complex LED layouts or a diffusion lens, but these solutions increase the complexity and manufacturing cost of the LED lighting fixture.

[0006] US 2012 / 0 235 586 A1 describes a circuit for a 3-way LED light bulb and a circuit that connects to a standard 3-way lamp socket and produces three light intensities corresponding to the three settings of the socket.

[0007] US 2013 / 0 119 887 A1 describes lighting systems and control devices for controlling light-emitting diode lamps.

[0008] WO 2014 / 172612 A2 describes LED lamps and in particular a driver circuit for a 3-way omnidirectional LED lamp.

[0009] WO 2014 / 093 044 A1 describes a switch circuit for an LED lighting unit that adapts to multi-stage light switches.

[0010] US 2012 / 0 146 538 A1 describes an LED driver with a sensing circuit and attenuation circuits that enables both triple-switched dimming and phase-control dimming to control the output power for an LED load. SUMMARY

[0011] The invention is based on the technical problem of providing an LED control for a three-way socket that is better suited to the human perception of brightness changes.

[0012] This problem is solved by the features of the independent claims. Advantageous embodiments and further developments are the subject of the dependent claims.

[0013] Embodiments described herein include a system and method for controlling an output intensity of LED lighting fixtures connected to three-way sockets. Three-way sockets include two input voltage lines for providing three levels of output light intensity. Depending on a desired output light intensity, one or both input voltage lines can be activated. An LED lighting fixture according to various embodiments detects whether one or both input voltage lines are active and adjusts a level of regulated current supplied to the LEDs based on the detection.

[0014] The invention provides an LED lighting fixture according to claim 1. The LED bank comprises one or more LEDs. The LED controller is configured to detect whether the first and second input voltage lines are active. When the first input voltage line is active and the second input voltage line is not active, the LED controller is configured to provide a regulated output current having a first level to a first portion of the LED bank. When the second input voltage line is active and the first input voltage line is not active, the LED controller is configured to provide a regulated output current having a second level to a second portion of the LED bank. When the first and second input voltage lines are active, the LED controller is configured to provide a regulated output current having a third level to a third portion of the LED bank.The second part of the LED bank at least partially overlaps the first part, and the third part at least partially overlaps the first and second parts.

[0015] By adjusting the level of current delivered to the LED bank in response to the active input voltage lines of the three-way socket, an LED lighting fixture according to embodiments described herein can be a direct replacement for a three-way incandescent lamp.

[0016] The features and advantages described in the specification are not exhaustive, and in particular, many additional features and advantages will be apparent to those skilled in the art upon consideration of the drawings, the specification, and the claims. Furthermore, it should be noted that the language used in the specification was chosen primarily for readability and instructional purposes and was not chosen to limit or restrict the subject matter of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The teachings of the embodiments will be readily understood by considering the following detailed description in conjunction with the accompanying drawings. Figure (FIG.) 1 shows an LED lighting fixture circuit according to an embodiment. Fig. 2 is a block diagram showing an LED driver according to one embodiment. Fig. 3A shows a circuit of a detection unit according to an embodiment. Fig. 3B shows an alternative circuit of a detection unit according to an embodiment. Fig. 4A shows a circuit of a decoding unit according to an embodiment. Fig. 4B shows an alternative circuit of a decoding unit according to an embodiment. DETAILED DESCRIPTION OF EMBODIMENTS

[0018] The figures (FIG.) and the following description relate to preferred embodiments in an illustrative manner. It should be noted that from the following discussion, alternative embodiments of the structures and methods disclosed herein will be readily apparent as realistic alternatives that can be used without departing from the principles of the claimed invention.

[0019] Reference will now be made in detail to various embodiments, examples of which are illustrated in the accompanying figures. It should be noted that, where possible, similar or like reference numerals may be used throughout the figures and may indicate similar or like functionality. The figures show embodiments for illustration purposes only. One skilled in the art will readily appreciate from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the invention described herein.

[0020] As explained in more detail below with reference to the figures, the LED lighting system and method according to various embodiments (1) detects whether one or both input voltage lines of a three-way socket are active (i.e., have a voltage above or below a threshold voltage), (2) generates lighting level control signals based on the input lines determined to be active, and (3) provides a corresponding output drive current to the LEDs in the LED lighting fixture based on the lighting control signals to achieve the desired light intensity of the LEDs. In various embodiments, the LED lighting fixture system provides three discrete levels of output drive current. Since LEDs are current-controlled devices, regulating their current effectively controls their brightness.Accordingly, by adjusting the output drive current to one of the levels in response to the sensed input lines, the LED lighting fixture provides three output illumination intensity levels. LED lighting fixtures according to embodiments described herein can thus serve as direct replacements for three-way incandescent lamps.

