Ultra-high efficiency dimmable LED driver with switchable LED load

Abstract

The present invention relates to a lighting device comprising: a light source having a parallel or series configuration of a first sub-load and a second sub-load; a first driver adapted to supply power to the light source; a second driver adapted to supply power to the light source; a controller adapted to receive dimming signals and adapted to allow or deny power to be supplied to the light source by the first driver and / or the second driver based on the dimming level; and a control circuit adapted to receive a control signal, which is configured to operate and deactivate the first sub-load and the second sub-load based on the control signal.

Description

Technical Field

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

Background Art

[0002] For the lighting industry, the requirements for energy efficiency have become more stringent, especially due to the new European Union energy labelling introduced on September 1, 2021. This new labelling follows the trend of improving the energy efficiency of lighting products. By that time, an increasing number of light sources had achieved a label rating of A+ or A++, making it impossible for customers to examine the differences in luminous efficiency between products. With the new labelling, light sources will be more dispersed across the labelling range again. This also means that, for example, a lamp that was rated A++ under the old system is now labelled C. Therefore, it is desired to further improve the energy efficiency of light sources.

[0003] Particularly in the case of dimmable light sources, there is a strong desire to improve efficiency. During dimming, especially deep dimming, fixed losses in the driver, such as those caused in the control circuit, become a major part of the losses in the lighting device. The driver is generally designed according to the rated power of the driver, and therefore, the fixed losses also depend on the rated power of the driver. Generally, a driver with a lower rated output power has lower fixed power losses. This clearly affects the total amount of power that can be supplied to the load. A driver with a higher rated power can supply more power with its output, but this is accompanied by more fixed losses. Therefore, it is desired to provide a lighting device that can provide a good dimming function while operating with very high efficiency.

Summary of the Invention

Problems to be Solved by the Invention

[0004] The objective of the present invention is to provide a lighting device that offers improved efficiency while providing a dimming function. [Means for solving the problem]

[0005] To provide a solution, a lighting device is provided in a first embodiment of the present invention. The lighting device is - A light source having a parallel or series configuration of a first sub-load and a second sub-load, - A first driver adapted to supply power to the light source, - A second driver adapted to supply power to the aforementioned light source, - A controller adapted to receive dimming signals and to allow or deny power to be supplied to the light source by the first driver and / or the second driver based on the dimming level, - A control circuit adapted to receive a control signal, which is configured to activate and deactivate the first sub-load and the second sub-load based on the control signal.

[0006] The lighting device has a first driver and a second driver. Both drivers can supply power to the light source. The light source has an input and an output. Preferably, the driver supplies power to this input. Preferably, the input is the only input to the light source for supplying power. The light source has a first sub-load and a second sub-load. The first sub-load may be a first sub-lighting load, and the second sub-load may be a second sub-lighting load. The lighting device can receive dimming signals, which may be received by the controller. Examples of dimming signals are phase-cut dimming signals, 0 to 10V dimming signals, DALI dimming signals, DMX dimming signals, or wireless dimming signals. The controller determines the amount of power to be supplied to the light source. Therefore, the controller controls the first driver and the second driver to supply power to the light source based on the dimming level. Preferably, the controller may be used to allow or deny the drivers to supply power to the light source. The controller can adjust the amount of power supplied to the light source by controlling the number of drivers that can supply power to the light source. A control circuit is provided for operating and deactivating the first sub-load and the second sub-load. The control circuit receives a control signal that provides the control circuit with information on which of the sub-loads should be operated or deactivated. Thus, the controller is used to determine the amount of power supplied to the light source, and the control circuit is used to determine how the power is divided between the first sub-load and the second sub-load.

[0007] In a further example, the light source has a third sub-load, the lighting device has a third driver adapted to supply power to the light source, the controller is further adapted to allow or deny power supply by the third driver, and the control circuit is further configured to activate and deactivate the third sub-load.

[0008] A third driver and a third sub-load may be provided. The controller may be configured to control the third driver in the same way that the controller controls the first and second drivers. Therefore, the lighting device has a third driver and a third sub-load. This makes it possible to provide more dimming steps and improve the dimming resolution. The lighting device may have four or more drivers and four or more sub-loads. Preferably, the number of drivers is equal to the number of sub-loads.

[0009] In a further example, the control signal is supplied by the controller.

[0010] Preferably, the control signal is supplied by the controller. The controller may process the received dimming signal to derive the control signal. The control signal can then be supplied to the control circuit. The control circuit may receive the control signal from another source instead of the controller. For example, the current to the light source may be used as a control signal that enables the control circuit to determine which sub-load should be activated.

[0011] In a further example, the controller is configured to allow power from the first driver to be supplied to the light source and to deny power from the second driver to be supplied to the light source at a first dimming level.

[0012] At the first dimming level, the controller may determine that the first driver is permitted to supply power to the light source, and the second driver is denied supplying power to the light source. If only two drivers exist, at the first dimming level, the first driver may be the only driver supplying power to the light source.

