EP3729912B1

EP3729912B1 - Illumination system including tunable light engine and method

Info

Publication number: EP3729912B1
Application number: EP18830992.6A
Authority: EP
Inventors: Yifeng QIU
Original assignee: Lumileds LLC
Current assignee: Lumileds LLC
Priority date: 2017-12-20
Filing date: 2018-12-20
Publication date: 2024-06-05
Anticipated expiration: 2038-12-20
Also published as: KR102501197B1; TWI764228B; CN111713180B; KR20200098660A; EP3729912A1; CN111713180A; JP6942257B2; CN115297587B; TW201933644A; WO2019126583A1; TW202044923A; CN115297587A; TWI704707B; JP2021507473A

Description

FIELD

The present disclosure relates to an illumination system including a light engine.

BACKGROUND

Light emitting diodes ("LEDs") are commonly used as light sources in various applications. LEDs are more energy-efficient than traditional light sources, providing much higher energy conversion efficiency than incandescent lamps and fluorescent light, for example. Furthermore, LEDs radiate less heat into illuminated regions and afford a greater breadth of control over brightness, emission color and spectrum than traditional light sources. These characteristics make LEDs an excellent choice for various lighting applications ranging from indoor illumination to automotive lighting. It is known, for example from US9603213B1 to apply time-division multiplexing to control separate LED light sources of a single light fixture in order to "mix" the light output from the LED light sources. From US2014300283A1 it is known to control the relative operating currents and absolute operating currents provided to groups of LEDs in order to adjust color temperature and brightness of the output light.

SUMMARY

The invention is set out in the appended claims. An illumination system is disclosed that provides a control signal interface configured to provide a voltage control signal via a control channel. A light engine is provided and includes a first signal generator configured to provide a first pulse-width modulated (PWM) signal based on the control signal, via a first channel, a second signal generator configured to provide a second PWM signal based on the control signal, via a second channel, and a third signal generator configured to provide a third PWM signal based on the first PWM signal and the second PWM signal, via a third channel.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings described below are for illustration purposes only. The drawings are not intended to limit the scope of the present disclosure. Like reference characters shown in the figures designate the same parts in the various embodiments.

FIG. 1 is a schematic diagram of an illumination system;
FIG. 2 is a schematic diagram of an example of a PWM signal generator;
FIG. 3 is a diagram of an example of a PWM signal that is generated by the PWM signal generator of FIG. 2;
FIG. 4 is a graph illustrating the response of the PWM generator of FIG. 2 to changes in control voltage;
FIG. 5 is a diagram of an example of an illumination system, according to the invention;
FIG. 6A is a plot illustrating the relationship between different PWM signals in the illumination system of FIG. 5;
FIG. 6B is a plot illustrating the relationship between different PWM signals in the illumination system of FIG. 5;
FIG. 7 is a plot illustrating the operation of the illumination system of FIG. 5;
FIG. 8 is a plot illustrating the operation of the illumination system of FIG. 5;
FIG. 9 is a plot illustrating the relationship between different control signals in the illumination system of FIG. 5;
FIG. 10 is a flowchart of an example of a process, according to an embodiment of the invention;
Fig. 11 is a top view of an electronics board for an integrated LED lighting system.

