NL1037553C2

NL1037553C2 - Power factor corrector device for a dimming circuit.

Info

Publication number: NL1037553C2
Application number: NL1037553A
Authority: NL
Inventors: Riccardo Arthur Wet; Franciscus Adrianus Steur
Original assignee: Online Services B V
Priority date: 2009-12-14
Filing date: 2009-12-14
Publication date: 2011-06-15

Description

TITLE: Power factor corrector device for a dimming circuit.

FIELD OF THE INVENTION

5 The invention relates to a power factor corrector device for a dimming circuit. BACKGROUND OF THE INVENTION

With the progress in lighting technology (and under continuous global pressure to develop more energy-efficient transducers) other kind of lamps 10 has become popular, namely fluorescent lamps (F-L) and, lately, the high-power light-emitting diodes (LED-L) lamps. Both these lamps are no longer, such as the incandescent lamp, made of a simple, single resistive element but consist of several components of very different and disparate electrical properties themselves. Therefore, the total load that they present to the AC 15 sinusoidal supply is very different from the simplex behaviour of a pure resistor. This calls for novel designs of ballast devices for dimming circuits.

In addition, the present and growing demand for compact H-B LED lamp’s constant current devices-controllers has motivated several well known 20 electronic manufacturing firms to design, produce, and make commercially available Integrated Circuits (ICs) exclusively for this specific purpose.

As these ICs are custom-made and differ from each other in the topology of their respective working principles and power handling, the application 25 designer has a very restricted choice when intending to design an in-house, brand-new, competitive and well-spread range of modern solid-state luminaries for household, commerce and industry.

The so called ballast has evolved from the already mentioned electro-30 magnetic to the sophisticated electronic types of today. Specifically, for the 1037553 2 operational low-voltage halogen-incandescent luminaries they have even adopted the general commercial term of electronic transformers, with its implied meaning of simple voltage-down-converters (nominally 230 Volts AC household mains potential being in this case a relative high-voltage source.).

5

Thanks mainly to the amalgamation of the active components into integrated-circuits (ICs) and SMD (Surface-Mounted Devices) passive components generally available today, this LEDS lamps controllers have become very compact and attractive for being implemented within the tight 10 enclosures of household-type incandescent and Compact Fluorescent Lamps (CFLs) of similar geometry and volume; so its increasing desirability.

These electronic device-drivers are in fact no more than very efficient SMPS (Switching-Mode Power-Supplies) in miniature. They are implemented in 15 various general and well documented topologies, and new ones are being constantly developed as the requirements evolve with the availability of newer light transducers of different physical and electric properties and new electronic design techniques and manufacturing integration.

20 SUMMARY OF THE INVENTION:

The present invention aims to offer a price -and performance-competitive power factor corrector device for a dimming circuit that does not rely on source-scarce and relative expensive ICs: as their core, their source-power interface, as well as all their enhanced features. In addition it is aimed 25 to incorporate such a power factor corrector device into a ballast device standard topology from end to end design that can be applied and easily extrapolated to a complete range and type of lamps of diverse power and applications.

In accordance with a first aspect of the invention a power factor 30 corrector device is provided according to the features of claim 1.

3

In accordance with some aspects of the invention, a a power factor corrector circuit is provided comprising at least one capacitor, to be coupled in parallel to a low frequency DC bridge rectifier output; the power factor corrector circuit including a flyback diode coupled in parallel 5 over said at least one capacitor; and a clamping capacitor coupled in parallel to the power factor corrector circuit adapted to clamp a high frequency ripple of a high-frequency switching-mode ballast device. According to another aspect, a high-frequency switching-mode ballast device for a dimming circuit is provided, the ballast device comprising: 10 a bridge rectifier section having an AC input and a DC bridge rectifier output; a high frequency oscillator circuit including a main ballast coil assembly, coupled to the DC bridge rectifier output; and a power factor corrector device comprising a power factor corrector 15 circuit and a clamping capacitor.

In accordance with some other aspects of the invention, a dimmable CFL high-frequency switching-mode ballast device for a dimming circuit is provided, the ballast device comprising: a power factor corrector circuit and a clamping capacitor coupled in 20 parallel with the power factor corrector circuit.

In accordance with some other aspects of the invention, a dimmable energy saving lamp is provided comprising a light-transducer low-pressure gas tube including filaments arranged for starting the tube light transducing process; a high-frequency switching-mode ballast device for driving the gas 25 tube, the ballast device comprising a bridge rectifier section having an AC input and a DC bridge rectifier output; a high frequency oscillator circuit coupled to the bridge rectifier output; and a main ballast coil assembly coupled to the oscillator circuit and arranged in series with the gas tube filaments; and further comprising a power factor corrector device comprising 4 a power factor corrector circuit and a clamping capacitor coupled in parallel with the power factor corrector circuit.

The overall effect of the power factor corrector circuit is to extend as much as possible the -otherwise severely restricted- angle of conducted 5 current drawn from the supply line.

The overall effect of this power factor corrector device is to counter act a source for EMC induced by the power factor corrector circuit before it enters the ballast device.

Furthermore, the power factor corrector device is suited to be 10 implemented in a dimming circuit as well as in a ballast device.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will further be elaborated with reference to the following Figures: 15 Fig 1: Block diagram of the dimmable LED lamp

Fig 2: Detailed circuit diagram of a 3W dimmable LED lamp according to the block diagram of Figure 1.

Fig. 3: Standard circuit diagram of a conventional 11W CFL.

Fig. 4: Integrated Power Factor corrector device.

20 Fig 5: Block diagram of the CFL

Fig 6: Detailed circuit diagram of Figure 5.

Fig. 7: Standard circuit diagram of a conventional 11W CFL.

Fig. 8: Integrated Power Factor corrector device.

Fig. 9 Circuit diagram of the power factor corrector device 25 Fig. 10 Mechanical construction diagram of the power factor corrector device of fig. 9

Fig. 11: Detailed circuit diagram of another CFL Fig. 12 Pair of E-cores with primary and secondary coils In the figures, similar or corresponding elements will be addressed using the 30 same reference numerals.

5

DETAILED DESCRIPTION OF EMBODIMENTS

LED EMBODIMENT

5 Great progress have been made in the last part of the old century by the lighting industry in order to meet the new trend, especially in the field of fluorescent lamps: steadily the original the so-called electromagnetic ballast had made way for more efficient electronic types, and even the modern fluorescent tubes themselves have today a much better lumen-per-watt 10 energy-conversion ratio.

