Circuit and method for detecting load impedance
US6812715B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Oct 10, 2002 |
| Grant date | Nov 2, 2004 |
| Priority date | — |
| Expiry date | Oct 10, 2022 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01R27/26
- WIPO fieldMeasurement
- WIPO sectorInstruments
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 comparator 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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.