Systems and methods for over-current protection

A digital amplifier comprising:

• an over-current hard clipping unit configured to receive a digital audio signal and clip the digital audio signal according to a clip level;
• a modulator configured to receive the digital audio signal from the over-current hard clipping unit and to modulate the digital audio signal to produce a modulated audio signal;
• an output stage configured to receive the modulated audio signal and to generate an output current to drive a load;
• and
• an over-current sensing unit configured to compare the output current to a threshold value and to generate an over-current signal which indicates whether an over-current condition exists;
• wherein the over-current hard clipping unit is configured to receive the over-current signal and to ramp down the clip level while the over-current condition exists;
• wherein in order to ramp down the clip level while the over-current condition exists, the over-current hard clipping unit is configured to
• set the clip level to a value of the audio signal in the immediately preceding time period minus a decrement value, if the audio signal was not clipped in the immediately preceding time period;
• and
• decrease the clip level by the decrement value, if the audio signal was clipped in the immediately preceding time period.

A method implemented in a digital amplifier that includes an output stage that is driven in dependence on an audio signal, the method comprising:

• detecting an over-current condition in the output stage that is driven in dependence on the audio signal;
• while the over-current condition exists in the output stage that is driven in dependence on the audio signal, ramping down a clipping level at which the audio signal is clipped;
• clipping the audio signal according to the clipping level;
• wherein ramping down the clipping level comprises
• if the audio signal was not clipped in the immediately preceding time period, then setting the clipping level to a value of the audio signal in the immediately preceding time period minus a decrement value;
• and
• if the audio signal was clipped in the immediately preceding time period, then decreasing the clipping level by the decrement value.

A digital amplifier comprising:

• an over-current hard clipping unit configured to receive a digital audio signal and clip the digital audio signal according to a clip level;
• a modulator configured to receive the digital audio signal from the over-current hard clipping unit and to modulate the digital audio signal to produce a modulated audio signal;
• an output stage configured to receive the modulated audio signal and to generate an output current to drive a load;
• and
• an over-current sensing unit configured to compare the output current to a threshold value and to generate an over-current signal which indicates whether an over-current condition exists;
• wherein the over-current hard clipping unit is configured to receive the over-current signal and to ramp down the clip level while the over-current condition exists;
• wherein in order to ramp down the clip level while the over-current condition exists, the over-current hard clipping unit is configured to
• determine an audio input signal value upon receiving the over-current signal which indicates that the over-current condition exists;
• set the clipping level to an initial clip value that is less than or equal to the audio input signal value;
• and
• decrease the clip level, for each successive time period in which the over-current condition persists.