KR102185160B1 - Methods for detecting and identifying a receiver in an inductive power transfer system - Google Patents

Abstract

A method of detecting the presence of a receiver in an inductively coupled power transmission system having a transmitter and a receiver is disclosed. The method includes switching on the converter at a first frequency, measuring an inrush current, and detecting whether a receiver is present. In another method, the inrush current is measured over a range of transmitter frequencies, and the variation in current is used to determine where the receiver is. In another method, the inrush current is measured to measure when there is a change in voltage at the transmitter, and the shift in current is used to determine where the receiver is. In another method, the current supplied to the transmitter converter is measured across two transmitter frequencies, and the variation in current is used to determine where the receiver is present. In another method, the current supplied to the transmitter converter is measured across two transmitter voltages, and the variation in current is used to determine where the receiver is present.

Description

Methods for detecting and identifying a receiver in an inductive power transfer system

The present invention relates to the field of inductive power transfer (IPT). More specifically, the present invention relates to methods for detecting the presence and/or identifying a receiver to be utilized in such systems.

IPT systems are a well-known area of established technology (eg, wireless charging of electric toothbrushes) and evolving technology (eg, wireless charging of handheld devices on a'charging mat'). Typically, the primary side or transmitter uses a transmitting coil or coils to create a time varying magnetic field. This magnetic field induces an alternating current in the battery, or a suitable receiving coil that can then be used to charge the power device or other load. In some examples, the transmitter coils or receiver coils are connected to capacitors to create a resonant circuit, which can increase power throughput and efficiency at a corresponding resonant frequency.

A common problem in IPT systems is controlling when the transmitter should be powered and when the transmitter should be switched off. Additional problems arise when bringing the non-receiver into range of the transmitter, and unwanted current (and hence heat) is induced in the non-receiver. These non-receivers are commonly known as parasitic loads. Eventually, it may be possible to detect the presence of a receiver, but it may also be necessary to identify if the receiver is compatible with that particular transmitter. Attempting to transfer power to non-compliant receivers may result in inefficient power transfer (and thus unwanted energy loss), or transmitter and/or receiver failure.

The obvious solution to the problems outlined above is to include a manually operated power switch in the transmitter. Although this provides a means to control when the transmitter should be powered, it hurts the convenience that is the goal of many IPT systems. It also requires the user to manually switch off the transmitter when the receiver is removed and does not adjust any parasitic loads that may be introduced in close proximity to the transmitter without the user knowing.

Automatic systems for detecting and identifying receivers have been described in the prior art. For example:

-Systems that rely on contact-based interaction between transmitter and receiver;

-Systems that rely on communication signals transmitted between the transmitter and receiver; And

-Systems using non-radio proximity sensors (eg light sensors) to detect the physical presence of receivers.

All of these approaches rely on additional components to implement the detection method. This adds complexity and cost to the design of IPT systems. Perhaps more importantly, they tend to increase in size, which frustrates attempts to integrate IPT systems into smaller devices such as mobile phones, personal computers, and the like.

In order to reduce these effects, it is known that IPT systems likewise utilize the power transmission component for detection and identification (ie, for multiple purposes).

The weaknesses of these approaches are:

-Power transmission may need to be reduced or completely blocked to perform the detection method;

-If a steady-state current is used as an indicator of the receiver, no-load receivers may give false results;

-May be sensitive to component deviations and noise; And

-It may be impossible to identify whether or not the detected receiver is compatible.

The object of the present invention is that it does not require the extensive additional components required for the induced power, yields precise results that are not sensitive to noise, limits the time when power is not transmitted, and can reliably identify the receiver. Or at least to provide methods for detecting or identifying a receiver that may provide a useful choice to the public.

The scope of the invention is as set forth in the claims appended to the end of this specification.

The terms "comprise, comprises" and "comprising" are admitted to be in either the exclusive or collective meaning under varying judgments. For the purposes of this specification, and otherwise, these terms are intended to have a collective meaning. That is, they contain listed components that use references directly, and it will be considered to contain other-unspecified components or elements as well.

