Abstract: A method and apparatus of load detection for an audio amplifier system is described. A load detector includes a first load terminal and a second load terminal; a controller coupled to the first and second load terminals and configured to in a first control loop, vary a first current supplied to a first load terminal dependent on the difference between a first reference signal and the detected first load terminal voltage; and in a second control loop, vary a second current supplied to the second load terminal dependent on the difference between a second reference signal and the detected second load terminal voltage; and to determine a current through a load connected between the first load terminal and the second load terminal from the second current value, and a voltage across the load from the detected voltage difference between the first load terminal voltage and the second load terminal voltage.

Abstract: Aspects are directed to an amplifier circuit including a signal processing circuit and a calibration circuit. In certain specific embodiments, the signal processing circuit includes a signal combiner and a closed-loop feedback path, and the signal processing circuit is designed to provide a loop transfer function for a derived signal partly representing contributions from an audio input signal, a control or pilot signal having a target frequency range, and a calibration signal. The signal combiner is designed to combine aspects of the control or pilot signal and aspects of the audio input signal, and the calibration circuit is designed to adjust an effective gain of the derived signal in response to whether a unity-gain frequency of a signal in the closed-loop feedback path, as provided via the loop transfer function, is higher or lower than the target frequency range.

Abstract: A gain calibration controller and gain calibration method is described for calibrating the gain of a class D audio amplifier comprising an adjustable gain stage and a feedback path coupled to an output of a reconstruction filter. The gain calibration controller detects a first output noise level in a first frequency range and a second output noise level in a second higher frequency range, varies the gain of the adjustable gain stage, determines a minimum stable gain value of a stable gain range from a change in at least one of the first and second output noise level in response to varying the gain of the adjustable gain stage, and determines a maximum stable gain value of the stable gain range from a change in at least one of the first and second output noise level in response to varying the gain of the adjustable gain stage.

Abstract: A gain calibration controller and gain calibration method is described for calibrating the gain of a class D audio amplifier comprising an adjustable gain stage and a feedback path coupled to an output of a reconstruction filter. The gain calibration controller detects a first output noise level in a first frequency range and a second output noise level in a second higher frequency range, varies the gain of the adjustable gain stage, determines a minimum stable gain value of a stable gain range from a change in at least one of the first and second output noise level in response to varying the gain of the adjustable gain stage, and determines a maximum stable gain value of the stable gain range from a change in at least one of the first and second output noise level in response to varying the gain of the adjustable gain stage.

Abstract: A method and apparatus of load detection for an audio amplifier system is described. A load detector includes a first load terminal and a second load terminal; a controller coupled to the first and second load terminals and configured to in a first control loop, vary a first current supplied to a first load terminal dependent on the difference between a first reference signal and the detected first load terminal voltage; and in a second control loop, vary a second current supplied to the second load terminal dependent on the difference between a second reference signal and the detected second load terminal voltage; and to determine a current through a load connected between the first load terminal and the second load terminal from the second current value, and a voltage across the load from the detected voltage difference between the first load terminal voltage and the second load terminal voltage.

Abstract: Disclosed is a charge pump protection device including a power supply voltage, a charge pump to produce an output voltage higher than the power supply voltage, the charge pump including, a pumping capacitor to store voltage during a charging state and to discharge the voltage during a pumping state thereof, a plurality of switches to regulate the charging and pumping states, a charge pump capacitor to store the output voltage, and at least one current limiter in series with at least one of the plurality of switches to limit current and prevent an electrical failure of the charge pump.

Abstract: A current limiter for Class-D amplifiers measures and stores a position of an over-current event. By comparing the stored position, output signals can be selectively inverted. As a result, the Class-D amplifier remains in a defined modulation scheme even during period of current limiting.

Abstract: One example discloses a class-D amplifier apparatus, comprising: an amplifier circuit, having a set of input terminals, a set of output terminals, a quiescent circuit configuration, and an active circuit configuration; an amplifier control device, coupled to the amplifier circuit; wherein the amplifier control device is configured to place the amplifier circuit in the quiescent circuit configuration before measuring a voltage between the set of output terminals; wherein the amplifier control device is configured to add the output terminals voltage from the set of input terminals before placing the amplifier circuit in the active circuit configuration.

Abstract: One example discloses a class-D amplifier apparatus, comprising: an amplifier circuit, having a set of input terminals, a set of output terminals, a quiescent circuit configuration, and an active circuit configuration; an amplifier control device, coupled to the amplifier circuit; wherein the amplifier control device is configured to place the amplifier circuit in the quiescent circuit configuration before measuring a voltage between the set of output terminals; wherein the amplifier control device is configured to add the output terminals voltage from the set of input terminals before placing the amplifier circuit in the active circuit configuration.

Abstract: A current limiter for Class-D amplifiers measures and stores a position of an over-current event. By comparing the stored position, output signals can be selectively inverted. As a result, the Class-D amplifier remains in a defined modulation scheme even during period of current limiting.

Abstract: Disclosed is a charge pump protection device including a power supply voltage, a charge pump to produce an output voltage higher than the power supply voltage, the charge pump including, a pumping capacitor to store voltage during a charging state and to discharge the voltage during a pumping state thereof, a plurality of switches to regulate the charging and pumping states, a charge pump capacitor to store the output voltage, and at least one current limiter in series with at least one of the plurality of switches to limit current and prevent an electrical failure of the charge pump.

Abstract: An amplifier has a dual bridge design with two bridge amplifiers. A mode switch enables them to be configured in a series amplification mode. The switching of the mode switch is dynamic and enables re-use of signal current thereby improving overall system efficiency. A delay to the mode switch closure is provided in the event of clipping of one of the amplifier outputs. This prevents large cross currents from flowing.

Abstract: An amplifier has a dual bridge design with two bridge amplifiers. A mode switch enables them to be configured in a series amplification mode. The switching of the mode switch is dynamic and enables re-use of signal current thereby improving overall system efficiency. A delay to the mode switch closure is provided in the event of clipping of one of the amplifier outputs. This prevents large cross currents from flowing.

Abstract: A dual bridge amplifier includes a first bridge amplifier receiving a first input signal and having a pair of drive outputs connecting to a first load, a second bridge amplifier receiving a second input signal and having a pair of drive outputs connecting to a second load, and a mode switch between one of the drive outputs of the first bridge amplifier and one of the drive outputs of the second bridge amplifier. The mode switch closes and switches the dual bridge amplifier to a series amplification mode, based on detecting the magnitudes of the first and second input signals. The series amplification mode shares current between the first load and the second load, reducing amplifier heat generation.

Abstract: A dual bridge amplifier includes a first bridge amplifier receiving a first input signal and having a pair of drive outputs connecting to a first load, a second bridge amplifier receiving a second input signal and having a pair of drive outputs connecting to a second load, and a mode switch between one of the drive outputs of the first bridge amplifier and one of the drive outputs of the second bridge amplifier. The mode switch closes and switches the dual bridge amplifier to a series amplification mode, based on detecting the magnitudes of the first and second input signals. The series amplification mode shares current between the first load and the second load, reducing amplifier heat generation.