CN109143386B

CN109143386B - Metal foreign matter detection method of induction type power supply and power supply module thereof

Info

Publication number: CN109143386B
Application number: CN201810762662.0A
Authority: CN
Inventors: 蔡明球; 詹其哲
Original assignee: Fu Da Tong Technology Co Ltd
Current assignee: Fu Da Tong Technology Co Ltd
Priority date: 2018-04-27
Filing date: 2018-07-12
Publication date: 2020-08-07
Anticipated expiration: 2038-07-12
Also published as: TWI669880B; TW201828568A; CN109143386A

Abstract

The invention discloses a metal foreign matter detection method, which is used for a power supply module of an induction type power supply, wherein the power supply module comprises a power supply coil; measuring a plurality of wave peaks of the coil signal in a plurality of continuous oscillation periods of the coil signal to respectively obtain a plurality of peak trigger voltages; calculating a first attenuation parameter according to a first peak trigger voltage and a second peak trigger voltage in the plurality of peak trigger voltages; and comparing the first attenuation parameter with a first critical value to judge whether metal foreign matters exist in a power transmission range of the induction type power supply.

Description

Metal foreign matter detection method of induction type power supply and power supply module thereof

Technical Field

The present invention relates to a method for detecting metal foreign matter, and more particularly, to a method for detecting metal foreign matter for an inductive power supply.

Background

In the induction type power supply, a power supply end pushes a power supply coil to generate resonance through a driving circuit so as to emit radio frequency electromagnetic waves, and then the coil of a power receiving end receives electromagnetic wave energy and then carries out electrical conversion so as to generate direct current power to be supplied to a power receiving end device. If electromagnetic energy sent by the power supply coil is applied to the metal body, a heating effect can be generated on the metal body, and after heat is accumulated, the metal body is possibly burnt due to high temperature to cause damage. In the prior art, the inductive power supply can periodically interrupt driving during power transmission to detect metal foreign matters, and the detection is judged by measuring the change of the slope. However, the power output by the coil at the power supply end can be adjusted at any time along with the distance between the power supply end and the power receiving end, for example, when the coil is far away, the power output is larger, and when the coil is near, the power output is smaller. As the output power changes, the amplitude of the coil signal also changes, so that the resonance signal attenuates when the coil is interrupted from driving. Therefore, when the power changes, the power supply terminal needs to take several detection cycles to adjust the voltage set by the comparator to track the signal peak. If the coil voltage is unstable due to power or load, it is difficult to determine the attenuation slope by locking the signal peak.

In addition, in order to determine the attenuation slope, the driving signal is interrupted for a certain period of time. However, interrupting the driving signal during the wireless charging process may reduce the overall power output capability, and if the interruption time is too long, the power supply efficiency may be affected, and the driving signal may be reconnected after the interruption time is too long, which may easily generate excessive Electromagnetic Interference (EMI). In the prior art, a comparator module obtains a plurality of peak voltage levels to judge the change of a multi-section slope of coil signal attenuation, so that interruption needs a long time. Taking chinese patent application publication No. CN 106094041 a as an example, it needs 7-15 unequal coil oscillation cycles to complete the measurement of four peak voltage levels to determine the change of the attenuation slope.

In view of the above, it is necessary to provide another method for detecting metal foreign matters, which can complete the detection within a very short time of interrupting the driving, and at the same time avoid the effect of detecting the metal foreign matters due to the power or load variation.

Disclosure of Invention

Therefore, the main objective of the present invention is to provide a method for detecting metallic foreign objects, which can complete the detection within a very short driving interruption time, and can complete the detection within at least 2 to 3 coil oscillation cycles. In addition, the metal foreign matter detection method can judge through the attenuation proportion of the coil signal, and can overcome the defect that the attenuation slope judgment mode in the prior art is easily influenced by the amplitude and the load of the coil.

The invention also discloses a power supply module for the induction type power supply, which is used for executing the metal foreign matter detection method. The resonance capacitor is coupled to the power supply coil and is used for matching with the power supply coil to perform resonance. The at least one power supply driving unit is coupled to the power supply coil and the resonant capacitor, and is used for sending at least one driving signal to the power supply coil so as to drive the power supply coil to generate energy, and interrupting the at least one driving signal in a measurement period so as to stop driving the power supply coil so as to generate a coil signal of the power supply coil. The signal receiving module is coupled to the power supply coil and used for receiving the coil signal of the power supply coil. The processor is coupled to the signal receiving module and used for executing the following steps: measuring a plurality of wave peaks of the coil signal in a plurality of continuous oscillation periods of the coil signal to respectively obtain a plurality of peak trigger voltages; calculating a first attenuation parameter according to a first peak trigger voltage and a second peak trigger voltage in the plurality of peak trigger voltages; and comparing the first attenuation parameter with a first critical value to judge whether metal foreign matters exist in a power transmission range of the induction type power supply.

The invention also discloses a metal foreign body detection method, which is used for a power supply module of an induction type power supply, wherein the power supply module comprises a power supply coil; interrupting at least one driving signal of the inductive power supply in a measuring period to stop driving the power supply coil so as to generate a coil signal of the power supply coil; measuring a first peak of the coil signal in an oscillation period of the coil signal to obtain a first peak trigger voltage; comparing the first peak trigger voltage with the reference voltage value; and when the first peak trigger voltage is equal to or close to the reference voltage value, judging that no metal foreign matter exists in a power transmission range of the induction type power supply.

Drawings

Fig. 1 is a schematic diagram of an inductive power supply according to an embodiment of the invention.

Fig. 2 is a schematic diagram of a metal foreign object detection process according to an embodiment of the invention.

Fig. 3 is a schematic diagram of stopping driving of the power supply coil during a measurement period.

FIGS. 4-7 are schematic diagrams illustrating the peak trigger voltage obtained during a measurement period according to an embodiment of the present invention.

Fig. 8 is a schematic diagram of another metal foreign object detection process according to an embodiment of the invention.

Fig. 9 is a schematic diagram illustrating the determination of the metal foreign object by a peak trigger voltage in a measurement period according to an embodiment of the invention.

Wherein the reference numerals are as follows:

100 induction type power supply

1 Power supply module

10 power supply

111 processor

112 clock generator

113 voltage generating device

114 comparator

120 signal receiving module

121. 122 power supply driving unit

130 voltage dividing circuit

131. 132 voltage dividing resistor

141. 142 resonance capacitor

16 power supply coil

161. 261 magnetic conductor

D1, D2 drive signals

C1 coil signal

2 Power receiving Module

21 load cell

22 capacitance

230 rectification circuit

241. 242 resonant capacitance

26 receiving coil

3 metallic foreign matter

20. 80 metal foreign matter detection process

200 to 222, 800 to 818

CP1 comparison results

A. B, C, D, E, F peak of wave

VB, VC, VD, VE and VF peak trigger voltage

V0_ B, V0_ C, V0_ D, V0_ E, V0_ F triggers the start potential

PAR1 first attenuation parameter

PAR2 second attenuation parameter

PAR3 third attenuation parameter

PAR4 fourth attenuation parameter

TH1 first threshold

TH2 second critical value

TH3 third critical value

Basic threshold of THO

Detailed Description

Referring to fig. 1, fig. 1 is a schematic diagram of an inductive power supply 100 according to an embodiment of the invention, as shown in fig. 1, the inductive power supply 100 includes a power supply module 1 and a power receiving module 2, the power supply module 1 can receive a power from a power supply 10 and output wireless power to the power receiving module 2, the power supply module 1 includes a power supply coil 16 and

resonant capacitors

141 and 142, which are arranged in a structure of C-L-C, wherein the power supply coil 16 can be used to transmit electromagnetic energy to the power receiving module 2 for power supply, the

resonant capacitors

141 and 142 are respectively coupled to two ends of the power supply coil 16 and can be used to cooperate with the power supply coil 16 for resonance when power is supplied, in addition, in the power supply module 1, a magnetic conductor 161 made of a magnetic material can be selectively used to improve the electromagnetic induction capability of the power supply coil 16 and prevent the electromagnetic energy from affecting objects in a non-inductive surface direction of the coil.