The race is on for a lighting source with the least disadvantages and the most efficient input-power lumen-output ratio. The modern LED lamps seem to fulfil that requirement. Their main properties, vis a vis older technologies 15 are: - mechanical compactness and robustness, light and packing-friendly, - lower operating voltage, less inherent operational stress, - no brittle glass or vacuum enclosure required for normal operation, 20 - no direct heated metal transducer used, - no mercury, amalgam or foreign catalyst required for energy conversion, - inherent solid-state reliability and longer estimated working life, - best lumen-watt ratio than incandescent and fluorescent lamps, - no toxic residual chemicals precautions needed when replaced, disposed, 25 - availability in different primary colours and power ratings, - steadily getting better as price-performance specifications evolve, - solid-state’s lower manufacturing risks, - growing general consumer’s budget-conscious acceptability, - progressive tightening of official efficient legislation worldwide.

30 6

Although they seem to be a good bet for the future (as far as lighting-delivery transducers technology and range of applications is concerned), the developing engineer has to be aware of certain inherent limitations and restrictions for implementing successful commercial LAMPS, such as: 5 - normal low DC operational voltages coupled with relative high currents, - point of source light transducer might need added distribution optics, - concentrated energy will need some sort of thermal management, - versatility, longer life and efficiency must not compromise real and 10 perceived manufacturing, distribution and retail final cost barriers in order to make the technology, appeal-able and viable.

Therefore the challenge is to translate the obvious potential advantages of the LEDS LAMPS into a real-world competitive and popular price-15 performance product.

As the cost of the original High-Brightness (H-B) LED devices have come down in price dramatically in the last couple of years, the focus have been put squarely in the design and implementation of suitable low-cost drivers to 20 match them, coupled with the desired goal of making a modern, more efficient and longer-lasting direct-replacement product for the ubiquitous household incandescent bulb.

The Power factor (PF), is defined as the cosine of the phase-angle between the 25 load’s voltage and current waves, which is a unit-less number between 1 and 0. When the PF=1, the voltage and current waves are in perfect sync, and all the energy that is supplied is consumed by the load (the PF of a purely resistive load is equal to 1). When the PF<1, the voltages and current waves are out-of-step, and only part of the energy supplied is consumed by the load, 7 the rest being cyclically absorbed then reflected back, at the frequency of the AC supply (in standard reticulation distribution, meaning 50 or 60 Hz).

Whereas incandescent lamps are purely-resistive loads, Fluorescent Lamps 5 and high-power LEDs lamps include some substantial capacitive reactance themselves. Accordingly, their Power Factor is poor due to the resulting V/I phase-shift, and the part of the total power supply available to do real work is therefore somehow compromised by the presence of a concurrent reactive power term. Phase-cut dimmers are generally not suitable for dimming these 10 poor PF lamps.

As this type of dimmer is advanced, it greatly distorts the incoming voltage wave-front progressively, and the higher harmonics elements so generated tend to increase even further the original reactance value-part of the load (at 15 the nominal mains frequency), which leads to an even grater V/I phase-shift, a dramatic reduction of the originally inherent poor PF that this type of lamps have, and finally, an increased loss of the real available power.

This vicious-circle manifest itself as mild to severe flickering of the lamps as 20 the dimmer control is advanced, and is most-evident when attempting to dim them below 50% (of their nominal maximum power output). The reactive part of the load, capacitive and/or inductive (Xc and/or XI), induces a phase-shift between the supplied voltage wave-front and its consequential resultant load-current. The relative amount of phase-shift that thus occurs is a magnitude 25 so called power-factor of that specific load.

Therefore, a purely inductive or purely capacitive load results in a relative phase-shift of minus/plus 90 degrees and a PF=0. Purely inductive or pure capacitive loads consume no power on average, but merely cyclically absorb 30 and reflect the input power totally. Importantly then, the closer the PF is to 8 0, the less real power is available in the load transducer circuit to do work efficiently.

Turning now to Figure 1, the block diagram of the dimming circuit, coupled to 5 AC mains is divided into four areas: 10) Triac-dimmer minimum-load interface.

20) Low-frequency AC to DC rectifier-converter.

30) Passive Power Factor Correction compensator integrated network device. 40) High-frequency DC to AC self-oscillating inverter.

10

Referring specifically to the 10 - 40 sections of Figure 1, the following is observed: (10) Triac-dimmer minimum-load interface.

15

Most commercial dimmers are of the phase-cut topology and have at their core a high-voltage AC bipolar gating-controller device, an industry-standard electronic component known as a TRIAC. These dimmers, being low-cost due to their small component count, have historically been -and they still are- the 20 most popular brightness controller for incandescent luminaries, therefore their wide use in the average household, worldwide.

Though their electronic design principle is fairly standard, their actual manufacture implementation still differs quite a lot from brand to brand.

25 Moreover, depending of the particular TRIAC device used, all have a specific -and perhaps diverse- maximum power-handling capability.

More important, in the present context of sourcing variable power to the relative much lower power LED lamps, is the -also generally stated in the 30 product’s packaging- specific minimum load requirement. This is mainly due 9 to an inherent restricting electrical property of all TRIACS devices and it is very well published and understood.

In the present invention design, a fixed resistor of relative medium K-ohms 5 value helps to equalize the performance of many disparate dimmer devices, especially at low brightness levels, as it presents a constant and fixed minimum working load to the wide-spread brands and types of lightcontrolling TRIAC-core products commercially available in the marketplace: their average response become smoother, less prone to flickering, less noisy, a 10 more reliable operational life-span can be expected, and their general performance becomes more predictable.

Its contribution is therefore four-fold: - To present a constant pure-resistive component to offset, at least partially, 15 the reactively inherent characteristic of any CFL’s input impedance.

- To help equalize the performance of the very disparate dimmer electronic designs dimming ranges, and the mechanical variations in their control-pot geometry span-travels.

- To present the dimmer’s gating device (the Triac core) with a minimum load 20 current to keep it conducting for a longer angle span, especially at the critical low-brightness dimming settings, when the avoidance of flickering is highly desirable, not only just for aesthetics but also due to sound electronic design principles.

- As a perfect resistive element of fixed value, always in parallel with the 25 changing lamp’s reactance (as it is progressively dimmed.) it helps to keep the overall PF as high as possible, and therefore contributes -although partially, as compared to the principal contribution of the power factor corrector device described above- to keep the overall harmonic distortion incheck, as well.

