Hybrid digital and analog lighting control system

Abstract

The invention relates to a driver for driving a load. The driver comprises an output couplable to the load, a power converter for providing a regulated current to the output and a variable resistance element coupled to the output and arranged to draw a random or pseudo-random current from the power converter such that a current to the load is modulated by the random or pseudo-random current.

Description

[0001] Hybrid digital and analog lighting control system

[0002] FIELD OF THE INVENTION

[0003] The invention relates to a driver for driving a load. The invention further relates to a lighting system.

[0004] BACKGROUND OF THE INVENTION

[0005] Lighting systems can be used to create dynamic lighting that provides an immersive light scene experience. The lighting system provides the dynamic lighting by providing artificially reproducing the tonalities, patterns, rhythms and cycles of nature. The immersive light scene of nature consists of two parts. A predictable portion, and a variable stochastic portion associated with the predictable portion. The predictable portion relates to the daily precession, and wobble, of the earth around its axis, and its yearly orbit around the sun, as well as the interaction with other celestial bodies. The variable stochastic portion is associated with the interaction of the predictable and geolocation dependent portion of the sun’s light with the variable stochastics of the earth’s atmosphere, and the subsequent interaction of the resulting sun and skylight light striking the static and stochastic dynamic surfaces of the earth, such as soil and rock, and water, plants and trees, respectively.

[0006] The variability of stochastic and cascading light scene effects may be very diverse, in that it may be global and / or local, rich and / or dull, high and / or low dynamic, and / or simple and / or complex. Thus, the artificial reproduction of the geolocation dependent immersive light scene of nature may involve the synchronous operation of a plurality of different and identical, coarse and fine pixelated, multichannel lighting devices, together working as one system, and with the overall light scene at least in part being pre-programmed for each of the lighting devices in the system, such that each device uniquely contributes to the predictable and unpredictable portion of the overall light scene experience.

[0007] Sophisticated digital lighting systems may be deployed to reproduce the dynamic light scene experience of nature, such as streaming theatrical and stage lighting systems. However, such systems are expensive when it comes to e.g. office lighting. Cost effective, mainstream office lighting systems are digital, but extremely slow due to traditional use cases. Moreover, they are hallmarked by the grouped and static operation of simple identical, single pixel, lighting devices, limited bandwidth networks and protocols, simple device interfaces (DALI, 0-10V, DMX, D4I), low cost and resolution of single channel, digital LED drivers (often limited to 8 bits), and above all, lighting control programs such as Interact focusing on energy management rather than on light scene management.

[0008] It is desired to provide a lighting system that can provide both the predictable portion and the variable stochastic portion in a simple and cheap manner.

[0009] SUMMARY OF THE INVENTION

[0010] It is an objective of the invention to provide a lighting device that provides an improved lighting experience for a human observer in a cheap and simple way.

[0011] To overcome this concern, in a first aspect of the invention, a driver for driving a load is provided.

[0012] The driver comprises: an output couplable to the load; a power converter for providing a regulated current to the output; a variable resistance coupled to the output and arranged to draw a random or pseudo-random current from the power converter such that a current to the load is modulated by the random or pseudo-random current.

[0013] Providing a pseudo random or random current deviation in the current to the load may provide desired effects depending on the type of load. As an example, for a lighting load an introduction of a pseudo random or random fluctuation in the current provides an improved light scene experience since the light has light effects that resemble real light effects that correspond to light effects created by natural light. The power converter may be any power commonly used power converter, which would not require any modifications.

[0014] As another example, the load may be a fan that is driven by the regulated current. An advantage is that the tip noise frequencies of the fan are spread out over a wider frequency spectrum.

[0015] In a further example, example, the variable resistance is couplable in parallel with the load.

[0016] Providing the variable resistance in parallel to the load provides a current regulation that does not impact the current regulation of the regulated current by the power converter. In parallel with the load, the regulated current will be distributed between the load and the variable resistance. The current regulation of the power converter will not be impacted this way. In a further example, the variable resistance comprises a semiconductor switching element arranged to receive a control signal, wherein the control signal is used for controlling the semiconductor switching element to regulate the drawing of random or pseudo-random current from the power converter.

