A driving arrangement

Abstract

A driving arrangement comprises a main switch mode power converter and a secondary switch mode power converter. The main converter output and the secondary converter output are superposed into a driving output for driving a load. The driving arrangement has first and second modes of operation. In the first mode of operation, the secondary converter is used to at least partially cancel the voltage ripple in the output of the main converter, whereas in the second mode of operation, the secondary converter generates a larger output signal than in the first mode, by providing a smaller (or no) voltage ripple and using an extra headroom away from the maximum output voltage amplitude, provided by reducing the voltage ripple, to increase the average voltage amplitude of the output signal. The voltage amplitude of the driving output in the second mode is higher than that in the first mode but with less voltage ripple suppression.

Description

[0001] 2024PF80515

[0002] 1 05.12.2025 A driving arrangement

[0003] FIELD OF THE INVENTION

[0004] This invention relates to driving arrangements, for example for driving lighting loads such as LED luminaires.

[0005] BACKGROUND OF THE INVENTION

[0006] In many lighting applications such as outdoor (e.g. road) lighting, various types of luminaire are required, but the number required of each type of luminaire is very small. More specifically, mainly it is the LED loads that are different for various types of luminaires, and the LED loads have different forward voltages. For this reason, the LED driver is required to support various types of luminaire, such as with a high output voltage as well as a low output voltage, in order to reduce the part count and reduce costs such as R&D costs, product management costs and sourcing costs. High dimming efficiency is also required for energy saving purposes.

[0007] Different lighting applications also have different requirements for the light output, such as the tolerated amount of flicker resulting from the powering of the driving arrangement using AC mains. For road lighting applications, cancellation of flicker typically is not required by the lighting regulations, but some customers require flicker cancellation for their particular application.

[0008] Thus, for outdoor lighting applications, two types of driver are needed for different customers. One driver type is a high voltage ripple driver but with a high output voltage that can be implemented with low cost, and the other driver type is a low voltage ripple driver. As a result, there is a high component count for driver components to support the different applications.

[0009] It is desirable to provide a driver design that can support as many applications as possible with reasonable cost, fewer components and better performance. For example, it would be desirable to provide a driver design that can support applications where low flicker is required as well as applications where flicker is tolerated.2024PF80515

[0010] 2 05.12.2025 Even more, in some extreme conditions such as a cold start, the LED load voltage is higher than that in normal operation. It is desired for a drive to be able to cope with this phenomenon.

[0011] WO2023156262 discloses a driver arrangement with a power factor correction circuitry and a switched-mode power supply. In a first mode, the switched-mode power supply is able to generate an offset signal that is superimposed over a PFC output signal for attenuating a voltage ripple in the PFC output signal. In a second mode, the power factor correction circuitry is disabled and the switched-mode power supply is able to generate a supply power for a second load.

[0012] WO2023213613A1 discloses a power factor correction circuitry and a switched-mode power supply whose output is superimposed with the output of the power factor correction circuitry to compensate the ripple of the output of the power factor correction circuitry, wherein the switched-mode power supply can change the average amplitude of its output.

[0013] SUMMARY OF THE INVENTION

[0014] The invention is defined by the claims.

[0015] According to examples in accordance with an aspect of the invention, there is provided a driving arrangement comprising:

[0016] an input to receive an AC mains input with a mains frequency voltage ripple; a main switch mode power converter adapted to convert the AC mains input into a main output with a first voltage ripple corresponding the mains frequency voltage ripple;

[0017] a secondary switch mode power converter adapted to generate a secondary output; and

[0018] an output connection to superimpose the main output and the secondary output into a driving output for driving a load,

[0019] wherein the driving arrangement has first and second modes of operation, wherein:

[0020] in the first mode of operation, the secondary switch mode power converter is configured to generate the secondary output with a first average voltage amplitude and with a second voltage ripple adapted to at least partially cancel the first voltage ripple, wherein the sum of the first average voltage amplitude and the second voltage ripple is capped by the maximum output voltage amplitude;2024PF80515

[0021] 3 05.12.2025 in the second mode of operation, the secondary switch mode power converter is configured to generate the secondary output wherein reducing a voltage ripple in the secondary output and using an extra headroom away from the maximum output voltage amplitude, provided by reducing the voltage ripple, to increase the average voltage amplitude of the secondary output such that the voltage amplitude of the driving output in the second mode is higher than that in the first mode.

