WO2008140366A1

WO2008140366A1 - Cordless decorative light assembly

Info

Publication number: WO2008140366A1
Application number: PCT/SE2007/000488
Authority: WO
Inventors: I Sverige Ab Julgransljus
Original assignee: I Sverige Ab Julgransljus
Priority date: 2007-05-16
Filing date: 2007-05-16
Publication date: 2008-11-20
Also published as: CA2685559A1; WO2008140366A8; EP2147249A1

Abstract

A cordless light assembly comprises a remote control unit (9) and light units (1), each comprising a light source (3), an electric power storage device (7) for driving the light source and a. switching unit (5). When the switching units receive a wirelessly transferred signal. from the remote control unit the power to the respective light sources are switched on and they start to emit light for only a predetermined time period after which, if no signal from the remote control unit is received, they stop to emit light. If a signal is received during the predetermined time, the light sources continue to emit light during a new time period. In receiving the signal, a voltage at a control terminal (12) of a controllable switch (11) in a light unit can be made to be sufficient to control the switch to a conducting state, this voltage decreasing gradually to eventually not being sufficient to control the switch to the conducting state. The signal from the remote control unit can be inductively transferred in a transformer coupling, the remote control unit having a primary coil (21) and the light units secondary coils (13).

Description

CORDLESS DECORATIVE LIGHT ASSEMBLY

TECHNICAL FIELD

The present invention relates to a cordless decorative light assembly and components thereof, in particular to a light assembly for Christmas tree decorations and the like, and also to a method of driving a light unit included in a cordless decorative light assembly. BACKGROUND

Cordless, decorative light assemblies typically comprise a plurality of electric light units, each comprising a light emitting diode (LED) powered by a chemical battery or cell, the on-off- state of the light unit controlled by a wirelessly controlled switch, see e.g. the published International patent application WO 2006/204548 and published U.S. patent application 2001/0030862. The wireless control is typically accomplished using infrared (IR) light or radio waves, the latter called radio frequency (RF) control.

However, RF control requires that the receivers of the RF signal in the individual light units are powered even in the standby-state in which the lights are not illuminated since they must be always ready to receive an activating signal. Also, the signal to the switch in each unit may require a considerable electric current when the unit is activated and illuminated. These effects reduce the possible total time during which the light units can be illuminated. Also, in order to use available frequency bands it may be necessary to include some simple electronic logic circuits in each unit so that they can be uniquely addressed by a signal from a remote control unit, thereby not interfering with other signals in the same frequency band. Such circuits will also add to the electrical current consumed at least in the activated state and also to the complexity and hence the cost of each light unit.

IR-control also consumes considerable power in the standby-state. IR-control is basically optical which may make it unsuitable in cases where there is a risk that there is some obstacle between the light unit and the remote controller. SUMMARY

It is an object of the invention to provide a cordless light unit that efficiently uses the local power supply or power storage housed in the unit.

It is another object of the invention to provide an assembly comprising cordless light units and a remote control unit in which a signal from the remote to the cordless light units is efficiently transmitted.

Generally, a cordless light unit may inductively or in some other suitable way, e.g. using radio transmission, receive a signal for making electric current from the local power storage, e.g. an electrochemical cell or battery, to be provided to the light source of the unit. After receiving the signal, the light source continues to be activated emitting light during a limited time period at the end of which a new signal can be received to make the light source continue to emit light. If no new signal is received within said limited time period the light emitted from the light source will gradually be weaker and weaker to finally stop to be emitted. The timing for the limited time period can be set by a simple electric circuit having a suitable time constant, so that e.g. an electric voltage controlling a switch to make it take an ON-state is applied to .said simple electric circuit and hence decays.

Generally also, a cordless light assembly comprises a remote control unit and light units, each comprising a light source, an electric power storage device for driving the light source and a switching unit. When the switching units receive a wirelessly transferred signal, also called an activating signal, from the remote control unit the power to the respective light sources are switched on, by e.g. setting controllable switches to an on-state or a conducting state, and they start to emit light for only a predetermined time period after which, if no signal from the remote control unit is received, they stop to emit light, by e.g. setting the respective controllable switches to an off-state or non-conducing state. If a signal is received during the predetermined time, the light sources continue to emit light during a new time period. In receiving the signal, a voltage at a control terminal of a controllable switch in a light unit can be made to be sufficient to control the switch to a conducting state, this voltage (the absolute value thereof) decreasing gradually to eventually not being sufficient to control the switch to the conducting state. The signal from the remote control unit can be inductively transferred in a transformer coupling, the remote control unit then having a primary coil and the light units secondary coils.