[0017] A reliable way of controlling the resistance of the variable resistance and therefore the amount of current that is modulated in the current of the load is to introduce a semiconductor switching element that is used to regulate the drawing of random or pseudorandom current from the power converter. A semiconductor switching element such as e.g., a MOSFET or a bipolar transistor can be controlled to provide a variable resistance based on a control signal. The control signal is provided to the gate of the MOSFET or base of the bipolar transistor.

[0018] In a further example, the control signal is an analog signal.

[0019] The analog signal may then be provided with the desired pseudo random or random voltage that is provided to the semiconductor switching element. The analog signal is then directly translated by the semiconductor switching element into the variable resistance that is used to vary the current to the load.

[0020] In a further example, the control signal is generated by a plurality of analog signals, which are summed and provided as a single control signal to the semiconductor switching element.

[0021] Multiple analog signals can be mixed together to form a single analog signal that is provided to the semiconductor switching element. The multiple analog signals are summed together into the single analog signal.

[0022] In a further example, the control signal is a derived by a digital control circuit.

[0023] Alternative or together with the analog signal generation, the signal to be provided to the semiconductor switching element can be generated using a digital control circuit. A digital processor can for example be used to generate a random or pseudo random signal that may be provided to the semiconductor switching element. This may for example be done using a digital to analog converter, DAC.

[0024] In a further example, the current to the load is modulated by the variable resistance element at a rate between 1 % to 5 % of a momentary amplitude of the regulated current.

[0025] To provide a modulation that is comfortable to the human eye, a modulation between 1 % and 5 % is preferred. Too much modulation can be perceived as disturbing and can end up in undesired light flicker. In a further example, the current to the load is modulated by the variable resistance element at a frequency between 0.0001 Hz and 10 Hz. More preferably between 0.01 and 3 Hz.

[0026] Modulating at a frequency that is too large may be perceived as flicker and is considered an undesired light effect. Therefore, the modulation frequency is desired to be very low. A slow transition may improve the wellbeing of the user while not directly noticing a change in light output.

[0027] In a further example, the power converter is arranged to provide pulse width modulated or amplitude modulated dimming to the regulated current.

[0028] To provide a load with a lower power e.g., for dimming a lighting load or reducing the speed of a fan, the amplitude of the current needs to be reduced. Preferably, this is done using pulse width modulation of the regulated current. Amplitude modulation may also be implemented, where the amplitude of the regulated current is varied using amplitude modulation. This allows a standard dimmable driver to be used for driving the load. The dimming of the light output can also be used for generating the predictable portion of light, which is a slow changing current that varies over a time period of e.g. a day.

[0029] In another example a lighting system is provided. The lighting system comprises the driver according to any of the preceding examples and the load.

[0030] Preferably, a lighting system is provided with the driver according to the invention and the load. The load is now provided with a regulated current from the power converter with an additional, relatively small, modulated current to provide the desired additional subtle lighting effects.

[0031] In another example, the load is a lighting load.

[0032] Preferably, the load is a lighting load. The lighting system may then preferably be a luminaire or a lamp.

[0033] In another example, the lighting load comprises a series combination of a first lighting load and a second lighting load, wherein the variable resistance is coupled in parallel with the first lighting load.

[0034] It may be desired to have multiple lighting loads, while not all lighting loads are required to have the variation in the current. It may be desired that one lighting load is used for providing the desired light modulation while another lighting load may be used to provide lighting that has no additional light effects.

[0035] In another example, the lighting load comprises at least one of an LED or a laser element. Preferably, the lighting load comprises at least one of an LED or a laser element. The use of an LED or laser element allows a lighting system to be provided with a high efficiency.

[0036] In another example, the lighting system comprises a sensor wherein a parameter of the random or pseudo-random current is determined based on a sensor signal from the sensor.

[0037] The random or pseudo-random signal can be modified by a signal provided by a sensor. The sensor may be used for sensing an ambient parameter such as presence, temperature or light intensity. This allows external effects to be taken into consideration when generating the signal for the variable resistance.

[0038] In another example, the variable resistance is a separate module comprising a connector for connecting to the output of the power converter and the load.

[0039] The variable resistance can be provided as a separate module that can be installed in parallel to the lighting load. This allows increased functionality for the lighting load in a very simple way. The driver and the module may be provided with connectors that can be connected together to provide the desired regulated current to the load.