30 10 (20) Low-frequency AC to DC rectifier-converter.

This is implemented as a high-voltage full diode-bridge rectifier topology 200 of standard-grade inverse-recovery response. Its many possible current-5 capacity rating values are directly proportional to the specific stated AC overall power consumption.

(30) POWER-FACTOR CORRECTOR.

A Power-Factor Corrector (PFC) is an electronic sub-circuit 400 needed to 10 help reduce as much as possible the phase-shift between the input Voltage and Current wave fronts due to the presence of a complex/non-linear load.

A non-linear load (linear-load= perfect resistor) will generate some sort of spurious, non-desired harmonic (higher multiples.) frequencies that, as they 15 all add-up, will distort somehow, the generally clean sinusoidal fundamental low-frequency Mains supply wave-front (50/60 Hz). The greater the nonlinearity factor, the worse the harmonic distortion will be.

Very strict International Standard are being currently enforced world-wide in 20 respect of the electronic pollution limits that apply specifically to any kind of load/appliance/circuit connected to the L.V. Public Utility Supply distribution lines (110/220VAC) and that includes all luminaries.

There are two main power factor corrector implementation approaches: they 25 are so called passive and active. Respectively, each presents the design and the manufacturing engineers with their own set of electronic and mechanical advantages and restrictions, notably challenging in the case of the CFLs.

But the general idea, or rather common goal, is to make, somehow, the load as to look as much resistive as possible, taking in consideration the best 11 price/performance, mechanical space/electronic complexity, and total design effort/features compromises.

According to an aspect of the present invention, a passive power factor 5 corrector has been chosen for its simplicity, robustness, low-cost and, - as the provided comparative tests will confirm - it’s very promising results.

The power factor corrector according to an aspect of the invention is practically realized by the integration within a single component sub-10 assembly (resembling an ordinary polarized 2-terminal electrolytic capacitor) of an electrical network of 2 capacitors and 3 rectifier diodes, placed just after the bridge rectifier 200, superseding the single reservoir capacitor characteristic of standard Low-PF lamps and at the same classical position. The overall effect of this network is to extend as much as possible the -15 otherwise severely restricted - angle of conducted Current drawn from the

Supply line within the reference of the positive and the negative excursions of the input Voltage mains cycle/period.

Accordingly the power factor corrector circuit 400 comprises a two-terminal 20 network of three serially switched diodes; wherein first and second diodes are coupled in parallel with a first polarized capacitor and wherein second and third diodes are coupled in parallel with a second polarized capacitor; the two-terminal network coupled in parallel to the bridge converter. The flyback diodes D4, D5, D6 or steering diodes make the capacitors’ distributed overall 25 charging and discharging process (from the supply and to the load respectively) smoother, predictable, balanced, self-adjusting and more independent of the load’s demands. The overall input Current waveform tends to better follow the input Voltage waveform, and as is greatly improved average shape shows, brings into view a clear indication that the non-30 linearity conductive restrictions of the load have been largely overcome.

12

According to an aspect, the present invention accordingly provides a front-end, highly efficient passive high power factor correction.

When integrating the electronic components of the capacitive circuit in a 5 single electronic device, an example of which is illustrated in Fig 4, the result of the tight mechanical integration of 5 standard electronic components within this new 2-terminal Power-Factor Correction Device saves footprint space and interconnection tracks and holes on the PCB.

10 Accordingly, the power factor corrector circuit 400 is preferably designed as a two pin connectable device. The input impedance of the CFL now becomes less reactive, therefore with a marked and more defined resistive behaviour that was originally predicted if no power factor corrector were to be implemented. Much less energy bounces-back towards the supply-lines: the 15 nasty harmonics are greatly restricted and the harmonic distortion is brought within acceptable specification’s margins.

40) High-frequency DC to AC self-oscillating inverter.

20 The challenge presented by the need of a general-purpose and very compact power converter is magnified by the desire for a cost-effective but reliable SMPS universal design topology that could be applied successfully to a full range of mains-powered luminaries.

25 Although new specific ICs available for this very purpose have started to appear in the marketplace, variations of tried and tested discrete components topologies can work as well as the emerging new-ones, and can be as good for its perceived price-performance competitiveness.

13

One of the most popular and reliable have been the so called DC-bus powered, High-Frequency, Half-Bridge AC Driver configuration, that is one of the group of ideals in order to excite non-linear/complex loads.

Again, modern manufacturing techniques have gravitated to amalgamate 5 and miniaturize the main critical components of general-purpose Half-Bridge Drivers into Integrated Circuits, custom-made by well known power-control oriented design houses, and also manufactured under their licences by several third-party electronics concerns.

10 As the output load impedance of the converter remains relatively fairly constant, and its input power DC-BUS voltage varies with the progressive dimmer operation, a variable current control is developed onto the LED devices themselves, therefore proportionally varying their brightness.

15 A simple design calculation to properly rate all the current-carrying components of the basic topology design core, in order to encompass all the products within a set range of industry-standard power outputs, then becomes a very simple scale and straight-forward proportionality task.

20 According to an aspect, no specialized high voltage IC-driver is used but a discrete high voltage switched mode power supply.

Figure 2 refers to a detailed block diagram showing practical implementation of the device. Accordingly, there is shown a high-frequency switching-mode 25 ballast device 100 for a dimming circuit, the ballast device 100 comprising a bridge rectifier section 200 having an AC input 201; 202 and a DC bridge rectifier output 203; 204; a high frequency oscillator circuit 300 including a main ballast coil assembly 350, coupled to the DC bridge rectifier output 203; 204; and further comprising a power factor corrector circuit 400 comprising at 30 least one capacitor C6, C7, coupled in parallel to the DC bridge rectifier 14 output 203; 204; the power factor corrector circuit 400 including a flyback diode D4, D5, D6 coupled in parallel over said at least one capacitor C6, C7.

Figure 3 shows a detailed layout scheme for the power factor corrector 5 functional circuit which may be applied in other electrical layouts for improving a power factor.

Figure 4 shows an embodiment, wherein the dimming circuit is arranged for driving a (High Brightness) LED 60.

10

Basically, a LED (Light-Emitting Diode) is a current-driven energy-transducer device and can be driven electrically only by a direct (unipolar or single polarity -generally labelled as DC-) energy-source. Its maximum normalized current has a tight specification and can not otherwise be 15 exceeded without a predictable sure failure: in electronic terms it has a very low dynamic impedance. Therefore the control of its current is the most important requirement for the associated electronic driver.