In order to control the operations of the power coil 16 and the

resonant capacitors

141, 142, the power supply module 1 further includes a processor 111, a clock generator 112, power

supply driving units

121 and 122, a signal receiving module 120, and a voltage dividing circuit 130. The

power driving units

121 and 122 are coupled to the power coil 16 and the

resonant capacitors

141 and 142, and respectively send driving signals D1 and D2 to the power coil 16, which can receive the control of the processor 111 to drive the power coil 16 to generate and send energy. When both the power

supply driving units

121 and 122 operate simultaneously, full-bridge driving can be performed. In some embodiments, only one of the

power driving units

121 and 122 may be turned on, or only one

power driving unit

121 or 122 may be disposed to perform half-bridge driving. The clock generator 112 is coupled to the

power driving units

121 and 122, and is used for controlling the

power driving units

121 and 122 to send the driving signals D1 and D2. The clock generator 112 may be a Pulse Width Modulation (PWM) generator or other type of clock generator, and is used for outputting a clock signal to the power

supply driving units

121 and 122. The processor 111 may receive information related to the coil signal C1 (i.e., the voltage signal between the power coil 16 and the resonant capacitor 142) on the power coil 16, such as the resonant frequency or the attenuation amplitude of the coil signal C1, and determine whether the metal foreign object exists according to the information. The processor 111 may be a Central Processing Unit (CPU), a microprocessor (microprocessor), a Micro Controller Unit (MCU), or other types of Processing devices or computing devices. The signal receiving module 120 is configured to track the resonant frequency and the peak magnitude of the coil signal C1, and provide information related to the resonant frequency and the peak magnitude to the processor 111 for subsequent interpretation. The voltage divider circuit 130 includes

voltage divider resistors

131 and 132, which attenuate the coil signal C1 on the power coil 16 and output the attenuated signal to the processor 111 and the signal receiving module 120. In some embodiments, if the circuits such as the processor 111 and the signal receiving module 120 have sufficient withstand voltage, the coil signal C1 on the power supply coil 16 may be directly received by the processor 111 without using the voltage dividing circuit 130. As for other possible components or modules, such as a power supply unit, a display unit, etc., which may be increased or decreased according to the system requirements, they are not shown in the description of the embodiment.

In one embodiment, the signal receiving module 120 includes a voltage generating device 113 and a comparator 114, as shown in fig. 1. The voltage generating device 113 may be a Digital-to-Analog Converter (DAC) that receives a reference voltage information from the processor 111, converts it into an Analog voltage, and outputs the Analog voltage. One input terminal of the comparator 114 receives the reference voltage, the other input terminal receives the coil signal C1 from the power coil 16, the comparator compares the coil signal C1 with the reference voltage, and the processor 111 performs subsequent determination and signal processing according to the comparison result. It should be noted that the signal receiving module 120 may also be integrated inside the processor 111, but is not limited thereto.

Please continue to refer to fig. 1. The power receiving module 2 includes a load unit 21, a capacitor 22, a rectifying circuit 230, a power receiving coil 26 and

resonant capacitors

241 and 242. In the power receiving module 2, a magnetic conductor 261 made of a magnetic material may be selectively used to improve the electromagnetic induction capability of the power receiving coil 26 and prevent the electromagnetic energy from affecting the object in the non-inductive surface direction of the coil. The power receiving coil 26 is used for receiving the power supplied by the power supplying coil 16, and transmitting the received power to the rectifying circuit 230 for rectification, and then to the capacitor 22 and the load unit 21 at the rear end after the rectification is completed. The capacitor 22 may be a filter capacitor for filtering or a voltage stabilizing capacitor for stabilizing the output voltage, and should not be limited thereto. In the power receiving module 2, other possible components or modules, such as a signal feedback circuit, a power receiving microprocessor, etc., may be added or subtracted according to system requirements, and therefore, they are not shown in the description of the embodiment.

In addition, a metal foreign object 3 is not included in the inductive power supply 100, but is shown between the power module 1 and the power receiving module 2 in fig. 1 for convenience of illustration. When the metallic foreign object 3 is located within the power transmission range of the inductive power supply 100, it may generate heat by receiving electromagnetic energy transmitted by the power supply module 1. The foreign metal detection method of the present invention can be used to determine whether or not a foreign metal 3 is present within the power transmission range of the induction power supply 100, and stop power transmission when it is determined that a foreign metal 3 is present.

Different from the prior art that the power supply module judges the metal foreign matter by measuring the change of the attenuation slope of the coil, the invention judges the metal foreign matter by measuring the voltage attenuation proportion of the coil signal. Referring to fig. 2, fig. 2 is a schematic diagram of a metal foreign object detection process 20 according to an embodiment of the invention. As shown in fig. 2, the metal foreign object detection process 20 can be applied to a power supply terminal of an inductive power supply (e.g., the power supply module 1 of the inductive power supply 100 of fig. 1), and includes the following steps:

step 200: and starting.

Step 202: the driving signals D1 and D2 of the inductive power supply 100 are interrupted during a measurement period to stop driving the power coil 16, so as to generate a coil signal C1 of the power coil 16.

Step 204: two peaks of the coil signal C1 are measured in two consecutive oscillation cycles of the coil signal C1 to obtain two peak trigger voltages, respectively.

Step 206: based on the two peak trigger voltages, a decay parameter is calculated.

Step 208: and comparing the attenuation parameter with a corresponding critical value, and judging whether the attenuation parameter is greater than the critical value. If yes, go to step 216; if not, go to step 210.

Step 210: it is determined whether the measured number of oscillation cycles reaches a predetermined number. If yes, go to step 216; if not, go to step 212.

Step 212: the peak of the coil signal C1 is measured during the next oscillation period of the coil signal C1 to obtain a peak trigger voltage.

Step 214: calculating a damping parameter according to the peak trigger voltage and the peak trigger voltage obtained in the previous oscillation period.

Step 216: the obtained attenuation parameters are averaged to generate an average result, and the average result is compared with a basic threshold value to determine whether the average result is greater than the basic threshold value. If yes, go to step 218; if not, go to step 220.

Step 218: it is determined that the metallic foreign object 3 is not present within the power transmission range of the induction type power supply 100.

Step 220: it is determined that the metallic foreign object 3 exists within the power transmission range of the inductive power supply 100.

Step 222: and (6) ending.

According to the process 20, in the power supply module 1 of the inductive power supply 100, the driving signals D1 and D2 are interrupted for a period of time during the driving process, and the

power driving units

121 and 122 stop driving the power supply coil 16. When the power supply coil 16 stops driving, the coil signal C1 will continue to oscillate and gradually decay because energy is still present between the power supply coil 16 and the

resonant capacitors

141 and 142. As shown in fig. 3, when the driving is stopped, the driving signals D1 and D2 stay at the high potential and the low potential respectively for a period of time, and the coil signal C1 assumes an oscillating and gradually decaying waveform, and then the

power driving units

121 and 122 are re-engaged to output the square wave driving signals D1 and D2 and drive the power supply coil 16 again to output power. In other embodiments, the driving signals D1 and D2 may be controlled to stay at high level or low level simultaneously to stop driving, but not limited thereto. The above-mentioned period during which the driving signals D1 and D2 are interrupted is used for measuring the resonance of the coil signal C1 for the detection of the metallic foreign object 3, and hereinafter referred to as a measurement period for convenience of explanation.

