CN109143386B - Metal foreign object detection method for inductive power supply and its power supply module - Google Patents

Abstract

The present invention discloses a metal foreign body detection method, which is used for a power supply module of an inductive power supply, and the power supply module includes a power supply coil. The metal foreign body detection method includes interrupting at least one driving signal of the inductive power supply during a measurement period to stop driving the power supply coil to generate a coil signal of the power supply coil; measuring multiple wave peaks of the coil signal during multiple consecutive oscillation cycles of the coil signal to obtain multiple peak trigger voltages respectively; calculating a first attenuation parameter according to a first peak trigger voltage and a second peak trigger voltage among the multiple peak trigger voltages; and comparing the first attenuation parameter with a first critical value to determine whether there is a metal foreign body in a power transmission range of the inductive power supply.

Description

Metal foreign object detection method for inductive power supply and its power supply module

technical field

The invention relates to a metal foreign body detection method, in particular to a metal foreign body detection method which can be used in an inductive power supply.

Background technique

In the inductive power supply, the power supply end drives the power supply coil to resonate through the drive circuit, and then emits radio frequency electromagnetic waves, and then receives the electromagnetic wave energy through the coil of the power receiving end and conducts electrical conversion to generate DC power for the power receiving end device. If the electromagnetic energy sent by the power supply coil is applied to the metal body, it will have a heating effect on it. In the prior art, the inductive power supply can periodically interrupt the driving during the power transmission process for metal foreign object detection, which is determined 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 with the distance between the power supply end and the power receiving end. For example, when the coil is far away, the output is larger, and when the coil is closer, the output is smaller. As the output power changes, the amplitude of the coil signal also changes, so that the attenuation of the resonant signal is different when the coil is interrupted to drive. Therefore, when the power changes, the power supply needs to spend several detection cycles to adjust the voltage set by the comparator to track the signal peak value. If the coil voltage is unstable due to power or load, it is difficult to lock the signal peak to determine the attenuation slope.

In addition, in order to determine the decay slope, the driving signal needs to be interrupted for a period of time. However, interrupting the driving signal during the wireless charging process will reduce the overall power output capability. If the interruption time is too long, the power supply efficiency will be affected, and reconnecting the driving signal after the long interruption time is likely to cause excessive electromagnetic interference (Electromagnetic Interference, EMI). In the prior art, the comparator module obtains multiple peak voltage levels to determine the change of the multi-segment slope of the coil signal attenuation, so it needs to be interrupted for a long time. Taking Chinese Patent Application Publication No. CN 106094041 A as an example, it takes 7-15 coil oscillation cycles to complete the measurement of four peak voltage levels to determine the change of the attenuation slope.

In view of this, it is necessary to propose another metal foreign object detection method, which can complete the detection in a very short interruption driving time, and at the same time avoid power or load changes to affect the metal foreign object detection efficiency.

SUMMARY OF THE INVENTION

Therefore, the main purpose of the present invention is to provide a metal foreign object detection method that can complete the detection in an extremely short interruption driving time, and can complete the metal foreign object detection within 2-3 coil oscillation cycles at least. In addition, the metal foreign object detection method of the present invention can be judged by the attenuation ratio of the coil signal, which can solve the disadvantage that the attenuation slope judgment method of the prior art is easily affected by the coil amplitude and load.

The invention discloses a metal foreign object detection method for a power supply module of an inductive power supply. The power supply module includes a power supply coil, and the metal foreign object detection method includes interrupting the inductive power supply during a measurement period. to stop driving the power supply coil to generate a coil signal of the power supply coil; measure multiple peaks of the coil signal in multiple consecutive oscillation cycles of the coil signal to obtain multiple peaks respectively triggering voltage; calculating a first attenuation parameter according to a first peak triggering voltage and a second peak triggering voltage among the plurality of peak triggering voltages; and comparing the first attenuation parameter and a first threshold to determine the Whether there is a metal foreign object within a power transmission range of the inductive power supply.

The invention also discloses a power supply module for an inductive power supply, which is used to perform a metal foreign object detection method. The power supply module includes a power supply coil, a resonance capacitor, at least one power supply driving unit, and a signal receiving module. and a processor. The resonant capacitor is coupled to the power supply coil and used for resonating with the power supply coil. 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 drive signal to the power supply coil to drive the power supply coil to generate energy, and to interrupt the at least one drive signal during a measurement period to generate energy. Stop driving the power supply coil to generate a coil signal of the power supply coil. The signal receiving module is coupled to the power supply coil for receiving the coil signal of the power supply coil. The processor is coupled to the signal receiving module, and is used for executing the following steps: measuring a plurality of peaks of the coil signal in a plurality of consecutive oscillation periods of the coil signal to obtain a plurality of peak trigger voltages respectively; a first peak trigger voltage and a second peak trigger voltage among the peak trigger voltages to calculate a first attenuation parameter; and compare the first attenuation parameter with a first threshold to determine a Whether there is any metallic foreign object within the power transmission range.

The invention also discloses a metal foreign object detection method, which is used for a power supply module of an inductive power supply, the power supply module includes a power supply coil, and the metal foreign object detection method includes obtaining the corresponding measurement in the previous measurement period. A previous peak trigger voltage is set as a reference voltage value; during a measurement period, at least one driving signal of the inductive power supply is interrupted to stop driving the power supply coil, so as to generate a coil signal of the power supply coil; Measure a first peak of the coil signal during an oscillation period of the coil signal to obtain a first peak trigger voltage; compare the first peak trigger voltage with the reference voltage value; and when the first peak trigger voltage is equal to When it is close to the reference voltage value, it is determined that there is no metal foreign object within a power transmission range of the inductive power supply.

Description of drawings

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

FIG. 2 is a schematic diagram of a metal foreign body detection process according to an embodiment of the present invention.

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

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

FIG. 8 is a schematic diagram of another metal foreign body detection process according to an embodiment of the present invention.

FIG. 9 is a schematic diagram of discriminating metal foreign objects by a peak trigger voltage during a measurement period according to an embodiment of the present invention.

