Patent Application
20240006920
The present disclosure relates to wireless charging systems and in particular to wireless charging transmitters, controllers therefor and methods of operating such controllers and transmitters.
Wireless charging systems and solutions are becoming increasingly important in several fields of application, including consumer and automotive products. Wireless charging efficiency and safety can be significantly affected or compromised by the presence of foreign objects in the vicinity of the transmitter and/or receiving coil. It is important to be able to effectively identify situations in which a foreign object is or may be present. It is known to use resonance methods to identify a foreign object which may affect the charging, since the resonance of the transmitter is typically affected by any foreign object which would also affect the charging performance (for instance by changing the resonant frequency and/or level of coupling between the transmitter and receiver).
Resonance methods are generally straightforward to employ in wireless charging systems in which the resonance tank including the transmitter inductor coil and a series capacitor is directly coupled to a driving circuit such as a full-bridge inverter, since the series L-C resonance tank can readily be made to resonate. However, some wireless charging systems benefit by including a filter between the series L-C resonance tank and the driving circuit. It may be desirable to be able to employ resonance methods with transmitters including such filters without using lossy measurement circuits.
According to a first aspect of the present disclosure, there is provided a controller for: a wireless charging transmitter circuit having a full-bridge inverter having first and second full-bridge output nodes, a resonance circuit comprising a series arrangement of a transmitter inductor and a first capacitor, and a second capacitor in parallel with the series arrangement, the wireless charging transmitter circuit further including a PI-filter comprising the second capacitor and first and second filter inductors coupled between first and second terminals of the second capacitor and the first and second full-bridge output nodes respectively; wherein the controller is configured to or operable to measure a Q-factor of the resonant circuit by: controlling the full-bridge inverter to connect an input voltage supply to the PI-filter to supply an excitation] pulse to the resonant circuit; controlling the full-bridge inverter to disconnect the input voltage supply and initiate a resonance in the resonant circuit; controlling a switch in the full-bridge inverter to provide a reference ground to a first terminal of the transmitter inductor; and measuring a decay of the voltage across the transmitter inductor. By connecting only one of the legs of the PI-filter to a fixed voltage, the transmitter inductor may be allowed to freely resonate only with the series capacitor Cser, and parallel capacitor Cpar. The inductors in the PI-filter have been effectively disconnected from the circuit, allowing for a “clean” free resonance which does not suffer from distortion due to the PI-filter, and may allow for voltage-based measurements.
According to one or more embodiments, measuring a decay of the voltage across the transmitter inductor comprises measuring a decay of the voltage at the second terminal of the transmitter inductor. In other embodiments, a differential measurement may be made. Measuring a decay of the voltage at the second terminal of the transmitter inductor may comprise measuring a first voltage at a central node of a resistive voltage divider coupled between a ground and a supply rail, the central node being coupled to the second terminal of the transmitter inductor by a first coupling capacitor in series with a first coupling resistor.
According to one or more embodiments, the controller is further configured to or operable to determine a power-loss during wireless charging. The measurement circuitry for measuring the resonance signal(s) may also be used in the power-loss measurements. In particular, the current in the transmitter coil (that is to say, the current in the transmitter inductor Lp) may be determined. Furthermore, measurement of the coil current may be used for additional, or alternative, purposes such as protection of the coil by avoiding overcurrent in the coil.
According to one or more embodiments, determining a power-loss during wireless charging comprises measuring a second voltage at a central node of a second resistive voltage divider coupled between the ground and the supply rail, the central node being coupled to the first terminal of the first capacitor by a second coupling capacitor in series with a second coupling resistor. According to one or more such embodiments, determining a power-loss during wireless charging comprises measuring a differential voltage between the first voltage and the second voltage. The single of differential voltage signals may enable demodulation of any residual communication information which may still reside in the resonance signal.
According to one or more embodiments, determining a power-loss during wireless charging comprises determining a current through the transmitter inductor from the differential voltage between the first voltage and the second voltage. Coil current so determined may be used in system protection, and additionally or alternatively, may be used to calculate the internal power-loss of the wireless charging transmitter.
According to a second aspect of the present disclosure, there is provided wireless charging transmitter circuit, comprising: a controller as described above, and the full-bridge inverter having two full-bridge output nodes. The full-bridge inverter may comprise MOSFETs. The MOSFETs may be co-packaged with the controller of or may be separately packaged. The wireless charging transmitter circuit may further comprise the resonant circuit comprising the series arrangement of the transmitter inductor and the first capacitor, and a second capacitor in parallel with the series arrangement; and a PI-filter comprising first and second filter inductors coupled between first and second terminals of the second capacitor and the first and second full-bridge output nodes respectively.