DETAILED DESCRIPTION

Examples of different light illumination systems and/or light emitting diode ("LED") implementations will be described more fully hereinafter with reference to the accompanying drawings. These examples are not mutually exclusive, and features found in one example may be combined with features found in one or more other examples to achieve additional implementations. Accordingly, it will be understood that the examples shown in the accompanying drawings are provided for illustrative purposes only and they are not intended to limit the disclosure in any way. Like numbers refer to like elements throughout.
It will be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms may be used to distinguish one element from another. For example, a first element may be termed a second element and a second element may be termed a first element without departing from the scope of the present invention. As used herein, the term "and/or" may include any and all combinations of one or more of the associated listed items.
It will be understood that when an element such as a layer, region, or substrate is referred to as being "on" or extending "onto" another element, it may be directly on or extend directly onto the other element or intervening elements may also be present. In contrast, when an element is referred to as being "directly on" or extending "directly onto" another element, there may be no intervening elements present. It will also be understood that when an element is referred to as being "connected" or "coupled" to another element, it may be directly connected or coupled to the other element and/or connected or coupled to the other element via one or more intervening elements. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements present between the element and the other element. It will be understood that these terms are intended to encompass different orientations of the element in addition to any orientation depicted in the figures.
Relative terms such as "below," "above," "upper,", "lower," "horizontal" or "vertical" may be used herein to describe a relationship of one element, layer, or region to another element, layer, or region as illustrated in the figures. It will be understood that these terms are intended to encompass different orientations of the device in addition to the orientation depicted in the figures.
Further, whether the LEDs, LED arrays, electrical components and/or electronic components are housed on one, two or more electronics boards may also depend on design constraints and/or application.
Semiconductor light emitting devices (LEDs) or optical power emitting devices, such as devices that emit ultraviolet (UV) or infrared (IR) optical power, are among the most efficient light sources currently available. These devices (hereinafter "LEDs"), may include light emitting diodes, resonant cavity light emitting diodes, vertical cavity laser diodes, edge emitting lasers, or the like. Due to their compact size and lower power requirements, for example, LEDs may be attractive candidates for many different applications. For example, they may be used as light sources (e.g., flash lights and camera flashes) for hand-held battery-powered devices, such as cameras and cell phones. They may also be used, for example, for automotive lighting, heads up display (HUD) lighting, horticultural lighting, street lighting, torch for video, general illumination (e.g., home, shop, office and studio lighting, theater/stage lighting and architectural lighting), augmented reality (AR) lighting, virtual reality (VR) lighting, as back lights for displays, and IR spectroscopy. A single LED may provide light that is less bright than an incandescent light source, and, therefore, multi-junction devices or arrays of LEDs (such as monolithic LED arrays, micro LED arrays, etc.) may be used for applications where more brightness is desired or required.
Tunable illumination is highly desirable in consumer and commercial lighting. A tunable illumination system is usually able to change its color and brightness independently of one another. According to aspects of the disclosure, a tunable illumination system is disclosed which splits a single channel output into three by means of current steering and/or time division and multiplexing techniques. More particularly, the tunable light system may split the input current into three pulse-width modulated (PWM) channels. The individual duty cycles of the PWM channels may be adjusted based on a control signal that is received via a control signal interface. The control signal interface may include a switch and/or other circuity that is manipulated by the user when the user wants to change the color of light that is output by the illumination system.
According to aspects of the disclosure, an illumination system is disclosed, comprising: a first signal generator configured to generate a first pulse-width modulated (PWM) signal based on a first control signal; a second signal generator configured to generate a second PWM signal based on a difference in voltage between a reference signal and the first control signal; a third signal generator configured to generate a third PWM signal based on the first PWM signal and the second PWM signal, the third PWM signal having a different duty cycle than at least one of the first PWM signal and the second PWM signal; a first light emitting diode (LED) that is powered using the first PWM signal, the first LED being configured to emit a first type of light; a second LED that is powered using the second PWM signal, the second LED having a second CCT, the second LED being configured to emit a second type of light; and a third LED that is powered using the third PWM signal, the third LED being configured to emit a third type of light.
According to aspects of the disclosure, a method is disclosed for operating an illumination system, comprising: generating a first pulse-width modulated (PWM) signal based on a first control signal; generating a second PWM signal based on a difference between a reference signal and the first control signal; generating a third PWM signal based on the first PWM signal and the second PWM signal, the third PWM signal having a different duty cycle than at least one of the first PWM signal and the second PWM signal; controlling a first light emitting diode (LED) based on the first PWM signal, the first LED being configured to output a first type of light; controlling a second LED based on the second PWM signal, the second LED being configured to output a second type of light; and controlling a third LED based on the third PWM signal, the third LED being configured to output a third type of light. FIG. 1 is a diagram of an example of an illumination system 100, according to aspects of the disclosure. The illumination system 100 includes a control signal interface 110, a light fixture 120, and a light engine 130. In operation, the illumination system 100 may receive a user input via the control signal interface 110 and change the color of light that is output by the light fixture 120 based on the input. For example, if a first user input is received, the light fixture 120 may output light having a first color. By contrast, if a second user input is received, the light fixture 120 may output light having a second color that is different from the first color. In some implementations, the user may provide input to the illumination system by turning a knob or moving a slider that is part of the control signal interface 110. Additionally or alternatively, in some implementations, the user may provide input to the illumination system by using his or her smartphone, and/or another electronic device to transmit an indication of a desired color to the control signal interface 110.
