WO2005022964A1

WO2005022964A1 - Lighting controller

Info

Publication number: WO2005022964A1
Application number: PCT/NZ2004/000204
Authority: WO
Inventors: Michael George Rae Hutcheson; Christopher James Allington; Richard John Newton
Original assignee: Michael George Rae Hutcheson; Christopher James Allington; Richard John Newton
Priority date: 2003-09-01
Filing date: 2004-08-31
Publication date: 2005-03-10

Abstract

A lighting controller (1) for initially reducing and then gradually increasing the power provided to a light source (10) is disclosed. In a first embodiment, the lighting controller comprises a negative temperature coefficient (NTC) resistor having a predetermined initial (room temperature) resistance, a predetermined temperature versus resistance relationship and a predetermined “hot” resistance. In a further embodiment, the lighting controller comprises an NTC resistor (2) having a predetermined temperature versus resistance relationship connected in parallel with a temperature independent resistance (3) and/or a temperature dependent switch (4). The lighting controller may be provided within a light bulb, a light socket, an extension light bulb socket or a light switch module.

Description

LIGHTING CONTROLLER

TECHNICAL FIELD

This invention relates to lighting controllers and in particular, though not solely, to electrical lighting controllers which adjust the power supplied to light sources, such as incandescent light bulbs, over a period of time.

BACKGROUND ART

Conventionally, there is practically no perceivable time delay between switching on an electric light source such as an incandescent bulb and full output light power occurring. Accordingly, the eyes of a person turning on a light switch in a dark room may need to adjust from virtual darkness to intense brightness virtually immediately. Often, especially in the elderly, the pupils of the eyes may take some time (in the order of 10's of seconds) to adjust to the abrupt change in brightness. Until the eyes adjust, squinting often results in order to reduce the amount of light entering the eyes. It may also be necessary to shade the eyes from the light and/or look away from the light. Worse still, a sudden increase in light on already dilated pupils may result in a form of sensory overload to the brain so that temporary blindness ensues and a person will "see" a white light for a length of time (in the order of 10's of seconds).

Electrical dimmers are well known in which the power supplied to a light source may be adjusted so as to reduce power output in order to save energy and to extend the life of the light source. Such devices are often complex and involve expensive and/or sensitive componentry. These devices are also usually manually adjusted so that the intensity of light produced by a light source will virtually immediately reach and be maintained at its preset setting.

US4680536A and US5030890A disclose electronic dimmer circuits which also include means for providing a "soft start" feature to light sources such that the amount of power supplied to an incandescent light bulb is controllably increased over time in order to protect the dimmer components from the initial high currents ordinarily drawn by cold incandescent light bulbs. US4360743A and US5365162A both disclose electrical circuits which gradually increase power to light bulbs in order to extend the life of the bulb.

The circuits disclosed in all of these documents are relatively complex, utilising components such as triacs or SCRs, whose firing angle is adjusted in response to sophisticated and/or expensive control circuitry and/or a microprocessor. The incorporation of such sophisticated and costly components add to the total cost of the device, increase power consumption and reduce reliability.

All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.

It is acknowledged that the term 'comprise' may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, the term 'comprise' shall have an inclusive meaning - i.e. that it will be taken to mean an inclusion of not only the listed components it directly references, but also other non-specified components or elements. This rationale will also be used when the term 'comprised' or 'comprising' is used in relation to one or more steps in a method or process.

It is therefore an object of the present invention to provide a lighting controller which will go at least some way towards overcoming the above disadvantages or which will go at least some way towards meeting the above desiderata or which will at least provide the public with a useful choice.

DISCLOSURE OF INVENTION

Accordingly, in a first aspect the invention consists in a lighting controller for a light source, the lighting controller comprising: a pair of input voltage terminals adapted to receive an input voltage, a pair of output voltage terminals adapted for connection to the light source, and a temperature dependent impedance connected between a first of the input voltage terminals and a first of the output voltage terminals, wherein the remaining input and output terminals are connected together.

Preferably, the temperature dependent impedance is adapted to be positioned adjacent to said light source so that the temperature of said temperature dependent impedance is influenced by the temperature of said light source.

Preferably, said temperature dependent impedance comprises a negative temperature coefficient resistor having a predetermined room temperature resistance, a predetermined temperature versus resistance relationship and a predetermined working temperature resistance.

Preferably, the predetermined room temperature resistance is sufficiently high to limit the power provided to the light source to between about 2 to about 15 Watts and the working temperature resistance of the temperature dependent impedance is less than about 10% of the room temperature resistance.

