WO2009150562A1

WO2009150562A1 - Wireless sensor device and illumination system comprising such a device

Info

Publication number: WO2009150562A1
Application number: PCT/IB2009/052268
Authority: WO
Inventors: Willem F. P. Pasveer; Roger P. A. Delnoij; Theodorus J. P. Van Den Biggelaar; Adrianus Sempel
Original assignee: Koninklijke Philips Electronics NV
Current assignee: Koninklijke Philips NV
Priority date: 2008-06-11
Filing date: 2009-05-29
Publication date: 2009-12-17
Anticipated expiration: 2010-12-11

Abstract

The invention relates to an illumination system and to a wireless sensor device for such an illumination system. The wireless sensor device comprises a light level sensor and an energy accumulator for providing power to the wireless sensor device. The light level sensor comprises a substrate and at least one photo-electric detector provided on the substrate and arranged for detecting light. Also a switched capacitor (voltage) converter is provided on the same substrate. The converter is arranged to convert a first signal (voltage) from the photo-electric detector to a second signal (voltage) for accumulating energy in the energy accumulator.

Description

Wireless sensor device and illumination system comprising such a device

FIELD OF THE INVENTION

The invention relates to the field of wireless sensor devices for lighting control. More specifically, the invention relates to a wireless sensor device and an illumination system comprising such a wireless sensor device, wherein the wireless sensor device comprises at least a light level sensor.

BACKGROUND OF THE INVENTION

In recent years, attention has increased for energy saving measures in the field of illumination of areas, such as rooms. As an example, control systems have been developed that activate light sources only when the presence of human beings is detected, using occupancy sensors (e.g. pyroelectric infrared sensors), and to adapt the level of artificial light from the light sources depending on the level of daylight in the area, using light level sensors. Occupancy sensors and light sensors may advantageously be used in combination.

The sensor devices typically need to be installed at particular locations in the area in order to fulfill the sensing function. Installation of such sensor devices is greatly facilitated by providing wireless sensor devices. Such sensor devices are capable of wireless transmission of the sensing data, or derivatives thereof, to the light sources (or a central controller thereof).

For true wireless sensor devices, not only the sensing data should be transmitted wirelessly, but also energizing the sensor devices should not require wire connections. A battery or other energy storage means may be used to accomplish such a wireless sensor device.

For such sensor devices, power consumption is critical. A shortcoming of such a true wireless sensor device is that batteries need to be replaced. This is not only inconvenient from a maintenance perspective, but the need for replacement may not always be readily apparent.

Recent developments are directed to using light level detectors both for sensing and for energy accumulation. As an example, WO2006/057322 discloses a wireless sensor device comprising a sensor defined by a photovoltaic cell. The photovoltaic cell senses an illumination level on the one hand and converts light into electrical energy for accumulating electric power in a power supply of the wireless sensor device.

There exists a need in the art for a less complex wireless sensor device capable of accumulating itself at least some of the energy it requires for operation.

SUMMARY OF THE INVENTION

A wireless sensor device comprising a light level sensor is proposed. The wireless sensor device also comprises an energy accumulator for powering the wireless sensor device. The light level sensor comprises a substrate and at least one photo electric detector provided on the substrate and arranged for detecting light. Also a switched capacitor (voltage) converter is provided on the same substrate. The converter is arranged to convert a first signal (voltage) from the photo electric detector to a second signal (voltage) for accumulating energy in the energy accumulator.

Moreover, an illumination system comprising a plurality of light sources and at least one such a wireless sensor device is proposed. The illumination system is configured for controlling one or more of the light sources in dependence on sensing data of said wireless sensor device.

Finally, a method for operating a wireless sensor device, comprising a light level sensor with a substrate carrying at least one photo electric detector and a switched capacitor (voltage) converter is proposed. Light is detected at the photo electric detector to provide a first signal (voltage). The first signal is converted to a second signal (voltage) using the switched capacitor converter in order to accumulate energy in an energy accumulator. The energy is then available for powering the wireless sensor device.