[0040] BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Examples of the invention will now be described with reference to the accompanying drawings, in which:

[0042] Fig. 1 shows an example of a circuit diagram of a lighting system.

[0043] Fig. 2 shows another example of a circuit diagram of a lighting system.

[0044] Fig. 3 shows another example of a circuit diagram of a lighting system.

[0045] Fig. 4 shows another example of a circuit diagram of a lighting system.

[0046] Fig. 5 shows another example of a circuit diagram of a lighting system.

[0047] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0048] The invention will be described with reference to the Figures.

[0049] It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the apparatus, systems and methods, are intended for purposes of illustration only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the apparatus, systems and methods of the present invention will become better understood from the following description, appended claims, and accompanying drawings. It should also be understood that the Figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the Figures to indicate the same or similar parts.

[0050] Figure 1 shows an example of a circuit diagram of a lighting system. The lighting system has a driver that is used for driving the load LED1. The driver has a rectifier bridge Bl that is arranged to receive an AC voltage, which may be any standard mains voltage, and provide a rectified voltage. The rectified voltage is provided to a power converter 1. The driver may also have a power converter 1. The power converter 1 provides a regulated current to its output. The output is coupled to the load LED1 and the variable resistance element 3. The driver may also have the variable resistance element 3. The variable resistance element 3 is in this example coupled in parallel to the load LED1. The regulated current that is provided by the power converter 1 is therefore provided to the parallel combination of the load LED1 and the variable resistance element 3. The current will therefore be divided between the load LED1 and the variable resistance element 3. The distribution of the regulated current can be regulated by controlling the resistance of the variable resistance element 3. The variable resistance element 3 may have a semiconductor switching element QI. The semiconductor switching element QI receives a control signal at its control input. The control signal is provided to cause the semiconductor switching element QI to regulate the resistance of the variable resistance element 3. This is preferably done by operating the variable resistance element 3 in its linear operating regime where a control signal is directly translated into a resistance. This means that effectively a resistance is placed in parallel with the load LED1. This resistance determines the amount of current from the regulated that is not provided to the load LED1. The resistance of the variable resistance element 3 is therefore used to regulate the amount regulated current that is diverted from the load LED1. The variable resistance element 3 draws a current that is random or pseudorandom. Therefore, the current through the load LED1 will also show a random or pseudorandom behavior. This random or pseudo-random current behavior provides an additional subtle light effect which will be perceived by a human observer as a desired or comfortable light effect.

[0051] The variable resistance element 3 may have a controller 2 that is arranged to generate the random or pseudo-random control signal. Since no external control signal may be required for generating the random or pseudo-random control signal, the variable resistance element 3 may be a standalone module with a connector to allow the variable resistance element 3 to be connected to the output of the power converter and the load LED1. The variable resistance element 3 may also be integrated into the load LED1 e.g., mounted on an LED board.

[0052] Figure 2 shows another example of a circuit diagram of a lighting system. The lighting system has a driver that is used for driving the load LED1, LED2. In this example, the load LED1, LED2 comprises a series combination of a first lighting load LED1 and a second LED lighting load LED2. The driver has a rectifier bridge Bl that is arranged to receive an AC voltage, which may be any standard mains voltage, and provide a rectified voltage. The rectified voltage is provided to a power converter 1. The driver may also have a power converter 1. The power converter 1 provides a regulated current to its output. The output is coupled to the load LED1, LED2 and the variable resistance element 3. The driver may also have the variable resistance element 3. The variable resistance element 3 is in this example coupled in parallel to a part of the load LED1, LED2. It may be desired that not the entire load is provided with a random or pseudo-random current. As an example, the first lighting load LED1 may be used for providing a subtle lighting effect, while the second lighting load LED2 may be used for e.g. providing a large amount of light for lighting a large surface. Therefore, the variable resistance element 3 is placed in parallel with the first lighting load LED1. The variable resistance element 3 will therefore cause a random or pseudo-random current in the first lighting load LED1. The current through the second lighting load LED 2 is unaffected and may therefore be equal to the regulated current provided by the power converter 1. The variable resistance element 3 may be identical to the variable resistance element 3 as shown in Figure 1.

