WO2018065077A1

WO2018065077A1 - A charging device and a method of charging a charge storage device

Info

Publication number: WO2018065077A1
Application number: PCT/EP2016/082365
Authority: WO
Inventors: Wouter Cornelis OTTE
Original assignee: VERACHTERT, Nicolaas, Geertruda
Priority date: 2016-10-04
Filing date: 2016-12-22
Publication date: 2018-04-12
Also published as: ZA201902792B

Abstract

A charging device (100) comprises an antenna interface (20) adapted for receiving multiple electromagnetic signals at different radio frequencies, rectifiers (30) for simultaneously rectifying the received multiple electromagnetic signals into corresponding rectified signals having rectified voltages and rectified currents, respectively, each rectifier having a rectifier input (50) for electrically coupling to an output of the antenna interface (20) for receiving one of the multiple electromagnetic signals at one radio frequency and a rectifier output (60) for outputting the corresponding rectified signal, switching circuit (70) configured for electrically coupling a rectifier output to at least another rectifier output, selectively in series or in parallel, for adding at least two rectified signals and selectively supplying the added rectified signals to the charge storage device (90), a control circuit (80) configured for controlling the switching circuit for controlling the supplied rectified signals based on the rectified voltages.

Description

A CHARGING DEVICE AND A METHOD OF CHARGING A CHARGE STORAGE DEVICE

FIELD OF THE INVENTION

The invention relates to a charging device for charging a charge storage device, a charging device system and a method of charging the charge storage device.

BACKGROUND

Wireless chargers are practical devices for charging devices that store charges. Wireless chargers do not use cables to connect the device to be charged to the power source so that a user of the wireless charger can place the device to be charged near the wireless charger without plugging any socket therein.

A known example of such wireless charger is given in in US patent 6127799. A charging system for wirelessly charging a charge storage device is disclosed. The charge storage device is placed in a Radio frequency or microwave electromagnetic field. One or more antennas receiving the Radio Frequency electromagnetic field are placed on the charge storage device. Rectifiers are connected to the antennas for rectifying the received RF electromagnetic field and produce a DC output current which is used to charge the charge storage device.

However, the inventor found devices such as described in the above patent to have severe limitations. The known charging system works solely when the RF or microwave radiation field is known to the user of the charging system. In other words, the charge storage device of the known device is placed, via a support surface, in a specific RF electromagnetic field generated by a specific RF power source (e.g. a magnetron). By knowing the radiation field, radiated frequency components of the radiation field are also known. Thereupon, choices on the type of antenna to be used and on the relative antenna orientation can be made for optimizing conversion of the RF electromagnetic field into DC output current for charging the charge storage device.

Unfortunately, a specific RF power source may or may not be available or appropriate when charging a charge storage device on the move, while for example travelling. In particular, the known charging system fails to work in cases where the user wishes to charge the charge storage device independently on a specific RF source, and/or on the placement of the charge storage device relative to said specific RF source.

SUMMARY OF THE INVENTION

It would be advantageous to have an improved charging device. The inventor had the insight that multiple RF signals which are normally present in the electromagnetic spectrum radiated into the free space, can be simultaneously used for charging a charge storage device. A charging device is provided that uses multiple RF signals at different radio frequencies. The charging device comprises an antenna interface adapted for receiving the multiple electromagnetic signals at different radio frequencies, rectifiers for simultaneously rectifying the received multiple electromagnetic signals into corresponding rectified signals having rectified voltages and rectified currents, respectively. Each rectifier has a rectifier input for electrically coupling to an output of the antenna interface and receiving one of the multiple electromagnetic signals at one radio frequency and a rectifier output for outputting the corresponding rectified signal. The charging device further comprises a switching circuit configured for electrically coupling a rectifier output to at least another rectifier output, selectively in series or in parallel, for adding at least two rectified signals and selectively supplying the added rectified signals to the charge storage device, and a control circuit configured for controlling the switching circuit for controlling the supplied rectified signals based on the rectified voltages.

For example, electromagnetic signals of electromagnetic field radiated into the free space such as those transmitted with wireless appliances of common use as with Wifi, GSM, UMTS, LTE, or 802.1 1 appliances can be received by the antenna interface. Rectifiers rectify said different electromagnetic signals into corresponding rectified signals comprising rectified voltages and rectified currents, respectively. The switching circuit, controlled by the control circuit, adds the rectified signals based on the rectified voltages for supplying the added rectified signal to the charge storage device. By controlling the added rectified signal based on the rectified voltages, power for charging the charge storage device can be optimized. For example, rectified voltages can be added such that the charge storage device can be charged with a desired rectified voltage. Rectified currents can be added to increase a total rectified current such that charging power determined by the desired rectified voltage and total rectified current is increased. The charge storage device can be charged faster and more efficiently.

Embodiments provide different functional arrangements of the rectified voltages in series and/or in parallel for optimizing charging of the charge storage device.

In an embodiment, the rectified voltages are added with the condition that the added rectified voltages are equal or higher than a threshold voltage for obtaining an overvoltage value. Prior to starting charging the charge storage device, for example Lithium batteries, an overvoltage is supplied. In this way the charge storage device can be charged with a rectified voltage equal or higher than the threshold voltage, i.e. with an overvoltage. The overvoltage may be specific for the particular charge storage device. The overvoltage may be selected as the smallest voltage with which the charge storage device will charge.

