Q factor detection method

Abstract

Embodiments of the present disclosure relate to a Q-factor detection method. The present invention provides a wireless transmitter with Q-factor measurement. In some embodiments, a method for performing a measurement test in a wireless power transmitter includes: adjusting an input voltage to a bridge circuit; setting transistors in the wireless power transmitter to form an LC oscillating circuit including a transmitting coil and a capacitor circuit; and measuring a sinusoidal voltage V from the LC oscillating circuit. DET ; and according to the sinusoidal voltage V DET Determine a result. The result may be a calculation result of a Q factor and / or determine the presence of foreign matter.

Description

Technical Field

[0001] Embodiments of the present invention relate to a wireless power system, and in particular, to a quality factor (Q-factor) determination method. Background Art

[0002] Typically, a wireless power system includes a transmitter coil, which is driven to generate a time-varying magnetic field, and a receiver coil, which is positioned relative to the transmitter coil to receive the power transmitted in the time-varying magnetic field. One measure of system efficiency is to measure the quality factor (Q factor) of the resonant circuit that includes the transmitter coil. Generally, in a resonant circuit, the Q factor can be defined as a dimensionless quality factor that is related to the ratio of the energy stored in the circuit to the amount of energy dissipated from the circuit per cycle. The resonant circuit in a transmitter typically includes a transmitter coil coupled in series with a capacitor, a series circuit coupled across a driving voltage.

[0003] There are several reasons for determining the Q factor of a resonant circuit in a wireless power system. The resonant circuit is affected by the receiver system and foreign objects within the field range of the generated electromagnetic field. Therefore, monitoring the Q factor of the transmitter resonant circuit can be used as an indicator of the presence of foreign objects. Furthermore, monitoring the Q factor can aid in operation because it is a function of the resonant frequency, so the Q factor can help determine the resonant frequency. Furthermore, the Q factor can be used to facilitate communication methods.

[0004] In an important aspect, the Q factor can be used to determine the presence of foreign objects (FO). As the power levels of transmitted wireless power become higher, safety becomes an increasingly important factor. FO objects can heat to dangerous levels in the presence of time-varying magnetic fields. Measuring the Q factor allows the presence of FO to be determined before entering the power transfer phase.

[0005] Current methods for measuring the Q factor in wireless power transmitters can be complex. Therefore, there is a need to better determine the Q factor in wireless systems. Summary of the Invention

[0006] According to some embodiments of the present invention, a wireless power transmitter with Q-factor measurement is provided. The wireless power transmitter according to some embodiments includes: a transmit coil coupled between a first node and a second node; a half-bridge circuit coupled between an input voltage and ground, the half-bridge circuit coupled to the first node; a capacitor circuit having a plurality of capacitors coupled to the transmit coil; a measurement circuit coupled to the capacitor circuit and to the transmit coil; and a transmit driver coupled to the measurement circuit and the half-bridge circuit. During a measurement test, the transmit driver configures the half-bridge circuit to form an LC oscillating circuit with the transmit coil and the capacitor circuit, monitors a sinusoidal voltage in the LC oscillating circuit, and determines a result based on the sinusoidal curve. The result can be a calculation of the Q-factor and / or a determination of the presence of a foreign object.

[0007] In some embodiments, a method for performing a measurement test in a wireless power transmitter includes: adjusting an input voltage to a bridge circuit; setting transistors in the wireless power transmitter to form an LC oscillating circuit including a transmitting coil and a capacitor circuit; and measuring a sinusoidal voltage V from the LC oscillating circuit. DET ; and according to V DET The sinusoidal voltage determines the result.

[0008] These and other embodiments are discussed further below in conjunction with the following figures. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1A A wireless power transfer system is illustrated.

[0010] Figure 1B The determination of the Q factor is illustrated.

[0011] Figure 2 A transmitter circuit is illustrated that is configured to measure the Q factor using a conventional Q factor measurement method.

[0012] Figure 3A and Figure 3B The Q-factor determination by frequency sweep is illustrated.

[0013] Figure 4A and Figure 4B The Q factor determination by ringing attenuation is illustrated.

[0014] Figure 5A 、 Figure 5B and Figure 5C Illustrated is the measurement of the Q factor in a transmitter according to some embodiments.

[0015] Figure 6 Pictured Figure 5A 、 Figure 5B and Figure 5C Examples of measurements shown.

[0016] Figure 7A and Figure 7B Pictured Figure 5A 、 Figure 5B and Figure 5C Another embodiment of the measurement is shown. DETAILED DESCRIPTION

[0017] In the following description, the specific details of some embodiments of the present invention are set forth. However, it will be apparent to those skilled in the art that the present invention may be practiced without some or all of these specific details. The specific embodiments disclosed herein are intended to be illustrative, not restrictive. Those skilled in the art will appreciate that, although not specifically described herein, other elements are also within the scope and spirit of this disclosure.

[0018] The description and drawings, which illustrate aspects and embodiments of the invention, should not be construed as limiting—the claims define the protected invention. Various changes may be made without departing from the spirit and scope of the description and claims. In some cases, well-known structures and techniques are not shown or described in detail so as not to obscure the present invention.