Reference to any prior art in this specification does not constitute an admission that such prior art forms part of a common general knowledge.

The effects of the invention are specified individually in the corresponding parts of this specification.

The accompanying drawings are incorporated into and constitute a part of this specification, and illustrate embodiments of the present invention together with a general description of the present invention given above and a detailed description of the embodiments given below, and illustrate the principles of the present invention. It is helpful to explain.
1 shows a block diagram of an IPT system.
2A-5 show sample data sets.

Embodiments of the present invention relate to a method of detecting or identifying a receiver in an Inductive Power Transmission (IPT) system. 1 is a block diagram showing a general representation of an IPT system (1). The IPT system includes a transmitter (2) and a receiver (3). The transmitter is connected to a suitable power supply (5). In Fig. 1 this is shown as a converter connected to a DC-DC converter 6, which DC-DC converter is connected to the mains power supply. The converter may be a non-resonant half bridge converter or any other converter adapted for the particular IPT system, such as a push-pull converter. The converter is configured to output an alternating current of a desired frequency and amplitude. The voltage at the output of the converter may also be regulated by the converter, the DC-DC converter, or a combination of both.

The converter 4 is connected to the transmission inductor(s) 7. The converter supplies the transmission conductor(s) along with an alternating current, causing the transmission inductor(s) to generate a time-varying magnetic field with an appropriate frequency and strength. In some configurations, the transfer inductors may also be considered to be a component part of the converter, but for clarity of this description the transfer inductors will be referred to as separate.

The transmission inductor(s) 7 may be of any suitable configuration of coils, which depends on the specific application of the transmitter and the characteristics of the magnetic field required in the specific external shape. In some IPT systems, the transfer inductors may be connected to capacitors (not shown) to create a resonant circuit.

1 also shows the controller 8 in the transmitter 2. The controller can be connected to each part of the transmitter. The controller is adapted to receive input from each part of the transmitter and to produce outputs that control how each part of the transmitter operates. The controller may comprise a memory 9. The controller is preferably a programmable logic controller programmed to perform different computational tasks dependent on the requirements of the IPT system.

In addition to the features of the general IPT system 1 summarized above, FIG. 1 also shows a representation of the sensor 10. Such a sensor is configured to detect the special operating characteristics of the transmitter 2 and may thus be connected to other parts of the transmitter. In Fig. 1, the sensor is shown to be connected to the contact between the DC-DC converter 6 and the converter 4, which is suitable for measuring the current being supplied to the converter. Of course, other sensors may be needed and the invention is not limited in this respect.

In some embodiments of the invention described in more detail below, the sensor 10 is adapted to measure current. Those of ordinary skill in the art to which the present invention pertains will appreciate that there are many possible types of sensors adapted to measure current, and the present invention is not limited in this respect. One example is a current sense resistor. It will be appreciated that a suitable current sensor will be used that can measure the desired current characteristic depending on the required functionality. This will be explained in more detail later.

1 also shows a receiver 3. The receiver comprises a receiving inductor(s) 11 suitably connected to a receiver circuit 12, which receiver circuit supplies power to the load 13. The load may be a battery. The receiver circuit is adapted to convert the induced current into a shape suitable for the load. In some IPT systems, the receiving inductors can be connected to capacitors (not shown) to create a resonant circuit.

Five embodiments of methods for detecting and/or identifying receivers in an IPT system, or for detecting non-receiver behaviors will now be described. Although these methods will be described in relation to the IPT system 1 described in connection with Fig. 1, the methods will be adapted to operate using any number of suitable IPT system configurations, and similarly IPT systems will It will be understood that it operates using s, and the invention is not limited in this respect.

Inrush current detection method (INRUSH CURRENT DETECTION METHOD)

According to an embodiment of the present invention, the inrush current detection method starts using a transmitter in a standby mode. In this mode, the transmitter is controlled to absorb minimal current. The transmitter periodically switches from standby mode to detection mode to detect whether any receivers have entered the transmission range of the transmitter. In a preferred embodiment of the present invention, the transmitter is configured to temporarily switch to the detection mode every 2 seconds. Alternatively, if another detection method precedes the inrush current detection method, the transmitter may already be in the detection mode.