In an embodiment, the control circuit is configured for selecting a first set and a second set of one or more rectifiers, and for controlling the switching circuit for electrically coupling the rectifier outputs of the first set in series, electrically coupling the rectifiers outputs of the second set in parallel, electrically coupling the coupled rectifier outputs of the first set to the coupled rectifier outputs of the second set in series. The first set is selected so that the rectified voltage of the coupled rectifier outputs in series is equal or higher than threshold voltage for obtaining an overvoltage value. Charging can occur at an overvoltage value and at the same time the total rectified current can be increased by electrically coupling the rectifier outputs of the second set in parallel. Charging at an overvoltage is performed more efficiently.

A method of charging a charge storage device may be implemented on a computer as a computer implemented method, or in dedicated hardware, or in a combination of both. Executable code for a method according to the invention may be stored on a computer program product. Examples of computer program products include memory devices, optical storage devices, integrated circuits, servers, online software, etc. Preferably, the computer program product comprises non-transitory program code stored on a computer readable medium for performing a method according to the invention when said program product is executed on a computer.

In a preferred embodiment, the computer program comprises computer program code adapted to perform all the steps of a method according to the invention when the computer program is run on a computer. Preferably, the computer program is embodied on a computer readable medium.

BRIEF DESCRIPTION OF THE DRAWINGS

Further details, aspects and embodiments of the invention will be described, by way of example only, with reference to the drawings. Elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. In the Figures, elements which correspond to elements already described may have the same reference numerals. In the drawings,

Figure 1 schematically shows an example of an embodiment of a charging device, Figure 2a schematically shows a functional embodiment of a switching circuit,

Figure 2b schematically shows a functional embodiment of a switching circuit, Figure 2c schematically shows the schematic diagram for the functional embodiment of Figure 2a,

Figure 2d schematically shows the schematic diagram for the functional embodiment of Figure 2b,

Figure 3 schematically shows a flow diagram describing various embodiments of a charging method,

Figure 4a schematically shows an example of an embodiment of antenna interface, Figure 4b schematically shows an example of an embodiment of antenna interface, Figure 5 schematically shows an embodiment of a rectifier,

Figure 6 schematically shows a circuit diagram of an embodiment of a charging system ,

Figure 7 schematically shows a signal waveform measured with an embodiment of a charging device,

Figure 8 schematically shows a flow diagram for a method of charging a charge storage device. List of Reference Numerals in Figures 1 , 2a, 2b, 2c, 2d, 4a, 4c 5 and 6:

10-14, 16 a receiving antenna

15 a matching circuit

20-22 an antenna interface

30 rectifiers

31-34 a rectifier

35 a Tesla air circuit

36 a transistor

37 a capacitor

38 a Joule thief circuit

39 a resistor

41 a transformer

50 a rectifier input

55 a diode

57 a capacitor

60 a rectifier output

70 a switching circuit

80, 81 a control circuit

85 a voltage measurement circuit

86 a current measurement circuit

90 a charge storage device

95, 97 a battery

100 a charging device

600 a charging system

900 a measured waveform

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

While this invention is susceptible of embodiment in many different forms, there are shown in the drawings and will herein be described in detail one or more specific embodiments, with the understanding that the present disclosure is to be considered as exemplary of the principles of the invention and not intended to limit the invention to the specific embodiments shown and described.

In the following, for the sake of understanding, elements of embodiments are described in operation. However, it will be apparent that the respective elements are arranged to perform the functions being described as performed by them. Further, the invention is not limited to the embodiments, and the invention lies in each and every novel feature or combination of features described herein or recited in mutually different dependent claims.

Figure 1 schematically shows an example of an embodiment of a charging device 100.

The charging device 100 is for charging a charge storage device 90 by an electromagnetic field radiated into the free space.

Such an electromagnetic field comprises a variety of electromagnetic signals which are generated by various sources in the free space. The electromagnetic field comprises multiple electromagnetic signals at different radio frequencies.

The electromagnetic field is radiated into the free space by commonly used appliances which include but are not limited to FM radios, wireless devices based on various communication technologies such as Wifi, GSM, UMTS, LTE, 802.1 1 , smart sensors based on Bluetooth or other wireless communication protocols, or the like. Each appliance generates an electromagnetic signal having different radio frequency components of another electromagnetic signal generated by another appliance.

In this document, a radio frequency (RF) electromagnetic signal is any signal containing frequency components suitable for transmitting energy into the free space. Such radio frequency signal thus comprises but is not limited to frequency components in the range of 9KHz to 300 GHz, for example the radio frequency or microwave frequency spectrum. For example, the frequency components of GSM technology are in the range of 870 Megahertz to 920 Megahertz, frequency components of DCS (Digital Cellular System) band are in the range of 1710 to 1790 Megahertz, and likewise Wifi can operate at different frequency ranges centered approximatively at 2.4 GHz or 5 GHz.

The environment in which there is any kind of human activity has seen an increase of wireless devices which enable or improve communications between persons, and between electronic devices. The inventor has realized that the electromagnetic field radiated in the free space is usable for charging a charge storage device.

