WO1997032385A1

WO1997032385A1 - Charging and/or signal transmission system comprising a light source coacting with photovoltaic cells

Info

Publication number: WO1997032385A1
Application number: PCT/CH1997/000072
Authority: WO
Inventors: Jean Claude Berney
Original assignee: Njc Innovations
Priority date: 1996-03-01
Filing date: 1997-02-27
Publication date: 1997-09-04

Abstract

A system comprising a light source coacting with photovoltaic cells (5) in a device such as a hearing aid, an electronic watch or the like. In a first embodiment, the system comprises a housing (7, 8) such as a box in which the device is placed. The box has a cover containing the light source. When the cover is closed, the light source is located opposite the photovoltaic cells (5) and may be used to charge a power supply battery (2) of the device, or to transmit optical signals that may be taken into account in certain internal functions of the device.

Description

Patent application

Key charging system / or signal transmission comprising a light source collaborating with photovoltaic cells

There are at present many electronic applications requiring both a certain autonomy of operation and an increasing miniaturization, for example devices for the deaf, electronic watches, more particularly watches having special functions such as remote control, pager, certain medical applications, etc. As a result, the batteries are getting smaller and smaller while the energy requirements cannot be reduced in proportion. For example, devices for the deaf can now be housed directly inside the ear, but the power requirements for the amplifier and speaker remain the same, so you have to change the battery almost every week. In pager watches or other applications using very miniaturized RF receivers, the consumption of the input amplifier working in class A cannot be reduced beyond certain limits if we want to keep the necessary reception sensitivity . It is well known that in this type of watch, having to change the battery often represents a significant commercial handicap. Replacing the battery with an accumulator or a rechargeable battery, for example by means of photovoltaic cells, could present an interesting solution, provided that it is associated with an efficient charging system, not only from a technical point of view, but especially in terms of ease of implementation by the user. By photovoltaic cells we mean of course all cells capable of transforming light energy into electrical energy.

ec a suitable yield. In classic type quartz watches, the problem is less since the batteries have a much longer lifespan. However, there is currently a tendency to replace conventional batteries with photovoltaic cells charging a buffer element capable of ensuring the watch a certain operating autonomy. However it is well known that some people do not expose their watches to light enough, and are even likely to put it for several days, even several months in a dark place, wardrobe, chest or other, which can cause pure and simple stopping of the watch. This is a definite handicap, and here again the use of an efficient and user-friendly charging system would eliminate this drawback.

On another level, the applications mentioned above are increasingly using sophisticated means to increase their performance. For example, in devices for the deaf, means of remote control of the various functions are used, in particular electro-optical means of signal transmission. There is therefore a certain analogy in the components and subsystems which can be used both in the charging system recommended above and in these means of signal transmission. By pooling all or part of these components and subsystems, significant advantages are added which could increase the interest of the entire system.

The present invention specifically relates to a system for charging and / or transmitting signals comprising a light source collaborating with photovoltaic cells of the application, characterized in that it comprises> nun ens of positioning agencies of way u place said light source near said cells and directing at least a significant part of the light rays delivered by said light source onto said cells when said positioning means are put in place.

Figure 1 shows schematically by way of example the charging system according to the invention suitable for a device for the deaf.

FIG. 2 shows by way of example the charging system according to the invention suitable for a watch, this system being arranged so as to also allow the transmission of signals.

FIG. 3 shows by way of example a circuit directly using the photovoltaic cells as a means of receiving these signals.

FIG. 4 shows by way of example means for transmitting signals separate from the charging means proper applied to a device for the deaf.

Figure 1 shows schematically by way of example the charging system according to the invention suitable for a device for the deaf. In this device 1 having a shape allowing it to be housed directly inside the ear, the battery is replaced by an accumulator 2. In fact, the use of an accumulator in place of the battery can offer great advantages, especially the elimination of the weekly battery change. However, if this kind of solution is not currently applied to devices for the deaf or to other similar applications, it is because the whole problem lies in the implementation of the battery charge tern. Indeed, although steady progress is being made in this field, the capacity of accumulators remains approximately 4 times lower than that of batteries for an equivalent volume. This amounts to saying that for an autonomy of 8 days on battery, or 192 hours, there would remain 48 hours on accumulator. We must therefore promote a charging system that naturally encourages the user to recharge his device every day.