[0013] In a further example, the control circuit is configured to activate the first sub-load and deactivate the second sub-load.

[0014] Preferably, when the first driver supplies power to the light source and the second driver does not supply power to the light source, the control circuit is enabled to activate the first sub-load and deactivate the second sub-load. In this case, the lighting device is configured to supply power using the first driver. In this case, the power is supplied to the first sub-load. This makes it possible to optimize the power supplied by the first driver to match the power that can be consumed by the first sub-load. In this case, in an example where only two drivers are provided, the first driver may supply power only to the first sub-load.

[0015] In a further example, the current supplied by the first driver corresponds to the optimal current density of the first sub-load.

[0016] Preferably, the power supplied to the first sub-load by the first driver supplies a current to the first sub-load that corresponds to the optimal current density of the first sub-load. When the first sub-load is supplied with the optimal current density, the first sub-load supplies light with its optimal efficiency. In this example, the lighting device supplies a light output lower than the maximum possible light output at the first dimming level. The light output is supplied with relatively high efficiency. Preferably, the first driver is configured to supply power that supplies the optimal current density at the first driver's highest efficiency. Therefore, the lighting device operating at the first dimming level has a driver and sub-load that operate with relatively high efficiency.

[0017] In a further example, the controller is configured to refuse to supply power from the first driver to the light source and to allow power from the second driver to the light source at a second dimming level.

[0018] At the second dimming level, the controller may decide that the first driver is denied power to the light source, and the second driver is permitted to power the light source. If only two drivers are present, at the second dimming level, the second driver may be the only driver supplying power to the light source.

[0019] In a further example, the control circuit is configured to deactivate the first sub-load and activate the second sub-load.

[0020] Preferably, when the first driver does not supply power to the light source and the second driver supplies power to the light source, the control circuit enables the operation of the second sub-load and the deactivation of the first sub-load. In this case, the lighting device is configured to supply power using the second driver. In this case, the power is supplied to the second sub-load. This makes it possible to optimize the power supplied by the second driver to match the power that can be consumed by the second sub-load. In this case, in an example where only two drivers are provided, the second driver may supply power only to the second sub-load.

[0021] In a further example, the current supplied by the second driver corresponds to the optimal current density of the second sub-load.

[0022] The power supplied to the second sub-load by the second driver preferably supplies a current corresponding to the optimum current density of the second sub-load to the second sub-load. When supplying the optimum current density to the second sub-load, the second sub-load supplies light at its optimum efficiency. In this example, the lighting device supplies a light output lower than the maximum possible light output at the second dimming level. The light output is supplied with a relatively high efficiency. Preferably, the second driver is configured to supply power that supplies the optimum current density with the highest efficiency of the second driver itself. Therefore, the lighting device operating at the second dimming level has a driver and a sub-load that operate with relatively high efficiency.

[0023] In a further example, the maximum power capability of the first driver is approximately the same as the maximum power capability of the second driver.

[0024] As an example, the first driver and the second driver are configured such that they can supply the same maximum power to the light source. This means that in the example of two drivers, each driver can supply 50% of the maximum power that can be supplied to the light source. The design of the lighting device can be simplified in a simple, modular way by providing the desired number of the same drivers.

[0025] In another example, the maximum power capability of the first driver is lower than the maximum power capability of the second driver.

[0026] As an example, the first driver has a maximum power capability lower than the maximum power capability of the second driver.

[0027] If the first driver has a maximum power capability lower than that of the second driver, this enables the first driver to supply less power at the first dimming level than the second driver supplies at the second dimming level. Non-linear dimming steps can be introduced in this way. Another advantage can be that additional dimming steps with different light outputs can be provided to the lighting device. As an example, the first sub-load may have a maximum power capability smaller than that of the second sub-load. Therefore, the first driver can supply less power to the first sub-load than the second driver supplies to the second sub-load. Therefore, the power supplied at the first dimming level may be lower than the power supplied at the second dimming level. The third dimming level can be, for example, at maximum power to the light source where both drivers supply power to the light source.

[0028] In a further example, the first driver and the second driver are non-dimmable drivers.

[0029] To provide a very energy-efficient lighting device, it is desirable that the driver is a non-dimmable driver. The driver is designed to supply a single amount of power. Therefore, the driver can be optimized to supply this single amount of power at its highest efficiency. Therefore, when the driver is active, the driver is always active at its highest efficiency.

[0030] In a further example, the light generated by the first sub-load is emitted on a first surface, the light generated by the second sub-load is emitted on a second surface, and the first surface does not at least partially overlap the second surface.