Preferably, a substantially temperature independent resistor is connected in parallel with said temperature dependent impedance in order to control the initial current output by the controller.

Preferably, said substantially temperature independent resistor has a resistance value which, in combination with the room temperature resistance of said temperature dependent impedance and the internal resistance of said light source, provides an initial power of between about 2 to about 15 Watts to said light source.

Preferably, a temperature dependent switching means is connected in parallel with said temperature dependent impedance, wherein said switch closes above a predetermined temperature and wherein the switch is adapted to be positioned adjacent to said light source so that the temperature of said switch is influenced by the temperature of said light source.

Preferably, said temperature dependent switching means closes at a first predetermined temperature as the temperature of the switching means increases and reopens at a second predetermined temperature as the temperature of the switching means decreases, wherein the first and second predetermined temperatures are different.

Preferably, the first predetermined temperature is greater than the second predetermined temperature.

Preferably, said first predetermined temperature is about 60°C and said second predetermined temperature is about 50°C.

Preferably, said temperature dependent switching means comprises a bimetallic switch.

In a second aspect, the invention consists in an incandescent light bulb comprising: a filament, a sealed chamber in which the filament is positioned, fixing means adapted to enable the light bulb to be retained in a light socket, electrical contact means provided on said fixing means and adapted to receive electrical power from said light socket, and a lighting controller according to the first aspect which receives electrical power from said electrical contact means via said pair of input voltage terminals and outputs power to said filament via said pair of output voltage terminals.

Preferably, said lighting controller is positioned within said fixing means.

Preferably, said fixing means includes a male Edison screw component or a male bayonet fixing.

In a further aspect, the invention consists in a light socket comprising: retaining means adapted for receiving and retaining a light bulb, electrical contact means adapted to provide electrical power to said light bulb, and a lighting controller according to the first aspect which receives electrical power from a source of electrical power via said pair of input voltage terminals and outputs electrical power to said light bulb via said pair of output voltage terminals.

Preferably, said retaining means includes a female Edison screw component or a female bayonet fixing.

In a still further aspect, the invention consists in an extension light bulb socket comprising: fixing means adapted to connect to a light bulb socket, a lighting controller according to the first aspect, and retaining means adapted to receive and connect to a light bulb, wherein said fixing means includes electrical contact means adapted to receive electrical power from said light socket via said pair of input voltage terminals and connected to transfer said power to said lighting controller means, and wherein said retaining means includes further electrical contact means adapted to receive electrical power output by said lighting controller means via said pair of output voltage terminals and to transfer said output power to said light bulb.

In a still further aspect, the invention consists in a light switch module for controlling transfer of power from a power source to a light source, the light switch module comprising switching means connected in series with one of the pair of input voltage terminals of a lighting controller according to the first aspect, the switching means capable of attaining an open or non-conducting state and a closed or conducting state so that, when in a conducting state, power is supplied from the power source, to the input voltage terminals of the lighting controller and the output voltage terminals of the lighting controller are adapted to provide power to the light source.

BRIEF DESCRIPTION OF DRAWINGS

Further aspects of the present invention will become apparent from the following description which is given by way of example only and with reference to the accompanying drawing in which:

Figure 1 is a basic circuit diagram of a lighting controller according to an embodiment of the present invention connected to a power source and a light source, Figure 2 is a front elevational view of a light bulb within a partially cut-away view of a light socket adaptor or an extension light bulb socket including the lighting controller of Figure 1 ,

Figure 3 is a front elevational view of a light bulb including the lighting controller of Figure 1 ,

Figure 4 is a cross-sectional front elevational view of a light bulb socket including the lighting controller of Figure 1, and

Figure 5 is a perspective view of a light switch module including the lighting controller of Figure 1. BEST MODES FOR CARRYING OUT THE INVENTION

With reference to the drawings and in particular Figure 1, a circuit diagram for a lighting controller 1 is shown including a temperature dependent impedance, for example a negative temperature coefficient (NTC) resistor 2 (that is, a resistor whose resistance decreases with increasing temperature), a resistor 3 and a temperature dependent switch, for example a bimetallic switch 4. Resistor 3 is substantially temperature independent.

The bimetallic switch 4 should be physically positioned adjacent to the light source 10 so that its temperature is influenced by or commensurate with that of the light source. The negative temperature coefficient resistor 2 could be physically positioned adjacent to the light source also so that its temperature is influenced by or commensurate with that of the light source however this is not essential. The NTC resistor 2 could be positioned remotely of the light source (for example in a light switch module - see Figure 5) including a switch. In this embodiment, the current flowing through the NTC resistor may be relied upon to provide heating to the NTC resistor. As the temperature of the NTC resistor further increases, its resistance will decrease thereby increasing the current and heating caused by that current.