[0019] Whenever practicable, elements and their associated aspects described in detail with reference to one embodiment may be included in other embodiments that do not specifically show or describe them. For example, if an element is described in detail with reference to one embodiment, but not described with reference to a second embodiment, the element may still be considered to be included in the second embodiment.

[0020] Figure 1A A system 100 for wireless power transfer is shown. Figure 1A As shown, wireless power transmitter 102 drives coil 106 to generate a magnetic field. Power supply 104 powers wireless power transmitter 102. For example, power supply 104 can be a battery-based power supply or can be powered by alternating current (e.g., a standard 50 Hz, 240 V power supply). Wireless power transmitter 102 typically drives coil 106 within a certain frequency range, typically in accordance with one of the wireless power standards. However, this can be applied to any frequency, regardless of any existing standards, as long as it is feasible to transmit power and / or information using magnetic coils.

[0021] There are several standards for wireless power transfer, including the Alliance for Wireless Power (A4WP) and the Wireless Power Consortium (Qi). Under the A4WP standard, for example, up to 50 watts of power can be inductively transferred to multiple charging devices near coil 106 at a power transfer frequency of approximately 6.78 MHz. Under the Qi specification of the Wireless Power Consortium (WPC), a resonant inductive coupling system is used to charge a single device at the device's resonant frequency. In the Qi standard, coil 108 is placed near coil 106, while in the A4WP standard, coil 108 is placed near coil 106 along with other coils belonging to other charging devices. Figure 1A A generic wireless power system 100 operating under any of these standards is depicted. In Europe, the switching frequency has been limited to 148 kHz.

[0022] like Figure 1A As further shown, the magnetic field generated by coil 106 induces a current in coil 108, which causes power to be received in receiver 110. Receiver 110 receives power from coil 108 and provides the power to load 112, which may be a battery charger or other component of a mobile device. Receiver 110 typically includes rectification to convert the received AC power into DC power for load 112.

[0023] Figure 1B The wireless power transmitter 102 is depicted in further detail. In many cases, the transmit coil 106 is coupled in series with the capacitor 114 across a full bridge driver formed by transistors 116, 118, 120, and 122. Figure 1B As shown, transistors 116 and 118 are coupled in series at an input voltage V in and ground. Transistors 120 and 122 are also coupled in series at the input voltage V in and ground. Transistor coil 106 is coupled between node 130 between transistors 116 and 118 and node 132 between transistors 120 and 122. Current can be driven through the transmit coil by alternately turning on transistors 116 and 122 while turning off transistors 120 and 118, and turning on transistors 120 and 118 while turning off transistors 116 and 122. In some embodiments, the transmit coil can be driven in a half-bridge manner by turning off transistor 120, turning on transistor 122, and alternately turning on transistors 116 and 118.

[0024] Although Figure 1B A wireless power transmitter 102 is shown with a simple resonant circuit comprising a transmit coil 106 and a capacitor 114 coupled in series, but other more complex transmit coil technologies may be used. In some cases, a multi-coil transmit coil may be used, such as, for example, an A13 coil topology. However, for simplicity purposes, Figure 1B The resonant circuit shown is beneficial.

[0025] Transistors 116, 118, 120, and 122 are driven by emitter driver 126. Emitter driver 126 may be a single integrated circuit that generates gate voltages GA, GB, GC, and GD for driver transistors 116, 118, 120, and 122, respectively. Figure 1B As shown, measurement circuit 124 can be coupled to receive a signal from node 128 between transmit coil 106 and capacitor 114, as well as signals from nodes 130 and 132. In some embodiments, measurement circuit 124 can provide signals to transmit driver 126, which can itself determine the Q factor. Driver 126 can drive transmit coil 106 at a specific frequency (e.g., a resonant frequency determined by modifying the drive frequency to maximize the Q factor). Further, measurement circuit 124 can provide signals to transmitter driver 126 to control the states of transistors 116, 118, 120, and 122 during testing.

[0026] The Q factor can be determined as the voltage of the transmitting coil 106 and the input voltage V in In some embodiments, the Q factor can be determined by approximately measuring the amplitude of the AC signal across transmit coil 106 (i.e., between node 130 and node 128), which can be used to detect the presence of foreign objects. In some examples, transmit driver 126 can monitor the Q factor to detect the presence of foreign objects.

[0027] The transmitter driver 126 may include a microcontroller, a microprocessor, a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), etc. The transmitter driver 126 further includes sufficient volatile and non-volatile memory to store data and firmware instructions to perform the tasks described in this disclosure. The transmitter driver 126 further includes interfaces and other circuit systems to allow the transmission of data, power, and other signals.

[0028] The Q factor can be important for foreign object (FO) detection (FOD) in wireless power systems. In many applications (such as automotive applications), FOD detection becomes an important aspect of wireless power transmission. Foreign objects (such as Figure 1A The presence of foreign matter 140 (shown) can cause multiple problems, including a reduction in the Q factor, which indicates insufficient wireless power transfer efficiency. Furthermore, foreign matter 140 may be heated during wireless power transfer, resulting in the risk of fire or other damage.