The charge storage device 90 may be any suitable charge storage device suitable for the specific implementation. For example, the charge storage device 90 may be a battery or a capacitor which may be relatively large to store electric charges for some time. The battery or capacitor may be that of a portable device, for example a mobile phone, a tracking device, a sensor device or any device which consumes relatively low power and can be powered by portable batteries.

The charging device 100 has an antenna interface 20 which is adapted for receiving these multiple electromagnetic signals at different radio frequencies.

An antenna interface 20 may in particular comprise multiple receiving antennas, each adapted to receive an electromagnetic signal at one specific radio frequency or within a selected frequency band, as further described in an embodiment below. In an alternative embodiment further described below, the antenna interface 20 may comprise a single receiving antenna electrically coupled to a matching circuit for matching the single antenna at the multiple radio frequencies.

The charging device 100 comprises rectifiers 30 for simultaneously rectifying the received multiple electromagnetic signals into corresponding rectified signals. Each rectified signal has a rectified voltage and a rectified current. Each rectifier 31-34 has a rectifier input 50 and a rectifier output 60. The rectifier input 50 is for electrically coupling to an output of the antenna interface 20 and receiving one of the multiple electromagnetic signals at one radio frequency. The rectifier output 60 is for outputting the corresponding rectified signal.

The charging device 100 comprises a switching circuit 70 configured for electrically coupling a rectifier output 60 to at least another rectifier output, selectively in series or in parallel, for adding at least two rectified signals and selectively supplying the added rectified signals to the charge storage device 90.

The charging device 100 comprises a control circuit 80 configured for controlling the switching circuit 70 for controlling the supplied rectified signals based on the rectified voltages.

Control circuit 80 may be configured to generate switching signals for controlling switches in switching control circuit 70 associated to each rectifier output of rectifiers 30. Such switching signals may control switches for electrically coupling the rectifier outputs between each other and adding at least two rectified signals.

The control circuit 80 may be configured for controlling the switching circuit 70 such that the switching circuits 70 adds one or more rectified voltages in series.

The control circuit 80 may be configured for controlling the switching circuit 70 such that the switching circuits 70 adds one or more rectified currents in parallel.

Control circuit 80 may comprise e.g. a microprocessor which can be programmed according to one or more embodiment described below.

Charge storage device 90 may be charged independently from the presence or absence of a specific electromagnetic signal at a specific frequency, because multiple electromagnetic signals may be added in series or parallel in order to provide sufficient charge power to the charge storage device 90. Since the antenna interface 20 may be adapted to receive multiple electromagnetic signals at different radio frequency, the charging device 100 may harvest energy from multiple RF power sources, some of them being further way than others. There is thus a higher probability that charging of the charge storage device 90 does not depend upon on the location of the charging device 100 relative to the RF power sources.

To explain further, Figure 2a shows a possible functional embodiment of the switching circuit 70.

Each rectifier 31-34 can act as a voltage source producing rectified voltages V1-V4 and corresponding rectified currents 11-14.

Switching circuit 70 may be implemented in any manner suitable for the specific implementation. For example, switching circuit 70 may comprise multiple switches, multiplexer-like capable of electrically connecting the rectified voltages V1-V4 in series or in parallel.

Such switches may be implemented with any suitable semiconductor technology or semiconductor switches. For example, Metal Oxide Semiconductor (MOS) switches or bipolar (NPN or PNP) switches or diode switches may be implemented.

In an embodiment as shown in Figure 2a, each rectifier output comprises a first output terminal and a second output terminal for outputting the rectified voltage V1 , V2, V3 or V4 across the first output terminal and the second output terminal. The first output terminal or second output terminal of each rectifier 31 , 32, 33, or 34 may output the rectified current 11 , I2, I3 or I4.

In Figure 2a, a control circuit 81 is configured to control the switching circuit 70 such that, based on the rectified voltages, the respective rectified voltages V1-V4 are added, for example in series. The added voltages V1-V4 are supplied to the charge storage device 90.

In order to charge the charge storage device 90, for example a battery, sufficient rectified voltage may be required prior to starting charging.

In an embodiment, the rectified voltages V1-V4 are added with the condition that the added rectified voltages are equal or higher than a threshold voltage such that an overvoltage value is obtained. The overvoltage value is applied across the charge storage device 90.

The charging device aims to charge storage device 90 at a voltage of at least a threshold voltage, such a voltage is termed an overvoltage.

For example, the overvoltage may be selected as the smallest voltage with which the charge storage device 90 will charge.

When the voltage applied to the charge storage device 90 is equal or higher than the threshold voltage, the charge storage device 90 can start to be charged.

In an embodiment, the overvoltage is at least 5% higher than a nominal voltage of the charge storage device 90.

For example, batteries with a lithium iron phosphate positive electrode and graphite negative electrode have a nominal open-circuit voltage of 3.2 V and a typical charging voltage of 3.6 V. Battery with lithium nickel manganese cobalt (NMC) oxide positive electrode and with a graphite negative electrode have a 3.7 V nominal voltage while they can be charged at 4.2 V.

