A power supply system arranged for driving a load as well as a light emitting diode, led, based lighting device comprising such a power supply system

Abstract

A power supply system arranged for driving a load, said power supply system comprising a rectifier arranged for receiving an AC mains voltage and for converting said AC mains voltage to a DC voltage, a Power Factor Correction, PFC, stage, connected to an output of said rectifier and arranged for improving a power factor of said power supply system, a DC / DC converter, connected to an output of said PFC stage, and arranged for receiving a DC voltage from said PFC stage and for converting said received DC voltage to a DC output for driving said load, wherein said PFC stage comprises an inductor, said inductor comprising a magnetic core, windings wound around said magnetic core such that magnetic flux, induced by current flowing through said windings, circulates through said magnetic core, wherein said magnetic core comprises a first magnetic core part having a first magnetic permeability, a second magnetic core part having a second magnetic permeability, different to said first magnetic permeability, wherein said magnetic flux circulates through said first and second magnetic core parts.

Description

[0001] A power supply system arranged for driving a load as well as a Light Emitting Diode, LED, based lighting device comprising such a power supply system

[0002] TECHNICAL FIELD

[0003] The present disclosure is, generally, related to the field of power supply systems and, more specifically, to a Power Factor Correction, PFC, stage within such power supply systems.

[0004] BACKGROUND

[0005] Power supply systems play an important role in providing the necessary electrical energy to a wide array of electronic devices, and their efficiency and reliability are of importance for the performance of these devices. In the context of Light Emitting Diode, LED, based lighting devices, power supply systems are designed with a multi-stage architecture comprising a rectifier, a Power Factor Correction, PFC, stage, and a DC / DC converter.

[0006] The rectifier is the initial stage in a power supply system and is arranged for converting alternating current, AC, from the mains supply into direct current, DC. LEDs, being inherently DC-driven devices, require such a conversion for proper functionality. Commonly, rectifiers can be classified as either half-wave or full-wave rectifiers, each with their own advantages and disadvantages. The rectification process involves the conversion of the AC signal into a pulsating DC signal, where the negative half-cycles are typically converted to positive half-cycles.

[0007] Following rectification, the DC signal may require further modification to meet the specific voltage and current requirements of the LED load. This task is accomplished by the DC / DC converter, a component that enables the adjustment of voltage levels while maintaining a steady DC output.

[0008] Flyback converters are commonly deployed. The DC / DC converter ensures that the LED load receives the electrical parameters needed for their performance, enhancing energy efficiency and lifetime of these devices.

[0009] While rectification and DC / DC conversion are of importance, an often overlooked yet important aspect of power supply systems is the Power Factor Correction, PFC, stage. Power factor is a measure of how effectively electrical power is converted into useful work output, and it is influenced by the relationship between voltage and current waveforms.

[0010] In conventional systems, power factor can be low due to the non-unity displacement angle between voltage and current, leading to inefficiency of the corresponding driver.

[0011] The PFC stage addresses this issue by actively correcting the power factor, bringing it closer to unity. A unity power factor implies that all the supplied power is utilized for useful work, minimizing wastage. PFC may especially be important in LED based lighting devices, as LEDs may be sensitive to fluctuations in power quality. A PFC stage ensures that the power drawn from the mains supply, for example the grid, is in phase with the voltage, optimizing energy utilization and reducing the impact on the electrical infrastructure.

[0012] Typically, there are two types of PFC: active PFC and passive PFC. Active PFC involves the use of active components such as transistors to actively adjust the input current, dynamically aligning it with the input voltage. This method is highly effective but requires additional circuitry and components. On the other hand, passive PFC employs passive components like capacitors and inductors to achieve power factor correction. While simpler and cost-effective, passive PFC may not be as efficient as active PFC in dynamically adjusting to varying load conditions. Passive solutions may also be heavier and bulkier compared to an active one.

[0013] Integrating a PFC stage into power supply systems for LED loads brings several advantages. It not only improves power factor and energy efficiency but also helps meet regulatory standards for harmonic distortion, contributing to a cleaner and more reliable power grid. Additionally, by reducing reactive power, PFC minimizes voltage drops and losses in distribution networks, enhancing overall power system stability.