Among them, the reference numerals are described as follows:

100 Inductive Power Supply

1 Power supply module

10 Power Supply

111 processors

112 Clock Generator

113 Voltage generating devices

114 Comparator

120 signal receiving module

121, 122 Power supply drive unit

130 Voltage divider circuit

131, 132 divider resistor

141, 142 Resonant capacitor

16 Power supply coil

161, 261 Magnetic conductors

D1, D2 drive signal

C1 coil signal

2 Power receiving module

21 Load cell

22 Capacitor

230 Rectifier circuit

241, 242 Resonant capacitor

26 Power receiving coil

3 Metal foreign bodies

20, 80 Metal foreign body detection process

200～222, 800～818 steps

CP1 Comparison Results

A, B, C, D, E, F peaks

VB, VC, VD, VE, VF Peak trigger voltage

V0_B, V0_C, V0_D, V0_E, V0_F Trigger start potential

PAR1 first decay parameter

PAR2 Second attenuation parameter

PAR3 third attenuation parameter

PAR4 Fourth attenuation parameter

TH1 first threshold

TH2 second threshold

TH3 third threshold

THO base threshold

Detailed ways

Please refer to FIG. 1 , which is a schematic diagram of an inductive power supply 100 according to an embodiment of the present 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 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 C-L-C structure. The power supply coil 16 can be used to transmit electromagnetic energy to the power receiving module 2 for power supply, and the resonant capacitors 141 and 142 are respectively coupled to both ends of the power supply coil 16 and can be used to resonate with the power supply coil 16 during power supply. In addition, in the power supply module 1 , a magnetic conductor 161 made of magnetic material can be selectively used to improve the electromagnetic induction capability of the power supply coil 16 and prevent electromagnetic energy from affecting objects in the direction of the non-inductive surface of the coil.

In order to control the operation of the power supply coil 16 and the resonant capacitors 141 and 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 supply driving units 121 and 122 are coupled to the power supply coil 16 and the resonant capacitors 141 and 142, and can respectively send drive signals D1 and D2 to the power supply coil 16, which can receive the control of the processor 111 to drive the power supply coil 16 to generate and transmit energy. When both the power supply driving units 121 and 122 operate at the same time, full-bridge driving can be performed. In some embodiments, only one of the power supply driving units 121 and 122 may be turned on, or only one power supply driving unit 121 or 122 may be arranged to perform half-bridge driving. The clock generator 112 is coupled to the power supply driving units 121 and 122, and can be used to control the power supply driving units 121 and 122 to send the driving signals D1 and D2. The clock generator 112 may be a pulse width modulation generator (PWM generator) or other types of clock generators, and is used for outputting a clock signal to the power supply driving units 121 and 122 . The processor 111 can receive the relevant information of the coil signal C1 on the power supply coil 16 (that is, the voltage signal between the power supply coil 16 and the resonant capacitor 142 ), such as the resonant frequency or attenuation amplitude of the coil signal C1, and determine the metal foreign body accordingly. does it exist. The processor 111 may be a central processing unit (Central Processing Unit, CPU), a microprocessor (microprocessor), a microcontroller unit (Micro Controller Unit, MCU), or other types of processing devices or computing devices. The signal receiving module 120 can be used to track the resonance frequency and the peak value of the coil signal C1, and provide the relevant information of the resonance frequency and the peak value to the processor 111 for subsequent interpretation. The voltage dividing circuit 130 includes voltage dividing resistors 131 and 132 , which can attenuate the coil signal C1 on the power supply coil 16 and then output it to the processor 111 and the signal receiving module 120 . In some embodiments, if circuits such as the processor 111 and the signal receiving module 120 have sufficient withstand voltage, the voltage divider circuit 130 may not be used, and the processor 111 directly receives the coil signal C1 on the power supply coil 16 . As for other possible components or modules, such as a power supply unit, a display unit, etc., which may be increased or decreased depending on the system requirements, they are omitted and not shown without affecting the description of this 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 can be a digital to analog converter (DAC), which can receive a reference voltage information from the processor 111, convert it into an analog voltage and output it. One input end of the comparator 114 can receive the reference voltage, and the other input end can receive the coil signal C1 from the power supply coil 16 , which can compare the coil signal C1 with the reference voltage, and the processor 111 makes subsequent judgments according to the result of the above comparison and signal processing. It should be noted that, the signal receiving module 120 can also be integrated inside the processor 111, but is not limited to this.

Please continue to refer to Figure 1. The power receiving module 2 includes a load unit 21 , a capacitor 22 , a rectifier circuit 230 , a power receiving coil 26 and resonance capacitors 241 and 242 . In the power receiving module 2, a magnetic conductor 261 made of magnetic material can also be selectively used to improve the electromagnetic induction capability of the power receiving coil 26, and at the same time prevent electromagnetic energy from affecting objects in the direction of the non-inductive surface of the coil. The power receiving coil 26 can be used to receive power from the power supply coil 16 and transmit the received power to the rectifier circuit 230 for rectification. The capacitor 22 can 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., can be increased or decreased depending on the system requirements, so they are omitted and omitted without affecting the description of this embodiment. Show.

In addition, a metal foreign object 3 is not included in the inductive power supply 100, but is shown between the power supply module 1 and the power reception module 2 in FIG. 1 for convenience of description. When the metal foreign object 3 is located within the power transmission range of the inductive power supply 100 , it may receive the electromagnetic energy sent by the power supply module 1 and generate heat. The metal foreign object detection method of the present invention can be used to determine whether there is a metal foreign object 3 within the power transmission range of the inductive power supply 100 , and stop power transmission when it is determined that the metal foreign object 3 exists.