The photo electric detector may comprise one or more photo diodes. The energy stored in the energy accumulator can be used for providing power for one or more components of the wireless sensor device, such as the light level sensor, a further sensor (e.g. an occupancy sensor) and/or a transmitter. The switched capacitor device is used to convert (raise) a voltage signal from the at least one photo electric detector to a voltage signal sufficient for the energy accumulator. The integration of the at least one photo electric sensor and the switched capacitor converter on a single substrate provides a wireless sensor device of reduced complexity that is capable of accumulating itself at least some of the energy required for its operation, i.e. the light level sensor may be used for sensing purposes as well as for energy accumulation. On chip integration of the at least one photo electric detector and the converter provides ease of manufacturing and enables reduced dimensions of the wireless sensor device.

The embodiment of claim 2 enables integrating a single photo diode in a bulk CMOS process. The on-chip switched capacitor voltage convertor is used to boost the voltage from the photo diode to a level sufficient for the energy accumulator.

The embodiment of claim 3 enables quick charging of the energy accumulator under high light level conditions.

The embodiment of claim 4 allows the ratio between the sensing mode the energy accumulation mode to be chosen such that sufficient time is available for energy accumulation while sensing operation is not noticeably influenced. In particular, the controller is configured such that the sensing mode time is shorter than the energy accumulation mode time. Typically, the ratio of the sensing mode time to the energy accumulation mode time (in percents) is less than 1%. As an example, a sensing time of 1 minute may require an energy accumulation time of 5 hours. The embodiment of claim 5 enables the operation of the wireless sensor device to be controlled by the first signal, i.e. by the detected light level. As an example, enhanced sensing operation by the wireless sensor device may be promoted under high light level conditions and a lower level of activity during lower light level conditions. On the other hand, the embodiment allows enhanced charging operation (and thus lowered sensing operation) by the wireless sensor device if a low energy status for the energy accumulator is detected under high light level conditions.

The embodiment of claim 6 provides for a sensor device comprising an array of photo diodes, wherein each diode is tuned to be responsive to a specific wavelength range of the light to be detected. As a consequence, the amount of light for each wave length range can be determined. Such tuning may e.g. be obtained by using wavelength filters or by selecting materials with specific wavelength sensitivity characteristics. Although the wavelength selective properties of the array result in a considerable loss of energy that could potentially have been harvested, sufficient energy may still be available since the period of energy accumulation (the energizing mode) is long in relation to the period of light sensing (the sensing mode). The switched capacitor converter raises the signal from each photo diode of the array to a level sufficient for storing energy in the energy accumulator.

The embodiment of claim 7 provides the advantage of powering further sensors using energy stored in the energy accumulator. Such a further sensor may e.g. be an occupation sensor configured for detecting motion in an area of an objection (e.g. a human being) as defined in claim 8.

The embodiment of claim 9 is advantageous in that the transmitter for transmitting the sensing data is also powered from the energy accumulator. By providing multiple sensor devices in an area, as defined in the embodiment of claim 11, sensing data may be transmitted from these devices at mutually different times in order to allow sufficient energizing time for each individual sensor device.

Hereinafter, embodiments of the invention will be described in further detail. It should be appreciated, however, that these embodiments may not be construed as limiting the scope of protection for the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

Fig. 1 is a diagrammatic view of a room comprising a wireless sensor device and an illumination system according to an embodiment of the invention;

Figs. 2A and 2B show schematic illustrations of a wireless sensor device and an electrical circuit diagram according to a first embodiment of the invention; and

Figs. 3 A and 3B show schematic illustrations of a wireless sensor device and an electrical circuit diagram according to a second embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an illumination system 1 provided in an area (such as a room) occupied by a person P. The illumination system 1 comprises a wireless sensor device 2 and at least one armature 3 having one or more light sources (not shown). The area may e.g. be an office environment or a domestic environment. Alternatively, a central controller 4 may be present in the room to receive the signals from the wireless sensor device 2 and to provide operation commands for the armature or armatures 3 in the room.

It should be appreciated that the wireless sensor device 2 may be used in other applications. An example includes monitoring the operation of a light source in an installation, such as a UV light source in a purification device. Such a light source may be monitored in view of the life time of the light source (e.g. defect light source, light output below a particular threshold etc.).

In the present embodiment of FIG. 1, the wireless sensor device 2 controls the operation of the armature 3 in response to triggers sensed by the sensing device. Such triggers may include the entrance of the person P into a room or a change of the ambient light level in the room. The type of triggers that may be detected depend on the sensors comprised in the wireless sensor device 2. Examples of control of the operation of the armature 3 include switching on/off one or more light sources of the armature, adapting the color and/or brightness of the light emitted by the light sources, redirecting the light of the light sources etc.

