Power supply systems for driving loads and LED-based lighting devices including such power supply systems.

Abstract

A power supply system for driving a load includes: a rectifier arranged to receive an AC mains voltage and convert it into a DC voltage; a power factor correction (PFC) stage connected to the output of the rectifier and arranged to improve the power factor of the power supply system; and a DC / DC converter connected to the output of the PFC stage and arranged to receive the DC voltage from the PFC stage and convert the received DC voltage into a DC output for driving the load. The PFC stage includes an inductor comprising: a magnetic core; and a winding wound around the magnetic core such that magnetic flux induced by a current flowing through the winding circulates through the magnetic core. The magnetic core includes: a first core portion having a first permeability; and a second core portion having a second permeability different from the first permeability. The magnetic flux circulates through both the first and second core portions.

Description

Technical Field

[0001] This disclosure relates generally to the field of power systems, and more specifically to power factor correction (PFC) stages in such power systems. Background Technology

[0002] Power supply systems play a vital role in providing the necessary electrical energy to various electronic devices, and their efficiency and reliability are crucial to the performance of these devices. In LED-based lighting installations, the power supply system is designed as a multi-stage architecture, including a rectifier, a power factor correction (PFC) stage, and a DC / DC converter.

[0003] A rectifier is the initial stage in a power supply system, used to convert alternating current (AC) from the mains supply into direct current (DC). LEDs are inherently DC-driven devices, so this conversion is necessary for them to function properly. Rectifiers are typically classified as half-wave rectifiers and full-wave rectifiers, each with its own advantages and disadvantages. The rectification process involves converting an AC signal into a pulsating DC signal, where the negative half-cycle is typically converted to the positive half-cycle.

[0004] After rectification, the DC signal may need further modification to meet the specific voltage and current requirements of the LED load. This task is accomplished by a DC / DC converter, a component capable of adjusting the voltage level while maintaining a stable DC output.

[0005] Flyback converters are a commonly used type. DC / DC converters ensure that LED loads receive the electrical parameters required for their performance, thereby improving the energy efficiency and lifespan of these devices.

[0006] While rectification and DC / DC conversion are important, a crucial yet often overlooked aspect of power systems is the power factor correction (PFC) stage. The power factor, a measure of the efficiency with which electrical energy is converted into usable work output, is influenced by the relationship between voltage and current waveforms.

[0007] In traditional systems, the power factor may be low due to the non-unit displacement angle between voltage and current, resulting in low efficiency of the corresponding driver.

[0008] PFC (Power Factor Correction) levels address this issue by actively correcting the power factor, bringing it close to unity power factor. Unity power factor means that all electricity supplied is used for useful work, thus minimizing waste. PFC can be particularly important in LED-based lighting installations, as LEDs can be sensitive to fluctuations in power quality. PFC levels ensure that the power drawn from the grid (e.g., the mains power supply) is in phase with the voltage, thereby optimizing energy use and reducing the impact on power infrastructure.

[0009] Generally, there are two types of PFC: active PFC and passive PFC. Active PFC uses active components such as transistors to actively adjust the input current to dynamically align it with the input voltage. This method is very effective but requires additional circuitry and components. Passive PFC, on the other hand, uses passive components such as capacitors and inductors to achieve power factor correction. While simpler and more cost-effective, passive PFC may be less efficient than active PFC in dynamically adapting to changing load conditions. Passive solutions may also be heavier and bulkier than active solutions.

[0010] Integrating a power factor control (PFC) stage into power systems for LED loads offers several advantages. It not only improves power factor and energy efficiency but also helps meet regulatory standards regarding harmonic distortion, contributing to a cleaner and more reliable power grid. Furthermore, by reducing reactive power, PFC minimizes voltage drop and losses in the distribution network, enhancing the stability of the entire power system.