The power that has be received in the light units can be kept very small and no logic circuits for switching on/off are required in the light units. The electric power provided from the power supply in a light unit is almost only used to drive the light emitting device in the light unit, this giving the light units a long life-time. Some electric power is always dissipated from the local power storage by self-discharge but otherwise the power of the power storage is almost entirely used for driving the light source.

Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the methods, processes, instrumentalities and combinations particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

While the novel features of the invention are set forth with particularly in the appended claims, a complete understanding of the invention, both as to organization and content, and of the above and other features thereof may be gained from and the invention will be better appreciated from a consideration of the following detailed description of non-limiting embodiments presented hereinbelow with reference to the accompanying drawings, in which:

- Fig. 1 is a schematic of a light unit included in a cordless decorative light assembly,

- Fig. 2 is a schematic of a cordless decorative light assembly including light units and a remote control unit,

- Fig. 3 is a schematic of electric circuits in a light unit and a remote control unit included in a cordless decorative light assembly,

- Fig. 4 is a more detailed circuit diagram of the remove control unit of Fig. 3, and

- Fig. 5 is an alternative circuit diagram of a light unit included in a cordless decorative light assembly.

DETAILED DESCRIPTION

In Fig. 1 a cordless light unit or illumination unit 1, intended for e.g. decorative purposes, is illustrated. The light unit includes a light source 3, such as a light emitting diode (LED) or a light bulb, connected through a switching unit 5 to an electric power storage device, herein called a power supply 7, e.g. an electro-chemical battery 5. Typically, as illustrated in Fig. 2, a plurality of light units 1 are provided, e.g. arranged in a Christmas tree, and they are all remotely controlled by a remote control device 9.

The switching units 5 are controlled to take a closed position or conductive state, in which electrical current from the power supplies 7 is provided to the light sources, by inductively receiving electric current from the remote control device 9. Hence, as seen in the circuit diagram of Fig. 3, the switching unit 5 includes a main switch 11, typically a semiconductor switch such as a field effect transistor (FET), through which the light source is connected to the power supply. The switch can on its control terminal 12, the gate, receive activating current from a first end of a coil 13 in which electrical current can be induced. In the circuit diagram the activating current is used to control another assisting switch 15 that may be e.g. a bipolar transistor and is responsive also to very small currents, the assisting switch allowing, when its control terminal 16 such the base terminal receives an electrical current of a sufficient intensity, electrical current from the power supply 7 to be conducted to a first electrode of a capacitor 17 to charge it. The other, second electrode of the capacitor is connected to a second terminal of the coil 13 that is in turn connected to the negative terminal of the power supply 7 taken e.g. to have a ground potential in the circuit. A resistor 19 is connected in parallel to the capacitor 17 and the end of the parallel capacitor-resistor combination 17, 19 that is not connected to the negative terminal of the power supply is connected to the control terminal 12 of the main switch 11.

The remote control unit 9 also includes a coil 21 that is connected to a control circuit 23 and receives electric power e.g. from the public electricity distribution network through a cable 25. When the ON-key 29 of the remote control unit is depressed, the control circuit allows alternating current to be provided to its coil 21 during a relatively short time period, typically about 1 s and generally in the range of e.g. 0.2 - 5 s or 0.2 - 2 s, and hence an alternating magnetic field is created that interacts with: the coils 13 of the light units 1, inducing a current therein. The induced electrical current is used to make the main switches 11 conduct and hence the light sources 3 are illuminated. The electrical current supplied by the assisting switch 15, that is in a conducting state, from the power supply 7 to the control terminal 12 builds an electrical voltage over the capacitor 17, i.e. between the control terminal 12 of the main switch and the negative terminal of the power supply. When this voltage has a sufficient magnitude the main switch 11 is controlled to take a conducting state and then the light source 3 is illuminated.

After the relatively short time period during which a current is induced in the coils 31 of the light units 1, the voltage over the capacitors 17 slowly decays due to the fact that the capacitors are discharged through the respective parallel resistors 19 and possibly, in many cases to a very small extent, by some current flowing through the main switches 11 from the control terminals 12 thereof to their terminals connected to said ground potential. Finally the voltage over the capacitors takes such a low value that the main switches 11 stop to conduct. Before this time, that can be set by suitably selecting the time constant of the capacitor-resistor combinations, the control circuit 23 of the remote control unit has again provided alternating current to the coil 23, this inducing current in the coils 13 of the light units 1 and hence increasing the voltage between the control terminal 12 of the main switches and the negative power supply terminal.. For example, exciting pulses of alternating current can be supplied with intervals in the range of 1 - 5 minutes or 1 - 3 minutes.