The control signal interface 110 may include any suitable type of circuit or a device that is configured to generate a voltage signal CTRL and provide the voltage signal CTRL to the light engine 130. Although in the present example the control signal interface 110 and the light engine 130 are depicted as separate devices, alternative implementations are possible in which the control signal interface 110 and the light engine 130 are integrated together in the same device. For example, in some implementations, the control signal interface 110 may include a potentiometer coupled to a knob or slider, which is operable to generate the control signal CTRL based on the position of the knob (or slider). As another example, the control signal interface may include a wireless receiver (e.g., a Bluetooth receiver, a Zigbee receiver, a WiFi receiver, etc.) which is operable to receive one or more data items from a remote device (e.g., a smartphone or a Zigbee gateway) and output the control signal CTRL based on the data items. In some implementations, the one or more data items may include a number identifying a desired correlated color temperature (CCT) to be output by the light fixture 120.
The light fixture 120 includes a first light source 122 , a second light source 124 and a third light source 126 . The first light source 122 (e.g., warm-white) may include one or more LEDs that are configured to output white light having a CCT of approximately 2700K. The second light source 124 (e.g., cool-white) may include one or more LEDs that are configured to output white light having a CCT of approximately 6500K. The third light source 126 (e.g., neutral-white) may include one or more LEDs that are configured to output white light having a CCT of approximately 4000K.
The light engine 130 is configured to supply power to the light fixture 120 over three different channels. More particularly, the light engine 130 is configured to: supply a first PWM signal PWR1 to the light source 122 (e.g., warm-white) over a first channel; supply a second PWM signal PWR2 to the light source 124 (e.g., cool-white) over a second channel; and supply a third PWM signal PWR3 to the light source 126 (e.g., neutral-white) over a third channel. The signal PWR1 is used to power the warm-white light source, and its duty cycle may determine the brightness of the warm-white light source. The signal PWR2 is used to power the cool-white light source, and its duty cycle may determine the brightness of the cool-white light source. The signal PWR3 is used to power the neutral-white light source, and its duty cycle may determine the brightness of the neutral-white light source. In operation, the tunable light engine may change the relative magnitude of the duty cycles of the signals PWR1, PWR2, and PWR3, to adjust the respective brightness of each one of light sources 122-126. As can be readily appreciated, varying the individual brightness of the light sources 122-126 may cause the output of the light fixture 120 to change color (and/or CCT). As noted above, the light output of the light fixture 120 is the combination (e.g., a mix) of the light emissions produced by the light sources 122-126.
According to aspects of the disclosure, the light engine 130 may include any suitable type of electronic device and/or electronic circuitry that is configured to generate the signals PWR1, PWR2, and PWR3. Although in the present examples, the signals PWR1-PWR3 are PWM signals, alternative implementations are possible in which the signals PWR1 are current signals, voltage signals, and/or any other suitable type of signal. Furthermore, although in the present example the light sources 122-126 are white light sources, alternative implementations are possible in which the light sources 122-126 are each configured to emit a different color of light. For example, the light source 122 may be configured to emit red light, the light source 126 may be configured to emit green light, and the light source 124 may be configured to emit blue light.
FIG. 2 is a schematic diagram of an example of a PWM generator 200, according to aspects of the disclosure. The PWM generator 200 may include any suitable type of PWM generator. In some implementations, the PWM generator 200 may include a power-in terminal 210, a ground terminal 220, control terminal 230, and an output terminal 240. In operation, the PWM generator 200 may receive power at the power-in terminal 210 and a voltage control signal VCTRL at the control terminal 230. Based on the control signal VCTRL, the PWM generator 200 may generate a PWM signal and output the PWM signal from the output terminal 240.
FIG. 3 is graph illustrating an example of a PWM signal which may be generated by the PWM generator 200. The PWM signal may have a period P and a pulse width W. The duty cycle of the PWM signal is the proportion of each period P for which the PWM signal is on (e.g., high), and it may be described by Equation 1 below: $DUTY CYCLE OF PWM SIGNAL = \frac{PULSE WIDTH W}{PERIOD P} \times 100$
FIG. 4 is a graph illustrating the response of the PWM generator 200, according to aspects of the disclosure. As illustrated, when the control signal VCTRL has a first value (e.g., approximately 0V), the duty cycle of the PWM signal that is generated by the PWM generator 200 is 100%, and when the control signal VCTRL has a second value Vc, the PWM generator 200 is deactivated. Although not shown in FIG. 4, in some implementations, the PWM generator 200 may be configured to set the duty cycle of the PWM signal at 100% when the value of the control signal VCTRL is in a predetermined range (e.g., 0V-0.4V). Configuring the PWM generator 200 in this manner may ensure that outputting a PWM signal having a 100% duty cycle is always possible, as obtaining a control signal that is exactly 0V may not always be feasible in analog circuits. According to aspects of the disclosure, when the PWM generator is deactivated, it may be regarded as producing a PWM signal having a duty cycle of 0%. According to the present disclosure, the value Vc may be referred to as the cutoff voltage of the PWM generator. The value Vc may depend on the internal design of the PWM generator 200. Depending on design specifications, any suitable value for Vc may be achieved by those of ordinary skill in the art.
FIG. 5 is a circuit diagram of an example of an illumination system 500, which uses PWM generators, such as the PWM generator 200 as one of its building blocks. As illustrated, the illumination system 500 may include a light fixture 510, a control signal interface 520, and a light engine 530.
The light fixture 510 includes a first light source 512, a second light source 514, and a third light source 516. Each light source may include one or more respective LEDs. For example, the first light source 512 may include one or more light emitting diodes (LEDs) that are configured to produce a first type of light. The second light source 514 may include one or more LEDs that are configured to produce a second type of light. The third light source 516 may include one or more LEDs that are configured to produce a third type of light. The three types of light may differ from one another in one or more of wavelength, color rendering index (CRI), correlated color temperature (CCT), and/or color. In some implementations, the first type of light may be a warm-white light, the second type of light may be a cool-white light, and the third type of light may be a neutral-white light. Additionally or alternatively, in some implementations, the first type of light may be a red light, the second type of light may be a green light, and the third type of light may be a blue light.