[0014] There is always a need for designing a pragmatic passive PFC stage that has at least decent power factor correction capabilities.

[0015] SUMMARY

[0016] It would be advantageous to achieve a power supply system having a Power Factor Correction, PFC, stage that is both effective and pragmatic in its implementation. It would further be advantageous to achieve a Light Emitting Diode, LED, based lighting device comprising such a power supply system. In a first aspect of the present disclosure, there is provided a power supply system arranged for driving a load, said power supply system comprising: a rectifier arranged for receiving an AC mains voltage and for converting said AC mains voltage to a DC voltage; a Power Factor Correction, PFC, stage, connected to an output of said rectifier and arranged for improving the power factor of said power supply system; a DC / DC converter, connected to an output of said PFC stage, and arranged for receiving a DC voltage from said PFC stage and for converting said received DC voltage to a DC output for driving said load.

[0017] The PFC stage comprises an inductor, said inductor comprising: a magnetic core; windings wound around said magnetic core such that magnetic flux, induced by current flowing through said windings, circulates through said magnetic core; wherein said magnetic core comprises: a first magnetic core part having a first magnetic permeability; a second magnetic core part having a second magnetic permeability, different to said first magnetic permeability; wherein said magnetic flux circulates through said first and second magnetic core parts.

[0018] The inventors have found that it may be beneficial to replace a traditional inductor in a PFC stage with an inductor having at least a first magnetic core part and a second magnetic core part.

[0019] When a current flows through the windings, it induces a magnetic flux that circulates through the magnetic core. This magnetic core is made up of two parts: a first part with a certain magnetic permeability and a second part with a different magnetic permeability. The magnetic flux circulates through both these parts.

[0020] By having different magnetic permeabilities in the core, the distribution of the magnetic field can be controlled more precisely. Different permeabilities also allow for better utilization of the magnetic properties of the core material, potentially leading to increased efficiency or performance of the inductor.

[0021] Every magnetic material has a limit to how much magnetic field strength it can support. Once this limit is reached, the material is said to be saturated. In this state, even if the current flowing through the inductor increases, the magnetic field strength does not increase proportionally. When an inductor's core material saturates, the inductor's inductance effectively decreases, which can significantly alter its performance characteristics. It is noted that different magnetic materials have varying saturation points.

[0022] The above can be taken into account when designing the inductor. For higher loads, the second magnetic core part having the second magnetic permeability may, for example, be saturated while the first magnetic core part having the first magnetic permeability, is not yet saturated. In this case, the second magnetic core material may act as an “air gap” as it provides only a small contribution to the inductance of the inductor for those currents.

[0023] The above makes the inductor variable. Variable in the sense that the inductance of the inductor may vary based on the current flowing through the windings.

[0024] The present disclosure may also be viewed as follows. The airgap of the inductor used in the PFC stage may be variable. The inductance may be much higher at low load compared to high load. This is accomplished by using material with different permeability in the core of the inductor.

[0025] A DC / DC converter is a device that transforms one DC voltage level to another, by either stepping up, i.e. boosting, or stepping down, i.e. bucking, the voltage. In scenarios where a regulated current to a load, such as an LED-based load, is of importance, the DC / DC converter may be deployed. LEDs may require a consistent current to function optimally. An excessive current can harm the LEDs, while insufficient current can result in reducing desired brightness or prevent the LED from illuminating altogether.

[0026] By incorporating a DC / DC converter, the power supply system ensures that the LED load receives a steady and regulated current, even when there are variations in the input voltage or shifts in the load's demands. This consistent regulation not only safeguards the LED's lifespan and performance but also introduces the capability to dim the LED.

[0027] By adjusting the output current of the DC / DC converter, the brightness of the LED can be modulated, offering users the flexibility to control the luminosity based on their requirements. Thus, in LED applications, the DC / DC converter serves as an important component, both ensuring the LED's safety and enabling dynamic brightness adjustments through dimming functionalities.