Different from the prior art, the power supply module judges the metal foreign body by measuring the change of the coil attenuation slope, the present invention judges the metal foreign body by measuring the voltage attenuation ratio of the coil signal. Please refer to FIG. 2 . FIG. 2 is a schematic diagram of a metal foreign object detection process 20 according to an embodiment of the present invention. As shown in FIG. 2 , the metal foreign object detection process 20 can be used for the power supply end of an inductive power supply (such as the power supply module 1 of the inductive power supply 100 in FIG. 1 ), which includes the following steps:

Step 200: Start.

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

Step 204 : Measure two peaks of the coil signal C1 in two consecutive oscillation periods of the coil signal C1 to obtain two peak trigger voltages respectively.

Step 206: Calculate an attenuation parameter according to the two peak trigger voltages.

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

Step 210: Determine 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 : Measure the peak value of the coil signal C1 in the next oscillation period of the coil signal C1 to obtain a peak trigger voltage.

Step 214: Calculate an attenuation parameter according to the peak trigger voltage and the peak trigger voltage obtained in the previous oscillation period.

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

Step 218 : Determine that there is no metal foreign object 3 within the power transmission range of the inductive power supply 100 .

Step 220 : It is determined that there is a metal foreign object 3 within the power transmission range of the inductive power supply 100 .

Step 222: End.

According to the metal foreign object detection process 20 , in the power supply module 1 of the inductive power supply 100 , the driving signals D1 and D2 will be interrupted for a period of time during the driving process. At this time, the power supply driving units 121 and 122 will stop the power supply coil 16 drive. When the power supply coil 16 stops driving, since there is still energy between the power supply coil 16 and the resonance capacitors 141 and 142 , the coil signal C1 will continue to oscillate and gradually attenuate. As shown in FIG. 3 , when the driving is stopped, the driving signals D1 and D2 stay at a high potential and a low potential for a period of time, respectively. At this time, the coil signal C1 exhibits an oscillating and gradually attenuating waveform, and then the power supply and driving units 121 and 122 are reconnected. The power supply coil 16 is driven again to output electric power by outputting the square wave driving signals D1 and D2. In other embodiments, the driving signals D1 and D2 can also be controlled to stay at a high level or at a low level at the same time to stop driving, but not limited to this. The above-mentioned interruption period of the driving signals D1 and D2 is used to measure the resonance of the coil signal C1 to detect the metal foreign object 3 , which is hereinafter referred to as the measurement period for convenience of description.

During the measurement period, there are multiple consecutive oscillation periods on the coil signal C1, and the processor 111 can measure the peaks of the coil signal C1 in the multiple oscillation periods to obtain multiple peak trigger voltages respectively. Please refer to FIG. 4 . FIG. 4 is a schematic diagram of obtaining peak trigger voltages VB and VC during a measurement period according to an embodiment of the present invention. As shown in FIG. 4 , the coil signal C1 includes three peaks A, B and C during the measurement period. 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 supply coil 16 itself. Therefore, the peak value of the peak A is The height may not have reached the height of natural oscillation. In this case, in order to avoid the distortion of the determination of the metal foreign object 3 due to the influence of the driving signals D1 and D2, the peak trigger voltage measurement of the peak A can be discarded, and only the peak trigger voltages VB and VC of the peaks B and C can be measured.

During the oscillation period in which the wave peak is to be measured, the processor 111 can set a reference voltage (shown in dotted lines in FIG. 4 ), and output the reference voltage to the comparator 114 through the voltage generating device 113 , and the comparator 114 compares the reference voltage with the reference voltage. The coil signal C1 generates a comparison result CP1. Specifically, before entering the oscillation period corresponding to the peak B, the processor 111 may first set the reference voltage to a trigger start potential V0_B. Then, when the level of the coil signal C1 rises to exceed the reference voltage and a trigger signal appears at the output of the comparator 114 (ie, the comparison result CP1 shows a high level), the processor 111 can control the reference voltage to gradually increase. When the reference voltage rises to exceed the level of the coil signal C1, it can be determined that the trigger signal ends (that is, the comparison result CP1 returns to a low level). At this time, the processor 111 can obtain the level of the reference voltage as the peak trigger corresponding to the peak B voltage VB. Similarly, in the oscillation period corresponding to the peak C, the processor 111 may first set the reference voltage to a trigger start potential V0_C, and then obtain the peak trigger voltage VC corresponding to the peak C in the same manner.

Next, the processor 111 can calculate 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 the average value of the peak trigger voltage VB and the peak trigger voltage VC to the difference between the peak trigger voltage VB and the peak trigger voltage VC. In one embodiment, the first attenuation parameter PAR1 can be obtained 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. The detailed calculation method is as follows:

It is worth noting that the Chinese Patent Application Publication No. CN 106094041 A uses the change of the attenuation slope to determine the metal foreign matter, that is, the change of the attenuation amount. However, in the absence of metal foreign matter, when the output power is high (that is, the coil signal C1 has a large amplitude), the attenuation after the coil is interrupted and driven is large; when the output power is low (that is, the coil signal C1 has a small amplitude) ), the attenuation after the coil is interrupted and driven is small. That is, the ratio of attenuation to output power will be approximately the same. For example, in the absence of metal foreign matter, 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 50 units. is 45 units of voltage, the two have different amounts of peak attenuation. Therefore, the present invention uses the ratio of the average value or sum of the peak trigger voltage to the difference (that is, the attenuation) of the peak trigger voltage to calculate the attenuation parameter, which can exclude the influence of different output powers on the attenuation of the coil signal, thereby achieving a more effective Metal foreign body judgment. In this example, the larger the attenuation parameter is, the slower the signal attenuation speed is, that is, the lower the possibility of the existence of metal foreign objects; the smaller the attenuation parameter, the faster the signal attenuation speed is, that is, the higher the possibility of the existence of metal foreign objects.