If the OFF-key 29 of the control unit 9 is depressed, the control circuit 23 stops to periodically supply alternating current to the coil 21. Then obviously, the light units 1 will not receive any more induced current and the light sources thereof stop to emit light after some time period.

In the inductive or transformer coupling between the coil 21 of the remote control unit 9 and the coils 13 in the light units 1 the magnetic field of the externally activated, primary coil interacts with the coils of the light units. In the inductive transfer of energy or power e.g. only very small currents, e.g. < 100 μA, can be induced in the receiving, secondary coils. Inductive power transfer can only be made over relatively small distances and is not easily exposed to interference from other signals. It should be reminded that even strong magnetic fields decay rapidly when moving to increased distances from the primary, exciting coil. The primary and second coils do not have to be accurately tuned to each other. Typically the frequency of the exciting electric current can be about 100 kHz, this giving a wide-band transfer of energy. The receiving,' secondary coils 13 in the light units 1 can as illustrated in Fig. 1 include wirings in two subcoils around the battery 7, the subcoils located in rectangular planes. Also three orthogonal coils can be used as disclosed in U.S. patent 6,150,986 giving a very good reception for any relative position of the light units 1 and the remote control unit 9. -Alternatively, . the receiving, secondary coils can be configured as small coils having ferrite cores, not shown. For example, miniature inductors Sd75 from Neosid having an inductance of 1000 μH and comprising a ferrite core can be used. Also, the primary coil 21 can comprise a winding and a ferrite core, the winding e.g. having about 300 turns, a diameter of 10 mm and a length of 60 mm.

The internal components of the remote control device 9 can e.g. be configured as illustrated in the circuit diagram of Fig. 5. The power supply 31 is here shown as a battery of electrochemical cells, such a battery then suitably having a much larger capacity than the power supplies 7 of the individual light units 1. The ON and OFF keys 27, 29 are shown as electrical circuit breakers which when depressed control the state of a flip-flop circuit 33. Hence, when the ON key is depressed the flip-flop circuit controls a timer circuit 35 to start generating a pulse train. The generated pulse train can as mentioned above comprise pulses having a length of about 1 s and time intervals between the pulses of about 1 - 2 min. The pulses are provided to an oscillator 37 which give an oscillating electrical signal of a frequency e.g. about 100 kHz only during the time periods of the pulses. Hence, a signal having isolated bursts of an electric oscillating signal is obtained that is provided to a buffer step 39 that transforms the oscillating signal to be capable of driving the coil 21.

Another electrical circuit for use in the light units 1 is shown in Fig. 6. Here the terminal of the coil 13 that is not connected to a terminal of the power supply 7 is connected to the first electrode of the capacitor 17 through a diode 41 and possibly an amplifier 43. The main switch 11 is shown as a general semiconductor switch. There is no resistor connected in parallel to the capacitor and hence the capacitor is discharged only through the semiconductor switch, through e.g. the base-emitter resistance in the case where the main switch is a bipolar transistor. If the amplifier 43 includes a semiconductor switch that is connected in the same way and is similar to the assisting switch 15 of Fig. 4, the amplifier does not consume any electrical power when no activating electrical oscillating bursts are received. If its configured as some standard amplifier it may consume some power even in the standby state.

While specific embodiments of the invention have been illustrated and described herein, it is realized that numerous other embodiments may be envisaged and that numerous additional, advantages, modifications and changes will readily occur to those skilled in the art without departing from the spirit and scope of the invention. Therefore, the invention in its broader aspects is not limited to the specific details, representative devices and illustrated examples shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents. It is therefore to be understood that the appended claims are intended to cover all such modifications and changes, as¹ fall within a, true spirit and scope of the invention. Numerous other embodiments may be. envisaged without departing from the. spirit and scope of the invention.