[0029] Several techniques can be used to measure the Q factor, including frequency sweep methods and ringing decay methods. The ringing decay method is the subject of a previously filed U.S. application (serial number 15 / 998,784), which is incorporated herein by reference in its entirety. However, each of these methods has disadvantages, as discussed further below. Embodiments of the present invention overcome many of these disadvantages.

[0030] Figure 2 Pictured Figure 1B Another depiction of the transmitter 102 is shown. In particular, Figure 2 A configuration is shown that includes transistors 116 and 118 driving the series-coupled transmit coil 106 and capacitor 114 according to a transmit driver 126. In some cases, if the wireless power transmitter 102 uses a half-bridge drive arrangement, transistor 122 may be replaced with a connection from capacitor 114 to ground, and transistor 120 may not be present. In some cases, the configuration is formed by turning on transistor 122 and turning off transistor 120. Further, Figure 2 A resistor 202 is shown, which may be the resistance of the transmitter coil 106. Measurement according to the frequency sweep method or the ringing decay method measures the Q factor by measuring the voltage V0 at the node 128 between the transmitter coil 106 and the capacitor 114.

[0031] Figure 3A and Figure 3B The diagram shows Figure 2 During the measurement, transistors 116 and 118 generate pulses whose frequency varies across a certain frequency range. For example, the frequency can vary within a range of about 100 kHz. Figure 1B As shown, measurement circuit 124 measures the voltage across inductor 106 , which is voltage V 0 at node 128 .

[0032] Figure 3A A measurement circuit 124 is shown which is adapted to measure the voltage V0 at the node 128 during a frequency sweep within the frequency range discussed above. Figure 3A As shown, the voltage V0 at node 128 is input to a differential amplifier 304 followed by a diode 306. The signal is then filtered using a resistor 308 and a capacitor 310 to provide an output voltage V coil In some embodiments, a frequency sweep can be performed by stepping transistors 116 and 118 over a frequency range with measurements taken at each stepped frequency in the process. The frequency sweep can be controlled by a transmitter driver 126. The data generated by the measurement circuit 124 can be input to the transmit driver 126, which processes the data to determine the quality factor Q.

[0033] Figure 3B The output voltage V from the measurement circuit 124 is shown as a function of frequency. coil As shown in the figure, the maximum Q factor is shown as the peak value V occurring at the frequency ω0. peak The bandwidth BW can be defined by the width of the curve at the 3dB attenuation point. The 3dB attenuation point is 0.707*V peak Appears at frequency ω －1 and ω1. Therefore, if Figure 3B As shown, BW=ω1-ω －1 =2*(ω1-ω0). In one calculation, the quality factor Q can then be given by Q=ω0 / BW. Alternatively, the quality factor Q can also be calculated based on the low frequency (ie DC) voltage V0, Q=V peak / V0.

[0034] This technique for determining Q has several advantages. First, the measurement circuit 124 is easy to design. The filter formed by resistor 208, resistance R and capacitor 210, capacitance C is relatively easy to design. However, in practical applications, it is difficult to locate the peak voltage V peak It is very difficult. peak Small differences in ω0 can lead to large differences in gain and, thus, in the calculation of the Q factor Q. Furthermore, calculating the Q factor Q using this data typically takes a very long time.

[0035] Furthermore, the measurement according to the frequency sweep technique depends on the input voltage V during the measurement. in Stability. Input voltage V in The instability of the Q factor may lead to large errors in the calculation of the obtained Q factor.

[0036] Furthermore, when the frequency is at or near ω0, the current through transistors 116 and 118 may be high, which may cause the input ripple of the measurement circuit 124 to be large, thereby causing large measurement errors. Furthermore, large currents require a good bridge power supply. Generally, reducing the input voltage V in , to reduce the current. However, a small input voltage V in Also, the pulses used during this technique can contain many harmonics, which can also affect the accuracy of the results.

[0037] Furthermore, to mitigate at least some of these issues, the firmware design for processing the data that may appear in transmitter driver 126 becomes significantly more complex. Furthermore, since operation at bandwidths greater than 20 MHz is possible, the cost of the processing circuitry becomes even higher. All of these issues can lead to measurement instability even when implemented on the same board. Distributing the circuitry across multiple boards can increase instability.

[0038] A ringing attenuation method is provided, the method comprising: Figure 2 The capacitor 114 in the illustrated LC tank circuit (resonant circuit) comprising the series-coupled transmit coil 106 and capacitor 114 is charged to a charging voltage and the resonant circuit is initiated in a free-running manner. The voltage at node 128 can be measured in a free-running manner, and the resonant frequency and Q factor can be determined from this data. No frequency sweep or large database is required. Compared to frequency sweep methods, data can be acquired more quickly, and analysis can be completed more accurately and more quickly than provided by frequency sweep techniques.

[0039] Figure 4A and Figure 4B The diagram illustrates the determination of the Q factor by ringing attenuation. Figure 4A A measurement circuit 124 suitable for measuring ringing attenuation is shown. For example, the output from the measurement circuit 124 can be input to the transmit driver 126, which processes the data to determine the Q factor. As described above, the process begins when the transmitter driver 126 turns on transistor 116 and turns off transistor 118, charging capacitor 114. At time t=0, transistor 116 is turned off, transistor 118 is turned on, and the LC tank circuit is allowed to oscillate. The data from the measurement circuit 124 is processed.

