High-efficiency dimming using multiple sub-drivers for a single load

Abstract

The present invention relates to a driver circuit for driving a light source. The driver circuit includes a first driver adapted to provide power to the light source, a second driver adapted to provide power to the light source, and a controller for controlling the first and second drivers. The controller is configured to receive a dimming signal indicating a dimming level for the light source, and is configured to convert the received dimming signal into a plurality of discrete dimming levels representing dimming levels corresponding to the amount of power that can be provided by the first and / or second drivers, and is configured to allow or deny power to flow from the first and / or second drivers based on the discrete dimming levels.

Description

Technical Field

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

Background Art

[0002] For the lighting industry, the requirements for energy efficiency have become more stringent, especially with the new EU energy labelling introduced on September 1, 2021. This new labelling is in line with the trend of improving the energy efficiency of lighting products. Until then, more and more light sources had achieved A+ or A++ label evaluations, making it impossible for customers to recognize the difference in luminous efficiency between products. With the new labelling, light sources have become more dispersed across the labelling range again. This also means that, for example, a lamp that 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. In dimming, especially deep dimming, fixed losses in the driver, such as losses occurring in the control circuit, become a major part of the losses in the lighting device. Drivers are generally designed for rated power, and therefore, the fixed losses also depend on the rated power of the driver. Generally, a driver with a low rated output power also has a low fixed power loss. This clearly affects the total amount of electric power that can be provided to the load. A driver with a high rated power can provide more power to its output, but this is accompanied by more fixed losses. Therefore, it is desired to provide a lighting device that can operate with very high efficiency while providing a good dimming function.

Summary of the Invention

Problems to be Solved by the Invention

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

[0005] To provide such a solution, a first aspect of the present invention provides a driver circuit for driving a light source. The driver circuit is A first driver adapted to provide a first maximum amount of power to a light source, A second driver adapted to provide a second maximum amount of power to the light source, A controller for controlling the first driver and the second driver, Includes, The controller is configured to receive dimming signals indicating the dimming level for the light source. The controller is configured to convert the received dimming signal into a plurality of discrete dimming levels representing dimming levels corresponding to a first maximum amount of power provided by a first driver and / or a second maximum amount of power provided by a second driver, and the controller is configured to allow or deny power from flowing from the first driver and / or the second driver based on the received dimming signal.

[0006] 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 driver and the second driver. The controller also receives a dimming signal. The dimming signal may be any type of dimming signal used in the lighting industry. Examples of dimming signals include phase-cut dimming signals, 0-10V dimming signals, DALI dimming signals, DMX dimming signals, or wireless dimming signals. The controller converts the received dimming signal into a plurality of discrete dimming levels. A discrete dimming level is an indication of the amount of power that should be supplied to the light source. Based on the discrete dimming levels, the controller determines which driver is permitted to supply power to the light source. Based on the discrete dimming levels, the controller may decide to supply power to the light source using the first driver, the second driver, or both the first and second drivers. Preferably, the number of discrete dimming levels is based on the number of drivers. If there are two drivers, and both drivers have the same power rating, there may be three discrete dimming levels. In this case, such dimming levels may be, for example, 0%, 50%, and 100%. At 0%, the controller may decide not to allow both drivers to supply power to the light source. At 50%, the controller may decide to allow only one of these drivers to supply power to the light source. At 100%, the controller may decide to allow both drivers to supply power to the light source. In this example, it may be preferable that the discrete dimming levels be set to the power ratings of the corresponding drivers. Preferably, the drivers have the highest efficiency at the corresponding power ratings. For example, if both the first and second drivers are configured to supply 2W of power to the light source, the 50% discrete dimming level corresponds to 2W of power to the light source. In this case, the 100% discrete dimming level may correspond to 4W of power to the light source. At any of the discrete dimming levels, the driver circuit may enable optimized power efficiency to be achieved.

[0007] In a further example, the driver circuit further includes a third driver, and the controller is configured to control the third driver, with each discrete dimming level representing a dimming level corresponding to the amount of power that can be supplied by the first driver and / or the second driver and / or the third driver, and the controller is configured to allow or deny power to flow from the first driver and / or the second driver and / or the third driver based on the discrete dimming level.

[0008] A third driver allows for the provision of more discrete dimming steps. If there are three drivers, there may be four discrete dimming levels if all drivers have the same power rating. In this case, such dimming levels may be, for example, 0%, 33%, 66%, and 100%. Preferably, the driver has the highest efficiency at the corresponding power rating. For example, if the first, second, and third drivers are configured to supply 2W of power to the light source, then the 33% discrete dimming level corresponds to 2W of power to the light source. In this case, the 66% discrete dimming level may correspond to 4W of power to the light source. In this case, the 100% discrete dimming level may correspond to 6W of power to the light source. At any of the discrete dimming levels, the driver circuit may allow optimized power efficiency to be achieved.

[0009] In a further example, the first driver and the second driver are configured to have the same power rating.

[0010] If the first and second drivers provide substantially similar amounts of power to the light source, the drivers may be designed as identical modules. This greatly simplifies the design of the driver circuit. In this example, the number of discrete dimming steps may be based on the number of drivers used. Each additional driver allows for the introduction of additional discrete dimming steps. Furthermore, a 0% dimming level always exists. From this perspective, the number of discrete dimming levels may 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.

[0011] In a further example, the first driver and the second driver are configured to have different power ratings.

[0012] Using drivers with different power ratings allows for the provision of more dimming steps. With two drivers, there may be four discrete dimming levels. Furthermore, different dimming steps can be provided non-linearly, for example, via a logarithmic dimming curve.

[0013] For example, the first driver may supply 1W of power to the light source, and the second driver may supply 2W of power to the light source. As a result, dimming levels of, for example, 0%, 33%, 66%, and 100% can be obtained. In this case, a discrete dimming level of 33% corresponds to supplying 1W of power to the light source. In this case, a discrete dimming level of 66% may correspond to supplying 2W of power to the light source. In this case, a discrete dimming level of 100% may correspond to supplying 3W of power to the light source. From this perspective, the quantity of discrete dimming levels may also be derived from the following formula: D = N(N+1) / 2 + 1, where D is the number of discrete dimming levels and N is the number of drivers. In the example of three drivers, seven combinations are possible.

