Efficiency optimization through parallel string switching via dimming interface

Abstract

The present invention relates to a driver circuit for driving a plurality of light sources. The driver circuit includes a driver adapted to provide a first current to a first light source and a second current to a second light source, and a controller for controlling the driver. The controller is configured to receive a dimming signal indicating a dimming level for the light output of the light sources. The controller is configured to convert the received dimming signal into a plurality of discrete dimming levels representing dimming levels. The discrete dimming levels correspond to the amount of current to be supplied by the driver to the first light source and / or the second light source. At the first discrete dimming level, the controller is configured to allow the first current to be supplied to the first light source and to prevent the second current from being supplied to the second light source. At the second discrete dimming level, the controller is configured to allow the first current to be supplied to the first light source and to allow the second current to be supplied to the second light source.

Description

Technical Field

[0001] The present invention relates to a driver circuit. The present invention further relates to a lighting device.

Background Art

[0002] For the lighting industry, the requirements for energy efficiency have become more stringent, especially with the new EU energy labelling introduced on September 1, 2021. This new labelling is in line with the trend of improving the energy efficiency of lighting products. Until then, more and more light sources had achieved an A+ or A++ label rating, making it impossible for customers to recognize the difference in luminous efficiency between products. With the new labelling, light sources have become more dispersed across the labelling range again. This also means that, for example, a lamp that had an A++ rating under the old system is now labelled as C. Therefore, it is desirable to further improve the energy efficiency of light sources.

[0003] Especially in the case of dimmable light sources, there is a strong desire to improve efficiency. In dimming, especially deep dimming, fixed losses in the driver, such as losses occurring in the control circuit, become a major part of the losses in the lighting device. Drivers are generally designed for rated power, and therefore the fixed losses also depend on the rated power of the driver. Generally, a driver with a low rated output power also has low fixed power losses. This clearly affects the total amount of electrical energy that can be provided to the load. A driver with a high rated power can provide more power to its output, but this is accompanied by more fixed losses. Therefore, it is desirable to provide a lighting device that can operate with very high efficiency while providing a good dimming function.

Summary of the Invention

Problems to be Solved by the Invention

[0004] The objective of the present invention is to provide a solution that enables dimming while maintaining good overall efficiency. [Means for solving the problem]

[0005] To provide such a solution, a first aspect of the present invention provides a driver circuit for driving a plurality of light sources. The driver circuit is - A driver adapted to supply a first current to a first light source and a second current to a second light source, - A controller for controlling the driver, Includes, The controller is configured to receive dimming signals that indicate the dimming level for the light output of the light source. The controller is configured to convert the received dimming signal into a discrete number of dimming levels, where each discrete dimming level corresponds to the amount of current to be supplied by the driver to the first and / or second light source. - At a first discrete dimming level, the controller is configured to allow a first current to be supplied to the first light source and to prevent a second current from being supplied to the second light source. - At a second discrete dimming level, the controller is configured to allow a first current to be supplied to the first light source and a second current to be supplied to the second light source.

[0006] A driver is provided that can supply regulated current to multiple light sources. The first and second light sources are capable of receiving current from the driver. A controller is provided that receives dimming signals and provides discrete dimming levels. Examples of dimming signals include phase-cut dimming signals, 0-10V dimming signals, DALI dimming signals, DMX dimming signals, or wireless dimming signals. The controller converts the received dimming signals into a number of discrete dimming levels. The discrete dimming levels are used to determine the amount of current to be supplied to the first and / or second light sources.

[0007] The absolute maximum efficiency of an LED is achieved at a specific current density; that is, efficiency decreases above and below this current density. The inventors' insight is that, in order to have maximum efficiency across the dimming range, the LED's current density needs to be optimized across the entire dimming range. This invention provides an optimal current density by turning off the LED at low dimming levels. Discrete dimming levels are introduced to provide the off-event. These discrete dimming levels may be used to provide levels at which the active light source may be changed.

[0008] The first discrete dimming level may be a low dimming level. This dimming level requires a low amount of light output. The controller may be used to allow the driver to supply a first current to the first light source and to prevent a second current from being supplied to the second light source. The driver does not need to supply an additional second current and maintains only the first current through the first light source. The total current supplied by the driver decreases, and the total amount of light remaining active also decreases. The current density in the first light source is not affected by the disconnection of the second light source or the removal of the second current. Therefore, the driver supplies a low current to the light source, effectively reducing the light output of the light source, while maintaining a high current density in the active light source.

[0009] The second discrete dimming level may be a high dimming level. This dimming level requires a high amount of light output. A controller may be used to allow the driver to supply a first current to the first light source and a second current to the second light source. The driver supplies the first and second currents. Therefore, the total current supplied by the driver increases, and the total amount of light from the light source also increases. The current density in the first light source is not affected by the introduction of the second light source and the second current. The increase in current allows the light source to supply more light while maintaining good efficiency.

[0010] Preferably, the driver can provide only a steady current corresponding to the current level set by the discrete dimming level. In this way, the current density in the first and / or second light source can remain constant and at a level that allows the light source to emit light efficiently.

[0011] In a further example, at a third discrete dimming level, the controller is configured to prevent a first current from being supplied to a first light source and to supply a second current to a second light source.

