Efficient dimming with multiple sub-drivers for single load

Abstract

The invention relates to a driver circuit for driving a light source. The driver circuit includes a first driver adapted to supply power to the light source, a second driver adapted to supply power to the light source, and a controller for controlling the first driver and the second driver. The controller is arranged to receive a dimming signal indicative of a dimming level of the light source, where the controller is arranged to convert the received dimming signal to a discrete number of dimming levels representative of a dimming level corresponding to an amount of power that can be provided by the first driver and / or the second driver, wherein the controller is arranged to allow or reject power flow from the first driver and / or the second driver based on the discrete dimming level.

Description

Technical Field

[0001] This invention relates to a driver. It also relates to a lighting device. Background Technology

[0002] For the lighting industry, energy efficiency requirements have become more challenging, especially with the introduction of the new EU energy efficiency labeling system on September 1, 2021. This new labeling follows the trend of increasing energy efficiency in lighting products. Consequently, more and more light sources have achieved A+ or A++ ratings, making it impossible for consumers to perceive any difference in luminous efficiency between products. With the new labeling, light sources have again become more dispersed in the labeling range. This also means that, for example, a lamp rated A++ in the old system is now labeled C. Therefore, further improvements in the energy efficiency of light sources are expected.

[0003] Especially for dimmable light sources, high efficiency is highly desirable. During dimming, and particularly deep dimming, fixed losses in the driver (e.g., losses in the control circuitry) become a major component of the losses in the lighting fixture. Drivers are typically designed for their rated power, so fixed losses also depend on the driver's rated power. Generally, drivers with lower rated output power also have lower fixed power losses. This significantly affects the total power available to the load. Drivers with higher rated power can deliver more power to their output, but this introduces more fixed losses. Therefore, it is desirable to provide a lighting fixture that offers good dimming capabilities while operating with very high efficiency. Summary of the Invention

[0004] The purpose of this invention is to provide a solution that allows dimming to be performed while maintaining good overall efficiency.

[0005] To provide such a solution, in a first aspect of the invention, a driver circuit for driving a light source is provided. The driver circuit includes:

[0006] - A first driver adapted to provide a first maximum amount of power to the light source;

[0007] - A second driver adapted to provide a second maximum power amount to the light source;

[0008] - A controller for controlling the first and second drives;

[0009] The controller is configured to receive a dimming signal indicating the dimming level of a light source, and the controller is configured to convert the received dimming signal into a discrete number of dimming levels, the discrete number of dimming levels representing dimming levels corresponding to a first maximum power amount provided by a first driver and / or a second maximum power amount provided by a second driver, wherein the controller is configured to allow or deny power flow from the first driver and / or the second driver based on the received dimming signal.

[0010] A first driver and a second driver are provided. Both drivers supply power to the same light source. A controller is used to control the first and second drivers. The controller also receives a dimming signal. The dimming signal can be any kind of dimming signal used in the lighting industry. Examples of dimming signals are phase-cut dimming signals, 0-10V dimming signals, DALI dimming signals, DMX dimming signals, or wireless dimming signals. The controller converts the received dimming signal into multiple discrete dimming levels. The discrete dimming level is an indication of the amount of power to be supplied to the light source. Based on the discrete dimming level, the controller determines which driver is allowed to supply power to the light source. Based on the discrete dimming level, the controller can decide to use the first driver, the second driver, or both the first and second drivers to supply power to the light source. Preferably, the number of discrete dimming levels is based on the number of drivers. If there are two drivers with the same rated power, there can be three discrete dimming levels. Such dimming levels could be, for example, 0%, 50%, and 100%. At 0%, the controller can decide to deny power to the light source from both drivers. At 50%, the controller can decide to allow only one driver to supply power to the light source. At 100%, the controller can decide whether to allow both drivers to power the light source. In this example, the discrete dimming level can preferably be set to the rated power of the corresponding driver. Preferably, the driver has the highest efficiency at the corresponding rated power. For example, when both the first and second drivers are arranged to provide 2W of power to the light source, a 50% discrete dimming level corresponds to 2W of power to the light source. Then, a 100% discrete dimming level can correspond to 4W of power to the light source. At any discrete dimming level, the driver circuitry can allow optimized power efficiency to be achieved.

[0011] In another example, the driver circuitry further includes a third driver, wherein a controller is arranged to control the third driver, and wherein each discrete dimming level represents a dimming level corresponding to the amount of power that can be provided by the first driver and / or the second driver and / or the third driver, wherein the controller is arranged to allow or deny power flow from the first driver and / or the second driver and / or the third driver based on the discrete dimming level.

[0012] A third driver allows for more discrete dimming steps. With three drivers, assuming all drivers have the same rated power, there can be four discrete dimming levels. Such dimming levels could be, for example, 0%, 33%, 66%, and 100%. Preferably, the driver has the highest efficiency at the corresponding rated power. For example, when the first, second, and third drivers are arranged to supply 2W of power to the light source, a 33% discrete dimming level corresponds to 2W of power to the light source. Then, a 66% discrete dimming level could correspond to 4W of power to the light source. And a 100% discrete dimming level could correspond to 6W of power to the light source. At any discrete dimming level, the driver circuitry can allow for optimized power efficiency.

[0013] In yet another example, the first and second drives are arranged to have the same rated power.

[0014] If the first and second drivers provide substantially similar amounts of power to the light source, the drivers can be designed as identical modules. This greatly simplifies the design of the driver circuitry. In this example, the number of discrete dimming steps can be based on the number of drivers used. Each additional driver allows the introduction of additional discrete dimming steps. Furthermore, there is always a 0% dimming level. In this sense, the amount of discrete dimming level can be derived from the following equation: D = 1 + N, where D is the number of discrete dimming levels and N is the number of drivers.

[0015] In another example, the first driver and the second driver are arranged to have different rated power from each other.

[0016] Using drivers with different power ratings allows for more dimming steps. With two drivers, there can be four discrete dimming levels. Additionally, different dimming steps can be provided in a non-linear manner, such as logarithmic dimming profiles.

[0017] For example, a first driver can supply 1W of power to the light source, and a second driver can supply 2W of power to the light source. This can result in dimming levels of, for example, 0%, 33%, 66%, and 100%. This would result in a discrete dimming level of 33% corresponding to 1W of power to the light source. Then, a discrete dimming level of 66% could correspond to 2W of power to the light source. Then, a discrete dimming level of 100% could correspond to 3W of power to the light source. In this sense, the amount of discrete dimming level can be derived from the following equation: Where D is the number of discrete dimming levels and N is the number of drivers. In the example with three drivers, seven combinations are possible.

[0018] In another example, between two discrete dimming steps, only one driver is arranged to provide variable power to the light source.