[0021] Fig. 1 shows an LED lighting system with an LED lighting fixture 100 that interfaces with a conventional three-way Edison base 110. The LED lighting fixture 100, according to various embodiments, is a direct replacement for a three-way incandescent lamp in a conventional three-way lighting system. The three-way base 110 is connected to an AC input voltage source 10 and the LED lighting fixture 100. The three-way base 110 receives an AC input voltage signal 15 and selects one or both lighting fixture input lines 120 in response to the light level control input signal 25. In other words, the three-way socket 110 controls the light intensity output by the LED lighting fixture 100 by selecting which input voltage line 120 (or both) to apply to the LED lighting fixture 100 in response to a control input signal 25.The LED lighting fixture 100 controls the light output intensity of the LED lighting fixture 100 to vary it in response to the activation of one or both input lines 120, representing behavior similar to three-way incandescent lamps. The light level control input signal 25 can be provided in various ways, for example, manually (via a knob or switch, not shown here) or via an automated lighting control system (not shown here).

[0022] As in Fig. 1, the LED lighting fixture 100 includes an LED driver 130 and an LED device 150. The LED device 150 includes an LED bank 155 having one or more LEDs. The LED driver 130 detects whether an input line 120A or 120B, or both, is active and supplies a drive current or control current 140 to the LED device 150 based on the detected input line 120. The LED driver 130 controls the LED device 150 based on the detected input line 120 to achieve the desired light intensity, as described in more detail below.

[0023] Fig. Figure 2 is a block diagram illustrating details of LED driver 130. In one embodiment, LED driver 130 includes a bridge rectifier 205, an LED controller 210, a detection circuit 220, and a decoding circuit 230. Those skilled in the art will recognize that other embodiments may have different modules than those described here, and that the functionalities may be distributed among the circuits or modules in a different manner. Additionally, the functions assigned to the various circuits or modules may be performed by multiple circuits or modules.

[0024] Rectifier 205 rectifies input AC voltage signals 120A and 120B and supplies the rectified signals Vin_A and Vin_B to LED controller 210. Detection circuit 220 receives the rectified signals Vin_A and Vin_B and detects the voltages of the signals. Based on the detected voltages, detection circuit 220 supplies detection signals 225A and 225B to decoding block 230.

[0025] The Fig. 3A and Fig. 3B are circuit diagrams illustrating exemplary configurations of the detection circuit 220. In Fig. 3A, rectified input voltages Vin_A and Vin_B are input to a single-terminal RC integrator with discharge resistors R1 and R2. The first conduction sense signal 225A represents the voltage across R1, and the second conduction sense signal 225B represents the voltage across R2. Fig. 3B shows a differential mode configuration of the detection circuit 220. In the Fig. 3A and Fig. 3B, the detection circuit 220 generates a first line detection signal 225A proportional to Vin_A and a second line detection signal 225B proportional to Vin_B. When an input voltage line has a magnitude greater than the magnitude of a threshold voltage, the input line is determined to be active. The magnitude of the threshold voltage can be selected based on the expected voltage of the input AC voltage 15 and the desired accuracy for a particular application. For example, for an expected input AC voltage 15 of 120V (e.g., for applications in North America), the line can be considered "active" if a detection signal 225 indicates that the corresponding input voltage line has a voltage above 70 volts.As another example, for an expected AC input voltage 15 of 230V (for example, for applications in Europe), the line may be considered "active" if a sense signal 225 indicates that the corresponding input voltage line has a voltage above 160V. Other threshold voltage values ​​may also be selected based on the desired application, for example, to avoid crosstalk in the vicinity of the sense circuit 220. Furthermore, other configurations for the sense circuit 220 than those shown in FIGS. Fig. 3A and Fig. 3B is also possible. For example, the detection circuit 220 may be implemented as a digital circuit in one embodiment.

[0026] Back to Fig. 2, the decoding circuit 230 receives the detection signals 225A and 225B from the detection circuit 220 and generates the control signal 235 based on the detection signals. Specifically, the decoding circuit 230 identifies whether the input voltage lines 120 are active based on the output signals of the detection circuit 220 and generates the control signal 235 for the LED controller 210 to drive the LEDs at the desired intensity level.