[0012] A separate discrete dimming level may be provided in which the driver provides a second current to the second light source but no current to the first light source. This allows the controller to decide, based on the provided dimming level, whether to power only the first light source, only the second light source, or both the first and second light sources. As will be discussed later, there may be many advantages to powering only the first light source or only the second light source.

[0013] In a further example, between two discrete dimming steps, the driver is configured to provide a variable current to only one of the first or second light sources based on the dimming signal, while maintaining a constant current through the other of the first or second light sources.

[0014] Between two discrete dimming levels, it is preferable that the driver may provide a variable current to only one light source. This may mean, for example, that the driver provides a fixed current to the first light source, preferably at the first light source's optimal current density. Preferably, the driver may additionally provide a current to the second light source that can vary based on the dimming signal. By providing a fixed current to the first light source, preferably at the first light source's optimal current density, the first light source operates at maximum efficiency. The second driver may operate at lower efficiency. However, the overall efficiency is still improved, and the variable current in the second light source allows for more dimming levels. Between the two discrete dimming levels, the controller may provide an additional dimming level that allows the driver providing variable power to the light sources to change the output power according to the dimming signal.

[0015] A further example is a lighting device. The lighting device is - Driver circuit and, - The first light source, - A second light source, Includes.

[0016] Lighting devices benefit most from this invention because the overall efficiency of the lighting device is improved, primarily by providing the light source with an electric current that enables more efficient light emission.

[0017] Preferably, the light source is a semiconductor light source. Examples of semiconductor light sources are LEDs, laser diodes, and vertical-cavity surface-emitting lasers (VCSELs). Preferably, the LED is formed as a filament.

[0018] In a further example, the first and second light sources are connected in a parallel configuration.

[0019] Preferably, the first and second light sources are coupled in parallel. This allows the driver to easily control and distribute current between the first and second light sources.

[0020] In a further example, the driver circuit includes a first switch connected in series with a second light source, and the controller is configured to open and close the first switch so that a first current flows through the first light source when the first switch is open, and a second current flows through the second light source when the first switch is closed.

[0021] As a very simple way to adjust the currents through the first and second light sources, a first switch is connected in series with the second light source. When the first switch is open, the current path through the second light source is blocked, and therefore, current can flow only through the first light source. Thus, opening the first switch can be used to allow the driver to supply the first current to the first light source and to prevent the second current from being supplied to the second light source at the first discrete dimming level. When the first switch is closed, the second current can flow through the second light source. Furthermore, the first current can still flow through the first light source. Thus, closing the first switch can be used to allow the driver to supply the first current to the first light source and the second current to the second light source at the second discrete dimming level. In this example, it is preferable that the first and second light sources have substantially the same forward voltage.

[0022] In a further example, the driver circuit includes a first switch connected in series with a first light source and a second switch connected in series with a second light source, and the controller is configured to open and close the first and second switches so that a first current flows through the first light source when the first switch is closed and a second current flows through the second light source when the second switch is closed.

[0023] In this example, both light sources are coupled in series with their respective switches. By closing each switch, each light source becomes active. When the first switch is closed, a first current flows through the first light source. When the second switch is closed, a second current flows through the second light source. When both switches are closed, depending on the configuration of the light sources, the first current may flow through the first light source and the second current may flow through the second light source. When both switches are open, no current can flow through either light source. If the driver provides current, this can pose a risk. An additional switch may be provided to shunt all light sources. Thereby, the current from the driver has a current path that does not pass through the light sources. Alternatively, when both switches are open, the driver can be configured not to generate current. In any case, it is preferable that one of the two switches is closed so as to ensure the current path of the driver.

[0024] In a further example, the driver circuit includes a series combination of a first switch and a second switch between the outputs of the driver, the first light source is coupled in parallel with the first switch, and the second light source is coupled in parallel with the second switch.

[0025] Instead of the parallel configuration, the light sources can also be coupled in series. A first shunt switch is provided between the two ends of the first light source, and a second shunt switch is provided between the two ends of the second light source.

[0026] When the first shunt switch is open and the second shunt switch is closed, the driver provides a first current to the first light source. No current is provided to the second light source. Therefore, the opening of the first switch and the closing of the second switch can be used to allow the driver to provide a first current to the first light source and prevent a second current from being provided to the second light source at a first discrete dimming level.

[0027] When the first shunt switch is closed and the second shunt switch is open, the driver supplies a second current to the second light source. No current is supplied to the first light source. Therefore, closing the first switch and opening the second switch can be used at a third discrete dimming level to prevent the driver from supplying a first current to the first light source and to supply a second current to the second light source.

[0028] When the first and second shunt switches are open, the driver supplies a first current to the first light source and a second current to the second light source. Opening the first and second switches can be used to allow the driver to supply a first current to the first light source and a second current to the second light source at a second discrete dimming level. The first current may be identical to the second current. In this configuration, the driver's current path is always guaranteed. If the first and second light sources have the same optimal current density, the controller may adjust the amplitudes of the first and second currents to allow the current density in the light sources to reach the optimal current density. This allows the light sources to generate light with high efficiency.

[0029] In a further example, the controller is configured to sense the current supplied by the driver, and to control a first switch and / or a second switch based on the amplitude of the current supplied by the driver.