In addition, it should be noted that the above-mentioned peak trigger voltage is often not equal to the peak voltage of the corresponding peak. In fact, the peak trigger voltage is slightly lower than the peak voltage of the corresponding peak. It can be seen from FIG. 4 that the peak trigger voltage VB is close to and slightly lower than the peak voltage of peak B, and the peak trigger voltage VC is close to and slightly lower than the peak voltage of peak C. Since the trigger start potentials V0_B and V0_C can be set at a voltage level slightly lower than that of the peak B and the peak C, respectively, the rising reference voltage and the coil signal C1 cross on the right side of the peak, so that the obtained value according to the reference voltage The peak trigger voltages VB and VC are also slightly lower than and close to their corresponding peak voltages. In addition, it can be seen from the above calculation method of the attenuation parameter that the size of the attenuation parameter is mainly affected by the attenuation ratio. Therefore, using the peak trigger voltage with a value slightly lower than the peak voltage as the calculation reference, the obtained metal foreign matter judgment results are still roughly the same as Judgment result based on peak voltage. As long as the attenuation parameter can reflect the attenuation amount or attenuation ratio, it can be used to discriminate metal foreign objects.

As mentioned above, the first attenuation parameter PAR1 is equal to the result of adding the peak trigger voltage VB and the peak trigger voltage VC divided by the result of the subtraction of the peak trigger voltage VB and 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 inductive power supply 100 is within a power transmission range Metal foreign body 3 is present. In one embodiment, when the first attenuation parameter PAR1 is greater than the first threshold value TH1, it can be determined that there is no metal foreign object 3 within the power transmission range of the inductive power supply 100; when the first attenuation parameter PAR1 is less than the first threshold value When TH1, further follow-up judgment is performed. In an inductive power supply system, there is often a lot of noise at the power supply or load end, which is easy to interfere with the analysis and detection of the coil signal. Therefore, in order to accurately identify metal foreign objects, it is necessary to continuously obtain data or results that are judged as metal foreign objects for many times to avoid Noise interference causes misjudgment of metal foreign objects, so that the power output is erroneously turned off.

In one embodiment, the processor 111 may set a basic threshold THO. During the product testing process of the inductive power supply, there may be variability in attenuation parameters between different products and different environments. The basic threshold THO can be set according to the lowest attenuation parameter measured without metal foreign matter. Preferably, the basic threshold value THO can be set to a relatively low value, which has a relatively loose judgment criterion, so as to avoid noise interference from being misjudged as the presence of metal foreign objects. Next, the processor 111 may add different values to the basic threshold value THO to obtain a plurality of threshold values, such as the first threshold value TH1 , the second threshold value TH2 , and the third threshold value TH3 . The processor 111 can compare the first attenuation parameter PAR1, the second attenuation parameter PAR2, the third attenuation parameter PAR3 and the fourth attenuation parameter PAR4 obtained in a measurement period with the first threshold TH1, the second threshold TH2, the third threshold The threshold value TH3 and the basic threshold value THO are compared to determine the metal foreign matter 3 . For example, the processor can set the basic threshold value THO to 150, and set the first threshold value TH1 to the basic threshold value TH0 = 150 plus 30, that is, 180; and set the second threshold value TH2 to the basic threshold value THO=150 plus 20, that is, 170; the third threshold TH3 is set as the basic threshold TH0=150 plus 10, that is, 160. The first threshold TH1 is greater than the second threshold TH2, and the second threshold TH2 is greater than the third threshold TH3.

First, the processor 111 compares the first attenuation parameter PAR1 with the first threshold TH1. In an embodiment (as shown in Table 1), the processor 111 can obtain that the peak trigger voltage VB is 1000 unit voltage and the peak trigger voltage VC is 990 unit voltage, and the first attenuation parameter PAR1 is 199 after calculation. Since the first attenuation parameter PAR1=199 is greater than the first threshold value TH1=180, which means that it is much larger than the basic threshold value THO, the processor 111 directly determines that the foreign metal object 3 does not exist.

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

Table I

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, indicating that the probability of the existence of the metal foreign body 3 is extremely low, which is a very safe state, so the system directly determines that the metal foreign body 3 does not exist. . In this case, the processor 111 only needs to measure two oscillation periods to complete the identification of the metal foreign object 3 . In other words, the measurement period in which the driving signals D1 and D2 are interrupted only needs to include 3 oscillation periods, wherein the oscillation period corresponding to the peak A is not measured, and the measurement is completed within the oscillation period corresponding to the peaks B and C, and the first oscillation period is obtained. After the attenuation parameter PAR1, the identification of the metal foreign object 3 can be completed.

In one embodiment, the first attenuation parameter PAR1 is smaller than the first threshold value TH1 , and at this time, the processor 111 further performs the subsequent determination of the metal foreign object 3 , as shown in Table 2.

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

Table II

Specifically, the processor 111 first compares the first attenuation parameter PAR1 with the first threshold TH1. After determining that the first attenuation parameter PAR1=166 is smaller than the first threshold value TH1=180, the processor 111 may measure the next oscillation period of the coil signal C1 (corresponding to the oscillation period of 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 potential V0_D, and obtain the peak trigger voltage VD corresponding to the peak D according to the above method. Next, the processor 111 can calculate a second attenuation parameter PAR2 according to the peak trigger voltage VC and the peak trigger voltage VD. In detail, the processor 111 can calculate the result of adding the peak trigger voltage VC and the peak trigger voltage VD divided by the result of subtracting the peak trigger voltage VC and the peak trigger voltage VD to obtain the second attenuation parameter PAR2. The detailed calculation method is as follows. :

In this example, the peak trigger voltage VC is 988 unit voltages and the peak trigger voltage VD is 977 unit voltages. After calculation, the second attenuation parameter PAR2 is 179 (rounded off after the decimal point). Next, the processor 111 compares the second attenuation parameter PAR2 with the second threshold value TH2, and determines that the second attenuation parameter PAR2=179 is greater than the second threshold value TH2=170. In this case, the processor 111 stops measuring the subsequent oscillation period during the measurement period, and at the same time averages the obtained first attenuation parameter PAR1 and the second attenuation parameter PAR2, and compares the above-mentioned average result with the basic threshold THO , in order to discriminate metal foreign objects 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 THO, so the processor 111 determines that there is no metal foreign object 3 within 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 value TH2. At this time, the processor 111 further performs the subsequent determination of the metal foreign object 3, as shown in Table 3.