[0022] This driving arrangement uses a main switch mode power converter to convert an AC input into an output with a first voltage ripple, for example corresponding to a mains frequency voltage ripple. The secondary switch mode power converter generates a secondary output which is superimposed with the main switch mode converter output to create a driving output.

[0023] In the first mode of operation, low flicker can be achieved by using the secondary converter for voltage ripple cancellation. In the second mode of operation, when low voltage ripple is not required, the secondary switch mode power converter is able to generate an averagely larger output signal because the secondary switch mode power converter has an extra headroom in the output signal. This extra headroom is to enabled thanks to the generation of a smaller voltage ripple or generation of no voltage ripple at all (so the voltage ripple cancellation with the main output is no longer achieved as in the first mode). Instead, a wide output window, namely a high output voltage, can be achieved as well as high dimming efficiency. In this way, a single driver arrangement is suitable for a large range of applications, reducing the component count to service those different applications. The mode can be selected via updating the firmware of the driving arrangement, or updating a memory in the driver (at the factory, at the distributor, or at the client’s facility). The modes can instead be switched dynamically.

[0024] The main switch mode power converter for example comprises a power factor correction circuit, the secondary switch mode power converter has a maximum output voltage amplitude for the secondary output, and the average voltage amplitude of the driving output in the second mode is higher than that in the first mode.

[0025] The maximum output of the secondary switch mode power converter is for example the rated maximum / peak voltage amplitude due to the rating of its component.

[0026] In the first mode, the secondary switch mode power converter may be adapted to generate the second voltage ripple with an voltage amplitude of at least 80%, preferably at least 90% of the voltage amplitude of the first voltage ripple, and a sum of the first average2024PF80515

[0027] 4 05.12.2025 voltage amplitude and the voltage amplitude of the second voltage ripple is no larger than the maximum output voltage amplitude.

[0028] This provides substantial cancellation of the mains voltage ripple. For example, the secondary switch mode power converter may be adapted to generate the second voltage ripple out of phase, preferably at a 180 degree phase difference, with the first voltage ripple such that the second voltage ripple at least partially cancels the first voltage ripple and smooths the driving output.

[0029] This provides effective cancellation of the mains voltage ripple.

[0030] In the first mode, the main switch mode power converter may be adapted to contribute 80% to 90% of the power of the driving output. Thus, the second switch mode power converter has the main function of voltage ripple cancellation rather than power generation.

[0031] In this case, the main switch mode power converter can be designed to be operated at a high power and high efficiency at the high power and the secondary switch mode power power converter is a low power circuit and operates with high efficiency at the lower power. So the overall efficiency is good.

[0032] The secondary converter is for example adapted, in the second mode, to generate the secondary output with a third voltage ripple with an voltage amplitude less that of the second voltage ripple, and a sum of said second average voltage amplitude and the voltage amplitude of the third voltage ripple is no larger than the maximum output voltage amplitude, or

[0033] the secondary converter is adapted, in the second mode, to generate the secondary output without a voltage ripple and said second average voltage amplitude is no larger than the maximum output voltage amplitude.

[0034] The second average voltage amplitude is thereby larger than the first average value given the same maximum output voltage amplitude because a higher average voltage amplitude can be provided whereas the average voltage amplitude plus the voltage ripple, if any, would still not go beyond the maximum output voltage amplitude.

[0035] In the first mode, the main switch mode power converter may be adapted to sense and regulate the main output to match a reference voltage and the secondary switch mode power converter may be adapted to sense and regulate the current of the driving output to match a reference current.

[0036] The secondary switch mode power converter thereby functions as a voltage ripple remover which is constant-current controlled. This gives a fast response control loop2024PF80515

[0037] 5 05.12.2025 and naturally compensates the load current voltage ripple at heavy load. The main switch mode power converter is a slow response PFC stage wherein the reference voltage is a slow mains frequency voltage rippled voltage.