Upon switching to the detection mode, the controller controls the converter, causing the converter to supply an initial high frequency alternating voltage to the inductor. In case the IPT system has resonant networks, the frequency should be non-resonant. In an embodiment of the present invention, the frequency may be 1 MHz-10 MHz. Such current removes any residual DC biases that may be present in the capacitors in the IPT system. Eliminating such biases improves the reliability of subsequent steps of the method. Other methods could be used to remove DC biases in a system such as a voltage divider or to replace a half bridge inverter with a full bridge inverter. In a preferred embodiment, a high frequency current is supplied for a sufficient time interval until the steady state is reached. In one embodiment of the invention, this time period is of the order of approximately 10 ms.

In the next step, the controller controls the converter, causing the converter to supply alternating current to the inductor at a test frequency. In the preferred embodiment, this is the frequency at which the receiver will have the strongest influx. This frequency may be at or near the frequency at which the transmitter is configured to transmit power. Those of ordinary skill in the art to which the present invention pertains will appreciate that this frequency is dependent on the circuit components used in the transmitter. For typical IPT systems this may be approximately 100 kHz-approximately 1 MHz. In a preferred embodiment, the test frequency is approximately 150 kHz or close to approximately 150 kHz.

If you supply current at the test frequency, there will be an inrush period, during which transient currents will flow through the circuit components in the transmitter and any receiver that may be present. The presence of transient currents is a well-known phenomenon in circuits. However, transient currents are usually ignored until the system reaches a steady state. Conversely, these transient currents form the basis of the inrush current detection method.

The sensor is configured to measure the current supplied to the converter. As shown in Fig. 1, the sensor 10 can be connected to a contact point between the converter 4 and the DC-DC converter 6. During the inflow period, the sensor measures the amplitude of the current being supplied to the converter. In one embodiment, the sensor measures the peak amplitude during the inflow period. In one embodiment, the sensor may comprise a peak amplitude detection circuit for this purpose. The controller may be configured to provide the inflow period as input to the sensor. In an alternative embodiment, the sensor will be able to continuously measure the current amplitude during the inrush period using the measurements being provided as input to the controller, which is configured to determine the peak amplitude from this data. do.

The peak amplitude of the current is then provided to the controller. The controller is configured to determine whether the peak amplitude exceeds a threshold. If no receiver is present then the peak current is due to a transient current in circuit components in the transmitter only. However, if there is a receiver present, then the peak current will usually be higher due to transient currents in the receiver. Therefore, the threshold is preferably chosen to be higher than any peak currents that only transmitter components can be responsible for. Advantageously, this is achieved by adjusting the controller with respect to the particular configuration of the transmitter. Non-receivers may also influence the magnitude of the peak current measured during the inrush period. Therefore, select the threshold so that the transient currents in receivers are still low enough to ensure that the measured peak amplitude exceeds the threshold, while the threshold is high enough to exclude non-receivers. It may also be necessary to do.

In an embodiment of the present invention, the sensor may measure multiple peak currents during the inflow period. The sensor and/or controller may be configured to ignore peaks that are characteristic of the transmitter. Again, this could be done through adjustment of the sensor and/or controller with reference to the configuration of the transmitter.

If the measured peak current exceeds the threshold, then there is a possibility that the receiver is within the range of the transmitter, so the controller will then be able to:

-Controlling the controller so that power is transmitted to the receiver;

-Controlling the transmitter according to additional detection methods to further verify the presence of the receiver; or

-Controlling the controller according to additional identification methods to identify the compatibility of the receiver with the transmitter.

If the measured peak current falls below the threshold, there is a possibility that the receiver is not within the full-term range, so the controller will be able to:

-Controlling the transmitter according to additional detection methods to detect the presence of the receiver;

-Bring the transmitter back to the previously described standby mode; or

-Switch off the transmitter.

Frequency progressive change detection method (FREQUENCY SWEEP DETECTION METHOD)

According to an embodiment of the present invention, the frequency sweep detection method starts using the transmitter in the standby mode described above under the inrush current detection method. Alternatively, the transmitter may already be in the detection mode if another detection method has preceded the frequency gradual change detection method.