This is the object of the charging system according to the present invention. Firstly, the accumulator 2, making it possible to supply the electronic circuit of the application 3, is recharged through a diode 4 by 4 photovoltaic cells 5. These cells are composed for example of layers of polycrystalline NIP silicon deposited on a glass 6 fixed on the part of the device 1 facing outwards. The use of photovoltaic cells makes it possible to produce a contactless charging system, but it is certain that natural light is completely insufficient to ensure the recharging of the battery and that a charging system must be implemented. individual ad hoc which, as we said above, naturally encourages the user to use it every day. However it is a fact that the users of devices for deaf people do not use their device when they sleep As it is an element of a certain price, they will preferably place it in a case or fitting ad hoc to protected from shocks and dust. The originality of the invention consists precisely in making a case or fitting which, in addition to its primary function, allows the recharging of the accumulator 2. In our example this case is composed of a base 7 and a hinged cover 8. The base 7 comprises a recess having a shape adapted to the device 1, recess in which the user can place the latter, the photovoltaic cells 5 being turned outwards. The case includes a light source 9 connected by an external cable to a power supply 10. with a possible option for a low voltage socket (razor socket). When the cover S. is folded down, the latter covers the entire the surface except an opening 11 allowing the light source 9 to pass through and an opening 12 giving access to the cells 5. The entire internal surface 13 of the chamber thus formed is arranged so as to reflect the light in the manner of a mirror . By this particular arrangement, most of the light emitted by the light source 9 which would not be directly absorbed by the cells 5 is reflected on the walls until it reaches said cells in the manner of the spheres d 'Ulbricht. There is thus a high efficiency which makes it possible to use light sources of low power (of the order of a few Watts) and to limit heating. Note that the base and the cover of the case will be made at least partially with materials good heat conductors to evacuate it to the outside.

Thus for a light source of 1 Watt having a light output of 25%, a reflection chamber having a yield of 60% and cells having a yield of 5%, there is an overall yield of 0.75%, i.e. 7 , 5 mW of useful power per Watt. It may seem weak, but it is sufficient for this kind of application. Note that a 1 Watt light source used 8 hours a day consumes about 0.25 kWh per month, which represents a few cents, against several francs for the purchase of batteries.

FIG. 2 shows by way of example the charging system according to the invention suitable for a watch, this system being arranged so as to also allow the transmission of signals. There are obviously certain types of watches such as pager watches which consume relatively a lot of energy and whose batteries must be changed frequently, which are similar to the case described in FIG. However we have chosen to illustrate in this figure 2 the case of a simple quartz watch having only functions hours, hours, minutes, seconds, date, month, etc. This type of watch consumes only currents of the order of the microampere whereas the deaf device described in FIG. 1 consumes currents of the order of milliampere. Thus an accumulator of a few mAh is capable of ensuring a running autonomy of several months.

However, we are faced with a problem of energy balance. When worn, the watch can be hidden by clothing. In addition, there is no guarantee that it will be worn every day. Thus, even if the starting autonomy is several months, one can have a regular loss of this power reserve which ultimately results in the stopping of the watch. The regular use of a charging system therefore retains its meaning, provided that this system naturally encourages the user to use it, as we said above. In the case of the device for deaf or other similar applications there is a relatively imperative incentive insofar as, if ia recharging is not carried out punctually, the device stops working. In the watch it is not the same, and it is necessary to find other motivations to encourage the user to use his charging system as often as possible. This is possible by adding additional functions as we will describe below.

In FIG. 2, the charging system according to the invention comprises a box formed by a base 20 and a cover 21. The base 20 comprises a housing for placing the watch 22. When the cover 21 is folded down, the dial of watch 23 faces an opening 24 of the reflection chamber 25 described in FIG. Note that if the photovoltaic cells occupy only part of the surface of the dial, one can add a reflective cover on the opening 24. cover which lets the light rays pass only on said cells. The using a charging system such as that which is the subject of the present invention makes the cell surface less critical and it is possible, for example, to use ring cells placed outside the dial so as to leave the center of this one free for inscriptions or decorations. In the case described, the light source has been replaced by a simple power LED 26. Indeed, since the energy requirements of a watch are much lower than those of a deaf device, the use of a LED of a few hundred milliwatts is sufficient. Furthermore, this type of light source has the advantage of being able to be switched quickly and of being able to be used for the generation of light signals, as we will see below. The use of an incandescent light source for charging and a separate LED for signal transmission is also possible without problems.