During the measurement period, there are a plurality of consecutive oscillation periods on the coil signal C1, and the processor 111 may measure the peak of the coil signal C1 during the plurality of oscillation periods to obtain a plurality of peak trigger voltages respectively. Referring to fig. 4, fig. 4 is a schematic diagram illustrating the peak trigger voltages VB and VC obtained during a measurement period according to an embodiment of the invention. As shown in fig. 4, the coil signal C1 during the measurement period includes three peaks A, B and C. Since the first peak a occurs when the driving signals D1 and D2 just stop driving, the signal oscillation of the peak a may still be affected by the driving signals D1 and D2 rather than the natural oscillation of the power coil 16 itself, and thus the peak height of the peak a may not yet reach the height of the natural oscillation. In this case, in order to avoid the determination of the metal foreign object 3 from being distorted by the driving signals D1 and D2, the peak trigger voltage measurement of the peak a may be discarded, and only the peak trigger voltages VB and VC of the peaks B and C may be measured.

During the oscillation period of the peak to be measured, the processor 111 sets a reference voltage (shown in fig. 4 by a dotted line), outputs the reference voltage to the comparator 114 through the voltage generating device 113, and compares the reference voltage with the coil signal C1 by the comparator 114 to generate a comparison result CP 1. In detail, the processor 111 may set the reference voltage to a trigger start voltage V0_ B before entering the oscillation period corresponding to the peak B. Then, the processor 111 controls the reference voltage to gradually increase after the level of the coil signal C1 rises to exceed the reference voltage and a trigger signal appears at the output terminal of the comparator 114 (i.e. the comparison result CP1 appears as a high level). When the reference voltage rises to a level exceeding the level of the coil signal C1, the trigger signal is judged to be over (i.e., the comparison result CP1 returns to the low level), and the processor 111 can obtain the level of the reference voltage as the peak trigger voltage VB corresponding to the peak B. Similarly, in the oscillation period corresponding to the peak C, the processor 111 first sets the reference voltage to a trigger start voltage V0_ C, and then obtains the peak trigger voltage VC corresponding to the peak C in the same manner.

Next, the processor 111 calculates a first attenuation parameter PAR1 according to the peak trigger voltage VB and the peak trigger voltage VC. In detail, the first attenuation parameter PAR1 may be a ratio of an average value of the peak trigger voltage VB and the peak trigger voltage VC to a difference value of the peak trigger voltage VB and the peak trigger voltage VC. In one embodiment, the first attenuation parameter PAR1 may be calculated by dividing the result of the addition of the peak trigger voltage VB and the peak trigger voltage VC by the result of the subtraction of the peak trigger voltage VB and the peak trigger voltage VC as follows:

it is noted that chinese patent application publication No. CN 106094041 a determines the metal foreign matter, i.e., the change of the attenuation amount, by the change of the attenuation slope. However, in the case where no metallic foreign matter exists, when the output power is high (i.e., the amplitude of the coil signal C1 is large), the amount of attenuation after the coil interruption of driving is large; when the output power is low (i.e., the amplitude of the coil signal C1 is small), the amount of attenuation after the coil is interrupted from driving is small. That is, the ratio of the attenuation amount to the output power is substantially the same. For example, in the case where no metal foreign object exists, if the peak trigger voltage VB is 100 units, the peak trigger voltage VC is about 90 units; if the peak trigger voltage VB is 50 units, the peak trigger voltage VC is about 45 units, and the two voltages have different peak attenuations. Therefore, the invention adopts the ratio of the average value or the sum of the peak trigger voltage to the difference value (namely the attenuation) of the peak trigger voltage to calculate the attenuation parameter, can eliminate the influence of different output powers on the attenuation of the coil signal, and further achieves more effective judgment of the metal foreign matters. In this case, the larger the attenuation parameter, the slower the signal attenuation speed, i.e. the lower the possibility of the existence of metal foreign matter; the smaller the attenuation parameter, the faster the signal attenuation speed, i.e., the higher the possibility of the existence of metal foreign matter.

It should be noted that the peak trigger voltage is not equal to the peak voltage of the corresponding peak, and actually, the peak trigger voltage is slightly lower than the peak voltage of the corresponding peak. As can be seen from fig. 4, the peak trigger voltage VB is close to and slightly lower than the peak voltage of the peak B, and the peak trigger voltage VC is close to and slightly lower than the peak voltage of the peak C. Since the trigger start potentials V0_ B and V0_ C can be set at voltage levels slightly lower than the peak B and the peak C, respectively, the rising reference voltage and the coil signal C1 cross at the right side of the peak, so that the peak trigger voltages VB and VC obtained from the reference voltage are also slightly lower than and close to their corresponding peak voltages. In addition, as can be seen from the above calculation method of the attenuation parameter, the magnitude of the attenuation parameter is mainly affected by the attenuation ratio, and therefore, the determination result of the metal foreign object obtained by using the peak trigger voltage having a value slightly lower than the peak voltage as the calculation reference is still substantially the same as the determination result obtained according to the peak voltage. The attenuation parameter can be used to determine the metal foreign matter as long as the attenuation parameter reflects the attenuation amount or the attenuation ratio.

As described above, the first attenuation parameter PAR1 is equal to the result of the addition of the peak trigger voltage VB to the peak trigger voltage VC divided by the result of the subtraction of the peak trigger voltage VB from the peak trigger voltage VC. After obtaining the first attenuation parameter PAR1, the processor 111 may set a first threshold value TH1 and compare the first attenuation parameter PAR1 with the first threshold value TH1 to determine whether the metallic foreign object 3 exists within a power transmission range of the inductive power supply 100. In an embodiment, when the first attenuation parameter PAR1 is greater than the first threshold value TH1, it may be determined that the metallic foreign object 3 is not present within the power transmission range of the inductive power supply 100; when the first attenuation parameter PAR1 is smaller than the first threshold TH1, the subsequent determination is further performed. In an inductive power supply system, a power supply or a load end often has a large amount of noise, which is likely to interfere with analysis and detection of a coil signal, so that data or results determined as metal foreign objects need to be continuously obtained for accurate determination of the metal foreign objects, so as to avoid erroneous determination of the metal foreign objects caused by noise interference, and thus, power output is erroneously turned off.

In one embodiment, the processor 111 may set a base threshold value THO. In the product testing process of the induction type power supply, the attenuation parameter variability may exist in different products and different environments, and the basic threshold value THO can be set according to the lowest attenuation parameter measured under the condition that no metal foreign matter exists. Preferably, the basic threshold value THO may be set to a lower value with a looser determination criterion to avoid the noise interference being erroneously determined as the existence of the metal foreign object. Next, the processor 111 may add different values to the basic threshold value THO to obtain a plurality of threshold values, such as a first threshold value TH1, a second threshold value TH2, a third threshold value TH3, and so on. The processor 111 may compare the first attenuation parameter PAR1, the second attenuation parameter PAR2, the third attenuation parameter PAR3, and the fourth attenuation parameter PAR4 obtained during a measurement period with the first threshold value TH1, the second threshold value TH2, the third threshold value TH3, and the basic threshold value THO, respectively, to determine the metal foreign object 3. For example, the processor may set the base threshold value THO to 150, and set the first threshold value TH1 to 150 plus 30, i.e. 180, of the base threshold value TH 0; the second threshold TH2 is set to the base threshold THO 150 plus 20, i.e. 170; the third threshold TH3 is set to the base threshold TH0 equal to 150 plus 10, i.e., 160. The first threshold value TH1 is greater than the second threshold value TH2, and the second threshold value TH2 is greater than the third threshold value TH 3.