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

Table 3

Specifically, the processor 111 first compares the first attenuation parameter PAR1 with the first threshold TH1. After judging that the first attenuation parameter PAR1=142 is smaller than the first threshold TH1=180, the processor 111 can measure the next oscillation period of the coil signal C1 (corresponding to the oscillation period of the peak D) to obtain the second attenuation parameter PAR2, and Compare the second attenuation parameter PAR2 with the second threshold TH2. Next, after judging that the second attenuation parameter PAR2=163 is smaller than the second threshold value TH2=170, the processor 111 can measure the next oscillation period of the coil signal C1 (corresponding to the oscillation period of the peak E). 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 potential V0_E, and obtain the peak trigger voltage VE corresponding to the peak E according to the above method. Next, the processor 111 can calculate a third attenuation parameter PAR3 according to the peak trigger voltage VD and the peak trigger voltage VE. Specifically, the processor 111 can calculate the result of adding the peak trigger voltage VD and the peak trigger voltage VE divided by the result of the subtraction of the peak trigger voltage VD and the peak trigger voltage VE to obtain the third attenuation parameter PAR3. The detailed calculation method is as follows: :

In this example, the peak trigger voltage VD is 974 units of voltage and the peak trigger voltage VE is 962 units of voltage. After calculation, the third attenuation parameter PAR3 is 161 (rounded off after the decimal point). Next, the processor 111 compares the third attenuation parameter PAR3 with the third threshold value TH3, and determines that the third attenuation parameter PAR3=161 is greater than the third threshold value TH2=160. In this case, the processor 111 stops measuring the subsequent oscillation period during the measurement period, and at the same time averages the obtained first attenuation parameter PAR1, second attenuation parameter PAR2 and third attenuation parameter PAR3, and compares the above average result with The basic threshold value THO is compared for the determination of metal foreign matter 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 THO, so the processor 111 determines that there is no metal in the power transmission range of the inductive power supply 100 Foreign body 3.

In another embodiment, the third attenuation parameter PAR3 may also be smaller than the third threshold value TH3. At this time, the processor 111 further performs the subsequent determination of the metal foreign object 3, as shown in Table 4.

crest/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

Table 4

Specifically, the processor 111 first compares the first attenuation parameter PAR1 with the first threshold TH1. After judging that the first attenuation parameter PAR1=124 is smaller than the first threshold TH1=180, the processor 111 can measure the next oscillation period of the coil signal C1 (corresponding to the oscillation period of the peak D) to obtain the second attenuation parameter PAR2, and Compare the second attenuation parameter PAR2 with the second threshold TH2. Next, after judging that the second attenuation parameter PAR2=122 is smaller than the second threshold value TH2=170, the processor 111 can measure the next oscillation period of the coil signal C1 (corresponding to the oscillation period of the peak E) to obtain the third attenuation parameter PAR3 , and compare the third attenuation parameter PAR3 with the third threshold TH3. Next, after judging that the third attenuation parameter PAR3=120 is smaller than the third threshold value TH3=160, the processor 111 can measure the next oscillation period of the coil signal C1 (corresponding to the oscillation period of the peak F). 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 potential V0_F, and obtain the peak trigger voltage VF corresponding to the peak F according to the above method. Next, the processor 111 can calculate a fourth attenuation parameter PAR4 according to the peak trigger voltage VE and the peak trigger voltage VF. Specifically, the processor 111 can calculate the result of adding the peak trigger voltage VE and the peak trigger voltage VF by dividing the result of the subtraction of the peak trigger voltage VE and the peak trigger voltage VF to obtain the fourth attenuation parameter PAR4. The detailed calculation method is as follows: :

In this example, the peak trigger voltage VE is 952 units of voltage and the peak trigger voltage VF is 936 units of voltage, and the fourth attenuation parameter PAR4 is 118 after calculation. Since the number of oscillation periods measured by the processor 111 during this measurement period has reached a predetermined number, the processor 111 can perform the first attenuation parameter PAR1, the second attenuation parameter PAR2, the third attenuation parameter PAR3 and the fourth attenuation The parameter PAR4 is averaged, and the above averaged result is compared with the basic threshold value THO for the determination of metal foreign body 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 less than the basic threshold THO, so the processor 111 determines the power of the inductive power supply 100 A metallic foreign object 3 is present within the transmission range.

In the above-mentioned embodiment, only 3 to 6 oscillation periods need to be included in the measurement period when the driving signals D1 and D2 are interrupted, and the identification of the metal foreign object 3 can be completed. Compared with the Chinese Patent Application Publication No. CN 106094041 A, which requires 7-15 coil oscillation cycles to complete the measurement of the four peak voltage levels to determine the change of the attenuation slope, the metal foreign body detection method of the present invention can be used in less It is completed within the time limit, thereby shortening the interruption time of the driving signals D1 and D2. Generally speaking, when the metal foreign body 3 does not exist and the determination of the coil signal C1 is not disturbed by noise, the obtained first attenuation parameter PAR1 is often much larger than the basic threshold THO. At this time, only two oscillation periods need to be measured, namely The identification of the metal foreign object 3 can be completed, and after the identification is completed, the power supply driving units 121 and 122 can immediately join the lines to activate the driving signals D1 and D2 , as shown in FIG. 3 . On the other hand, more oscillation periods need to be measured only when metal proximity or noise interference reduces the attenuation parameter. In other words, the smaller the value of the attenuation parameter, the higher the possibility of the presence of metal foreign matter, and the number of measured oscillation periods also increases simultaneously. Finally, no matter how many oscillation periods are measured or how many attenuation parameters are obtained, the processor 111 averages the obtained attenuation parameters, and compares the averaged result with the basic threshold THO to determine whether the foreign metal object 3 exists. Generally speaking, when the coil stops driving, its signal is in a state of natural resonance. If there is no metal foreign matter, the change in the attenuation slope of the coil signal relative to the value of the signal amplitude is extremely small. Since each damping parameter is calculated in the same way based on the peak trigger voltage of the adjacent oscillation period, the numerical value of the damping parameter is quite stable. In an inductive power supply system, the judgment of the signal must be affected by the power supply or circuit noise, but most power supply/circuit noise will only show a small value jump in the attenuation parameter. At this time, the attenuation parameter is often much larger than the aforementioned critical value. without affecting the judgment result. On the contrary, when metal foreign matter appears, the peak trigger voltage will decay rapidly. Through the calculation method of dividing the above addition result by the subtraction result, the attenuation parameter will drop rapidly, which can effectively detect and discriminate metal foreign matter.