[0019] Preferably, between two discrete dimming steps, only one driver can supply varying power to the light source. This may mean, for example, that the first driver supplies a fixed amount of power to the light source, preferably at the first driver's rated power. Preferably, the second driver can then additionally supply power to the light source that can vary based on the dimming signal. By supplying a fixed amount of power to the light source, preferably at the rated power of the first driver with or near its highest efficiency, the first driver operates at its highest efficiency. The second driver can operate at a potentially lower efficiency. However, the overall efficiency of the driver circuitry is still improved, and the second driver allows for more dimming levels. In the example of three drivers, the first and second drivers can supply a fixed amount of power to the light source, preferably at the rated power of the first and second drivers with or near their highest efficiency. The third driver can then additionally supply power to the light source that can vary based on the dimming signal. Another example with three drivers could be that the first driver supplies a fixed amount of power to the light source, preferably at the first driver's rated power. The second driver can then additionally supply power to the light source that can vary based on the dimming signal. In this example, the third driver does not supply power to the light source. The determination of driver control as defined in the preceding examples can be based on the dimming signal and / or discrete dimming levels. Between two discrete steps, the controller can provide an additional dimming step, which allows the driver supplying variable power to the light source to change its output power according to the dimming signal.

[0020] In another example, the first driver and / or the second driver are not dimmable.

[0021] If the drivers are non-dimmable, they are arranged to provide a fixed amount of power. Therefore, the drivers can only provide one power level, which may be the driver's rated power. The drivers have optimal power efficiency because they are designed to provide that single amount of power with the highest possible efficiency. In this example, when all drivers are non-dimmable, the driver circuitry may only be able to provide a number of discrete dimming steps corresponding to the number of drivers provided.

[0022] In another example, the controller is configured to turn the first and second drivers on and off based on discrete dimming levels.

[0023] A simple way to allow and deny power from the driver to the light source is to turn the corresponding driver on and off. When the controller determines, based on the discrete dimming level, that the driver should not supply power to the light source, it turns off the corresponding driver. If the discrete dimming level increases, the controller can decide to turn the corresponding driver on. The advantage of turning off a driver is that it consumes less or no power during the off period. This significantly improves the efficiency of the corresponding driver, and thus the efficiency of the driver circuitry.

[0024] In another example, the first driver and / or the second driver are dimmable, wherein the first driver and / or the second driver are adapted to be reduced to 50% of the minimum output power. Preferably, the first driver and / or the second driver cannot be reduced below this 50% minimum output power. Below this output power level, the efficiency of the driver may begin to decrease significantly, so further reduction would have too great an impact on the efficiency of the driver circuitry.

[0025] A driver can be designed to operate at its rated power of 100% output power with optimal efficiency. If the driver deviates from this power point, its efficiency will decrease. If one or both drivers reduce their output power below 50%, the impact on the driver circuitry can become too significant and is therefore undesirable. Drivers should therefore be arranged so that the output power does not drop below 50%.

[0026] In another example, the first driver and / or the second driver are dimmable switch-mode power supplies, wherein the first driver and / or the second driver are adapted to be dimmed so that the overall efficiency of the driver circuit does not drop below 95%.

[0027] To ensure good overall efficiency of the driver circuitry, it is desirable to avoid the overall efficiency dropping below 95%. This means the driver is designed to power the light source so that the overall efficiency does not fall below 95%. This might mean, for example, disallowing driver dimming, which would cause the overall efficiency to drop below 95%. Input and output power can be measured, allowing the controller to determine the efficiency of the driver circuitry.

[0028] In another example, the driver circuit includes an auxiliary driver adapted to power the controller and adapted to be electrically isolated from the light source.

[0029] Controllers typically require their own power supply. Controllers have their own power requirements. Therefore, it is desirable to provide an auxiliary driver whose power efficiency is optimized for the power consumed by the controller. This can be accomplished when the auxiliary driver is used solely to power the controller. Preferably, the auxiliary driver is electrically decoupled from the light source, so that the auxiliary driver cannot power the light source.

[0030] In another example, the driver circuitry includes an additional auxiliary driver adapted to supply power to the controller when the driver circuitry is in standby mode.

[0031] In standby mode, the controller can consume less power than during normal operation. Preferably, good power efficiency is also provided during the standby mode of the driver circuitry. An additional auxiliary driver can optimize its power efficiency for the power consumed by the controller during standby. During standby, the controller can, for example, remain active for receiving wireless control signals.

[0032] In another example, at discrete dimming levels where the first and second drivers provide power to the lighting load, the first and second drivers operate in an interleaved operation mode.

[0033] The desired dimming level is achieved by having two drivers operate in an interleaved mode, providing power at optimized power efficiency. The controller can control the two drivers such that they operate with a relative phase delay. When using two drivers, the phase delay is preferably 180 degrees, or for any number of n drivers, the phase delay is preferably... This results in ripple in the output current, which has double the frequency but with reduced peak-to-peak amplitude.

[0034] In another example, a lighting device is provided. The lighting device includes a driver circuit and a light source according to any of the foregoing examples.

[0035] The lighting device will benefit from the driver circuit according to the invention. The lighting device can provide dimmed light output from its light source while maintaining good efficiency.

[0036] In another example, the controller is arranged to control the first and second drivers based on the dimming level, such that the effectiveness of the lighting device increases when the dimming level is reduced.

[0037] Preferably, the efficiency of the lighting device is increased. This can be achieved by disconnecting one driver when the discrete dimming level is at a level where, for example, only one driver is needed to power the light source. The light source is configured to receive current only from the first driver, while the second driver does not provide current. This means that the current supplied to the light source is smaller, resulting in a reduction in the current density in the light source. The light source has improved efficiency at the reduced current density, thus improving the efficiency of the lighting device.

[0038] In another example, the lighting load is a semiconductor lighting load, preferably an LED load, and more preferably an LED load in the form of a filament.

[0039] Preferably, the lighting load is a semiconductor lighting load. Examples of semiconductor loads are LEDs, laser diodes, and vertical cavity surface emitting lasers (VCSELs). Preferably, the LED is formed as a filament. Attached Figure Description

[0040] Examples of the invention will now be described with reference to the accompanying drawings, in which:

[0041] Figure 1 An example of a circuit diagram is shown.

[0042] Figure 2 Another example of a circuit diagram is shown.

[0043] Figure 3 The graph showing the relationship between output power and dimming level is presented.

[0044] Figure 4 Another graph showing the relationship between output power and dimming level is presented.

[0045] Figure 5 Another graph showing the relationship between output power and dimming level is presented.

[0046] Figure 6 Another graph showing the relationship between output power and dimming level is presented.

[0047] Figure 7 Another example of a circuit diagram is shown.

[0048] Figure 8 Another graph showing the relationship between output power and dimming level is presented.

[0049] Figure 9 Another graph showing the relationship between output power and dimming level is presented.

[0050] Figure 10 Another graph showing the relationship between output power and dimming level is presented.

[0051] Figure 11 Another example of a circuit diagram is shown.

[0052] Figure 12 Another example of a circuit diagram is shown.

[0053] Figure 13 An example of a light source is shown.

[0054] Figure 14 Another example of a circuit diagram is shown.

[0055] Figure 15 Another example of a circuit diagram is shown.

[0056] Figure 16 Another example of a circuit diagram is shown. Detailed Implementation

[0057] The invention will be described with reference to the accompanying drawings.

[0058] It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the apparatuses, systems, and methods, are for illustrative purposes only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the apparatuses, systems, and methods of the present invention will become more readily apparent from the following description, the appended claims, and the accompanying drawings. It should also be understood that the drawings are merely schematic and not drawn to scale. Furthermore, it should be understood that the same reference numerals are used throughout the drawings to denote the same or similar parts.