In another embodiment, the entire lighting controller circuitry including the temperature dependent components could be located within the end cap (either bayonet or Edison screw varieties) of an incandescent light bulb so that the present invention is retrofittable as it may be utilised in the same way as or in place of a conventional light bulb. In this embodiment, heat from the light source would be provided directly to the NTC resistor 2 thereby "kick starting" its resistance transformation.

It should however be appreciated that resistor 3 and bimetallic switch 4 are optional and that the lighting controller 1 may include either:

1. a temperature dependent impedance only,

2. a temperature dependent impedance and a substantially temperature independent resistor,

3. a temperature dependent impedance and a bimetallic switch, or 4. a temperature dependent impedance, a substantially temperature independent resistor and a temperature dependent switch.

It can be seen that, where provided, the resistor 3 and temperature dependent switch 4 are connected in parallel with the temperature dependent impedance 2.

Lighting controller 1 includes a pair of input voltage terminals 5,6 connected to respective output terminals such as line and neutral connections of a power supply 7 (such as a normal household power supply of 110V/230V AC). A pair of output voltage terminals 8,9 are also provided, to which a light source, such as an incandescent light bulb 10 is connected. Use of the word "terminal" herein should not be interpreted as implying that physical connection points need be attached to conductors in the circuit. Each "terminal" referred to herein could simply comprise a point or portion of a conductor in the circuit.

The present invention aims to gradually (over about 10s to about 20s) increase the brightness of a light source when switched on to allow the eye time to adjust to the new level of light intensity. In order to achieve this aim, the following properties are considered important:

1. The initial brightness emitted by the source must be low enough not to dazzle but be sufficient to signal to a user that the light source is working.

2. The rate at which the brightness increases (or ramps) could be linear or exponential or any other suitable rate of change.

3. The time taken for the bulb to reach full brightness must be long enough that the user's eyes are given time to adjust but short enough that the user is not waiting for sufficient usable light to fill the room.

In the embodiment of the invention in which only a temperature dependent impedance is included in the circuit between the power source and the light source, the temperature independent impedance must be manufactured to include parameters which meet all three of the above requirements.

Conventionally, negative temperature coefficient resistors are designed to reach their minimum resistance within a few milliseconds. As mentioned above, the present invention requires resistance between the power source and light source to reduce gradually over a period of 10s to 20s (depending on the ramping time required). It is also known that the resistance of the filament of an incandescent light bulb increases with increasing temperature.

The design of the negative temperature coefficient resistor 2 is a non-linear process because its resistance is dependent on its temperature, which is affected by the surrounding temperature in addition to the current which passes through it. However the surrounding temperature is significantly affected by the heat produced by the light source 10 which in turn is influenced by the current which the negative temperature coefficient resistor 2 allows to flow.

By recording the temperature surrounding the negative temperature coefficient resistor 2 and simultaneously recording its resistance, it is possible to derive an ideal temperature versus resistance curve for the negative temperature coefficient resistor. Using this system the negative temperature coefficient resistor can be designed to include four key features:

1. a predetermined initial ("cold" or room temperature - around 20°C) resistance that allows the bulb to glow at a predetermined brightness (for example between about 2 to about 15 Watts or more preferably about 5 Watts)

2. a predetermined resistance versus temperature curve to ensure that brightness is ramped up at a desired rate and following a predetermined path (for example linear or exponential),

3. a final (or "hot" - for example, above about 60°C) resistance that is sufficiently small so as not to waste any or minimal power (for example, preferably the hot resistance is less than about 10% of the room temperature resistance so that at least about 90% or 95% of the power is consumed by the light source), and

4. physical dimensions to fit within its housing (for example, the metal casing of either bayonet or Edison screw light bulbs or a light switch module).

These four properties can be controlled by varying the dimensions (height and diameter) of the negative temperature coefficient resistor, by changing the properties of the negative temperature coefficient material, by altering the insulation around the negative temperature coefficient material, and by varying the shape of the component (for example solid or hollow with different wall thicknesses). Furthermore, the required resistance parameters of the negative temperature coefficient resistor also depend on the power rating of the light source and its initial "cold" and final "hot" resistance.