The charging device aims to charge batteries of smaller capacity than batteries used to power, for example, mobile phones. As described in a later embodiment, one of such smaller capacity battery may be a 0.5 V or lower battery. In such a case the overvoltage is also correspondingly lower, e.g. 55m V or lower.

Charging of the charge storage device 90 may be effected at an overvoltage and the overvoltage may be applied while the current drops to a predetermined threshold. Charging may be terminated when the current drops 3% of the initial charge current. In an embodiment, the control circuit 81 is configured to control the switching circuit 70 such the added rectified voltages are supplied to the charge storage device 90 until the rectified current supplied to the charged storage device 90 is equal or higher than a selected current threshold, for example equal or lower than 3% of an initial rectified supplied current.

The charging device 100 is configured to supply to the charge storage device 90, a direct current (DC) rectified voltage, equal or higher than a threshold, for obtaining an overvoltage and to supply the rectified current corresponding to that overvoltage value while the rectified current is equal or higher than a selected current threshold.

In an embodiment, the control circuit 81 may comprise a voltage measuring circuit 85 for measuring the rectified voltages V1-V4.

In an embodiment, the voltage measuring circuit 85 may measure the rectified voltages and determine whether the added rectified voltage is equal or lower than the overvoltage value.

In an embodiment, the voltage measuring circuit 85 may be configured to measure directly the added rectified voltages and determine whether the added rectified voltage is equal or lower than the overvoltage value. The control circuit 81 , based on the measured rectified voltages or added rectified voltages, may be configured to control the switching circuit 70 such that one or more rectified voltages V1-V4 are added in series. In the example shown in Figure 2a, all available rectified voltages V1-V4 are added in series, meaning that an overvoltage value can be obtained by adding the respective rectified voltages V1 , V2, V3 and V4 in series.

In an embodiment, the control circuit 81 may comprise a current measuring circuit 86 for measuring the rectified current corresponding to the supplied added rectified signals.

In an embodiment, the current measuring circuit 86 may be configured to measure the rectified current corresponding to the supplied rectified voltage and determine whether the rectified current is equal or higher than a current threshold.

In an embodiment, the control circuit 81 may be configured to control the switching circuit 70 such that the overvoltage value is supplied to the charge storage device until the measured rectified current is equal or higher than the current threshold.

For example, in the embodiment shown in Figure 2a, the control circuit 81 may be configured to supply the voltage equal to the series of voltages V1 , V2, V3 and V4 until the series current is higher than a predetermined threshold. When the series current drops below the current threshold, the control circuit 81 may be configured to control the switching circuit 70 for electrically decoupling the switching circuit 70 from the charge storage device 90.

Figure 2b schematically shows an embodiment of switching circuit 70. Embodiment of Figure 2b differs from embodiment of Figure 2a in that control circuit 81 controls the switching circuit 70 such the rectifier outputs are differently electrically connected to each other. Switching circuit 70 is controlled such that rectified voltages V1 and V2 are connected in series while rectified voltages V3 and V4 are connected in parallel. Rectified voltage V3 and V4 connected in parallel are connected in series to the voltages V1 and V2 connected in series.

In the embodiment of Figure 2b, an overvoltage value is obtained by electrically connecting rectified voltages V1 and V2 in series. Measuring circuit 86 may determine that rectified voltage V1 in series to rectified voltage V2 is equal or higher than the threshold voltage such that an overvoltage can be obtained and supplied to the charge storage device. However, rectified voltages V3 and V4 are available for increasing the charge current. Therefore, control circuit 81 controls the switching circuit 70 for arranging the rectified voltages V3 and V4 in parallel for adding up the rectified currents I3 and I4 of voltage sources V3 and V4, respectively. The resulting current is added to the equivalent current of the voltage sources V1 and V2 connected in series.

In the latter embodiment, charging power has been increased by increasing the total charging current. Charging of the charging storage device 90 may be performed faster or more efficiently.

In an embodiment, the control circuit 80 or 81 described with reference to the embodiments of Figure 1 and Figure 2a and Figure 2b, respectively, may be configured for selecting a first set and a second set of one or more rectifiers. In said embodiment, the control circuit may be configured to control the switching circuit for electrically coupling the rectifier outputs of the first set in series, electrically coupling the rectifier outputs of the second set in parallel, and electrically coupling the coupled rectifier outputs of the first set to the coupled rectifier outputs of the second set in series. The first set of rectifier outputs is selected so that the voltage of the coupled rectifier outputs in series is equal or higher than a threshold voltage for obtaining an overvoltage value.

Figure 2c schematically shows the schematic diagram for the functional embodiment of Figure 2a. Rectified voltages V1 , V2 V3 and V4 are arranged in series and the resulting series voltage which the sum of rectified voltages V1 , V2, V3 and V4 is supplied to the charge storage device. The resulting series voltage is an overvoltage value

Figure 2d schematically shows the schematic diagram for the functional embodiment of Figure 2b. Rectified voltages V1 and V2 are arranged in series. Rectified voltages V3 and V4 are arranged in parallel. The sum of rectified voltages V1 and V2 is an overvoltage. Series arranged rectified voltages V1 and V2 are arranged in series to parallel arranged rectified voltages V3 and V4. The resulting series voltage is the sum of rectified voltages V1 , V2 and equivalent rectified voltage of parallel arranged rectified voltages V3 and V4. The resulting series voltage is an increased overvoltage value. However, the increased overvoltage value is a smaller than a value that would be obtained if all rectified voltages V1 , V2, V3 and V4 were arranged in series. In this embodiment, it is preferred to increase the rectified current than increase further the overvoltage.