First, the processor 111 compares the first attenuation parameter PAR1 with a first threshold TH 1. In one embodiment (as shown in table one), the processor 111 obtains the peak trigger voltage VB as 1000 units and the peak trigger voltage VC as 990 units, and calculates the first attenuation parameter PAR1 as 199. Since the first attenuation parameter PAR 1-199 is greater than the first threshold TH 1-180, which means that it is much greater than the basic threshold THO, the processor 111 directly determines that the alien metal 3 is not present.

Peak/oscillation period	B	C	×	×	×
						Peak trigger voltage	1000	990	×	×	×
Attenuation parameter		199	×	×	×
						Critical value		180	170	160	150

Watch 1

In this example, the first attenuation parameter PAR1 is greater than the first threshold value TH1 and much greater than the basic threshold value THO, which indicates that the probability of the existence of the metal foreign object 3 is very low, and belongs to a very safe state, so the system directly determines that the metal foreign object 3 does not exist. In this case, the processor 111 only needs to measure 2 oscillation cycles to complete the determination of the metal foreign object 3. In other words, the determination of the metallic foreign object 3 can be completed only after the oscillation period corresponding to the peak a is not measured and the first attenuation parameter PAR1 is obtained after the measurement is completed in the oscillation period corresponding to the peaks B and C, which only needs to include 3 oscillation periods during the measurement period when the driving signals D1 and D2 are interrupted.

In an embodiment, the first attenuation parameter PAR1 is smaller than the first threshold value TH1, and the processor 111 further performs the subsequent determination of the metallic foreign object 3, as shown in table two.

Peak/oscillation period	B	C	D	×	×
						Peak trigger voltage	1000	988	977	×	×
Attenuation parameter		166	179	×	×
						Critical value		180	170	160	150

Watch two

In detail, the processor 111 first compares the first attenuation parameter PAR1 with the first threshold TH 1. After determining that the first attenuation parameter PAR 1-166 is smaller than the first threshold TH 1-180, the processor 111 may measure a next oscillation period of the coil signal C1 (an oscillation period corresponding to the peak D). As shown in fig. 5, in the oscillation period of the peak D, the processor 111 may first set the reference voltage to a trigger start voltage V0_ D, and obtain the peak trigger voltage VD corresponding to the peak D according to the above-mentioned manner. Next, the processor 111 calculates a second attenuation parameter PAR2 according to the peak trigger voltage VC and the peak trigger voltage VD. In detail, the processor 111 may calculate the second attenuation parameter PAR2 by dividing the result of the addition of the peak trigger voltage VC and the peak trigger voltage VD by the result of the subtraction of the peak trigger voltage VC and the peak trigger voltage VD as follows:

in this example, the peak trigger voltage VC is 988 units of voltage and the peak trigger voltage VD is 977 units of voltage, which are calculated to yield a second attenuation parameter PAR2 of 179 (rounded off after the decimal point). Next, the processor 111 compares the second attenuation parameter PAR2 with a second threshold TH2, and determines that the second attenuation parameter PAR 2-179 is greater than the second threshold TH 2-170. In this case, the processor 111 stops measuring the subsequent oscillation period during the measurement period, and averages the obtained first attenuation parameter PAR1 and second attenuation parameter PAR2, and compares the average result with the basic threshold value THO to determine the metal foreign object 3. In this example, the average value of the first attenuation parameter PAR1 and the second attenuation parameter PAR2 is greater than the basic threshold value THO, so the processor 111 determines that the metallic foreign object 3 is not present in the power transmission range of the inductive power supply 100.

In another embodiment, the second attenuation parameter PAR2 may also be smaller than the second threshold TH2, and the processor 111 further performs the subsequent determination of the metallic foreign object 3, as shown in table three.

Peak/oscillation period	B	C	D	E	×
						Peak trigger voltage	1000	986	974	962	×
Attenuation parameter		142	163	161	×
						Critical value		180	170	160	150

Watch III

In detail, the processor 111 first compares the first attenuation parameter PAR1 with the first threshold TH 1. After determining that the first attenuation parameter PAR1 is less than the first threshold TH1 and 180, the processor 111 may measure a next oscillation period (corresponding to the oscillation period of the peak D) of the coil signal C1 to obtain a second attenuation parameter PAR2, and compare the second attenuation parameter PAR2 with a second threshold TH 2. Next, after determining that the second attenuation parameter PAR2 is less than the second threshold TH2 and 170, the processor 111 may measure a next oscillation period (corresponding to the oscillation period of the peak E) of the coil signal C1. As shown in fig. 6, in the oscillation period of the peak E, the processor 111 may first set the reference voltage to a trigger start voltage V0_ E, and obtain the peak trigger voltage VE corresponding to the peak E according to the above-mentioned manner. Next, the processor 111 may calculate a third attenuation parameter PAR3 according to the peak trigger voltage VD and the peak trigger voltage VE. In detail, the processor 111 may calculate the third attenuation parameter PAR3 by dividing the result of the addition of the peak trigger voltage VD and the peak trigger voltage VE by the result of the subtraction of the peak trigger voltage VD and the peak trigger voltage VE, and the detailed calculation is as follows:

in this example, the peak trigger voltage VD is 974 units and the peak trigger voltage VE is 962 units, calculated to result in a third attenuation parameter PAR3 of 161 (rounded off after the decimal point). Next, the processor 111 compares the third attenuation parameter PAR3 with a third threshold TH3, and determines that the third attenuation parameter PAR 3-161 is greater than the third threshold TH 2-160. In this case, the processor 111 stops measuring the subsequent oscillation period during the measurement period, and averages the obtained first attenuation parameter PAR1, second attenuation parameter PAR2 and third attenuation parameter PAR3, and compares the average result with the basic threshold value THO to determine the metallic foreign object 3. In this example, the average value of the first attenuation parameter PAR1, the second attenuation parameter PAR2, and the third attenuation parameter PAR3 is greater than the basic threshold value THO, so the processor 111 determines that the metallic foreign object 3 is not present in the power transmission range of the inductive power supply 100.

In another embodiment, the third attenuation parameter PAR3 may be smaller than the third threshold TH3, and the processor 111 further performs the subsequent determination of the metallic foreign object 3, as shown in table four.

Peak/oscillation period	B	C	D	E	F
						Peak trigger voltage	1000	984	968	952	936
Attenuation parameter		124	122	120	118
						Critical value		180	170	160	150

Watch four

In detail, the processor 111 first compares the first attenuation parameter PAR1 with the first threshold TH 1. After determining that the first attenuation parameter PAR1 is smaller than the first threshold TH1 and 180, the processor 111 may measure a next oscillation period (corresponding to the oscillation period of the peak D) of the coil signal C1 to obtain a second attenuation parameter PAR2, and compare the second attenuation parameter PAR2 with a second threshold TH 2. Then, when the second attenuation parameter PAR2 is determined to be less than the second threshold TH2 or 170, the processor 111 may measure a next oscillation period (corresponding to the oscillation period of the peak E) of the coil signal C1 to obtain a third attenuation parameter PAR3, and compare the third attenuation parameter PAR3 with the third threshold TH 3. Next, after determining that the third attenuation parameter PAR3 is smaller than the third threshold TH3 is smaller than 160, the processor 111 may measure a next oscillation period (corresponding to the oscillation period of the peak F) of the coil signal C1. As shown in fig. 7, in the oscillation period of the peak F, the processor 111 may first set the reference voltage to a trigger start voltage V0_ F, and obtain the peak trigger voltage VF corresponding to the peak F according to the above-mentioned manner. Next, the processor 111 may calculate a fourth attenuation parameter PAR4 according to the peak trigger voltage VE and the peak trigger voltage VF. In detail, the processor 111 may calculate the fourth attenuation parameter PAR4 by dividing the result of the addition of the peak trigger voltage VE and the peak trigger voltage VF by the result of the subtraction of the peak trigger voltage VE and the peak trigger voltage VF, and the detailed calculation is as follows:

in this example, the peak trigger voltage VE is 952 units and the peak trigger voltage VF is 936 units, which are calculated to obtain the fourth attenuation parameter PAR4 as 118. Since the number of oscillation cycles measured by the processor 111 during the measurement period has reached the predetermined number, the processor 111 averages the obtained first attenuation parameter PAR1, second attenuation parameter PAR2, third attenuation parameter PAR3 and fourth attenuation parameter PAR4, and compares the average result with the basic threshold value THO to determine the metallic foreign object 3. In this example, the average value of the first attenuation parameter PAR1, the second attenuation parameter PAR2, the third attenuation parameter PAR3, and the fourth attenuation parameter PAR4 is smaller than the basic threshold value THO, so the processor 111 determines that the metallic foreign object 3 exists in the power transmission range of the inductive power supply 100.

In the above embodiment, the measurement period in which the driving signals D1 and D2 are interrupted only needs to include 3-6 unequal oscillation periods, so as to complete the determination of the metal foreign object 3. Compared with the method disclosed in the Chinese patent application publication No. CN 106094041A, which requires 7-15 unequal coil oscillation cycles to complete the measurement of four peak voltage levels to determine the change of the attenuation slope, the method for detecting the metal foreign matters can be completed in less time, so that the interruption time of the driving signals D1 and D2 is shortened. Generally, under the condition that the metallic foreign object 3 is not present and the coil signal C1 is not determined to be interfered by noise, the obtained first attenuation parameter PAR1 is usually much larger than the basic threshold value THO, at this time, only two oscillation cycles need to be measured to complete the determination of the metallic foreign object 3, and after the determination is completed, the

power driving units

121 and 122 can be immediately connected to the circuit to start the driving signals D1 and D2, as shown in fig. 3. On the other hand, when the attenuation parameter is decreased due to metal proximity or noise interference, more oscillation cycles need to be measured. In other words, the smaller the value of the damping parameter, the higher the probability of representing the presence of metallic foreign matter, and the number of oscillation cycles measured at this time also increases simultaneously. Finally, no matter how many oscillation cycles are measured or how many attenuation parameters are obtained, the processor 111 averages the obtained attenuation parameters and compares the average result with the basic threshold value THO to determine whether the metallic foreign matter 3 exists. In general, when the coil stops driving, the signal is in a natural resonance state, and if no metal foreign matter exists, the amount of change in the attenuation slope of the coil signal with respect to the value of the signal amplitude is extremely small. Since each damping parameter is calculated in the same way and based on the peak trigger voltage of the adjacent oscillation period, the value of the damping parameter is rather stable. In the inductive power supply system, the judgment of the signal is necessarily affected by the noise of the power supply or the circuit, but most of the power supply/circuit noise is reflected on the attenuation parameter and only small-amplitude value jitter occurs, and at the moment, the attenuation parameter is often far larger than the critical value without affecting the judgment result. On the contrary, when the metal foreign body appears, the peak trigger voltage can be quickly attenuated, and the attenuation parameter can be quickly reduced through the calculation mode of dividing the addition result by the subtraction result, so that the metal foreign body can be effectively detected and distinguished.

In each measuring period, the number of the oscillation cycles can be determined according to the comparison result of the attenuation parameters and the corresponding critical values, and the average value of all the attenuation parameters is obtained to judge the metal foreign matters. Generally, when any of the first, second and third attenuation parameters PAR 1-PAR 3 is greater than the corresponding threshold, the calculation of the last fourth attenuation parameter PAR4 is not performed. Since the first, second and third threshold values TH 1-TH 3 are all larger than the basic threshold value THO, the average value of the first three attenuation parameters PAR 1-PAR 3 is usually larger than the basic threshold value THO under the condition that the fourth attenuation parameter PAR4 is not calculated, and the determination result that the foreign metal object 3 does not exist is obtained. In this case, the processor 111 may also determine the number of the acquired attenuation parameters or the number of the measured oscillation cycles, and only when the number of the acquired attenuation parameters reaches a preset value (for example, four attenuation parameters), calculate an average value of the attenuation parameters to determine the metal foreign object 3; if the obtained attenuation parameter quantity does not reach the preset value, the processor 111 directly determines that the metallic foreign object 3 does not exist.

In addition, to improve the determination accuracy and prevent the power output from being turned off due to erroneous determination, the processor 111 may set a metal foreign object counter. If the average value of the attenuation parameter obtained in a measuring period is smaller than the basic critical value, the metal foreign matter counter is increased by one. When the metal foreign matter counter reaches a specific value within a predetermined period, it is determined that the metal foreign matter 3 is present. Alternatively, the presence of the metal foreign matter 3 may be determined when the average value of the attenuation parameter obtained in a plurality of consecutive measurement periods is smaller than the basic threshold value.

It should be noted that, in the above embodiment, the processor 111 first sets a reference voltage at a trigger start level, controls the reference voltage to rise when the output terminal of the comparator 114 triggers, and then obtains the level of the reference voltage as the peak trigger voltage at the end of triggering. In order for the peak trigger voltage to effectively reflect the voltage level of the corresponding peak, the trigger initiation voltage should be set to a position close to and slightly below the peak voltage to successfully trigger while bringing the peak trigger voltage close to the peak voltage level. If the trigger starting potential is set too high, the situation that the trigger starting potential is higher than the peak voltage and cannot be triggered successfully can occur; if the trigger start voltage is set too low, although successful triggering can be achieved, the peak trigger voltage may be too low to reflect the actual peak voltage.

In an embodiment, the processor 111 may calculate the trigger start potential used in the current measurement period according to a previous peak trigger voltage obtained in a previous measurement period, for example, a value obtained by subtracting a preset voltage value from the previous peak trigger voltage is set as the trigger start potential. For example, for the oscillation period of the peak B, if the peak trigger voltage VB obtained in the previous measurement period is 1000 unit voltage, the trigger start voltage V0_ B in the current measurement period can be set to 900 unit voltage (i.e. 1000 minus the preset voltage value of 100); for the oscillation period of the peak C, if the peak trigger voltage VC obtained in the previous measurement period is 980 units of voltage, the trigger start voltage V0 — C in the current measurement period can be set to 880 units of voltage (i.e., 980 minus the preset voltage value of 100). From the peak trigger voltage during the previous measurement period, the processor 111 knows the possible level of the peak voltage to set the trigger start potential at a slightly lower level. The trigger starting potential with lower level can improve the probability of triggering, and unless the peak voltage is rapidly reduced, the triggering can be successfully carried out under most conditions, and the judgment result of the metal foreign matter can be obtained.

The peak voltage level of chinese patent application publication No. CN 106094041 a is determined by determining whether to increase or decrease the reference voltage according to the result of trigger in the previous measurement period, and determining that the reference voltage is locked at the peak voltage level when trigger occurs or does not occur in several measurement periods. Therefore, when the load and the output power are not changed, a plurality of measurement periods are required to lock the reference voltage to the peak voltage level. In contrast, according to the method of obtaining the peak trigger voltage of the present invention, setting the trigger start potential at a lower potential can increase the probability of triggering, and the attenuation parameter can be immediately calculated to determine the metal foreign object as long as triggering occurs. In addition, the trigger start potential can be continuously adjusted to a preferred level in the determination process, for example, the trigger start potential V0_ B is set to 900 unit voltage during the current measurement period, and the triggering is finished when the reference voltage rises to 910 unit voltage, which represents that the peak value of the trigger voltage VB is decreased to 910 unit voltage, in this case, the trigger start potential V0_ B can be set to 810 unit voltage (i.e., 910 minus the preset voltage value of 100) during the next measurement period, so as to achieve a preferred triggering effect and improve the probability of successful triggering.