[0014] In a further example, between two discrete dimming steps, only one driver is configured to provide variable power to the light source.

[0015] Preferably, between two discrete dimming steps, only one driver may provide variable power to the light source. This may mean, for example, that a first driver provides a fixed amount of power to the light source, preferably at the first driver's rated power. Preferably, a second driver may additionally provide power to the light source that can vary based on the dimming signal. Preferably, the first driver operates at maximum efficiency by providing a fixed amount of power to the light source at maximum or near-maximum efficiency at the first driver's rated power. The second driver may operate at lower efficiency. However, the overall efficiency of the driver circuit is still improved while the second driver allows for more dimming levels. In the example of three drivers, the first and second drivers may provide a fixed amount of power to the light source, preferably at maximum or near-maximum efficiency at the first and second drivers' rated power. A third driver may additionally provide power to the light source that can vary based on the dimming signal. Another example having three drivers may involve a first driver providing a fixed amount of power to the light source, preferably at the first driver's rated power. A second driver may additionally provide the light source with power that can vary based on a dimming signal. In this example, the third driver does not provide power to the light source. The control decisions of the drivers as defined in the previous example may be based on a dimming signal and / or discrete dimming levels. Between two discrete steps, the controller may provide an additional dimming step that allows a driver providing variable power to the light source to change its output power according to the dimming signal.

[0016] In further examples, the first driver and / or the second driver are non-dimmable.

[0017] If a driver is non-dimmable, it is configured to provide a fixed amount of power. Therefore, a driver can provide only one power level, which may also be its rated power. Since the driver is optimized in design to provide this single amount of power with the highest possible efficiency, it has optimal power efficiency. In this example, if all drivers are non-dimmable, the driver circuit may only provide discrete dimming steps available in proportion to the number of drivers provided.

[0018] In a further example, the controller is configured to turn a first driver and a second driver on and off based on discrete dimming levels.

[0019] A simple way to allow and deny power from a driver to a light source is to turn the corresponding driver on and off. If the controller determines, based on the discrete dimming level, that a driver should not be supplying power to the light source, the controller turns off the corresponding driver. If the discrete dimming level increases, the controller may decide to turn on the corresponding driver. The advantage of turning off a driver is that it consumes less or no power during the off period. This significantly increases the efficiency of the corresponding driver, and therefore the efficiency of the driver circuit.

[0020] In a further example, the first driver and / or the second driver are dimmable and are adapted to be dimmed down to a minimum output power of 50%. Preferably, the first driver and / or the second driver cannot be dimmed below this minimum output power of 50%. Below this output power level, the efficiency of the driver may begin to decrease significantly, and therefore further dimming would have an excessive impact on the efficiency of the driver circuit.

[0021] The driver may be designed to operate with optimal efficiency at the rated power of 100% output power. If the driver deviates from this power point, the efficiency will drop. If either or both drivers reduce the output power to less than 50%, the influence of the driver circuit may become too large and thus undesirable. Therefore, the driver should be configured so that the output power cannot drop below 50%.

[0022] In a further example, the first driver and / or the second driver is a dimmable switched mode power supply, and the first driver and / or the second driver is adapted to be dimmed so that the total efficiency of the driver circuit does not fall below 95%.

[0023] To ensure good overall efficiency of the driver circuit, it is desirable to avoid the total efficiency dropping below 95%. This means that the driver is designed to supply power to the light source such that the total efficiency does not fall below 95%. This may also mean, for example, that the driver is not permitted to be dimmed such that the total efficiency falls below 95%. The input power and the output power can be measured, which enables the controller to determine how efficient the driver circuit is.

[0024] In a further example, the driver circuit includes an auxiliary driver that is adapted to supply power to the controller and is adapted to be electrically isolated from the light source.

[0025] The controller typically requires its own power supply. The controller has its own power requirements. Therefore, it is desirable to provide an auxiliary driver that has power efficiency optimized for the power consumed by the controller. This can be done when the auxiliary driver is only used to supply power to the controller. It is preferable to electrically isolate the auxiliary driver from the light source so that the auxiliary driver cannot supply power to the light source.

[0026] In a further example, the driver circuit includes a further auxiliary driver, and the further auxiliary driver is adapted to power the controller when the driver circuit is in standby mode.

[0027] In standby, the controller may consume less power than during normal operation. It is preferable to provide good power efficiency also during the standby mode of the driver circuit. The further auxiliary driver may have a power efficiency optimized for the power consumed by the controller during standby. During standby, the controller may still be active, for example, to receive a wireless control signal.

[0028] In a further example, at discrete dimming levels where the first driver and the second driver provide power to the lighting load, the first driver and the second driver operate in an interleaved mode of operation.

[0029] At discrete dimming levels where both drivers provide power with optimized power efficiency, it is desirable for the drivers to operate in an interleaved operation mode. The controller can control the two drivers to operate with a relative phase delay. The phase delay is preferably 180 degrees when two drivers are used, or 360° / n when the number of drivers is n. As a result, the output current has a ripple at twice the frequency, but the peak-to-peak amplitude is reduced.

[0030] In another example, a lighting device is provided. The lighting device includes a driver circuit according to any of the previous examples and a light source.

[0031] The lighting device benefits from the driver circuit according to the present invention. The lighting device can provide a dimmable light output from the light source while maintaining good efficiency.

[0032] In another example, the controller is configured to control a first driver and a second driver based on the dimming level such that the effectiveness of the lighting device increases when the dimming level decreases.

[0033] Preferably, the efficacy of the lighting device increases. This can be done by turning off one of the drivers when the discrete dimming level is such that only one driver is needed to power the light source. In this case, the light source is configured to receive current only from the first driver and not from the second driver. This means that less current is supplied to the light source, and the current density of the light source decreases. The light source has improved efficacy at the reduced current density, and therefore the efficiency of the lighting device improves.