In each measurement period, the number of oscillation cycles to be measured can be determined according to the comparison result between the attenuation parameter and the corresponding critical value, and the average value of all the attenuation parameters can be obtained to discriminate metal foreign objects. Generally speaking, when any one of the first, second and third attenuation parameters PAR1 to PAR3 is greater than the corresponding threshold, the calculation of the last fourth attenuation parameter PAR4 is not performed. Since the first, second and third thresholds TH1-TH3 are all greater than the basic threshold THO, the average value of the first three attenuation parameters PAR1-PAR3 is usually greater than the basic threshold without calculating the fourth attenuation parameter PAR4 The value of THO is used to obtain the determination result that the metallic foreign matter 3 does not exist. In this case, the processor 111 can also determine the number of acquired attenuation parameters or the number of measured oscillation periods, and only when the number of acquired attenuation parameters reaches a preset value (for example, four attenuation parameters), calculates the number of attenuation parameters. The average value is used to determine the metal foreign object 3 ; if the acquired number of attenuation parameters does not reach the preset value, the processor 111 directly determines that the metal foreign object 3 does not exist.

In addition, in order to improve the determination accuracy and avoid the power output being turned off due to wrong determination, the processor 111 may set a metal foreign object counter. If the average value of attenuation parameters obtained during a measurement period is less than the basic threshold value, the metal foreign matter counter can be increased by one. When the metal foreign object counter reaches a certain value within a predetermined period, it is determined that the metal foreign object 3 exists. Alternatively, it can also be determined that the metal foreign body 3 exists when the average value of the attenuation parameter obtained in several consecutive measurement periods is less 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 potential, and controls the reference voltage to rise when the output terminal of the comparator 114 is triggered, and then obtains the reference voltage when the trigger ends. The level of the reference voltage is used as the peak trigger voltage. In order for the peak trigger voltage to effectively reflect the voltage level of the corresponding peak, the trigger start potential should be set close to and slightly lower than the peak voltage for successful triggering and at the same time the peak trigger voltage is close to the peak voltage level. If the trigger start potential is set too high, the trigger start potential may be higher than the peak voltage and the trigger cannot be successfully triggered; if the trigger start potential is set too low, the trigger may be successfully triggered but the peak trigger voltage may be too low It cannot reflect the actual peak voltage.

In one embodiment, the processor 111 may calculate the trigger start potential used in this measurement period according to a corresponding previous peak trigger voltage obtained in the previous measurement period, for example, subtract a predetermined value from the previous peak trigger voltage. The value obtained from the voltage value 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 units of voltage, the trigger start potential V0_B of this measurement period can be set to 900 units of voltage (that is, 1000 minus 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 potential V0_C during this measurement period can be set to 880 units of voltage (ie 980 minus the preset voltage value of 100). According to the peak trigger voltage in the previous measurement period, the processor 111 can know the possible level of the peak voltage, so as to set the trigger start potential at a slightly lower level. Setting a lower trigger start potential can increase the probability of triggering. Unless the peak voltage drops rapidly, triggering can be successful in most cases and the metal foreign object judgment result can be obtained.

The way of judging the peak voltage level of Chinese Patent Application Publication No. CN 106094041 A is to judge whether the reference voltage needs to be increased or decreased according to the result of whether there is a trigger in the previous measurement period, and the reference voltage needs to be increased or decreased in several measurement periods. It is judged that the reference voltage has been locked at the peak voltage level without triggering. Therefore, when the load and output power do not change, multiple 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 improve the probability of triggering, and as long as triggering occurs, the attenuation parameter can be calculated immediately to determine the metal foreign matter. Therefore, , the present invention can quickly complete the discrimination without spending multiple measurement periods to lock to the peak voltage level. In addition, during the determination process, the trigger start potential can still be adjusted to a better level. For example, during this measurement period, the trigger start potential V0_B is set to 900 units of voltage, and the trigger ends when the reference voltage rises to 910 units of voltage, It represents that the peak value of the trigger voltage VB drops to 910 units of voltage. In this case, the trigger start potential V0_B can be set to 810 units of voltage (ie, 910 minus the preset voltage value of 100) in the next measurement period to achieve A better trigger effect also increases the chance of a successful trigger.

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, in 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 subsequent measurement is not required. Oscillation period and calculate other decay parameters. However, during this measurement period, the processor 111 determines that the first attenuation parameter PAR1 is smaller than the first threshold value TH1 and the subsequent oscillation period needs to be measured. In other words, the trigger start potential V0_D corresponding to the peak D needs to be obtained during this measurement period, but the oscillation period of the peak D was not measured during the previous measurement period, so there is no peak trigger voltage VD as the basis for estimating the trigger start potential V0_D this time. . In this case, the processor 111 can use another previous peak trigger voltage (ie, 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 the peak value corresponding to the peak D The trigger voltage VD may be lower than the amplitude of the peak trigger voltage VC, and then the trigger start potential V0_D is calculated. 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 accordingly, and the trigger start potential V0_D is set at 770 units (that is, 870 minus the predetermined value). Set the voltage value to 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 and the peak trigger voltage VC is 90 units, it can be estimated that the peak trigger voltage VD of the peak D is about 80 units, and then the trigger start potential V0_D is set as 70 units of voltage to detect the actual peak trigger voltage VD.

