1332results about "Audio amplifier" patented technology

An energy-efficient consumer device audio power output stage provides improved battery life and reduced power dissipation. A power supply having a selectable operating mode supplies the power supply rails to the power amplified output stage. The operating mode is controlled in conformity with the audio signal level, which may be determined from a volume control setting of the device and / or from a signal level detector that determines the amplitude of the signal being amplified. The power supply may be a charge pump in which the operating mode uses a capacitive divider to provide for selection of a power supply output voltage that is a rational fraction of the power supply output voltage in a full-voltage operating mode.

According to an embodiment, a method includes amplifying a signal provided by a capacitive signal source to form an amplified signal, detecting a peak voltage of the amplified signal, and adjusting a controllable impedance coupled to an output of the capacitive signal source in response to detecting the peak voltage. The controllable impedance is adjusted to a value inversely proportional to the detected peak voltage.

An audio switching power amplifier having an output pulse voltage selected in conformity with an indication of the output signal amplitude provides lower electromagnetic interference (EMI) in class-D amplifier implementations, in particular, in inductor-less designs. The output pulse voltage may be selected by providing multiple switching circuits, such as half or fully bridge switches, with each switching circuit connected to a different power supply. One of the switching circuits is activated by the switching controller, while the others are disabled, providing selection of the output pulse voltage. Selection of a lower pulse voltage, when the maximum voltage is not required, reduces the generated EMI. The switching frequency of the class-D amplifier may also be controlled in conformity with the output signal amplitude, so that at higher output levels a lower switching rate is selected, reducing the generated EMI.

A stereo class-D audio system includes a first die including four monolithically integrated NMOS high-side devices and a second a second die including four monolithically integrated PMOS low-side devices. The audio system also includes a set of electrical contacts for connecting the high and low-side devices to components within the a stereo class-D audio system, the set of electrical contacts including at least one supply contact for connecting the drains of the high-side devices to a supply voltage (Vcc) and at least one ground contact for connecting the drains of the low-side devices to ground, the electrical contacts also including respective contacts for each source of the high and low-side devices allowing the source of each high-side device to be connected to the source of a respective low-side device to form two H-bridge circuits.

A method and apparatus to control output power of a digital amplifier capable of automatically determining an impedance of an earphone or headphone connected to a portable audio device and outputting a power that is optimized according to the impedance. The apparatus is usable with a digital amplification device and includes a signal processing unit to convert a pulse signal into a direct current (DC) voltage by power-amplifying the pulse signal, an impedance measuring unit to connect a resistance device between the signal processing unit and a speaker unit and to detect a voltage value applied to the resistance device and the speaker unit, and a micom unit to generate a pulse signal having a predetermined duty cycle in the signal processing unit if the speaker unit is connected to the device, to determine an impedance of the speaker unit based on the voltage value detected by the impedance measuring unit, to control a power amplification by providing a voltage level control signal to the signal processing unit according to the determined impedance, and to control an audio level in an audio reproduction mode accordingly.

Digital amplifying circuitry delays a digital data signal (INR) to produce an output signal (VoutR). The delayed digital data signal is converted to an analog signal (VinR) for amplifying by an amplifier (10R). Signal amplitude information (S_R[n]) contained in the incoming digital data signal is detected during the delaying. The signal amplitude information is converted to a first control signal (S_Io_NEG[n]) in response to which an adjustable maximum available supply current of the amplifier is produced of least sufficient magnitude to avoid distortion during the amplifying to produce the output signal. The signal amplitude information also is converted to a second control signal (S_AMPLITUDE[n]) in response to which a supply voltage (VNEG) of the amplifier is controlled.

The present invention relates to an audio signal controller adapted to receiving first and second digital audio signals and estimating a signal feature of the first or second digital audio signal. The estimated signal feature is compared with a predetermined feature criterion and the audio signal controller switches from conveying the first digital audio signal to conveying the second digital audio signal to a controller output, or vice versa, at a zero-crossing of the first digital audio signal or the second digital audio signal based on the comparison between the estimated signal feature and the predetermined feature criterion.

A pulse-width modulation (PWM) amplifier is adapted to a class-D amplifier in which an analog input signal is subjected to integration, pulse-width modulation, and switched amplification, wherein a glitch elimination circuit eliminates noise from a pulse-width modulated signal, from which a high pulse signal and a low pulse signal are isolated such that each pulse is delayed by a dead time at the leading-edge timing thereof. When both of them are simultaneously set to a high level, one of them is reduced in level. In response to the occurrence of clipping, an integration constant applied to an operational amplifier is automatically changed from a primary integration constant to a secondary integration constant. When the clipped state is sustained for a prescribed time, an inversion pulse is compulsorily introduced into the pulse-width modulated signal.