[0034] In another example, the lighting load is a semiconductor lighting load, preferably an LED load, and more preferably a filament.

[0035] Preferably, the illumination load is a semiconductor illumination load. Examples of semiconductor loads are LEDs, laser diodes, and vertical-cavity surface-emitting lasers (VCSELs). Preferably, the LED is formed as a filament. [Brief explanation of the drawing]

[0036] Hereinafter, examples of the present invention will be described with reference to the accompanying drawings. [Figure 1] An example of a circuit diagram is shown. [Figure 2] Here is another example of a circuit diagram. [Figure 3] The 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]Another graph showing the relationship between output power and dimming level is shown. [Figure 6] Another graph showing the relationship between output power and dimming level is shown. [Figure 7] Here is another example of a circuit diagram. [Figure 8] Another graph showing the relationship between output power and dimming level is shown. [Figure 9] Another graph showing the relationship between output power and dimming level is shown. [Figure 10] Another graph showing the relationship between output power and dimming level is shown. [Figure 11] Here is another example of a circuit diagram. [Figure 12] Here is another example of a circuit diagram. [Figure 13] An example of a light source is shown. [Figure 14] Here is another example of a circuit diagram. [Figure 15] Here is another example of a circuit diagram. [Figure 16] Here is another example of a circuit diagram. [Modes for carrying out the invention]

[0037] The present invention will be described with reference to the figures.

[0038] The detailed descriptions and specific examples illustrate exemplary embodiments of the apparatus, systems, and methods, but should be understood to be for illustrative purposes only and not intended to limit the scope of the invention. These and other features, aspects, and advantages of the apparatus, systems, and methods of the invention will be better understood from the following description, the appended claims, and the appended drawings. Please understand that the drawings are for illustrative purposes only and are not drawn to scale. Please also understand that the same reference numerals are used to indicate the same or similar parts throughout the drawings.

[0039] Figure 1 shows an example circuit diagram of a lighting device having a driver circuit that provides output power to a light source LED. The driver circuit may be coupled to the mains via a rectifier circuit having four diodes D10, D11, D12, and D13. The rectifier circuit provides a rectified mains voltage. In this example, a first driver D1 and a second driver D2 receive the rectified mains 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 provided by a dimmer or an external device that provides a dimming command. Examples of devices that can provide a dimming signal include a phase-cut dimmer, a 0-10V dimmer, a DALI dimmer, a DMX dimmer, or a wireless remote device that provides a dimming signal. The first driver D1 and the second driver D2 are configured to provide power to the same load, which in this example is the light source LED.

[0040] 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 may be a string of LEDs coupled in series, preferably forming a filament. Other devices or combinations of devices, such as a laser diode or VCSEL, may also be coupled in series. For clarity, the example shows LEDs as the light source. Preferably, the size of the LED string cannot be changed. This means that each LED string has only one input and one return for receiving and returning current. Therefore, the forward voltage cannot be changed, for example, by a shunt switch that shunts a portion of the LED string. In this way, the power consumed by the light source LED is regulated by the driver supplying power to the light source LED and not by changing the size of the light source LED. The light source LED may have two LED strings in parallel, preferably having substantially the same forward voltage. Details of this topology are provided in further examples.

[0041] Controller C receives a dimming signal and uses this signal 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 may base the number of discrete dimming levels on the number of drivers provided in the driver circuit. In the example of drivers having the same power rating, the number of discrete dimming levels may be determined by the following formula: 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 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. In this case, 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% may be converted to 0% as a discrete dimming level. A dimming signal between 26% and 75% may be converted to 50% as a discrete dimming level. A dimming signal between 76% and 100% may be converted to 100% as a discrete dimming level. These values ​​are merely examples of how to convert the dimming range of a dimming signal 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, controller C provides the drivers with control signals that prevent the first driver D1 and the second driver D2 from supplying power to the light source LEDs. Both drivers may be turned off. At 50% output power, controller C provides the drivers with control signals that allow one driver to supply rated power to the load and prevent the other driver from supplying power to the load. At 100% output power, controller C provides the drivers with control signals that allow both drivers to supply rated power to the light source.

[0042] At all discrete dimming levels, the lighting device can operate with the highest possible efficiency. If fewer drivers than the maximum number supply power to the light source LEDs, the light efficacy can be further improved. Since the light source has a single forward voltage that cannot be altered, for example by shunting a portion of the series connection of LEDs in the light source, the number of drivers supplying power to the light source determines the current density of the light source LEDs. Fewer drivers supplying power to the light source LEDs result in a lower current density through the light source LEDs, thus increasing the light efficacy of the lighting device.

[0043] Figure 2 shows an example of a detailed circuit diagram of the circuit shown in Figure 1. In the provided example, rectifier circuits D10, D11, D12, and D13 are provided. The rectifier circuits provide the rectified voltage 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 the input 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. These diodes form freewheeling diodes in the boost converter topology and allow the outputs of the first driver D1 and the second driver D2 to be coupled together. In a topology other than a boost converter, for example a buck converter, an additional diode may be required for each driver to allow these drivers to be coupled at the output. Controller C provides control signals to the first driver D1 and the second driver D2. In this example, the control signals may be provided 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 LED. Preferably, Controller C controls the drivers so 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.

[0044] Figure 3 shows a graph illustrating the relationship between output power and dimming level in a driver circuit 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 the discrete dimming level 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 sets the discrete dimming level to 0% output power between dimming levels 0% and 33%. Between dimming levels 34% and 66%, the discrete dimming level is set to 50%. Between 67% and 100%, the discrete dimming level is set to 100%. This means that no power is supplied to the light source LED in the dimming range of 0% to 33%. Between dimming levels 34% and 66%, 50% output power is supplied to the light source LED. Controller C activates one driver to provide the rated power corresponding to 50% output power to the light source LED, and prevents the other driver from supplying power to the light source LED. Between dimming levels 67% and 100%, 100% output power is provided to the light source LED. Controller C activates both drivers to provide their respective rated power to the light source LED, which corresponds to 100% output power. It is clear that other relationships between dimming levels and discrete dimming levels can be derived while maintaining the same discrete dimming levels.