[0053] Figure 3 shows another example of a circuit diagram of a lighting system. The lighting system has a driver that is used for driving the load LED1, LED2. In this example, the load LED1, LED2 comprises a series combination of a first lighting load LED1 and a second LED lighting load LED2. The driver has a rectifier bridge Bl that is arranged to receive an AC voltage, which may be any standard mains voltage, and provide a rectified voltage. The rectified voltage is provided to a power converter 1. The driver may also have a power converter 1. The power converter 1 provides a regulated current to its output. The output is coupled to the load LED1, LED2 and the variable resistance element 3. The driver may also have the variable resistance element 3. The variable resistance element 3 is in this example coupled in parallel to a part of the load LED1, LED2. It may be desired that not the entire load is provided with a random or pseudo-random current. As an example, the first lighting load LED1 may be used for providing a subtle lighting effect, while the second lighting load LED2 may be used for e.g. providing a large amount of light for lighting a large surface. Therefore, the variable resistance element 3 is placed in parallel with the first lighting load LED1. The variable resistance element 3 will therefore cause a random or pseudo-random current in the first lighting load LED1. The current through the second lighting load LED 2 is unaffected and may therefore be equal to the regulated current provided by the power converter 1. The variable resistance element 3 may be identical to the variable resistance element 3 as shown in Figure 1. In this example, the second lighting load LED2 may be omitted. The variable resistance element 3 may be provided by multiple analog signals. In this example, three analog signals are provided to the control input of the variable resistance element 3. It is clear that any plurality of analog signals can be provided to the control input. The analog signals 1st, 2ndand 3rdare summed together with a summing circuit, which has in this example resistors Rl, R2 and R3. In this example, three separately generated waveforms can be provided to the control input of the variable resistance element 3, allowing more controllability of the random or pseudo-random signal to be provided to the control input.

[0054] Figure 4 shows another example of a circuit diagram of a lighting system. The lighting system has a driver that is used for driving the load LED1, LED2. In this example, the load LED1, LED2 comprises a series combination of a first lighting load LED1 and a second LED lighting load LED2. The driver has a rectifier bridge Bl that is arranged to receive an AC voltage, which may be any standard mains voltage, and provide a rectified voltage. The rectified voltage is provided to a power converter 1. The driver may also have a power converter 1. The power converter 1 provides a regulated current to its output. The output is coupled to the load LED1, LED2 and the variable resistance element 3. The driver may also have the variable resistance element 3. The variable resistance element 3 is in this example coupled in parallel to a part of the load LED1, LED2. It may be desired that not the entire load is provided with a random or pseudo-random current. As an example, the first lighting load LED1 may be used for providing a subtle lighting effect, while the second lighting load LED2 may be used for e.g. providing a large amount of light for lighting a large surface. Therefore, the variable resistance element 3 is placed in parallel with the first lighting load LED1. The variable resistance element 3 will therefore cause a random or pseudo-random current in the first lighting load LED1. The current through the second lighting load LED 2 is unaffected and may therefore be equal to the regulated current provided by the power converter 1. The variable resistance element 3 may be identical to the variable resistance element 3 as shown in Figure 1. In this example, the second lighting load LED2 may be omitted. In this example, the variable resistance element 3 has two semiconductor switching elements placed in parallel. Both semiconductor switching elements are placed in parallel with the first lighting load LED1. The first semiconductor switching element QI may receive a first analog signal 1stand the second semiconductor switching element Q2 may receive a second analogue signal 2nd. This allows additional semiconductor switching elements to draw multiple random or pseudo-random currents and therefore, the randomness of the current through the first lighting load LED1 is improved.

[0055] Figure 5 shows another example of a circuit diagram of a lighting system. The lighting system has a driver that is used for driving the load LED1, LED2. In this example, the load LED1, LED2 comprises a series combination of a first lighting load LED1 and a second LED lighting load LED2. The driver has a rectifier bridge Bl that is arranged to receive an AC voltage, which may be any standard mains voltage, and provide a rectified voltage. The rectified voltage is provided to a power converter 1. The driver may also have a power converter 1. The power converter 1 provides a regulated current to its output. The output is coupled to the load LED1, LED2 and the variable resistance element 3. The driver may also have a variable resistance element 3 that has a first variable resistance element and a second variable resistance element 3. It may be desired that not the entire load is provided with a single random or pseudo-random current. As an example, the first lighting load LED1 may be used for providing a first subtle lighting effect, while the second lighting load LED2 may be used for providing a second subtle lighting effect. Therefore, the first variable resistance element 3 is placed in parallel with the first lighting load LED1 and the second variable resistance element is coupled in parallel with the second lighting load LED2. The variable resistance element 3 will therefore cause a first random or pseudo-random current in the first lighting load LED1 and a second random or pseudo-random current in the second lighting load LED2. The light outputs of the first light source and the second light source will there deviate from each other. The first variable resistance element and the second variable resistance element may be controlled identical to any of the variable resistance elements 3 as shown in any of the previous Figures.