It should be noted that in some cases, the processor 111 cannot obtain the corresponding peak trigger voltage in the previous measurement period. For example, during the previous measurement period, the processor 111 calculates the first attenuation parameter PAR1 according to the peak trigger voltage VB and the peak trigger voltage VC, and determines that the first attenuation parameter PAR1 is greater than the first threshold value TH1, so that it is not necessary to measure the subsequent oscillation period and calculate other attenuation parameters. However, during the current measurement period, the processor 111 determines that the first attenuation parameter PAR1 is smaller than the first threshold TH1 and a subsequent oscillation period needs to be measured. In other words, the trigger start voltage V0_ D corresponding to the peak D needs to be obtained during the current measurement period, but the oscillation period of the peak D is not measured during the previous measurement period, so the peak trigger voltage VD does not exist as a basis for estimating the trigger start voltage V0_ D. In this case, the processor 111 may use another previous peak trigger voltage (i.e. the peak trigger voltage VC corresponding to the peak C) of the previous oscillation period in the current measurement period as a basis, and estimate a magnitude that the peak trigger voltage VD corresponding to the peak D may be lower than the peak trigger voltage VC, so as to calculate the trigger start voltage V0_ D. For example, if the peak trigger voltage VC is 900 units, the peak trigger voltage VD of the peak D can be estimated to be 870 units, and the trigger start voltage V0_ D is set to 770 units (i.e. 870 minus the predetermined voltage value of 100). In another embodiment, the peak trigger voltage VD of the peak D can also be estimated according to the peak trigger voltages VB and VC in the same measurement period. For example, if the peak trigger voltage VB is 100 units of voltage and the peak trigger voltage VC is 90 units of voltage, the peak trigger voltage VD of the peak D can be estimated to be about 80 units of voltage, and the trigger start voltage V0_ D can be set to 70 units of voltage to detect the actual peak trigger voltage VD.

Generally, if the oscillation period corresponding to the peak D is not measured during the previous measurement period, the record representing the previous peak trigger voltage corresponding to the peak D may be derived from a measurement result a longer time ago. However, the load and/or power output may vary during the power supply process of the inductive power supply 100, such that the peak voltage of the coil signal C1 varies greatly, which may be several tens or hundreds times. Under the condition, the peak trigger voltage record before a long time does not have reference value, so that the peak trigger voltage of the previous oscillation period in the same measurement period is used as the basis, a more appropriate trigger starting potential can be obtained, and the probability of successfully triggering and obtaining the attenuation parameter and the judgment result of the metal foreign matter is further improved.

It is noted that the above method does not successfully trigger and obtain the attenuation parameter during every measurement period. If the corresponding peak trigger voltage cannot be obtained due to no trigger in one oscillation period, the processor 111 discards the calculation and determination results in the measurement period, and reduces the trigger start voltage to increase the probability of successful trigger in the next measurement period. In addition, to effectively obtain the peak trigger voltage, the processor 111 may first measure the resonant frequency of the coil and obtain a position interval where the peak may occur in each resonant period. If no trigger occurs in this interval, it represents that the trigger start voltage is too high, so the processor 111 decreases the trigger start voltage in the next measurement period and tries to trigger again to obtain the corresponding peak trigger voltage.

In view of the above, the present invention can measure the coil signal to obtain the peak trigger voltages corresponding to a plurality of peaks during the measurement period of the interruption of the driving signal, and calculate the attenuation parameter according to the ratio of the average value of two adjacent peak trigger voltages to the difference value thereof, and then compare the attenuation parameter with the corresponding critical value to determine whether to obtain more peak trigger voltages to perform the subsequent judgment, and at the same time, determine the metal foreign object. The processor can set the reference voltage at a trigger initial potential, and control the reference voltage to gradually rise when triggering occurs, so as to obtain the peak trigger voltage. Those skilled in the art can make modifications or changes thereto without being limited thereto. For example, in the above embodiment, a maximum of 5 oscillation cycles are measured during a measurement period to obtain 5 peak trigger voltages for calculating 4 damping parameters. In other embodiments, the maximum number of measured oscillation cycles and the maximum number of acquired damping parameters may be adjusted according to system requirements, but are not limited thereto. In addition, in the above embodiments, the values of the peak trigger voltage and the trigger start voltage are only examples, and those skilled in the art can set and obtain appropriate voltage values according to system requirements. For example, the voltage generating device 113 may be implemented by a digital-to-analog converter, and the unit voltage may be a digital value set by the processor 111, which is converted into a corresponding analog voltage by the digital-to-analog converter and then output, and the peak trigger voltage and the trigger start voltage may have different values according to different specifications of the digital-to-analog converter. For example, if the voltage generator 113 is a 12-bit digital-to-analog converter, it can receive a digital value of 0-4095 and generate an output voltage according to the possible voltage range of the coil signal C1 (after passing through the voltage divider circuit 130). In addition, the peak trigger voltage is a level of the reference voltage rising from the trigger start potential to the trigger end, and the processor 111 may adjust a rising speed of the reference voltage, for example, the processor 111 may control the reference voltage to rise at a fixed speed and adjust the rising speed to a preferred value, so that the level of the reference voltage at the trigger end can effectively reflect the level of the peak voltage.

The metal foreign matter detection method can effectively reduce the time of interruption of the driving signal so as to reduce the influence of the interruption of the driving on the power supply. Therefore, the process of determining the metal foreign matter should be completed in the shortest time possible. In the above embodiment, the determination of the metal foreign matter can be completed only by measuring 2 oscillation cycles at minimum, and the drive signal only needs to interrupt three oscillation cycles at minimum together with the oscillation cycle of the discarded first peak. In another embodiment, the time for the drive signal to interrupt can be reduced still further.

Referring to fig. 8, fig. 8 is a schematic diagram of another metal foreign object detection process 80 according to an embodiment of the invention. As shown in fig. 8, the metal foreign object detection process 80 can be applied to a power supply terminal of an inductive power supply (e.g., the power supply module 1 of the inductive power supply 100 of fig. 1), and includes the following steps:

step 800: and starting.

Step 802: a previous peak trigger voltage corresponding to the measurement during the previous measurement period is obtained and set as a reference voltage value.

Step 804: the driving signals D1 and D2 of the inductive power supply 100 are interrupted during a measurement period to stop driving the power coil 16, so as to generate a coil signal C1 of the power coil 16.

Step 806: a first peak of the coil signal C1 is measured during an oscillation period of the coil signal C1 to obtain a first peak trigger voltage.

Step 808: the first peak trigger voltage is compared to a reference voltage value and it is determined whether the first peak trigger voltage is equal to or close to the reference voltage value. If yes, go to step 810; if not, go to step 812.

Step 810: if it is determined that the metal foreign object 3 is not present within a power transmission range of the inductive power supply 100, step 818 is performed.

Step 812: a second peak of the coil signal C1 is measured during a next oscillation period of the coil signal C1 to obtain a second peak trigger voltage.

Step 814: and calculating an attenuation parameter according to the first peak trigger voltage and the second peak trigger voltage.

Step 816: the attenuation parameter is compared with a threshold value to determine whether there is a metal foreign object 3 in the power transmission range of the inductive power supply 100.

Step 818: and (6) ending.