[0030] A controller may be used to control the driver. The discrete dimming levels may be converted into currents. The controller may sense the current supplied by the driver. The amplitude of the current may be considered an indication of at what discrete dimming level the light source should operate. If the sensed current is, for example, high, the controller may allow a first current to flow through the first light source and a second current to flow through the second light source. If the sensed current is, for example, relatively low, the controller may allow only the first current to flow through the first light source and prevent the second current from flowing through the second light source. In this situation, it may be considered that the driver does not supply enough current to support the second current, and therefore only the first current is supplied.

[0031] In a further example, the forward voltage of the first light source is less than the forward voltage of the second light source.

[0032] The forward voltage of the first light source may differ from the forward voltage of the second light source. This may be because different types of light sources are used, such as different LED types. Preferably, regardless of the switch configuration, the forward voltage of the first light source is smaller than the forward voltage of the second light source so that only one of the light sources is active at the first discrete dimming level.

[0033] In a further example, at a first discrete dimming level, the driver is configured to supply a first current to the first light source such that the current density through the first light source enables the first light source to emit light close to its maximum efficiency.

[0034] Preferably, the current to the first light source is such that the first light source operates at its optimal current density. During the first discrete dimming level, the first light source operates at its optimal efficiency, and therefore, the light generated during dimming is generated efficiently.

[0035] In a further example, at the second discrete dimming level, the driver, - Provides a first current to the first light source such that the current density through the first light source enables the first light source to emit light close to its maximum efficiency, and - Provide a second current to the second light source such that the current density through the second light source enables the second light source to emit light close to its maximum efficiency. It is configured in this way.

[0036] Preferably, the current to the first light source is such that the first light source operates at its optimal current density, and the current to the second light source is such that the second light source operates at its optimal current density. During the second discrete dimming level, the first and second light sources operate at their optimal efficiency, and therefore, the light generated during this dimming level, which may be at full power, is generated efficiently.

[0037] In a further example, the first light source produces a color or color temperature different from that of the second light source.

[0038] Preferably, the first and second light sources produce different colors. For example, the first light source may produce warm white light and the second light source may produce cold white light, or vice versa. Alternatively, the light sources may produce light having different colors. For example, the light sources may emit red, green, or blue light. This allows the color output of the light sources to change based on discrete dimming levels.

[0039] In a further example, the lighting device may also include at least three light sources in a parallel configuration, and the number of dimming levels may be based on the number of light sources.

[0040] Preferably, more discrete dimming levels may be required to allow for the introduction of more dimming steps across the entire dimming range. This can be done by introducing additional light sources that can be controlled by a controller to receive currents, each of which can be supplied by a controller. These currents can be supplied at different discrete dimming levels, for example, a fourth discrete dimming level. Different combinations of active light sources at different discrete dimming levels allow the light output of the lighting device to vary across the entire dimming range. Preferably, the discrete dimming levels are set to represent an imitation of the dimming of conventional incandescent bulbs. This means that when the current to the light source is reduced, a light source that produces relatively cool white light is deactivated so that the overall color temperature becomes warmer by reducing the current to the light source.

[0041] In a further example, light generated by the first light source is emitted onto the first surface, light generated by the second light source is emitted onto the second surface, and the first surface does not overlap with the second surface, at least partially.

[0042] In addition to or as an alternative to changing the light intensity, color, or color temperature of the light source, a beam shaping mechanism can be introduced. If the first light source emits light onto a surface different from the surface from which the second light source emits light, discrete dimming levels can be used to illuminate the different surface. The overall beam angle of the illumination device can be adjusted based on the discrete dimming levels. [Brief explanation of the drawing]

[0043] Hereinafter, examples of the present invention will be described with reference to the accompanying drawings. [Figure 1] An example of a circuit diagram for a lighting device is shown. [Figure 2] Here is another example of a circuit diagram for a lighting device. [Figure 3] An example of a graph showing the relationship between light source current and dimming level is shown. [Figure 4] Here is another example of a circuit diagram for a lighting device. [Figure 5] This shows an example of a lighting device implementation. [Modes for carrying out the invention]

[0044] The present invention will be described with reference to the figures.

[0045] The detailed descriptions and specific examples illustrate exemplary embodiments of the apparatus, systems, and methods, but should be understood to be for illustrative purposes only and not intended to limit the scope of the invention. These and other features, aspects, and advantages of the apparatus, systems, and methods of the invention will be better understood from the following description, the appended claims, and the appended drawings. Please understand that the drawings are for illustrative purposes only and are not drawn to scale. Please also understand that the same reference numerals are used to indicate the same or similar parts throughout the drawings.

[0046] Figure 1 shows an example of a circuit diagram of a lighting device. The lighting device has a driver circuit. The driver circuit has a driver 1 configured to supply power to a first light source LED1 and a second light source LED2. A first switch M1 is coupled in series with the second light source LED2. The series configuration of the first light source LED1 and the second light source LED2 and the first switch M1 is coupled in parallel to the output of the driver 1. The series configuration of the first light source LED1 and the second light source LED2 and the first switch M1 may be coupled in parallel with each other. A controller 2 is provided to control the first switch M1. Preferably, the controller 2 may also be used to control the driver 1. This allows one controller 2 to control both the first switch M1 and the driver 1. Alternatively, the controller 2 may include multiple components for different purposes, for example, controlling the first switch M1 separately from the driver 1. The controller 2 may be an integral part of the driver. The driver 1 may be configured to receive the mains voltage Mains. The mains voltage is an AC voltage and therefore may be rectified by a rectifier circuit. The rectifier circuit may be part of the driver. Controller 2 may receive dimming signals from an external device configured to provide dimming signals. Examples of dimming signals are phase-cut dimming signals, 0-10V dimming signals, DALI dimming signals, DMX dimming signals, or wireless dimming signals. Controller 2 receives the dimming signal and converts this dimming signal to discrete dimming levels. This means that Controller 2 translates the dimming signal into multiple dimming steps. Preferably, if the first light source LED1 and the second light source LED2 provide similar light outputs, the number of dimming steps is based on the number of light sources provided. In the provided example, two light sources are provided. At least three discrete dimming steps are available. One discrete dimming step may be set to 0% output power, another discrete dimming step may be set to 33% output power, another discrete dimming step may be set to 66% output power, and another discrete dimming step may be set to 100% output power.In this case, driver 1 may be configured not to generate current so that the light source is not powered during the dimming step at 0% output power.