[0040] like Figure 4A As shown, the measurement circuit 124 receives the voltage V(t) at node 128 into the diode 402. A filter 404 comprising capacitors 406 and 412 and resistors 408 and 410 is then provided. The output V coil (t) is the time-varying voltage generated by the oscillating voltage from the LC circuit formed by the transmitting coil 106 and the capacitor 114.

[0041] Figure 4B The voltage V when the LC circuit is formed by the transmitting coil 106 and the capacitor 114 is shown. coil (t). At time t=0, the voltage V coil (t) is designated as U0. The time-varying waveform 420 is typically modeled as a linear homogeneous differential order equation, which typically has the following solution

[0042]

[0043] Among them, U0 is at time t=t0V coil The voltage at (t0), is the phase constant during free oscillation, ω is the resonant frequency 2πf0, Q is the quality factor of the resonant circuit, and t is the time. In most cases, Q is large enough so that V coil The value of (t) becomes

[0044]

[0045] Therefore, the resonant frequency f0 can be directly determined by the time between consecutive oscillations of the exponentially decaying cosine function of waveform 422.

[0046] like Figure 4B As further shown, the amplitude envelope is 422V env (t) is an exponential decay, which, as mentioned above, is given by

[0047]

[0048] Therefore, since the resonant frequency f0 is known and therefore the frequency ω is also known, the Q factor Q can be determined based on the exponential decay curve (or envelope curve) 420. In particular, one method of determining Q is to take a time t1 after time t0 and determine the envelope value V at time t1. env (t1), and determine the value of Q, according to the above equation for V env The Q value of (t) is given by

[0049]

[0050] Thus, the Q factor can be calculated by measuring the initial voltage when capacitor 114 is fully charged at time t0, when the LC circuit begins to oscillate. Then, a second measurement of the envelope voltage is taken at time t1, after time t0. The Q factor can then be calculated as described above.

[0051] The ringing attenuation method results in a more stable measurement. The measurement is performed in a very short time (e.g. about 1ms). The measurement does not depend on the input voltage V in Therefore, the stability of input voltage Vin or high current, which can be a problem in frequency sweep measurements, is no longer an issue. Furthermore, measurement circuit 124 is relatively simple and low-cost. The firmware executed in transmit driver 126 can be relatively simple. With acceptable performance, components can be distributed across different boards. This method is insensitive to temperature. The circuit can also be used with frequency sweep methods, enabling a variety of measurement techniques.

[0052] However, the ringing attenuation method also has some disadvantages. Among them, the RC filter 404 must be carefully tuned. There is a trade-off between accurate measurement of large foreign objects (FO) and stable readings. If the RC constant of the filter 404 is large, the result is very stable. However, in the case of large FO, the quality factor Q will be larger. Fortunately, the filter 404 can be designed to ensure stable readings and accuracy at the same time in the case of smaller FO. Further, if the printed circuit board (PCB) including the wireless transmitter is poorly laid out, the Q may be very small, and the difference between the receiver and the small FO may also be small, making them difficult to distinguish. Additionally, as described above, although the firmware can be relatively simple, the calculation itself is complex and may be difficult to accurately implement in the transmitter driver 126.

[0053] Furthermore, while the ringing attenuation method is well suited for Figure 2 A system with a single transmit coil is shown, but this system does not work well with systems using the MP-A13 coil topology. The MP-A13 topology utilizes a three-coil array package commonly used for wireless power systems to provide the transmit coil. The MP-A13 coil topology introduces high-frequency ringing due to the two additional inductors (e.g., 1 μH) and capacitors (e.g., 400 nF). This high-frequency ringing introduces test errors that can affect the Q factor calculation in this configuration.

[0054] Figure 5A An example implementation of a wireless power transmitter 500 with Q-factor measurement according to some embodiments is illustrated. Figure 5A As shown, the transmitter 500 includes a full bridge driver formed by transistors 504, 506 and 508. As shown, transistors 502 and 504 are coupled in series at an input voltage V in and ground. Transistors 506 and 508 are also coupled in series at the input voltage V in The gates of transistors 502 , 504 , 506 , and 508 ( GA , GB , GC , and GD , respectively) are driven by emitter driver 510 .

[0055] Node 528 between transistor 502 and transistor 504 is coupled to inductor 512, while node 530 between transistors 506 and 508 is coupled to inductor 514. Capacitor 516 is coupled between inductors 512 and 514 opposite nodes 528 and 530. Inductors 512 and 514 and capacitor 516 are optional and depend on the specific coil configuration used for wireless power transmission coil 520. In particular, Figure 5A The example configuration shown is beneficial for the MP-A13 coil topology. Other coil topologies may be used.