The difference between the metallic foreign object detection process 80 and the metallic foreign object detection process 20 is that in the metallic foreign object detection process 80, the processor 111 only needs to measure a peak of the coil signal C1 and obtain a peak trigger voltage at least during the measurement period when the driving signals D1 and D2 are interrupted, so as to complete the determination of the metallic foreign object 3.

For example, referring to fig. 9, fig. 9 is a schematic diagram illustrating the determination of the metal foreign object by a peak trigger voltage VB during a measurement period according to the embodiment of the invention. As shown in fig. 9, the coil signal C1 during the measurement period includes only two peaks a and B. Similarly, to avoid the determination of the metal foreign object 3 being distorted by the driving signals D1 and D2, the peak trigger voltage measurement of the peak a may be discarded. Then, in the oscillation period corresponding to the peak B, the processor 111 sets the reference voltage at a trigger start voltage V0_ B and obtains the peak trigger voltage VB corresponding to the peak B as described above.

It is noted that, during the previous measurement period, the processor 111 may first measure a previous peak trigger voltage corresponding to the peak B in the previous measurement period, i.e. the peak trigger voltage VB corresponding to the peak B in the previous measurement period, and record the peak trigger voltage VB as a reference voltage value, for example, the processor 111 may store the reference voltage value in a memory. Meanwhile, only the peak trigger voltage VB is obtained in the previous measuring period, and the judgment result indicates that no metal foreign body 3 exists; alternatively, only the peak trigger voltages VB and VC are obtained during the previous measurement period, and the calculated first attenuation parameter PAR1 is greater than the first threshold value TH1 to indicate that no metallic foreign object 3 exists. Then, during the current measurement period, the processor 111 only needs to obtain the peak trigger voltage VB corresponding to the peak B, and the determination of the metallic foreign object 3 can be completed. In detail, the processor 111 can compare the peak trigger voltage VB with the reference voltage value, and determine that the metallic foreign object 3 is not present in the power transmission range of the inductive power supply 100 when the peak trigger voltage VB is equal to or close to the reference voltage value. In this case, after the peak trigger voltage VB is measured, the

power driving units

121 and 122 are reengaged to drive the power coil 16 to output power again through the driving signals D1 and D2.

Generally, when the metallic foreign object is not present and the coil output power and the load state are not changed, the peak trigger voltage VB corresponding to the peak B is also substantially unchanged. On the contrary, when a metal foreign object 3 enters the power transmission range of the inductive power supply 100, the peak trigger voltage VB will be greatly reduced under the influence of the metal foreign object 3 if other conditions (such as the coil output power and the load) are not changed. In this case, the processor 111 only needs to measure the peak trigger voltage VB to complete the determination of the metal foreign object 3. In this way, the measurement period during which the driving signals D1 and D2 are interrupted only needs to include at least 2 oscillation cycles, wherein the oscillation cycle corresponding to the peak a is not measured, and after the measurement is completed and the peak trigger voltage VB is obtained within the oscillation cycle corresponding to the peak B, the determination of the metallic foreign object 3 can be completed by comparing the peak trigger voltage VB with the previously obtained reference voltage value.

In one embodiment, when the peak trigger voltage VB is determined to be equal to or close to the reference voltage value, it represents that no metal foreign object exists in the power transmission range of the inductive power supply 100. At this time, the processor 111 can update the stored reference voltage value and set it as the current peak trigger voltage VB for the determination of the next measurement period.

Note that the determination of equality or closeness may be made in any manner. For example, if the peak trigger voltage VB is within a specific range of values above and below the reference voltage value, it can be determined that the two are equal or close to each other, for example, the interval of 50 units of voltage above and below the reference voltage value can be set as close to the reference voltage value, and the reference voltage value obtained in the previous measurement period is 1000 units of voltage. In this case, if the peak trigger voltage VB is within the range of 950 to 1050 unit voltages, the processor 111 may determine that the peak trigger voltage VB is equal to or close to the reference voltage value, and further determine that the metal foreign object 3 does not exist. In another embodiment, the range of values within a specific ratio of the upper and lower values of the reference voltage may be set to be equal to or close to, for example, the range of values within five percent of the upper and lower values of the reference voltage may be set to be close to the reference voltage, and the reference voltage obtained during the previous measurement period may be 500 volts. In this case, if the peak trigger voltage VB is within the range of 475 to 525 unit voltages, the processor 111 can determine that the peak trigger voltage VB is equal to or close to the reference voltage value, and further determine that the metallic foreign object 3 does not exist.

In addition, if the peak trigger voltage VB during the current measurement period is determined not to be equal to or close to the reference voltage value, it indicates that there may be a metal foreign object 3 or a change in the output power and/or load of the system. At this time, the processor 111 needs to further measure the next oscillation period of the coil signal C1 and obtain the corresponding peak trigger voltage. Next, the processor 111 calculates an attenuation parameter according to the peak trigger voltages measured in two adjacent oscillation periods, and compares the attenuation parameter with a corresponding threshold value to determine the metal foreign object 3. In other words, in the foreign metal detection process 80, if a first peak trigger voltage (e.g. VB) is determined to be not equal to or close to the reference voltage value, the next oscillation period is continuously measured to obtain a second peak trigger voltage (e.g. VC in fig. 4) for further determination of the foreign metal 3, which can be implemented by the foreign metal detection method 20 shown in fig. 2.

It is noted that in certain situations, it may happen that the metallic foreign object 3 approaches while the peak trigger voltage VB is still equal to or close to the reference voltage value due to coil movement or load variations. To avoid that the metal foreign object 3 cannot be effectively determined under the above conditions, the processor 111 may set a continuous number of times or an upper limit of a continuous time that the peak trigger voltage VB is determined to be equal to or close to the reference voltage value, and when the upper limit is reached, perform the steps of measuring a next oscillation period to obtain a second peak trigger voltage (e.g. VC in fig. 4) and calculating the attenuation parameter, i.e. perform the determination of the metal foreign object 3 by the above-mentioned metal foreign object detection method 20 shown in fig. 2. In one embodiment, the processor 111 may include a counter for counting the consecutive times that the peak trigger voltage VB is determined to be equal to or close to the reference voltage value, and thus only a peak trigger voltage VB is measured, and when the counter reaches the upper limit, the metallic foreign object detection method 20 shown in fig. 2 is executed instead, and the processor 111 resets the counter to count the consecutive times again. Alternatively, the processor 111 may also include a timer for determining the continuous time during which the peak trigger voltage VB is determined to be equal to or close to the reference voltage value, and when the timer expires, the processor 111 resets the timer to recalculate the continuous time instead of performing the metallic foreign object detection method 20 shown in fig. 2. Alternatively, the timer may be operated without considering the determination result of the peak trigger voltage VB, for example, the timer may be periodically operated according to a fixed timing period, the metal foreign object detection method 80 shown in fig. 8 may be adopted at ordinary times, and the metal foreign object detection method 20 shown in fig. 2 is forcibly executed when the timing period expires.