Systems and methods in which an ultrasonic signal is introduced into an audio signal before the audio signal is amplified by a switching amplifier. The added ultrasonic signal (e.g., a tone at half the amplifier's switching frequency) shifts the signals input to a set of power switches so that they do not switch nearly simultaneously. The ultrasonic signal causes the output current to be well defined to eliminate dead time distortion at low signal levels. Adding the tone ultrasonic signal causes the distortion to shift to an amplitude greater than zero. Signals that exceed this amplitude will experience the distortion, but the distortion will be less noticeable than in lower-amplitude signals. Signals that do not exceed this amplitude will not experience the distortion at all. Adding an ultrasonic signal may also draw energy away from the switch frequency and its harmonics to interference with AM radio reception.

A self-oscillating switching amplifier having an error amplifier output combined with the output of an output signal differentiator according predetermined weighing factors to force a small oscillation around the averaged output signal at a high frequency. The feedback voltage is sensed at the output of the switching amplifier. Additional feedback can be derived from a switching node of the power switch. The switching of the power switch can be dynamically changed from binary switching when the amplitude of the audio signal is low, to ternary switching when the amplitude of the input signal is high to minimize distortion of the output signal. The amplifier can be supplied with a pulsing voltage. In certain embodiments the output signal differentiator is simply a capacitor or a LC resonance circuit coupled directly to an appropriate speaker terminal for the highest possible self-oscillating frequency of the switching amplifier.

The present invention relates in one aspect to a class D audio amplifier with improved output driver topology supporting multi-level output signals such as 3-level, 4-level or 5-level pulse width or pulse density modulated output signals for application to a loudspeaker load. The present class D audio amplifiers are particularly well-suited for high-volume consumer audio applications and solutions.

A signal processing system and method utilizes a multi-stage amplifier to amplify an input signal. The multi-stage amplifier uses a mixed set of voltage rails to improve the operating efficiency of at least one of the amplification stages while allowing other amplification stages to operate in a predetermined operating mode. Efficiency of at least one of the stages is improved by supplying at least one variable voltage rail to an amplification stage of the multi-stage amplifier. The variable voltage rail varies in response to changes in an input signal voltage to the amplification stage. Accordingly, at least one amplification stage utilizes a variable voltage rail, and all amplification stages are supplied with a set of voltage rails that provides sufficient input signal headroom, thus, providing amplification stage efficiency and adequate voltage to allow operation of all amplification stages.

The present invention relates to an audio amplification circuit comprising a first preamplifier for receipt of an audio input signal and a second preamplifier comprising a first differential input for receipt of an attenuated audio input signal. The attenuated audio input signal is generated by an attenuator coupled to the audio input signal. A non-linear element is coupled to a first input of the first preamplifier thereby distorting the audio input signal at the first input at large signal levels. A distortion compensation network is adapted to supply a distortion compensation signal from the first input of the first preamplifier to a second differential input of the second preamplifier such that distortion in the output signal of the second preamplifier is cancelled or attenuated. The invention further relates to a corresponding method of compensating an audio amplification circuit for distortion induced by a non-linear element.

Techniques for controlling one or more audio amplifiers in or associated with a device coupled on a local area network are disclosed. The device receives at least one selected source from other devices also coupled on the network According to one aspect of the techniques, an automatic shutdown control module is provided in the device to power down the audio amplifiers when there is no audio data flow coming to the device or power up the audio amplifiers when there is audio data flow coming to the device. In one embodiment, the procedure to power down or power up the amplifiers is in accordance with a hysteresis, wherein the hysteresis, being lagging of an effect behind its cause, protects the amplifiers and makes the powering-down or powering-up procedure unnoticeable to a user.

A transducer amplification circuit may include a preamplifier circuit with a signal input receiving a transducer signal to provide an amplified transducer signal comprising audible frequency components and ultrasonic frequency components. The transducer amplification circuit may include a first sigma-delta modulator configured to sample and quantize the amplified transducer signal to generate a first digital transducer signal comprising a first quantization noise signal. The first sigma-delta modulator may include a first noise transfer function having a high pass response in at least a portion of an audible frequency range to push the quantization noise signal to ultrasonic frequencies. A second sigma-delta modulator is configured to sample and quantize the amplified transducer signal to generate a second digital transducer signal comprising a second quantization noise signal. The second sigma-delta modulator may include a second noise transfer function with a magnitude minimum placed at the ultrasonic frequencies.