[0056] Transmit coil 520, in series with resistor 518, is coupled across capacitor 516 (i.e., between nodes 528 and 530). Further, capacitor 517 may be coupled between node 528 and transmit coil 520. As described above, in the example where transmit coil 520 is an MP-A13 coil topology, inductors 512 and 514 are 1 μH inductors, and capacitor 516 is a 400 nF capacitor. Figure 5A In the embodiment shown, capacitors 522 and 524, which are coupled in series, are also coupled across capacitor 516. Capacitors 522 and 524 form a capacitive voltage divider that can be removed if capacitors 516 and 517 are present. For example, when capacitors 522 and 524 are not present, node 544 can be moved to node 549 between capacitors 516 and 517.

[0057] exist Figure 5A In the example shown, transmitter driver 510 can be formed on an integrated circuit and coupled to drive the gates of transistors 502, 504, 506, and 508. Transmitter driver 510 can include a processor 532 coupled to a memory 534. Processor 532 can be any microcontroller, microprocessor, or other processing device capable of performing functions associated with controlling the wireless power transmitted by a wireless power transmitter and performing the functions described herein. As a specific example, the transmitter driver can be the P9261 wireless power transmitter chip sold by Renesas, in which processor 532 is a 32-bit ARM processor. Memory 534 can be a combination of volatile and non-volatile memory structures for storing data and firmware programming instructions for processor 532. Processor 532 executes the instructions stored in memory 534 to control the operation of wireless power transmitter 500. In some embodiments, processor circuit 532 can be coupled to interface pins on the integrated circuit via interface circuitry, through which firmware stored in memory 534 can be loaded or updated, or other communications can be performed with transmit driver 510.

[0058] like Figure 5A As further shown, processor 523 is coupled to half-bridge drivers 536 and 538, which may be PWM generators for providing gate signals GA, GB, GC, and GD, respectively, to transistors 502, 504, 506, and 508. In some embodiments, half-bridge drivers 536 and 538 may be operated such that transistors 502 and 504 are driven in a half-bridge mode and transistors 506 and 508 are configured to keep transistor 508 turned on and transistor 506 turned off, thereby configuring node 530 to be grounded.

[0059] Thus, the transmit driver 510 may further be capable of interfacing with a multi-coil configuration, such as the MP-A13 coil topology discussed above. Thus, the processor 532 may be coupled to the coil select driver 542 to select a particular coil configuration for the coil topology. Figure 5A , the transmit coil 520 may include a multi-coil transmit topology and a switch coupled to receive a signal from a coil select driver 542 to select a particular configuration.

[0060] The transmit driver 510 further includes an analog-to-digital converter 540 that can receive an input signal and provide a corresponding digitized signal to the processor 532. The ADC 540 can include a multiplexer and an ADC for receiving and processing analog signals. Figure 5A As discussed further below, ADC 540 may receive a voltage signal V DET and the current signal I DET .

[0061] According to an embodiment of the present disclosure, a measurement circuit 527 including a bipolar junction transistor (BJT) 526 is illustrated. For simplicity, the bipolar junction transistor is shown as an NPN BJT. In practice, the BJT 526 can be implemented as an operational amplifier. Figure 5A As shown, BJT 526 has a base coupled to node 548, which is grounded to ground node 530 through inductor 514, an emitter coupled to node 544 between capacitor 522 and capacitor 524 (or in the absence of capacitors 522 and 524 coupled to node 549), and a collector coupled to node 546 on the opposite side of capacitor 522 from node 544. The Q factor is then the current I at node 546. DET and the voltage V at node 546 DET The Q factor can be given by

[0062]

[0063] Where ω is the frequency of the signal generated by the Q measurement circuit formed by BJT 526, and C is the capacitance provided by the capacitive divider (capacitors 522 and 524) and resonant caps 516 (if present) and 517. For ease of measurement, an operational amplifier can be used in place of BJT 526. In this case, I DET reaches a known limit, and therefore Q L By measuring V DET To confirm. DET and I DET The value of is the amplitude of the fundamental frequency component signal.

[0064] Figure 5BThe operation of transmitter 500 according to some embodiments is illustrated to provide measurement 560. One of ordinary skill in the art will recognize that measurement 560 may be modified for a specific configuration of transmitter 500 that is customized for a specific coil configuration. However, measurement 560 or a modified measurement 560 may be used to make measurements according to some embodiments of the present disclosure.

[0065] Measurement 560 begins at step 562. In step 562, Vin is set to a level such that the body diodes of transistors 502, 504, 506, and 508 do not conduct. In some systems, V in is set to 5V or higher. In setup step 564, transistors 502, 504, 506, and 508 are set to perform the measurement. In some embodiments, other transistors may also be fixed. Figure 5A In the example shown, transistors 502, 504, 506, and 508 are set to off and transistor 508 is set to on. In some embodiments, the bridge transistors 502, 504, 506, and 508 are also set. For example, in some embodiments, transistor 508 may also remain off. In step 566, the measurement circuit 527 involving the BJT 526 shown in the figure is enabled. Figure 5A In the configuration shown, with transistors 502, 504 and 506 off, transistor 508 on and measurement circuit 527 enabled, an LC oscillator is formed using transmitting coil 520 and capacitance formed by capacitors 522, 524, 516 and 517 as described above.