[0059] Figure 1 An example circuit diagram of a lighting device with a driver circuit that provides output power to a light source LED is shown. The driver circuit can be coupled to a power supply via a rectifier circuit with four diodes D10, D11, D12, and D13. The rectifier circuit provides a rectified power supply voltage. In the provided example, a first driver D1 and a second driver D2 receive the rectified power supply voltage. A controller C is used to control the first driver D1 and the second driver D2. The controller C can receive a dimming signal Dim. The dimming signal Dim can be provided by a dimmer or an external device that provides a dimming command. Examples of devices that can provide a dimming signal are phase-cut dimmers, 0-10V dimmers, DALI dimmers, DMX dimmers, or wireless remote devices for providing dimming signals. The first driver D1 and the second driver D2 are arranged to power the same load, which in this example is a light source LED.

[0060] The light source LED has a first input to which the output of a first driver D1 and the output of a second driver D2 are coupled. Preferably, the light source LED is an LED light source. The LED light source can be a series-coupled string of LEDs, preferably forming a filament. Other devices or combinations of devices can also be series-coupled, such as laser diodes or VCSELs. For clarity, these examples show an LED as a light source. Preferably, the size of the LED string cannot be changed. This means that the LED string has only one input for receiving current and one return current, respectively. Therefore, the forward voltage is not changed by, for example, a shunt switch that shunts a portion of the LED string. Thus, the power consumed by the light source LED is regulated by the driver that powers the light source LED, rather than by changing the size of the light source LED. The light source LED can have two parallel LED strings, preferably with approximately the same forward voltage. More details about this topology will be provided in further examples.

[0061] Controller C receives the dimming signal and uses it to provide control signals to the first driver D1 and the second driver D2. Preferably, controller C converts the dimming signal into discrete dimming levels. Controller C can make the number of discrete dimming levels based on the number of drivers provided in the driver circuit. In an example with drivers of the same rated power, the number of discrete dimming levels can be determined by the following equation: D = 1 + N, where D is the number of discrete dimming levels and N is the number of drivers. In an example with two drivers, the number of discrete dimming levels is 3. 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 then 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. Clearly, these values ​​are merely one example of how to convert a dimming signal's dimming range to a discrete dimming level, and other ranges for converting dimming signals to discrete dimming levels can be conceived. At 0% output power, the controller provides a control signal to the drivers, preventing the first driver D1 and the second driver D2 from supplying power to the LED light source. Both drivers can be disconnected. At 50% output power, the controller C provides a control signal to the drivers, allowing one driver to supply rated power to the load and preventing the other driver from supplying power to the load. At 100% output power, the controller C provides a control signal to the drivers, allowing both drivers to supply their rated power to the light source.

[0062] At all discrete dimming levels, the lighting fixture is now able to operate at the highest possible efficiency. Luminous efficiency can be further improved when fewer than the maximum number of drivers supply power to the LED light source. Since the light source has a single forward voltage, the amplitude of which cannot be altered by, for example, a portion of the series connection of the LEDs in the light source, the number of drivers supplying power to the light source determines the current density in the LEDs. Fewer drivers supplying power to the LEDs reduce the current density through the LEDs, thus increasing the luminous efficiency of the lighting fixture.

[0063] Figure 2 It shows Figure 1An example of a detailed circuit diagram of the circuit shown. In the provided example, rectifier circuits D10, D11, D12, and D13 are provided. The rectifier circuits provide a rectified voltage, which is supplied to the first driver D1 and the second driver D2. The first driver D1 and the second driver D2 are designed as a boost converter. The first driver D1 and the second driver D2 are coupled in parallel at their inputs and provide parallel power to the light source LED. 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. The diodes form freewheeling diodes for the boost converter topology, and they allow the outputs of the first driver D1 and the second driver D2 to be coupled together. In the case of another topology besides a boost converter (e.g., a buck converter), each driver may require additional diodes to allow the driver to couple at its output. Controller C provides control signals to the first driver D1 and the second driver D2. In this example, control signals can be directly provided to the gates of the first switching element M1 and the second switching element M2, respectively. Therefore, the controller C determines the power that can be delivered to the light source LED. Preferably, the controller C controls the driver such that the power supplied to the light source LED corresponds to the power required by the light source LED according to the discrete dimming level.

[0064] Figure 3This diagram illustrates the relationship between dimming level and driver circuit output power when two drivers with approximately equal rated power are provided. The dimming signal is received by controller C and interpreted as a dimming level. The controller determines a discrete dimming level based on the dimming level. In this example, three discrete dimming levels can be seen: one at 0% output power, one at 50% output power, and the last at 100% output power. In this example, controller C determines that the discrete dimming level is set to 0% output power between 0% and 33% dimming levels. Between 34% and 66% dimming levels, the discrete dimming level is set to 50%. Between 67% and 100%, the discrete dimming level is set to 100%. This means that within the dimming range of 0% to 33%, no power is supplied to the LED light source. Between the dimming levels of 34% and 66%, 50% of the output power is supplied to the LED light source. Controller C activates one driver to supply the rated power corresponding to 50% output power to the LED light source and disables the other driver from supplying power to the LED light source. Between 67% and 100% dimming levels, 100% of the output power is supplied to the LED light source. Controller C activates two drivers to provide the LED light source with their rated power, corresponding to 100% of the output power. Clearly, other relationships between dimming levels and discrete dimming levels can be derived while maintaining the same discrete dimming level.

[0065] Figure 4 The diagram shows the relationship between dimming level and the output power of the driver circuit when two drivers with different rated power 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, four discrete dimming levels can be seen: one at 0% output power, one at 25% output power, one at 75% output power, and the last at 100% output power. The number of discrete dimming levels can be derived from the equation: Where D is the number of discrete dimming levels and N is the number of drivers. For example, the first driver D1 is arranged with a rated power of 1W, and the second driver D2 is arranged with a rated power of 3W. When neither driver supplies power to the LED, the LED power is 0W, which relates to dimming levels between 0% and 24%. When only the first driver D1 supplies power to the LED at its rated power, the LED receives 1W, which corresponds to 25% of the total output power. This output power then relates to dimming levels between 25% and 50%. When only the second driver D2 supplies power to the LED at its rated power, the LED receives 3W, which corresponds to 75% of the total output power. This output power then relates to dimming levels between 51% and 75%. The total rated power of the driver circuit is 4W, which corresponds to the output power at dimming levels between 76% and 100%, where both the first driver D1 and the second driver D2 supply power to the LED at their respective rated powers.