[0031] A beam shaping mechanism may be introduced as an alternative to or in addition to modifying the light intensity, color, or color temperature of the light source. If the first light source emits light from a surface different from the surface from which the second light source emits light, the dimming level may be used to illuminate the different surface. The total beam angle of the lighting device may be adjusted based on the dimming level. [Brief explanation of the drawing]

[0032] Here, an example of the present invention will be described with reference to the attached drawings. [Figure 1] An example of a circuit diagram is shown. [Figure 2] Here is another example of a circuit diagram. [Figure 3] This graph shows the relationship between output power and dimming level. [Figure 4] Another graph showing the relationship between output power and dimming level is shown. [Figure 5] Here is another example of a circuit diagram. [Figure 6] Another graph showing the relationship between output power and dimming level is shown. [Figure 7] Another graph showing the relationship between output power and dimming level is shown. [Figure 8] Here is another example of a circuit diagram. [Figure 9] Here is another example of a circuit diagram. [Modes for carrying out the invention]

[0033] The present invention will be described with reference to the figures.

[0034] The detailed descriptions and specific examples illustrate exemplary embodiments of the apparatus, systems, and methods, but are for illustrative purposes only and should not be understood as being 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. It should also be understood that the figures are for illustrative purposes only and are not drawn to scale. It should also be understood that throughout the figures, the same reference numerals are used to indicate the same or similar parts.

[0035] Figure 1 shows an example circuit diagram of a lighting device having a driver circuit that supplies output power to a light source. The driver circuit may be coupled to the mains power supply via a rectifier circuit having four diodes D10, D11, D12, and D13. The rectifier circuit supplies a rectified mains power voltage. In the example shown, a first driver D1 and a second driver D2 receive the rectified mains power voltage. A controller C is used to control the first driver D1 and the second driver D2. Controller C may receive a dimming signal Dim. The dimming signal Dim may be supplied by a dimmer or an external device that supplies dimming commands. Examples of devices that can supply dimming signals include phase-cut dimmers, 0-10V dimmers, DALI dimmers, DMX dimmers, or wireless remote devices for supplying dimming signals. The first driver D1 and the second driver D2 are configured to supply power to the same light source.

[0036] The light source has a first input to which the outputs of the first driver D1 and the second driver D2 are coupled. Preferably, the light source is an LED light source. The LED light source may be a string of LEDs coupled in series, preferably a string of LEDs forming a filament. Other devices or combinations of devices, such as laser diodes or VCSELs, may also be coupled in series. For clarity, the example shows LEDs as the light source.

[0037] Controller C receives a dimming signal and uses this dimming signal to supply control signals for the first driver D1 and the second driver D2. Preferably, Controller C converts the dimming signal into discrete dimming levels. Controller C may determine the number of discrete dimming levels based on the number of drivers provided in the driver circuit. In the example of drivers with the same power rating, the number of discrete dimming levels can be determined by the equation D = 1 + N, where D is the number of discrete dimming levels and N is the number of drivers. In the example of two drivers, the number of discrete dimming levels is three. The dimming signal has a dimming range from 0% to 100%. Controller C reads the dimming signal and generates discrete dimming levels based on the value of the dimming signal. The discrete dimming levels are set to 0% output power, 50% output power, and 100% output power. In this example, a dimming signal between 0% and 25% can be converted to 0% as a discrete dimming level. A dimming signal between 26% and 75% can be converted to 50% as a discrete dimming level. A dimming signal between 76% and 100% can be converted to 100% as a discrete dimming level. These values ​​are merely examples of how the dimming range of a dimming signal should be converted to discrete dimming levels, and it is clear that other ranges for converting a dimming signal to discrete dimming levels are also possible. At 0% output power, the controller supplies a control signal to the drivers that prevents the first driver D1 and the second driver D2 from supplying power to the light source. Both drivers may be turned off. At 50% output power, controller C supplies a control signal to the drivers that allows one of the drivers to supply the rated power to the load and prevents the other driver from supplying power to the load. At 100% output power, controller C supplies a control signal to the drivers that allows both drivers to supply their rated power to the light source.

[0038] At all dimming levels, the lighting system can operate with the highest possible efficiency. Light efficiency can be further increased if fewer than the maximum number of drivers power the light source.

[0039] The light source comprises a first sub-load LED1 and a second sub-load LED2. The first sub-load LED1 has a first illumination load, indicated in this example as an LED load. Any number of LEDs can be selected as desired for any design. The LEDs can be arranged in series, in parallel, or in a combination thereof. A first switching element M10 is in series with the first illumination load. The first switching element M10 is indicated as a MOSFET, but other types of switching elements are also possible. Examples of switching elements are transistors or relays. The first switching element is controlled by a control circuit 1. The second sub-load LED2 has a second illumination load LED2, indicated in this example as an LED load. Any number of LEDs can be selected as desired for any design. The LEDs can be arranged in series, in parallel, or in a combination thereof. The control circuit 1 is used to control the first switching element M10. Therefore, the control circuit 1 is configured to adjust the distribution of power supplied to the sub-loads by the driver.