[0066] In step 568, while the LC circuit is oscillating, V DET The value of the sinusoidal signal generated in the LC circuit is V DET The amplitude is very sensitive to the presence of foreign matter. Therefore, in some embodiments, method 560 proceeds to step 572, where the presence of foreign matter is directly determined by V DET The amplitude measurement and other characteristics of the generated sinusoidal signal are determined. In some embodiments, method 560 proceeds to step 570 to accurately calculate the Q value for later use. The calculated Q value can also be used to determine the presence of foreign objects or can be used for other purposes in wireless power transmitter 500.

[0067] Figure 5C The figure shows V under specific conditions DET Sine waveform. Waveform 550 illustrates the V in transmitter 500 when there is no foreign object (FO) and receiver circuitry near transmitter coil 520. DET Waveform. V DET Waveform 552 illustrates the V in transmitter 500 with FO near transmit coil 520. DETWaveform. V DET Waveform 554 illustrates the V in transmitter 500 when there is a receiver near transmitter coil 520. DET Waveform. Figure 5B As shown, V DET The waveform is a sinusoidal waveform having a specific frequency ω. In particular, comparing waveform 550 (without a receiver or FO) with waveform 552 (with FO), it is seen that the frequency ω remains the same, but the amplitude of waveform 552 is reduced compared to waveform 550. Comparing waveform 550 with waveform 554 (with a receiver), it is seen that the frequency of waveform 554 is shifted and the amplitude of waveform 554 is reduced. Figure 5B As shown, the stable results are illustrated in the case where the FO and the presence of the receiver can be detected.

[0068] Therefore, V DET The sinusoidal waveform can be analyzed in the transmit driver 510 to determine the Q factor or to determine the presence of foreign matter. In particular, V DET The shift of the sine wave (ie V DET Measurements of amplitude and / or frequency ω) can be used to determine the presence of foreign matter.

[0069] Figure 6 An embodiment of a measurement system in a wireless transmitter 600 is illustrated. In the wireless transmitter 600, the capacitor 516 includes four parallel capacitors 602, 604, 606, and 608. The transmit coil 520 is illustrated by an MP-A13 coil configuration 610 coupled to switches 612, 614, and 616. The transmit driver 510 drives the coil select 542 to drive a particular coil configuration indicated by the processor 532. Capacitors 618 and 620 are coupled in parallel between the MP-A13 coil configuration 610 and the inductor 512. The transmitter 600 further includes V coil Measuring circuit 622. Figure 6 As further shown, the coil select signal from transmit driver 510 controls the operation of switches 612 , 614 , and 616 . Figure 6 The transmit driver 510 is shown inputting V measured by the detector circuit 630. DET Signal.

[0070] Detector circuit 630 includes a circuit configured to generate V from node 633. DET As shown, amplifier 624 receives the voltage-divided signal at node 636 and the voltage-divided signal between the output signal from amplifier 624 and the voltage at node 638. The voltage at node 636 is V inNode 638 is a resistor-divided signal from a capacitor voltage divider 640, which is coupled between the transmitter coil 610 and node 633. In this example, BJT 626 is a PNP junction transistor 626, where the emitter is coupled to the input voltage V in , the collector is coupled to the transmit coil 610, and the base is coupled to the base from the amplifier 624. Thus, the voltage at node 636 provides a low noise DC reference for the op amp 624 and BJT 626 to maintain proper biasing. Thus, the collector of the BJT 626 provides V which can be analyzed by the transmit driver 510 as described above. DET Sinusoidal signal. Figure 6 During the measurement test of the system shown, transistors 502 and 506 are turned off and transistors 504 and 508 are set (eg, on or off) during step 564. This is arranged for an LC oscillator having a transmitting coil 610 and capacitors 618 and 620 and optionally capacitor 516.

[0071] Further, Figure 6 The operation of transmitter 600 is particularly illustrated, wherein the transmitting coil 610 is an MP-A13 coil configuration. However, the embodiments can be applied to wireless power transmitters having any other coil configuration, such as an MP-A11 coil configuration or any other coil configuration that may be included.

[0072] The proposed measurement system has improved stability. Furthermore, the measurement time (i.e., the operating time in half-bridge mode) is acceptable in most cases. In many embodiments, measurements according to some embodiments of the present invention can be completed in approximately 10 ms. Furthermore, filter design and calculations are relatively simple. Furthermore, components can be distributed across different boards. As shown, the system can stably identify various FO and RX signals, particularly when operating with the MP-A13 coil configuration. However, the circuit cost can be high, and the specifications of the various components can also be high.

[0073] The following table provides a comparison of this oscillator technique, the frequency sweep technique, and the ringing reduction technique. As can be seen in the table, the current system has advantages and disadvantages compared to the other techniques. However, when using the MP-A13 coil configuration or a configuration similar to the MP-A13, the oscillator technique according to the embodiments described in this disclosure can be an overall superior solution for determining Q factor and detecting FO or receiver.

[0074]

[0075]

[0076] As described above, it is expected that embodiments of the present invention are advantageous in terms of stability, design difficulty, measurement error, firmware complexity, FO / RX identification, and measurement time. However, cost and PCB size may not be advantageous. Furthermore, distribution and temperature effects may or may not be advantageous.