[0011] There is always a need to design a practical passive PFC stage that has at least good power factor correction capability. Summary of the Invention

[0012] Advantageously, it is possible to realize a power system in which the power factor correction (PFC) stage is both effective and practical in its implementation. Further advantageously, it is possible to realize a light-emitting diode (LED) based lighting device incorporating such a power system.

[0013] In a first aspect of this disclosure, a power supply system for driving a load is provided, the power supply system comprising:

[0014] A rectifier, which is arranged to receive AC mains voltage and convert AC mains voltage into DC voltage;

[0015] A power factor correction (PFC) stage is connected to the output of the rectifier and is arranged to improve the power factor of the power system.

[0016] A DC / DC converter is connected to the output of the PFC stage and is arranged to receive DC voltage from the PFC stage and convert the received DC voltage into a DC output for driving the load.

[0017] The PFC stage includes inductors, which include:

[0018] magnetic core;

[0019] The winding is wound around the magnetic core so that the magnetic flux induced by the current flowing through the winding circulates through the magnetic core.

[0020] The magnetic core includes:

[0021] The first magnetic core portion has a first magnetic permeability;

[0022] The second magnetic core portion has a second magnetic permeability that is different from the first magnetic permeability;

[0023] The magnetic flux circulates through the first and second magnetic core sections.

[0024] The inventors have discovered that it can be beneficial to replace the conventional inductor in the PFC stage with an inductor having at least a first core portion and a second core portion.

[0025] When current flows through the winding, it induces a magnetic flux that circulates through the core. The core consists of two parts: a first part with a specific permeability and a second part with a different permeability. The magnetic flux circulates through these two parts.

[0026] By using different permeabilities within the magnetic 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 improving the efficiency or performance of the inductor.

[0027] Every magnetic material has a limit to the 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 will not increase proportionally.

[0028] When the core material of an inductor becomes saturated, the inductance of the inductor decreases significantly, which can substantially alter its performance characteristics. It is important to note that different magnetic materials have different saturation points.

[0029] The above situation can be taken into account when designing inductors. For example, for higher loads, the second core portion with the second permeability may saturate, while the first core portion with the first permeability is not yet saturated. In this case, the second core material can act as an "air gap" because it contributes very little to the inductor's inductance for these currents.

[0030] The above makes the inductor variable. Variable means that the inductance of the inductor can change according to the current flowing through the winding.

[0031] This disclosure can also be understood as follows: The air gap of the inductor used in the PFC stage can be variable. The inductance may be much higher under low loads than under high loads. This is achieved by using materials with different permeabilities in the inductor core.

[0032] A DC / DC converter is a device that converts one DC voltage level to another, which can be achieved through boost (i.e., step-up) or buck (i.e., step-down) conversion. DC / DC converters are used in scenarios where a regulated current needs to be supplied to a load, such as an LED-based load. LEDs may require a consistent current to operate optimally. Excessive current can damage the LED, while insufficient current will result in reduced brightness or failure to fully illuminate the LED.

[0033] By incorporating a DC / DC converter, the power system ensures that the LED load receives a stable and regulated current even when the input voltage varies or the load demand changes. This stable regulation not only protects the LED's lifespan and performance but also introduces the ability to dim the LED.

[0034] The brightness of an LED can be adjusted by changing the output current of the DC / DC converter, providing users with the flexibility to control brightness according to their needs. Therefore, the DC / DC converter is an important component in LED applications, ensuring LED safety while enabling dynamic brightness adjustment through dimming functionality.

[0035] The DC / DC converter is connected to the output of the PFC stage, thus receiving a more consistent and stable DC input. This is due to the function of the PFC stage. This allows the DC / DC converter to provide a more reliable and stable DC output to loads such as LED-based loads.

[0036] According to this disclosure, the power supply system includes a rectifier. A rectifier is a component that converts alternating current (AC) into direct current (DC). Its primary function is to convert alternating voltage and current that periodically change direction into unidirectional flow. Essentially, a rectifier ensures that the negative half-cycle of the AC waveform is flipped or reversed to align with the positive half-cycle, thereby producing a consistent DC output.

