Abstract: An audio amplifier system is described comprising: a variable gain audio processor for processing digital audio signal, a digital to analog converter coupled to the audio processor, and configured to receive the processed digital audio signal, a variable gain amplifier having an input coupled to the output of the digital to analog converter and operably connected to a power supply, a controller coupled to the variable gain audio processor and the variable gain amplifier and configured to switch the audio amplifier system between a first operating mode having a first power supply voltage value and a second operating mode having a second higher power supply voltage value; wherein the controller is operable in the first operating mode to set the audio amplifier system gain to a desired gain value and in the second operating mode to maintain the desired gain value.

Abstract: A loudspeaker controller (1) for controlling a loudspeaker (2), configured to determine time-varying impedance information of the loudspeaker (2) based on a loudspeaker voltage and a measure of a loudspeaker current and provide for control of the loudspeaker (2) in accordance with said time-varying impedance information.

Abstract: An audio amplifier system is described comprising: a variable gain audio processor for processing digital audio signal, a digital to analog converter coupled to the audio processor, and configured to receive the processed digital audio signal, a variable gain amplifier having an input coupled to the output of the digital to analog converter and operably connected to a power supply, a controller coupled to the variable gain audio processor and the variable gain amplifier and configured to switch the audio amplifier system between a first operating mode having a first power supply voltage value and a second operating mode having a second higher power supply voltage value; wherein the controller is operable in the first operating mode to set the audio amplifier system gain to a desired gain value and in the second operating mode to maintain the desired gain value.

Abstract: A loudspeaker controller (1) for controlling a loudspeaker (2), configured to determine time-varying impedance information of the loudspeaker (2) based on a loudspeaker voltage and a measure of a loudspeaker current and provide for control of the loudspeaker (2) in accordance with said time-varying impedance information.

Abstract: A loudspeaker controller (1) for controlling a loudspeaker (2), configured to determine time-varying impedance information of the loudspeaker (2) based on a loudspeaker voltage and a measure of a loudspeaker current and provide for control of the loudspeaker (2) in accordance with said time-varying impedance information.

Abstract: A loudspeaker controller (1) for controlling a loudspeaker (2), configured to determine time-varying impedance information of the loudspeaker (2) based on a loudspeaker voltage and a measure of a loudspeaker current and provide for control of the loudspeaker (2) in accordance with said time-varying impedance information.

Abstract: Disclosed is a class D amplifier comprising a modulation stage having a first input for receiving an input signal and an output for producing a modulated version of the input signal; a plurality of power stages, each power stage being responsive to said modulation stage and comprising a first switch and a second switch coupled in series between a first voltage source and a second voltage source, each power stage comprising an output node between the first switch and the second switch; and a power stage control circuit for measuring the input signal level and enabling a selected number of the power stages as a function of the measured input signal level. A method for controlling such a class D amplifier is also disclosed.

Abstract: A pulse density modulation, PDM, driver, outputs a PDM stream and can be switched to a control token. The switch takes place when the first integral of the PDM stream has a magnitude less than or equal to a first predetermined value and the second integral of the PDM stream has a magnitude less than or equal to a second predetermined value.

Abstract: A switching amplifier comprising: an output driving circuit (400) including a pair of switching transistors (M1, M2) connected in series between a pair of supply voltage lines (VP, gnd); a switch driver circuit (204a) configured to drive the switching transistors (M1, M2) with first and second respective PWM signals dependent on an input signal (101); an output connection between the pair of transistors (M1, M2) for driving an output load (403); and an output current sensing circuit for measuring a current through the output load, the output current sensing circuit comprising: a current sensing resistor (401a) connected between a first one (M2) of the pair of transistors and an adjacent supply voltage line (gnd); and a voltage sense circuit (404) connected across the current sensing resistor, wherein the voltage sense circuit is configured to sample a voltage across the current sensing resistor (401a) at a midpoint of successive corresponding portions of one of the PWM signals.

Abstract: Disclosed is a class D amplifier comprising a modulation stage having a first input for receiving an input signal and an output for producing a modulated version of the input signal; a plurality of power stages, each power stage being responsive to said modulation stage and comprising a first switch and a second switch coupled in series between a first voltage source and a second voltage source, each power stage comprising an output node between the first switch and the second switch; and a power stage control circuit for measuring the input signal level and enabling a selected number of the power stages as a function of the measured input signal level. A method for controlling such a class D amplifier is also disclosed.

Abstract: A pulse density modulation, PDM, driver, outputs a PDM stream and can be switched to a control token. The switch takes place when the first integral of the PDM stream has a magnitude less than or equal to a first predetermined value and the second integral of the PDM stream has a magnitude less than or equal to a second predetermined value.

Abstract: A switching amplifier comprising: an output driving circuit (400) including a pair of switching transistors (M1, M2) connected in series between a pair of supply voltage lines (VP, gnd); a switch driver circuit (204a) configured to drive the switching transistors (M1, M2) with first and second respective PWM signals dependent on an input signal (101); an output connection between the pair of transistors (M1, M2) for driving an output load (403); and an output current sensing circuit for measuring a current through the output load, the output current sensing circuit comprising: a current sensing resistor (401a) connected between a first one (M2) of the pair of transistors and an adjacent supply voltage line (gnd); and a voltage sense circuit (404) connected across the current sensing resistor, wherein the voltage sense circuit is configured to sample a voltage across the current sensing resistor (401a) at a midpoint of successive corresponding portions of one of the PWM signals.

Abstract: A class D amplifier (1) comprises an input unit (11) for receiving a digital input signal (Vin), a pulse shaping unit (12) for producing pulse shaped signals in dependence of the input signal (Vin), a comparator unit (13) for comparing the pulse shaped signals and producing a comparator signal, a driver unit (14) for producing driver signals in dependence of the comparator signal, a switching output unit (15) for producing a pulse width modulated output signal (Vout) in dependence of the driver signals, and a feedback unit (16) for feeding the output signal (Vout) back to the pulse shaping unit (12). The input unit (11) comprises a clipping control unit (10) for controlling the duty cycle of the pulse width modulated output signal (Vout).