[0077] Figure 7A and Figure 7B A high power wireless power transmitter 700 is shown. Figure 7A As shown, transmit coil 702 is a high-power coil configuration, which may be an MP-A13 coil configuration, coupled to coil switches 612, 614, and 616. However, capacitors 618 and 620 are replaced by capacitors 704, 706, and 708, which are switched using coil switches 612, 614, and 616 having transistors 710, 712, and 714, respectively. In some embodiments, transmit coil 702 may include a comb filter 716 for filtering signals passing through each of the three coils included in transmit coil 702.

[0078] Figure 7B 1 illustrates an implementation of the measurement circuit 630 for a high power wireless power transmitter 700. Figure 7B As shown, in this implementation, a capacitive voltage divider 640 is coupled between nodes 632 and 634, rather than Figure 6 The illustrated implementation illustrates coupling between the transmit coil 701 and the node 632. Further, in a setup step 564 of the method 560, transistors 710, 712, and 714 are turned on.

[0079] The above detailed description is provided to illustrate specific embodiments of the present invention and is not intended to be limiting. Many changes and modifications are possible within the scope of the present invention. The present invention is set forth in the appended claims.

Claims

1. A wireless power transmitter, comprising: a transmitting coil coupled between the first node and the second node; a first half-bridge circuit coupled between an input voltage and a ground, the first half-bridge circuit comprising a first transistor and a second transistor, the first transistor coupled between the input voltage and the first node, the second transistor coupled between the first node and the ground; a second half-bridge circuit coupled between the input voltage and ground, the second half-bridge circuit comprising a third transistor and a fourth transistor, the third transistor coupled between the input voltage and the second node, the fourth transistor coupled between the second node and the ground; a capacitor circuit having a plurality of capacitors coupled between the first node and the second node; a measurement circuit coupled to the capacitor circuit and the first node; as well as a transmit driver coupled to provide control signals to the measurement circuit, the first half-bridge circuit, and the second half-bridge circuit, wherein, during a measurement test, the transmit driver configures the first half-bridge circuit to turn on the first transistor and turn off the second transistor, configures the second half-bridge circuit to turn off the third transistor and turn on the fourth transistor, and enables the measurement circuit to form an LC oscillating circuit between the input voltage and ground, the LC oscillating circuit including the transmit coil and the plurality of capacitors in the capacitor circuit, monitors a sinusoidal voltage across the transmit coil in the LC oscillating circuit, and determines a Q factor based on a voltage amplitude across the transmit coil, and Wherein the capacitor circuit includes a capacitive voltage divider formed in the capacitor circuit, and the measurement circuit includes a bipolar junction transistor (BJT) coupled to the capacitive voltage divider. 2 . The transmitter of claim 1 , wherein the Q factor is calculated based on the voltage magnitude at the first node and the current magnitude at the first node determined by the transmit driver.

3. The transmitter of claim 1, wherein the Q factor is used as an indicator of the presence of foreign matter. 4 . The transmitter of claim 1 , wherein the second half-bridge circuit is coupled to the second node through an inductor. The transmitter of claim 1 , wherein the transmitting coil is a configurable multi-coil system. The transmitter of claim 1 , wherein the transmit coil is configured for high power operation.

7. The transmitter of claim 1 , wherein the transmit driver comprises: a bridge driver having a first driver coupled to the first half-bridge and a second driver coupled to the second half-bridge; an analog-to-digital converter coupled to receive the analog signal and provide a digital signal; as well as a processor coupled to the bridge driver and to the analog-to-digital converter, the processor executing instructions to: adjusting the input voltage; configuring the first transistor and the second transistor of the first half-bridge circuit for the measurement test; configuring the third transistor and the fourth transistor of the second half-bridge circuit for the measurement test; enabling the measurement circuit; receiving the sinusoidal voltage during the measurement test; as well as The voltage amplitude is provided based on the sinusoidal voltage.

8. A wireless power transmitter, comprising: a transmitting coil coupled between the first node and the second node; a first half-bridge circuit coupled between an input voltage and a ground, the first half-bridge circuit comprising a first transistor and a second transistor, the first transistor coupled between the input voltage and the first node, the second transistor coupled between the first node and the ground; a second half-bridge circuit coupled between the input voltage and ground, the second half-bridge circuit comprising a third transistor and a fourth transistor, the third transistor coupled between the input voltage and the second node, the fourth transistor coupled between the second node and the ground; a capacitor circuit having a plurality of capacitors coupled between the first node and the second node; a measurement circuit coupled to the capacitor circuit and the first node; as well as a transmit driver coupled to provide control signals to the measurement circuit, the first half-bridge circuit, and the second half-bridge circuit, wherein during a measurement test, the transmit driver configures the first half-bridge circuit to turn on the first transistor and turn off the second transistor, configures the second half-bridge circuit to turn off the third transistor and turn on the fourth transistor, and enables the measurement circuit to form an LC oscillating circuit between the input voltage and ground, the LC oscillating circuit including the transmit coil and the plurality of capacitors in the capacitor circuit, monitors a sinusoidal voltage across the transmit coil in the LC oscillating circuit, and determines a Q factor based on a voltage amplitude across the transmit coil, and Wherein the capacitor circuit includes a capacitive voltage divider formed in the capacitor circuit, and the measurement circuit includes an amplifier coupled to the capacitive voltage divider.