Generally speaking, if the oscillation period corresponding to the peak D is not measured in the previous measurement period, the record representing the previous peak trigger voltage corresponding to the peak D may come from the measurement results of a longer period of time ago. However, changes in load and/or power output may occur during the power supply of the inductive power supply 100, resulting in a large change in the peak voltage on the coil signal C1, which may be as high as tens or hundreds of times. In this case, the peak trigger voltage record before a long period of time is often of no reference value. Therefore, using the peak trigger voltage of the previous oscillation period within the same measurement period as the basis, a more suitable trigger start potential can be obtained, thereby improving the The probability of successful triggering and obtaining attenuation parameters and metal foreign object judgment results.

It is worth noting that the aforementioned methods cannot successfully trigger and obtain attenuation parameters in every measurement period. If no triggering occurs in one oscillation period and the corresponding peak trigger voltage cannot be obtained, the processor 111 discards the calculation and judgment results in the measurement period, and at the same time lowers the trigger start potential to increase the successful triggering in the next measurement period probability. In addition, in order to effectively obtain the peak trigger voltage, the processor 111 can first measure the coil resonance frequency, and obtain the position interval where the peak may occur in each resonance cycle. If no trigger occurs within this interval, it means that the trigger start potential is too high, so the processor 111 reduces the trigger start potential in the next measurement period, and tries to trigger again to obtain the corresponding peak trigger voltage.

It can be seen from the above that the present invention can measure the coil signal during the measurement period when the driving signal is interrupted to obtain the peak trigger voltage corresponding to a plurality of peaks, and obtain the peak trigger voltage according to the ratio of the average value of the two adjacent peak trigger voltages to the difference thereof. Calculate the attenuation parameter, and then compare the attenuation parameter with the corresponding threshold value to determine whether more peak trigger voltages of the peaks need to be obtained to perform subsequent judgments, and at the same time, the judgment of metal foreign objects is performed. The processor may set the reference voltage at a trigger start potential, and control the reference voltage to gradually increase when a trigger occurs, thereby obtaining a peak trigger voltage. Those skilled in the art can make modifications or changes accordingly, but are not limited to this. For example, in the above-mentioned embodiment, a maximum of 5 oscillation periods are measured in a measurement period to obtain 5 peak trigger voltages to calculate 4 attenuation parameters. In other embodiments, the maximum number of times of measuring the oscillation period and the maximum number of obtained attenuation parameters can be adjusted according to system requirements, but not limited to this. In addition, in the above embodiments, the values of the peak trigger voltage and the trigger start potential 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 can be realized by a digital-to-analog converter, and the above-mentioned unit voltage can 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, according to Different specifications of digital-to-analog converters may have different values for the peak trigger voltage and trigger start potential. For example, if the voltage generating device 113 is a 12-bit digital-to-analog converter, it can receive digital values from 0 to 4095 and generate the 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 the level at which the reference voltage rises from the trigger start potential to the trigger end, and the processor 111 can adjust the speed of the reference voltage rise. For example, the processor 111 can control the reference voltage to rise at a fixed speed, and Adjust the rising speed to an optimal value so that the level at the end of the trigger can effectively reflect the level of the peak voltage.

The metal foreign object detection method of the present invention can effectively reduce the interruption time of the driving signal, so as to reduce the influence of interruption of driving on the power supply. Therefore, the process of judging metal foreign objects must be completed in the shortest time possible. In the above embodiment, it only needs to measure 2 oscillation periods at least to complete the identification of metal foreign objects, and together with the oscillation period of the first wave peak discarded, the driving signal only needs to be interrupted for at least three oscillation periods. In another embodiment, the interruption time of the driving signal can be further reduced.

Please refer to FIG. 8 , which is a schematic diagram of another metal foreign object detection process 80 according to an embodiment of the present invention. As shown in FIG. 8 , the metal foreign object detection process 80 can be used for the power supply end of an inductive power supply (such as the power supply module 1 of the inductive power supply 100 in FIG. 1 ), which includes the following steps:

Step 800: Start.

Step 802 : Obtain a corresponding previous peak trigger voltage measured in the previous measurement period, and set it as a reference voltage value.

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

Step 806: Measure a first peak of the coil signal C1 within an oscillation period of the coil signal C1 to obtain a first peak trigger voltage.

Step 808 : Compare the first peak trigger voltage with the reference voltage value, and determine 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 : It is determined that there is no metal foreign object 3 within a power transmission range of the inductive power supply 100 , and then step 818 is executed.

Step 812 : Measure a second peak of the coil signal C1 in the next oscillation period of the coil signal C1 to obtain a second peak trigger voltage.

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

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

Step 818: End.

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

For example, please refer to FIG. 9 . FIG. 9 is a schematic diagram of discriminating metal foreign objects by a peak trigger voltage VB during a measurement period according to an embodiment of the present invention. As shown in FIG. 9 , the coil signal C1 includes only two peaks A and B during the measurement period. Similarly, in order to avoid distortion of the determination of the metal foreign object 3 due to the influence of the driving signals D1 and D2 , the peak trigger voltage measurement of the peak A can be discarded. Next, in the oscillation period corresponding to the peak B, the processor 111 may set the reference voltage to a trigger start potential V0_B, and obtain the peak trigger voltage VB corresponding to the peak B according to the above method.

It is worth noting that, in the previous measurement period, the processor 111 can first measure a corresponding previous peak trigger voltage, that is, 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. At the same time, only the peak trigger voltage VB was obtained in the previous measurement period and the judgment result indicated that no metal foreign matter 3 existed; or, only the peak trigger voltage VB and VC were obtained in the previous measurement period, and the calculated first attenuation parameter PAR1 was greater than the A threshold value TH1 indicates that there is no metal foreign matter 3 present. Next, during the current measurement period, the processor 111 only needs to obtain the peak trigger voltage VB corresponding to the peak B to complete the identification of the metal foreign object 3 . Specifically, the processor 111 can compare the peak trigger voltage VB with the reference voltage value, and when the peak trigger voltage VB is equal to or close to the reference voltage value, it can determine that there is no metal foreign matter within the power transmission range of the inductive power supply 100 3. In this case, after the peak trigger voltage VB is measured, the power supply driving units 121 and 122 can be reconnected to drive the power supply coil 16 to output power again through the driving signals D1 and D2.