[0066] Figure 5Another graph showing the relationship between dimming level and driver circuit output power when two drivers are provided is shown. 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 at 100% output power. In this example, the discrete dimming levels are used differently compared to the previous example. The discrete dimming levels are used to determine whether an additional driver is needed to power the light source, or whether another driver should be prevented from powering the light source. In this example, it is again assumed that the first driver D1 and the second driver D2 are arranged with substantially the same rated power. At 0%, controller C controls both drivers not to power the light source LED. At dimming levels, for example, between 0.1% and 50%, controller C controls one of the drivers to allow power to be supplied to the light source LED. If a single active driver is arranged to follow the dimming signal and therefore the dimming level, the power is not supplied at a single rated power level. For example, at a 10% dimming level, an active driver can be arranged to provide 20% of its rated output power, while at 50%, the active driver can be arranged to provide 100% of its rated output power. At 50.1%, controller C determines that a discrete dimming level has exceeded 50%. This means that between dimming levels of 50.1% and 100%, one driver provides its rated power, while the other driver additionally provides variable power. For example, at a dimming level of 60%, one driver provides 100% of its rated power, and the driver providing variable power can be arranged to provide 20% of its rated output power. At a 100% dimming level, both drivers can be arranged to provide 100% of their rated output power. Therefore, controller C determines the discrete dimming level, and between two discrete dimming levels, one driver is arranged to provide variable power to the LED light source, i.e., the power can be changed based on the dimming level, and the other driver is arranged to provide a fixed power to the LED light source, preferably at the driver's rated power.

[0067] Figure 6 It shows the relationship with Figure 5 The graph shown is similar to the graph shown. In this example, the rated power of the two drivers is carefully selected. The rated power of the drivers depends on the minimum efficiency allowed for the drivers. The drivers are allowed to provide a variable level of power from the rated power down to the power level corresponding to the minimum allowed efficiency. The first driver, D1, has its rated power at 100% power output, therefore it has a 100% to P... rated D1 The power range of *min_loading, where P ratedD1This is the rated power of the first driver D1, and `min_loading` is the minimum allowable power of the first driver D1, expressed as a percentage, where the minimum driver efficiency target is met. To provide a smooth dimming curve, the second driver D2 can provide a minimum power equal to or less than the rated power of the first driver D1. Then, through... Determine the rated power of the second driver D2, where P ratedD2 It is the rated power of the second driver D2, P ratedD1 It is the rated power of the first driver D1, and min_loading is the minimum allowable power of the second driver D2 as a percentage, where the minimum driver efficiency target is met.

[0068] As an example, the first driver D1 and the second driver D2 have a minimum permissible load of 70% while meeting the minimum driver efficiency target. The first driver D1 can have a rated power of 1.75W. Therefore, the minimum power that the first driver D1 can provide is 1.23W. The second driver D2 is then configured to provide a minimum power of 1.75W. This results in a rated power of 2.5W. The driver circuit can provide a total of 4.25W. The minimum power that can be provided by the first driver D1 (i.e., 1.23W) is located at 28.8% of the dimming range. The rated power that can be provided by the first driver D1 (i.e., 1.75W) is located at 41.2% of the dimming range. Therefore, this is also the same as the minimum power that the second driver D2 can provide. The rated power that can be provided by the second driver D2 (i.e., 2.5W) is located at 58.8% of the dimming range. The rated power of the driver circuit (i.e., 4.25W) is located at 100% of the dimming range.

[0069] The first part of the graph (solid line) represents the area where power cannot be supplied to the LED in this configuration. Controller C can then prevent both drivers from supplying power to the LED. Increasing the dimming level to 28.2% will cause controller C to activate the first driver D1, thus supplying 1.23W to the LED at 70% load. Further increasing the dimming level will allow the first driver D1 to supply more power to the LED. If the dimming level is further increased to 41.2%, the first driver D1 supplies power to the LED at its rated power, and therefore preferably at its highest efficiency. Further increasing the dimming level above 41.2% causes the second driver D2 to supply at least 1.75W of power to the 41.2% LED. In this case, the first driver D1 is prevented from supplying power to the LED. Further increasing the dimming level will allow the second driver D2 to supply more power to the LED. If the dimming level is further increased to 58.8%, the second driver D2 supplies power to the LED at its rated power, and therefore preferably at its highest efficiency. Increasing the dimming level above 58.8% will cause controller C to control both drivers to power the LED light source. In this case, to minimize the gap in the dimming range, the second driver D2 provides reduced power to the LED light source to allow the first driver D1 to also provide power to the light source. This gap may be caused by the first driver D1 being unable to provide power below 70% of the load, thus effectively resulting in a dimming range between 58.8% and 70% where no further increase in output power can be provided. Preferably, within this dimming range, the output power of the LED light source is maintained at 2.5W. When the dimming level is further increased above 70%, both drivers can begin to power the LED light source. At 70%, the two drivers can provide a minimum permissible power of 1.23W to the first driver D1 and a minimum permissible power of 1.75W to the second driver D2. The 70% power then provided to the LED light source is 2.98W. In this example, the gap in the dimming range between 58.8% and 70% involves a power gap of 2.98W - 2.5W = 0.48W. From a dimming level between 70% and 100%, the drivers increase their power to the LED to match the corresponding dimming level. This can be achieved by increasing the power of both drivers simultaneously, or by increasing the power from the first driver D1 in the first portion of the 70% to 100% dimming range and increasing the power from the second driver D2 in the second portion of the 70% to 100% dimming range. At a 100% dimming level, the first driver D1 and the second driver D2 supply their rated power to the LED. In this example, a total power of 1.75W + 2.5W = 4.25W is supplied to the LED.

[0070] To reduce any gaps in the dimming range, the first driver D1 and / or the second driver D2 can be allowed to reduce power to levels well below 70%. In the provided example, the gap in the dimming range between 58.8% and 70% can be reduced or even eliminated. In the provided example, the gap in the dimming range between 0% and 28.8% can then also be reduced or eliminated. This may result in some efficiency loss because the efficiency of the drivers can be further reduced.

[0071] Figure 7 An example circuit diagram of a lighting device with driver circuitry is shown. The driver circuitry includes additional drivers. The driver circuitry has a first driver D1, a second driver D2, and a third driver D3. In the provided example, rectifier circuits D10, D11, D12, and D13 are provided. The rectifier circuits provide a rectified voltage, which is supplied 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 provide parallel power to the light source LED. A controller C provides control signals to the first driver D1, the second driver D2, and the third driver D3. Therefore, the controller C determines the power that can be delivered to the light source LED. Preferably, the controller C controls the drivers such that the power supplied to the light source LED corresponds to the power required by the light source LED according to a discrete dimming level.

[0072] Figure 8 An example graph showing the relationship between dimming level and the output power of the driver circuit when three drivers are provided is shown. In this example, it is assumed that the drivers have approximately the same rated power. In this example, four discrete dimming levels are obtained: 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 LED. At dimming levels between 25% and 50%, the discrete dimming level is set to 33.33%, causing controller C to control one driver to supply power to the LED at the power corresponding to that driver's rated power. This results in 33% of the total power that can be provided by the driver circuit being supplied to the LED. At dimming levels between 26% and 75%, the discrete dimming level is set to 66.67%, causing controller C to control two of the three drivers to supply power to the LED at the respective rated power of the drivers. This results in 66.67% of the total power that can be provided by the driver circuit being supplied to the LED. At dimming levels between 76% and 100%, the discrete dimming level is set to 100%, causing controller C to control all drivers to supply power to the LED light source at the corresponding rated power of the drivers. This results in 100% of the total power available from the driver circuitry being supplied to the LED light source.