[0037] There are various types of rectifiers, the most common being diode rectifiers. In this configuration, the diode, as a semiconductor device, allows current to flow in only one direction. As the AC voltage alternates between positive and negative half-cycles, the diode ensures that the current flowing through the load always flows in the same direction. This process is crucial for the stable operation of electronic devices connected to the rectifier output, as many components require a stable DC power supply to function properly.

[0038] With the PFC stage preceding the rectifier, the power output is further improved, ensuring that subsequent stages (such as DC / DC converters and connected loads) receive a consistent and reliable DC voltage.

[0039] According to this disclosure, the magnetic core includes a first magnetic core portion and a second magnetic core portion. The magnetic core portion may even have more magnetic core portions, such as a third, fourth, fifth magnetic core portion, etc.

[0040] One of the basic ideas is that the first magnetic core section forms the basis of the inductor. The windings are set up using the first magnetic core section.

[0041] The second magnetic core portion, and optionally the third and fourth magnetic core portions, can be composed of additional materials placed or mounted on the outer end of the first magnetic core portion, wherein each additional material has its own magnetic permeability. This can be viewed as a stack of materials with different magnetic permeabilities.

[0042] In one example, the first core portion has outer ends facing each other.

[0043] The first core portion can be constructed in a shape that is not strictly circular, rectangular, square, or any other shape. It can be "almost" every one of these shapes. This means that while it resembles these geometries, it does not perfectly conform to any of them. A characteristic of this core portion is the presence of a second core portion and possibly additional air gaps.

[0044] The presence of the second core portion indicates that the ends of the first core portion are not seamlessly joined. Alternatively, a gap exists between them, which is wholly or partially filled by the second core portion. As mentioned above, this design feature of the inductor affects its magnetic properties, influencing factors such as its inductance and performance, particularly those related to the current flowing through the inductor.

[0045] In another example, at least one of the outer ends of the first magnetic core portion is connected to the second magnetic core portion.

[0046] In another example, both outer ends of the first magnetic core portion are connected to the second magnetic core portion.

[0047] In this example, no additional air gap is implemented, so that the magnetic flux circulates only through the first and second core sections.

[0048] In yet another example, the shape of the first magnetic core portion is substantially similar to any of the following shapes:

[0049] Rectangle, square, hexagon, octagon, pentagon, circle, triangle.

[0050] It should be noted that the first magnetic core portion may include materials conventionally used for constructing inductors. In fact, an off-the-shelf inductor with an air gap can be used as a starting point for obtaining the inductor according to this disclosure. The air gap may be at least partially filled with different magnetic materials or multiple different magnetic materials. This results in a so-called variable inductor.

[0051] This means that the winding is located on the first core section. The second core section may be relatively small, consisting of a single plate or similar material, to fill the air gap.

[0052] In yet another example, the first permeability is any value between 1000 and 5000 and / or the second permeability is any value between 10 and 500. It should be noted that the first permeability is typically higher than the second permeability.

[0053] Therefore, the first permeability can be high, i.e., in the range of 1000-5000. The first permeability is so high that the magnetic field H in the corresponding material is close to zero. The magnetic field H is then essentially concentrated in the other materials constituting the core or in the air gap. The air gap can be filled entirely or partially with another material having a second permeability between 1 and 5000. This allows control over how the inductor's self-inductance depends on the current flowing through it.

[0054] Magnetic permeability can be considered an indicator of how easily a material can be magnetized. Specifically, it typically quantifies the relationship between magnetic flux density and magnetic field strength within a material. Materials with high magnetic permeability are easily magnetized by external magnetic fields, while materials with low magnetic permeability respond less strongly to such fields.