[0045] Figure 4 shows a graph illustrating the relationship between output power and dimming level in 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, it can be seen that 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 may also be derived from the equation D = N(N+1) / 2 + 1, where D is the number of discrete dimming levels and N is the number of drivers. As an example, the first driver D1 is configured to have a rated power of 1W, and the second driver D2 is configured to have a rated power of 3W. When neither driver is supplying power to the light source LED, the power to the light source LED is 0W, which corresponds to a dimming level between 0% and 24%. When only the first driver D1 supplies power to the light source LED at its rated power, the light source LED receives 1W, which corresponds to 25% of the total output power. In this case, this output power relates to dimming levels between 25% and 50%. When only the second driver D2 supplies power to the light source at its rated power, the light source LED receives 3W, which corresponds to 75% of the total output power. In this case, this output power 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%. Here, both the first driver D1 and the second driver D2 supply power to the light source LED at their respective rated powers.

[0046] Figure 5 shows another graph illustrating the relationship between output power and dimming level in a driver circuit when two drivers 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, the discrete dimming levels are used differently than in 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, we again assume that the first and second drivers are configured to have substantially identical power ratings. At 0%, controller C controls both drivers so as not to power the light source LED. For example, at dimming levels between 0.1% and 50%, controller C controls one of the drivers to allow power to be supplied to the light source LED. Instead of providing power at a single rated power level, the power of a single active driver follows the dimming signal and is therefore set to follow the dimming level. For example, at a dimming level of 10%, the active driver may be configured to provide 20% of its rated power output, and at 50%, the active driver may be configured to provide 100% of its rated power output. At 50.1%, controller C determines that the 50% discrete dimming level has been exceeded. This means that between the dimming levels of 50.1% and 100%, one driver provides its rated power, and additionally, the other driver provides variable power. For example, at a dimming level of 60%, one driver may be configured to provide 100% of its rated power, and the driver providing variable power may be configured to provide 20% of its rated power output. At a dimming level of 100%, both drivers may be configured to provide 100% of their rated power output.Therefore, controller C determines discrete dimming levels, and between two discrete dimming levels, one driver is configured to provide variable power to the light source LED, i.e., the power may be changed based on the dimming level, and the other driver is configured to provide fixed power to the light source LED, preferably at the driver's rated power.

[0047] Figure 6 shows a graph similar to the graph shown in Figure 5. In this example, the power ratings of the two drivers are carefully selected. This power rating of the drivers depends on the minimum efficiency that the drivers are allowed to have. The drivers are allowed to provide a variable level from the power rating down to the power level corresponding to the minimum allowable efficiency. The first driver D1 has a power rating at 100% power output, and therefore from 100% to P rated D1 *min_loading has a power range. Here, P rated D1 P is the rated power of the first driver D1, and min_loading is the minimum allowable power of the first driver D1 at the percentage in which the minimum driver efficiency target is met. To provide a smooth dimming curve, the minimum power that the second driver D2 can provide is less than or equal to the rated power of the first driver D1. In this case, the rated power of the second driver D2 is P rated D2 =P rated D1 Determined by / min_loading. Here, P rated D2 This is the rated power of the second driver D2, and P rated D1 is the rated power of the first driver D1, and min_loading is the minimum allowable power of the second driver D2 at the percentage in which the minimum driver efficiency target is met.

[0048] For example, the first driver D1 and the second driver D2 have a minimum allowable loading at 70% where the minimum driver efficiency target is met. The first driver D1 may have a rated power of 1.75W. In this case, the minimum power that may be provided by the first driver D1 is 1.23W. In this case, the second driver D2 is configured to provide a minimum power of 1.75W. This results in a rated power of 2.5W. A total of 4.25W can be provided by the driver circuit. 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 can be provided by the second driver D2. 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, corresponds to 100% of the dimming range.

[0049] The first part of the graph (solid line) represents the region where power cannot be supplied to the light source LED in this configuration. In this case, controller C may prevent both drivers from supplying power to the light source LED. By increasing the dimming level to 28.2%, controller C turns on the first driver D1 and supplies 1.23W to the light source LED at 70% loading. By further increasing the dimming level, the first driver D1 can supply more power to the light source LED. If the dimming level is further increased to 41.2%, the first driver D1 supplies power to the light source LED at its rated power, and therefore preferably at maximum efficiency. By further increasing the dimming level above 41.2%, the second driver D2 supplies at least 1.75W of power to the 41.2% light source LED. In this situation, the first driver D1 is prevented from supplying power to the light source LED. By further increasing the dimming level, the second driver D2 can supply more power to the light source LED. If the dimming level is further increased to 58.8%, the second driver D2 provides power to the light source LED at its rated power, and therefore preferably at maximum efficiency. By increasing the dimming level above 58.8%, the controller C controls both drivers to power the light source LED. In this case, to minimize the gap in the dimming range, the second driver D2 provides reduced power to the light source LED, and the first driver D1 is also allowed to power the light source. The gap may be due to the first driver D1 being unable to provide power below 70% loading, resulting in virtually no increase in output power being provided in the dimming range from 58.8% to 70%. Preferably, in this dimming range, the output power to the light source LED is maintained at 2.5W. If the dimming level is further increased above 70%, both drivers can begin to provide power to the light source LED. At 70%, both drivers can provide a minimum allowable power of 1.23W for the first driver D1 and 1.75W for the second driver D2. In this case, the power supplied to the light source LED at 70% is 2.98W.In this example, the gap in the dimming range between 58.8% and 70% corresponds to a power gap of 2.98W - 2.5W = 0.48W. At dimming levels between 70% and 100%, the driver increases the power to the light source LED to match the corresponding dimming level. This can be done by simultaneously increasing the power of both drivers, or by increasing the power from the first driver D1 in the first part of the dimming range from 70% to 100%, and increasing the power of the second driver D2 in the second part of the dimming range from 70% to 100%. At the 100% dimming level, the first driver D1 and the second driver D2 provide the rated power to the light source LED. In this example, a total power of 1.75W + 2.5W = 4.25W is provided to the light source LED.