Upon switching to the detection mode, the transmitter is controlled according to the inrush current detection mode described above, up to the stage when the peak amplitude of the current is provided to the controller. Then, instead of determining whether the peak amplitude exceeds a threshold, the controller stores the value of the test frequency as well as the peak amplitude in memory.

Then, the transmitter is again controlled until the peak amplitude of the current is provided to the controller according to the inrush current detection mode described above, but this time the operation is performed at the second test frequency. The controller stores the value of the second test frequency as well as the peak amplitude in the memory.

This step is repeated for a plurality of test frequencies over a range of frequencies. As a result of this, the memory is provided with a record of the peak amplitude currents measured during the inflow period over a range of frequencies. In a preferred embodiment, the range of frequencies is chosen so that the receiver is centered with respect to the frequency at which the strongest influx will be. This frequency may be at or near a frequency at which the transmitter is configured to transmit power.

The controller then analyzes the record to determine if there is a maximum in the relationship between the peak amplitudes of the currents and the test frequencies. The controller determines whether or not a maximum exists by any suitable method of function analysis.

2A and 2B show two example data sets. It can be seen that in the first data set of FIG. 2A there is some deviation, but no separable maximum. Conversely, the second data set in Figure 2b shows the maximum (14) that can be separated. The controller is

As exemplified by the second data set in FIG. 2B, a maximum exists only when there is a sufficiently large maximum in the environment of the data set as a whole (i.e., it does not necessarily have to be a maximum in a strictly mathematical sense). It could be configured to determine that it is.

The controller then determines the parameters associated with that maximum. This may include the maximum width (such as a full-width half-maximum metric), the maximum height and the frequency at which the maximum occurs. Again, those of ordinary skill in the art will understand that any suitable method of performing function analysis can be adapted and used by the controller for this purpose. The controller may be able to flatten or average the results to improve the reliability of the analysis. Referring to Fig. 3, another data set representing a maximum of 15 is shown. In this example, the maximum has a width of 32 kHz, a height of 2.0, and occurs at 120 kHz.

In one embodiment, analyzing the maximum may include the following:

-Subtract the baseline data from the measured data so that any result is compared to the baseline;

-Smoothing and filtering noise by performing shifting the average of three widths over the data points;

-Locate the largest edges by finding where the slope changes polarity;

-Locate the top of the maximum by finding the largest value between the maximum edges;

-Measure the height at the largest edges;

-The maximum width may be defined as the width between the largest edges; And

-The maximum height may be defined as the vertical distance from the height at the higher of the maximum edges to the height at the top of the peak.

If a receiver is present, then the maximum will result in displaying some or all of these characteristics. For example, the resonant receiver will cause a maximum to occur at the resonant frequency of the receiver, because more transient current will flow when the resonant receiver and the transmitter are combined. Also, because the frequency at which the maximum occurs will be able to identify the type of receiver. For example, a receiver that causes the maximum in Fig. 3 to be calculated is configured to resonate at 120 kHz. Since the resonant frequency of the receiver may be unique to the type of receiver, the controller will be able to identify whether the receiver is compatible with the transmitter. In other words, the maximum may be a resonance'signature'. Thus, it will be appreciated that the frequency progressive change detection method may be a method for detecting a receiver, but may also be a method for identifying a receiver.

The controller includes predetermined parameters, and the controller compares the maximum parameters against these parameters. For example, the predetermined parameters may provide that the maximum must have or exceed a certain width and/or a certain height, and/or must occur at a certain frequency, at frequencies or within a frequency range. have.

If the controller determines that the maximum of the parameters satisfies the predetermined parameters, then there is a possibility that the (detected) receiver or the (identified) compatible receiver is within the range of the transmitter, or a previously detected receiver There is a possibility that is compatible with the transmitter. So the controller would be able to do the following:

-Controlling the controller so that power is transmitted to the receiver;

-Controlling the controller according to additional detection methods to further verify the presence of the receiver; or

-Control the transmitter according to additional identification methods to further identify the receiver's compatibility with the transmitter.