[0047] At the first discrete dimming level, driver 1 may provide a current with an amplitude corresponding to the first current. Controller 2 may open the first switch M1 and allow the first current to flow to the first light source LED1. In this situation, no current flows to the second light source LED2. At the first discrete dimming level, the driver circuit provides the first current to the first light source LED1 and no current to the second light source LED2.

[0048] At the second discrete dimming level, the driver may provide a current with an amplitude corresponding to the sum of the first and second currents. The controller 2 may close the first switch M1, which allows the second current to flow through the second light source LED2. Preferably, the forward voltage of the first light source LED1 is approximately the same as the forward voltage of the second light source LED2. In this situation, closing the first switch M1 allows the first current to flow through the first light source LED1 and the second current to flow through the second light source LED2.

[0049] Driver 1 may be configured to adjust a first current to correspond to a current density in the first light source LED1 that enables the first light source LED1 to emit light with very high efficiency, preferably so as to maximize the efficiency of the first light source LED1. Preferably, the first current has an amplitude that provides a current density in the first light source so that the first light source generates light with a predetermined efficiency. Preferably, the first current allows the first light source to operate at or near its maximum efficiency. Driver 1 may also be configured to adjust a second current to correspond to a current density in the second light source LED2 that enables the second light source LED2 to emit light with very high efficiency, preferably so as to maximize its efficiency. Preferably, the second current has an amplitude that provides a current density in the second light source so that the second light source generates light with a predetermined efficiency. Preferably, the second current allows the second light source to operate at or near its maximum efficiency. In an example where the first light source LED1 has approximately the same power requirement as the second light source LED2, the first current and the second current may have the same amplitude. In this case, the driver 1 may be configured to provide only two current levels, namely the first current or the sum of the first and second currents.

[0050] Figure 2 shows another example of a circuit diagram for a lighting device. The lighting device has a driver circuit. The driver circuit has a driver 1 configured to supply power to a first light source LED1 and a second light source LED2. A first switch M1 is coupled in series with the first light source LED1. A second switch M2 is coupled in series with the second light source LED2. The series configuration of the first light source LED1 and the first switch M1 and the series configuration of the second light source LED2 and the second switch M2 are coupled in parallel to the output of the driver 1. The series configuration of the first light source LED1 and the first switch M1 and the series configuration of the second light source LED2 and the second switch M2 may be coupled in parallel to each other. A controller 2 is provided to control the first switch M1 and the second switch M2. Preferably, the controller 2 may also be used to control the driver 1. This allows one controller 2 to control both the first switch M1 and the driver 1. Alternatively, controller 2 may include multiple components for different purposes, for example, controlling a first switch M1 separately from driver 1. Controller 2 may be an integral part of the driver. Driver 1 may be configured to receive a mains voltage Mains. The mains voltage Mains is an AC voltage and therefore may be rectified by a rectifier circuit. The rectifier circuit may be part of the driver. Controller 2 may receive a dimming signal from an external device configured to provide a dimming signal. Examples of dimming signals are phase-cut dimming signals, 0-10V dimming signals, DALI dimming signals, DMX dimming signals, or wireless dimming signals. Controller 2 receives the dimming signal and converts it to discrete dimming levels. This means that controller 2 translates the dimming signal into multiple dimming steps. Preferably, if the first light source LED1 and the second light source LED2 provide similar light outputs, the number of dimming steps is based on the number of light sources provided. In the provided example, two light sources are provided. Three discrete dimming steps are available.One discrete dimming step may be set to 0% output power, another discrete dimming step may be set to 33% output power, another discrete dimming step may be set to 66% output power, and another discrete dimming step may be set to 100% output power. In this case, driver 1 may be configured not to generate current so that the light source is not powered during the 0% output power dimming step.

[0051] Controller 2 may be configured to control a first switch M1 and a second switch M2 based on the discrete dimming level. Driver 1 may be configured to adjust the current to the light source based on the discrete dimming level. Driver 1 may receive a discrete dimming signal from Controller 2.

[0052] At the first discrete dimming level, the controller 2 may close the first switch M1 and open the second switch M2. In this case, the driver 1 may supply the light source with a current corresponding to the first current. By closing the first switch M1 and opening the second switch M2, the controller 2 allows the first current to flow through the first light source LED1. The driver 1 determines the amplitude of the first current and, therefore, the current density present in the first light source LED1. Preferably, the first current is set to an amplitude that allows the current density in the first light source LED1 to be its optimal current density, enabling the first light source LED1 to emit light most efficiently. The first discrete dimming level allows the lighting device to emit light only from the first light source LED1. This means that a relatively low light output, i.e., a dimmed light output, is provided.