According to the present example, the light fixture 510 may be arranged to produce tunable white light by mixing the respective outputs of each of the light sources 512-516. In such instances, the light source 512 may be configured to emit warm-white light having CCT of approximately 2700K; the light source 514 may be configured to emit cool-white light having a CCT of approximately 6500K; and the light source 516 may be configured to emit neutral-white light having a CCT of approximately 4000 CCT. As noted above, the output of the light fixture 510 may be a composite light output that is produced as a result of the emissions from the light sources 512-516 mixing with one another. The CCT of the composite light output may be varied by changing the respective brightness of each of light sources based on a control signal VCRL1, which is generated by the control signal interface 520 and is provided via a first channel 521.
The control signal interface 520 may include any suitable type of circuit or a device that is configured to generate a voltage control signal VCTRL1 and provide the control signal VCTRL1 to the light engine 530. Although in the present example the control signal interface 520 and the light engine 530 are depicted as separate devices, alternative implementations are possible in which the control signal interface 520 and the light engine 530 are integrated together in the same device. For example, in some implementations, the control signal interface 520 may include a potentiometer coupled to a knob or slider, which is operable to generate the control signal VCTRL1 based on the position of the knob (or slider). As another example, the control signal interface may include a wireless receiver (e.g., a Bluetooth receiver, a Zigbee receiver, a WiFi receiver, etc.) which is operable to receive one or more data items from a remote device (e.g., a smartphone or a Zigbee gateway) and output the control signal VCTRL1 based on the data items. As another example, the control signal interface 520 may include an autonomous or semi-autonomous controller which is configured to generate the control signal VCTRL1 based on various control criteria. Those control criteria may include one or more of time of day, current date, current month, current season, etc.
The light engine 530 is a three-channel light engine. The light engine 530 is configured to supply power to each of the light sources 512-516 over different respective channels 522, 523, and 524. The light engine 530 includes a current source 532, a voltage regulator 534, and a reference voltage generator 536. The voltage regulator 534 is configured to generate a voltage VDD that is used for powering various components of the light engine 530, as shown. The reference voltage generator 536 is configured to generate a reference voltage signal VREF. The impact of the signal VREF on the operation of the light engine 530 is discussed further below.
The light engine 530 is operable to drive the light source 512 by using a first PWM signal PWR1 which is supplied to the light source 512 over a first channel 522. The signal PWR1 is generated by using a first signal generator GEN 1 525 and a first switch SW1. The generator GEN 1 525 may be the same or similar to the PWM generator 200 which is discussed with respect to FIG. 2, and has a cutoff voltage Vc₁. The switch SW1 is a MOSFET transistor. The light source 512 is connected to the current source 532 across the drain-source of the MOSFET transistor SW1, and the gate of the MOSFET transistor SW1 is arranged to receive a PWM signal VGATE1 which is generated by the signal generator GEN 1 525. As can be readily appreciated, this arrangement may result in the switch SW1 imparting on the signal PWR1 a duty cycle that is the same or similar to that of the signal VGATE1. The duty cycle of the signal VGATE1 is dependent on the magnitude (e.g., level) of the control signal VCTRL1, as shown in FIG. 3.
The light engine 530 is operable to drive the light source 514 by using a second PWM signal PWR2 which is supplied to the light source 514 over a second channel 523. The signal PWR2 is generated by using a second signal generator GEN 2 526 and a second switch SW2. The generator GEN 2 526 may be the same or similar to the PWM generator 200 which is discussed with respect to FIG. 2, and has a cutoff voltage Vc₂. The cutoff voltage Vc₂ of the signal generator GEN 2 526 may be the same or different from the cutoff voltage Vc₁ of the signal generator GEN 1 525. The switch SW2 is a MOSFET transistor. The light source 514 is connected to the current source 532 across the drain-source of the MOSFET transistor SW2, and the gate of the MOSFET transistor SW2 is arranged to receive a PWM signal VGATE2 which is generated by the signal generator GEN 2 526. As can be readily appreciated, this arrangement may result in the switch SW2 imparting on the signal PWR2 a duty cycle that is the same or similar to that of the signal VGATE2. The duty cycle of the signal VGATE2 is dependent on the magnitude (e.g., level) of a voltage control signal VCTRL2, as shown in FIG. 3.
The control signal VCTRL2 is a voltage signal. Furthermore, as noted above, the signals VCTRL1 and VREF also are voltage signals. In this regards, the control signal VCTRL2 may be generated by subtracting the voltage of first control signal VCTRL1 from the voltage of the reference signal VREF. For example, when the reference signal VREF is 10V and the control signal VCTRL1 is 3V, the control signal VCTRL2 may equal 7V. The control signal VCTRL2 is generated using a voltage subtracting circuit SUB1. The subtracting circuit SUB1 may include an operational amplifier (opamp) 540 configured to operate as a voltage subtractor. Furthermore, the subtracting circuit SUB1 may include resistors 552, 554, 556, and 558. Resistors 552 and 554 may both have a resistance R2. Resistors 556 and 558 may both have a resistance R1. Resistance R2 may be the same or different from resistance R1. Resistor 552 is disposed between the output terminal and the inverting input terminal of the opamp 540, as shown. Resistor 554 is coupled between the non-inverting input terminal of the opamp 540 and Ground. Resistor 556 is coupled between the inverting terminal of the opamp 540 and the control signal interface 520. Resistor 558 is coupled between the non-inverting terminal of the opamp 540 and the control reference voltage generator 536. In operation, the opamp 540 may: (i) receive the control signal VCTRL1 as a first input, (ii) receive the reference signal VREF as a second input, and generate the control signal VCTRL2 based on the control signal VCTRL1 and the reference signal VREF. The magnitude of the control signal VCTRL2 is described by Equation 2 below: $VCTRL 2 = (VREF - VCTRL 1) \frac{R 2}{R 1}$
The light engine 530 is operable to drive the light source 516 by using a third PWM signal PWR3 which is supplied to the light source 516 over a third channel 524. The signal PWR3 is generated by using a third signal generator GEN3 and a third switch SW3. The switch SW2 is a MOSFET transistor. The light source 516 is connected to the current source 532 across the drain-source of the MOSFET transistor SW3, and the gate of the MOSFET transistor SW3 is arranged to receive a PWM signal VGATE3 which is generated by the signal generator GEN3. As can be readily appreciated, this arrangement may result in the switch SW3 imparting on the signal PWR3 a duty cycle that is the same or similar to that of the signal VGATE3. The signal VGATE3 is generated by the generator GEN3 based on the signals VGATE1 and VGATE2. The signal generator GEN3 is a NOR gate. As illustrated in FIG. 5, the NOR gate receives the signals VGATE1 and VGATE2 as inputs and generates the signal VGATE3 by performing a NOR operation on the signals VGATE1 and VGATE2.
