Texas Instruments Incorporated
DEVICES AND METHODS TO CONTROL DYNAMIC AUDIO RANGE IN BOOSTED AUDIO SYSTEMS

Abstract:

A controller regulates the voltage delivered to the load and current drawn from the battery in an audio system depending on ripple in the battery voltage which is input to the controller to allocate power for audio playback. Regulation maximizes available headroom while avoiding audio clipping. The effect of internal battery and external parasitic resistance (ESR) on ripple is compensated by an iterative process. ESR is rapidly increased whenever the minimum of the battery voltage input to the controller falls below a clipping threshold and slowly decreased whenever such voltage exceeds such threshold and the audio is under compression. A limiter allocates power to utilize more of the available audio headroom. A de-emphasis filter in each audio signal path compensates for capacitive ripple in the battery voltage input to the controller. As the frequency of the audio input changes, the filter(s) allow frequency-dependent power/current regulation to fill the full audio range without distortion.