[0055] For example, the first material, corresponding to the first permeability, might exhibit a permeability falling within the range of 1000 to 5000, indicating moderate magnetic responsiveness. In contrast, the second material, corresponding to the second permeability, has a higher permeability, ranging from 500 to 5000, indicating a stronger magnetic response.

[0056] In another example, the first permeability is at least twice the second permeability, preferably at least five times.

[0057] In yet another example, the second core portion includes a ferrite layer mounted on at least one of the two outer ends of the first core portion.

[0058] The second magnetic core portion can be provided as a hardening gel, wherein the hardening gel contains magnetic core material particles.

[0059] In a further example of this disclosure, the PFC stage includes only an inductor. This means that the PFC stage does not include other components such as switches.

[0060] The inventors have discovered that it may be advantageous if the PFC stage consists solely of inductors according to this disclosure.

[0061] This may seem counterintuitive, as the power factor achieved through this implementation is lower compared to a traditional PFC stage. A variable inductor can still provide sufficient power factor correction for the power system.

[0062] The advantage of this approach is that it significantly reduces the implementation complexity of the PFC stage. Therefore, the trade-off lies between the implementation complexity of the PFC stage and the actual power factor correction achieved by the PFC stage.

[0063] It has been found that using only the (variable) inductor according to this disclosure is sufficient to obtain a sufficiently good power factor.

[0064] In another example, the system is configured to drive a light-emitting diode (LED) based load.

[0065] In a second aspect of this disclosure, a light-emitting diode (LED) based lighting device is provided, which includes a power supply system according to any of the foregoing examples.

[0066] It should be noted that the advantages explained with reference to the first aspect of this disclosure (i.e., the power supply system) also correspond to the second aspect of this disclosure (i.e., the LED-based lighting device).

[0067] In another example, an LED-based lighting device includes:

[0068] A dimming unit is arranged to dim the LED load.

[0069] Therefore, a dimming unit can be arranged to regulate the total current supplied to the LED load. The current supplied to the LED load can be controlled using pulse width modulation (PWM). The frequency of the PWM can be selected high enough that it exceeds the range of the visible spectrum.

[0070] In yet another example, the DC / DC converter is any of the following: boost converter, buck converter, buck-boost converter, flyback converter.

[0071] This disclosure is described in conjunction with the accompanying drawings. It should be emphasized that, in accordance with industry standard practice, the various features are not drawn to scale. In fact, for clarity of discussion, the dimensions of the various features may be arbitrarily increased or decreased.

[0072] In the accompanying drawings, similar components and / or features may have the same reference numerals. Furthermore, various components of the same type can be distinguished by adding a dash after the reference numeral and a second numeral to differentiate similar components. If only the first reference numeral is used in the specification, the description applies to any similar components having the same first reference numeral, regardless of the second reference numeral.

[0073] The foregoing and other aspects of this disclosure will be apparent and illustrated from the examples described below. Attached Figure Description

[0074] Figure 1 An example of a power supply system according to this disclosure is shown;

[0075] Figure 2 An example of an inductor in the power factor correction (PFC) stage of a power supply system according to this disclosure is shown;

[0076] Figure 3 Another example of an inductor in a power factor correction (PFC) stage of a power supply system according to this disclosure is shown. Detailed Implementation

[0077] It should be noted that in the description of the accompanying drawings, the same reference numerals refer to the same or similar components that perform the same or substantially the same function.

[0078] The description will be more detailed with reference to specific examples, some of which are illustrated in the accompanying drawings, to provide a more detailed understanding of the features of this disclosure. It should be noted that the drawings show only typical examples and should not be construed as limiting the scope of the subject matter of the embodiments. The drawings are included for the purpose of facilitating understanding of this disclosure and are not necessarily drawn to scale. The advantages of the claimed subject matter will become apparent to those skilled in the art upon reading the specification in conjunction with the accompanying drawings.