As illustrated in FIGS 6A-B, one or more of: (i) the value (e.g., level) of the voltage signal VREF, (ii) the value (e.g., level) of the cutoff voltage Vc1 of the signal generator GEN 1 525, and (iii) the value (e.g., level) of the cutoff voltage Vc2 of the signal generator GEN 2 526 may be selected such that only one of the signals VGATE1 and VGATE2 is at a logic high at any given time. This may be needed so that current from the current source 532 can be diverted to only one channel (e.g., only one of the light-sources 512-516) at any given time. In some implementations, diverting current from the current source 532 to only one channel at any given time may be advantageous as it may permit a more precise control over the brightness of the light sources 512-516.
In some implementations, as illustrated in FIGS. 6A-B, one of the signals VGATE1 and VGATE2 may always have a duty cycle of 0%, while the other may have a duty cycle that is greater than 0%. In such instances, the signal VGATE3 is generated by inverting a given one of the signals VGATE1 and VGATE2 which has the greater duty cycle. As a result, the sum of the duty cycles of the given one of the signals VGATE1 and VGATE2 which has the greater duty cycle, and the signal VGATE3 equals 100%. Stated succinctly, in the example of FIGS. 6A-B, the signal VGATE3 is the inverse of one of the signals VGATE1 and VGATE2. According to aspects of the disclosure, one PWM signal is the inverse of another PWM signal when the value of the former signal is the opposite of the latter. For instance, as shown in FIG. 6A, the signal VGATE3 may be considered to be the inverse of the signal VGATE1 because the signal VGATE3 is at a logic high at all times when the signal VGATE1 is at a logic low, and vice versa.
Stated succinctly, in some implementations, the light engine 530 may steer the current generated by the current source 532 into three pulse-width modulated channels (e.g., PWR1, PWR2, PWR3) with the sum of their duty cycles being unity. This effect may be achieved by: (i) ensuring that only one of the signals VGATE1 and VGATE2 is at a logic high value at any given time, (ii) and ensuring that the signal VGATE3 is the inverse of one of the signals VGATE1 and VGATE2 that has the greater duty cycle. Diverting the current from current source 532 in this manner may help achieve a more precise control over the brightness of the light output from the light sources 512-516.
As noted above, the operation of the light engine 530 is dependent on one or more of the magnitude of the reference signal VREF, the cutoff voltage Vc₁ of the signal generator GEN 1 525, the cutoff voltage Vc₂ of the signal generator GEN 2 526, and the ratio R2/R1. The present disclosure is not limited to any specific value for the reference signal VREF, the cutoff voltage Vc₁ of the signal generator GEN 1 525, the cutoff voltage Vc₂ of the signal generator GEN 2 526, and the ratio R2/R1. The value of any of these variables may vary in different configurations of the illumination system 500, and it may be selected in accordance with desired design specifications.
The control signal VCTRL1, as discussed above, is generated by the control signal interface 520 in response to a user input indicating a desired CCT (and/or color) for the light that is output by the light fixture 510. The control signal VCTRL1 may thus be a voltage signal indicating a desired CCT (and/or color) for the light that is emitted from the light fixture 510.
The control signal VCTRL1 may determine when the light source 512 will be switched off. More particularly, when the magnitude of the control signal VCTRL1 exceeds the cutoff voltage Vc₁ of the signal generator GEN 1 525, the light source 512 is switched off. The reference signal VREF may determine when the light source 516 will be switched on. If the value of the reference signal VREF is lower than double the cutoff voltage Vc₁ of the signal generator GEN 1 525, the light source 514 is switched on before the light source 512 is switched off. By contrast, if the value of the reference signal VREF is higher than double the cutoff voltage Vc₁ of the signal generator GEN 1 525, the light source 514 is switched on before the light source 512 is switched off. Similarly, when the signal VREF is equal to double the cutoff voltage Vc₁ of the signal generator GEN 1 525, the light source 514 is switched at the same time when the light source 512 is switched off.
The ratio R2/R1 may determine the rate at which the brightness of the light source 514 changes in response to changes in the signal VCTRL1. This, in turn, may affect the responsiveness of the illumination system 500 to user input. As noted above, in some implementations, the light source 514 may be a cool-white light source and the control signal VCRL1 may be generated by the control signal interface 520 in response to the user turning a knob. In such instances, when the ratio R2/R1 is high, the light output of the illumination system 500 will turn cool more abruptly when the knob is turned. By contrast, when the ratio R2/R1 is low, the light output of the illumination system 500 may turn cool more slowly when the knob is actuated.
FIG. 7 shows a plot 700 illustrating the operation of the illumination system 500, in accordance with one possible configuration of the light engine 530. In this configuration, the cutoff voltage Vc₁ of the signal generator GEN 1 525 is the same as the cutoff voltage Vc₂ of the signal generator GEN 2 526, and the magnitude of the reference signal VREF equals double the cutoff voltage Vc₁. The plot 700 shows the relationship between the respective duty cycle of each of the signals PWR1, PWR2, and PWR3 and the control signal VCTRL1. Furthermore, the plot 700 illustrates that the illumination system 500 may have at least five operational states, which are herein enumerated as states S0-S4.
The illumination system 500 may be in the state S0 when the control signal VCTRL1 is equal to 0V (VCTRL1=0V). When the illumination system 500 is in the state S0, the light source 512 may be switched on (at maximum capacity), and the light sources 514 and 516 may be switched off.
The illumination system 500 may be in the state S1 when the control signal VCTRL1 is greater than 0V and less than the cutoff voltage Vc₁ of the signal generator GEN 1 525 (0<VCTRL1<Vc₁). When the illumination system 500 is in the state S1, the light sources 512 and 516 may be switched on, and the light source 514 may be switched off.
The illumination system 500 may be in the state S2 when the control signal VCTRL1 is equal to the cutoff voltage Vc₁ of the signal generator GEN 1 525 (VCTRL1=Vc₁). When the illumination system 500 is in the state S2, the light source 516 may be switched on (at maximum capacity), and the light sources 512 and 514 may be switched off.
The illumination system 500 may be in the state S3 when the control signal VCTRL1 is greater than the cutoff voltage Vc₁ of the signal generator GEN 1 525 and less than the reference signal VREF (Vc₁<VCTRL1<VREF). When the illumination system 500 is in the state S3, the light sources 514 and 516 may be switched on, and the light source 512 may be switched off.
The illumination system 500 may be in the state S4 when the control signal VCTRL1 is greater than or equal to VREF (VCTRL1≥VREF). When the illumination system 500 is in the state S4, the light source 514 may be switched on (at maximum capacity), and the light sources 512 and 516 may be switched off.
