588 results about "Class-D amplifier" patented technology

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.

Introduce a pulse length control mechanism to generate virtual multi-level output pulses for a Class-D Amplifier, which has only 2 physical output levels. Typically a Sigma-Delta-Modulator converts the input signal into high frequency low bit rate. The disclosed invention adds functions to transform the SDM signal into pulses with equivalent multi-level time-voltage areas and adds a pulse-length-control mechanism to produce various output pulse patterns, where the summations of the positive and negative pulses, within one sampling period, result in time-voltage area values, corresponding to 3 or more digital levels. Thus the invention produces higher signal quality at lower sampling rates.

A wireless power transmission system transmits power wirelessly from a power transmitter to a power receiver. The power transmitter includes a class E amplifier, a transmitting-end resonant circuit, a detector that detects a voltage or current waveform at a predetermined position in the class E amplifier in accordance with the impedance of the transmitting-end resonant circuit as viewed from the class E amplifier, and a signal extractor that extracts a signal according to the waveform. The power receiver includes a receiving-end resonant circuit, a rectifier circuit, a power reproducing section, and an impedance changer connected between the rectifier circuit and the power reproducing section to change its impedance. When the impedance is changed, the detector detects the waveform variation and the signal extractor extracts and outputs a signal corresponding to the waveform detected by the detector.

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.

A class AD audio amplifier system (10) with improved recovery from clipping events is disclosed. The amplifier system (10) includes multiple audio channels (20), each of which can be constructed to include a pulse-width-modulator (PWM) (24). The PWM modulator (24) includes a pair of comparators (39A, 39B; 52+, 52−) that generate complementary PWM output signals based upon the comparison between a filtered difference signal and a reference waveform. Clip detection logic (26) is provided to detect clipping at the output of the channel (20), preferably by detecting successive edges of the reference waveform without an intervening edge of a PWM output signal. In response to detecting clipping, a first integrator (30; 45) is reset to remove residuals and to eliminate the first integrator (30; 45) from the loop filter of the modulator (24). A saturation level circuit (35) applies a clamping voltage, preferably in both clipping and non-clipping situations, to a second integrator (36; 47). As a result, the loop filter is prevented from entering extreme conditions during clipping, which greatly reduces the clipping recovery time.

Digital transmitters having improved characteristics are described. In one design of a digital transmitter, a first circuit block receives inphase and quadrature signals, performs conversion from Cartesian to polar coordinates, and generates magnitude and phase signals. A second circuit block (which may include a delta-sigma modulator or a digital filter) generates an envelope signal based on the magnitude signal. A third circuit block generates a phase modulated signal based on the phase signal. The third circuit block may include a phase modulating phase locked loop (PLL), a voltage controlled oscillator (VCO), a saturating buffer, and so on. A fourth circuit block (which may include one or more exclusive-OR gates or an amplifier with multiple gain states) generates a digitally modulated signal based on the envelope signal and the phase modulated signal. A fifth circuit block (which may include a class D amplifier and/or a power amplifier) amplifies the digitally modulated signal and generates an RF output signal.

A class AD audio amplifier system (10) with DC output detection logic (26) is disclosed. The amplifier system (10) includes multiple audio channels (20), each of which includes a pulse-width-modulator (PWM) (24). The DC detection logic (26) includes a sigma-delta modulator (60) and a digital low-pass filter (62) that monitors the PWM output signals from the PWM modulators (24). The sigma-delta modulator (60) operates at a first clock frequency, while the low-pass filter (62) operates at a much lower clock frequency, so that AC audio components, PWM harmonics, and sigma-delta quantization error is suppressed from the DC detection. The modulated filtered signal is compared against a threshold level (THRSH) to determine whether the amplitude of a DC component at the PWM output is sufficiently high to constitute a fault. If so, a fault detection signal (DC_DET) is issued, and the PWM modulators (24) are disabled to prevent unsafe conditions in the system (10).

A monolithic 1.75 is mounted in a speaker cabinet 1.71 to drive the voice coil 1.74 of the speaker 1.70. The monolithic integrated circuit may be a class D amplifier 1.10, and is at least a half-bridge or full bridge power MOSFET device. Structures and process for forming the mos switching devices 2.20 of the bridge driver circuits are disclosed. Also disclosed is the N+ buried layer 4.14 of the QVDMOS transistors 4.43 of the bridge circuits.

An amplifier having an active and passive gain stage connect to a load for driving a load according to a system analog input. A first embodiment of the amplifier in accordance with the present invention includes a logic network connected between a comparator network and a switching system, wherein the comparator network connects to the passive gain stage. Specifically, the active gain stage may include an active filter connected to receive an analog or digital input and provide a difference between the analog or digital input and the feedback signal relative to the gain factor of a gain unit connected to the active filter. The passive gain stage includes a passive filter. The logic network generates at least one switching signal which controls the switching system that includes at least one switching device to selectively provide power to the load. An output signal from the switching system provides output for the amplifier and is fed back to the active gain stage. In another embodiment, the output is a two-level signal and the passive and active filters are second order low pass filters, where the gain factor is about 25 or more. In yet another embodiment, the gain factor is approximately 250. Moreover, the amplifier may include a digital delta-sigma modulator connected to supply a two level input.

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 class-D amplifier for pulse-width-modulating an analog input signal to output a pulse-width-modulated signal, includes: a differentiating circuit for differentiating the pulse-width-modulated signal of the class-D amplifier; and a negative feedback circuit for feeding back the differentiated signal of the differentiating circuit to an input side of the class-D amplifier in a negative feedback manner.

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 is directed to an amplifier circuit based on the principle of a class D amplifier. To avoid unwanted convolution effects and to improve the power supply rejection ratio, provision is made for the amplitude of the ramp signal used for pulse width modulation to track proportionally the supply voltage for the amplifier circuit. For this purpose, the ramp signal generator has an amplitude control input suitably connected to supply and reference potentials. This ensures a constant duty ratio which is independent of the supply voltage. The present circuit may be used, for example, as a DC/DC converter or as an audio amplifier.

The invention discloses an active noise reduction method applied to a range hood. A noise reduction system using the active noise reduction method comprises a power supply system, input equipment, output equipment and a data processing module; the input equipment is connected with the data processing module; the data processing module is connected with the output equipment; the input equipment particularly comprises noise information input equipment, namely, a noise acquisition microphone array, a pre-amplification module and an ADC module; the data processing module comprises a filter, a controller W1 and a controller W2; and the output equipment comprises a loudspeaker array specially used for emitting noise reduction sound waves, a DAC module and a D type amplifier. The noise reductionsystem can be matched with system equipment according to different models of range hoods, the reusability is high and the noise reduction effect is remarkable; to solve the problem that inner equipment of the range hood is stained with oil, oil-tight films or half-funneled oil isolation and sound transmission structures are additionally arranged at the peripheries of the inner equipment, the situation that effect of the range hood becomes poor due to the pollution of oil smoke is avoided, and the situation that the response of an equipment drive is changed due to the fact that the equipment drive is affected by the oil pollution is avoided.

A fiber optic link is provided that is receptive of an AM RF input signal, includes an analog comparator for comparing the input signal with a triangle waveform to convert the input signal to a PWM signal. The PWM signal is converted into an optical signal, and transmitted over a fiber optic cable to an optical receiver. The optical receiver converts the optical signal back into a PWM signal, which is amplified via a Class D amplifier. The amplified PWM signal is passed through a low pass filter for converting it into an AM RF output signal having a predetermined power level, the output signal corresponding to the AM RF input signal.