According to a further aspect of the present disclosure, there is provided a method of operating a wireless charging transmitter having a full-bridge inverter suppling a resonant circuit, which may be a series L-C resonant circuit, with a PI-filter therebetween, the method comprising: controlling the full-bridge to connect an input voltage supply to the PI-filter to supply an excitation pulse to the resonant circuit; controlling the full-bridge inverter to disconnect the input voltage supply and initiate a resonance in the resonant circuit; controlling a switch in the full-bridge inverter to provide an reference ground to a first terminal of the transmitter inductor; and measuring a decay of the voltage at a second terminal of the transmitter inductor.
In one or more embodiments, measuring a decay of the voltage at the second terminal of the transmitter inductor comprises: measuring a first voltage at a central node of a resistive voltage divider coupled between a ground and a supply rail, wherein the central node is coupled to the second terminal of the transmitter inductor by a first coupling capacitor in series with a first coupling resistor.
In one or more embodiments, the wireless charging transmitter has a power transfer mode, and the method further comprises determining a power-loss during operation of the wireless transmitter in the power transfer mode.
In one or more embodiments, determining a power-loss during operation of the wireless charging transmitter in the power transfer mode comprises: measuring a second voltage at a central node of a second resistive voltage divider coupled between the ground and the supply rail, wherein the central node is coupled to the first terminal of the first capacitor by a second coupling capacitor in series with a second coupling resistor.
In one or more embodiments, determining a power-loss during operation of the wireless charging transmitter in the wireless charging comprises measuring a differential voltage between the first voltage and the second voltage.
There may be provided a computer program, which when run on a computer, causes the computer to configure any apparatus, including a circuit, controller, sensor, filter, or device disclosed herein or perform any method disclosed herein. The computer program may be a software implementation, and the computer may be considered as any appropriate hardware, including a digital signal processor, a microcontroller, and an implementation in read only memory (ROM), erasable programmable read only memory (EPROM) or electronically erasable programmable read only memory (EEPROM), as non-limiting examples. The software implementation may be an assembly program.
The computer program may be provided on a computer readable medium, which may be a physical computer readable medium, such as a memory device, or may be embodied as another non-transient signal.
These and other aspects of the invention will be apparent from, and elucidated with reference to, the embodiments described hereinafter.
Embodiments will be described, by way of example only, with reference to the drawings, in which
It should be noted that the Figures are diagrammatic and not drawn to scale. Relative dimensions and proportions of parts of these figures have been shown exaggerated or reduced in size, for the sake of clarity and convenience in the drawings. The same reference signs are generally used to refer to corresponding or similar features in modified and different embodiments
The voltage Vser (relative to ground 162) may be measured using an RC circuit at a node P1155 between series capacitor 150 and the transmitter inductor Lp, as shown at 180. The Q-factor of the resonant circuit may be derived, as shown at 186, from the rate of decay of the voltage 184]. Moreover, using an RC circuit connecting node 155 to ground, the coil currents during power transfer may be measured in order to calculate the power loss.
It will be noted that the resonant circuit 190 of the transmitter coil includes not only the series capacitor 150 and the transmitter inductor 130 but in addition, it includes the parallel capacitor 216. Further, it will be noted that, unlike the resonant circuit 190 in the directly connected transmitter, the resonant circuit in this transmitter which includes a PI-filter is not directly connected to ground at 162, even if switch S4148 is closed: in other words, the reference voltage may be floating. In consequence, a simple RC divider circuit connection between the series capacitor 150 and ground, in order to determine the voltage at Cser and thence the current in the resonance, may no longer directly be possible. Instead, it has been suggested to use a transformer 230 acting as a current sensor in the loop. The secondary winding of the current sensing transformer 230 can be connected to a coil current sensing circuit 240. The sensed coil current may be also used for Q-factor measurements (during resonance prior to or in between power transfer), as well as in a power loss calculation during wireless charging.
It is challenging to determine the Q factor, because the signal is floating. An accurate coil current is difficult to obtain, and moreover, it is difficult to obtain the equivalent loop impedance of the complex PI-filter and Cser, since the voltage from one point of Cser-to-GND cannot be easily obtained.
According to the present disclosure, the switches in the full bridge are dynamically controlled in order to create a desired resonance tank, and this results in a relatively distortion-free resonance. Such a “clean” resonance 410 in the tank is shown in
The full bridge may comprise four MOSFETs as shown, —S1512, S2514, S3516, and S4518. The full bridge connects a DC input supply, shown connected between a supply rail 525 and ground rail 535, in which S1 and S3 selectively connect the supply rail 525 to first and second outputs 542 and 544 respectively, and S2 and S4 selectively connect the ground rail 535 to the first and second output nodes 542 and 544 respectively. The voltage on the supply rail 525 of the DC input supply may typically be 9V or more.