Its normal operating voltage is relative very low (only a few volts) and once is 20 progressively achieved (i.e.: as a slow rise from 0 Volts can testify) it will remain relative constant. Thereafter it will revert to its constant-current drive requirement, so long as it is operated within the range of its maximum specified current limit.

25 H-B LED devices are basically designed for constant current operation to attaint their maximum specified efficiency, therefore there is a general perception that they can not be directly dimmable by voltage drivers means.

According to an aspect of the present invention, as opposed to industry 30 standard current driven control topologies, the present invention provides a 15 voltage driven and dimming control design for a LED device. Accordingly, the LED-device according to the invention comprises a ballast device providing a voltage driven dimming control design.

5 For a discussion of block elements 10-40, reference is made to Figure 1. In addition, for driving the HB-LED 60, block element 50 references a high-frequency AC to DC rectifier and ripple-compensation network.

Since the LEDS devices are essentially unipolar in their normal operational drive requirements, a high frequency and efficient AC to DC conversion is 10 implemented in the present invention. The use of an inverse fast-recovery full-wave rectifier diode-bridge configuration aids to this purpose in a simple, compact and robust way, which rating can as well be scaled to each particular LED lamp nominal power output.

15 According to an aspect, the driver is of a fixed frequency, and no frequency control is required.

In order to extend to it’s maximum the dimming performance capabilities of the LED lamps, an optional and proportionally rated relative low voltage 20 electrolytic capacitor could be added in parallel with the output DC polarized terminals of the high-frequency rectifier diode-bridge to aid to minimize any onset of flickering behaviour that could appear on the LED devices at very low brightness levels, if so required. It could, as well, help to the general smoother transitional operation of the dimmer controller itself, as it is 25 exercised throughout its full range.

In another embodiment in addition to the shown power factor corrector circuit (400) a clamping capacitor may be coupled in parallel to the power factor corrector circuit (400). In this manner a power factor corrector device 30 (500) is provided which will be described further below, fig. 9.

16

CFL EMBODIMENT

Before further elaboration on the drawings 5-8, the following is considered regarding the switching behaviour of ballast devices for CFL. The problem is 5 not the household dimmer or the CFLs themselves. The reason for this poor performance resides mainly in the electronic-properties (characteristic IMPEDANCE) miss-match between them.

This dynamic inter-action between the source energy device and its 10 corresponding load counterpart is seldom perfectly efficient, and there is always certain loss when attempting their practical inter-coupling.

When an AC load is not a perfect resistor (as generally is the case in the incandescent-type lamps) the electrical source-energy is not converted into 15 light-energy in its entirety: curiously, some part of the incoming-energy is absorbed by the load (and converted into light and heat) and some of it is rejected, or more appropriate, bounced-back towards the source. The load circuit reacts against its source, so to speak due to its reactance.

20 An AC complex-impedance-load is therefore one that has some resistance AND some reactance values. The reactive components of the load are the cause of losses and wasted applied energy, therefore the aim of any good engineering electronics AC design is to keep the resistive/reactive-ratio of the load as high as possible in order to obtain the maximum desirable -but 25 practical- (reads: cost-effective-way) energy-transfer (efficiency) effect. Oneway to express this important ratio is called: the Power-Factor of the load. Other way (mainly concerning known complex loads) might be: the relative index of the load’s capability to do real work.

17

Power-Factor (PF) can be described as the resultant amount of phase-shift angle between Voltage and Current that can be induced by any load (with some reactive component/s in them) when an AC electrical source-energy is applied to it. The magnitude of the PF is defined as the value of the cosine of 5 said angle, therefore, a unit-less number between 1 and 0.

When the AC load is a pure resistor, practically all the energy is transfer to the load, (as -by definition- there are no reactive components in them), and therefore no phase-shift can occur: the PF is, theoretically, = 1.0.

10 Voltage and Current are said to be always in-phase: the work efficiency of the circuit is maximum.

When an AC load is a pure reactance (i.e.: a perfect Capacitor and/or perfect Inductor), the load not only bounces-back all the incoming energy: but the 15 resultant phase shift is theoretically +/- 90 degrees now, and therefore the PF = 0.0. Transfer efficiency is at minimum, as only heat losses are generated.

In-between these two extreme examples, the real-world of generally useful 20 electronics application resides. One of the most ubiquitous is the modern, so-called, energy-saving CFL.

A CFL is composed of a few dozen different electronic components, but basically, can be thought-of a miniature high-frequency switching-mode 25 power supply (HFSMPS) driving a light-transducer low-pressure gas tube 60. The overall input impedance of the CFLs are far removed from the theoretical pure-resistive concept, (vis a vis: the incandescent paradigm.) as their Power Supply (PS) front-end are made (purposely.) highly capacitive due to the need for reservoir or smoothing DC capacitor/s of very significant value, as any 18 good AC/DC/AC frequency converter design must have for its intended stable and reliable long-term operation.

This relative significant capacitive character of the input impedance of the 5 classical front-end of the PS of any standard fluorescent lamps tends not only to lower their PF, but as of direct consequence (due to their added full bridge rectifier-diodes standard configuration and conductive behaviour), distorts the incoming the Current supply waveform itself, proportionally increasing the it’s Total Harmonics Distortion (THD).

10

Turning now to Figure 1, the block diagram is divided into two areas: (A) Integrated front-end area including aspects according to the invention; (B) Conventional circuit elements of CFL circuitry including a rectifier; 15

Just for completion and without limitation we refer to the details of Figure 2 to provide an embodiment of the conventional circuitry of the B-area; variations and modifications to this standard circuitry are known and deemed to be included in the specification.

20

Referring specifically to the A1 - A4 sections of Figure 1, the following is observed: (1) POWER-FACTOR CORRECTOR.

A Power-Factor Corrector (PFC) is an electronic sub-circuit needed to help 25 reduce as much as possible the phase-shift between the input Voltage and Current wave fronts due to the presence of a complex/non-linear load.

A non-linear load (linear-load= perfect resistor) will generate some sort of spurious, non-desired harmonic (higher multiples.) frequencies that, as they 30 all add-up, will distort somehow, the generally clean sinusoidal fundamental 19 low-frequency Mains supply wave-front (50/60 Hz). The greater the nonlinearity factor, the worse the harmonic distortion will be.