Generally speaking, when there is no metal foreign matter and the output power of the coil and the load state are unchanged, the peak trigger voltage VB corresponding to the peak B is also roughly unchanged. Conversely, when a metal foreign object 3 enters the power transmission range of the inductive power supply 100 , if other conditions (such as coil output power and load) remain unchanged, the peak trigger voltage VB will be greatly reduced by the metal foreign object 3 . In this case, the processor 111 only needs to measure the peak trigger voltage VB to complete the identification of the metal foreign object 3 . In this way, the measurement period in which the driving signals D1 and D2 are interrupted only needs to include at least 2 oscillation periods, wherein the oscillation period corresponding to the peak A is not measured, and the measurement is completed and obtained in the oscillation period corresponding to the peak B. After the peak trigger voltage VB is obtained, the identification of the metal 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 means that there is no metal foreign matter within 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.

It should be noted that the above determination of being equal to or close to can be performed in any manner. For example, if the peak trigger voltage VB is within a specific value range above and below the reference voltage value, it can be determined that the two are equal or close. The reference voltage value, and the reference voltage value obtained during the previous measurement period is 1000 units of voltage. In this case, if the peak trigger voltage VB is in the range of 950-1050 unit voltage, 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 metal foreign object 3 does not exist. In another embodiment, the range of values within a specific ratio above and below the reference voltage value can be set to be equal to or close to, for example, the range of five percents of the reference voltage value up and down can be set as close to The reference voltage value, and the reference voltage value obtained during the previous measurement period is 500 units of voltage. In this case, if the peak trigger voltage VB is in the range of 475-525 unit voltage, 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 metal foreign object 3 does not exist.

In addition, if the peak trigger voltage VB is determined to be not equal to or close to the reference voltage value during the current measurement period, it means that there may be metal foreign objects 3 or the output power and/or load of the system have changed. 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 a damping parameter according to the peak trigger voltages measured in two adjacent oscillation periods, and compares the damping parameter with the corresponding threshold value to determine the metallic foreign object 3 . In other words, in the metal foreign object detection process 80, if a first peak trigger voltage (eg VB) is determined not to be equal to or close to the reference voltage value, it is necessary to continue to measure the next oscillation period to obtain a second peak trigger voltage ( VC) in FIG. 4 , to further discriminate the metallic foreign body 3 , the above-mentioned discrimination can be realized by the aforementioned metal foreign body detection method 20 shown in FIG. 2 .

It is worth noting that, under certain circumstances, it may happen that the peak trigger voltage VB is still equal to or close to the reference voltage value due to the movement of the coil or the change of the load while the metal foreign object 3 is approaching. In order to avoid the inability to effectively discriminate the metal foreign object 3 in the above situation, the processor 111 can set the peak trigger voltage VB to be judged to be equal to or close to the reference voltage value for a continuous number of times or an upper limit of a continuous time, and perform measurement when the upper limit is reached. In the next oscillation cycle, the steps of obtaining a second peak trigger voltage (VC in FIG. 4 ) and calculating the attenuation parameter, that is, the metal foreign object detection method 20 shown in FIG. 2 is used to determine the metal foreign object 3 . In one embodiment, the processor 111 may include a counter for counting the consecutive times when the peak trigger voltage VB is judged to be equal to or close to the reference voltage value and thus only a peak trigger voltage VB is measured. The metal foreign object detection method 20 shown in FIG. 2 is executed, at this time, the processor 111 resets the counter to re-count the consecutive times. Alternatively, the processor 111 may also include a timer for judging the continuous time during which the peak trigger voltage VB is judged to be equal to or close to the reference voltage value, and when the timer expires, the metal foreign object detection as shown in FIG. 2 is performed instead. Method 20, where the processor 111 resets the timer to recalculate the continuous time. Alternatively, the operation of the timer may not consider the determination result of the peak trigger voltage VB. For example, the timer may operate periodically according to a fixed timing period. Usually, the metal foreign object detection method 80 shown in FIG. 8 may be used. When the timer expires, the metal foreign object detection method 20 as shown in FIG. 2 is enforced.

In summary, the present invention provides a metal foreign object detection method, which can measure the coil signal to obtain one or more peak trigger voltages during the measurement period when the driving signal is interrupted, and can compare the peak trigger voltage with a previously obtained one. Refer to the voltage value to discriminate metal foreign objects, or calculate the attenuation parameter according to the ratio of the average value of the two adjacent peak trigger voltages to the difference, and then compare the attenuation parameter with the corresponding critical value to determine whether to obtain more peaks. The peak trigger voltage is used to perform subsequent judgments to realize the judgment of metal foreign objects. The processor can set the reference voltage to a trigger start potential of a lower level, and control the reference voltage to gradually increase when a trigger occurs, thereby obtaining a peak trigger voltage. Setting the trigger start potential at a lower level increases the chance of a successful trigger and peak trigger voltage. In addition, when the metal foreign body does not exist, the metal foreign body detection method of the present invention only needs to measure one or two coil oscillation cycles and obtain one or two peak trigger voltages to complete the identification of the metal foreign body. Even if the first wave peak that is not measured is added, the measurement period when the driving signal is interrupted only includes at least 2 to 3 coil oscillation cycles, which can greatly reduce the impact of the driving signal interruption on the power output. In addition, the metal foreign object detection method of the present invention can be judged by the attenuation ratio of the coil signal, instead of the past judgment by the attenuation amount or the attenuation slope, and can solve the disadvantage of being easily affected by the coil amplitude and the load according to the attenuation slope.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (18)

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:

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 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:

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.

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:

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, the processor executes 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.

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 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 threshold value, the processor further performs the following steps:

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.

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

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

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;

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.

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