Operation of the circuit of shown in
The power transfer phases shown at 582 and 586 are the same as in conventional operation of a wireless charging circuit. That is to say, switches S2514 and S3516 are switched to be in the complimentary states to switches S1512 and S4518. The timing of the switching is controlled, according to known methods for instance by PWM control (a 50% duty cycle as shown), in order to result in an AC current being transferred through the PI-filter to the transmitter inductor 530, in order to enable power transfer to the receiver (not shown).
At the start of the resonance measurement phase 584, switches S2 and S4 are switched on and switches S1 and S3 are switched off. Both output nodes 542 and 544 of the half bridge are thus connected directly to the ground rail 535. As shown at 588, a driving, or excitation, pulse is then supplied to the PI-filter in order to prime the resonant circuit. This is done by a closing switch S1512 and opening S2, to connect the first output node 542 to the supply rail 525. S3516 and S4518 are not changed during this pulse since S3516 is already open and S4518 closed such that the second output node 544 is connected to ground rail 535.
At the end of the pulse, conventionally all the switches would be opened in order to establish the resonance in the complex circuit comprising the PI-filter and transmitter inductor LP together with series inductors Cser during a subsequent resonance subinterval or phase 590. However, according to embodiments of the present disclosure, switch S2 is returned to an “on” or closed state in order to connect the resonant circuit to ground, since by closing S2514, the first output node 542 is directly connected to ground. The skilled person will appreciate that the present disclosure is not limited to closing S2; in other embodiments S4 may, instead, be closed such that the second output node is grounded during the remainder of the resonance phase. In still other embodiments, one of S1512 and S3516 is closed in order to connect first or second output node 542 or 544 respectively to an alternative fixed voltage (in this case the DC voltage at the supply rail 525). In general, it will be appreciated that during the resonance time 590, one and only one of the switches is closed, in order to fix a voltage at one point of the resonant circuit. In other words, during the resonance measurement subinterval or phase 590, the controller controls a switch in the full-bridge inverter to provide an reference ground to a first terminal of the transmitter inductor. The reference ground may also be referred to as an AC ground, since the ground connection is through one inductive leg of the PI filter. The fixed voltage at one of the output nodes of the full bridge constitutes an reference ground to a first one terminal of the transmitter inductor, since at the resonance frequency, the PI-filter inductors L1524 and L2526 provide a low impedance path between the transmitter inductor and the fixed voltage point. The fixed voltage point may, as already mentioned, typically be a ground reference or a supply rail reference.
During the resonance time 590, since only one of the output node 542 and 544 are connected to a fixed DC voltage (either ground 535 or the supply voltage at the supply rail 525), there is only a simple resonance circuit comprising the transmitter inductor 530, the series capacitor Cser 540, and the parallel capacitor Cpar 522. The inductors L1524 and L2526 in the legs of the PI-filter do not form part of the resonance. In consequence, as shown in the bottom waveform 570 of
Operation of the circuit of shown in
Operation of the circuit of
From reading the present disclosure, other variations and modifications will be apparent to the skilled person. Such variations and modifications may involve equivalent and other features which are already known in the art of wireless charging and which may be used instead of, or in addition to, features already described herein.
Although the appended claims are directed to particular combinations of features, it should be understood that the scope of the disclosure of the present invention also includes any novel feature or any novel combination of features disclosed herein either explicitly or implicitly or any generalisation thereof, whether or not it relates to the same invention as presently claimed in any claim and whether or not it mitigates any or all of the same technical problems as does the present invention.
It is noted that one or more embodiments above have been described with reference to different subject-matters. In particular, some embodiments may have been described with reference to method-type claims whereas other embodiments may have been described with reference to apparatus-type claims. However, a person skilled in the art will gather from the above that, unless otherwise indicated, in addition to any combination of features belonging to one type of subject-matter also any combination of features relating to different subject-matters, in particular a combination of features of the method-type claims and features of the apparatus-type claims, is considered to be disclosed with this document.
Features which are described in the context of separate embodiments may also be provided in combination in a single embodiment. Conversely, various features which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination.
For the sake of completeness it is also stated that the term “comprising” does not exclude other elements or steps, the term “a” or “an” does not exclude a plurality, a single processor or other unit may fulfil the functions of several means recited in the claims [delete if not relevant] and reference signs in the claims shall not be construed as limiting the scope of the claims. Furthermore, the word “may” is used in a permissive sense (i.e., meaning having the potential to), rather than the mandatory sense (i.e., meaning must). Similarly, the words “include,” “including,” and “includes” mean including, but not limited to.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202210776283.3 | Jun 2022 | CN | national |