[0027] The Fig. 4A and Fig. 4B show exemplary circuit diagrams of the decoding circuit 230. In the Fig. 4A and Fig. 4B, the decoding circuit 230 is configured as a resistive divider in which different parts of the circuit can be shorted to ground depending on the state of switches Sw1 and Sw2. A DC bias for the decoding circuit 230 can be provided by a low-dropout regulator connected to an input voltage of the LED driver. The decoding circuit 230 can be configured to provide three values ​​for the control signal 235 corresponding to the three states of the decoding circuit 230: (1) switches Sw1 and Sw2 both open (or both closed), (2) switch Sw1 open and switch Sw2 closed, and (3) switch Sw1 closed and switch Sw2 open.

[0028] In the Fig. 4A and Fig. 4B, the detection signals 225A and 225B received from the detection circuit 220 control the switching controllers 405A and 405B. The switching controllers 405A and 405B turn corresponding switches Sw1 and Sw2 on and off in response to the values ​​of the first conduction detection signal 225A and the second conduction detection signal 225B. For example, the switching controller 405A may turn on Sw1 in response to the first conduction detection signal 225A exceeding a threshold voltage. Likewise, the switching controller 405B may turn on the switch Sw2 in response to the second conduction detection signal 225B exceeding a threshold voltage. In another embodiment, the switching control devices 405 may turn off the switches Sw1 and Sw2 in response to the first conduction detection signal 225A and the second conduction detection signal 225B, respectively, exceeding a threshold voltage.The threshold voltages can be selected based on the expected AC input voltage 15. For example, the threshold voltage can be selected such that switches Sw1 and Sw2 are turned on (or off) when sense signals 225 indicate that input voltage lines 120 are connected to AC voltage source 10.

[0029] The Fig. 4A, generates a DC voltage signal 235 whose value depends on the on or off states of switches Sw1 and Sw2. In another embodiment, as shown in Fig. As shown in Figure 4B, the decoding circuit 230 generates a pulse width modulation signal 235. The pulse width modulation (PWM) block 410 compares the voltage V1 with the DC bias and generates a PWM pulse wave by, for example, delta modulation. Other configurations for the decoding circuit 230 than those shown in Figures Fig. 4A and Fig. 4B are also possible. For example, decoding circuit 230 may be implemented as a digital circuit in one embodiment.

[0030] Back to Fig. 2, the LED controller 210 provides a constant output current 140 through the LED bank 155 based on the control signal 235 received from the decoding circuit 230. The LED controller 210 may be configured in a flyback topology, a buck topology, or other topologies known to those skilled in the art. The LED controller 210 may employ one of a number of well-known modulation techniques, such as pulse width modulation (PWM) or pulse frequency modulation (PFM), to control the output current 140 through the LED bank 155.

[0031] The LED controller 210 controls an output brightness of the LEDs of the LED bank 155 by providing a differently regulated output current to the LED bank 155 based on the control signal 235. In one embodiment, the LED controller 210 is configured to select one of three current levels corresponding to the three values ​​of the control signal 235. For example, if the LED controller 210 is configured as a flyback power converter including a transformer and a switch for controlling current through a primary winding of the transformer, the LED controller 210 can regulate a primary-side current amplitude to any of three levels based on the control signal 235. Alternatively, the LED controller 210 can regulate an output current 140 by controlling the switching frequency or duty cycle of the switch.The LED controller 210 may provide a first current level to the LED bank 155 (or a portion thereof) in response to the control signal indicating that the input voltage line 120A is active and the input voltage line 120B is inactive. A second current level may be provided to the LED bank 155 (or a portion thereof) in response to the control signal indicating that the input voltage line 120B is active and the input voltage line 120A is inactive. A third current level may be provided to the LED bank 155 (or a portion thereof) in response to the control signal indicating that both input voltage lines are active.

[0032] In one embodiment, the third current level is equivalent to a sum of the first and second current levels to mimic conventional three-way incandescent lamps, where the highest light intensity level is a sum of the two lower intensity levels. However, in other embodiments, the third current level can be arbitrarily set to other levels; for example, different levels can be set for different applications. For example, the third current level can be greater than a sum of the first and second current levels, or it can be less than a sum of the first and second current levels.

[0033] The LED lighting fixtures according to various embodiments have the advantage that the LED lighting fixture can be a direct replacement for conventional incandescent bulbs and lighting fixtures in conventional three-way sockets that activate different input voltage lines to control the light intensity from the lighting fixtures. Embodiments described herein provide three output light intensity levels without an additional wire connection to the LED bank. Furthermore, LED lighting fixtures as described herein provide a uniform light distribution without a complicated distribution of LEDs or a diffusion lens. Finally, the three light intensity levels of LED lighting fixtures as described can be arbitrarily adjusted for their intended applications.

