Soft transitions between muted and unmuted states in class D audio amplifiers
US7378904B2 · kind B2 · utility
Assignee
Inventor
Key dates
| Filing date | Oct 12, 2004 |
| Grant date | May 27, 2008 |
| Priority date | — |
| Expiry date | Dec 19, 2025 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03F3/217
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A class AD audio amplifier system (10) with reduced noise capability in muting and unmuting events is disclosed. The amplifier system (10) includes multiple audio channels (20), each of which can be constructed to include a pulse-width-modulator (PWM) (24). The PWM modulator (24) includes a pair of comparators (39A, 39B; 52+, 52−) that generate complementary PWM output signals based upon the comparison between a filtered difference signal and a reference waveform. When the system is muted, a common mode voltage (CM_RAMP) is applied to the inputs of the comparators (39A, 39B; 52+ 52−) to suppress the duty cycle at the amplifier output, preferably to a zero duty cycle. In the transition from a muted state to an unmuted state, the common mode voltage (CM_RAMP) is ramped from the suppressing voltage to zero common mode voltage, permitting the duty cycle of the complementary PWM signals to gradually increase, thus reducing clicks and pops. The converse operation is performed in the transition from unmuted to muted. Pulse-width-modulation control logic (26) is also included to ensure that that the PWM “on” and “off” pulses are of at least a minimum duration, and also to generate compensa…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.