Very strict International Standard are being currently enforced world-wide in 5 respect of the electronic pollution limits that apply specifically to any kind of load/appliance/circuit connected to the L.V. Public Utility Supply distribution lines (110/220VAC) and that includes all luminaries, therefore CFLs, fall within the scope of this sector.

10 There are two main power factor corrector implementation approaches: they are so called passive and active. Respectively, each presents the design and the manufacturing engineers with their own set of electronic and mechanical advantages and restrictions, notably challenging in the case of the CFLs.

But the general idea, or rather common goal, is to make, somehow, the load 15 as to look as much resistive as possible, taking in consideration the best price/performance, mechanical space/electronic complexity, and total design effort/features compromises.

In the context of the present document, a passive power factor corrector has 20 been chosen for its simplicity, robustness, low-cost and, -as the provided comparative tests will confirm-, it’s very promising results.

The power factor corrector according to an aspect of the invention is practically realized by the integration within a single component sub-25 assembly (resembling an ordinary polarized 2-terminal electrolytic capacitor) of an electrical network of 2 capacitors and 3 rectifier diodes, placed just after the bridge rectifier B2, superseding the single reservoir capacitor characteristic of standard Low-PF lamps and at the same classical position. The overall effect of this network is to extend as much as possible the — 30 otherwise severely restricted- angle of conducted Current drawn from the 20

Accordingly the power factor corrector circuit A1 comprises a two-terminal 5 network of three serially switched diodes; wherein first and second diodes are coupled in parallel with a first polarized capacitor and wherein second and third diodes are coupled in parallel with a second polarized capacitor; the two-terminal network coupled in parallel to the bridge converter. The flyback diode (D4, D5, D6)s or steering diodes make the capacitors’ distributed 10 overall charging and discharging process (from the supply and to the load respectively) smoother, predictable, balanced, self-adjusting and more independent of the load’s demands. The overall input Current waveform tends to better follow the input Voltage waveform, and as is greatly improved average shape shows, brings into view a clear indication that the non-15 linearity conductive restrictions of the load have been largely overcome.

When integrating the electronic components of the capacitive circuit in a single electronic device, an example of which is illustrated in Fig 8, the result of the tight mechanical integration of 5 standard electronic components 20 within this new 2-terminal Power-Factor Correction Device saves footprint space and interconnection tracks and holes on the PCB.

Accordingly, the power factor corrector circuit A1 is preferably designed as a two pin connectable device. The input impedance of the CFL now becomes 25 less reactive, therefore with a marked and more defined resistive behaviour that was originally predicted if no power factor corrector were to be implemented. Much less energy bounces-back towards the supply-lines: the nasty harmonics are greatly restricted and the harmonic distortion is brought within acceptable specification’s margins.

30 21 (2) Electro-Magnetic Compatibility counter-measures.

The A2 block of Figure 1 is a schematic illustration of a low pass filter including an inductor A2 coupled in parallel to the power factor corrector circuit A1 to provide a low pass filter. More particularly, an L-R High 5 Frequency Low-Pass Filter (HF-LPF) A2 is configured in series with the total circuit’s load’s current-return-path 30.

Harmonic distortion can be measured with specialized relative low-frequency response analyzers (up to the 40th. Harmonic of the fundamental Mains frequency, -50 or 60 Hz.-, that means roughly up to 25KHz or so.). The 10 current pass-specification usually keep a special watch for the third and the fifth ones, still within the realm of very low frequencies, indeed.

If the power source is a theoretical constant sinusoidal one, and the load is relative stable, the upper terms of the harmonic distortion will be relative 15 greatly reduced. Therefore, with just a properly rated and good performance power factor corrector device added to any CFLs’ front-end, their overall electronic designs will be expected to be within specs.

But that is only part of the whole EMC (Electro-Magnetic Compatibility) 20 assessment that all electrical and electronic products must comply with.

Any HFSMPS (high-frequency, switching-mode power supply) is a source of interfering harmonics also, and every CFL must have one due to its inherent AC/DC/AC switching frequency-con version topology.

25 As the fundamental of the built-in converter of any CFL is already at around 40KHz and above, we can expect very high frequencies to be present in the total electrical circuit as well, as the load that the converter (more precisely, inverter at this stage) sees, is a highly non-linear one (as it includes the highly complex electronic dynamic behaviour of the tube itself.). Without 30 being restricted to a specific lower limit, high frequency will be meant to 22 indicate at least in the KHz range, more specifically at least 20 KHz and higher to MHz frequencies relevant for EMC specifications; where low frequency will be meant to indicate lower than this lower limit, especially, in the range of 50/60 Hz and lower harmonic multiples, relevant for THD 5 specifications.

If we add to this scenario the possibility of varying the input power to the tube by means of varying the power input to the whole lamp (and it’s core non-sinusoidal switching driver.) with a waveform-chopping device (any Phase-Cut dimmer comes into view from here on.) we have in every CFL 10 itself a potential interference-generator of very important magnitude indeed.

As this EMC-passing regulation extends a mandatory test up to 30MHz, means must be provided to minimize the HF fundamental and its harmonics so generated by the SMPS driving the fluorescent tube circuit.

15

To this effect, an L-R High Frequency Low-Pass Filter (HF-LPF) is configured in series with the total circuit’s load’s current-return-path towards the Mains power source. The inductive element (L) is located in series with the total DC current return circuit, and the resistance element (R), that does 20 double-duty as a safety current-limiter in case of a short-circuit inside the whole CFL assembly, is complementary located in series with the total AC input current path into the lamp.

The inductor is implemented as a HF-choke made of a copper-wire coil 25 wounded around a ferrite core, and the resistor is a low-value, high-power one. All and each element’s current-carrying capacity of the L-R filter must be dimensioned according to the rated output (20-1; 20-2) maximum brightness required for each CFL, taking in consideration, as well, the extra dissipation required to deal effectively with the onset of spurious higher 30 power-terms of significant value, specially when dimming.

23 A full disclosure of the typical values of the components of this HF-LPF is given (as a general practical, feature-enhanced, actual lab implementation example, that has been built based on an standard 11W CFL, and used here 5 with the only purpose as to provide real, complementary and fair comparative test results to the solid validity of this mainly theoretical document) in with reference to Figure 6, below.

In another preferred embodiment, a DC electrolytic capacitor is added in 10 parallel with the high power factor switching arrangement, figure 11.