[0028] The DC / DC converter is connected at the output the PFC stage, and therefore receives a more consistent and stable DC input. This is caused by the PFC stage. This allows the DC / DC converter to provide a more reliable and regulated DC output to the load, such as the LED-based load. In accordance with the present disclosure, the power supply system comprises a rectifier. The rectifier is a component for converting alternating current, AC, to direct current, DC. Its primary function is to convert the alternating voltage and current, which periodically changes direction, into a unidirectional flow. In essence, the rectifier ensures that the negative cycles of the AC waveform are flipped or inverted to align with the positive cycles, resulting in a consistent DC output.

[0029] There are various types of rectifiers, with the most common being the diode rectifier. In this configuration, diodes, which are semiconductor devices, allow current to flow in only one direction. As the AC voltage alternates between positive and negative cycles, the diodes ensure that the flow of current always proceeds in the same direction across the load. This process is of importance for the stable operation of the electronic devices provided at the output of the rectifier, as many components require a steady DC supply to function correctly.

[0030] In the context of the PFC stage preceding it, the rectifier further refines the power supply output, ensuring that the subsequent stages, like the DC / DC converter and the connected load, receive a consistent and reliable DC voltage.

[0031] In accordance with the present disclosure, the magnetic core comprises a first magnetic core part and a second magnetic core part. The magnetic core part may have even more magnetic core parts, i.e. a third, a fourth, a fifth, magnetic core part, etc.

[0032] One of the underlying ideas is that the first magnetic core part forms the foundation of the inductor. The windings are provided using the first magnetic core part.

[0033] The second magnetic core part, and optionally the third magnetic core part, the fourth magnetic core part, etc., may be constituted by additional materials placed, or mounted, at an outer end of the first magnetic core part, wherein each of those additional materials has their own magnetic permeability. It may be viewed as a stack of materials having different magnetic permeability.

[0034] In an example, the first magnetic core part has outer ends that face one another.

[0035] The first magnetic core part may be constructed in such a way that it resembles a shape that is not strictly circular, rectangular, square, or anything alike. It can be “almost” each of these shapes. This means that while it bears a resemblance to these geometric forms, it does not perfectly conform to any of them. One feature of this magnetic core part is the presence of a second magnetic core part and, possibly an additional air gap. The presence of the second magnetic core part indicates that the ends of the first magnetic core part do not meet seamlessly, instead, there's a space between them, that is fully, or partially, filled with the second magnetic core part. As mentioned above, this design feature of the inductor has implications for the inductor's magnetic properties, affecting factors such as its inductance and performance - especially in relation to the current flowing through the inductor.

[0036] In another example, at least one of said outer ends of said first magnetic core part is connected to said second magnetic core part.

[0037] In another example, both of said outer ends of said first magnetic core part are connected to said second magnetic core part.

[0038] In this example, no additional air gap is realized such that the magnetic flux circulates only through the first and second magnetic core parts.

[0039] In yet another example, a shape of said first magnetic core part resembles substantially any of: a rectangle, a square, a hexagon, a octagon, a pentagon, a circle, a triangle.

[0040] It is noted that the first magnetic core part may comprise materials that are traditionally used for constructing an inductor. In fact, an off-the-shelf inductor having an air gap may be used as a starting point for obtaining an inductor in accordance with the present disclosure. The air gap may be, at least partially, filled with a different magnetic material, or with different magnetic materials. This creates a so-called variable inductor.

[0041] The above would entail that the windings are provided on the first magnetic core part. The second magnetic core part may be relatively small, i.e. may constitute of a single plate or the like, to fill the air gap.

[0042] In yet another example, the first magnetic permeability ranges anywhere from 1000 - 5000 and / or the second magnetic permeability ranges anywhere from 10 - 500. It is noted that the first magnetic permeability is typically higher compared to the second magnetic permeability.