[0040] For example, when the first switching element M10 is closed, all current can flow through the first sub-load LED1, and no power flows through the second sub-load LED2. Therefore, any power supplied by either driver is supplied to the first sub-load LED1. This is especially true if the forward voltage of the first sub-load LED1 is lower than the forward voltage of the second sub-load LED2. For example, when the first driver D1 supplies power to the light source, it may be desirable for the control circuit 1 to close the first switching element M10, allowing all the power supplied by the first driver D1 to be supplied to the first sub-load LED1, while no power is supplied to the second sub-load LED2. In this example, the second driver D2 supplies no power to the light source at all.

[0041] When the first switching element M10 is open, no current can flow through the first sub-load LED1. Therefore, any power supplied by either driver is supplied to the second sub-load LED2. For example, when the second driver D2 supplies power to the light source, it may be desirable for the control circuit 1 to open the first switching element M10, allowing all the power supplied by the second driver D2 to be supplied to the second sub-load LED2, while the first sub-load LED1 is not supplied with power. In this example, the first driver D1 supplies no power to the light source at all.

[0042] Preferably, the first driver D1 is configured to supply power at its rated power. This means that the first driver D1 supplies power with very high efficiency. More preferably, the first sub-load LED1 is designed to receive this rated power and convert this rated power with very high efficiency. This means that the optimal current density of the first sub-load LED1 is matched to the current supplied by the first driver D1. In this example, it may be desirable that the first driver D1 be configured to supply power only at the rated power level. This means that the first driver D1 is a non-dimmable driver and therefore can only output a single amount of power.

[0043] Preferably, the second driver D2 is configured to supply power at its rated power. This means that the second driver D2 supplies power with very high efficiency. More preferably, the second sub-load LED2 is designed to receive this rated power and convert this rated power with very high efficiency. This means that the optimal current density of the second sub-load LED2 is matched to the current supplied by the second driver D2. In this example, it may be desirable that the second driver D2 be configured to supply power only at the rated power level. This means that the second driver D2 is a non-dimmable driver and therefore can only output a single amount of power.

[0044] For example, the first driver D1 and the second driver D2 may be configured to supply power to the light source simultaneously. This may be done, for example, to supply maximum power to the light source at a 100% dimming level. Preferably, the first sub-load LED1 and the second sub-load LED2 are designed to provide a proper distribution of the total power between the first sub-load LED1 and the second sub-load LED2 when both drivers are supplying power to the light source and the control circuit 1 is closed by the first switching element M10. This may be done by ensuring that the forward voltage of the first sub-load LED1, with the voltage across the first switching element M10 added, matches the forward voltage of the second sub-load LED2.

[0045] Figure 2 shows an example of a detailed circuit diagram of the circuit shown in Figure 1. In the example shown, rectifier circuits D10, D11, D12, and D13 are provided. The rectifier circuits supply the rectified voltage that is supplied to the first driver D1 and the second driver D2. The first driver D1 and the second driver D2 are designed as boost converters. The first driver D1 and the second driver D2 are coupled in parallel at their inputs to supply parallel power to the light source. The first driver D1 has a first inductor L1, a first switching element M1, and a first diode D5. The second driver D2 has a second inductor L2, a second switching element M2, and a second diode D6. The first diode D5 and the second diode D6 provide two functions. These diodes form freewheeling diodes for the boost converter topology, allowing the outputs of the first diode D5 and the second diode D6 to be coupled to each other. In topologies other than boost converters, such as buck converters, an additional diode may be required for each driver to enable coupling of drivers at the driver output. Controller C supplies control signals to the first driver D1 and the second driver D2. In this example, the control signals may be supplied directly to the gates of the first switching element M1 and the second switching element M2, respectively. Thus, Controller C determines the power that can be supplied to the light source. Preferably, Controller C controls the drivers such that the power supplied to the light source corresponds to the power required for the light source according to the discrete dimming level.

[0046] Figure 3 shows a graph illustrating the relationship between driver output power and dimming level when two drivers with nearly equal power ratings are provided. The dimming signal is received by controller C and interpreted as a dimming level. The controller determines discrete dimming levels based on the dimming level. In this example, there are three discrete dimming levels, one at 0% output power, one at 50% output power, and the last one at 100% output power. In this example, controller C decides that between 0% and 33% dimming levels, the discrete dimming level is set to 0% output power. Between 34% and 66% dimming levels, the discrete dimming level is set to 50%. Between 67% and 100% dimming levels, the discrete dimming level is set to 100%. This means that in the dimming range between 0% and 33%, no power is supplied to the light source. Between a 34% dimming level and a 66% dimming level, the light source is supplied with 50% of its output power. Controller C activates one driver to supply the rated power corresponding to 50% of the output power to the light source, while preventing the other driver from supplying power to the light source. Between a 67% dimming level and a 100% dimming level, the light source is supplied with 100% of its output power. Controller C activates both drivers to supply their rated power corresponding to 100% of the output power to the light source. It is clear that other relationships can be derived between dimming levels and discrete dimming levels while maintaining the same discrete dimming levels.