FIGS. 2A-2B and FIGS 3A-3B provide schematic illustrations and circuit diagrams of wireless sensor devices 2 according to embodiments of the invention. The wireless sensor device 2 of these embodiments comprises a light level sensor 10, 20, respectively. Both wireless sensor devices 10, 20 comprise a substrate 11, 21 for the light level sensor 10, 20, an energy accumulator 12, 22, an occupancy sensor 13, 23 and a controller 14, 24.

The controller 14, 24 is configured for switching the operation of the light level sensor 10, 20 between a sensing mode (in which the light level in the room is registered) and an energy accumulation mode (in which energy is collected from light incident on the photo electric detector for energizing the energy accumulator 12, 22). Controller 14, 24 may be configured to obtain and process information on the energy status of the energy accumulator 12, 22 and control the switching between the sensing mode and the energy accumulation mode in dependence on the energy status. The controller 14, 24 may be integrated on the substrate 11, 21.

The energy accumulator 12, 22 comprises e.g. a rechargeable battery or a super capacitor.

The sensors of the wireless sensor device 2 are typically active only during a limited period of time as compared to the inactive periods. Therefore, sufficient time is available for energy accumulation in the inactive period.

In FIG. 2A, the light level sensor 10 has a single photo diode 15 provided on a CMOS substrate 11. The photo diode has a surface area in a range between 1-10 mm². A switched capacitor voltage converter 16 and a transmitter 17 are also provided on the CMOS substrate 11. In FIG. 3A, the light level sensor 20 comprises an array of photo diodes 25 on the substrate 21 wherein each diode 25 is tuned to be responsive to a specific wavelength range of the light to be detected. Such tuning may e.g. be obtained by using wavelength filters or by selecting materials with specific wavelength sensitivity characteristics. Substrate 21 further carries a switched capacitor voltage converter 26 and a transmitter 27. Each of the diodes 25 is connected separately to the switched capacitor voltage converter 26.

Switched capacitor voltage converters 16, 26 are arranged such that, in the energy accumulation mode of the wireless sensor device 2, a voltage generated by detecting light by the photo diode(s) 15, 25 is converted to a voltage for accumulating energy in the respective energy accumulators 12, 22. Basically, the voltage converters comprise one or more capacitors C and one or more switches (schematically illustrated by a switch S) for transferring charge from the capacitor C to the energy accumulator 12, 22 in a manner known as such. A variety of configuration of capacitors and switches is possible. The number of switches S and capacitors C is determined by the desired voltage conversion.

The switched capacitor voltage converters 16, 26 are configured to convert a voltage of -0.5V over the photo diode 15, 25 to 1.8V or higher for charging the energy accumulator 12, 22. Switched capacitor voltage converters are especially suitable since the components (switches, capacitors) of the converters can be readily integrated on-chip with the photo diodes 15, 25.

The switches of the switched capacitor voltage converters 16, 26 are switched back and forth at a particular switching frequency controlled by oscillators 18, 28 integrated in the converters 16, 26. The switching frequency can be controlled in dependence on the light level sensed by the photo diodes 15, 25, indicated by arrow CTRL. The operation of a wireless sensor device in accordance with an embodiment of the invention will now be described with reference to FIGS. 3A and 3B.

Wireless sensor device 2 is installed in the room of FIG. 1. Controller 24 controls switches Sl -S3 to switch the operation of the light level sensor 20 between a sensing mode (switches Sl -S3 in position A such that current Il runs) and an energy accumulation mode (switches Sl -S3 in position B such that current 12 runs). By switching S3 to position A, amplifier Al is powered to amplify the sensing signal of photo diode 25 in the sensing mode. Controller 24 is configured such that the time wherein switches Sl -S3 are in position A is longer than the time wherein switches Sl -S3 are in position B in order to have sufficient time for energizing the energy accumulator 22. Typically, the ratio of the time wherein switches Sl -S3 are in position A to the time wherein switches Sl -S3 are in position B is less than 1% in a particular time interval.

Switching between the two modes of operation may be dependent on the energy status of the energy accumulator 22. If photo detector 25 measures a high light level in the room, while the energy in the energy accumulator 22 is low, controller 24 may instruct switches Sl -S3 to remain in position B for a longer time period to boost the energy level in the energy accumulator 22. In this situation, also occupancy sensor 23 may be kept inactive for a longer time period.