To explain further, Figure 3 schematically shows a flow diagram describing various embodiments of a charging method that may be used, e.g. in the charging device 100 of Figure 1.

In step 300 the electromagnetic field is received. The electromagnetic signals are received by multiple antennas assigned to a specific radio frequency of the signal.

In an embodiment, schematically described with step 310, control circuit 80 or 81 may determine whether all rectifier outputs are electrically connected in series or are electrically connected at all. In an embodiment, if all rectifier outputs are connected in series and the sum of all rectified voltages connected in series is higher than an overvoltage, then the battery can be charged with said overvoltage, see corresponding step 330.

In an embodiment, if some of rectifier outputs are not connected, control circuit may be configured to select a first set of rectifier outputs and a second set of rectifier outputs. In step 340, control circuit 80 or 81 may determine whether, for the rectifier outputs already electrically connected in series, the added rectified voltage is higher or lower than an overvoltage. If the added rectified voltage is higher than an overvoltage, at step 350, the rectifier outputs which are not connected yet, i.e. the rectifier outputs of the second set, will be electrically connected first in parallel between each other and then in series with the rectifier outputs of the first set. Battery can be charged with the resulting series/parallel/series arrangement at step 330.

In an embodiment, if it is not possible to select at least two sets of rectifier outputs of which one set can add up to an overvoltage, then if there is a rectifier output available, this is connected in series, see corresponding step 360. A check, see step 310, whether all rectifier outputs are electrically connected in series will start again.

Charging voltage drops when charging current drops, therefore charging voltage is monitored, e.g. by voltage measuring circuit 85.

In an embodiment, control circuit 80 or 81 , see corresponding step 370, controls that the rectified voltage supplied to the battery, remains higher than an overvoltage, otherwise, see corresponding step 380, the control circuit may determine whether there are or not, in the existing arrangement of rectifier outputs, rectifier outputs connected in parallel.

In an embodiment, if there are some rectifier outputs connected in parallel, the control circuit is configured to disconnect them, see corresponding step 390, and to connect one of the disconnected rectifier output in series with the existing rectifier output arrangement. The control circuit will again determine whether all rectifier outputs are electrically connected in series, see step 310, and whether or not an overvoltage value can be obtained with connecting all rectifier outputs, see step 320, or with some of the rectifier outputs, see step 340.

In an embodiment, if there are no other rectifier outputs connected in parallel which can be used to make an overvoltage, then there is no possibility to obtain an overvoltage value and all rectifier outputs are disconnected from the charge storage device, see step 400. The check can start all over again at step 300.

In an embodiment, the control circuit is configured for controlling the switching circuit for electrically connecting two overvoltage values in parallel if more than one overvoltage value is obtainable by adding the rectified voltages.

In an embodiment, if more than one rectified voltage remains unused for obtaining another overvoltage value, the control circuit is configured for controlling the switching circuit for electrically connecting the remaining rectified voltages in a parallel arrangement between each other for obtaining a first rectified current equal to the sum of the rectified currents corresponding to the respective remaining rectified voltages, and electrically connecting the parallel arrangement in series with the one or more existing overvoltage values. In an embodiment, if there is only one rectified voltage unused for obtaining an overvoltage, the control circuit may be configured to control the switching circuit for electrically connecting the unused rectified voltage in series with the one or more overvoltage values.

Figure 4a schematically shows an example of an embodiment of antenna interface 21. Antenna interface 21 comprises a single receiving antenna 10 and a matching circuit 15 having an input for electrically coupling to the receiving antenna and multiple outputs for electrically coupling to respective rectifier inputs 50.

The single receiving antenna 10 may be made of electrical conductors of desired electrical length.

The matching circuit 15 is configured for matching the receiving antenna 10 to the different radio frequencies.

For example, the matching circuit 15 may include filter circuitry, multiplexing circuitry, microstrip lines to adapt electrical length of the receiving antenna 10 to the desired radio frequency range. The matching circuit 15 and the antenna 10 may be partially or fully integrated in substrate layers made of dielectric material such single or multi-layer printed circuit boards (PCB).

Figure 4b schematically shows an example of an embodiment of antenna interface 22. Antenna interface 22 comprises multiple receiving antennas 1 1-14 for receiving the respective multiple electromagnetic signals. Each receiving antenna 1 1-14 is electrically coupled to respective rectifier inputs of rectifiers 31-34. Each receiving antenna 1 1-14 is adapted to receive in a specific frequency band corresponding to the respective electromagnetic signals.

As in the embodiment for the single antenna described above, receiving antennas may be made of electrical conductors of desired electrical length associated to the respective receiving radio frequency of the electromagnetic signals. The receiving antennas 1 1-14 may be fully or partially integrated on dielectric substrate or PCBs.

The electric field of an electromagnetic signal induces a small voltage in each small segment of the receiving antenna. The induced voltage depends on the electrical field and the conductor length. The voltage depends also on the relative orientation of the segment and the electrical field. Each small voltage induces a current and this current circulates through a small part of the antenna impedance.