[0073] Figure 9 Another example of a graph showing the relationship between dimming level and driver circuit output power when three drivers are provided is shown. In this example, it is assumed that the drivers have different rated power. In this example, seven discrete dimming levels are obtained: 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 at 100% output power. As an example, the first driver D1 can have a rated power of 1W, the second driver D2 can have a rated power of 2W, and the third driver D3 can have a rated power of 5W, resulting in the driver circuit being able to provide a maximum power of 8W. 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 LED. At dimming levels between 14.4% and 28.6%, the discrete dimming level is set to 12.5%, resulting in power being supplied to the light source LED only by the first driver D1 at its rated power. At dimming levels between 28.7% and 42.9%, the discrete dimming level is set to 25%, resulting in power being supplied to the LED light source only by the second driver D2 at its rated power. At dimming levels between 43% and 57.1%, the discrete dimming level is set to 37.5%, resulting in power being supplied to the LED light source only by the first driver D1 and the second driver D2 at their rated power. At dimming levels between 57.2% and 71.4%, the discrete dimming level is set to 75%, resulting in power being supplied to the LED light source only by the first driver D1 and the third driver D3 at their rated power. At dimming levels between 71.5% and 85.7%, the discrete dimming level is set to 87.5%, resulting in power being supplied to the LED light source only by the second driver D2 and the third driver D3 at their rated power. At dimming levels between 85.8% and 100%, the discrete dimming level is set to 100%, resulting in the first driver D1, the second driver D2, and the third driver D3 supplying power to the LED light source at their rated powers. Changing the rated power of the drivers will result in different distributions of the discrete dimming level.

[0074] Figure 10Another graph showing the relationship between dimming level and driver circuit output power when three drivers are provided is shown. 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 four discrete dimming levels: one at 0% output power, one at 33.3% output power, one at 66.67% output power, and the last at 100% output power. In this example, discrete dimming levels are used differently compared to the previous example. Discrete dimming levels are used to determine whether an additional driver is needed to power the light source, or whether another driver should be prevented from powering the light source. In this example, it is again assumed that the first driver D1, the second driver D2, and the third driver D3 are arranged with substantially the same rated power. At 0%, controller C controls all drivers to not power the light source LED. At dimming levels between 1% and 33.33%, controller C controls one of the drivers to allow power to be supplied to the light source LED. For example, at a dimming level of 11.11%, the active driver can be arranged to provide 33.33% of the driver's rated power, and at a dimming level of 33.33%, the active driver can be arranged to provide 100% of the driver's rated power. At a dimming level of 33.34%, controller C determines that a discrete dimming level of 33.33% has been exceeded. This means that between dimming levels of 33.34% and 66.67%, one driver provides the driver's rated power, while another driver additionally provides variable power. At a dimming level of 66.68%, controller C determines that a discrete dimming level of 66.67% has been exceeded. This means that between dimming levels of 66.68% and 100%, two drivers provide the driver's rated power, and a third driver additionally provides variable power.

[0075] As an example, at a dimming level of 77.78%, both drivers provide 100% of their rated power, and the driver providing variable power can be arranged to provide 33.33% of its rated output power. At a dimming level of 100%, all drivers can be arranged to provide 100% of their rated output power. Therefore, controller C determines discrete dimming levels, and between two discrete dimming levels, one driver is arranged to provide power to the LED light source, which can be variable—that is, the power can be changed based on the dimming level—and another driver, or both drivers, are arranged to provide their respective rated power to the LED light source, depending on the absolute dimming level.

[0076] Figure 11Another example of a driver circuit is shown. In this example, rectifier circuits D10, D11, D12, and D13 are provided. The rectifier circuits provide a rectified voltage, which is supplied to a first driver D1 and a second driver D2. The first driver D1 and the second driver D2 are coupled in parallel at their inputs and provide parallel power to the light source LED. A controller C provides control signals to the first driver D1 and the second driver D2. The controller C can, for example, provide an enable or disable signal to each of the drivers. The controller C can receive a dimming signal Dim. The dimming signal Dim can be provided by a dimmer or an external device that provides a dimming command. Examples of devices that can provide a dimming signal are phase-cut dimmers, 0-10V dimmers, DALI dimmers, DMX dimmers, or wireless remote devices for providing dimming signals. The first driver D1 and the second driver D2 are arranged to power the same load, which in this example is the light source LED. The first driver D1 provides rated power to the light source LED at the optimal power conversion rate. Therefore, the first driver D1 provides a first output power at a first optimal power conversion rate. The second driver D2 provides rated power to the LED light source at an optimal power conversion rate. Therefore, the second driver D2 provides a second output power at a second optimal power conversion rate. When the two drivers are arranged to provide the same amount of power, the first and second output powers can be the same, and therefore the first and second optimal conversion rates can also be the same. The controller C can control the on-time of the first driver D1 and the second driver D2 with a predefined duty cycle. The duty cycle of the on-time can be determined based on the received dimming signal. The controller C converts the dimming signal into a dimming level. Based on the dimming level, the desired output power to the LED light source is required. By providing a first duty cycle for the on-time of the first driver D1 and a second duty cycle for the on-time of the second driver D2, the controller C can adjust the power to be supplied to the LED light source.

[0077] For example, at a 0% dimming level, both drivers are off. Increasing the dimming level increases the on-time of the first driver D1 until it has an on-time with a 100% duty cycle. This can happen at a 50% dimming level. At a 50% dimming level, the first driver D1 provides its rated power for 100% of the time. Further increasing the dimming level causes the controller to activate both the first driver D1 and the second driver D2. As an example, the first driver D1 could be a controller with a 100% on-time across the entire range from 50% to 100%. Then, as the dimming level increases, the second driver D2 is controlled with an increasing on-time. When the dimming level is 100%, both the first driver D1 and the second driver D2 are controlled to operate with an on-time of 100% duty cycle. Effectively, both drivers continuously power the LED light source at their rated power.

[0078] As another example, the rated power of the first driver D1 may be different from the rated power of the second driver D2.

[0079] For example, the first driver D1 can have a rated power of 2W. The second driver D2 can have a rated power of 4W. Therefore, the maximum total power that can be supplied to the LED light source by the driver circuit is 6W. When the dimming level is set to 50%, 3W of output power may be required. Then, the controller C can provide a first duty cycle of 100% for the first driver D1 and a second duty cycle of 25% for the second driver D2. The first driver D1 provides 2W, the second driver D2 provides 1W, providing a total of 3W to the LED light source. Another way to provide 3W of power is to provide a first duty cycle of 0% for the first driver D1 and a second duty cycle of 50% for the second driver D2. The first driver D1 provides 0W to the LED light source, and the second driver D2 provides 3W. Clearly, these examples form a series of many combinations of duty cycles that can be used to achieve the desired output power of the driver circuit.

[0080] When the first driver D1 and / or the second driver D2 are arranged to supply power to the light source, this is done at the rated power level. Therefore, power is supplied to the light source with high efficiency. The inventors recognized that, to achieve maximum efficiency, the driver should supply power to the load at a single rated power level. Deviating from this power level results in reduced efficiency. A duty cycle that supplies rated power to the load allows less power to be supplied to the load while maintaining high efficiency.