FIG. 8 shows a plot 800 illustrating the operation of the illumination system 500, in accordance with another possible configuration of the light engine 530. In this configuration, the cutoff voltage Vc₁ of the signal generator GEN 1 525 is the same as the cutoff voltage Vc₂ of the signal generator GEN 2 526, and the magnitude of the reference signal VREF is greater than double the magnitude cutoff voltage Vc₁. The plot 800 shows the relationship between respective duty cycle of each of the signals PWR1, PWR2, and PWR3 and the control signal VCTRL1. Furthermore, the plot 800 illustrates that the illumination system 500 may have at least five operational states, which are herein enumerated as states S0-S4.
The illumination system 500 may be in the state S0 when the control signal VCTRL1 is equal to 0V (VCTRL1=0V). When the illumination system 500 is in the state S0, the light source 512 may be switched on (at maximum capacity), and the light sources 514 and 516 may be switched off.
The illumination system 500 may be in the state S1 when the control signal VCTRL1 is greater than 0V and less than the cutoff voltage Vc₁ of the signal generator GEN 1 525 (0<VCTRL1<Vc₁). When the illumination system 500 is in the state S1, the light sources 512 and 516 may be switched on, and the light source 514 may be switched off.
The illumination system 500 may be in the state S2 when the control signal VCTRL1 is greater than or equal to the cutoff voltage Vc₁ of the signal generator GEN 1 525 and less than or equal to Vm (Vc₁≤VCTRL1≤Vm). When the illumination system 500 is in the state S2, the light source 516 may be switched on (at maximum capacity), and the light sources 512 and 514 may be switched off. In some implementation, the value Vm may be defined by Equation 3 below: $Vm = VREF - {Vc}_{2} * (\frac{R 1}{R 2})$
The illumination system 500 may be in the state S3 when the control signal VCTRL1 is greater than Vm and less than the reference signal VREF (Vm<VCTRL1 <VREF). When the illumination system 500 is in the state S3, the light sources 514 and 516 may be switched on, and the light source 512 may be switched off. Accordingly, Vm may be the value for the control signal VCTRL1 at which the light source 514 is switched on.
The illumination system 500 may be in the state S4 when the control signal VCTRL1 is greater than or equal to the reference signal VREF (VCTRL1≥VREF). When the illumination system 500 is in the state S4, the light source 514 may be switched on (at maximum capacity), and the light sources 512 and 516 may be switched off.
FIG. 9 shows a plot 900 which illustrates the relationship between the control signals VCTRL1 and VCTRL2, in accordance with the configuration of the illumination system 500 that is discussed with respect to FIG. 8. As shown, when the control signal VCTRL1 reaches the value of the cutoff voltage Vc₁ of the signal generator GEN 1 525, the light source 512 is switched off and the light source 516 may reach 100% brightness. When the control signal VCTRL1 surpasses the value Vm, the brightness of the light source 516 may start to decrease. Furthermore, for values between of VCTRL1 between Vc₁ and Vm, the light source 516 may operate at maximum brightness and the light sources 512 and 514 are switched off.
The plots 700 and 800 illustrate that the illumination system 500 may permit the user to change the color and/or CCT of the light output produced by the illumination system 500, without affecting the total brightness of the light that is emitted from the illumination system 500. This concept is illustrated in the plots 700 and 800. As illustrated in the plots 700 and 800, the lines representing the signals PWR1 and PWR2 may have slopes that are equal in magnitude, but opposite in sign, to the slope of the line representing the signal PWR3. This implies that any decrease in brightness of one of the light source 512 and the light source 514 is matched by an equal increase in brightness of the light source 516, and vice versa. Thus, in some implementations, when the CCT (or color) of the light output of the illumination system 500 is changed (as a result of the control signal VCTRL1 changing), that change may take place without any increase or decrease in brightness of the illumination system's 500 light output.
FIG. 10 is a flowchart of an example of the process, according to aspects of the disclosure. In some implementations, all steps in the process 1000 may be performed concurrently based on the sequencing of the reference numbers provided in Fig. 10. Alternatively, in some implementations, some or all steps in the process 1000 may be performed sequentially, for example, as outlined by the flow arrows provided in Fig. 10. The process 1000 may be performed by the illumination system 100, the illumination system 500, and/or any other suitable type of electronic device. For example, in some implementations, at least some of the steps in the process 1000 may be performed using processing circuitry, such as a microprocessor (e.g., an ARM-based processor, an Arduino-based processor, etc.) Additionally or alternatively, in some implementations, at least some of the steps in the process 1000 may be performed by using an electronic circuit, such as the one shown in FIG. 5.
At step 1010, a first control signal is received which indicates a desired CCT and/or a desired color for a light output. The control signal may be received from a control signal interface, such as the control signal interface 110 or 520. In some implementations, the control signal may be a voltage signal, such as the control signal VCTRL1. In some implementations, the control signal may be a digital representation of a number or an alphanumerical string which indicates a desired CCT and/or color. At step 1020, a reference signal is generated. In some implementations, the reference signal may be a voltage signal, such as the signal VREF. Additionally or alternatively, in some implementations, the reference signal may be a digital representation of a number and/or an alphanumerical string. At step 1030, a second control signal is generated based on at least one of the reference signal and the first control signal. In some implementations, the second control signal may be generated by subtracting the first control signal from the reference signal.
At step 1040, a first PWM signal is generated based on the first control signal. In some implementations, the first PWM signal may have a duty cycle that is based on the first control signal. In some implementations, the duty cycle of the first PWM signal may be proportional to the magnitude of the first control signal (e.g., proportional to a level of the first control signal).
At step 1050, a second PWM signal is generated. In some implementations, the duty cycle of the second PWM signal may be generated based on at least one of the first control signal and the reference signal. Additionally or alternatively, in some implementations, the second control signal may be generated based on the second control signal. Additionally or alternatively, in some implementations, the second PWM signal may have a duty cycle that is proportional to the magnitude of the second control signal.
At step 1060 a third PWM signal is generated based on at least one of the first PWM signal and the second PWM signal. In some implementations, the third PWM signal may have a duty cycle that is different from each of the first PWM signal and the second PWM signal. In some implementations, the third PWM signal may be generated by inverting one of the first PWM signal and the second PWM signal which has the greater duty cycle. Additionally or alternatively, in some implementations, the third PWM signal may be generated by performing a NOR operation on the first PWM signal and the second PWM signal.