[0043] The first magnetic permeability may thus have a high permeability, i.e. in the range of 1000 - 5000. This first magnetic permeability is high such that the magnetic field H in the corresponding material is close to zero. The magnetic field H is then basically condensed in the other materials, or the air gap, that constitutes the core. The air gap may be filled, fully or partially, with another material having a second magnetic permeability between the 1 and 5000. This allows to control how the self-inductance of the inductor depends on the current flowing through the inductor. Magnetic permeability may be considered as a measure of how easily a material can be magnetized. Specifically, it typically quantifies the relationship between magnetic flux density and the magnetic field intensity in a material. Materials with high permeability can be easily magnetized by an external magnetic field, while those with low permeability are less responsive to such fields.

[0044] For instance, the first material, i.e. corresponding to the first magnetic permeability, might exhibit a magnetic permeability that falls within the range of 1000 to 5000, indicating moderate magnetic responsiveness. In contrast, the second material, corresponding to the second magnetic permeability, has a higher permeability ranging from 500 to 5000, signifying a much stronger magnetic response.

[0045] In another example, the first magnetic permeability is at least 2 times greater than said second magnetic permeability, preferably at least 5 times greater.

[0046] In yet another example, the second magnetic core part comprises a layer of ferrite mounted to at least one of said two outer ends of said first magnetic core part.

[0047] The second magnetic core part may be provided as a hardened gel, wherein the hardened gel comprises magnetic core material particles.

[0048] In a further example of the present disclosure, the PFC stage comprises only said inductor. That would mean that the PFC stage does not comprise other components like switches or the like.

[0049] The inventors have found that it may be beneficial if the PFC stage is only comprised by the inductor in accordance with the present disclosure.

[0050] This might feel counterintuitive as the power factor obtained by such a realization is reduced compared to traditional PFC stages. The variable inductor may still provide for sufficient power factor correction for the power supply system.

[0051] The benefit hereof is that the implementation of the PFC stage is much less complex. The trade off is thus related to the complexity of the implementation of the PFC stage and the actual power factor correction obtained by the PFC stage.

[0052] It was found that using just a (variable) inductor in accordance with the present disclosure is sufficient for obtaining a power factor that is good enough.

[0053] In another example, the system is arranged for driving a Light Emitting Diode, LED, based load.

[0054] In a second aspect of the present disclosure, there is provided a Light Emitting Diode, LED, based lighting device comprises a power supply system in accordance with any of the previous examples. It is noted that the advantages as explained with reference to the first aspect of the present disclosure, being the power supply system, also correspond to second aspect of the present disclosure, being the LED based lighting device.

[0055] In another example, the LED based lighting device comprises: a dimmer unit arranged for dimming said LED load.

[0056] The dimmer unit may thus be arranged to regulate the total current provided to the LED load. The current provided to the LED load may be controlled using Pulse Width Modulation, PWM. The frequency of the PWM may be chosen high enough such that the frequency is out of the spectrum of the visual eye.

[0057] In yet another example, the DC / DC converter is any of a boost converter, a buck converter, a buck-boost converter, a flyback converter.

[0058] The present disclosure is described in conjunction with the appended figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

[0059] In the appended figures, similar components and / or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label.

[0060] The above and other aspects of the disclosure will be apparent from and elucidated with reference to the examples described hereinafter.

[0061] BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Fig. 1 discloses an example of a power supply system in accordance with the present disclosure;

[0063] Fig. 2 disclose an example of an inductor in a Power Factor Correction, PFC, stage of a power supply system in accordance with the present disclosure;

[0064] Fig. 3 discloses another example of an inductor in a Power Factor Correction, PFC, stage of a power supply system in accordance with the present disclosure. DETAILED DESCRIPTION

[0065] It is noted that in the description of the figures, same reference numerals refer to the same or similar components performing a same or essentially similar function.

[0066] A more detailed description is made with reference to particular examples, some of which are illustrated in the appended drawings, such that the manner in which the features of the present disclosure may be understood in more detail. It is noted that the drawings only illustrate typical examples and are therefore not to be considered to limit the scope of the subject matter of the embodiments. The drawings are incorporated for facilitating an understanding of the disclosure and are thus not necessarily drawn to scale. Advantages of the subject matter as claimed will become apparent to those skilled in the art upon reading the description in conjunction with the accompanying drawings.