[0047] Figure 4 shows a graph illustrating the relationship between the output power and dimming level of a driver circuit when two drivers with different power ratings are provided. The dimming signal is received by controller C and interpreted as a dimming level. Controller C determines discrete dimming levels based on the dimming level. In this example, there are four discrete dimming levels, one at 0% output power, one at 25% output power, one at 75% output power, and the last one at 100% output power. The number of discrete dimming levels is:

number

[0048] Figure 5 shows an example of a circuit diagram of a lighting device. The lighting device has additional drivers. The driver circuit has a first driver D1, a second driver D2, and a third driver D3. In the example shown, rectifier circuits D10, D11, D12, and D13 are provided. The rectifier circuits supply rectified voltages to the first driver D1, the second driver D2, and the third driver D3. The first driver D1, the second driver D2, and the third driver D3 are coupled in parallel at their inputs and supply parallel power to the light source LEDs. Controller C supplies control signals to the first driver D1, the second driver D2, and the third driver D3. Thus, Controller C determines the power that can be supplied to the light source. Preferably, Controller C controls the drivers so that the power supplied to the light source corresponds to the power required for the light source according to discrete dimming levels. Preferably, the lighting device has a third sub-load LED3 arranged in parallel with other sub-loads. In this example, the first sub-load LED1 is coupled in series with the first switching element M10. The second sub-load LED2 is connected in series with the second switching element M11. In this example, the third sub-load LED3 is not connected in series with a switching element, but connecting the third sub-load LED3 in series with a switching element is an option. When the first switching element M10 is closed and the second switching element M11 is open, the sub-loads may be configured so that the driver supplies power only to the first sub-load LED1. When the first switching element M10 is open and the second switching element M11 is closed, the sub-loads may be configured so that the driver supplies power only to the second sub-load LED2. When the first switching element M10 and the second switching element M11 are open, no current can flow through the first sub-load LED1 and the second sub-load LED2. Therefore, any power supplied by the driver is supplied to the third sub-load LED3. Providing a switching element in series with the third sub-load LED3 allows for better control of power distribution between sub-loads.

[0049] Figure 6 shows an example graph of the relationship between driver output power and dimming level when three drivers are provided. In this example, it is assumed that the drivers have approximately the same power rating. In this example, four discrete dimming levels are derived: 0%, 33.33%, 66.67%, and 100%. At dimming levels between 0% and 24%, the discrete dimming level is set to 0%, resulting in no power being supplied to the light source. At dimming levels between 25% and 50%, the discrete dimming level is set to 33.33%, resulting in controller C controlling one driver to supply power to the light source at its corresponding power rating. This means that 33% of the total power that can be supplied by the driver circuit is supplied to the light source LED. At dimming levels between 26% and 75%, the discrete dimming level is set to 66.67%, resulting in controller C controlling two of the three drivers to power the light source at their corresponding rated power. This means that 66.67% of the total power that can be supplied by the driver circuit is supplied to the light source. At dimming levels between 76% and 100%, the discrete dimming level is set to 100%, resulting in controller C controlling all drivers to power the light source LEDs at their corresponding rated power. This means that 100% of the total power that can be supplied by the driver circuit is supplied to the light source.

[0050] Figure 7 shows an example graph of the relationship between driver output power and dimming level when three drivers are provided. In this example, it is assumed that the drivers have different power ratings. In this example, seven discrete dimming levels are derived, namely, one at 0% output power, one at 12.5% ​​output power, one at 25% output power, one at 37.5% output power, one at 75% output power, one at 87.5% output power, and the last one at 100% output power. For example, the first driver D1 may have a power rating of 1W, the second driver D2 may have a power rating of 2W, and the third driver D3 may have a power rating of 5W, resulting in a maximum power of 8W being supplied by the drivers. In this example, at dimming levels between 0% and 14.3%, the discrete dimming level is set to 0%, resulting in no power being supplied to the light source. At dimming levels between 14.4% and 28.6%, the discrete dimming level is set to 12.5%, resulting in the light source being powered by the first driver D1 alone at its rated power. When only the first driver D1 powers the light source at its rated power, the light source receives 1W, which corresponds to 12.5% ​​of the total output power. Preferably, the first driver D1 supplies 1W of power to the first sub-load LED1. Preferably, the first sub-load LED1 has optimal light generation at 1W. The current supplied by the first driver D1 can supply the first sub-load LED1 with a current density close to the optimal current density of the first sub-load LED1. At dimming levels between 28.7% and 42.9%, the discrete dimming level is set to 25%, resulting in the light source being powered by the second driver D2 alone at its rated power. When only the second driver D2 supplies power to the light source at its rated power, the light source receives 2W, which corresponds to 25% of the total output power. Preferably, the second driver D2 supplies 2W of power to the second sub-load LED2. Preferably, the second sub-load LED2 has optimal light generation at 2W.The current supplied by the second driver D2 can supply the second sub-load LED2 with a current density close to the optimal current density of the second sub-load LED2. At dimming levels between 43% and 57.1%, the discrete dimming level is set to 37.5%, resulting in the light source being powered at the rated power of the first and second drivers D1 and D2 by only the first and second drivers D2. At dimming levels between 57.2% and 71.4%, the discrete dimming level is set to 75%, resulting in the light source being powered at the rated power of the first and third drivers D1 and D3 by only the first and third drivers D3. At dimming levels between 71.5% and 85.7%, the discrete dimming level is set to 87.5%, resulting in the light source being powered at the rated power of the second and third drivers D2 and D3 by only the second and third drivers D3. At dimming levels between 85.8% and 100%, the discrete dimming level is set to 100%, resulting in the first driver D1, second driver D2, and third driver D3 supplying power to the light source at their rated power. In the example where only the third driver supplies power to the light source, the third driver D3 supplies 5W of power to the third sub-load LED3. Preferably, the third sub-load LED3 has optimal light generation at 5W. The current supplied by the third driver D3 can supply the third sub-load LED3 with a current density close to the optimal current density of the third sub-load LED3.