[0053] At the second discrete dimming level, the controller 2 may close the first switch M1 and the second switch M2. In this case, the driver 1 may supply the light source with a current corresponding to the sum of the first current and the second current. Preferably, the first light source LED1 and the second light source LED2 have the same forward voltage. This allows the current supplied by the driver 1 to be distributed between the light sources without requiring additional adjustments. In this example, the first current flows through the first light source LED1 and the second current flows through the second light source LED2. Preferably, the current to the first light source LED1 is such that the first light source LED1 operates at its optimal current density, and the current to the second light source LED2 is such that the second light source LED2 operates at its optimal current density.

[0054] At the third discrete dimming level, the controller 2 may open the first switch M1 and close the second switch M2. By opening the first switch M1 and closing the second switch M2, the controller 2 allows the second current to flow through the second light source LED2. The driver 1 determines the amplitude of the second current and, therefore, the current density present in the second light source LED2. Preferably, the second current is set to an amplitude that allows the current density in the second light source LED2 to be its optimal current density, enabling the second light source LED2 to emit light most efficiently. The third discrete dimming level allows the lighting device to emit light from only the second light source LED2. This means that a relatively low light output, i.e., a dimmed light output, is provided.

[0055] At the first discrete dimming level, the driver 1 powers the first light source LED1, but not the second light source LED2. At the third discrete dimming level, the driver 1 powers the first light source LED1, but not the second light source LED2. At the second discrete dimming level, the driver 1 powers both the first light source LED1 and the second light source LED2. The first and second discrete dimming levels may be used for dimming purposes. The third dimming level may be used to provide a different desired effect. The first and second light source LEDs may have the same forward voltage, but may, for example, provide different color temperatures. The first light source LED1 may be an LED that provides warm white light, and the second light source may be an LED that provides cool white light. The LED may be, for example, a blue LED in which the phosphor layer converts blue light to warm white or cool white light. At the first discrete dimming level, the first light source LED1 is powered, and therefore warm white light is generated by the lighting device with a reduced light output. At the third discrete dimming level, the second light source LED2 is powered, and therefore cool white light is generated by the lighting device with a reduced light output. At the second discrete dimming level, both the first light source LED1 and the second light source LED2 are powered. A combination of warm white light and cool white light is generated by the lighting device.

[0056] As a common practice, a low (first) current is supplied to two light sources to provide a dimmed light output. This reduces the current density in both light sources, effectively lowering the efficiency of both. The inventors' insight is that by simultaneously reducing the current and the number of light sources, the current density remains nearly the same, allowing the dimming to be performed with high efficiency.

[0057] Preferably, the light output generated by the lighting device is higher at the second discrete dimming level than at the first discrete dimming level.

[0058] In the provided example, two light sources are provided. More light sources may be provided in parallel with the first light source LED1 and / or the second light source LED2. Each of these additional light sources may be provided with a corresponding series-connected switch. More light sources allow for the introduction of more discrete dimming levels and can increase the resolution of the dimming steps. Driver 1 may be adapted to provide a current corresponding to each of the discrete dimming levels. The more discrete dimming levels there are, the more current levels may need to be provided by driver 1. Therefore, driver 1 may be adapted to provide multiple discrete current levels to provide the light sources with current corresponding to the discrete dimming levels.

[0059] Figure 3 shows a graph illustrating the relationship between the dimming level and the current supplied to the light source in another example. In this example, driver 1 is adapted to provide a current that can be increased based on the dimming level. Driver 1 can increase or decrease the current to the light source. Fluctuations in current can cause the current density to deviate from the optimal current density, which can affect the efficiency of the light source. Driver 1 may be configured to limit current fluctuations so that the efficiency of the light source is not excessively lost. Preferably, the current through the light source cannot deviate by more than 50% from the maximum current supplied to the light source. This means that the current through at least one light source can fluctuate between 100% and 50% of the current.

[0060] The discrete dimming level is used in a different way than in the previous example. The discrete dimming level is used to determine whether an additional light source needs to be activated or whether another light source should be prevented from being powered. Controller 2 determines the discrete dimming level based on the dimming level it receives. Based on the determined discrete dimming level, Controller 2 determines how many light sources should be activated. In the provided example, Controller 2 determines which switches should be closed and which switches should be opened.

[0061] In Figure 3, eight light sources are used. These eight light sources form eight parallel channels and preferably have substantially the same forward voltage. Preferably, they also have substantially the same current requirement. The dimming level is expressed as a DALI dimming level in the range of 0 to 253. In this example, the dimming curve is a logarithmic dimming curve. This can offer the advantage that the dimming behavior of the lighting device follows the behavior of the human eye. The human eye has logarithmic sensitivity to changes in light intensity. At a dimming level of 0, the controller 2 may be configured so that no light source is connected to the driver 1. Since no power is supplied to the light sources, the driver 1 may be configured not to supply current to the light sources.