If the controller determines that the maximum parameters do not meet the predetermined parameters or that no maximum exists, then the receiver may not be within the range of the transmitter or the receiver may not be compatible with the transmitter. There is a possibility that there is. So, the controller then:

-Controlling the transmitter according to additional detection methods to detect the presence of the receiver;

-Return the transmitter to the previously described standby mode; or

-Switch off the transmitter.

INRUSH CURRENT REMOVAL DETECTION METHOD

According to an embodiment of the present invention, the inrush current removal detection method starts using a transmitter in a power mode. In one embodiment, the transmitter has already detected the presence of a receiver and has started transmitting power to the receiver. In power mode, the transmitter is controlled to transmit power to the receiver. The converter and DC-DC converter will be controlled to supply alternating current to the inductor at an operating frequency and operating voltage.

The transmitter periodically switches from the power mode to a power-detection mode (ie, a mode for detecting receivers or parasitic loads while transmitting power) to detect whether the receiver has been removed from the range of the transmitter. In a preferred embodiment of the present invention, the transmitter is configured to temporarily switch to the power-detection mode every 2 seconds.

When switching to the power-detection mode, the controller controls the converter or DC-DC converter so that the inductor is supplied with a slightly lower voltage. The lower voltage should not be so small that it affects the rated power transmission from the transmitter to the receiver. In one embodiment, the smaller voltage is less than 4% smaller than the operating voltage. The system is then allowed to reach a steady state under that smaller voltage.

Next, the controller controls the converter or DC-DC converter so that the inductor is supplied with a higher voltage. The higher voltage should not be so high that it affects the rated power transmission from the transmitter to the receiver. In one embodiment, the higher voltage is less than 4% higher than the operating voltage. The higher voltage may be the operating voltage.

Increasing the voltage in this manner will result in an inrush period, and transient currents will flow in the circuit components present in the system. The transmitter measures the peak amplitude of the current supplied to the converter according to the inrush current detection method. The controller also determines whether or not the peak amplitude of the current exceeds a threshold value according to the inrush current detection method described above. Those of ordinary skill in the art to which the present invention pertains to the thresholds, time periods, and characteristic peaks described in connection with the inrush current detection method take into account the fact that the inrush current removal detection method is undertaken during power transmission. You will understand that it will need to be revised.

If the measured peak current exceeds the threshold, then there is a possibility that the receiver may still be within the range of the transmitter, so the controller will be able to:

-Controlling the controller so that power is transmitted to the receiver, which may include returning the voltage of the transmitter to the operating voltage.

If the measured peak current falls below the threshold, then there is a possibility that the receiver is no longer within the range of the transmitter, so the controller will be able to:

-Controlling the transmitter according to additional detection methods to verify the absence of the receiver;

-Return the transmitter to the previously described standby mode; or

-Switch off the transmitter.

In another embodiment of the inrush current elimination detection method, rather than initially reducing the voltage to a smaller voltage, the voltage may be increased to a higher voltage, and the inrush current measured in this step. In this embodiment, the higher voltage should not be so high to affect the power transfer from the transmitter to the receiver. In one embodiment, the higher voltage is less than 4% higher than the operating voltage.

In another embodiment of the inrush current elimination detection method, rather than additionally reducing the burn voltage to a smaller voltage, the voltage is reduced to zero during a first test period and then returns to the operating voltage. When the voltage is increased inversely to the operating voltage, the measured inrush current is measured according to the above description.

The first test period is short enough so that switching the voltage to zero does not affect the power transfer from the transmitter to the receiver, especially if the receiver has a load. In one embodiment of the present invention, the first test period is approximately 10 us. Such a short test period may allow the DC voltages in the receiver to be sufficiently reduced to measure the resulting transient current. Thus, the test is repeated over a series of steps of increasing the test periods to a second test period when there are resulting transient currents that can be measured. Alternatively, if no transient currents are detected in the second test period, then it is determined that no receiver is present. Increasing the test period incrementally in this way allows the inflow period to be observed for the shortest'off-time' required (i.e. 0 volts), so that the receiver has a load. If so, the power transmission will not be interrupted.