[0051] Figure 8 shows an example of a circuit diagram that includes an improved light source that can operate with a driver circuit as shown in the example. The light source LEDs receive power from the driver. The light source has a first sub-load LED1 and a second sub-load LED2. The first sub-load LED1 and the second sub-load LED2 are coupled in parallel. Preferably, the first sub-load LED1 and the second sub-load LED2 have approximately the same forward voltage. Preferably, the first sub-load LED1 and the second sub-load LED2 are provided as filaments. Although the first sub-load LED1 and the second sub-load LED2 are shown as single LEDs, more LEDs may be coupled in series to form a string or filament of LEDs. A first switching element M10 is provided in series with the first sub-load LED1. A second switching element M11 is provided in series with the second sub-load LED2. A control circuit 1 is configured to control the first switching element M10 and the second switching element M11. The control circuit 1 is configured to sense the voltage or current parameters supplied by the driver. Examples of parameters may include the frequency, duty cycle, or amplitude of a voltage or current. The parameters are used by the control circuit 1 to determine how the first switching element M10 and the second switching element M11 are controlled. For example, frequency modulation of the voltage or current supplied by the driver may provide the control circuit 1 with information to determine which of the switching elements should be controlled. For example, a 1 kHz frequency modulation may provide the control circuit 1 with an indication to close the first switching element M10 and open the second switching element M11; a 2 kHz modulation may cause the first switching element M10 to open and the second switching element M11 to close; and a 3 kHz modulation may cause the first switching element M10 to close and the second switching element M11 to close. As another example, similar control can be provided by changing the amplitude of the voltage or current supplied by the driver. A change in voltage or current may change the control of the first switching element M10 and the second switching element M11.The advantage of controlling the light source configuration according to the example above is that power and data can be transmitted from the driver to the light source with just two wires, which is particularly beneficial when the light source is designed as a filament in a light bulb, such as a retrofit bulb with a screw-in or plug-in base. In such situations, the number of wires that can be provided through the stem may be limited. Using the dimming technique shown in the example allows for easy dimming of the filaments, while the control circuit 1 allows the supplied power to be divided between the filaments. Preferably, the first sub-load LED 1 and the second sub-load LED 2 have different colors or color temperatures. Preferably, the first sub-load LED 1 has a warm color temperature, and the second sub-load LED 2 has a cool color temperature. Therefore, parameters can be used to allow the control circuit 1 to adjust the color or color temperature emitted by the light source. The opening and closing of the first switching element M10 and the second switching element M11 may be a continuous process, each with its own duty cycle, for example, in PWM control, where the first switching element M10 is closed or the second switching element M11 is closed. Preferably, this switching process is carried out at a frequency above 100 Hz, more preferably above 2 kHz. In other examples, to provide simple control of the control circuit 1, the opening and closing of the first switching element M10 and the second switching element M11 may be a single event, for example, when the lighting device is started up. During operation, the open and closed states of the first switching element M10 and the second switching element M11 can be changed by different commands, such as commands to change the color or color temperature.

[0052] Figure 9 shows an example of a circuit diagram that includes an improved light source that can operate with a driver circuit as shown in the example. A first sub-load LED1 is coupled in series with a second sub-load LED2. The series configuration of the first sub-load LED1 and the second sub-load LED2 is coupled between the outputs of the driver. A first switching element M10 is provided in parallel with the first sub-load LED1. A second switching element M11 is provided in parallel with the second sub-load LED2. The switching elements act as shunt switches and, when closed, can substantially shunt the corresponding parallel sub-loads. A control circuit 1 is provided to control the first switching element M10 and the second switching element M11. The control circuit 1 may have multiple components for different purposes, for example, to control the first switching element M10 and the second switching element M11. The control circuit 1 may be an integrated part of the controller C.