The maximum power that an antenna can extract from the electromagnetic field radiated into the free space is determined by so-called Friis transmission Formula and linearly depends on a gain of the antenna and on the square of the wavelength of the electromagnetic field, and not on the antenna dimension. It is thus possible to maximize the gain of the receiving antenna at one specific radio frequency band for optimizing reception at that band, without too much compromising on the antenna dimensions.

For example, according to an earlier embodiment, gain of receiving antenna 1 1 may be optimized for receiving radio frequency of FM radio, i.e. in the radio frequency band typically between 65 MHz and 108 MHz, gain of receiving antenna 12 may be optimized for receiving electromagnetic signals emitted by Wifi routers in a first frequency band, i.e. typically in the frequency band between 2.4 and 2.5 GHz, gain of receiving antenna 13 may be optimized for receiving electromagnetic signals emitted by Wifi routers in a second frequency band, i.e. typically in the frequency band between 5.150 GHz and 5.750 GHz, and gain of receiving antenna 14 may be optimized for receiving electromagnetic signals emitted by mobile telephones in some of UMTS, PCS, DCS radio frequency band, i.e. between 1800 MHz and 2100 MHz.

Figure 5 schematically shows an embodiment of a rectifier 35. Rectifier 35 may have a rectifier input electrically coupled to an output of a receiving antenna 16. Rectifier 35 may be a so-called Tesla air circuit, for example the Tesla air circuit 35 of Figure 5. Tesla air circuit 35 has Tesla air input, a Tesla positive output terminal electrically coupled to a positive terminal of the charge storage device (not shown in Figure 5) via the switching circuit (not shown in Figure 5), and a Tesla negative terminal electrically coupled to a negative terminal of the charge storage device via the switching circuit.

Tesla air circuit of the example shown in Figure 5, includes four diodes 55 for rectifying both the positive and negative wave portions of the electromagnetic signal, two capacitors 57 having each a first capacitor terminal coupled to an anode of two of the diodes 55 and to a cathode of the other two diodes 55, respectively, and a common second capacitor terminal electrically coupled to the output of the receiving antenna 16. The diodes 55 are, in this example, Germanium diodes 1 N34. However, man other different types can be used, such 1 N4148, 1 N60, 1 270 diodes.

Figure 6 schematically shows a circuit diagram of an embodiment of a charging system 600. Charging system 600 comprises a Tesla air circuit 35 and a joule thief circuit 38. Tesla air circuit 35 is electrically coupled to a storage device 95, in this case battery 95. In Figure 6, the switching circuit is not shown: charging system 600 includes, as way of an example, only one rectifier, i.e. Tesla air circuit 35 having the Tesla output directly electrically coupled to the first charge storage device, i.e. battery 95.

Battery 95 may be a battery of small capacity, for example of 0.5 V which is charged by the charging device as explained in one or more of the above embodiments and can be used to supply the Joule thiefcircuit 38. The battery 95 is a support battery which can be charged with low power, for example in the mill watts (mW) range, received by the receiving antenna 16 and by other receiving antennas (not shown in Figure 6), converted by the Tesla air circuit 35 and other rectifiers (not shown in Figure 6) whose output is selectively switched in series and/or in parallel with the Tesla output. Joule thief circuit 38 comprises a transistor 36, for example of NPN type, for example type BC547 or 2N3904 or 2N2222, transformer 41 electrically coupled between an input and output of the transistor 36, a capacitor 37 connected between the base of the NPN transistor 36 and one terminal of a secondary winding of the transformer 41 , and a resistor electrically coupled between the base of the NPN transistor and another terminal of the secondary winding of the transformer 41. Transformer 41 may comprise a ferrite core and a primary to secondary winding turn ratio, for example in a range between 1 to 30 to 2 to 10.

Joule thief circuit 38 further includes a decoupling capacitor 42 which is electrically coupling to a voltage regulator, for example type LM317 for converting the rectified voltage of the battery 95 for charging a further charge storage device, e.g. in this example further battery 97. Further battery 97 may be a battery of greater capacity than battery 95, for example a 5 V battery.

In an embodiment, Joule thief circuit 38 is configured to transfer electrical power from the battery 95 to the further battery 97. Joule thief circuits are known in the art to be very efficient circuits for driving small loads. The circuit works by rapidly switching the transistor 36. Initially, current begins to flow through the resistor 39, secondary winding of transformer 41 , and base-emitter junction of transistor 36 which causes the transistor 36 to begin conducting collector current through the primary winding. Since the two windings are connected in opposing directions, this induces a voltage in the secondary winding which is positive (due to the winding polarity) which turns the transistor 36 on with higher bias. This self-stroking/positive-feedback process almost instantly turns the transistor on as hard as possible (putting it in the saturation region), making the collector-emitter path look like essentially a closed switch (since V_CE will be only about 0.1 volts, assuming that the base current is high enough). With the primary winding effectively across the battery 95, the current increases at a rate proportional to the supply voltage divided by the inductance.