[0050] To reduce the gap in the dimming range, the first driver D1 and / or the second driver D2 may be made capable of supplying power to levels much lower than 70%. In the provided example, the gap in the dimming range between 58.8% and 70% may be reduced, or even eliminated. In the provided example, the gap in the dimming range between 0% and 28.8% may also be reduced or eliminated in this case. This may come at the cost of some efficiency loss, as it may further reduce the efficiency of the drivers.

[0051] Figure 7 shows an example of a circuit diagram of a lighting device having a driver circuit. The driver circuit has additional drivers. The driver circuit 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 the rectified voltage 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 the input and provide parallel power to the light source LEDs. A controller C provides control signals to the first driver D1, the second driver D2, and the third driver D3. Thus, the controller C determines the power that can be supplied to the light source LEDs. Preferably, the controller C controls the drivers so that the power supplied to the light source LEDs corresponds to the power required by the light source LEDs according to the discrete dimming level.

[0052] Figure 8 shows an example graph illustrating the relationship between output power and dimming level in a driver circuit 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 LED. 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 LED at the corresponding power rating of that driver. As a result, 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%, and as a result, controller C controls two of the three drivers to provide power to the light source LEDs at the corresponding rated power of those drivers. As a result, 66.67% of the total power that can be provided by the driver circuit is supplied to the light source LEDs. At dimming levels between 76% and 100%, the discrete dimming level is set to 100%, and as a result, controller C controls all drivers to provide power to the light source LEDs at the corresponding rated power of those drivers. As a result, 100% of the total power that can be provided by the driver circuit is supplied to the light source LEDs.

[0053] Figure 9 shows another example of a graph illustrating the relationship between output power and dimming level in a driver circuit 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: 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 that can be provided by the driver circuit being 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 by the first driver D1 alone at the rated power of the first driver D1. At dimming levels between 28.7% and 42.9%, the discrete dimming level is set to 25%, resulting in power being supplied to the light source LED by the second driver D2 alone at the rated power of the second driver D2. At dimming levels between 43% and 57.1%, the discrete dimming level is set to 37.5%, resulting in power being supplied to the light source LED by the first driver D1 and the second driver D2 alone at the rated power of the first driver D1 and the second driver D2. At dimming levels between 57.2% and 71.4%, the discrete dimming level is set to 75%, resulting in power being supplied to the light source LEDs by only 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 light source LEDs by only 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, second driver D2, and third driver D3 supplying power to the light source LED at their respective rated powers. Changing the rated power of the drivers results in different distributions of discrete dimming levels.

[0054] Figure 10 shows another graph of the relationship between output power and dimming level in a driver circuit when three drivers 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 four discrete dimming levels: one at 0% output power, one at 33.3% output power, one at 66.67% output power, and the last one at 100% output power. In this example, the discrete dimming levels are used differently than in the previous example. The discrete dimming levels are used to determine whether an additional driver is needed to provide power to the light source or whether another driver should be prevented from supplying power to the light source. In this example, we again assume that the first driver D1, the second driver D2, and the third driver D3 are configured to have substantially the same power rating. At 0%, controller C controls all drivers so as not to supply power to 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 may be configured to provide 33.33% of its rated power output, and at a dimming level of 33.33%, the active driver may be configured to provide 100% of its rated power output. At a dimming level of 33.34%, controller C determines that the discrete dimming level of 33.33% has been exceeded. This means that between dimming levels of 33.34% and 66.67%, one of the drivers provides its rated power, and additionally, another driver provides variable power. At a dimming level of 66.68%, controller C determines that the discrete dimming level of 66.67% has been exceeded. This means that between dimming levels of 66.68% and 100%, two of the drivers provide their rated power, and additionally, a third driver provides variable power.

[0055] For example, at a dimming level of 77.78%, two drivers may be configured to provide 100% of their rated power, and a driver providing variable power may be configured to provide 33.33% of its rated power. At a dimming level of 100%, all drivers may be configured to provide 100% of their rated power. Therefore, the controller C determines discrete dimming levels, and between two discrete dimming levels, one driver may be configured to provide variable power to the light source LEDs, i.e., the power may change based on the dimming level, while another driver, or both drivers, are configured to provide their respective rated power to the light source LEDs depending on the absolute dimming level.

[0056] Figure 11 shows another example of a driver circuit. In this example, rectifier circuits D10, D11, D12, and D13 are provided. The rectifier circuits provide the rectified voltage 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 the input 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 or disable signal to each driver. 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 a phase-cut dimmer, a 0-10V dimmer, a DALI dimmer, a DMX dimmer, or a wireless remote device that provides a dimming signal. The first driver D1 and the second driver D2 are configured to supply power to 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 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 LED at an optimal power conversion rate. Therefore, the second driver D2 provides a second output power at a second optimal power conversion rate. If both drivers are configured to provide the same amount of power, the first output power and the second output power may be the same, and therefore, the first optimal conversion rate and the second optimal conversion rate may also be the same. The controller C may 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 may 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 light source LED 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.

[0057] For example, at a 0% dimming level, both drivers are turned off. The dimming level may be increased, and the on-time of the first driver D1 may be increased until the first driver has an on-time with a 100% duty cycle. This may occur at a 50% dimming level. At a 50% dimming level, the first driver D1 provides rated power for 100% of the time. If the dimming level is increased further, the controller enables both the first driver D1 and the second driver D2. For example, the first driver D1 may be controlled to have a 100% on-time across the entire range from 50% to 100%. In this case, the second driver D2 is controlled to have an increasing on-time as the dimming level increases. At a dimming level of 100%, both the first driver D1 and the second driver D2 are controlled to operate with an on-time with a 100% duty cycle. Effectively, both drivers are continuously supplying power to the light source LED at rated power.

[0058] As another example, the rated power of the first driver D1 may be different from the rated power of the second driver D2.