[0038] In the second mode, the main switch mode power converter may be adapted to sense and regulate its output current to match a reference current and the secondary switch mode power converter is adapted to sense and regulate its output voltage to match a reference voltage, wherein said reference voltage relates to a difference between the voltage of the driving output and a maximum output voltage of the main switch mode power converter.

[0039] The secondary switch mode power converter implements constant voltage control. This gives a fast response control loop so that the output voltage voltage ripple of the secondary switch mode power converter can be controlled to be very low, or near zero. For the same components of the secondary switch mode power converter (with the same voltage derating), the average output voltage can be higher than that in the first mode. Thus, the second mode of the driving arrangement extends the output window to cover more applications.

[0040] The secondary switch mode power converter for example has a first efficiency when operating in the first mode and a second efficiency lower than the first efficiency when operating in the second mode. Thus, the first mode is a high efficiency mode with voltage ripple cancellation. While in the second mode, the benefit of a high output voltage is achieved still with an acceptable trade off of the efficiency of secondary switch mode power converter.

[0041] The driving arrangement may further comprise a mode setting interface to receive a mode selection input, wherein the secondary switch mode power converter is adapted to remain in the first mode or in the second mode during operation according to the mode selection input.

[0042] The mode setting input enables the driving arrangement to be switched between a low voltage ripple mode and a high power mode. The manufacturer, distributor, and even the final customer can set the mode conveniently.

[0043] The secondary switch mode power converter may be adapted to switch between the second mode and the first mode during operation. Thus, the mode of operation may be adapted over time. For example, the secondary switch mode power converter may be adapted to switch between the second mode and the first mode during operation according to a variable voltage of a load driven by the driving output. The voltage of load can be varied due to changing LEDs numbers for dimming down or dimming up the whole lighting circuit.2024PF80515

[0044] 6 05.12.2025 In another example, the secondary switch mode power converter may be adapted to operate in the second mode at start up of the driving arrangement and to transition to the first mode after the voltage of the driving output has decreased after the start up. In this way, startup performance can be improved in harsh environments.

[0045] The main switch mode power converter for example comprises a boost converter and the secondary switch mode power converter for example comprises a buck converter.

[0046] The main switch mode power converter may comprise a series primary inductor having an electromagnetically coupled secondary inductor, wherein the secondary inductor provides an input to the secondary switch mode power converter. Thus, the input to the secondary switch mode power converter is formed by a current that has been generated by inductive coupling to the main switch mode power converter. Using this electromagnetic coupling can losslessly match the normally high voltage in the main switch mode power converter and the normally low voltage in the secondary switch mode power converter. Otherwise a voltage down conversion would be needed with a consequent power loss. The electromagnetic coupling can also provide an isolation function.

[0047] The invention also provides a lighting circuit comprising:

[0048] the driving arrangement as described above; and

[0049] a LED arrangement which comprises the load driven by the driving arrangement.

[0050] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter.

[0051] BRIEF DESCRIPTION OF THE DRAWINGS

[0052] For a better understanding of the invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, in which:

[0053] Fig. 1 shows a driver arrangement; and

[0054] Fig. 2 shows voltage waveforms for the driver arrangement of Figure 1 in two different modes of operation.

[0055] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0056] The invention will be described with reference to the Figures.2024PF80515

[0057] 7 05.12.2025 It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the apparatus, systems and methods, are intended for purposes of illustration only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the apparatus, systems and methods of the present invention will become better understood from the following description, appended claims, and accompanying drawings. It should be understood that the Figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the Figures to indicate the same or similar parts.

[0058] It is a concept of the invention to provide a driving arrangement that can operate in different modes according to customer needs (or according to characteristics of the load being driven). In particular, one mode provides voltage ripple cancellation of the voltage ripple resulting from the powering of the driving arrangement using an AC mains input. Another mode allows voltage ripple to be present in the output but enables a higher driving voltage to be generated, and may also enable more efficient dimming when driving a lighting load. The driving arrangement comprises a main switch mode power converter and a secondary switch mode power converter. The main converter output and the secondary converter output are superposed into a driving output for driving the load. In a first mode of operation of the driving arrangement, the secondary converter is used to at least partially cancel the voltage ripple in the output of the main converter, whereas in a second mode of operation, the secondary converter generates an averagely larger output signal than in the first mode, with a smaller (or no) voltage ripple. The voltage amplitude of the driving output in the second mode is higher than that in the first mode but with less voltage ripple suppression.