[0081] Figure 12 Here is another example of a driver circuit. A driver circuit can be similar to... Figure 11The driver circuit is shown. In this example, rectifier circuits D10, D11, D12, and D13 are provided. The rectifier circuits provide a rectified voltage, which is supplied to the first driver D1 and the second driver D2. The first driver D1 and the second driver D2 are coupled in parallel at their inputs and provide parallel power to the light source LED. Controller C provides control signals to the first driver D1 and the second driver D2. Controller C may, for example, provide an enable signal to each of the drivers. Controller C may receive a dimming signal Dim. The dimming signal Dim may be provided by a dimmer or an external device that provides a dimming command. Examples of devices that can provide a dimming signal are phase-cut dimmers, 0-10V dimmers, DALI dimmers, DMX dimmers, or wireless remote devices for providing dimming signals. The first driver D1 and the second driver D2 are arranged to power the same load, which in this example is the light source LED. The first driver D1 provides rated power to the light source at an optimal power conversion rate. Therefore, the first driver D1 provides a first output power at a first optimal power conversion rate. The second driver D2 provides rated power to the light source at the optimal power conversion rate. Therefore, the second driver D2 provides a second output power at a second optimal power conversion rate. When both drivers are designed to provide the same amount of power, the first and second output powers can be the same, and therefore the first and second optimal conversion rates can also be the same. The controller C can control the on-time of the first driver D1 and the second driver D2 with a predefined duty cycle. The duty cycle of the on-time can be determined based on the received dimming signal. The controller C converts the dimming signal into a dimming level. Based on the dimming level, the desired output power is required. By providing a first duty cycle for the on-time of the first driver D1 and a second duty cycle for the on-time of the second driver D2, the controller C can adjust the power to be supplied to the light source LED.

[0082] Preferably, pulse width modulation (PWM) is used to control the on-time. The frequency of the PWM signal is higher than the frequency perceptible to the human eye, for example, 200 Hz. More preferably, the frequency is higher than 1 kHz. A filter capacitor may be connected in parallel with the LED to smooth the current through the LED load.

[0083] When the first driver D1 and / or the second driver D2 are arranged to supply power to the light source, this is done at the rated power level. Therefore, the light source is powered with high efficiency. The inventors recognized that, to achieve maximum efficiency, the driver should supply power to the load at a single rated power level. Deviating from this power level results in reduced efficiency. A duty cycle that supplies rated power to the load allows less power to be supplied to the load while maintaining high efficiency.

[0084] A series configuration of a buffer capacitor C1 and a switch J1 can be provided at the output of rectifier circuits D10, D11, D12, and D13. This switch is shown as a simple controllable switching element, but additional circuitry can be provided to perform the desired function: controlling the current flow through the buffer capacitor C1. This means that a switching device with one or more switching elements and a control circuit system can be used instead of the switch. Switch J1 can be controlled by a controller C. Switch J1 is used to regulate the current through the buffer capacitor C1. This allows the buffer capacitor C1 to be charged and discharged in a controlled manner. Using duty cycle control to control the driver may cause interference at the input of the driver circuit because there are moments when the driver does not draw current from the power supply. When any driver is not drawing current or is not drawing enough current, the buffer capacitor C1 can be used to draw current from the power supply. This allows the current from the power supply to become smooth. Preferably, the controller C controls the switch J1 and the driver such that the driver circuit provides power factor correction. This means that the current drawn from the power supply follows the waveform of the voltage. The power supply voltage can be, for example, a sinusoidal voltage with a frequency of 50Hz or 60Hz. Therefore, the current waveform follows the voltage waveform in phase. This can also be achieved by setting a common input PFC (Power Factor Correction) stage between the rectifier and drivers D1 and D2. The common PFC stage draws a sinusoidal current from the power supply, and a buffer capacitor placed at the output of the PFC stage acts as a buffer for the pulsating current drawn by drivers D1 and D2.

[0085] Figure 13An example circuit diagram is shown, in which an improved light source LED is provided, which can operate with the driver circuit provided in the example. The light source LED receives power from the driver circuit. The light source LED has a first LED load LED1 and a second LED load LED2. The first LED load LED1 and the second LED load LED2 are coupled in parallel. Preferably, the first LED load LED1 and the second LED load LED2 have approximately the same forward voltage. Preferably, the first LED load LED1 and the second LED load LED2 are configured as filaments. The first LED load LED1 and the second LED load LED2 are shown as single LEDs, but more LEDs can be coupled in series to form an LED string or filament. A first series switch M10 is configured in series with the first LED load LED1. A second series switch M11 is configured in series with the second LED load LED2. A control circuit 1 is used to control the first series switch M10 and the second series switch M11. The control circuit is arranged to sense parameters of the voltage or current supplied by the driver circuit. Examples of parameters may be the frequency, duty cycle, or amplitude of the voltage or current. The control circuit 1 uses these parameters to determine how to control the first series switch M10 and the second series switch M11. For example, frequency modulation of the voltage or current supplied by the drive circuit can provide information to control circuit 1 to determine which series switch to control. For instance, 1kHz frequency modulation can provide control circuit 1 with an indication to close the first series switch M10 and open the second series switch M11, while 2kHz modulation can open the first series switch M10 and close the second series switch M11, and 3kHz modulation can close both. As another example, similar control can be provided by changing the amplitude of the voltage or current supplied by the driver circuit. Changes in voltage or current can alter the control of the first and second series switches M10 and M11. The advantage of controlling the LED configuration according to the above example is that power and data can be sent from the driver circuit to the light source using only two wires. This is particularly beneficial when the LED is designed as a filament in a bulb, such as a reconfigurable bulb with, for example, a screw or bayonet base. In this case, the number of wires that can be supplied via a lever may be limited. The dimming technique provided in the example allows for easy dimming of the filament, while control circuit 1 allows for the distribution of the supplied power between the filaments. Preferably, the first LED load LED1 and the second LED load LED2 have different colors or color temperatures. Preferably, the first LED load LED1 has a warm color temperature, and the second LED load LED2 has a cool color temperature. Therefore, this parameter can be used to allow the control circuit 1 to adjust the color or color temperature emitted by the light source LEDs.The opening and closing of the first series switch M10 and the second series switch M11 can be a time-continuous process, wherein either the first series switch M10 is closed or the second series switch M11 is closed, and each switch has its own duty cycle, such as PWM control. Preferably, the switching process is performed at a frequency higher than 100Hz, more preferably higher than 2kHz. Alternatively, to provide simple control of the control circuit 1, the opening and closing of the first series switch M10 and the second series switch M11 can be a single event, such as when the lighting device is activated. During operation, the open or closed state of the first series switch M10 and the second series switch M11 can be changed by different commands, such as commands for changing color or color temperature.