[0079] The following description provides only preferred exemplary embodiments and is not intended to limit the scope, applicability, or configuration of this disclosure. Rather, the following description of preferred exemplary embodiments will provide a illustrative description for those skilled in the art to implement preferred exemplary embodiments of this disclosure. It should be understood that various changes may be made to the function and arrangement of elements, including combinations of features from different embodiments, without departing from the scope of this disclosure.

[0080] Unless the context explicitly requires it, throughout the specification and embodiments, the words “comprise,” “comprising,” etc., should be interpreted in an inclusive sense, rather than an exclusive or exhaustive one; that is, meaning “including but not limited to.” As used herein, the terms “connected,” “coupled,” or any variation thereof mean any connection or coupling between two or more elements, whether direct or indirect; the coupling or connection between elements can be physical, logical, electromagnetic, or a combination thereof. Furthermore, when used in this application, the words “herein,” “above,” “below,” and words with similar meanings refer to the entire application and not any particular part of it. Where the context permits, words used in the detailed description in singular or plural forms may also include either the plural or singular forms, respectively. When referring to a list of two or more items, the word “or” covers all of the following interpretations: any item in the list, all items in the list, and any combination of items in the list.

[0081] These and other changes can be made to the technology in light of the following detailed description. While this description depicts certain examples of the technology and describes the expected best practices, the technology can be practiced in many ways, no matter how detailed the description may be. The details of the system may vary considerably in its specific implementation, but are still covered by the technology disclosed herein. As noted above, specific terms used when describing certain features or aspects of the technology should not be construed as implying that the term is being redefined herein to limit any particular characteristic, feature, or aspect of the technology associated with that term. Generally, the terminology used in the following embodiments should not be construed as limiting the technology to the specific examples disclosed in the specification, unless such terms are explicitly defined in the Detailed Description section. Therefore, the actual scope of the technology includes not only the disclosed examples but also all equivalent ways in which the technology is practiced or implemented under the embodiments.

[0082] Figure 1 Example 1 of a power supply system according to this disclosure is shown.

[0083] The power system includes a full-wave rectifier 2. The full-wave rectifier 2 is arranged to receive AC mains power, such as 230Vac or 110Vac or a similar voltage.

[0084] A full-wave rectifier is a circuit used to convert alternating current (AC) to direct current (DC). Unlike a half-wave rectifier, which utilizes only half a cycle of the AC input, a full-wave rectifier utilizes both the positive and negative half-cycles of the AC waveform. This results in a more continuous and smoother DC output.

[0085] The basic configuration of a full-wave rectifier typically uses four diodes arranged in a bridge configuration, commonly 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 through the load in one direction. Similarly, the other two diodes become forward biased during the negative half-cycle, ensuring that current continues to flow through the load in the same direction. As a result, the output voltage across the load is a pulsating DC waveform, effectively utilizing both half-cycles of the AC cycle.

[0086] PFC stage 3 is connected to the output of the full-wave rectifier. The PFC stage is arranged to provide power factor correction to minimize the amount of reactive power drawn from the AC grid.

[0087] In a specific example of this disclosure, the PFC stage consists only of a variable inductor discussed throughout this disclosure. This makes the implementation of the PFC stage less complex while providing sufficient power factor correction.

[0088] Of course, a buffer capacitor can be placed at the output of the full-wave rectifier, just like at the output of the PFC stage.

[0089] DC / DC converter 4 is located at the output of the PFC stage. The DC / DC converter may include a buck converter or a similar device. Finally, a DC load 5 may be connected to the output of the DC / DC converter. The DC load may be, for example, a light-emitting diode (LED) based load.

[0090] Figure 2 An inductor 11 according to this disclosure is shown. A PFC stage includes such an inductor, wherein the inductor comprises:

[0091] Magnetic cores 13 and 14;

[0092] A winding 12 is wound around the magnetic core such that the magnetic flux induced by the current flowing through the winding circulates through the magnetic core.