First of all we will describe very schematically but sufficient for understanding some interesting auxiliary functions. Firstly, there is no need to leave the light source 26 permanently on. For this, the base 20 is equipped with a switch 27 mounted on a fairly hard spring which closes when the watch 22 is placed in its housing and the latter is held in place by the cover. Closing this switch 27 is therefore a prerequisite for turning on the LED 26. Secondly, it is not necessary to charge the accumulator for more than ten hours. After this delay, it is preferable either to interrupt the charge or to limit it to a maintenance value of the order of one tenth of the normal charge. The switch 27 is therefore connected to a timing circuit 28 connected to an LHD control circuit 29 so as to manage these charging times. Whatever the interest of these two functions. these are internal functions that do not go particularly encourage the owner of the watch to use their charging system more regularly. On the other hand, we can find complementary functions which clearly reinforce this motivation.

It is well known that the dream of any watchmaker is to create a watch that always stays perfectly on time. So there have been many proposals for several years ranging from remote control on the electricity network, cable television and hourly distribution by radio beam. The latter possibility is quite concrete since there have been radio controlled watches and clocks on the market for some time. However, this imposes a number of very restrictive constraints on the watch. For example, it is not possible to put the antenna inside a metal case which represents a magnetic short circuit. It is therefore necessary either to limit oneself to a plastic case, or to put the antenna outside, which is very limiting from an aesthetic point of view. Furthermore, due to the small volume of this antenna, the reception sensitivity is not optimal and there may be problems inside buildings. These constraints do not of course exist at the level of the clock where there is much more energy and space.

The solution proposed in Figure 2 is to integrate a clock controlled by radio or any other system that can serve as a time reference inside our box. This clock can be used for example as an alarm clock, which will encourage the user to place his box in his bedroom. As the latter generally does not need his watch when he sleeps, he will naturally have the gesture of placing it in the box which is within his reach. In addition,

in * electronic devices currently known, such as watchmaking microprocessors>. allow to incorporate in the watch a time reset function controlled from outside by ad hoc control signals. This time reset function can range from simple resetting of the second hand for classic analog watches to full time reset including the date and month for digital watches or analog watches multifunction with several motors. We will not describe in detail these time setting functions which are already used in the RF watches mentioned above, but show how one can use the charging system according to the invention to transmit the signals necessary for the watch. It goes without saying that the introduction of such a function in the charging case of the watch creates an important additional motivation to encourage the user to use it as often as possible. We can then assimilate this charging box to the famous sympathetic clocks which are one of the most prestigious jewels of traditional watchmaking.

The clock controlled by radio is represented schematically by the circuit 30 which controls the display 31. This circuit 30 transmits the time information necessary to the control circuit of the LED 29. This control circuit is arranged to die in form this information in the form serial signals and transmit them to the watch via LED 26, either on request or automatically every 10 minutes for example. There are numerous procedures for transmission by electro¬ optical means which may be suitable for this application. That which is described in the following figure relates to means making it possible to directly use the photovoltaic cells combined with simple reception means arranged so as to deliver all-or-nothing signals directly usable by the logic circuit for processing these signals. It goes without saying that we can use this signal transmission tern to transmit all other information useful to the watch or to the user, for example for watches having special functions such as electronic organizer, pager, etc.

FIG. 3 shows by way of example a circuit directly using the photovoltaic cells as a means of receiving the signals. In this figure we find ies four photovoltaic cells 40 and the rectifying diode 41 making it possible to charge the accumulator 42 through the resistor 43, connected between base and emitter of the transistor 44. This resistor 43 is chosen so that the fall of voltage across its terminals is less than the conduction voltage of the emitter / base diode of this transistor 44 as long as the current supplied by the photovoltaic cells is less than 100 μA, for example. Thus, up to this limit, this transistor 44 is not conductive and all the current supplied by the cells 40 is used to recharge the accumulator 42. When the current supplied by the cells 40 becomes greater than the fixed 100 μA, the transistor 44 becomes conductive. Its collector current is limited to 10 μA by the resistor 45, after which the transistor 44 saturates. The majority of the additional current supplied by the cells 40 then passes through the base of the transistor 44 through the resistor 46. This resistor 46 serves to limit the charging current. In fact, the voltage across the cells 40 is logarithmic, and cannot exceed about 0.8 volts per cell, even in the case of strong lighting. Resistor 46 is therefore chosen so as to limit the current to approximately one tenth of the capacity of accumulator 42, ie 1 mA for a capacity of 10 mAh. The transistor 44 acts practically as an all or nothing amplifier and delivers on its collector a signal 0 when the cells 40 deliver less than 100 μA, and a signal I when they deliver a current of more than 1 10 μΛ. This signal can be used directly by the logic processing circuit 47. without an intermediate amplifier. he