[0086] Figure 14A circuit diagram of a lighting device with a simpler example of an improved light source LED is shown, which can operate with the driver circuit provided in the example. The light source LED receives power from the driver circuit. The light source LED has a first LED load LED1 and a second LED load LED2. The first LED load LED1 and the second LED load LED2 are coupled in parallel. Preferably, the forward voltage of the first LED load LED1 is lower than the forward voltage of the second LED load LED2. Preferably, the first LED load LED1 and the second LED load LED2 are configured as filaments. The first LED load LED1 and the second LED load LED2 are shown as single LEDs, but more LEDs can be coupled in series to form an LED string or filament. A first series switch M10 is configured to be connected in series with the first LED load LED1. A control circuit 1 is arranged to control the first series switch M10. The control circuit is arranged to sense parameters of the voltage or current supplied by the driver circuit. Examples of parameters may be the frequency, duty cycle, or amplitude of the voltage or current. The control circuit 1 uses these parameters to determine how to control the first series switch M10. For example, frequency modulation of the voltage or current supplied by the driver circuit can provide information for the control circuit 1 to control the first series switch M10. For example, frequency modulation can provide control circuit 1 with an indication to close the first series switch M10, while no modulation can provide control circuit 1 with an indication to open the first series switch M10. When the first series switch M10 is open, the current supplied by the drive circuit can only flow through the second LED load LED2. When the first series switch M10 is open, the current supplied by the drive circuit can flow through the first LED load LED1. When the forward voltage of the first LED load LED1 is approximately the same as the forward voltage of the second LED load LED2, closing the first series switch M10 will allow current to flow through both the first LED load LED1 and the second LED load LED2. If the forward voltage of the first LED load LED1 is lower than the forward voltage of the second LED load LED2, the current will only flow through the first LED load LED1. As another example, similar control can be provided by changing the amplitude of the voltage or current supplied by the driver circuit. Changes in voltage can alter the control of the first series switch M10. The advantage of controlling the LED configuration according to the example above is that power and data can be sent from the driver circuit to the light source using only two wires. This is particularly beneficial when the LED is designed as a filament in a light bulb, such as a reconfigurable bulb with a screw or bayonet base. In this case, the number of wires that can be provided by the rod may be limited. The dimming technique provided in the example allows for easy dimming of the filament, while the control circuit 1 allows for the distribution of the supplied power between the filaments. Preferably, the first LED load LED1 and the second LED load LED2 have different colors or color temperatures from each other.Preferably, the first LED load LED1 has a warm color temperature, and the second LED load LED2 has a cool color temperature. Therefore, this parameter can be used to allow the control circuit 1 to adjust the color or color temperature emitted by the light source LEDs. The opening and closing of the first series switch M10 can be a time-continuous process, wherein the first series switch M10 opens or closes with a duty cycle controlled, for example, by PWM. Preferably, this switching process is performed at a frequency higher than 100Hz, more preferably higher than 2kHz. Alternatively, to provide simple control of the control circuit 1, the opening and closing of the first series switch M10 can be a single event, such as when the lighting device is started. During operation, the open or closed state of the first series switch M10 can be changed by different commands, such as commands for changing the color or color temperature.

[0087] Figure 15 A circuit diagram of a lighting device with an improved LED light source, shown as another simple example, is illustrated. This LED light source can operate with the driver circuit provided in the example. The LED light source receives power from the driver circuit. The LED light source has a first LED load LED1 and a second LED load LED2. The first LED load LED1 and the second LED load LED2 are coupled in parallel. Preferably, the forward voltage of the first LED load LED1 is higher than the forward voltage of the second LED load LED2. A resistor R1 is placed in series with the second LED load LED2. The driver circuit provided in the example provides a current that can vary based on the amount of power supplied by the driver to the light source. At relatively low currents, all current will flow through the second LED load LED2 and the resistor R1. The sum of the forward voltage of the second LED load LED2 and the voltage drop across resistor R1 is lower than the forward voltage of the first LED load LED1. If the current increases, the forward voltage of the second LED load LED2 will increase only slightly, but a more significant voltage drop will occur across resistor R1. Further increasing the current to the light source LED will cause the sum of the forward voltage of the second LED load LED2 and the voltage drop across resistor R1 to increase until this sum reaches or exceeds the forward voltage of the first LED load LED1. Under this increased current, the first LED load LED1 will also begin to conduct. Therefore, increasing or decreasing the current to the light source allows for a simple distribution of the current through the first LED load LED1 and the second LED load LED2. Preferably, the first LED load LED1 is a cool white LED load, and the second LED load LED2 is a warm white LED load. At low currents, primarily the warm white LEDs are active, while with increased currents, the cool white LEDs also become active. This allows for a very simple mimicry of a dimmable incandescent filament or halogen lamp. Figure 13 and 14Compared to the example provided, this circuit does not require control circuit 1, although resistor R1 may generate additional power loss.

[0088] Figure 16Another example of a lighting device is shown. In the provided example, rectifier circuits D10, D11, D12, and D13 are provided. The rectifier circuits provide a rectified voltage, which is supplied to a first driver D1 and a second driver D2. The first driver D1 provides regulated power to a first light source LED1. The second driver D2 provides regulated power to a second light source LED2. A controller C is used to control the first driver D1 and the second driver D2. The controller C can receive a dimming signal Dim. The dimming signal Dim can be provided by a dimmer or an external device that provides a dimming command. Examples of devices that can provide a dimming signal are phase-cut dimmers, 0-10V dimmers, DALI dimmers, DMX dimmers, or wireless remote devices for providing dimming signals. The first driver D1 is arranged to provide a regulated current to the first light source LED1. The current amplitude is set to a value that matches the current density through the first light source LED1, which allows for optimal conversion of electrical energy into photonic energy. The LED has an optimal current density, at which the electrical power supplied to the LED is converted into light in the most efficient manner. Therefore, LEDs have the highest efficiency at their optimal current density. For example, by increasing the current amplitude through the LED, increasing the current density in the LED from the optimal current density, the light output will increase, but the luminous efficiency will decrease. For example, by decreasing the current amplitude through the LED, decreasing the current density in the LED from the optimal current density, the light output will decrease, and the luminous efficiency will also decrease. Therefore, it is desirable to allow the driver to provide a current to the LED load corresponding to the LED's optimal current density. The first driver D1 provides a current that allows the current density in the first light source LED1 to approach the optimal current density. The closer the current density is to the optimal current density, the more efficient the first light source LED1 becomes. The second driver D2 provides a current that allows the current density in the second light source LED2 to approach the optimal current density. The closer the current density is to the optimal current density, the more efficient the second light source LED2 becomes. To further optimize the efficiency of the lighting device, the driver is optimized to provide a current that allows the light source to operate at its optimized current density. The optimized current density as a light source for the LED is considered a value, and therefore it is desirable to provide a fixed current to the light source. The fixed current can be changed to compensate for variations in the optimal current density value. For example, the optimal current density can be changed based on the temperature or lifetime of the light source. By optimizing the driver design to achieve the required current density, the driver operates at its highest efficiency, and the light source provides light at its highest efficiency. Therefore, the first driver D1 is adapted to supply current to the first light source LED1 at its rated power level, and the second driver D2 is adapted to supply current to the second light source LED2 at its rated power level. The first light source LED1 and the second light source LED2 can have different dimensions. The forward voltage and / or required current of the first light source LED1 are therefore different from those of the second light source LED2.Alternatively, the first light source LED1 and the second light source LED2 can have the same electrical characteristics. If the controller C receives a dimming signal, it can decide to activate multiple drivers based on the dimming level. At, for example, a 50% dimming level, the controller can then decide to activate one of the drivers, thus activating one of the light sources. For example, the first driver D1 can supply current to the first light source LED1 at its rated power level, while the second driver D2 can supply no current to the second light source LED2. This allows the lighting fixture to provide 50% of the possible light that can still be generated with very high efficiency. Similar to other examples, having more drivers with a combination of light sources can allow for the introduction of more dimming steps while operating the lighting fixture at the highest possible efficiency.