[0053] Preferably, when the first sub-load LED1 and the second sub-load LED2 supply similar light output, the number of dimming steps is based on the number of sub-loads and corresponding switching elements provided. In the example shown, two sub-loads are provided. Three discrete dimming steps are available. One discrete dimming step can be set to 0% output power, another discrete dimming step can be set to 33% output power, another discrete dimming step can be set to 66% output power, and another discrete dimming step can be set to 100% output power. In this case, the driver may be configured not to generate current so that the light source is not powered during the 0% output power dimming step.

[0054] The control circuit 1 may be configured to control the first switching element M10 and the second switching element M11 based on discrete dimming levels. The driver may be configured to adjust the current to the light source based on discrete dimming levels. The driver may receive discrete dimming signals from the controller C. The teachings provided in the example where the subloads are coupled in parallel may also apply to the teachings in this example where the subloads are coupled in series.

[0055] When the first switching element M10 is open and the second switching element M11 is closed, the driver supplies a first current to the first sub-load LED1. The second sub-load LED2 is shunted by the second switching element M11, and therefore no current flows through the second sub-load LED2. Therefore, at the first discrete dimming level, it is possible to open the first switching element M10 and close the second switching element M11.

[0056] When the first switching element M10 is open and the second switching element M11 is open, the driver supplies a first current to the first sub-load LED1 and a second current to the second sub-load LED2. The first sub-load LED1 and the second sub-load LED2 are not shunted by the first switching element M10 and the second switching element M11, respectively, and therefore current flows through the first sub-load LED1 and the second sub-load LED2. Therefore, at the second discrete dimming level, it is possible to open the first switching element M10 and the second switching element M11.

[0057] When the first switching element M10 is closed and the second switching element M11 is open, the driver supplies a second current to the second sub-load LED2. The first sub-load LED1 is shunted by the first switching element M10, and therefore no current flows through the first sub-load LED1. Therefore, at the third discrete dimming level, it is possible to close the first switching element M10 and open the second switching element M11.

[0058] In this example, it may be desirable for the first current and the second current to be the same.

[0059] In the example shown, controller C may determine the number of discrete dimming levels based on the number of drivers provided in the driver circuit. In the example of drivers with the same power rating, the number of discrete dimming levels can be determined by the equation D = 1 + N, where D is the number of discrete dimming levels and N is the number of drivers. In the example where two drivers are provided, the number of discrete dimming levels is three. The dimming signal has a dimming range from 0% to 100%. Controller C reads the dimming signal and generates discrete dimming levels based on the value of the dimming signal. The discrete dimming levels are set to 0% output power, 50% output power, and 100% output power. In this example, a dimming signal between 0% and 25% can be converted to 0% as a discrete dimming level. A dimming signal between 26% and 75% can be converted to 50% as a discrete dimming level. Dimming signals between 76% and 100% can be converted to 100% as discrete dimming levels. These values ​​are merely examples of how the dimming range of a dimming signal should be converted to discrete dimming levels, and it is clear that other ranges for converting dimming signals to discrete dimming levels are also possible. At 0% output power, the controller supplies control signals to the drivers that prevent the first driver D1 and the second driver D2 from supplying power to the light source. Both drivers may be turned off. At 50% output power, the controller C supplies control signals to the drivers that allow one of the drivers to supply rated power to the load and prevent the other driver from supplying power to the load. Preferably, the first driver D1 may supply power to the first sub-load LED1, and the second driver D2 may not supply any power to the light source. In other examples, the second driver D2 may supply power to the second sub-load LED2, and the first driver D1 may not supply any power to the light source. At 100% output power, controller C supplies control signals to the drivers, enabling both drivers to supply their rated power to the light source.

[0060] In the example shown, controller C may determine the number of discrete dimming levels based on the number of drivers provided in the driver circuit. In the example of drivers with different power ratings, the number of discrete dimming levels is:

number

[0061] In the example shown, the controller C and additional peripheral electrical components may also be powered using a dedicated power supply. An auxiliary power supply may be provided for powering the controller C. Preferably, the auxiliary power supply is electrically isolated from the light source. Therefore, the auxiliary power supply is a power supply dedicated to the controller C. The auxiliary power supply cannot supply power to the light source and can therefore be optimized for powering the controller C.

[0062] During the standby mode of the lighting device, no power is supplied to the light source, and therefore the driver can be turned off. However, the controller C may need to operate in standby mode, for example, to receive control commands to activate the lighting device. In that case, the controller C requires less power than when the lighting device is operating. An additional auxiliary power supply may be provided to power the controller C and surrounding electrical components during standby. The additional auxiliary power supply is optimized to power the controller C in standby mode.