[0059] Figure 1 shows a driving arrangement comprising an input IN to receive an AC mains input with a mains frequency voltage ripple.

[0060] A main switch mode power converter 10 comprises a full bridge rectifier D2 to D5 that rectifies the mains input IN. The rectified mains voltage is stored on a capacitor Cl connected between a first high power line HPL1 and a first low power line LPL1. The voltage across the capacitor Cl functions as the input to a converter stage of the main switch mode power converter 10.

[0061] The converter stage comprises a series inductor LI and a series diode DI connected in series at a junction JI. The junction JI connects to the anode of the diode DI. A main switch Ml is connected between the junction JI and the first low power line LPL1.2024PF80515

[0062] 8 05.12.2025 An output capacitor C2 is connected between the cathode of the diode DI and the first low power line LPL1. The inductor, diode and switch are configured as a boost converter.

[0063] The main switch is controlled by a power factor correction circuit 12.

[0064] The main switch mode power converter is effectively a boost converter and converts the AC mains input IN into a main output Vmain across the output capacitor C2 with a first voltage ripple corresponding the mains frequency voltage ripple. The voltage at the high side of the output capacitor is at a first output terminal OUT1.

[0065] A secondary switch mode power converter 20 is adapted to generate a secondary output. The input to the secondary switch mode power converter is present across a second input capacitor C4. The second input capacitor C4 is connected between a second high power line HPL2 and a second low power line LPL2.

[0066] The input to the secondary switch mode power supply is generated by a transformer, formed by the inductor LI an electromagnet cally coupled secondary inductor L3. A current generated in the inductor L3 is delivered through diode D8 to the second input capacitor C4. The transformer LI, L3 lowers the input voltage to the secondary switch mode power converter 20 so that it can operate at higher efficiency and be implemented with lower cost and smaller size. For example, it enables the use of lower voltage derating components. The transformer also performs an isolation function.

[0067] The converter stage of the secondary switch mode power converter comprises a series switch U1 and a series inductor L2 connected in series at a second junction J2. A diode D7 is connected between the second junction J2 and the second low power line LPL2, with the cathode connected to the second junction J2. A second output capacitor C3 is connected between the other end of the inductor L2 and the second low power line LPL2.

[0068] The secondary switch mode power converter converts the voltage across capacitor C4 into a secondary output Vsub across the second output capacitor C3. The voltage at the high side of the second output capacitor is at a second output terminal OUT2. The switch Ul, diode D7 and inductor L2 are configured as a buck converter.

[0069] The series switch Ul is controlled by a second power factor correction circuit 22.

[0070] An output connection superimposes the main output Vmain and the secondary output Vsub into a driving output for driving a load. The load comprises an LED arrangement, represented by diode D6. In particular, the second output terminal OUT2 is connected to the first lower power line LPL1 of the main switch mode power converter 10, so2024PF80515

[0071] 9 05.12.2025 that the two output capacitors C2, C3 are in series between the first output terminal OUT1 and the second low power line LPL2.

[0072] The driving arrangement has first and second modes of operation. To implement the modes of operation the power factor correction circuits 12, 22 each have two modes of operation.

[0073] The main switch mode power converter has a first potential divider Rl, R2 that measures the output voltage Vmain to provide a feedback voltage. The feedback voltage Vs PFC is provided to the first power factor correction circuit 12 (of the main switch mode power converter) through a first switch SI.

[0074] A current sense resistor R3 is in series with the load D6 between the output terminal OUT1 and the second low power line LPL2 (of the secondary switch mode power supply). The voltage across the current sense resistor R3 is provided to the first power factor correction circuit 12 through a second switch S2.

[0075] The secondary switch mode power converter 20 has a second potential divider R9, R10 that measures the output voltage Vsub delivered by the secondary switch mode power converter to provide a feedback voltage Vs_sub. The feedback voltage Vs_sub is provided to the second power factor correction circuit 22 (of the secondary switch mode power supply) through a third switch S3.

[0076] The voltage across the current sensor resistor R3 is also provided to the second power correction circuit 22 through a fourth switch S4.