[0089] In the provided example, controller C and additional peripheral electrical components can also be powered using a dedicated power supply. An auxiliary power supply can be provided to power controller C. Preferably, the auxiliary power supply is electrically isolated from the LED light source. Therefore, the auxiliary power supply is a dedicated power supply for controller C. The auxiliary power supply cannot provide power to the LED light source, and thus can be optimized for powering controller C.

[0090] During the standby mode of the lighting fixture, no power is supplied to the LED light source, so the driver can be disconnected. However, the controller C can be required to operate in standby mode to, for example, receive control commands to activate the lighting fixture. The controller C thus requires less power than during the operating mode of the lighting fixture. An additional auxiliary power supply can be provided to power the controller C and peripheral electrical components during standby. Additional auxiliary equipment is optimized for powering the controller C in standby mode.

[0091] Under the definition of rated power, it can be understood that the driver has a defined power capability. At this power capability, the driver supplies power to the LED light source in the most efficient manner. The driver design is then optimized to allow for maximum efficiency at this rated power level. Rated power can be the maximum power the driver can provide. Alternatively, rated power can be below the maximum power level. When the driver provides power different from its rated power, such as above or below the rated power, the driver's efficiency will decrease. Therefore, to achieve maximum efficiency, it is desirable for the driver to operate at its rated power whenever it is needed to power the LED light source.

[0092] In the provided example, the drive can be a separate device with separate components. To improve space and component utilization, some components can be reused among the drives.

[0093] In the example provided, the dimming level is linearly related to the power required by the LED light source. Other relationships, such as logarithmic or nonlinear relationships, are also conceivable and lead to the desired effect.

[0094] In the provided example, for simplicity, the discrete dimming levels are uniformly distributed across the entire dimming range. It should be understood that this is merely one option for converting dimming levels into discrete dimming steps. Alternatively, the discrete dimming steps could be distributed such that more discrete dimming steps are provided in the low-modulation photon range than in the high-modulation photon range, or vice versa.

[0095] At dimming levels, it should be understood how much power the driver circuitry needs to provide to the load. At a 100% dimming level, it is desirable for the driver circuitry to provide 100% of its rated power. At a 0% dimming level, it is desirable for the driver circuitry to provide 0% of its rated power. Dimming levels between 100% and 0% can be linearly or non-linearly proportional to the rated power of the driver circuitry. In linear scaling, a 50% dimming level can be associated with 50% of the rated power of the driver circuitry. In non-linear scaling, a 50% dimming level can, for example, be associated with 25% of the rated power of the driver circuitry.

[0096] The provided examples 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 the dimming steps can be provided.

[0097] The driver can be provided as a switch-mode power supply. Examples of switch-mode power supplies are boost converters, buck converters, buck-boost converters, flyback converters, or resonant converters.

[0098] In the context of a dimmable driver, the definition of dimmable should be understood according to general practice. A dimmable driver is capable of receiving dimming signals such as 0-10V, wireless dimming commands, or phase-cut dimming signals. A non-dimmable driver may not be able to receive any dimming signals and therefore always provides a fixed output current and / or voltage. A dimmable driver allows the light source to dim because lower power supplied to the light source will result in lower light output.

[0099] The light source LED can be considered as a single light source LED with input and return. Both drivers provide power to the input and return.

[0100] By studying the accompanying drawings, the disclosure, and the appended claims, those skilled in the art can understand and implement other variations of the disclosed embodiments in practicing the claimed invention. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude a plurality. The fact that certain measures are recited in mutually different dependent claims does not imply that combinations of these measures cannot be advantageously used. Any reference numerals in the claims should not be construed as limiting the scope.

Claims

1. A driver circuit for driving a light source (LED), the driver circuit comprising: - A first driver (D1) adapted to provide a first maximum power to the light source (LED); - A second driver (D2) adapted to provide a second maximum power to the light source (LED); - Controller (C) for controlling the first driver (D1) and the second driver (D2); The controller (C) is configured to receive a dimming signal indicating the dimming level of the light source (LED). The controller (C) is arranged to convert the received dimming signal into a plurality of discrete dimming levels, the plurality of discrete dimming levels representing dimming levels corresponding to a first maximum power provided by the first driver (D1) and / or a second maximum power provided by the second driver (D2), wherein the controller (C) is arranged to allow or deny power flow from the first driver (D1) and / or the second driver (D2) based on the received dimming signal.

2. The driver circuit of claim 1, further comprising a third driver (D3), wherein the controller (C) is arranged to control the third driver (D3), and wherein each discrete dimming level represents a dimming level corresponding to the amount of power that the first driver (D1) and / or the second driver (D2) and / or the third driver (D3) can provide, wherein the controller (C) is arranged to allow or deny power flow from the first driver (D1) and / or the second driver (D2) and / or the third driver (D3) based on the received dimming signal.

3. The driver circuit according to any one of the preceding claims, wherein the first driver (D1) and the second driver (D2) are arranged to have the same rated power.

4. The driver circuit according to claim 1 or 2, wherein the first driver (D1) and the second driver (D2) are arranged to have different rated power from each other.

5. The driver circuit according to any one of the preceding claims, wherein between two discrete dimming steps, only one driver is arranged to provide variable power to the light source based on the dimming signal.

6. The driver circuit according to any one of the preceding claims, wherein the first driver (D1) and / or the second driver (D2) is not dimming.

7. The driver circuit according to any one of the preceding claims, wherein the controller (C) is configured to turn the first driver (D1) and the second driver (D2) on and off based on the discrete dimming level.

8. The driver circuit according to any one of the preceding claims, wherein the first driver (D1) and / or the second driver (D2) is dimmable, wherein the first driver (D1) and / or the second driver (D2) is adapted to be reduced to a minimum output power of 50%.

9. The driver circuit according to any one of the preceding claims, wherein the first driver (D1) and / or the second driver (D2) are dimmable switch mode power supplies, wherein the first driver (D1) and / or the second driver (D2) are adapted to be turned down such that the overall efficiency of the driver circuit does not drop below 95%.

10. The driver circuit according to any one of the preceding claims further includes an auxiliary driver, the auxiliary driver being adapted to power the controller (C) and to be electrically disconnected from the light source (LED).

11. The driver circuit according to any one of the preceding claims further includes an additional auxiliary driver, wherein the additional auxiliary driver is adapted to supply power to the controller (C) when the driver circuit is in standby mode.

12. The driver circuit according to any one of the preceding claims, wherein the first driver (D1) and the second driver (D2) operate in an interleaved operation mode at discrete dimming levels in which the first driver (D1) and the second driver (D2) supply power to the lighting load.

13. A lighting device, comprising: - The driver circuit according to any one of the preceding claims; as well as - Light source (LED).

14. The lighting device according to any one of claims 12 or 13, wherein the lighting load (LED) is a semiconductor lighting load, preferably an LED load, and more preferably an LED load in the form of a filament.

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