[0056] A random current can be drawn by providing a random control signal to the variable resistance element 3. An example of random can be understood as that when using multiple drivers with similar components, the currents drawn by each respective variable resistance element 3 are not the same. In a very simple way, the random behavior can be the cause of the tolerances of the components in the drivers. It is an insight of the inventor that instead of trying to keep the variations between drivers as small as possible, which is often the case, the variations have to be maintained and it would not be desired to try to compensate for the differences. Therefore, each driver will have its unique behavior.

[0057] A pseudo-random current can be drawn by providing a pseudo-random control signal to the variable resistance element 3. This means that a random signal can be modified with an additional signal. This signal may e.g. be provided by a sensor or another control or sensing element.

[0058] In the examples provided, the semiconductor switching elements QI and Q2 are shown as bipolar transistors. The base of the bipolar transistor may then be considered as the control input. The semiconductor switching elements may for example be MOSFETs, which have a gate as a control input.

[0059] In the examples provided, the loads LED1 and LED2 are shown as LED loads. Other examples of loads can be conceived such as a mechanical fan, which would be placed at the location of the LEDs.

[0060] In the examples provided, the power converter 1 may be controlled by a conventional communication protocol. Examples of such protocols are DALI, DMX or wireless communication protocols such as ZigBee, Wi-Fi or Bluetooth.

[0061] Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

Claims

CLAIMS:

1. A driver for driving a load, the driver comprising: an output couplable to the load (LED1, LED2); a power converter (1) for providing a regulated current to the output; a variable resistance element (3) coupled to the output and arranged to draw a random or pseudo-random current from the power converter (1) such that a current to the load (LED1, LED2) is modulated by the random or pseudo-random current, wherein the current to the load (LED1, LED2) is modulated by the variable resistance element (3) at a rate between 1 % to 5 % of a momentary amplitude of the regulated current or wherein the current to the load (LED1, LED2) is modulated by the variable resistance element (3) at a frequency between 0.0001 Hz and 10 Hz.

2. The driver according to claim 1, wherein the variable resistance element (3) is couplable in parallel with the load (LED1, LED2).

3. The driver according to any of the preceding claims, wherein the variable resistance element (3) comprises a semiconductor switching element (QI) arranged to receive a control signal, wherein the control signal is used for controlling the semiconductor switching element (QI) to regulate the drawing of random or pseudo-random current from the power converter (1).

4. The driver according to claim 3, wherein the control signal is an analog signal.

5. The driver according to claim 4, wherein the control signal is generated by a plurality of analog signals, which are summed and provided as a single control signal to the semiconductor switching element (QI).

6. The driver according to claim 3, wherein the control signal is derived by a digital control circuit.

7. The driver according to any of the preceding claims, wherein the power converter (1) is arranged to provide pulse width modulated or amplitude modulated dimming to the regulated current.

8. A lighting system comprising the driver according to any of the preceding claims and the load (LED1, LED2).

9. The lighting system according to claim 8, wherein the load (LED1, LED2) is a lighting load.

10. The lighting system according to claim 9, wherein the lighting load comprises a series combination of a first lighting load (LED) and a second lighting load (LED2), wherein the variable resistance element (3) is coupled in parallel with the first lighting load (LED1).

11. The lighting system according to any of the claims 9 or 10, wherein the lighting load comprises at least one of an LED or a laser element.

12. The lighting system according to any of the claims 8 to 11, further comprising a sensor wherein a parameter of the random or pseudo-random current is determined based on a sensor signal from the sensor.

13. The lighting system according to any of the claims 8 to 12, wherein the variable resistance element (3) is a separate module comprising a connector for connecting to the output of the power converter (1) and the load (LED1, LED2).

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