As an alternative to the above "ideal" embodiment in which the specifications of negative temperature coefficient resistor are manipulated to obtain each of the desired physical properties, resistor 3 and/or bimetallic switch 4 may be combined in parallel with a non-ideal negative temperature coefficient resistor 2. The non-ideal negative temperature coefficient resistor in this alternative embodiment only controls the ramping up of the voltage (or power) supplied to the light source and therefore the initial "cold" and/or final "hot" resistance parameters of the negative temperature coefficient resistor need not be within precise tolerances. The properties of the negative temperature coefficient resistor 2 may therefore only need to be tailored to ensure that it ramps the brightness of the light source 10 at the correct rate and in the correct manner (that is for example linear or exponential).

The initial or "cold" brightness of the light source may be controlled by resistor 3 which is preferably of a fixed value. For example, resistor 3 may have a resistance of around 4kΩ which when acting in parallel with the cold/room temperature negative temperature coefficient resistor 2 (for example having a resistance of 4kΩ) produces a total resistance of 2kΩ. For a 75W/230V incandescent light bulb 10 having an initial resistance of about 705Ω this will result in approximately 5W initially provided to the light bulb. The value of resistor 3 can be altered to adjust the initial brightness and will need to be different for light bulbs of different nominal power rating in order to achieve the same level of initial brightness. This can easily be determined by those skilled in the art using Ohm's law (V=I.R) and its derivatives.

The final or "hot" brightness of the bulb may be controlled by bimetallic switch 4 which is designed to close once the NTC resistor and/or light source and/or bimetallic switch reaches a predetermined temperature. Once switch 4 has closed it removes resistor 3 and/or negative temperature coefficient resistor 2 from the circuit and ensures that the light source 10 is operating at 100% efficiency (that is, no power is wasted in the two resistors 2,3).

Bimetallic switch 4 also ensures that resistors 2,3 are only used during start up of the light source 10 which should ensure a longer life expectancy of the components. The temperature at which bimetallic switch 4 closes may be altered depending on the heat output from the light source (that is, its power rating) and the length of time in which the light source is required to ramp up to full brightness.

Bimetallic switch 4 may also be provided with an amount of hysteresis to ensure that once it is closed it stays closed while the light source is in operation and will only open once the light source has cooled sufficiently (that is, once the light source has been switched off for a sufficient period of time). For example the switch may be designed to close at 60°C but not reopen until the light source cools to 50°C. This ensures that the negative temperature coefficient resistor 2 is allowed to drop in temperature sufficiently between successive uses as the temperature ramp action of the temperature dependent resistor 2 may only be observed within a range of temperatures, below its steady state operating temperature. The cooling of the negative temperature coefficient resistor 2 may, for example, take up to 5 minutes depending on whether insulation is used about the component and the length of time which it has been in operation for.

As mentioned above, the lighting controller 1 according to the present invention may be incorporated into a standard incandescent light bulb so that it looks substantially like a conventional light bulb but operates significantly differently (see Figure 3). The standard looking light bulb incorporating the lighting controller and having either a bayonet or Edison screw type end cap fitting would then fit within conventional household, commercial or industrial light fittings. The above described lighting controller could be fitted within the glass bulb 14 or the metallic base 15 of the bulb.

Alternatively, the lighting controller according to the present invention could be incorporated within a standard type light bulb socket 16 (see Figure 4) for attachment to walls, ceilings or the like or for use in lamps or chandelier-type lighting arrangements. Furthermore, the lighting controller could be incorporated within an extension socket 11 (see Figure 2) having at one end a male end cap fitting and the opposite end a female light bulb receiving socket. The extension socket could then be inserted into conventional light bulb sockets and receive a conventional light bulb 12 in its female end. The extension socket could also act as a converter between bayonet type and Edison screw type fittings by having one of each type of fitting at opposite ends.

As previously mentioned, in a further alternative embodiment, the lighting controller 1 according to the present invention could be incorporated within a light switch module 13 or housing adapted to be mounted on a wall for example as shown in Figure 5.

Accordingly, at least in its preferred embodiment, incandescent light bulbs incorporating the present invention will have a longer life expectancy than conventional incandescent light bulbs. Most conventional light bulbs blow during start- up as the filament decays with use and is most susceptible to failure when cold. As the present invention is designed to slowly increase the power supplied to the filament it will also reduce the thermal shock placed thereon and thereby increase the life of the light bulb.

Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof.

Claims

1. A lighting controller for a light source, the lighting controller comprising: a pair of input voltage terminals adapted to receive an input voltage, a pair of output voltage terminals adapted for connection to the light source, and a temperature dependent impedance connected between a first of the input voltage terminals and a first of the output voltage terminals, wherein the remaining input and output terminals are connected together.