[0077] First mode

[0078] In a first mode, the first switch SI is closed and the second switch S2 is open, the fourth switch S4 is closed and the third switch S3 is open.

[0079] In this way, in the first mode the main switch mode power converter 10 senses and regulates the main output voltage Vmain, sensed by the feedback voltage Vs, to match a reference voltage, and the secondary switch mode power converter senses and regulate the current of the driving output, sensed by the voltage Is PFC, to match a reference current. Here the reference voltage is not necessarily a constant voltage but could be a mains frequency voltage ripple voltage whose average voltage is regulated to be constant.

[0080] The overall output voltage is sensed, and a certain percentage (for example 80% to 90%) of the overall output voltage is used as the reference voltage for the main switch mode power converter. This is based on a design rule that, in the first mode, the main switch mode power converter is high power and should deliver the majority of the output2024PF80515

[0081] 10 05.12.2025 power, while the secondary converter only generates a small power output for voltage ripple cancellation. To realize a high power factor, the cross frequency is for example designed to be lower than 10Hz and it uses a slow response control loop. The secondary switch mode power converter is constant current controlled based on the sensed load current, using a fast response control loop that naturally compensates the LED current voltage ripple even at heavy load.

[0082] In this first mode of operation, the secondary switch mode power converter 20 is used to generate a secondary output with a first average voltage amplitude and with a second voltage ripple, and it is adapted to at least partially cancel the first voltage ripple. In this first mode of operation, low flicker can be achieved by using the secondary converter for voltage ripple cancellation. The secondary switch mode power converter is constant-current controlled to give a fast response control loop and naturally compensate the load current voltage ripple at heavy load. The constant current control means that the current through the LED load D6 is naturally constant and the second voltage ripple of the secondary switch mode power converter naturally equals the first voltage ripple of the main driver.

[0083] Due to the components’ rating, the secondary switch mode power converter has a maximum output voltage voltage amplitude, and that exceeds the sum of the average voltage amplitude and the voltage amplitude of the voltage ripple of the secondary output.

[0084] The second voltage ripple of the secondary switch mode power converter for example has an voltage amplitude of at least 80%, preferably at least 90% of the voltage amplitude of the first voltage ripple (the rectified mains voltage ripple). The second voltage ripple is preferably out of phase with the first voltage ripple such that the second voltage ripple cancels the first voltage ripple and smooths the driving output. The first mode is thus a voltage ripple removal mode, and the secondary switch mode power converter operates below its maximum output voltage amplitude (determined by the rating of the components of the secondary switch mode power converter). Details can be found in the description below and in Figure 2.

[0085] Second mode

[0086] In a second mode, the first switch SI is open and the second switch S2 is closed, the fourth switch S4 is open and the third switch S3 is closed.

[0087] In the second mode, the main switch mode power converter is adapted to sense and regulate its output current, sensed by the voltage Is PFC, to match a reference current and the secondary switch mode power converter is adapted to sense and regulate its output2024PF80515

[0088] 11 05.12.2025 voltage, sensed by the voltage Vs_sub to match a reference voltage. In this mode, 60% to 100% of the overall output voltage is provided by the main switch mode power converter, and 0% to 40% is provided by the secondary switch mode power converter.

[0089] The reference voltage for the secondary switch mode power converter is based on the difference between the voltage of the driving output and a maximum output voltage of the main switch mode power converter 10. Thus, the main switch power converter is driven to its maximum output and the secondary switch mode power converter provides additional output.

[0090] The secondary switch mode power converter for example has a first efficiency when operating in the first mode and a second efficiency lower than the first efficiency when operating in the second mode. Thus, the first mode is a high efficiency mode with voltage ripple cancellation.

[0091] In this second mode of operation, the secondary switch mode power converter is configured to generate the secondary output with a second average voltage amplitude higher than the first average voltage amplitude and with a third voltage ripple less than the second voltage ripple or without voltage ripple. Thus, the secondary switch mode power converter no longer aims to cancel mains voltage ripple, in that the voltage ripple is less than is used in the first mode, and hence less than is required for voltage ripple cancellation.