[0062] At dimming levels 1 to 175, current is supplied from the driver to a single light source. The current starts at a minimum of 0mA and increases up to 85mA. In this example, the dimming level is used by driver 1 to determine the increasing current to the light source, and by controller 2 to determine how many light sources should be supplied. In this case, the active single light source may not operate at or near its optimal current density because the current range to this single light source varies from 0 to 85mA. Trade-offs in dimming levels may be made to further optimize efficiency. For example, currents lower than 42.5mA (50% of the total current) may not be supplied so as not to over-affect the efficiency of the light source. However, if the maximum current of 85mA corresponds to the optimal current density in the active light source, the effect of reducing the current, and therefore the current density in the light source, will have a smaller effect, for example, than the effect of increasing the current, and therefore the current density beyond the optimal current density.

[0063] At dimming levels 176–205, controller 2 may determine that another discrete dimming level has been reached and therefore allow current from driver 1 to be supplied to an additional light source. In this example, two light sources may be powered. Since two light sources, rather than one, receive current from driver 1, the current through the light sources is almost halved, as seen in the step at dimming level 176 (where the current has decreased to approximately 45mA for each light source). However, driver 1 still provides 85mA. By increasing the dimming level to 205, driver 1 is able to further increase the current through the light sources back up to 85mA. Driver 1 may provide a total current of 170mA at dimming level 205.

[0064] At dimming levels 206-216, controller 2 may determine that another discrete dimming level has been reached. In this example, three light sources may be powered. Since the three light sources are powered by driver 1, the total current supplied by driver 1 is distributed among the three light sources. In this case, 170mA is approximately 57mA per light source at dimming level 206. By increasing the dimming level to 216, driver 1 can further increase the current in the light sources, bringing it back up to 85mA. In this case, driver 1 supplies 255mA to all active light sources.

[0065] At dimming levels 217-226, controller 2 may determine that another discrete dimming level has been reached. In this example, four light sources may be powered. Since the four light sources are powered by driver 1, the total current supplied by driver 1 is distributed among the four light sources. In this case, 255mA is approximately 64mA per light source at dimming level 217. By increasing the dimming level to 226, driver 1 can further increase the current in the light sources, bringing it back up to 85mA. In this case, driver 1 supplies 340mA to all active light sources.

[0066] At dimming levels 227-234, controller 2 may determine that another discrete dimming level has been reached. In this example, five light sources may be powered. Since the five light sources are powered by driver 1, the total current supplied by driver 1 is distributed among the five light sources. In this case, 340mA is approximately 68mA per light source at dimming level 227. By increasing the dimming level to 234, driver 1 can further increase the current in the light sources, bringing it back up to 85mA. In this case, driver 1 supplies 425mA to all active light sources.

[0067] At dimming levels 235-242, controller 2 may determine that another discrete dimming level has been reached. In this example, six light sources may be powered. Since the six light sources are powered by driver 1, the total current supplied by driver 1 is distributed among the six light sources. In this case, 425mA is approximately 71mA per light source at dimming level 235. By increasing the dimming level to 242, driver 1 can further increase the current in the light sources, bringing it back up to 85mA. In this case, driver 1 supplies 510mA to all active light sources.

[0068] At dimming levels 243 to 248, controller 2 may determine that another discrete dimming level has been reached. In this example, seven light sources may be powered. Since the seven light sources are powered by driver 1, the total current supplied by driver 1 is distributed among the seven light sources. In this case, 510mA is approximately 73mA per light source at dimming level 243. By increasing the dimming level to 248, driver 1 can further increase the current in the light sources, bringing it back down to 85mA. In this case, driver 1 supplies 595mA to all active light sources.

[0069] At dimming levels 249-253, controller 2 may determine that another discrete dimming level has been reached. In this example, eight light sources may be powered. Since the eight light sources are powered by driver 1, the total current supplied by driver 1 is distributed among the eight light sources. In this case, 595mA is approximately 74mA per light source at dimming level 249. By increasing the dimming level to 253, driver 1 can further increase the current to the light sources, bringing it back down to 85mA. In this case, driver 1 supplies 680mA to all active light sources. At this discrete dimming level, all eight light sources are active. At dimming level 253, 85mA is supplied to all light sources, and therefore the lighting device emits the maximum possible light.

[0070] In the example presented, eight light sources are used. This is merely one example, and it is clear that other examples may use more or fewer light sources, preferably at least two.

[0071] Figure 4 shows an example of a lighting device. The lighting device has a driver circuit. The driver circuit has a driver 1 configured to supply power to a first light source LED1 and a second light source LED2. The first light source LED1 is coupled in series with the second light source LED2. The series configuration of the first light source LED1 and the second light source LED2 is coupled between the outputs of the driver 1. A first switch M1 is coupled in parallel with the first light source LED1. A second switch M2 is coupled in parallel with the second light source LED2. The switches may function as shunt switches, effectively shunting the corresponding light sources when closed. The driver 1 is configured to supply current to the light sources. A controller 2 is provided to control the first switch M1 and the second switch M2. Preferably, the controller 2 may also be used to control the driver 1. This allows one controller 2 to control both the first switch M1 and the driver 1. Alternatively, controller 2 may include multiple components for different purposes, for example, controlling a first switch M1 separately from driver 1. Controller 2 may be an integral part of the driver. Driver 1 may be configured to receive a mains voltage Mains. The mains voltage Mains is an AC voltage and therefore may be rectified by a rectifier circuit. The rectifier circuit may be part of the driver. Controller 2 may receive a dimming signal from an external device configured to provide a dimming signal. Examples of dimming signals are phase-cut dimming signals, 0-10V dimming signals, DALI dimming signals, DMX dimming signals, or wireless dimming signals. Controller 2 receives the dimming signal and converts it to discrete dimming levels. This means that controller 2 translates the dimming signal into multiple dimming steps. Preferably, if the first light source LED1 and the second light source LED2 provide similar light outputs, the number of dimming steps is based on the number of light sources provided. In the provided example, two light sources are provided. Three discrete dimming steps are available.One discrete dimming step may be set to 0% output power, another discrete dimming step may be set to 33% output power, another discrete dimming step may be set to 66% output power, and another discrete dimming step may be set to 100% output power. In this case, driver 1 may be configured not to generate current so that the light source is not powered during the 0% output power dimming step.