The low frequency ripple generated by the high power factor switching topology, is introduced to the DC supply rail and hence forth amplified by the two switching transistors at high frequency generating harmonic and electromagnetic interference. This subsequent low frequency interference 15 would on its own not pose substantial difficulty, but is amplified by the high frequency switching transistors and can create EMC incompatibility on to the mains Voltage return line. This effect also manifest itself as heat, generated in inductor LI it acts as a choke and have to deal with the subsequent harmonic distortion now apparent in the circuit, making this design less 20 desirable and more energy hungry. To counter the effects of this an electrolytic capacitor is added as a clamp to minimise the effect of the ripple being generated by the high power factor topology. This added capacitor would seem counterproductive as it nullifies the effect of the high power factor correction circuit and it's intended function. This configuration is by no 25 means conventional as it is counterproductive, by making the HPF switch topology less efficient and increasing the THD generated by the device. This electrolytic capacitor thus needs to be calibrated as to find a balance between the EMC, THD and overall performance of the device. It is envisioned that this capacitor should be of very low value in the order of between 200nF and 30 900nF and appropriate Voltage for its intended application market. A typical 24 example before the adding of this electrolytic capacitor a typical value for the power factor in a CFL of power value between 5W and 25W would be between 0,9 and 0,96, after adding the capacitive device correctly calibrated, a typical value would be in the order of 0,85 to 0,9, still qualifying under international 5 standards as a HPF device. For a CFL of 7W, for example, 0,27pF, 9W = 0,3pF, llW=0,3pF, 15W=0,47pF, 20W=0,6pF, 25W=0,47pF.

(3) MAINS-PORTS DIMMER/LAMP INTERFACE.

Conventional so called Phase-Cut dimmers have at its AC controlled-current 10 core a bi-polar gating electronic component popularly known as a Triac.

Accordingly, in an embodiment, the dimming circuit B 3 is of a phase-cut off type typically including a triac. As these types of dimmers have been (and still are) the de-facto standard for the entry-level household sector, and as good as their advantages are, such as: low-price, ruggedness and 15 compactness, unfortunately those face-value advantages are offset by they poor control of the brightness of any standard, off the shelf (and so rightly labelled.) non-dimmable CFLs.

When a typical consumer takes them home and attempts to connect them to 20 an existent dimming circuit B3 for the first time, erratic, noisy and severe flickering behaviour soon follows, just only after a few minutes into the trial.

Persistent manipulation of the dimmer or re-starting the lamps at low levels, usually leads to the permanent failure of the CFLs, (sometimes of both 25 devices) fairly soon into the continuous repeat of this helpless attempts.

Just a simple resistor (or resistor network) of proper value and rating, place at the input mains’ port of the CFLs can make the performance of any phase-cut dimmer more predictable and repeatable. A practical value and rating is 30 given in Figure 6. Accordingly, preferably, a resistive network A3 is provided 25 coupled in parallel to the DC bridge rectifier input (10-1; 10-2) to interface with a dimming circuit B3.

Its contribution is therefore four-fold: 5 - To present a constant pure-resistive component to offset, at least partially, the reactively inherent characteristic of any CFL’s input impedance.

10 - To present the dimmer’s gating device (the Triac core) with a minimum load current to keep it conducting for a longer angle span, especially at the critical low-brightness dimming settings, when the avoidance of flickering is highly desirable, not only just for aesthetics but also due to sound electronic design principles.

15 - As a perfect resistive element of fixed value, always in parallel with the changing lamp’s reactance (as it is progressively dimmed.) it helps to keep the overall PF as high as possible, and therefore contributes -although partially, as compared to the principal contribution of the power factor corrector device described above- to keep the overall harmonic distortion in-20 check, as well.

(4) TUBES’S FILAMENTS HEATING.

As already mention above, the integrity of the filaments 70 at each end of the florescent tube is a clear indication of the relative life-condition of any CFL. 25

The filaments 70 are necessary to help start the ionization process of the compound heavy-metal and complex gas structures inside tube’s rarefied low-pressure vacuum that finally starts to break its initial high impedance state (due to the initial presence of a high-voltage differential potential) in order 30 for an arc to develop across it length and thus starts the lamp (strike phase).

26

The high current burst that immediately follows -as the impedance of the lamp instantly decreases dramatically- excite the mercury gas inside with enough energy as its free electrons are able to release visible light-bearing 5 photons as they collide with the atoms of the phosphor coating inside.

Finally, after a few of seconds, when the lamp has reached it’s optimal balanced temperature, automatically acquires its natural steady-state phase, developing its specifically-designed public parameters, such as its normal running current, nominal power rating and stated luminance output (20-1; 10 20-2).

This situation is normally referred to as a CFL’s cold start-up.

The hard-metal filament’s core-base are themselves coated with a chemical 15 substance that favours the emissions of primary-source electrons as to greatly facilitate the reliable but complex series of processes that finally bring the lamp to it’s strike phase. Therefore their integrity, or otherwise the lack of it, is the weakest-link in the tube, and they constitute mainly the initial load when the driving electronics are started as the mains power is initially 20 applied to the lamp: the filaments 70 take an initial substantial stress each time the lamp is powered-up.

Eventually, with time and the repeated power-ups, the special chemical coating on the filaments 70 begin to literally peel-off due to the normal wear 25 and tear of the inter-collision of atoms and electrons due primarily to the relative big surge start-up and (although at a much lesser rate.) the normal arc AC currents (back and forth) from end to end of the tube.

This has the effect of start pitting the sensitive coating, exposing the bare 30 hard-metal and, at this stage, the deterioration of the filaments 70 continue 27 to occur at an accelerated rate, until eventually one (or both) breaks up and an open filament situation develops.

From now on it will be almost impossible to start the CFL. A so-called tube’s 5 black-end will be symptomatic of this progressively undesirable development.

As to add further value to the features already described in this document, herewith is proposed to add a constant filament heating feature that will not only facilitate the initial emission of source electrons, but will soft-start the 10 CFLs with much less electronic overall stress, will help to keep the integrity of their filaments 70 (as their coatings will be less prone to the rate of pitting otherwise occurring with the cold-start situation) and therefore, as a great bonus to the consumer, extend substantially their normal useful life expectancy, more particularly when dimming is applied.

15

The implementation is again, simple, rugged and reliable enough to always guarantee a soft-start from initial power-up and an automatic filaments 70 protection when attempting to re-start an already extinguished lamp at low brightness dimming levels.

20

The inductance of the choke and the start capacitance values defines the resonant frequency-circuit that builds-up the required high voltage necessary to generate the necessary initial burst of arc-current that will start the lamp.