To be able to use these all-or-nothing signals generated directly at the terminals of the photovoltaic cells, two important conditions must be observed. First, given that this type of cell has a relatively slow reaction time, the frequency of these signals is limited in the current state of the art to a few hundred hertz, which is sufficient to transmit simple commands and instructions. . For example, the transmission of hour, minute, second, month and date time information comprises 10 4-bit digits, or 40 bits, which only takes a fraction of a second at 100 Hz. Second, state 0 corresponds to very weak illumination. U must therefore be sheltered from ambient lighting which is superimposed on the lighting provided by LED 26 and can therefore drown out the signals supplied by it. This condition is met in the charging system according to the invention since the application, device for the deaf, watch or the like is covered with a protective cover. Thus, there is a very simple signal transmission system to implement, provided that the above rules are observed.

The transmission of binary information can be done very simply by interrupting the light beam generated by the LED 26. States 0 and 1 can be represented for example by the relationships between the times of establishment and interruption of said light beam, as represented under points 48 and 49.

FIG. 4 shows by way of example means for transmitting signals separate from the charging means proper applied to a device for the deaf. In that case. the means of signal transmission must be independent of the charging means since the user may need to remote control your device at any time. In FIG. 4, the device for the deaf 50 is shown diagrammatically placed in the ear of the user 51. The latter has a remote control of small dimensions 52 which can easily be stored in a shirt pocket and be manipulated 'one hand. This remote control is therefore presented as a miniature telephone. It includes for example four control keys 53, 54, 55 and 56 for increasing and reducing the volume, increasing the treble or increasing the bass. This remote control is characterized by the fact that it must be placed directly on the deaf device. For this purpose the remote control comprises a relatively flexible part 57 adapted to the ear. The LED 58 necessary for the transmission of the signals is placed inside the part 57 which thus forms an open space on one side. The walls of this chamber are preferably bright metallized so as to reflect the light rays generated by the LED. Thus, when the user places his remote control on his device, we find ourselves in the same conditions as in FIGS. 1 and 2. The part 57 forms a cover and prevents ambient light from reaching the photovoltaic cells. Only the signals emitted by the LED 58 reach these cells and will be amplified as described in Figure 3. This way of doing things may be a little more restrictive than with the usual remote controls, but there is a clear simplification at the level of the internal electronics of the device, hence saving, especially if it can be combined with an efficient charging system.

The few examples which we have described seem to us sufficient for understanding the object of the invention. There are of course many other possible combinations but their description would not really bring new determining factors.

Claims

/ Charging and / or signal transmission system comprising at least one light source collaborating with photovoltaic cells of the application concerned, characterized in that it comprises positioning means arranged so as to place said light source at proximity of said cells and directing at least a significant part of the light rays delivered by said light source onto said cells when said positioning means are put in place.

/ System according to claim 1, characterized in that said positioning means are arranged so as to protect said cells from ambient light.

/ System according to claim 1 characterized in that the said positioning means consist of an installation with cover, said installation comprising at least one location for placing the application concerned, and the cover comprising at least means for directing the light rays delivered by the light source on the photovoltaic cells of the application.

/ System according to claim 1 characterized in that said means for directing a significant part of the light rays delivered by the light source on the photovoltaic cells comprise a reflection chamber having an opening on said cells, and whose walls are reflective like mirrors. 5 / System according to claim 1 characterized in that said light source is arranged so as to charge an accumulator through said photovoltaic cells.

6 / System according to claim 1 characterized in that said light source can be modulated all or nothing so as to transmit optical signals to said application.

System according to claims 1 and 6 characterized in that it comprises at least one additional electronic function which at least indirectly delivers the information to be transmitted to the application.

8 / System according to claims 1, 6 and 7 characterized in that said additional electronic function is a time function arranged so as to allow the time setting of a watch.

9 / System according to claims 1, 6 and 7 characterized in that said additional electronic function is arranged so as to allow to adjust the parameters of a device for the deaf.

10 / System according to claims l and 5 characterized in that it comprises a timing circuit for controlling said light source, circuit arranged to manage the time and the charging mode of the accumulator.