Frequency change detection method (FREQUENCY VARY DETECTION METHOD)

According to an embodiment of the present invention, the frequency change detection method starts using a transmitter in a power mode. In one embodiment, the transmitter has already detected the presence of a resonant receiver and has started transmitting power to the resonant receiver. In the power mode, the transmitter is controlled to transmit power to the resonant receiver. The converter and DC-DC converter will be controlled to supply alternating current to the inductor at an operating voltage and operating frequency, in which case the operating frequency is controlled to match the resonance of the receiver.

The transmitter periodically switches from the power mode to a power-detection mode in order to detect whether a conducting non-receiver (i.e., a parasitic load) has entered the range of the transmitter. In a preferred embodiment of the present invention, the transmitter is configured to temporarily switch to the power-detection mode every 2 seconds.

Switching to power-detection mode, the sensor measures the average steady state current being supplied to the converter. The controller stores the frequency value as well as this current value in the memory.

The controller then adjusts the frequency to the test frequency. The test frequency must be close enough to the operating frequency so as not to allow the receiver to escape from resonant conditions, so that it does not affect the rated power transfer from the transmitter to the receiver. In one embodiment, the test frequency differs by less than 4% different from the operating frequency.

The system is then allowed to reach a steady state under that new frequency. The sensor measures the average steady-state current being supplied to the converter. The controller stores the test frequency value as well as this current value in the memory.

The above step is repeated for a plurality of test frequencies over a range of frequencies. Those of ordinary skill in the art will appreciate that this is the result of a memory with a record of measured currents over a range of frequencies thereafter. In a preferred embodiment, the range of frequencies is chosen to be approximately centered around the operating frequency of the transmitter.

The controller then analyzes the record to determine the relationship between the steady state current and test frequencies. The controller determines the relationship by any suitable method of function analysis. The controller may be configured to flatten or average the data to improve the quality of the analysis. In a preferred embodiment, the controller performs a linear regression analysis of the data to determine a proportional constant. Figure 4 shows two example data sets as current on the vertical axis and frequency on the horizontal axis. In the first data set, it can be seen that there is some variation, but overall the slope of the data is close to zero, that is, the proportional constant is zero or nearly zero. Conversely, the second data set shows that the slope is much more negative, i.e. the proportionality constant is more negative.

If there is a receiver, then it will behave as a constant power load, so slight variations in the drive frequency will not affect the amount of power drawn. Therefore, the current drawn by the converter will not change significantly. Conversely, non-receiver behavior (such as a piece of metal) will act as a constant resistive load, so for a transmitting coil running at a constant voltage, slight increases in drive frequency will reduce the amount of current drawn. . Therefore, the current flowing to the converter will also decrease.

It will be appreciated that the proportional constant described above can thus be used as an indicator of the presence of non-receiver behavior. The controller may be adjusted so that only proportional constants with values less than a certain threshold (ie,'sufficiently negative') are considered to be an indication of the presence of non-receiver behavior.

If the controller determines that the proportional constant is not sufficiently negative, then there is a possibility that the non-receiver behavior may not be within the range of the transmitter, so the controller does the following:

-By controlling the transmitter, power is transmitted to the receiver.

If the controller determines that the proportional constant is sufficiently negative, then there is a possibility that a non-receiver behavior (i.e., parasitic load) may be within the range of the transmitter, so the controller does the following:

-Controlling the transmitter according to additional detection methods to verify the presence of non-receiver behavior;

-Bring the transmitter back to the previously described standby mode; or

-Switch off the transmitter.

Voltage change detection method (VOLTAGE VARY DETECTION METHOD)

According to an embodiment of the present invention, the voltage change detection method starts using a transmitter in a power mode. In one embodiment, the transmitter has already detected the presence of a receiver and begins to transmit power to that receiver. In power mode, the transmitter is controlled to transmit power to the receiver. The DC-AC converter and DC-DC converter will be controlled to supply alternating current to the inductor at an operating voltage and operating frequency.