[0059] For example, the first driver D1 may have a power rating of 2W. The second driver D2 may have a power rating of 4W. In this case, the maximum total power that can be supplied to the light source LED by the driver circuit is 6W. When the dimming level is set to 50%, an output power of 3W may be required. In this case, the controller C may provide the first driver D1 with a first duty cycle of 100% and the second driver D2 with a second duty cycle of 25%. The first driver D1 supplies 2W and the second driver D2 supplies 1W, for a total of 3W supplied to the light source LED. Another way to supply 3W of power is to provide the first driver D1 with a first duty cycle of 0% and the second driver D2 with a second duty cycle of 50%. The first driver D1 supplies 0W to the light source LED and the second driver D2 supplies 3W to the light source LED. It is clear that these examples form examples from among many combinations of duty cycles that can be used to achieve the desired output power of the driver circuit.

[0060] When the first driver D1 and / or the second driver D2 are configured to supply power to the light source, this is done at the rated power level. Therefore, supplying power to the light source is done with high efficiency. It is our insight that, in order to achieve maximum efficiency, the drivers should supply power to the load at a single rated power level. Deviating from this power level results in reduced efficiency. By supplying the load with a duty cycle at the rated power, it is possible to reduce the amount of power supplied to the load while maintaining high efficiency.

[0061] Figure 12 shows a further example of a driver circuit. The driver circuit may be similar to the driver circuit shown in Figure 11. In this example, rectifier circuits D10, D11, D12, and D13 are provided. The rectifier circuits provide the rectified voltage 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 the input 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 driver. 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 a phase-cut dimmer, a 0-10V dimmer, a DALI dimmer, a DMX dimmer, or a wireless remote device that provides a dimming signal. The first driver D1 and the second driver D2 are configured to supply power to the same load, which in this example is the light source LED. The first driver D1 provides the rated power to the light source at an optimal power conversion rate. Therefore, the first driver D1 provides the first output power at a first optimal power conversion rate. The second driver D2 provides the rated power to the light source at an optimal power conversion rate. Therefore, the second driver D2 provides the second output power at a second optimal power conversion rate. If both drivers are designed to provide the same amount of power, the first output power and the second output power may be the same, and therefore, the first optimal conversion rate and the second optimal conversion rate may also be the same. The controller C may 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 may 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.

[0062] Preferably, the on-time is controlled using pulse width modulation (PWM). The frequency of the PWM signal is, for example, 200 Hz, which is above the frequency perceptible to the human eye. More preferably, the frequency is above 1 kHz. A filter capacitor can be connected in parallel with the LED to realize a smoothing current through the LED load.

[0063] When the first driver D1 and / or the second driver D2 are configured to supply power to the light source, this is done at the rated power level. Therefore, supplying power to the light source is done with high efficiency. It is our insight that, in order to achieve maximum efficiency, the drivers should supply power to the load at a single rated power level. Deviating from this power level results in reduced efficiency. By supplying the load with a duty cycle at the rated power, it is possible to reduce the amount of power supplied to the load while maintaining high efficiency.

[0064] A series configuration of buffer capacitor C1 and switch J1 may be provided at the outputs of rectifier circuits D10, D11, D12, and D13. Although the switch is shown as a simple controllable switching element, additional circuitry may be provided to perform the required function, namely, to control the flow of current through buffer capacitor C1. This means that a switching device having one or more switching elements and control circuits may be used instead of the switch. Switch J1 may be controlled by controller C. Switch J1 is used to regulate the current through buffer capacitor C1. This allows buffer capacitor C1 to be charged and discharged in a controlled manner. Controlling the driver with duty cycle control can cause disturbance at the input of the driver circuit. This is because there are moments when the driver does not draw current from the mains power supply. Buffer capacitor C1 may be used to draw current from the mains power supply when no current is drawn or insufficient current is drawn by any driver. This allows the current from the mains power supply to be smoothed. Preferably, controller C controls switch J1 and the driver so that the driver circuit performs power factor correction. This means that the current drawn from the mains power supply follows the voltage waveform. The mains power supply voltage may be a sine wave at a frequency of, for example, 50 Hz or 60 Hz. In this case, the current waveform follows this voltage waveform in phase. This can also be achieved by placing a common input Power Factor Correction (PFC) stage between the rectifier and drivers D1 and D2. The common PFC stage draws a sinusoidal current from the mains 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.

[0065] Figure 13 shows an example of a circuit diagram in which an improved light source LED is provided that 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 substantially the same forward voltage. Preferably, the first LED load LED1 and the second LED load LED2 are provided as filaments. Although the first LED load LED1 and the second LED load LED2 are shown as single LEDs, more LEDs can be coupled in series to form a string or filament of LEDs. A first series switch M10 is provided in series with the first LED load LED1. A second series switch M11 is provided in series with the second LED load LED2. The control circuit 1 is configured to control the first series switch M10 and the second series switch M11. The control circuit is configured to sense parameters of the voltage or current provided by the driver circuit. Examples of parameters may be the frequency, duty cycle, or amplitude of the voltage or current. The parameters are used by the control circuit 1 to determine how the first series switch M10 and the second series switch M11 are controlled. For example, frequency modulation of the voltage or current provided by the driver circuit may provide the control circuit 1 with information to determine which series switch should be controlled. For example, 1 kHz frequency modulation may provide the control circuit 1 with an indication to close the first series switch M10 and open the second series switch M11, 2 kHz modulation may cause the first series switch M10 to open and the second series switch M11 to close, and 3 kHz modulation may cause the first series switch M10 to close and the second series switch M11 to close. As another example, similar control can be provided by changing the amplitude of the voltage or current provided by the driver circuit. Changes in voltage or current can alter the control of the first series switch M10 and the second series switch M11.The advantage of controlling the light source LED configuration according to the example above is that power and data can be sent from the driver circuit to the light source with only two wires, which is particularly beneficial when the light source LED is designed as a filament in a light bulb, such as a retrofittable bulb with a screw-in or bayonet base. In such situations, the number of wires that can be supplied through the stem may be limited. Using the dimming technique provided in the example allows for easy dimming of the filaments, while the control circuit 1 can distribute 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 cold 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 LED. The opening and closing of the first series switch M10 and the second series switch M11 can be a continuous time process, each with its own duty cycle, for example, under PWM control, where either the first series switch M10 is closed or the second series switch M11 is closed. Preferably, this switching process is performed at a frequency greater than 100 Hz, more preferably greater than 2 kHz. 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, for example, in the startup of the lighting device. During operation, the open / closed states of the first series switch M10 and the second series switch M11 can be changed by different commands, for example, commands to change the color or color temperature.