[0067] The ensuing description above provides preferred exemplary embodiment s) only, and is not intended to limit the scope, applicability or configuration of the disclosure. Rather, the ensuing description of the preferred exemplary embodiment(s) will provide those skilled in the art with an enabling description for implementing a preferred exemplary embodiment of the disclosure, it being understood that various changes may be made in the function and arrangement of elements, including combinations of features from different embodiments, without departing from the scope of the disclosure.

[0068] Unless the context clearly requires otherwise, throughout the description and the embodiments, the words "comprise," "comprising," and the like are to be construed in an inclusive sense, as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to." As used herein, the terms "connected," "coupled," or any variant thereof means any connection or coupling, either direct or indirect, between two or more elements; the coupling or connection between the elements can be physical, logical, electromagnetic, or a combination thereof. Additionally, the words "herein," "above," "below," and words of similar import, when used in this application, refer to this application as a whole and not to any particular portions of this application. Where the context permits, words in the Detailed Description using the singular or plural number may also include the plural or singular number respectively. The word "or," in reference to a list of two or more items, covers all of the following interpretations of the word: any of the items in the list, all of the items in the list, and any combination of the items in the list.

[0069] These and other changes can be made to the technology in light of the following detailed description. While the description describes certain examples of the technology, and describes the best mode contemplated, no matter how detailed the description appears, the technology can be practiced in many ways. Details of the system may vary considerably in its specific implementation, while still being encompassed by the technology disclosed herein. As noted above, particular terminology used when describing certain features or aspects of the technology should not be taken to imply that the terminology is being redefined herein to be restricted to any specific characteristics, features, or aspects of the technology with which that terminology is associated. In general, the terms used in the following embodiments should not be construed to limit the technology to the specific examples disclosed in the specification, unless the Detailed Description section explicitly defines such terms. Accordingly, the actual scope of the technology encompasses not only the disclosed examples, but also all equivalent ways of practicing or implementing the technology under the embodiments.

[0070] Fig. 1 discloses an example 1 of a power supply system in accordance with the present disclosure.

[0071] The power supply system comprises a full-wave rectifier 2. The full-wave rectifier 2 is arranged to receive an Alternating Current, AC, mains, for example 230Vac or 1 lOVac or something alike.

[0072] A full-wave rectifier is an electrical circuit used to convert alternating current, AC, into direct current, DC. Unlike half-wave rectifiers, which utilize only one half-cycle of the AC input, a full-wave rectifier takes advantage of both the positive and negative halves of the AC waveform. This results in a more continuous and smoother DC output.

[0073] The basic configuration of a full-wave rectifier typically employs four diodes arranged in a bridge configuration, often referred to as a "bridge rectifier." In this setup, two diodes conduct during the positive half-cycle of the AC input, allowing current to flow in one direction through the load. Similarly, the other two diodes become forward-biased during the negative half-cycle, ensuring that current continues to flow in the same direction through the load. As a result, the output voltage across the load is a pulsating DC waveform that effectively utilizes both halves of the AC cycle.

[0074] The PFC stage 3 is connected to the output of the full-wave rectifier. The PFC stage is arranged to provide power factor correction such that the amount of reactive power drawn from the AC grid is reduced as much as possible.

[0075] In a specific example of the present disclosure, the PFC stage comprises of merely the variable inductor as discussed throughout this disclosure. This makes the implementation of the PFC stage less complex and, at the same time, provides for sufficient power factor correction. Of course, at the output of the full-wave rectifier, a buffer capacitor may be placed, just as at the output of the PFC stage.

[0076] A DC / DC converter 4 is provided at the output of the PFC stage. The DC / DC converter may comprise a buck converter or anything alike. Finally, the DC load 5 may be connected to the output of the DC / DC converter. The DC load may, for example, be a Light Emitting Diode, LED, based load.

[0077] Fig. 2 discloses an inductor 11 in accordance with the present disclosure. The PFC stage comprises such an inductor, wherein said inductor comprises: a magnetic core 13, 14; windings 12 wound around said magnetic core such that magnetic flux, induced by current flowing through said windings, circulates through said magnetic core.

