Apparatus and method of limiting power applied to a loudspeaker

An apparatus to limit power to a load, comprising:

• a power source to drive the load;
• a monitor coupled to the power source to detect a power level supplied by the power source and to provide a power signal representative of said power level;
• a control circuit to receive said power signal and to provide a value based on said power signal according to one or more control parameters which include a power averaging time and a power threshold;
• and,
• a signal attenuator coupled to the power source and the control circuit, the signal attenuator to limit said power level based on said value, wherein an averaging coefficient (TA) is calculated by the control circuit using the power averaging time according to
• T
• A
• =
• ⅇ
• -
• n
• t
• a
• ⁢
• f
• s
• ,
• where n is a filter order, ta is the power averaging time in seconds, and fS is a sampling frequency.

A method for limiting power to a load comprising;

• driving the load with an input signal;
• providing a voltage signal that is representative of a voltage of the input signal;
• providing a current signal that is representative of a current of the input signal;
• calculating a gain value based on said voltage signal and said current signal according to one or more control parameters which include at least one of a power averaging time, a power threshold, an attack time and a release time;
• limiting the input signal based on the value;
• and
• calculating the gain value using the power threshold according to,
• gain
• =
• P
• T
• ⁢
• A
• I
• ⁢
• A
• V
• L
• ,
• where L is an averaged power level, PT is the power threshold, AI is a corrective factor for the current signal, AV is a corrective factor for the voltage signal.

A method for limiting power to a load comprising:

• driving the load with an input signal from a power source;
• providing a power signal that is representative of a power level of the input signal;
• calculating a value based on said power signal according to one or more control parameters which include at least one of a power averaging time, a power threshold, an attack time and a release time;
• limiting the input signal based on the value;
• and
• calculating the gain value using the power threshold according to,
• gain
• =
• P
• T
• ⁢
• A
• I
• ⁢
• A
• V
• L
• ,
• where L is an averaged power level, PT is the power threshold, AI is a corrective factor for the current signal, AV is a corrective factor for the voltage signal.