[0063] According to the definition of rated power, it can be understood that a driver has a specified power capacity. At this power capacity, the driver supplies power to the light source most efficiently. In this case, the driver's design is optimized to enable the highest efficiency to be achieved at this rated power level. The rated power may be the maximum power that the driver can supply. In other cases, the rated power may be lower than the maximum power level. If the driver supplies power different from the rated power, for example, power higher or lower than the rated power, the driver's efficiency decreases. Therefore, for maximum efficiency, it is desirable to operate the driver at its rated power whenever it needs to supply power to the light source.

[0064] In the example shown, the drivers may be separate devices comprising distinct components. To improve the use of space and components, some components may be reused among the drivers.

[0065] In the example shown, the dimming level is linearly related to the power required for the light source. Other relationships, such as logarithmic or nonlinear, are possible and may produce the desired effect.

[0066] In the example shown, for the sake of clarity, the discrete dimming levels are evenly distributed across the entire dimming range. It should be understood that this is merely one option for converting dimming levels to discrete dimming levels. In other examples, the discrete dimming levels may be distributed such that lower dimming subranges have more discrete dimming levels than higher dimming subranges, or vice versa.

[0067] The definition of a dimming level is understood as the percentage of power that needs to be supplied to the load by the driver circuit. 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.

[0068] The examples shown illustrate the use of two or three drivers. It should be clearly understood that more drivers can be used. Furthermore, the more drivers used, the more discrete dimming levels can be provided.

[0069] The example shown uses a MOSFET as the switching element, but other types of switching elements are also possible. Examples of switching elements include transistors or relays.

[0070] The driver may be provided as a switch-mode power supply. Examples of switch-mode power supplies include boost converters, buck converters, buck-boost converters, flyback converters, or resonant converters. Instead of operating the switching element as an open or closed switch, the switching element may also be operated in its linear operating region. This allows for better control of power distribution between subloads.

[0071] A light source can be considered a single light source with an input and a return. The driver supplies power to the input and return.

[0072] A person skilled in the art will be able to understand and achieve, in carrying out the claimed invention, other variations of the disclosed embodiments by studying the drawings, specification and appended claims. In the claims, the word “has” does not exclude other elements or steps, and singular notation does not exclude plurality. The mere fact that certain means are listed in different dependent claims does not mean that combinations of these means cannot be used favorably. No reference numeral in the claims should be construed as limiting the scope.

Claims

1. A light source having an input and an output, and a parallel or series configuration of a first sub-load and a second sub-load coupled between the input and the output, A first driver adapted to supply power to the input of the light source, A second driver adapted to supply power to the input of the light source, A controller adapted to receive dimming signals and to allow or deny power to be supplied to the light source by the first driver and / or the second driver based on the dimming level, A lighting device comprising a control circuit adapted to receive a control signal, the control circuit configured to operate and deactivate the first sub-load and the second sub-load based on the control signal.

2. The lighting device according to claim 1, wherein the light source has a third sub-load, the lighting device has a third driver adapted to supply power to the light source, the controller is further adapted to allow or deny power supply by the third driver, and the control circuit is further configured to operate and deactivate the third sub-load.

3. The lighting device according to claim 1 or 2, wherein the control signal is supplied by the controller.

4. The lighting device according to any one of claims 1 to 3, wherein the controller is configured to allow power from the first driver to be supplied to the light source and to refuse power from the second driver to be supplied to the light source at a first dimming level.

5. The lighting device according to claim 4, wherein the control circuit is configured to activate the first sub-load and deactivate the second sub-load.

6. The lighting device according to any one of claims 1 to 5, wherein the current supplied by the first driver corresponds to the optimal current density of the first sub-load.

7. The lighting device according to any one of claims 1 to 6, wherein the controller is configured to refuse to supply power from the first driver to the light source and to allow power from the second driver to be supplied to the light source at a second dimming level.

8. The lighting device according to claim 7, wherein the control circuit is configured to stop the operation of the first sub-load and activate the second sub-load.

9. The lighting device according to any one of claims 1 to 8, wherein the current supplied by the second driver corresponds to the optimal current density of the second sub-load.

10. The lighting device according to any one of claims 1 to 9, wherein the maximum power capacity of the first driver is substantially the same as the maximum power capacity of the second driver.

11. The lighting device according to any one of claims 1 to 9, wherein the maximum power capacity of the first driver is lower than the maximum power capacity of the second driver.

12. The lighting device according to any one of claims 1 to 11, wherein the first driver and the second driver are drivers that cannot be dimmed.

13. The lighting device according to any one of claims 1 to 12, wherein the light generated by the first sub-load is emitted on a first surface, the light generated by the second sub-load is emitted on a second surface, and the first surface does not overlap with the second surface in any part.

14. The lighting device according to any one of claims 1 to 13, wherein the light generated by the first sub-load has a different color or color temperature from the light generated by the second sub-load.

15. The first sub-load and / or the second sub-load have an LED light source.

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