[0078] In this particular case, the magnetic core comprises two different magnetic core parts 13, 14. The first magnetic core part 13 constitutes the majority of the magnetic core. The first magnetic core part has a first magnetic permeability.

[0079] On one of the two end faces of the first magnetic core part is a second magnetic core part 14 mounted. The second magnetic core part has a different magnetic permeability compared to the first magnetic permeability.

[0080] In the situation shown in figure 2, an additional airgap is present between the other end face of the first magnetic core part and an end face of the second magnetic core part.

[0081] This is different from the embodiment 21 shown in figure 3, wherein no air gap is present between the different magnetic core parts.

[0082] It should be noted that the above-mentioned examples illustrate rather than limit the idea, and that those skilled in the art will be able to design many alternative examples without departing from the scope of the appended claims. The word “comprising” does not exclude the presence of elements or steps other than those listed in a claim, “a” or “an” does not exclude a plurality, and a single processor or other unit may fulfil the functions of several units recited in the claims.

[0083] Any reference signs in the claims shall not be construed so as to limit their scope.

Claims

CLAIMS:

1. A power supply system (1) arranged for driving a load (5), said power supply system (1) comprising: a rectifier (2) arranged for receiving an AC mains voltage and for converting said AC mains voltage to a DC voltage; a Power Factor Correction, PFC, stage (3), connected to an output of said rectifier (2) and arranged for improving a power factor of said power supply system (1); a DC / DC converter (4), connected to an output of said PFC stage (3), and arranged for receiving a DC voltage from said PFC stage (3) and for converting said received DC voltage to a DC output for driving said load (5), wherein said PFC stage (3) comprises an inductor (11), said inductor (11) comprising: a magnetic core (13, 14); windings (12) wound around said magnetic core (13, 14) such that magnetic flux, induced by current flowing through said windings (12), circulates through said magnetic core (13, 14); wherein said magnetic core (13, 14) comprises: a first magnetic core part (13) having a first magnetic permeability and outer ends that face one another, wherein said at least one of said outer ends of said first magnetic core part (13) is connected to a second magnetic core part (14); the second magnetic core part (14) having a second magnetic permeability, different to said first magnetic permeability; wherein said magnetic flux circulates through said first and second magnetic core parts (13, 14).

2. A power supply system (1) in accordance with claim 1, wherein both said outer ends of said first magnetic core part (13) are connected to said second magnetic core part (14).

3. A power supply system (1) in accordance with any of the previous claims, wherein a shape of said first magnetic core part (13) resembles substantially any of: a rectangle, a square, a hexagon, an octagon, a pentagon, a circle, a triangle.

4. A power supply system (1) in accordance with any of the previous claims, wherein said first magnetic permeability ranges anywhere from 1000 - 5000.

5. A power supply system (1) in accordance with any of the previous claims 1 to 3, wherein said second magnetic permeability ranges anywhere from 10 - 500.

6. A power supply system (1) in accordance with any of the previous claims, wherein said first magnetic permeability is at least 2 times greater than said second magnetic permeability.

7. A power supply system (1) in accordance with any of the previous claims, wherein said second magnetic core part (14) comprises a layer of ferrite mounted to at least one of said two outer ends of said first magnetic core part (13).

8. A power supply system (1) in accordance with any of the previous claims, wherein said second magnetic core part (14) comprises a hardened gel, said gel comprising magnetic core material particles.

9. A power supply system (1) in accordance with any of the previous claims, wherein said PFC stage (3) comprises only said inductor (11).

10. A power supply system (1) in accordance with any of the previous claims, wherein said power supply system (1) is arranged for driving a Light Emitting Diode, LED, based load.

11. A Light Emitting Diode, LED, based lighting device comprises a power supply system (1) in accordance with any of the previous claims.

12. An LED based lighting device in accordance with claim 11, wherein said LED based lighting device comprises:a dimmer unit arranged for dimming said LED load.

13. An LED based lighting device in accordance with any of the claims 11 - 12, wherein said DC / DC converter (4) is any of: - a boost converter, a buck converter, a buck-boost converter, a flyback converter.

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