[0093] In this specific case, the magnetic core comprises two distinct core portions 13 and 14. The first core portion 13 constitutes the majority of the magnetic core. The first core portion has a first permeability.

[0094] A second magnetic core portion 14 is mounted on one of the two end faces of the first magnetic core portion. The second magnetic core portion has a permeability different from that of the first magnetic core portion.

[0095] exist Figure 2 In the case shown, there is an additional air gap between the other end face of the first magnetic core portion and one end face of the second magnetic core portion.

[0096] This is Figure 3 The example shown is different from embodiment 21. Figure 3There is no air gap between the different magnetic core sections.

[0097] It should be noted that the above examples are illustrative and not limiting of the concept, and those skilled in the art will be able to devise many alternative examples without departing from the scope of the appended claims. The word "comprising" does not exclude the presence of other elements or steps besides those listed in the claims, "a" and "an" do not exclude a plurality, and a single processor or other unit may perform the functions of several units recited in the claims.

[0098] Any reference numerals in the claims should not be construed as limiting their scope.

Claims

1. A power supply system (1) arranged for driving a load (5), the power supply system (1) comprising: A rectifier (2) is arranged to receive AC mains voltage and convert the AC mains voltage into DC voltage; A power factor correction (PFC) stage (3) is connected to the output of the rectifier (2) and is arranged to improve the power factor of the power system (1); A DC / DC converter (4) is connected to the output of a PFC stage (3) and is arranged to receive a DC voltage from the PFC stage (3) and convert the received DC voltage into a DC output for driving the load (5). The PFC stage (3) includes an inductor (11), which comprises: Magnetic core (13, 14); A winding (12) is wound around the magnetic core (13, 14) such that the magnetic flux induced by the current flowing through the winding (12) circulates through the magnetic core (13, 14). The magnetic cores (13, 14) include: A first magnetic core portion (13) has a first magnetic permeability and outer ends facing each other, wherein at least one of the outer ends of the first magnetic core portion (13) is connected to a second magnetic core portion (14). The second magnetic core portion (14) has a second magnetic permeability that is different from the first magnetic permeability; The magnetic flux circulates through the first core portion (13) and the second core portion (14).

2. The power supply system (1) according to claim 1, wherein both outer ends of the first magnetic core portion (13) are connected to the second magnetic core portion (14).

3. The power supply system (1) according to any one of the preceding claims, wherein the shape of the first magnetic core portion (13) is substantially similar to any of the following shapes: Rectangle, square, hexagon, octagon, pentagon, circle, triangle.

4. The power supply system (1) according to any one of the preceding claims, wherein the first permeability is any value in the range of 1000 to 5000.

5. The power supply system (1) according to any one of claims 1 to 3, wherein the second permeability is any value in the range of 10 to 500.

6. The power supply system (1) according to any one of the preceding claims, wherein the first permeability is at least twice the second permeability.

7. The power supply system (1) according to any one of the preceding claims, wherein the second magnetic core portion (14) includes a ferrite layer mounted on at least one of the two outer ends of the first magnetic core portion (13).

8. The power system (1) according to any one of the preceding claims, wherein the second magnetic core portion (14) comprises a hardened gel comprising magnetic core material particles.

9. The power supply system (1) according to any one of the preceding claims, wherein the PFC stage (3) comprises only the inductor (11).

10. The power supply system (1) according to any one of the preceding claims, wherein the power supply system (1) is arranged for driving a load based on a light-emitting diode, LED.

11. A lighting device based on a light-emitting diode (LED), comprising a power supply system (1) according to any one of the preceding claims.

12. The LED-based lighting device according to claim 11, wherein the LED-based lighting device comprises: A dimming unit is arranged to dim the LED load.

13. The LED-based lighting device according to any one of claims 11 to 12, wherein the DC / DC converter (4) is any one of the following: Boost converter, buck converter, buck-boost converter, flyback converter.

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