In summary, the present invention provides a method for detecting a metallic foreign object, which can measure a coil signal to obtain one or more peak trigger voltages during a measurement period when a driving signal is interrupted, compare the peak trigger voltage with a reference voltage value obtained previously to determine the metallic foreign object, or calculate an attenuation parameter according to a ratio of an average value of two adjacent peak trigger voltages to a difference value thereof, and further compare the attenuation parameter with a corresponding threshold value to determine whether to obtain more peak trigger voltages to perform a subsequent determination, so as to determine the metallic foreign object. The processor can set the reference voltage at a trigger starting potential of a lower level, and control the reference voltage to gradually rise when triggering occurs, so as to obtain the peak trigger voltage. Setting the trigger initiation voltage at a lower level increases the probability of successful triggering and obtaining the peak trigger voltage. In addition, when the metal foreign matter does not exist, the metal foreign matter detection method can finish the judgment of the metal foreign matter only by measuring one or two coil oscillation periods and correspondingly obtaining one or two peak trigger voltages. Even if the first peak which is not measured is added, the measurement period of the interruption of the driving signal only comprises 2-3 coil oscillation cycles at least, and the influence of the interruption of the driving signal on the power output can be greatly reduced. In addition, the metal foreign matter detection method can judge through the attenuation proportion of the coil signal, so as to replace the mode of judging by adopting the attenuation amount or the attenuation slope in the past, and solve the defect that the judgment is easily influenced by the amplitude and the load of the coil according to the attenuation slope.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A metal foreign object detection method is used for a power supply module of an induction type power supply, the power supply module comprises a power supply coil, and the metal foreign object detection method comprises the following steps:

interrupting at least one driving signal of the inductive power supply in a measuring period to stop driving the power supply coil so as to generate a coil signal of the power supply coil;

measuring a plurality of wave peaks of the coil signal in a plurality of continuous oscillation periods of the coil signal to respectively obtain a plurality of peak trigger voltages;

calculating a first attenuation parameter according to a first peak trigger voltage and a second peak trigger voltage in the plurality of peak trigger voltages; and

comparing the first attenuation parameter with a first critical value to judge whether metal foreign matters exist in a power transmission range of the induction type power supply;

wherein the step of calculating the first decay parameter according to the first peak trigger voltage and the second peak trigger voltage of the plurality of peak trigger voltages comprises:

and calculating the first attenuation parameter according to the ratio of the average value of the first peak trigger voltage and the second peak trigger voltage to the difference value of the first peak trigger voltage and the second peak trigger voltage.

2. The method of claim 1, wherein the first attenuation parameter is equal to a result of adding the first peak trigger voltage and the second peak trigger voltage divided by a result of subtracting the first peak trigger voltage and the second peak trigger voltage.

3. The method of claim 1, wherein the first peak trigger voltage is close to and lower than a peak voltage of a corresponding first peak of the plurality of peaks, and the second peak trigger voltage is close to and lower than a peak voltage of a corresponding second peak of the plurality of peaks.

4. The method of claim 1, wherein the step of measuring the plurality of peaks of the coil signal during the consecutive oscillation cycles of the coil signal to obtain the plurality of peak trigger voltages comprises:

performing the following steps within one of the plurality of oscillation periods:

setting a reference voltage at a trigger starting potential;

after a trigger signal appears, controlling the reference voltage to gradually rise; and

the level of the reference voltage at the end of the trigger signal is obtained as a peak trigger voltage of the plurality of peak trigger voltages.

5. The method of claim 4, wherein the step of measuring the plurality of peaks of the coil signal during the consecutive oscillation cycles of the coil signal to obtain the plurality of peak trigger voltages respectively further comprises:

obtaining a first previous peak trigger voltage measured in a previous measurement period, and setting a value obtained by subtracting a preset voltage value from the first previous peak trigger voltage as the trigger starting potential; or

When the first previous peak trigger voltage is not obtained in the previous measurement period, executing the following steps:

obtaining a second previous peak trigger voltage in a previous oscillation period of the oscillation periods;

calculating an estimated peak trigger voltage according to the second previous peak trigger voltage; and

and setting the value obtained by subtracting the preset voltage value from the estimated peak trigger voltage as the trigger initial potential.

6. The method as claimed in claim 1, wherein the step of comparing the first attenuation parameter with the first threshold value to determine whether there is a metal foreign object in the power transmission range of the inductive power supply comprises:

when the first attenuation parameter is larger than the first critical value, judging that no metal foreign matter exists in the power transmission range of the induction type power supply; and

when the first attenuation parameter is smaller than the first critical value, the following steps are also executed:

obtaining a third peak trigger voltage of the plurality of peak trigger voltages;

calculating a second attenuation parameter according to the second peak trigger voltage and the third peak trigger voltage; and

the second attenuation parameter is compared with a second threshold value.

7. The method of claim 6, wherein the first threshold is obtained by adding a first value to a predetermined basic threshold, and the second threshold is obtained by adding a second value to the basic threshold, wherein the second value is smaller than the first value.

8. The metallic foreign matter detection method according to claim 1, further comprising:

calculating a plurality of attenuation parameters according to the plurality of peak trigger voltages; and

averaging the attenuation parameters to determine whether there is a metal foreign object in the power transmission range of the inductive power supply.

9. The method of claim 8, wherein the step of averaging the attenuation parameters to determine whether there is a metal foreign object in the power transmission range of the inductive power supply comprises:

obtaining an average result generated by averaging the attenuation parameters;

comparing the average result with a basic critical value;

when the average result is larger than the basic critical value, judging that no metal foreign matter exists in the power transmission range of the induction type power supply; and

and when the average result is smaller than the basic critical value, judging that metal foreign matters exist in the power transmission range of the induction type power supply.

10. A power supply module for an inductive power supply for performing a metal foreign object detection method, the power supply module comprising:

a power supply coil;

a resonance capacitor coupled to the power supply coil for resonating with the power supply coil;

at least one power supply driving unit, coupled to the power supply coil and the resonant capacitor, for sending at least one driving signal to the power supply coil to drive the power supply coil to generate energy, and interrupting the at least one driving signal during a measurement period to stop driving the power supply coil to generate a coil signal of the power supply coil;

a signal receiving module, coupled to the power supply coil, for receiving the coil signal of the power supply coil; and

a processor, coupled to the signal receiving module, for performing the following steps:

the processor calculates the first attenuation parameter according to a ratio of an average value of the first peak trigger voltage and the second peak trigger voltage to a difference value of the first peak trigger voltage and the second peak trigger voltage.

11. The power supply module of claim 10 wherein the first attenuation parameter is equal to the result of the addition of the first peak trigger voltage and the second peak trigger voltage divided by the result of the subtraction of the first peak trigger voltage and the second peak trigger voltage.

12. The power supply module of claim 10 wherein the first peak trigger voltage is close to and lower than a peak voltage of a corresponding first one of the plurality of peaks, and the second peak trigger voltage is close to and lower than a peak voltage of a corresponding second one of the plurality of peaks.

13. The power supply module of claim 10 wherein the processor performs the following steps to measure the peaks of the coil signal in the consecutive oscillation cycles of the coil signal to obtain the peak trigger voltages respectively:

setting a reference voltage at a trigger starting potential;

14. The power supply module of claim 13 wherein the processor further performs the following steps to measure the peaks of the coil signal in the consecutive oscillation cycles of the coil signal to obtain the peak trigger voltages respectively:

When the first previous peak trigger voltage is not obtained in the previous measurement period, the processor executes the following steps:

15. The power supply module of claim 10, wherein the processor performs the following steps to compare the first attenuation parameter with the first threshold value to determine whether a metal foreign object exists in the power transmission range of the inductive power supply:

when the first attenuation parameter is smaller than the first threshold value, the processor further performs the following steps:

the second attenuation parameter is compared with a second threshold value.

16. The power supply module of claim 15 wherein the first threshold is determined by adding a first value to a predetermined base threshold, and the second threshold is determined by adding a second value to the base threshold, wherein the second value is less than the first value.

17. The power module of claim 10, wherein the processor further performs the steps of: calculating a plurality of attenuation parameters according to the plurality of peak trigger voltages; and

18. The power supply module of claim 17 wherein the processor performs the following steps to average the attenuation parameters to determine whether metallic foreign objects are present within the power transmission range of the inductive power supply:

obtaining an average result generated by averaging the attenuation parameters;

comparing the average result with a basic critical value;