Circuit and method for detecting load impedance
First Claim
1. A device for detecting load impedance, comprising:
- an analog circuit portion for detecting the impedance value of a load, and a digital circuit portion, which is suitable to provide load impedance type information.
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Accused Products
Abstract
A device for detecting load impedance having an analog circuit portion for detecting the impedance value of a load, and a digital circuit portion adapted to provide load impedance type information. The analog circuit portion having two power MOS transistors connected in series to each other and between a supply voltage and the ground, and a pair of mirror MOS transistors common-connected with their respective gate terminals to the gate terminals of the power MOS transistors. The digital circuit portion includes a first comparitor to determine whether the output current of an audio amplifier is higher or lower than a threshold value and a second comparitor to determine whether the output voltage of the amplifier is higher than a threshold voltage, a memory to store output signals of the first and second comparitors, and a logic circuit arranged in cascade with the memory to output a load-type indication signal. The device further includes a third comparitor that enables outputting of the load-type indication signal when the output voltage of the audio amplifier crosses a zero threshold to thereby eliminate unwanted noise.
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Citations
20 Claims
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1. A device for detecting load impedance, comprising:
- an analog circuit portion for detecting the impedance value of a load, and a digital circuit portion, which is suitable to provide load impedance type information.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method for detecting the impedance of a load in real time, comprising:
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reading across a sense resistor a voltage that is proportional to the output current of an amplifier, which is delivered on a reactive load;
comparing the output voltage of said amplifier with a threshold voltage;
on the basis of the value of said comparison, generating a logic signal which indicates the low- or high-impedance type of the load; and
storing said logic signal at rising and falling fronts of said output voltage of the amplifier, in order to detect a low-impedance condition with respectively capacitive or inductive reactive loads. - View Dependent Claims (14, 15, 16, 17)
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18. A load impedance detecting device, comprising:
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an analog load impedance detecting circuit having a sense voltage output representing the voltage across a sense resistor and a load voltage output representing a load voltage; and
a digital load impedance determining circuit coupled to the analog load impedance detecting circuit and configured to receive the sense voltage output and the load voltage output and compare the difference between the sense voltage output and the load voltage output to a first reference voltage and to determine whether the impedance is high or low, and to compare the low voltage output to a second reference voltage to determine the reliability of the load voltage output, the digital load impedance determining circuit further configured to output the comparison of the sense voltage output and the load voltage output when the comparison of the load voltage output to a second reference voltage meets a predetermined threshold value. - View Dependent Claims (19, 20)
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Specification