An advantage of using the Joule thief circuit 38 is that transistor 36 dissipates very little energy, even at high oscillating frequencies, because it spends most of its time in the fully on or fully off state, so either voltage over or current through the transistor is zero, thus minimizing the switching losses. Efficient transfer of electric charge from the battery 95 to further battery 97 ensures low losses in the charging system 600 or charging device thereof, making charging overall more efficient.

In an embodiment, charging system 600 comprises the charging device 100 according to any of the embodiment described above, and the further battery 97 for powering a portable device. The further battery may be electrically coupled to the charge storage device 95 for charging the further battery 97, for example according to the specification of the further battery 97.

Receiving antenna 16, Tesla air circuit 35 and Joule thief circuit 38 together with the first battery 95 may be integrated in a single charging device, for example a battery bank or separated connected devices.

For example, the battery bank may be connectable via USB to the second battery.

Charging system 600 may be fully integrated in the portable device, such as a mobile phone for charging 24 hours a day the second battery 97.

Figure 7 schematically shows a signal waveform measured with an embodiment of a charging device. Figure 7 shows the signal waveform of two coupled FM antenna's at an input of a rectifier according to an embodiment of the invention. This voltage is measured with an oscilloscope. Horizontal axis indicates time and vertical axis indicates voltage. In the oscilloscope, a scale for the horizontal axis is set to 5ms per division and a scale for the vertical axis is set to 0.5 V per division. The measured waveform is an AC voltage of about 3V peak to peak. At the rectifier output, a corresponding rectified voltage (not shown in Figure 7) of approximately 1.9V is obtained.

Figure 8 schematically shows a flow diagram for a method 1000 of charging a charge storage device, for example a battery or a capacitor, by an electromagnetic field radiated into the free space. The electromagnetic field comprises multiple electromagnetic signals at different radio frequencies.

The method comprises receiving 1010 the multiple electromagnetic signals at different radio frequencies, rectifying 1020 the received multiple electromagnetic signals into corresponding rectified signals having rectified voltages and rectified currents, adding 1030 at least two rectified signals, selectively in series or in parallel, for selectively supplying the added rectified signals to the charge storage device, and controlling 1040 the supplied rectified signals based on the rectified voltages.

Adding 1040 may further comprise adding 1050 one or more rectified voltages and/or adding one or more rectified currents, wherein, for example, the voltages are added such the added rectified voltages are equal or higher than a threshold voltage for obtaining an overvoltage value.

Controlling 1040 may further comprise selecting 1070 a first set and a second set of one or more rectified voltages, and electrically coupling 1080 the rectified voltages of the first set in series, electrically coupling 1090 the rectified voltages of the second set in parallel, electrically coupling 1 100 the coupled rectified voltages of the first set to the coupled rectified voltages of the second set in series, where the first set is selected so that the equivalent rectified voltage of the coupled rectified voltages in series is equal or higher than an overvoltage value.

Typically, the control circuits 80, 81 comprise a microprocessor (not shown) which executes appropriate software stored therein; for example, that software may have been downloaded and/or stored in a corresponding memory, e.g., a volatile memory such as RAM or a non-volatile memory such as Flash (not shown). The switching circuit 70 may also be equipped with microprocessors and memories (not shown). Alternatively, the control circuits 80, 81 may, in whole or in part, be implemented in programmable logic, e.g., as field-programmable gate array (FPGA). Control circuits 80, 81 may be implemented, in whole or in part, as a so- called application-specific integrated circuit (ASIC), i.e. an integrated circuit (IC) customized for their particular use.

Many different ways of executing the method are possible, as will be apparent to a person skilled in the art. For example, the order of the steps can be varied or some steps may be executed in parallel. Moreover, in between steps other method steps may be inserted. The inserted steps may represent refinements of the method such as described herein, or may be unrelated to the method. For example, steps 1030and 1040 may be executed, at least partially, in parallel. Moreover, a given step may not have finished completely before a next step is started.

A method according to the invention may be executed using software, which comprises instructions for causing a processor system to perform method 1000. Software may only include those steps taken by a particular sub-entity of the system. The software may be stored in a suitable storage medium, such as a hard disk, a floppy, a memory etc. The software may be sent as a signal along a wire, or wireless, or using a data network, e.g., the Internet. The software may be made available for download and/or for remote usage on a server. A method according to the invention may be executed using a bitstream arranged to configure programmable logic, e.g., a field-programmable gate array (FPGA), to perform the method.

It will be appreciated that the invention also extends to computer programs, particularly computer programs on or in a carrier, adapted for putting the invention into practice. The program may be in the form of source code, object code, a code intermediate source and object code such as partially compiled form, or in any other form suitable for use in the implementation of the method according to the invention. An embodiment relating to a computer program product comprises computer executable instructions corresponding to each of the processing steps of at least one of the methods set forth. These instructions may be subdivided into subroutines and/or be stored in one or more files that may be linked statically or dynamically. Another embodiment relating to a computer program product comprises computer executable instructions corresponding to each of the means of at least one of the systems and/or products set forth.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments.

In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

In the claims references in parentheses refer to reference signs in drawings of embodiments or to formulas of embodiments, thus increasing the intelligibility of the claim. These references shall not be construed as limiting the claim.

