Metal detection method for inductive power supply

Abstract

A method for detecting metallic foreign objects includes: during a detection phase, maintaining a drive signal at a specific potential, causing a coil signal obtained from a power supply coil to enter an attenuation state; setting a reference voltage and comparing the coil signal with the reference voltage to generate a digital output signal with a time length; capturing a complex time length of the digital output signal; calculating a complex time difference between adjacent time lengths and continuously accumulating the time differences to obtain a complex difference accumulation value; and determining whether a metallic foreign object exists within the power transmission range of an inductive power supply based on the distribution relationship of the accumulated difference values.

Claims

1. A method for detecting metallic foreign objects, used in a power supply module of an inductive power supply, the power supply module including a bridge driver and a power supply coil, wherein the bridge driver provides a drive signal to drive the power supply coil, the method for detecting metallic foreign objects includes: During a detection phase, the drive signal is maintained at a specific potential, causing a coil signal obtained from the power supply coil to enter an attenuation state; a reference voltage is set, and the coil signal is compared with the reference voltage to generate a digital output signal with a time length; the complex time lengths of the digital output signal are captured; the complex time differences between adjacent time lengths are calculated, and the time differences are continuously accumulated to a complex difference accumulation value; and the distribution relationship of the accumulated difference values ​​is used to determine whether a metallic foreign object exists within a power transmission range of the inductive power supply.

2. The method for detecting metallic foreign objects as described in claim 1, wherein the specific potential is a low potential.

3. The method for detecting metallic foreign objects as described in claim 1, wherein the bridge driver is a half-bridge driver.

4. The method for detecting metallic foreign objects as described in claim 1, wherein "setting a reference voltage and comparing the coil signal with the reference voltage to generate a digital output signal having a time length" includes: A fixed voltage is set for comparison with the coil signal; the moment when the coil signal begins to be greater than the fixed voltage is a rising edge of the digital output signal, and the moment when the coil signal begins to be less than the fixed voltage is a falling edge of the digital output signal, and the duration between each rising edge and each falling edge is the time length.

5. The method for detecting metallic foreign objects as described in claim 1, wherein "the complex time length for capturing the digital output signal" includes: The duration for which at least three consecutive output signals of that number are obtained.

6. The method for detecting metallic foreign objects as described in claim 5, wherein the time length of at least three consecutive digital coil signals is four.

7. The method for detecting metallic foreign objects as described in claim 1, wherein "calculating a complex time difference between two adjacent time lengths and continuously accumulating the time differences to a complex difference accumulation value" includes: Produce (N-1) time gaps over a complex number (N) time lengths, and sum up the (N-1) time gaps accordingly.

8. The method for detecting metallic foreign objects as described in claim 7, wherein the cumulative value of the segments is calculated using a first-in-first-out method, and the cumulative value interpretation can sum up the results of multiple measurements.

9. The method for detecting metallic foreign objects as claimed in claim 1, wherein "determining whether a metallic foreign object exists within a power transmission range of the inductive power supply based on the distribution relationship of the cumulative difference values" includes identifying different combinations of differences based on the difference variation, and determining whether the metallic foreign object exists based on the combination of differences.

10. The method for detecting metallic foreign objects as claimed in claim 1, wherein the time differences are calculated by a microprocessor, the time differences are accumulated to form the accumulated difference value, and the distribution relationship of the accumulated difference value is determined.

11. The method for detecting metallic foreign objects as described in claim 5, wherein if "the duration for which at least three consecutive digital output signals are acquired" fails, the detection phase is forcibly terminated after a waiting period.

12. The method for detecting metallic foreign objects as claimed in claim 11, wherein after the detection phase is completed, the frequency of the coil signal is increased to reconnect the waveform of the coil signal.

13. The method for detecting metallic foreign objects as described in claim 12, wherein when the coil signal is detected to be at its lowest voltage, the waveform of the coil signal is reconnected.

14. The method for detecting metallic foreign objects as described in claim 1, wherein the coil signal is processed by a signal detection module, wherein the signal detection module includes: A voltage divider circuit, including a complex number of voltage divider resistors; A compensation capacitor is coupled to the voltage divider circuit; A diode is coupled to the compensation capacitor and the voltage divider circuit. And a comparator that receives the coil signal and the reference voltage, and compares the coil signal and the reference voltage to generate the digital output signal having a time length.

15. The method for detecting metallic foreign objects as described in claim 1, wherein the coil signal is processed by a signal detection module, wherein the signal detection module includes: A voltage divider circuit, including a complex number of voltage divider resistors; A compensation capacitor is coupled to the voltage divider circuit; A diode coupled to the compensation capacitor and the voltage divider circuit; a first comparator that receives the coil signal and the reference voltage, and compares the coil signal and the reference voltage to generate the digital output signal having a time length; and a second comparator that receives the coil signal and a ground level voltage, and compares the coil signal and the ground level voltage.

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