[0066] Figure 14 shows a circuit diagram of a lighting device having a simpler example of an improved light source LED that 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 has a forward voltage lower than the forward voltage of the second LED load LED2. Preferably, the first LED load LED1 and the second LED load LED2 are provided as filaments. Although the first LED load LED1 and the second LED load LED2 are shown as single LEDs, more LEDs can be coupled in series to form a string or filament of LEDs. A first series switch M10 is provided in series with the first LED load LED1. A control circuit 1 is configured to control the first series switch M10. The control circuit is configured to sense a voltage or current parameter provided by the driver circuit. Examples of parameters may be the frequency, duty cycle, or amplitude of the voltage or current. The parameters are used to determine how the first series switch M10 is controlled by the control circuit 1. For example, frequency modulation of the voltage or current provided by the driver circuit may provide the control circuit 1 with information to control the first series switch M10. For example, frequency modulation may provide the control circuit 1 with an indication to close the first series switch M10, and the absence of modulation (absense) may provide the control circuit 1 with an indication to open the first series switch M10. When the first series switch M10 is open, the current provided by the driver circuit can flow only through the second LED load LED2. When the first series switch M10 is open, the current provided by the driver circuit can flow through the first LED load LED1. If 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 allows 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, current flows only through the first LED load LED1. As another example, similar control can be provided by changing the amplitude of the voltage or current provided by the driver circuit. The voltage change can alter the control of the first series switch M10. The advantage of controlling the light source LED configuration according to the above example is that power and data can be sent from the driver circuit to the light source with only two wires, which is particularly beneficial when the light source LED is designed as a filament in a light bulb, such as a retrofittable light bulb with a screw-in or bayonet base. In such a situation, the number of wires that can be provided through the stem may be limited. Using the dimming technique provided in the example allows for easy dimming of the filament, while the control circuit 1 can distribute the provided 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 cold color temperature. Therefore, parameters can be used to enable 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 in which the first series switch M10 is opened or closed on a duty cycle, e.g., PWM control. Preferably, this switching process is performed at a frequency greater than 100 Hz, more preferably greater than 2 kHz. Alternatively, to provide simple control over the control circuit 1, the opening and closing of the first series switch M10 can be a single event, e.g., in the startup of the lighting device. During operation, the open / closed state of the first series switch M10 can be changed by different commands, e.g., commands to change the color or color temperature.

[0067] Figure 15 shows a circuit diagram of a lighting device having a further simple example of an improved light source LED that 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 has a forward voltage 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 depending on the amount of driver powering the light source. At relatively low currents, all the current flows through the second LED load LED2 and 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. As the current increases, the forward voltage of the second LED load LED2 increases only slightly, but a larger voltage drop occurs across resistor R1. By further increasing the current to the light source LED, the sum of the forward voltage of the second LED load LED2 and the voltage drop across resistor R1 increases until this sum reaches or exceeds the forward voltage of the first LED load LED1. At this increased current, the first LED load LED1 also begins to conduct. Therefore, by increasing or decreasing the current to the light source, a simple distribution of current through the first LED load LED1 and the second LED load LED2 can be achieved. Preferably, the first LED load LED1 is a cold white LED load and the second LED load LED2 is a warm white LED load. At low currents, mainly the warm white LEDs are active, and as the current increases, the cold white LEDs also become active. This allows for a very simple imitation of a dimmable incandescent filament or halogen lamp. Compared to the examples provided in Figures 13 and 14, this circuit does not require a control circuit 1, but resistor R1 may introduce additional power loss.

[0068] Figure 16 shows another example of a lighting device. In the provided example, rectifier circuits D10, D11, D12, and D13 are provided. The rectifier circuits provide rectified voltages to the first driver D1 and the second driver D2. The first driver D1 provides regulated power to the first light source LED1. The second driver D2 provides regulated power to the second light source LED2. A controller C is used to control the first driver D1 and the second driver D2. The 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 include a phase-cut dimmer, a 0-10V dimmer, a DALI dimmer, a DMX dimmer, or a wireless remote device that provides a dimming signal. The first driver D1 is configured to provide regulated current to the first light source LED1. The current amplitude is set to a value that matches the current density of the first light source LED1, which enables the optimal conversion of electrical energy to photonic energy. The LED has an optimal current density, at which point the power supplied to the LED is most efficiently converted to light. Therefore, the LED has the highest efficacy at the optimal current density. For example, if the current density of the LED is increased from the optimal current density by increasing the current amplitude through the LED, the light output increases, but the light efficacy decreases. For example, if the current density of the LED is decreased from the optimal current density by decreasing the current amplitude through the LED, the light output decreases, and the light efficacy also decreases. Therefore, it is desirable that the driver be able to provide the LED load with a current corresponding to the LED's optimal current density. The first driver D1 provides a current that allows the current density of 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 current that allows the current density of 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 enables the light source to operate at an optimized current density. The optimized current density for a light source as an LED is considered to be a single value, and therefore, it is desirable that a fixed current be provided to the light source. The fixed current may vary to compensate for changes in the value of the optimal current density. For example, the optimal current density may vary based on the temperature or lifespan of the light source. By optimizing the driver design with a desired current relative to the optimal current density, the driver operates at maximum efficiency, and the light source provides light at maximum efficiency. Therefore, the first driver D1 is adapted to provide current at the rated power level to the first light source LED1, and the second driver D2 is adapted to provide current at the rated power level to the second light source LED2. The first light source LED1 and the second light source LED2 may have different dimensions. Therefore, the forward voltage and / or required current of the first light source LED1 will be different from that of the second light source LED2. Alternatively, the first light source LED1 and the second light source LED2 may have identical electrical characteristics. When controller C receives a dimming signal, the controller may decide to activate a certain number of drivers based on the dimming level. For example, at a dimming level of 50%, the controller may decide to activate one driver so that one light source is activated. For example, the first driver D1 may supply current to the first light source LED1 at its rated power level, while the second driver D2 may not supply current to the second light source LED2. This allows the lighting device to still provide 50% of the light it can generate with very high efficiency. As with other examples, more driver and light source combinations can introduce more dimming steps while operating the lighting device with the highest possible efficiency.