Claims

CLAIMS:

A charging device (100) for charging a charge storage device by an electromagnetic field radiated into the free space, the electromagnetic field comprising multiple electromagnetic signals at different radio frequencies, the charging device (100) comprising:

an antenna interface (20) adapted for receiving the multiple electromagnetic signals at different radio frequencies,

rectifiers (30) for simultaneously rectifying the received multiple electromagnetic signals into corresponding rectified signals having rectified voltages and rectified currents, respectively, each rectifier having a rectifier input (50) for electrically coupling to an output of the antenna interface (20) for receiving one of the multiple electromagnetic signals at one radio frequency and a rectifier output (60) for outputting the corresponding rectified signal,

switching circuit (70) configured for electrically coupling a rectifier output to at least another rectifier output, selectively in series or in parallel, for adding at least two rectified signals and selectively supplying the added rectified signals to the charge storage device (90),

a control circuit (80) configured for controlling the switching circuit for controlling the supplied rectified signals based on the rectified voltages.

A charging device according to claim 1 , wherein the antenna interface (21 ) comprises a receiving antenna (10) and a matching circuit (15) having an input for electrically coupling to the receiving antenna and multiple outputs for electrically coupling to respective rectifier inputs, the matching configured for matching the receiving antenna to the different radio frequencies.

A charging device according to claim 1 , wherein the antenna interface (22) comprises multiple receiving antennas (1 1 , 12, 13, 14) for receiving the respective multiple electromagnetic signals, wherein each receiving antenna (1 1 ; 12; 13; 14) is electrically coupled to a respective rectifier input.

A charging device according to any one of the preceding claims, wherein the control circuit is configured for controlling the switching circuit for adding one or more rectified voltages and/or adding one or more rectified currents.

5. A charging device according to claim 4, wherein the rectified voltages are added conditional on the added rectified voltages being equal or higher than a threshold voltage for obtaining an overvoltage value.

6. A charging device according to any of the preceding claims, wherein the control circuit (81 ) comprises a voltage measuring circuit (85) for measuring the rectified voltages and/or a current measuring circuit (86) for measuring a rectified current corresponding to the supplied rectified signals.

7. A charging device according to any one of the preceding claims, wherein each rectifier output comprises a first output terminal and a second output terminal for outputting the rectified voltage across the first output terminal and the second output terminal, and

- the rectified current via one of the first output terminal or second output terminal.

8. A charging device according to any one of the preceding claims, wherein the control circuit is configured

for selecting a first set and a second set of one or more rectifiers, and

for controlling the switching circuit for

electrically coupling the rectifier outputs of the first set in series,

electrically coupling the rectifiers outputs of the second set in parallel,

electrically coupling the coupled rectifier outputs of the first set to the coupled rectifier outputs of the second set in series, wherein the first set is selected so that the rectified voltage of the coupled rectifier outputs in series is equal or higher than a threshold voltage for obtaining an overvoltage value.

9. A charging device according to any one of the preceding claims and dependent on claim 5, wherein the control circuit is configured for controlling the switching circuit for electrically connecting two overvoltage values in parallel if more than one overvoltage value is obtainable by adding the rectified voltages, and/or

if more than one rectified voltage remains unused for obtaining another overvoltage value,

electrically connecting the remaining rectified voltages in a parallel arrangement between each other for obtaining a first rectified current equal to the sum of the rectified currents corresponding to the respective remaining rectified voltages, and

electrically connecting the parallel arrangement in series with the one or more overvoltage values, or

otherwise electrically connecting the one unused rectified voltage in series with the one or more overvoltage value.

10. A charging device according to any one of the preceding claims and dependent on claim 5, wherein the control circuit is configured for electrically decoupling the rectifier outputs from the charge storage device when the overvoltage value cannot be obtained.

1 1. A charging device according to any one of the preceding claims, wherein at least one rectifier is a Tesla air circuit comprising

a Tesla input electrically coupled to the antenna interface,

a Tesla positive output terminal electrically coupled to a positive terminal of the charge storage device, and

a Tesla negative terminal electrically coupled to a negative terminal of the charge storage device.

12. A charging device according to any one of the preceding claims, further comprising at least one Joule thief circuit electrically coupled to the charge storage device for transferring electrical power from the charge storage device to a further charge storage device.

13. A charging device according to any one of the preceding claims, wherein the antenna interface (20; 21 ; 22) is configured to receive the multiple electromagnetic signals at radio frequency corresponding to one or more of communication technology: Wifi, FM, GSM, UMTS, LTE, 802.1 1 communication technology.

14. A charging system (600) comprising the charging device (100) according to any of the claims 1 to 14 and a further charge storage device (97) for powering a portable device, the further charge storage device being electrically coupled to the charge storage device (95) for charging the further charge storage device (97).

15. A method of charging a charging storage device by an electromagnetic field radiated into the free space, the electromagnetic field comprising multiple electromagnetic signals at different radio frequencies, the method comprising

Receiving (1010) the multiple electromagnetic signals at different radio frequencies, Rectifying (1020) the received multiple electromagnetic signals into corresponding rectified signals having rectified voltages and rectified currents

- Adding (1030), selectively in series or parallel, at least two rectified signals for selectively supplying the added rectified signals to the charge storage device, Controlling (1040) the supplied rectified signals based on the rectified voltages.