[0092] Due to the components’ rating, the secondary switch mode power converter has a maximum output voltage voltage amplitude, and that exceeds the sum of the average voltage amplitude and the voltage amplitude of the voltage ripple of the secondary output. However, compared with the first mode, the voltage amplitude of the (combined) driving output in the second mode is higher than that in the first mode because the average voltage amplitude of the secondary output is higher, but still without making the secondary output (average voltage amplitude plus voltage ripple voltage amplitude) go beyond the maximum voltage amplitude. The secondary switch mode power converter is in this way used to generate a larger output signal but with smaller voltage ripple (so the voltage ripple cancellation with the main output is no longer achieved). A wide output window, namely high output voltage, can then be achieved as well as high dimming efficiency.

[0093] The constant voltage control of the secondary switch mode power converter gives a fast response control loop so that the output voltage voltage ripple of the secondary switch mode power converter can be controlled to be very low, or near zero. For the same components of the secondary switch mode power converter, the average output voltage can2024PF80515

[0094] 12 05.12.2025 be higher than that in the first mode. Thus, the second mode of the driving arrangement extends the output window to cover more applications.

[0095] The output of the secondary switch mode power converter is again below the maximum output voltage amplitude, but has an average voltage amplitude higher than the average voltage amplitude in the first mode. The voltage amplitude of the driving output in the second mode is thus higher than that in the first mode. The sum of the average voltage amplitude in the second mode and the voltage amplitude of the voltage ripple of the secondary converter in the second mode is equals to the maximum output voltage amplitude of the secondary converter.

[0096] Since voltage ripple cancellation is not required in the second mode, the voltage ripple of the output of the secondary converter may be in phase or out of phase with the first voltage ripple.

[0097] If the output of the secondary switch mode power converter has no voltage ripple, then the average voltage amplitude can then be equal to the maximum output voltage amplitude.

[0098] The secondary switch mode power converter in the second mode functions as a voltage booster. The overall output voltage is detected, and the maximum output voltage of the main switch mode power converter is known from its component ratings. The reference output voltage for the secondary switch mode power converter is equal to the load voltage less the maximum output voltage of the main switch power converter. To realize a high power factor, the cross frequency is again designed to be lower than 10Hz and a slow response control loop is used. The secondary switch mode power converter functions as a constant voltage controlled boost circuit. The output voltage of the secondary switch mode power converter is sensed and used to realize constant voltage control to match the reference output voltage of the secondary converter. It uses a fast response control loop and thus the output voltage voltage ripple of the secondary switch mode power converter can be controlled to be very low, or near zero. Thus, for components with the same voltage derating of the secondary switch mode power converter, the average output voltage can be higher than that in the first mode.

[0099] The overall driver arrangement is in this way suitable for a large range of applications, reducing the component count to service those different applications.

[0100] Figure 2 shows voltage waveforms 30 for the first mode and voltage waveforms 40 for the second mode.2024PF80515

[0101] 13 05.12.2025 In the first mode, plot 32 is the voltage output of the main switch mode power converter. Plot 34 is the voltage output of the secondary switch mode power converter, with the same voltage voltage ripple but with opposite phase. Line 36 is the maximum output level of the secondary switch mode power converter. The peak voltage amplitude of the voltage output of the secondary switch mode power converter, being the sum of the average value shown by the lower dotted line and the voltage amplitude of the voltage ripple, should below the maximum output level 36.

[0102] In the second mode, plot 42 is the voltage output of the main switch mode power converter. Plot 44 is the voltage output of the secondary switch mode power converter, with a smaller voltage voltage ripple but a higher average voltage output shown by the middle dotted line, closer to the maximum 36. Indeed, the peak value may correspond to the circuit maximum. It can be seen that the average value of the plot 44 is higher than that of the plot 34.

[0103] The average voltage amplitude of the driving output in the second mode (the sum of waveforms 42 and 44) is thus higher than that in the first mode (the sum of waveforms 32 and 34). The lower voltage ripple of first mode waveform 44 compared to second mode waveform 34 enables a higher average voltage amplitude. Thus, a second average voltage amplitude (for the second mode) of the second switch mode power converter is higher than a first average voltage amplitude (for the first mode). A voltage ripple of the waveform 44 (a third voltage ripple) is less than a voltage ripple of the waveform 34 (second voltage ripple) or the waveform 44 may be without voltage ripple.