[0069] In the provided example, the controller C and additional peripheral electrical components may be powered using dedicated power supplies. An auxiliary power supply may be provided for powering the controller C. Preferably, the auxiliary power supply is electrically isolated from the light source LEDs. Therefore, the auxiliary power supply is a dedicated power supply for the controller C. The auxiliary power supply cannot supply power to the light source LEDs and can therefore be optimized for powering the controller C.

[0070] During the standby mode of the lighting device, power should not be supplied to the light source LEDs, 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 this case, the controller C requires less power than when the lighting device is operating. A further auxiliary power supply may be provided to power the controller C and surrounding electrical components during standby. The further auxiliary power supply is optimized to power the controller C in standby mode.

[0071] Under the definition of rated power, it can be understood that the driver has a defined power capability. Within this power capability, the driver provides power to the light source LED most efficiently. The driver design is optimized so that the highest efficiency can be achieved at this rated power level. The rated power may be the maximum power that the driver can provide. Alternatively, the rated power may be below the maximum power level. If the driver provides power different from the rated power, for example, higher or lower than the rated power, the driver's efficiency will decrease. Therefore, for maximum efficiency, it is desirable to operate the driver at the rated power when it is necessary for the driver to provide power to the light source LED.

[0072] In the provided example, the driver may be a separate device with separate components. To improve component and space utilization, some components may be reused across multiple drivers.

[0073] In the provided example, the dimming level is linearly related to the power required by the LED light source. Other relationships, such as logarithmic or nonlinear, are also possible and may produce the desired effect.

[0074] In the provided example, for simplification, the discrete dimming levels are evenly distributed across the entire dimming range. It should be understood that this is only one option for converting dimming levels to discrete dimming steps. Alternatively, the discrete dimming steps may be distributed such that lower dimming subranges have more discrete dimming steps than higher dimming subranges, or vice versa.

[0075] The dimming level should be understood as the amount of power that the driver circuit needs to supply to the load. 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.

[0076] The provided examples demonstrate the use of two or three drivers. It should be understood that, obviously, more drivers can be used. Furthermore, the more drivers used, the more discrete dimming steps can be provided.

[0077] 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.

[0078] The definition of dimmable in the context of dimmable drivers should be understood according to common practice. A dimmable driver can receive dimming signals such as 0-10V, wireless dimming commands, or phase-cut dimming signals. A non-dimmable driver may not be able to receive dimming signals and therefore always provides a fixed output current and / or voltage. A dimmable driver allows a light source to be dimmed such that the light output decreases as the power supplied to the light source decreases.

[0079] The light source LED may be considered as a single light source LED with input and return. Both drivers provide power to the input and return.

[0080] By examining the drawings, this disclosure, and the appended claims, other variations of the disclosed embodiments can be understood by those skilled in the art and can be performed in carrying out the claimed invention. In the claims, the word “comprising” does not exclude other components or steps, and the indefinite article “a” does not exclude plural. The mere fact that certain means are enumerated in different dependent claims does not imply that combinations of these means cannot be used advantageously. No reference numeral in the claims should be construed as limiting in scope.

Claims

1. A driver circuit for driving a light source, the driver circuit is A first driver adapted to provide a first maximum amount of power to the light source, A second driver adapted to provide a second maximum amount of power to the light source, A controller for controlling the first driver and the second driver, Includes, The controller is configured to receive a dimming signal indicating the dimming level for the light source. The controller is configured to convert the received dimming signal into a plurality of discrete dimming levels representing dimming levels corresponding to a first maximum power and / or a second maximum power provided by the first driver, and the controller is configured to allow or deny power to flow from the first driver and / or the second driver based on the received dimming signal, the driver circuit.

2. The driver circuit according to claim 1, wherein the driver circuit includes a third driver, the controller is configured to control the third driver, 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, and the controller is configured to allow or deny power to flow from the first driver and / or the second driver and / or the third driver based on the received dimming signal.

3. The driver circuit according to claim 1 or 2, wherein the first driver and the second driver are configured to have the same rated power.

4. The driver circuit according to claim 1 or 2, wherein the first driver and the second driver are configured to have different power ratings.

5. A driver circuit according to any one of claims 1 to 4, wherein, between two discrete dimming steps, only one driver is configured to provide variable power to the light source based on a dimming signal.

6. The driver circuit according to any one of claims 1 to 5, wherein the first driver and / or the second driver are non-dimmable.

7. The driver circuit according to any one of claims 1 to 6, wherein the controller is configured to turn the first driver and the second driver on and off based on the discrete dimming level.

8. The driver circuit according to any one of claims 1 to 7, wherein the first driver and / or the second driver are dimmable, and the first driver and / or the second driver are adapted to dim to a minimum output power of 50%.

9. The driver circuit according to any one of claims 1 to 8, wherein the first driver and / or the second driver is a dimmable switch-mode power supply, and the first driver and / or the second driver are configured to dim the light so that the overall efficiency of the driver circuit does not fall below 95%.

10. The driver circuit according to any one of claims 1 to 9, further comprising an auxiliary driver adapted to supply power to the controller and to be electrically isolated from the light source.

11. The driver circuit according to any one of claims 1 to 10, wherein the driver circuit includes a further auxiliary driver, the further auxiliary driver being adapted to supply power to the controller when the driver circuit is in standby mode.

12. The driver circuit according to any one of claims 1 to 11, wherein, in discrete dimming levels in which the first driver and the second driver provide power to a lighting load, the first driver and the second driver operate in interleaved operation mode.

13. A driver circuit according to any one of claims 1 to 12, Light source and Lighting devices, including...

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

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