[0072] Controller 2 may be configured to control a first switch M1 and a second switch M2 based on discrete dimming levels. Driver 1 may be configured to adjust the current to the light source based on discrete dimming levels. Driver 1 may receive a discrete dimming signal from Controller 2. The teachings provided in the example where the light sources are coupled in parallel may also apply to the teachings in this example where the light sources are coupled in series.

[0073] When the first switch M1 is open and the second switch M2 is closed, the driver 1 supplies the first current to the first light source LED1. The second light source LED2 is shunted by the second switch M2, and therefore no current flows to the second light source LED2. Therefore, opening the first switch M1 and closing the second switch M2 may be performed at the first discrete dimming level.

[0074] When the first switch M1 is open and the second switch M2 is open, the driver 1 supplies a first current to the first light source LED1 and a second current to the second light source LED2. The first light source LED1 and the second light source LED2 are not shunted by the first switch M1 and the second switch M2, respectively, and therefore current flows to the first light source LED1 and the second light source LED2. Therefore, opening the first switch M1 and the second switch M2 may be performed at a second discrete dimming level.

[0075] When the first switch M1 is closed and the second switch M2 is open, the driver 1 supplies a second current to the second light source LED2. The first light source LED1 is shunted by the first switch M1, and therefore no current flows to the first light source LED1. Therefore, closing the first switch M1 and opening the second switch M2 may be performed at a third discrete dimming level.

[0076] In this example, it may be desirable for the first current and the second current to be the same.

[0077] Figure 5 shows an example of a lighting device implementation. The light source in the lighting device may have its own optics that enable the provision of specific beam angles. In this example, four beam angles Φ1, Φ2, Φ3, and Φ4 are provided. Each beam angle is generated by a combination of different light sources. In this example, four light sources may be used for each corresponding beam angle. Each beam angle may correspond to a discrete dimming level.

[0078] As an example, at the first discrete dimming level, a first current may be supplied to the first light source LED1. As a result, a light output with a beam angle of Φ1 is obtained. At the second discrete dimming level, a second current may be supplied to the second light source LED2. As a result, a light output with a beam angle of Φ2 is obtained. At the third discrete dimming level, a third current may be supplied to the third light source. As a result, a light output with a beam angle of Φ3 is obtained. At the fourth discrete dimming level, a fourth current may be supplied to the fourth light source. As a result, a light output with a beam angle of Φ4 is obtained.

[0079] Other combinations are also possible. For example, at the fourth, third, or second discrete dimming level, all or part of the other light sources may be powered such that they produce light outputs with beam angles of Φ4, Φ3, or Φ2, but also increase light outputs at other angles because a corresponding current is provided to all or part of the other light sources. Preferably, the current supplied to the light sources by the driver 1 is of a magnitude that allows the light sources to be powered at their optimal current density. In this example, the dimming signal may be used to provide different beam angles of the light output of the lighting device depending on the discrete dimming level. Furthermore, the dimming signal may be used to change the amount of light produced by the lighting device depending on the discrete dimming level.

[0080] In the provided example, driver 1 may supply current to the light source in a different manner. The current can be pulse-width modulated to maintain a current level that achieves an optimal current density in the first light source LED1 and / or the second light source LED2, while allowing less light to be emitted by the light source. Thus, the amplitude of the current to the light source remains constant, but the average current to the light source varies based on the duty cycle of the current. This effectively reduces the light output of the light source without affecting the efficiency of the light source. Preferably, the frequency of the PWM current is at a frequency above the frequency perceptible to the human eye, such as 200 Hz. More preferably, the frequency is above 1 kHz.

[0081] In the provided example, the driver may be provided as a switched-mode power supply. Examples of switched-mode power supplies include boost converters, buck converters, buck-boost converters, flyback converters, or resonant converters.

[0082] In the provided example, for simplification, the discrete dimming levels may be evenly distributed across the entire dimming range. It should be understood that this is only one option for converting dimming levels to discrete dimming levels. Alternatively, the discrete dimming levels may be distributed such that lower dimming subranges have more discrete dimming levels than higher dimming subranges, or vice versa.

[0083] In the provided example, the dimming level may be linearly related to the power required by the light source. Other relationships, such as logarithmic or nonlinear, are also possible and may produce the desired effect.

[0084] The definition of a dimming level should be understood as the amount of power that the driver circuit needs to supply to the light source. At a dimming level of 100%, it is desirable for the driver circuit to supply 100% of its rated power. At a dimming level of 0%, it is desirable for the driver circuit to supply 0% of its rated power. Dimming levels between 100% and 0% can be scaled linearly or nonlinearly with respect to the rated power of the driver circuit. In linear scaling, a 50% dimming level may correspond to 50% of the rated power of the driver circuit. In nonlinear scaling, a 50% dimming level may correspond to, for example, 25% of the rated power of the driver circuit.