Systems and methods for automatically adjusting the alignment of high-side and low-side pulse width modulated signals to improve dead time and shoot-through conditions. In one embodiment, a system includes a digital amplifier controller, an amplifier output stage coupled to the controller and configured to receive audio signals from the controller, and one or more sensors coupled to the output stage. The sensors are configured to detect and / or measure various parameters, such as shoot-through current and distortion, which are associated with the operation of the output stage. The sensors provide feedback to an internal processor or modulator of the controller, which then adjusts the timing of the high-side and low-side signals to improve the operating conditions of the output stage by minimizing shoot-through current and / or distortion.

An energy-efficient consumer device audio power output stage provides improved battery life and reduced power dissipation. A power supply having a selectable operating mode supplies the power supply rails to the power amplified output stage. The operating mode is controlled in conformity with the audio signal level, which may be determined from a volume control setting of the device and / or from a signal level detector that determines the amplitude of the signal being amplified. The power supply may be a charge pump in which the operating mode uses a capacitive divider to provide for selection of a power supply output voltage that is a rational fraction of the power supply output voltage in a full-voltage operating mode.

Techniques for controlling one or more audio amplifiers in or associated with a device coupled on a local area network are disclosed. The device receives at least one selected source from other devices also coupled on the network According to one aspect of the techniques, an automatic shutdown control module is provided in the device to power down the audio amplifiers when there is no audio data flow coming to the device or power up the audio amplifiers when there is audio data flow coming to the device. In one embodiment, the procedure to power down or power up the amplifiers is in accordance with a hysteresis, wherein the hysteresis, being lagging of an effect behind its cause, protects the amplifiers and makes the powering-down or powering-up procedure unnoticeable to a user.

A digital audio processor (20) for a digital audio receiver (21) having an improved automute sequence is disclosed. The digital audio processor (20) includes automute detection circuitry (42) that monitors the amplitude of digital audio signals before and after the application of digital filters by digital audio processing circuitry (20d). The amplitude of the input signals are compared against a first threshold level, while the amplitude of the output signals are compared against a second threshold level. In response to the amplitude of the input signals for all of the audio channels (44) falling below the first threshold for a selected time period, a gain stage (50) in each channel ramps down the volume to a mute level, and pulse-width-modulation circuitry (54) is disabled. If the output signal amplitude falls below a second threshold for a channel, the pulse-width-modulation circuitry (54) for that channel is disabled. Hysteresis for the input signal amplitude is preferably added into the automute exit determination.

A Class D amplifier comprises a ramp generator that generates a first reference signal and a second reference signal. A signal generator generates a first signal as the first reference signal exceeds an input signal to the Class D amplifier and generates the first signal as the second reference signal exceeds the input signal. The signal generator generates a second signal as the first reference signal falls below the input signal and generates the second signal as the second reference signal falls below the input signal.

A charging circuit comprising:a charge-pump circuit configured to generates a boosted voltage obtained by boosting an input voltage at each time interval shorter in accordance with an increase of a frequency of an input clock signal;an integrating circuit configured to integrate the boosted voltage to apply the integrated boosted voltage to a capacitor; anda clock signal output circuit configured to output a second clock signal higher in frequency than a first clock signal to the charge-pump circuit as the clock signal, and thereafter output the first clock signal to the charge-pump circuit as the clock signal, in order that a charge voltage of the capacitor reaches a predetermined voltage level in a time shorter than a time in which the charge voltage of the capacitor reaches the predetermined voltage level when the first clock signal is input to the charge-pump circuit as the clock signal.

A capacitive load driving circuit includes an error amplification circuit that amplifies a difference between an external input signal provided to one input terminal and a negative feedback signal provided from the following negative feed back circuit to the other input terminal; a modulation circuit that pulse-modulates the signal outputted from the error amplification circuit; a power switching circuit that switches between a power supply voltage and a ground potential or between a positive power supply voltage and a negative power supply voltage; a gate driving circuit that generates a gate driving signal for switching-controlling a switching element configuring the power switching circuit, from a modulated signal outputted from the modulation circuit; a low-pass filter that is connected to an output side of the power switching circuit and removes switching carrier components included in an output signal of the power switching circuit; an output transformer that boosts an output signal of the low-pass filter and has a primary winding connected to an output terminal of the low-pass filter; a capacitive load that is connected in parallel with a secondary winding of the output transformer; and a negative feedback circuit that performs a negative feedback from the output terminal of the low-pass filter to an input side of the error amplification circuit.