9. The transmitter of claim 8, wherein the Q factor is calculated based on the voltage magnitude at the first node and the current magnitude at the first node determined by the transmit driver.

10. The transmitter of claim 8, wherein the Q factor is used as an indicator of the presence of foreign matter.

11. The transmitter of claim 8, wherein the second half-bridge circuit is coupled to the second node through an inductor.

12. The transmitter of claim 8, wherein the transmit coil is a configurable multi-coil system.

13. The transmitter of claim 8, wherein the transmit coil is configured for high power operation.

14. The transmitter of claim 8, wherein the transmit driver comprises: a bridge driver having a first driver coupled to the first half-bridge and a second driver coupled to the second half-bridge; an analog-to-digital converter coupled to receive the analog signal and provide a digital signal; as well as a processor coupled to the bridge driver and to the analog-to-digital converter, the processor executing instructions to: adjusting the input voltage; configuring the first transistor and the second transistor of the first half-bridge circuit for the measurement test; configuring the third transistor and the fourth transistor of the second half-bridge circuit for the measurement test; enabling the measurement circuit; receiving the sinusoidal voltage during the measurement test; as well as The voltage amplitude is provided based on the sinusoidal voltage.

15. A method for performing a measurement test in a wireless power transmitter, comprising: regulating an input voltage to a bridge circuit, the bridge circuit comprising a first half-bridge having a first transistor coupled between the input voltage and a first node and a second transistor coupled between the first node and ground, and a second half-bridge having a third transistor coupled between the input voltage and a second node and a fourth transistor coupled between the second node and ground; configuring the bridge circuit to form an LC oscillating circuit between the first node and the second node by turning off the second transistor and the third transistor and turning on the first transistor and the fourth transistor, the LC oscillating circuit including a transmitting coil and a capacitor circuit; enabling a measurement circuit coupled to the transmit coil and the capacitor circuit; When the measurement circuit is enabled, the sinusoidal voltage V across the transmitting coil in the LC oscillating circuit is measured. DET the magnitude of According to the sinusoidal voltage V DET The magnitude determines the Q factor, A capacitive voltage divider is formed in the capacitor circuit, and wherein the sinusoidal voltage V DET The magnitude includes providing a bipolar junction transistor (BJT) coupled to the capacitive voltage divider. The method of claim 15 , wherein the transmitting coil is driven by the first half-bridge during power transfer. 17 . The method of claim 15 , wherein during power transfer the transmitting coil is driven by a bridge circuit formed by the first half-bridge and the second half-bridge.

18. The method of claim 15, wherein the Q factor is used as an indicator of the presence of foreign matter.

19. The method of claim 15, wherein adjusting the input voltage to the bridge circuit comprises: The input voltage is set to a level that prevents conduction through internal diodes of transistors in the bridge circuit during the measurement test.

20. The method of claim 15, wherein the transmitting coil is a configurable multi-coil system, and providing the bridge circuit comprises providing transistors in the bridge circuit and the configurable multi-coil system.

21. The method of claim 15, wherein the transmit coil is configured for high power operation.

22. The method of claim 15, wherein the first node is coupled to the first half-bridge through an inductor.

23. The method of claim 15, wherein the second node is coupled to the second half-bridge through an inductor.

24. A method for performing a measurement test in a wireless power transmitter, comprising: regulating an input voltage to a bridge circuit, the bridge circuit comprising a first half-bridge having a first transistor coupled between the input voltage and a first node and a second transistor coupled between the first node and ground, and a second half-bridge having a third transistor coupled between the input voltage and a second node and a fourth transistor coupled between the second node and ground; Setting the bridge circuit to form an LC oscillating circuit between the first node and the second node by turning off the second transistor and the third transistor and turning on the first transistor and the fourth transistor, the LC oscillating circuit including a transmitting coil and a capacitor circuit; enabling a measurement circuit coupled to the transmit coil and the capacitor circuit; When the measurement circuit is enabled, the sinusoidal voltage V across the transmitting coil in the LC oscillating circuit is measured. DET the magnitude of According to the sinusoidal voltage V DET The magnitude determines the Q factor, A capacitive voltage divider is formed in the capacitor circuit, and wherein the sinusoidal voltage V DET The magnitude is provided by an operational amplifier coupled to the capacitive voltage divider.

25. The method of claim 24, wherein the transmit coil is driven by the first half-bridge during power transfer.

26. The method of claim 24, wherein during power transfer the transmitting coil is driven by a bridge circuit formed by the first half-bridge and the second half-bridge.

27. The method of claim 24, wherein the Q factor is used as an indicator of the presence of foreign matter.

28. The method of claim 24, wherein adjusting the input voltage to the bridge circuit comprises: The input voltage is set to a level that prevents conduction through internal diodes of transistors in the bridge circuit during the measurement test.

29. The method of claim 24, wherein the transmit coil is a configurable multi-coil system, and providing the bridge circuit comprises: The bridge circuit and the transistors in the configurable multi-coil system are provided.

30. The method of claim 24, wherein the transmit coil is configured for high power operation.

Images