[0085] In the provided example, controller 2 is configured to prevent current from flowing to any of the light sources. It is clear that controller 2 can do this by using the switches provided in the example.

[0086] In the provided example, the first light source LED1 and / or the second light source LED2 may be semiconductor light sources. Examples of semiconductor light sources are LEDs, laser diodes, and vertical-cavity surface-emitting lasers (VCSELs). Preferably, the LED is formed as a filament.

[0087] In the provided example, the discrete dimming level may be converted into a current amplitude to be generated by driver 1. Driver 1 generates this current and supplies it to the light sources. Controller 2 senses the amplitude of the supplied current and, based on this sense, determines the number of light sources that need to be connected to driver 1 so that the current supplied by driver 1 is appropriately distributed among the light sources.

[0088] In the provided example, the dimming signal may be a digital signal. The digital signal may be derived, for example, from a DALI signal. When multiple lighting devices are used, the discrete dimming levels of each lighting device are similar to those of the others, and therefore, lighting devices receiving the same digital dimming command produce similar light outputs. If an analog dimming signal is provided, tolerances in the electronic components may cause deviations in light output between lighting devices.

[0089] By examining the drawings, this disclosure, and the appended claims, other variations of the disclosed embodiments can be understood by those skilled in the art and can be performed in carrying out the claimed invention. In the claims, the word “comprising” does not exclude other components or steps, and the indefinite article “a” or “an” does not exclude plural. The mere fact that certain means are enumerated in different dependent claims does not indicate that combinations of these means cannot be used advantageously. No reference numeral in the claims should be construed as limiting in scope.

Claims

1. The first light source and A second light source and Driver circuit and A lighting device including, the driver circuit, A driver adapted to provide a first current to the first light source and a second current to the second light source, A controller for controlling the aforementioned driver, Includes, The controller is configured to receive a dimming signal indicating a dimming level for the light output of the light source. The controller is configured to convert the received dimming signal into a plurality of discrete dimming levels, each discrete dimming level corresponding to the amount of current to be supplied to the first light source and / or the second light source by the driver. At a first discrete dimming level, the controller is configured to allow the first current to be supplied to the first light source and to prevent the second current from being supplied to the second light source, wherein the first current has an amplitude that provides a current density in the first light source such that the first light source generates light with a predetermined efficiency. A lighting device in which, at a second discrete dimming level, the controller is configured to allow the first current to be supplied to the first light source and the second current to be supplied to the second light source.

2. The lighting device according to claim 1, wherein, at a third discrete dimming level, the controller is configured to prevent the first current from being supplied to the first light source and to supply the second current to the second light source.

3. The lighting device according to claim 1 or 2, wherein, between two discrete dimming steps, the driver is configured to provide a variable current to only one of the first light source or the second light source based on a dimming signal, while maintaining a constant current through the other of the first light source or the second light source.

4. The lighting device according to any one of claims 1 to 3, wherein the second current has an amplitude that provides a current density in the second light source such that the second light source generates light with a predetermined efficiency.

5. The lighting device according to any one of claims 1 to 4, wherein the first light source and the second light source are coupled in a parallel configuration.

6. The lighting device according to claim 5, wherein the driver circuit includes a first switch coupled in series with the second light source, the controller is configured to open and close the first switch, the first current flows through the first light source when the first switch is open, and the second current flows through the second light source when the first switch is closed.

7. The lighting device according to any one of claims 1 to 5, wherein the driver circuit includes a first switch connected in series with the first light source and a second switch connected in series with the second light source, and the controller is configured to open and close the first switch and the second switch, wherein when the first switch is closed, the first current flows through the first light source, and when the second switch is closed, the second current flows through the second light source.

8. The lighting device according to any one of claims 1 to 7, wherein the driver circuit includes a series combination of a first switch and a second switch between the outputs of the driver, the first light source is coupled in parallel with the first switch, and the second light source is coupled in parallel with the second switch.

9. The lighting device according to any one of claims 6 to 8, wherein the controller is configured to sense a current provided by the driver, and the controller is configured to control the first switch and / or the second switch based on the amplitude of the current provided by the driver.

10. The lighting device according to any one of claims 1 to 9, wherein the forward voltage of the first light source is smaller than the forward voltage of the second light source.

11. The lighting device according to any one of claims 1 to 10, wherein, at the first discrete dimming level, the driver is configured to provide the first light source with a first current such that the current density through the first light source enables the first light source to emit light close to the highest efficiency of the first light source.

12. In the second discrete dimming level, the driver, The current density through the first light source is such that the first light source emits light close to the highest efficiency of the first light source, and the first current is supplied to the first light source, The second current is supplied to the second light source such that the current density through the second light source enables the second light source to emit light close to its maximum efficiency. A lighting device according to any one of claims 1 to 11, configured as described above.

13. The lighting device according to any one of claims 1 to 12, wherein the first light source generates a color or color temperature different from the color or color temperature of the second light source.

14. The lighting device according to any one of claims 1 to 13, comprising at least three light sources, wherein the number of dimming levels is based on the number of light sources.

15. The lighting device according to any one of claims 1 to 14, wherein the light generated by the first light source is emitted onto the first surface, the light generated by the second light source is emitted onto the second surface, and the first surface does not overlap with the second surface at least partially.

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