At step 1070 a first light source is controlled based on the first PWM signal. The first light source may include one or more LEDs and/or any other suitable type of light source. In some implementations, controlling the first light source may include switching on and/or switching off the first light source based on the first PWM signal. Additionally or alternatively, in some implementations, controlling the first light source may include increasing and/or decreasing the brightness of the first light source. Additionally or alternatively, in some implementations, controlling the first light source may include changing the state of a switch, which controls the flow of current across the first light source, based on the first PWM signal.
At step 1080 a second light source is controlled based on the second PWM signal. The second light source may include one or more LEDs and/or any other suitable type of light source. In some implementations, controlling the second light source may include switching on and/or switching off the second light source based on the second PWM signal. Additionally or alternatively, in some implementations, controlling the second light source may include increasing and/or decreasing the brightness of the second light source. Additionally or alternatively, in some implementations, controlling the second light source may include changing the state of a switch, which controls the flow of current across the second light source, based on the second PWM signal.
At step 1090 a third light source is controlled based on the third PWM signal. The third light source may include one or more LEDs and/or any other suitable type of light source. In some implementations, controlling the third light source may include switching on and/or switching off the third light source based on the third PWM signal. Additionally or alternatively, in some implementations, controlling the third light source may include increasing and/or decreasing the brightness of the third light source. Additionally or alternatively, in some implementations, controlling the third light source may include changing the state of a switch, which controls the flow of current across the third light source, based on the third PWM signal.
FIGS. 1-10 are provided as an example only. Although in the example of FIG. 5, the switches SW1 and SW2 are implemented as MOSFET transistors, any suitable type of switch may be used instead, such as a solid-state relay, a PMOS transistor, etc. Although in the example of FIG. 5, the subtractor SUB1 is implemented using an opamp, any suitable type of electronic circuitry may be used instead to implement the subtractor. Although in the example of FIG. 3, the generator GEN3 is implemented using a NOR gate, any other suitable type of circuitry can be used instead. For example, the signal generator GEN3 may be implemented by using an OR gate and one or more inverters, etc. At least some of the elements discussed with respect to these figures can be arranged in different order, combined, and/or altogether omitted.
Fig. 11 is a top view of an electronics board 310 for an integrated LED lighting system according to one embodiment. In alternative embodiments, two or more electronics boards may be used for the LED lighting system. For example, the LED array may be on a separate electronics board, or the sensor module may be on a separate electronics board. In the illustrated example, the electronics board 310 includes a power module 312, a sensor module 314, a connectivity and control module 316 and an LED attach region 318 reserved for attachment of an LED array to a substrate 320. The power module 312 of Fig. 11 may include the light engine (e.g., light engine 530 of Fig. 5) disclosed herein.
The substrate 320 may be any board capable of mechanically supporting, and providing electrical coupling to, electrical components, electronic components and/or electronic modules using conductive connecters, such as tracks, traces, pads, vias, and/or wires. The substrate 320 may include one or more metallization layers disposed between, or on, one or more layers of non-conductive material, such as a dielectric composite material. The power module 312 may include electrical and/or electronic elements. In an example embodiment, the power module 312 includes an AC/DC conversion circuit, a DC/DC conversion circuit, a dimming circuit, and an LED driver circuit.
The sensor module 314 may include sensors needed for an application in which the LED array is to be implemented. Example sensors may include optical sensors (e.g., IR sensors and image sensors), motion sensors, thermal sensors, mechanical sensors, proximity sensors, or even timers. By way of example, LEDs in street lighting, general illumination, and horticultural lighting applications may be turned off/on and/or adjusted based on a number of different sensor inputs, such as a detected presence of a user, detected ambient lighting conditions, detected weather conditions, or based on time of day/night. This may include, for example, adjusting the intensity of light output, the shape of light output, the color of light output, and/or turning the lights on or off to conserve energy. For AR/VR applications, motion sensors may be used to detect user movement. The motion sensors themselves may be LEDs, such as IR detector LEDs. By way of another example, for camera flash applications, image and/or other optical sensors or pixels may be used to measure lighting for a scene to be captured so that the flash lighting color, intensity illumination pattern, and/or shape may be optimally calibrated. In alternative embodiments, the electronics board 310 does not include a sensor module.
The connectivity and control module 316 may include the system microcontroller and any type of wired or wireless module configured to receive a control input from an external device. By way of example, a wireless module may include blue tooth, Zigbee, Z-wave, mesh, WiFi, near field communication (NFC) and/or peer to peer modules may be used. The microcontroller may be any type of special purpose computer or processor that may be embedded in an LED lighting system and configured or configurable to receive inputs from the wired or wireless module or other modules in the LED system (such as sensor data and data fed back from the LED module) and provide control signals to other modules based thereon. The control signal interface 110 disclosed herein may be part of the microcontroller or may receive input or provide output to the microcontroller. Algorithms implemented by the special purpose processor may be implemented in a computer program, software, or firmware incorporated in a non-transitory computer-readable storage medium for execution by the special purpose processor. Examples of non-transitory computer-readable storage mediums include a read only memory (ROM), a random access memory (RAM), a register, cache memory, and semiconductor memory devices. The memory may be included as part of the microcontroller or may be implemented elsewhere, either on or off the electronics board 310.
The term module, as used herein, may refer to electrical and/or electronic components disposed on individual circuit boards that may be soldered to one or more electronics boards 310. The term module may, however, also refer to electrical and/or electronic components that provide similar functionality, but which may be individually soldered to one or more circuit boards in a same region or in different regions.