The transmitter periodically switches from power mode to power-detection mode to detect whether non-receiver behavior (i.e., parasitic load) has entered the range of the transmitter. In a preferred embodiment of the present invention, the transmitter is configured to temporarily switch to the power-detection mode every 2 seconds.

Switching to power-detection mode, the sensor measures the average steady state current being supplied to the converter. The controller stores the value of the operating voltage as well as the value of this current in the memory.

The controller then adjusts the voltage of the test voltage. In one embodiment, this is achieved through control of the DC-DC converter. In another embodiment, the converter may be driven at different duty cycles to change the driving voltage. The test voltage should be close enough to the operating voltage so as not to affect the rated power transfer from the transmitter to the receiver. In one embodiment, the test voltage differs by less than 4% different from the operating voltage.

The system is then allowed to reach a steady state under the new voltage. The sensor measures the average steady-state current being supplied to the converter. The controller stores the test voltage value as well as the current value in the memory.

This step is repeated for a plurality of voltages over a range of voltages. Those of ordinary skill in the art will appreciate that this is the result of a memory having a record of measured currents over a range of voltages. In a preferred embodiment, the range of voltages is chosen to be generally centered around the operating voltage of the transmitter.

The controller then analyzes the record to determine the relationship between the steady state current and the test voltage. The controller determines the relationship by any suitable method of function analysis. The controller may be configured to flatten or average the data to improve the quality of the analysis. In a preferred embodiment, the controller performs a linear regression analysis of the data to determine a proportional constant. Figure 5 shows two example data sets as current on the vertical axis and voltage on the horizontal axis. In the first data set, it can be seen that the positive slope, that is, the proportionality constant is positive. Conversely, the second data set shows that the negative slope, that is, the proportional constant is negative.

If there is a receiver, then it will act as a constant power load, so a slight increase in drive voltage will not affect the amount of power drawn. Therefore, the current drawn by the converter will decrease as the applied voltage increases (cf. P = VI). Conversely, a non-receiver behavior (such as a piece of metal) will act as a constant resistive load, so a slight increase in drive voltage will increase the amount of power drawn. Therefore, the current flowing to the converter will also increase (cf. I = V/R).

It will be appreciated that the proportional constant described above can thus be used as an indicator of the presence of non-receiver behavior. The controller may be adjusted such that only proportional constants with values above a certain threshold (ie,'sufficiently positive') are considered to be an indication of the presence of non-receiver behavior.

If the controller determines that the proportional constant is not sufficiently positive, then there is a possibility that the non-receiver behavior may not be within the range of the transmitter, so the controller does the following:

-By controlling the transmitter, power is transmitted to the receiver.

If the controller determines that the proportional constant is sufficiently positive, then there is a possibility that non-receiver behavior (i.e., parasitic load) may exist within the range of the transmitter, so the controller does the following:

-Controlling the transmitter according to additional detection methods to verify the presence of non-receiver behavior;

-Bring the transmitter back to the previously described standby mode; or

-Switch off the transmitter.

The invention has been illustrated by the description of embodiments of the invention, and although the embodiments have been described in detail, it is not the intention of the applicant to limit or limit the scope of the appended claims to such details in any way. Further advantages and modifications will readily appear to those of ordinary skill in the art to which the present invention pertains. Therefore, the invention in its broadest aspects is not limited to the specific details shown and described, representative apparatus and methods, and illustrative examples. Accordingly, without departing from the spirit or scope of the general patent concept of the present applicant, a departure from such details may be made.

