Amplifiers – Modulator-demodulator-type amplifier
Reexamination Certificate
2006-07-18
2006-07-18
Pascal, Robert (Department: 2817)
Amplifiers
Modulator-demodulator-type amplifier
C375S238000, C332S107000, C332S109000
Reexamination Certificate
active
07078964
ABSTRACT:
A class AD audio amplifier system (10) with DC output detection logic (26) is disclosed. The amplifier system (10) includes multiple audio channels (20), each of which includes a pulse-width-modulator (PWM) (24). The DC detection logic (26) includes a sigma-delta modulator (60) and a digital low-pass filter (62) that monitors the PWM output signals from the PWM modulators (24). The sigma-delta modulator (60) operates at a first clock frequency, while the low-pass filter (62) operates at a much lower clock frequency, so that AC audio components, PWM harmonics, and sigma-delta quantization error is suppressed from the DC detection. The modulated filtered signal is compared against a threshold level (THRSH) to determine whether the amplitude of a DC component at the PWM output is sufficiently high to constitute a fault. If so, a fault detection signal (DC_DET) is issued, and the PWM modulators (24) are disabled to prevent unsafe conditions in the system (10).
REFERENCES:
patent: 6567491 (2003-05-01), McCune et al.
patent: 6771121 (2004-08-01), Nilsson et al.
patent: 2003/0223592 (2003-12-01), Deruginsky et al.
Risbo Lars
Teng James
Brady III W. James
Pascal Robert
Stewart Alan K.
Telecky , Jr. Frederick J.
Texas Instruments Incorporated
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