Alternatively, switching between the two modes of operation may also be dependent only on the light level in the room as sensed by photo diode 25. If a high light level is detected, switches Sl -S3 may be kept in position A for a longer timer period for improved light sensing. Also, occupancy sensor 23 may be active for a longer period under such conditions.

In the energy accumulation mode, operation of the switched capacitor voltage convertor 26 may also be dependent on the sensed light level by photo diode(s) 25. In particular, the frequency of transferring charge from capacitor C to energy accumulator 22, using the oscillator 28 to control switch(es) S, may be higher under high light level conditions in the room to obtain accelerated energy accumulation in the energy accumulator 22. On the other hand, a lower frequency for switching the switch(es) S may apply under low light level conditions in the room. It is noted that in FIG. 3B, capacitor(s) C for the voltage conversion are not shown.

In the sensing mode, light level sensor 20 senses the light level in the room. The obtained information may be processed and the resulting sensing data are transmitted to armature 3 to control e.g. the brightness of the light sources. The operation of the occupancy sensor 23 may or may not be synchronized with the operation of the light level sensor 20. Occupancy sensor 23 is arranged for detecting motion in the room and may e.g. comprise a pyroelectric infrared sensor. If person P enters the room or moves, transmitter 27 (or another transmitter) informs armature 3 to switch on the light sources. The armature 3 is informed either directly or via the central controller 4 of the illumination system.

Processing of the information obtained from the occupancy and/or light level sensors may be done in controller 14, 24.

The illumination system 1 may comprise a plurality of wireless sensor devices 2. In order to allow each wireless sensor device 2 to accumulate sufficient energy, the wireless sensor devices 2 may transmit sensing data at different times.

Claims

CLAIMS:

1. A wireless sensor device (2) comprising a light level sensor (10;20) and an energy accumulator (12;22) for providing power for said wireless sensor device, wherein said light level sensor comprises: a substrate (11 ;21); - at least one photo electric detector (15;25) provided on said substrate and arranged for detecting light; a switched capacitor converter (16;26) provided on said substrate and arranged to convert a first signal from said photo electric detector to a second signal for accumulating energy in said energy accumulator.

2. The wireless sensor device (2) according to claim 1, wherein said substrate is a CMOS substrate (11) and said photo electric detector comprises a single photo diode (15) provided on said CMOS substrate.

3. The wireless sensor device (2) according to claim 1, further comprising an oscillator (18;28) configured for frequency control of said switched capacitor voltage converter (16;26) in dependence of said first signal.

4. The wireless sensor device (2) according to claim 1, further comprising a controller (14;24) configured for switching said wireless sensor device between a sensing mode and an energy accumulation mode.

5. The wireless sensor device (2) according to claim 4, wherein said controller (14;24) is configured for controlling switching between said sensing mode and said energy accumulation mode in dependence of said first signal.

6. The wireless sensor device (2) according to claim 1, wherein said substrate (21) comprises a plurality of photo electric detectors (25), e.g. photo diodes, said photo electric detectors being configured for detecting different wavelength ranges of said light.

7. The wireless sensor device (2) according to claim 1, further comprising a second sensor (13;23) and wherein said energy accumulator (12;22) is arranged for powering said second sensor.

8. The wireless sensor device (2) according to claim 1, wherein said second sensor (13;23) comprises an occupancy sensor, such as a pyroelectric infrared sensor.

9. The wireless sensor device (2) according to claim 1, further comprising a transmitter (17;27) for wirelessly transmitting sensing data to an external device (3), and wherein said energy accumulator is arranged for powering said transmitter.

10. An illumination system (1) comprising a plurality of light sources and at least one wireless sensor device (2) according to claim 1 for controlling one or more of said light sources of said illumination system in dependence on sensing data of said wireless sensor device.

11. The illumination system (1) according to claim 10, comprising a plurality of said wireless sensor devices (2), said wireless sensor devices being configured for transmitting sensing data at different times.

12. A method for operating a wireless sensor device (2), comprising a light level sensor (10;20) with a substrate (11;21) carrying at least one photo electric detector (15;25) and a switched capacitor converter (16;26), comprising the steps of: - detecting light at said photo electric detector to provide a first signal; converting said first signal to a second signal using said switched capacitor converter; accumulating energy in an energy accumulator (12;22) using said second signal; - providing power for said wireless sensor device using said energy in said energy accumulator.