[0104] However, a sum of a second average voltage amplitude (i.e. the average voltage amplitude of the secondary switch mode power converter when in the second mode, namely the dotted line of plot 44) and the voltage amplitude of the third voltage ripple (i.e. the voltage ripple in the secondary switch mode power converter output when in the second mode of plot 44) is no larger than the maximum output voltage amplitude as represented by dotted line 36. If plot 44 has no voltage ripple, the second average voltage amplitude may reach the maximum output voltage amplitude of plot 36. It means the second average voltage amplitude (the dotted line of plot 44) is larger than the first average value (the dotted line of plot 34) given the same maximum output voltage amplitude 36.

[0105] Returning to Figure 1, there is additionally shown a mode setting interface 24 to receive a mode selection input MSI. The secondary switch mode power converter 20 is adapted to remain in the first mode or in the second mode during operation according to the2024PF80515

[0106] 14 05.12.2025 mode selection input. The mode seting input MSI enables the driving arrangement to be switched between a low voltage ripple mode and a high voltage mode.

[0107] The mode may be fixed for a particular application of the driving arrangement. For customers or distributors who do not require low voltage ripple, the second mode can be selected for a wide output window range and for customers who need low flicker the first mode can be selected. Thus can help to reduce the overall component count. The mode can be selected via updating the firmware or memory in the driver, at the factory, at the distributor, or at the customer facility.

[0108] However, the secondary switch mode power converter may instead be adapted to switch between the second mode and the first mode during operation. Thus, the mode of operation may be adapted over time. For example, the secondary switch mode power converter may be adapted to switch between the second mode and the first mode during operation according to a variable voltage of the load driven by the driving output. For example, in high brightness state, the number of LEDs (schematically represented by D6) is high and the voltage is high, and the second mode can be activated. In the low brightness state, some LEDs are bypassed and the voltage is low and the first mode can be activated.

[0109] In another example, the secondary switch mode power converter may be adapted to operate in the second mode at start up of the driving arrangement and to transition to the first mode after the driving output has decreased after the start up. In start-up in a cold environment, the second mode may in this way be used to support a high LED forward voltage during cold start. After the forward voltage has dropped, due to the LED becoming warm, the voltage ripple cancellation mode is used. In this way, startup performance can be improved in harsh environments.

[0110] The driver arrangement may also be used to improve light load efficiency. At light load, the main driver can be turned off and the secondary switch mode power converter may operate with high power factor (using a slow response PI control loop to guarantee high power factor, with cross frequency below 10Hz)) to supply the load directly to improve the efficiency. Plot 46 in Figure 2 shows an output voltage that can be delivered by the secondary switch mode power converter alone.

[0111] By adopting driver architecture described above, a single driver can be used in more applications to reduce component count and with dimming efficiency largely improved. A wider output window range is available for high voltage ripple applications with higher dimming efficiency. Low voltage ripple applications can also be provided with higher dimming efficiency.2024PF80515

[0112] 15 05.12.2025 Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.

[0113] The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0114] If the term "adapted to" is used in the claims or description, it is noted the term "adapted to" is intended to be equivalent to the term "configured to". If the term "arrangement" is used in the claims or description, it is noted the term "arrangement" is intended to be equivalent to the term "system", and vice versa.

[0115] Any reference signs in the claims should not be construed as limiting the scope.

Claims

2024PF8051516 05.12.2025 CLAIMS:

1. A driving arrangement comprising:an input (IN) to receive an AC mains input with a mains frequency voltage ripple;a main switch mode power converter (10) adapted to convert the AC mains input into a main output (OUT1) with a first voltage ripple corresponding the mains frequency voltage ripple;a secondary switch mode power converter (20) adapted to generate a secondary output (OUT2) and have a maximum output voltage amplitude for the secondary output; andan output connection to superimpose the main output (OUT1) and the secondary output (OUT2) into a driving output for driving a load,wherein the driving arrangement has first and second modes of operation, wherein:in the first mode of operation, the secondary switch mode power converter (20) is configured to generate the secondary output with a first average voltage amplitude and with a second voltage ripple adapted to at least partially cancel the first voltage ripple, wherein the sum of the first average voltage amplitude and the second voltage ripple is capped by the maximum output voltage amplitude;in the second mode of operation, the secondary switch mode power converter is configured to generate the secondary output wherein reducing a voltage ripple in the secondary output and using an extra headroom away from the maximum output voltage amplitude, provided by reducing the voltage ripple, to increase the average voltage amplitude of the secondary output such that the voltage amplitude of the driving output in the second mode is higher than that in the first mode.