25 Until the resonance point is not achieved, the lamp will not have a enough high-voltage to start-up; therefore, if for some brief time, and at the same time some current is allowed to pass trough both filaments 70 their naturally low cold resistance will steadily increase, automatically pre-heating them and will start to generate source electrons just prior of the initiation of the 30 ignition phase.

28

To realize that important condition during this initial phase, heating supply current for both filaments 70 is obtained from a transformer configuration built-in within the main ballast coil assembly: two independent small-turn 5 coils are added electrically independent and in parallel with each filament.

After the lamps strikes, and from now-on until the overall mains power supply to the lamp is interrupted, the filaments 70 will always be provided with their heating current, even in the case the lamp has apparently 10 extinguished, (due to over-extension of its useful dimming range, or maybe due to a sudden or progressive drop in ambient temperature.) as their internal oscillator still will be operational. This can substantially improve a dimmed CFL’s lifetime 15 Therefore, a residual AC current will still pass though the filaments 70 (as the driver electronics are still powered, although with lower incoming mains current.) as to keep them still in a relative warm situation. A small increase in the input supply mains current (usually just by tweaking upwards the dimmer’s control pot.) will then normally be enough to soft-start and re-ignite 20 the lamp, safely and with no electronic stuttering (no apparent flickering) whatsoever, thus avoiding a filaments 70-wearing, continuous cold restarting, vicious-circle condition of popular previous designs.

Typical secondary’s coil parameters are given with reference to Figure 6 in 25 the section just below (only for the 11W CFL reference design, and presented here only as a specific practical implementation example).

Accordingly, it is shown that the dimmable energy saving lamp preferably comprising a gas tube 60 filament heating circuit. The heating circuit may be provided by small-turn coils that are added electrically independent and in 29 parallel with each filament; arranged in transformer configuration built-in within the main ballast coil assembly.

Fig. 6 refers to a detailed block diagram showing practical implementation of 5 the device.

Fig. 7 shows, for reference purposes, a conventional layout of a high-frequency, switching-mode power supply arrangement without the power factor corrector functional circuit.

Fig. 8 shows a detailed layout scheme for the power factor corrector 10 functional circuit which may be applied in other electrical layouts for improving a power factor.

Topology, component values and (when required) their ratings are disclosed. The easy integration possibility of the enhanced circuit into a conventional 15 standard CFL topology, is plain evident. The new circuitry have been numbered according to their detailed described sections, (in the text above) and identified within dashed lines.

While the invention has been illustrated and described in detail in the 20 drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments.

Although a specific type and specific power (prototype-quality) CFL have been constructed to assess the real-world application of the principles 25 disclosed in this document, the integration of all and/or some of the enhancements in order to improve the performance and features over any standard design (as has been the aim of this paper), can be extended and applied successfully across a wide board of all the CFLs, and higher-power Electronic Ballast that are at the core of all modern and efficient luminaries, 30 (including the H.V. LED ones), of any topology and/or any power whatsoever; 30 the only concern being the assessment of the final values and ratings of the components involved. In conclusion Standard, off-the-shelf CFLs are not designed to be compatible with the standard household Triac-type/Phase-cut dimmer devices. The incorporation of a novel front-end sub-assembly 5 substantially optimizes their inherent low Power-Factor, and reduces overall components count. Means for a filament’s constant heating feature has been included within the preferred embodiment, as to greatly extend their normal expected life span.

10 POWER FACTOR CORRECTOR DEVICE

As described above a power factor corrector circuit (PFC-circuit) can be applied in dimming circuits for driving LEDs as well as CFLs or in combination. To counter act the EMC induced by such a PFC-circuit a clamping capacitor is coupled in parallel therewith as shown in fig. 9. Such 15 PFC-device is implemented in another CFL embodiment as shown in figure 11.

This modification diminishes the power factor slightly, but improves the EMC performance as the source thereof is removed before it can be amplified by 20 the circuitry portion of a conventional ballast device. In this manner the parasitic interference over the CLASSIC HPF Cap/diodes standard design is drastically reduced. Furthermore, it improves the running of the lamp as it is quieter, cooler and highly efficient.

25 Below are test results showing the difference in Power Factor performance before and after the clamping capacitor modification as displayed on the digital front panel of a UI3000 Electronic Ballast Tester.

Before mod: 30 (1) Vac Input (rms) = 248.9V.

31 (2) lac Input (rms) = 0.068A.

(3) Power Input = 16.2W.

(4) Power Factor = 0.962.

5 After mod: (small electrol. cap added => 2x 2.2uF/250V in series...) (1) Vac Input (rms) = 248.1V.

(2) lac Input (rms) = 0.081A.

(3) Power Input = 15.9W.

(4) Power Factor = 0.784.

10 2-TERMINAL HPF COMPENSATOR DEVICE:

The PFC-device of fig. 9 is implemented as a 2-pin element. Fig. 10 showing a simple configuration with dielectric 102, 103 and metallic foils 104, 105. allowing a compact housing. In particular, a clamping capacitor C301 is 15 shown formed by a segmented outer foil 104 coupled to the + terminal, opposite an inner foil 105 and divided by a dielectric 103 to provide indicative values between 200 and 900nF. In particular, non limiting values are: for a 7W CFL lamp: a 0.27uF/400V clamping capacitor; for a 9W lamp: a

0.3uF/400V clamping capacitor; for a 11W lamp a 0.3uF/400V capacitor; for a 20 15W lamp; a 0.47uF/400V clamping capacitor; for a 20W lamp, a 0.6uF/400V

clamping capacitor; and for a 25W lamp; a 0.47uF/400V clamping capacitor Outer foil 104 is further segmented and electrically coupled via diode D201 opposite segmented inner foil 105 that is electrically coupled via diode D101 and divided by a dielectric 102 to provide two corresponding capacitors C201 25 and C101 with indicative capacitive values between 5 and 25 uF/250V.

A diode D301 divides dielectric 102 and is coupled in flyback configuration to the diodes D201 and D101 to form a two-terminal network of three serially switched flyback diodes (D101, D201, D301); wherein first and second diodes (D201, D301) are coupled in parallel with a first polarized capacitor (C101) 32 and wherein second and third diodes (D301, D101) are coupled in parallel with a second polarized capacitor (C201).

As opposed to active P(ower) F(actor) C(orrection) devices in the form of 5 customs multi-pins ICs, the implementation of the present compact and highly reliable passive PFC made of inexpensive and ready available components, make this new design attractive and embodied with many practical and technical advantages: - rugged and compact single unit integrated two pin construction in the form 10 of a standard electrolytic capacitor; which provides substantial PCB footprint saving as opposed to multi-pin active PFC IC devices.