Claims

A tunable light engine (130, 530) configured to supply power to LED light sources (512, 514, 516) over three different channels (522, 523, 524), comprising:
a current source (532);

a reference voltage generator (536) configured to generate a reference voltage signal (VREF);

a first circuit portion configured to supply power to a first light source (512) of the LED light sources (512, 514, 516) over a first

channel (522) of the three channels (522, 523, 524), comprising
- a first pulse width modulated, PWM,

signal generator (525) configured to receive a first voltage control signal (VCTRL1) at a control terminal (230) and to provide a first PWM signal (VGATE1) at an output terminal (240), and
- a first switch (SW1), wherein the gate of the first switch (SW1) is arranged to receive the first PWM signal (VGATE1), and the first light source (512) is connected to the current source (532) across the drain-source of the first switch (SW1) such that the switching of the first switch (SW1) controls the flow of current across the first light source based on the first PWM signal (VGATE1);

a second circuit portion configured to supply power to a second light source (514) of the LED light sources (512, 514, 516) over a

second channel (524) of the three channels (522, 523, 524), comprising
- a voltage subtracting circuit (SUB1) configured to generate a second voltage control signal (VCTRL2) by subtracting the first voltage control signal (VCTRL1) from the reference voltage signal (VREF);

- a second pulse width modulated, PWM,

signal generator (526) configured to receive the second voltage control signal (VCTRL2) at a control terminal (230) and to provide a second PWM signal (VGATE2) at an output terminal (240), and
- a second switch (SW2), wherein the gate of the second switch (SW2) is arranged to receive the second PWM signal (VGATE2), and the second light source (514) is connected to the current source (532) across the drain-source of the second switch (SW2), such that the switching of the second switch (SW2) controls the flow of current across the second light source based on the second PWM signal (VGATE2); and

a third circuit portion configured to supply power to a third light source (516) of the LED light sources (512, 514, 516) over a third channel (523) of the three channels (522, 523, 524), comprising
- a NOR gate (GEN3) arranged to receive the first PWM signal (VGATE1) and the second PWM signal (VGATE2) and to provide a third PWM signal (VGATE3),and

- a third switch (SW3), wherein the gate of the third switch (SW3) is arranged to receive the third PWM signal (VGATE3), and the third light source (516) is connected to the current source (532) across the drain-source of the third switch (SW3), such that the switching of the third switch (SW1) controls the flow of current across the third light source based on the third PWM signal (VGATE3);

and wherein the sum of the duty cycles of each of the first, second and third PWM signals (VGATE1, VGATE2, VGATE3) is 100%.
An illumination system (100, 500) comprising:
- a light fixture (510) comprising a first LED light source (512) configured to emit light with a first property, a second LED light source (514) configured to emit light with a second property, and a third LED light source (516) configured to emit light with a third property;

- a tunable light engine (130, 530) according to claim 1, configured to supply power to the LED light sources (512, 514, 516) over three different channels (522, 523, 524); and

- a control signal interface (110, 520) configured to provide the first voltage control signal (VCTRL1) for the tunable light engine (130, 530) via a control channel.
The illumination system according to claim 2, wherein the light emitted by the first LED light source (512), the light emitted by the second LED light source (514), and the light emitted by the third LED light source (516) differ from one another in one or more of: wavelength, color rendering index, correlated color temperature, color.
The illumination system of according to claim 2 or claim 3, wherein the first voltage control signal (VCTRL1) is provided based on a user input received at the control signal interface (110, 520).
The illumination system according to any of claims 2 to 4, wherein the first LED light source (512) is configured to emit warm-white light, the second LED light source (514) is configured to emit cool-white light, and the third LED light source (516) is configured to emit neutral-white light.
The illumination system according to any of claims 2 to 4 wherein the first LED light source (512) is configured to emit red light, the second LED light source (514) is configured to emit blue light, and the third LED light source (516) is configured to emit green light.
The illumination system according to any claims 2 to 6, wherein the first PWM signal (VGATE1) at the first output terminal (240) of the first PWM signal generator (525) has a duty cycle of 0% when the first control signal (VCTRL1) at the control terminal (230) exceeds the cutoff voltage (VC₁) of that the first PWM generator signal generator (525, 526); and wherein the second PWM signal (VGATE2) of the second PWM signal generator (526) has a duty cycle of 0% when the second control signal (VCTRL2) exceeds the cutoff voltage (V_C2) of the second PWM generator signal generator (526).
The illumination system according to the preceding claims 2-7 wherein the cutoff voltage (Vc₁) of the first PWM signal generator (525) is the same as the cutoff voltage (Vc₂) of the second PWM signal generator (526), and the magnitude of the reference signal (VREF) equals double the cutoff voltage (Vc₁ ) of the first PWM signal generator ( 525).
A method of operating the illumination system according to any of the preceding claims 2-8, the method comprising the steps of:
receiving the first voltage control signal (VCTRL1) via the control channel in response to a user input indicating a desired correlated color temperature ;

providing, via the first channel (522), the first PWM signal based on the first voltage control signal (VCTRL1);

providing, via the second channel (524), the second PWM signal based on the reference signal (VREF) and the first voltage control signal (VCTRL1);

providing, via the third channel (523), the third PWM signal based on the first PWM signal and the second PWM signal, wherein the sum of the duty cycles of each of the first, second and third PWM signals (VGATE1, VGATE2, VGATE3) is 100%;

controlling the first LED light source (512) based on the first PWM signal;

controlling the second LED light source (514) based on the second PWM signal; and

controlling the third LED (516) based on the third PWM signal.