摘要:
A system and method for reducing audible turn-on and turn-off transients in switching amplifiers employs a frequency shaped start sequence in front of a modulated zero-signal or a frequency shaped stop sequence following a modulated zero-signal.
摘要:
A digital amplifier includes a noise shaper and a dither generator arranged to introduce noise to the shaper. The generator uses a seed value derived from a state variable of the shaper.
摘要:
An error model can be utilized to mitigate errors associated with a conversion system, such as an analog-to-digital or digital-to analog converter. The error model is adaptively calibrated to approximate error characteristics associated with at least a portion of the conversion system, such as a digital-to analog converter. The error model can be generated on-line during system operation or off-line to improve performance of various types of signal converters and systems using such signal converters.
摘要:
A system and method are provided for stopping a quantized signal from a noise-shaper with a significantly reduced inband transient, compared to a traditional random stop of a noise-shaped signal. The noise-shaped signal is stopped at a favorable time controlled by a detector that monitors the noise-shaped signal. The detector indicates the occurrence of a good time to stop the noise-shaper such that the transient due to the stop is minimized in a fashion that substantially reduces the inband disturbance.
摘要:
A multiple-channel audio processor (10) and an associated plurality of power stages (22) in an audio system are disclosed. The audio processor (10) includes a plurality of audio amplifier channels (22), each of which includes a pulse-code-modulation (PCM) to pulse-width-modulation (PWM) conversion function (25), which generates PWM signals for application to the plurality of power stages (22). The audio amplifier channels (20) each also include an interchannel delay function (28) for delaying the PWM edges relative to other channels (20), for reducing noise. The audio amplifier channels (20) each also include delay adjust circuitry (32) for gradually increasing and decreasing the interchannel delay of the channel (20) on startup and shutdown. This permits a single control terminal (VALID) at the processor to globally enable and disable all of the power stages (22).
摘要:
In an embodiment of the invention, the voice coil of an electro dynamic transducer is protected against thermal overload by estimating the temperature of a magnet in the electro dynamic transducer. When a power limit based on the temperature of the magnet and on a predetermined voice coil temperature limit is reached by an audio signal, the power applied to the voice coil is reduced.
摘要:
The present invention achieves technical advantages as a high performance analog charge pumped phase locked loop (PLL)(10) with process and temperature compensation in closed loop bandwidth. The PLL reduces the variation in bandwidth and stability by making the product KVCO*ICP independent of process and temperature variation. The PLL achieves a higher performance than existing PLL architectures, achieving a high dynamic range up to at least 110 dB, such that a PWM class-D amplifier is realizable with this PLL. The PLL has a constant bandwidth and damping factor while using an analog charge pump (16).
摘要:
A digital audio processor (20) is disclosed, in which digital filter coefficients associated with a plurality of sampling frequencies are stored in a plurality of coefficient memory banks (55). A controller in the digital audio processor (20) selects one of the coefficient memory banks (55) for use in the digital signal processing channels (44). In a manual mode, this selection is in response to a manual selection entry in a bank control register (41). In an automatic mode, indicated by a specific entry in the bank control register (41), sample rate detector circuitry (54) detects the sampling frequency relative to an external reference, such as a crystal (XTL); the appropriate one of the coefficient memory banks (55) is then selected based on sampling frequency associations stored in rate select register (43) in the controller (40).
摘要:
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).
摘要:
A technique to implement removal of dead time control circuitry from the back-end of a digital switching amplifier system 100 and add dead time control circuitry on the front-end digital modulator chip. The front-end dead time control circuitry adaptively adjusts timing of the output PWM control signals 124 to optimize performance and power consumption, i.e. operate with minimum dead time for all transitions. The front-end dead time control circuitry controls all propagation delays associated with the digital switching amplifier system 100.