- 500V DC H.V. constant withstanding capacity.

- Easy to adapt to different power inputs, directly from the manufacturing factory floor.

15 - Inexpensive, multi-sourced and ready available integral parts.

Integrated Capacitor C301 can help with the passing margin of EMC regulations, greatly improving the performance (and minimizing the pitfalls...) of current passive HPF designs, without adding any other EMC active nor passive components ("counter-measures"...) into any CFL PCB 20 design.

The HPF device module design helps the CFLs run cooler; less spent heat means more efficiency power-transfer conversion ratio and better Lumen/Watt product specification.

The present design allows ready configuration of an electrolytic capacitor 25 production machine and is impervious to Electrostatic Discharge (no sensitive active components in circuit).

Fig. 12 INTEGRATED CFL BALLAST COIL ASSEMBLY L3 AND FILAMENTS HEATER TRANSFORMER: 33

As opposed to non-dimmable CFLs, (whose power input-output ratio is kept constant) the dimmable variety performance is greatly enhanced by the constant heating of their filaments while dimming, as it mainly helps to improve the life-time span of the lamp, and aids in its easy re-strike when the 5 dimmer is brought back-up from its minimum settings.

Most designs employ discrete/stand-alone single (or several) dedicated "ring-core" ferrite coils/transformers in series with the main ballast coil current path. In this design a pair of E-cores is applied allowing compact housing; a 10 first core element 312 including a main coil winding 50, and a second core element 412 coupled to the first core 312 providnig for the secondary windings 401 and 402 in transformer configuration filament. Accordingly the secondary windings 401 and 402 are provided as small-turn coils that are added electrically independent and in parallel with each filament; arranged 15 in transformer configuration built-in within the main ballast coil assembly 312; 50.

The present design has various mechanical/electrical advantages: - Integrated concept saves parts, wiring, assembly time and PCB foot-print.

20 - Compactness means more reliability and ruggedness - no interconnecting loose wires.

- Heating of the filaments start instantly as the internal oscillator is powered up, even before the lamps strikes (assured pre-heating, always, eases the stress son the tube and the electronic components, again helping to the 25 optimum strike repeatability situation, reliability and longevity of the lamp).

- EMC conducted and radiated interference is kept to a minimum as a single point-source which can be dedicatedly shielded.

- Rugged integration means easy handling and efficient mechanical compactness.

30 34

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments.

5

Although a specific type and specific power (prototype-quality) LEDs have been constructed to assess the real-world application of the principles disclosed in this document, the integration of all and/or some of the enhancements in order to improve the performance and features over any 10 standard design (as has been the aim of this paper), can be extended and applied successfully across a wide board of all the LEDs, and higher-power electronic ballast that are at the core of all modern and efficient luminaries, of any topology and/or any power whatsoever; the only concern being the assessment of the final values and ratings of the components involved.

15

Other 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 20 indefinite article "a" or "an" does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. A computer program may be stored/distributed on a suitable 25 medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems. Any reference signs in the claims should not be construed as limiting the scope.

30

Claims

A power factor correction device (500) for a dimming circuit, comprising: a power factor correction circuit (400) comprising at least one capacitance (C1, C2) for a parallel coupling to a DC bridge rectifier output (203; 204); said power factor correction circuit (400) comprising a freewheel diode (D1, D2, D3) coupled in parallel over the at least one capacitance (C1, C2); and a clamping capacitance (C3) coupled in parallel with the power factor correction circuit (400) adapted to clamp a high-frequency ripple of a high-frequency switching mode for switching device.

The power factor correction device according to claim 1, wherein the power factor correction circuit (400) comprises a two-terminal network of three serially-switched freewheel diodes (D1, D2, D3) with first and second diodes (D2, D3) being parallel switched with a first polarized capacitance (C1) and wherein second and third diodes (D3, D1) are coupled in parallel with a second polarized capacitance (C2); 20

The power factor correction device according to claim 2, wherein the power factor correction device is designed as a two-pin linkable device (500).

A high frequency switching mode bias device (100) for a dimming circuit, said bias device (100) comprising: - a bridge rectifier device (200) with an AC input (201; 201) and a DC bridge rectifier output (203; 204); 1037553 a high-frequency oscillator circuit (300) comprising a main ballast coil assembly (350) coupled to a DC bridge rectifier output (203; 204); and further comprising - a power factor correction device according to any of claims 1-5 3.

The ballast device of claim 4, wherein the two-terminal network of the power factor correction device (500) is coupled in parallel with the bridge rectifier section. 10

The ballast device of claim 4, further comprising a resistor network (210) coupled in parallel with the DC bridge rectifier device (201; 202).

The ballast device of claim 4, wherein the dimming circuit is of a phase cut-off type.

The ballast device of claim 7, wherein the dimming circuit comprises a triac. 20

The ballast device of claim 4, further comprising an H-B LED device (60).

A dimmable energy saving lamp comprising: 25. a low pressure light converting gas tube (60) comprising filaments (70) adapted to start the tube light conversion process; a high frequency switching mode ballast (100) according to any of claims 4-9. 1037553 YES

The dimmable energy-saving lamp according to claim 10, further comprising a low-pass filter A2 comprising an inductor (L1) coupled in parallel with the power factor correction circuit (A1) to provide a low-pass filter. 5

The dimmable energy-saving lamp according to claim 10, further comprising a resistor network A3 coupled in parallel with the DC bridge rectifier input (10-1; 10-2) to provide an interface with a dimming circuit B3. 10

The dimmable energy-saving lamp according to claim 10, further comprising a gas tube (60) filament heating circuit (A4).

14. Dimmable energy-saving lamp according to claim 13, wherein the heating circuit (A4) is provided by coils (40) that are added independently of electricity in parallel with the filament; in transformation configuration built in with the main ballast coil assembly (50).

Dimming circuit comprising: - a phase-cut dimmer section for coupling to the AC mains voltage; - a bridge rectifier section (200) with an AC input (201; 202) connected in parallel to the dimmer section; and a DC bridge rectifier output (203; 204); and 25. a power factor correction device according to any of claims 1-3.

The dimming circuit, further comprising a DC-AC converter device coupled in parallel with the power factor corrector device that provides AC output terminals for the dimming circuit. 1037 55 3 -