Claims

1. A cordless light unit comprising a light source, an electric power storage device for driving the light source and a switching unit adapted to receive a wirelessly transferred signal from a remote control unit, the switching unit adapted to control that the power to the light source is switched on and off, characterized in that, when the switching unit receives the. wirelessly transferred signal, the switching unit is adapted to switch the power to the light source on during a time period having a predetermined length, after which, if no new wirelessly transferred signal is received, the power to the light source is switched off, and if a new wirelessly transferred signal is received during the predetermined period, start, from the time when the wirelessly transferred signal was received, a new time period having the predetermined length during which the power to the light source is switched on.

2. A cordless light unit method, characterized in that the predetermined time is in the range of 1 - 5 min, in particular in the range of 1 - 3 min.

3. A cordless light unit according to claim 1, characterized in that the switching unit includes a controllable switch for switching the power to the light source on and off and is adapted to make, when the switching unit receives the wirelessly transferred signal, a voltage at a control terminal of the controllable switch to be sufficient to control the switch to a conducting state thereby switching the power to the light source on, said sufficient voltage at the control terminal being, when a signal is not any longer received, gradually or continuously changed to taking, after a predetermined time period, a value not sufficient to control the switch to a conducting state, the power to the light source then being switched off.

4. A cordless light unit according to claim 1, characterized by an electric coil working as a secondary coil in an inductive coupling or transformer coupling, the electric coil connected to the control terminal of the controllable switch so that, when the electrical coil is inductively coupled to a primary electrical coil and then receiving induced electric power, the voltage at said control terminal is being changed to be sufficient to control the switch to a conducting state thereby switching the power to the light source on, said voltage at the control terminal, when the electric coil is not any longer inductively coupled to any primary coil, being gradually or continuously . changed to taking, after the predetermined time period, a value not sufficient to control the switch to a conducting state, the power to the light source then being switched off.

5. A cordless light unit according to claim 4, characterized in that one terminal of the electric coil is connected to the control terminal through a rectifying element and that the control terminal is connected to one electrode of a capacitor, the voltage over the capacitor being discharged through a resistor connected in parallel to the capacitor, said predetermined time period being determined by the time constant of the capacitor-resistor combination.

6. A cordless light assembly comprising at least one light unit according to any of claims

1 - 5 and a remote control unit, the remote control unit comprising a signal transmitting unit for wirelessly transmitting a signal to said at least one light unit.

7. A cordless light assembly according to claim 6, characterized in that the signal transmitting unit in the remote control unit comprises a coil acting as a primary coil in an inductive coupling or transformer coupling between the remote control unit and said at least one light unit.

8. A cordless light assembly according to claim 7, characterized in that the signal transmitting unit in the remote control unit comprises a timer circuit providing pulses during which an alternating current is provided to the coil in the remote control unit.

9. A method of driving a cordless light unit comprising a light source, an electric power storage device for driving the light source and a switch for switching the power to the light source on, characterized by the successive steps of:

- transmitting wirelessly an activating signal, - receiving the activating signal,

- using the received activating signal to set the switch in the on-state thereof to provide electric power from the electric power storage device to the light source to illuminate it, and

- setting the switch in the off-state if no activating signal has been received within a predetermined time.

10. A method according to claim 9, characterized in that the predetermined time is in the range of 1 - 5 min, in particular in the range of 1 - 3 min.

11. A method according to claim 9, characterized in that in the steps of receiving the activating signal and using the received activating signal, a voltage at a control terminal of the controllable switch is being changed to be sufficient to control the switch to the on-state thereby switching the power to the light source on, said sufficient voltage at the control terminal being, when an activating signal is not any longer received, gradually or continuously changed to taking, after a time period, a value not sufficient to control the switch to the on-state, the power to the light source then being switched off.

12. A method according to claim 9, characterized in that in the step of receiving the activating signal, the activating signal is received by a coil in the light unit, the coil working as a secondary coil in an inductive coupling or transformer coupling.

13. A method according to claim 12, characterized in that in the step of receiving the activating signal, when the electrical coil is inductively coupled to a primary electrical coil and receives induced electric power, the induced electric power is provided to a control terminal to gradually change the voltage at the control terminal, the voltage thereby being, during the activating signal, changed to be sufficient to control the switch to the on-state thereby switching the power to the light source on.

14. A method according to claim 13, characterized in that the voltage at the control terminal is the voltage. at one electrode of a capacitor, the capacitor being discharged through . a. resistor, so that when the electric coil is not any longer inductively coupled to any primary coil, . the voltage at the control terminal is being gradually or continuously changed to taking, after said predetermined time period,, a value not sufficient to control the switch to an on-state, the power to the light source then being switched off.