Thx Ltd.

Noise Cancellation Technologies, Inc.

Nct Group, Inc.

Other

University of Essex

Owen Jones

Lawrence R Fincham

Michael C Trinder

Andrew John Mason

Carl Steven Gifford

Embodiments provide an audio amplifier circuit with integrated (built-in) filter (e.g., a digital-to-analog converter (DAC) filter). The audio amplifier circuit may have a non-flat (e.g., low-pass) closed loop frequency response. The audio amplifier circuit may include a low pass filter coupled between an input terminal that receives the input analog audio signal and the input of the gain stage of the amplifier. In some embodiments, additional impedance networks may be included to produce a desired low-pass filter response, such as a second order filter, a third order filter, and/or another suitable filter response. Other embodiments may be described and/or claimed.

Audio amplifier with integrated filter

An amplifier circuit that includes a first amplifier that has a first input that receives an input signal, a second input and an output. The amplifier circuit also includes a second amplifier that has a first input that is coupled to the output of said the amplifier and a second input. The circuit further includes a first impedance network Z, a second impedance network Z, a third impedance network Zand a fourth impedance network Z. The first impedance network Zis coupled to a load and the second input of the second amplifier, the second impedance Zis connected the output of the first amplifier and the second input of the first amplifier, the third impedance Zis connected to the output of the first amplifier and the load, the fourth impedance Zis connected the output of the second amplifier and the second input of said first amplifier.

Amplifier circuit with reduced feedforward current

A power supply that includes a first current generator circuit that is coupled to a first transformer and generates a first waveform and a second current generator circuit that is coupled to a second transformer, and generates a second waveform that is out of phase with the first waveform. The first and second waveforms are rectified and combined into a DC output signal. The power supply includes a first coupling circuit that couples the first current generator circuit to the first transformer and a second coupling circuit that couples the second current generator circuit to the second transformer.

Power conversion techniques

A tracking power supply for one or more amplifiers includes one or more cascaded sets of power boost circuits to temporarily boost the positive and/or negative power supply rail, respectively. Each power boost circuit may include a gain element and an energy source such as a capacitor or battery, and the power boost circuits are linked to provide a greater degree of voltage boost when needed. An optional control circuit monitors amplifier output signal levels, or separately amplified input signal levels, and provides power boost control signals to the power boost circuits, which temporarily raise or lower the positive and/or negative supply voltages above or below the nominal voltage rails in tandem with the highest and lowest output signals, respectively, from the amplifier(s).

Tracking power supply with increased boost capability

A power supply includes two or more input waveforms being shaped or selected so that after being separately level-shifted and rectified, their additive combination results in a DC output waveform with substantially no ripple. The power supply may comprise a waveform generator, a level conversion stage for step up or down conversion, a rectification stage, and a combiner. The waveform generator may generate complementary waveforms, preferably identical but phase offset from each other, such that after the complementary waveforms are level-converted, rectified and additively combined their sum will be constant, thus requiring no or minimal smoothing for generation of a DC output waveform. The level conversion may be carried out using transformers or switched capacitor circuits. Feedback from the DC output waveform may be used to adjust the characteristics of the input waveforms.

Power converter with low ripple output

A low dissipation, low distortion amplifier includes a driver amplifier stage and a main output stage, with a plurality of impedance networks providing, among other things, feedback paths from outputs of the driver and main output stages to the input of the driver stage. The impedance networks also provide coupling paths from the outputs of the driver and main output stages to the load. The impedance networks can all be formed of resistors, capacitors, or network combinations thereof. An additional feedback path can be added from the load to the driver stage to flatten out the frequency response at low frequencies. The driver and main output stages may be operated in Class AB and B modes respectively, and/or in Class G or H modes. An intermediate amplifier driver stage may be added between the driver and main output stages.

Low dissipation amplifier

An earphone device comprises an inner casing enclosing one or more miniature drive units, and a movable cap or outer casing that moves relative to the inner casing. The inner casing has an extension member, such as a hollow post, terminating in an acoustic output port. A compressible foam bulb at least partially surrounds the extension member, and is decompressed and compressed by actuation of an adjustable member. The adjustable member may take the form, for example, of a pivoting lever, a helical cam, or a push-rod mechanism, among other things. A flange may be disposed around the periphery of the movable cap, in order to provide a seal surrounding the ear canal region. The compressible material may be gripped by the hollow extension member, and abut the movable cap or flange. Through actuation of the adjustable member, the compressible material may be decompressed and thus elongated for insertion into the wearer's ear, and may be compressed and thus widened or expanded to form an adequate seal with the wearer's ear canal region.

Earphone device

A dynamic power supply for N amplifiers includes first and second power boost circuits which temporarily boost the positive or negative power supply rail, respectively. A control circuit monitors amplifier output signal levels and provides power boost control signals to the power boost circuits, which temporarily raise the positive supply voltage above the nominal voltage level in tandem with the highest output signal from the N amplifiers and lower the negative supply voltage below the nominal voltage level in tandem with the lowest output signal level from the N amplifiers. The power boost circuits each may be coupled to a reservoir capacitor from which current is drawn to provide the power boost. When inactive, the reservoir capacitors charge up from the respective power supply rails. The dynamic power supply is well suited for audio amplification systems.

Efficient power amplifier

An active noise cancellation system includes a series of features for more effective cancellation, greater reliability, and improved stability. A particular feature adapted for headset systems includes locating a residual microphone radially offset from the center of a sound generator to detect a signal more similar to that incident upon the eardrum of the user. In addition, an open back headset design includes perforations on the side of the headset instead of the back, so that the perforations are less susceptible to inadvertent blockage. The system also includes a mechanism for detecting changes in the acoustic characteristics of the environment that may be caused, for example, by pressure exerted upon the earpieces, and that may destabilize the cancellation system. The system automatically responds to such changes, for example, by reducing the gain or the frequency response of the system to preserve stability. The system further includes other methods for detecting imminent instability and compensating, such as detecting the onset of signals within enhancement frequencies characteristic of the onset of instability, and adjusting the gain or frequency response of the system or suppressing the enhanced signals. The system further includes a mechanism for conserving battery life by turning the system off when sound levels are low, or adjusting the power supply to the system to correspond to the current power requirements of the system.

Growing community of inventors

Ipswich, United Kingdom

Owen Jones