2. A lighting controller as claimed in claim 1 , wherein the temperature dependent impedance is adapted to be positioned adjacent to said light source so that the temperature of said temperature dependent impedance is influenced by the temperature of said light source.

3. A lighting controller as claimed in claim 1 or claim 2, wherein said temperature dependent impedance comprises a negative temperature coefficient resistor having a predetermined room temperature resistance, a predetermined temperature versus resistance relationship and a predetermined working temperature resistance.

4. A lighting controller as claimed in claim 3, wherein the predetermined room temperature resistance is sufficiently high to limit the power provided to the light source to between about 2 to about 15 Watts and the working temperature resistance of the temperature dependent impedance is less than about 10% of the room temperature resistance.

5. A lighting controller as claimed in claim 1 , wherein a substantially temperature independent resistor is connected in parallel with said temperature dependent impedance in order to control the initial current output by the controller.

6. A lighting controller as claimed in claim 5, wherein said substantially temperature independent resistor has a resistance value which, in combination with the room temperature resistance of said temperature dependent impedance and the internal resistance of said light source, provides an initial power of between about 2 to about 15 Watts to said light source.

7. A lighting controller as claimed in claim 5 or claim 6, wherein a temperature dependent switching means is connected in parallel with said temperature dependent impedance, wherein said switch closes above a predetermined temperature and wherein the switch is adapted to be positioned adjacent to said light source so that the temperature of said switch is influenced by the temperature of said light source.

8. A lighting controller as claimed in claim 7, wherein said temperature dependent switching means closes at a first predetermined temperature as the temperature of the switching means increases and reopens at a second predetermined temperature as the temperature of the switching means decreases, wherein the first and second predetermined temperatures are different.

9. A lighting controller as claimed in claim 8, wherein the first predetermined temperature is greater than the second predetermined temperature.

10. A lighting controller as claimed in claim 8 or claim 9, wherein said first predetermined temperature is about 60°C and said second predetermined temperature is about 50°C.

11. A lighting controller as claimed in any one of claims 7 to 10, wherein said temperature dependent switching means comprises a bimetallic switch.

12. An incandescent light bulb comprising: a filament, a sealed chamber in which the filament is positioned, fixing means adapted to enable the light bulb to be retained in a light socket, electrical contact means provided on said fixing means and adapted to receive electrical power from said light socket, and a lighting controller according any one of claims 1 to 11 which receives electrical power from said electrical contact means via said pair of input voltage terminals and outputs power to said filament via said pair of output voltage terminals.

13. An incandescent light bulb as claimed in claim 12, wherein said lighting controller is positioned within said fixing means.

14. An incandescent light bulb as claimed in claim 12 or claim 13, wherein said fixing means includes a male Edison screw component or a male bayonet fixing.

15. A light socket comprising: retaining means adapted for receiving and retaining a light bulb, electrical contact means adapted to provide electrical power to said light bulb, and a lighting controller according to any one of claims 1 to 11 which receives electrical power from a source of electrical power via said pair of input voltage terminals and outputs electrical power to said light bulb via said pair of output voltage terminals.

16. A light socket as claimed in claim 15, wherein said retaining means includes a female Edison screw component or a female bayonet fixing.

17. An extension light bulb socket comprising: fixing means adapted to connect to a light bulb socket, a lighting controller according to any one of claims 1 to 11 , and retaining means adapted to receive and connect to a light bulb, wherein said fixing means includes electrical contact means adapted to receive electrical power from said light socket via said pair of input voltage terminals and connected to transfer said power to said lighting controller means, and wherein said retaining means includes further electrical contact means adapted to receive electrical power output by said lighting controller means via said pair of output voltage terminals and to transfer said output power to said light bulb.

18. An extension light bulb socket as claimed in claim 17, wherein said fixing means includes a male Edison screw component or a male bayonet fixing.

19. An extension light bulb socket as claimed in claim 17 or claim 18, wherein said retaining means includes a female Edison screw component or a female bayonet fixing.

20. A light switch module for controlling transfer of power from a power source to a light source, the light switch module comprising switching means connected in series with one of the pair of input voltage terminals of a lighting controller according to any one of claims 1 to 11 , the switching means capable of attaining an open or non-conducting state and a closed or conducting state so that, when in a conducting state, power is supplied from the power source, to the input voltage terminals of the lighting controller and the output voltage terminals of the lighting controller are adapted to provide power to the light source.