Claims (22)

A method for detecting a receiver in an inductively coupled power transmission system, comprising:
The system,
A coil for generating an alternating magnetic field;
A converter for supplying an alternating current to the coil; And
Having a sensor for measuring the current supplied to the converter,
The method is:
Operating the converter at a plurality of frequencies within a frequency range;
Determining a peak amplitude of the current measured using the sensor during an influx period for each of the plurality of frequencies;
Analyzing the characteristics of the determined peak amplitudes within the frequency range; And
Detecting a receiver based on the characteristic meeting a predetermined parameter
How to include. The method of claim 1,
Prior to operating the converter at each of the plurality of frequencies, supplying an alternating current having a non-resonant frequency higher than the frequency range to remove biases in capacitors present in the inductively coupled power transfer system. Operating the converter
How to further include. The method of claim 2, wherein the non-resonant frequency is 1 to 10 MHz. The method of claim 1,
Ignoring peak amplitudes below a threshold while determining the peak amplitude of the current during the inrush period for each of the plurality of frequencies.
How to include. The method of claim 1, wherein the frequency range is 100 to 1,000 kHz. The method of claim 1, wherein analyzing the characteristics of the determined peak amplitudes within the frequency range,
Identifying the maximum;
Determining the identified maximum characteristics including the identified maximum width, the magnitude of the identified maximum peak, or the frequency at which the maximum occurs.
Containing, method. 7. The method of claim 6, wherein the predetermined parameter comprises a frequency at which the identified maximum occurs. 7. The method of claim 6, wherein the maximum has a width and the predetermined parameter comprises the maximum width. The method of claim 8, wherein detecting a receiver based on the characteristic meeting a predetermined parameter comprises detecting the receiver based on a determination whether the identified maximum width spans more than 50 kHz. How to. 7. The method of claim 6, wherein the predetermined parameter comprises the size of the identified largest peak. The method of claim 1,
Depending on the result of detecting the receiver based on the characteristic satisfying a predetermined parameter,
Transmitting wireless power to the receiver,
Identifying whether the receiver is a receiver compatible with the inductively coupled power transmission system,
Switching the transmitter of the system to a standby mode; or
Switching off the transmitter of the system
The method further comprising performing one or more of. As an induction power transmitter,
A coil for generating an alternating magnetic field;
A converter for supplying an alternating current to the coil;
A sensor for measuring the current supplied to the converter; And
Controller
Including, the controller,
Operating the converter at a plurality of frequencies within a frequency range;
During an inflow period for each of the plurality of frequencies, determining a peak amplitude of the current measured using the sensor;
Characterize the determined peak amplitudes within the frequency range;
The inductive power transmitter configured to detect a receiver based on the characteristic meeting a predetermined parameter. The method of claim 12,
The controller is configured to supply an alternating current having a non-resonant frequency higher than the frequency range in order to remove biases from capacitors present in the inductively coupled power transfer system, prior to operating the converter at each of the plurality of frequencies. An inductive power transmitter further configured to operate the converter. 14. The inductive power transmitter of claim 13, wherein the non-resonant frequency is 1 to 10 MHz. The method of claim 12,
Wherein the controller is configured to ignore peak amplitudes that are below a threshold while determining a peak amplitude of the current during the inrush period for each of the plurality of frequencies. 13. The inductive power transmitter of claim 12, wherein the frequency range is 100 to 1,000 kHz. The method of claim 12, wherein analyzing the characteristics of the determined peak amplitudes within the frequency range,
Identifying the maximum;
Determining the identified maximum characteristics including the identified maximum width, the magnitude of the identified maximum peak, or the frequency at which the maximum occurs.
Containing, induction power transmitter. 18. The inductive power transmitter of claim 17, wherein the predetermined parameter is the frequency at which the identified maximum occurs. 18. The inductive power transmitter of claim 17, wherein the maximum has a width and the predetermined parameter comprises the maximum width. The method of claim 19, wherein detecting the receiver based on the characteristic meeting a predetermined parameter comprises detecting the receiver based on a determination of whether the identified maximum width spans more than 50 kHz. Induction power transmitter. 18. The inductive power transmitter of claim 17, wherein the predetermined parameter comprises a magnitude of the identified maximum peak. The method of claim 12, wherein the controller,
Depending on the result of detecting the receiver based on the characteristic meeting a predetermined parameter,
Transmitting wireless power to the receiver,
Identifying whether the receiver is a receiver compatible with an inductively coupled power transmission system including the inductive power transmitter,
Switching the transmitter to a standby mode; or
Switching off the transmitter
Further configured to perform one or more of the inductive power transmitter.

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