2. The driving arrangement of claim 1, wherein:the main switch mode power converter comprises a power factor correction circuit (12, 22); and2024PF8051517 05.12.2025 the average voltage amplitude of the driving output in the second mode is higher than that in the first mode.

3. The driving arrangement of claim 2, wherein in the first mode the secondary switch mode power converter (20) is adapted to generate the second voltage ripple with an voltage amplitude of at least 80%, preferably at least 90% of the voltage amplitude of the first voltage ripple, and a sum of the first average voltage amplitude and the voltage amplitude of the second voltage ripple is no larger than the maximum output voltage amplitude.

4. The driving arrangement of claim 2 or 3, wherein in the first mode the secondary switch mode power converter (20) is adapted to generate the second voltage ripple out phase, preferably at a 180 degree phase difference, with the first voltage ripple such that the second voltage ripple at least partially cancels the first voltage ripple and smooths the driving output.

5. The driving arrangement of any one of claims 1 to 4, wherein in the first mode the main switch mode power converter (20) is adapted to contribute 80% to 90% of the power of the driving output.

6. The driving arrangement of any one of claims 2 to 5, wherein:the secondary converter is adapted, in the second mode, to generate the secondary output with a third voltage ripple with an voltage amplitude less that of the second voltage ripple, and a sum of said second average voltage amplitude and the voltage amplitude of the third voltage ripple is no larger than the maximum output voltage amplitude; or the secondary converter is adapted to, in the second mode, generate the secondary output without a voltage ripple and said second average voltage amplitude is no larger than the maximum output voltage amplitude,such that the second average voltage amplitude is larger than the first average value given the same maximum output voltage amplitude.

7. The driving arrangement of any one of claims 1 to 6, wherein in the first mode the main switch mode power converter (10) is adapted to sense and regulate the main output2024PF8051518 05.12.2025 (OUT1) to match a reference voltage and the secondary switch mode power converter (20) is adapted to sense and regulate the current of the driving output to match a reference current.

8. The driving arrangement of any one of claims 1 to 7, wherein in the second mode the main switch mode power converter is adapted to sense and regulate its output current to match a reference current and the secondary switch mode power converter is adapted to sense and regulate its output voltage to match a reference voltage, wherein said reference voltage relates to a difference between the voltage of the driving output and a maximum output voltage of the main switch mode power converter.

9. The driving arrangement of any one of claims 1 to 8, wherein the secondary switch mode power converter (20) has a first efficiency when operating in the first mode and a second efficiency lower than the first efficiency when operating in the second mode.

10. The driving arrangement of any one of claims 1 to 9, further comprising a setting interface (24) to receive a mode selection input, wherein the secondary switch mode power converter (20) is adapted to remain in the first mode or in the second mode during operation according to the mode selection input.

11. The driving arrangement of any one of claims 1 to 10, wherein the secondary switch mode power converter (20) is adapted to switch between the second mode and the first mode during operation.

12. The driving arrangement of claim 11, wherein the secondary switch mode power converter is adapted:to switch between the second mode and the first mode during operation according to a variable voltage of a load driven by the driving output; orto operate in the second mode at start up of the driving arrangement and to transition to the first mode after the voltage of the driving output has decreased after the start up.

13. The driving arrangement of any one of claims 1 to 12, wherein the main switch mode power converter (10) comprises a boost converter and the secondary switch mode power converter comprises a buck converter.2024PF8051519 05.12.202514. The driving arrangement of claim 13, wherein the main switch mode power converter comprises a series primary inductor (LI) having an electromagnetically coupled secondary inductor (L3), wherein the secondary inductor (L3) provides an input to the secondary switch mode power converter (20).

15. A lighting circuit comprising:the driving arrangement of any one of claims 1 to 14:a LED arrangement which comprises the load driven by the driving arrangement.

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