A method and apparatus to generate a pulse width modulated signal from a sampled digital signal by chaotic modulation. The method includes generating predetermined chaotic intervals having random interval values using a chaotic interval generator, and generating the pulse width modulated signal from a reference signal and the sampled digital signal during each of the chaotic intervals. Thus, electromagnetic interference (EMI) that affects an audio amplifier can be remarkably reduced.

In accordance with an embodiment, a system for amplifying a signal provided by a capacitive signal source includes an impedance converter having an input node configured to be coupled to a first terminal of the capacitive signal source, and an adjustable capacitive network having a first node configured to be coupled to a second terminal of the capacitive signal source and a second node coupled to an output node of the impedance converter.

The present invention relates to a class D audio amplifier comprising a pulse width modulator, an adjustable loop filter and a feedback loop. The pulse width modulator generates a first set of pulse width modulated control signals at an adjustable modulation frequency for respective switch control terminals of a first output driver. A controller of the class D audio amplifier is configured to control frequency response characteristics of the adjustable loop filter based on a frequency setting of the adjustable modulation frequency.

Methods and apparatus are disclosed to reduce the size, weight, and heat loss of power modules mountable in loudspeakers. Disclosed embodiments replace conventional linear technology with high frequency switching technology in both the power supply and amplifier. In these embodiments Class-D switching occurs at a low and fixed frequency, using standard components, with audio performance improvements through adaptation of internal error correction. By permitting 100% modulation, maximum output power is obtained, and a simple clip-detecting scheme is possible. A half-bridge and full-bridge with a single main supply reservoir is disclosed, obtaining useful allocation of output power while enabling the use of a simplified power supply. Power supply improvements include simplification and high efficiency, while meeting the particular system requirements of this scheme. Advantages include: increased acoustic output, reduced distortion, wider frequency range, smaller and lighter speaker housings, and lower cost.

The invention discloses a multi-bit Delta-Sigma modulation-based digital speaker system implementation method and device. The method comprises the following steps: 1) converting digital input formats; 2) performing oversampling interpolation filtering; 3) performing multi-bit Delta-Sigma modulation; 4) encoding a thermometer; 5) performing multi-channel mismatch-shaping; 6) converting encoding formats; 7) performing multi-channel digital power amplification; 8) driving a speaker array or a multi-voice coil speaker unit to phonate. The device comprises a digital input interface, an oversampling interpolation filter, a multi-bit Delta-Sigma modulator, a thermometer encoder, a multi-channel mismatch-shaper, an encoding format converter, a multi-channel digital amplifier, and a speaker array or multi-voice coil speaker unit which are sequentially connected. By adopting the method and the device, the high-power output under low-voltage power supply can be realized; the power consumption is reduced; the single chip integration of a multi-channel playback system is realized; the volume weight and the implementation cost of the system are reduced; the quality of playback voice is improved.

A pre-charge apparatus and method for controlling startup transients in a capacitively-coupled switching power stage provide lower cost and improved startup transient performance in Class D amplifiers, as well as in other AC power converter applications. A charging source is activated at startup to control the charging of an external capacitor from a single power supply rail to an operating point voltage equal to the average DC output of the switching circuit, while a control circuit disables the output power stage of the switching converter. The current source may be a constant-current source and / or may be controlled via feedback from the voltage or current at the output terminal of the converter to taper the current level to more accurately control the charging. A discharge circuit can also be provided to discharge the output terminal to an opposite power supply rail before commencing the controlled charging.

An amplifier includes a first comparator, a second comparator, and an output switch. The first and second comparators respectively compare a pair of differential signals with a half-swing modulation signal to generate first and second pulse-width-modulation (PWM) control signals, wherein a voltage swing of the half-swing modulation signal is smaller than voltage swing of the differential signals. The output switch includes a pair of inputs coupled to receive the PWM control signals to provide a ternary encoded output signal in response to the PWM control signals.

An audio amplification circuit may include an input terminal for receipt of an input signal from a transducer. A signal processor may be coupled to the input terminal for receipt and processing of the input signal to generate a processed digital audio signal in accordance with a programmable configuration setting of the signal processor. A serial data transmission interface is configured for receipt of the processed digital audio signal and supply of a corresponding digital audio stream at an output terminal of the integrated audio amplification circuit. A serial data receipt interface may be coupled to an externally accessible configuration terminal of the integrated audio amplification circuit and a controller is configured to adjust one of the programmable configuration setting of the signal processor and a format of a digital audio stream in accordance with first configuration data received through the serial data receipt interface.