[0034] After reading this disclosure, those skilled in the art will be able to recognize further alternative designs for an LED lighting fixture. Thus, while specific embodiments and applications have been illustrated and described, it is apparent that the invention is not limited to the precise construction and components described herein, and that various modifications, changes, and variations known to those skilled in the art may be made in the arrangement, operation, and details of the method and apparatus disclosed herein without departing from the spirit and scope of the invention.

Claims

[1] A light-emitting diode (LED) lighting fixture (100) configured to receive signals from a first input voltage line (120A) and a second input voltage line (120B), the LED lighting fixture (100) comprising: an LED bank (155) with one or more LEDs; a detection circuit (220) configured to detect whether the first and second input voltage lines (120A, 120B) are active and to generate first and second detection signals (225A, 225B), wherein the first detection signal (225A) indicates the first input voltage and the second detection signal (225B) indicates the second input voltage; a decoding circuit (230) comprising a resistive divider and configured to receive the first and second detection signals (225A, 225B) and, in response to short-circuiting different portions of the resistive divider, generate a DC voltage signal (235) based on the first and second detection signals (225A, 225B); and an LED controller (210) configured to detect whether the first and second input voltage lines (120A, 120B) are active and to provide a regulated current to the LED bank (155), the LED controller (210) configured to: Providing a regulated output current having a first level to a first portion of the LED bank (155) in response to detecting that the first input voltage line (120A) is active and the second input voltage line (120B) is not active; Providing a regulated output current having a second level to a second portion of the LED bank (155) in response to detecting that the second input voltage line (120B) is active and the first input voltage line (120A) is not active, wherein the second portion of the LED bank (155) at least partially overlaps the first portion; and Providing a regulated output current having a third level to a third portion of the LED bank (155) in response to detecting that the first and second input voltage lines (120A, 120B) are active, wherein the third portion of the LED bank (155) at least partially overlaps the first portion and the second portion; wherein the LED controller (210) is configured to detect, whether the first and second input voltage lines (120A, 120B) are active based on the DC voltage signal (235), wherein the LED controller (210) is configured to select one of the three levels corresponding to one of three values ​​of the DC voltage signal (235), and wherein the third level is greater than a sum of the first level and the second level. [2] The LED lighting fixture (100) of claim 1, wherein the DC voltage signal (235) has a first value in response to the first sense signal (225A) indicating that the first input voltage line (120A) is active and the second input voltage line (120B) is not active, a second value in response to the second sense signal (225B) indicating that the second input voltage line (120B) is active and the first input voltage line (120A) is not active, and a third value in response to the first and second sense signals (225A, 225B) indicating that the first and second input voltage lines (120A, 120B) are active. [3] A method for controlling an output light intensity of a light-emitting diode (LED) lighting fixture (100) configured to receive signals from a first input voltage line (120A) and a second input voltage line (120B), the method comprising: Detecting whether the first and second input voltage lines (120A, 120B) are active; Generating a first and a second detection signal (225A, 225B), wherein the first detection signal (225A) indicates the first input voltage and the second detection signal (225B) indicates the second input voltage; Generating a DC voltage signal (235) by means of a resistive divider, the DC voltage signal (235) being based on the first and second detection signals (225A, 225B); Providing a regulated output current having a first level to a first portion of an LED bank (155) in response to detecting that the first input voltage line (120A) is active and the second input voltage line (120B) is not active; Providing a regulated output current having a second level to a second portion of the LED bank (155) in response to detecting that the second input voltage line (120B) is active and the first input voltage line (120A) is not active, wherein the second portion of the LED bank (155) at least partially overlaps the first portion; and Providing a regulated output current having a third level to a third portion of the LED bank (155) in response to detecting that the first and second input voltage lines (120A, 120B) are active, wherein the third part of the LED bank (155) at least partially overlaps the first part and the second part; wherein detecting whether the first and second input voltage lines (120A, 120B) are active comprises detecting whether the first and second input voltage lines (120A, 120B) are active based on the DC voltage signal (235), wherein one of the three levels is selected that corresponds to one of three values ​​of the DC voltage signal (235), and wherein the third level is greater than a sum of the first level and the second level. [4] The method of claim 3, wherein the DC voltage signal (235) has a first value in response to the first sense signal (225A) indicating that the first input voltage line (120A) is active and the second input voltage line (120B) is not active, a second value in response to the second sense signal (225B) indicating that the second input voltage line (120B) is active and the first input voltage line (120A) is not active, and a third value in response to the first and second sense signals (225A, 225B) indicating that the first and second input voltage lines (120A, 120B) are active.

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