摘要:
A system is described for generating a discrete noise-shaped variable switching frequency signal that may be used to define a digital pulse width modulation (“PWM”) period. The system may define a switching frequency waveform that may be used to generate a current switching frequency signal as a function of a system clock. The system may quantize the current switching frequency signal to generate a discrete switching frequency signal that is realizable with the system clock. The system may detect quantization noise and input the noise into the current switching frequency signal to eliminate or reduce discrete tones at the switching frequencies of a PWM signal spectrum.
摘要:
A system is described for generating a discrete noise-shaped variable switching frequency signal that may be used to define a digital pulse width modulation (“PWM”) period. The system may define a switching frequency waveform that may be used to generate a current switching frequency signal as a function of a system clock. The system may quantize the current switching frequency signal to generate a discrete switching frequency signal that is realizable with the system clock. The system may detect quantization noise and input the noise into the current switching frequency signal to eliminate or reduce discrete tones at the switching frequencies of a PWM signal spectrum.
摘要:
A system according to one embodiment includes a digital data modulator configured to generate encoded symbols; an envelope detector configured to receive the encoded symbols and to estimate transmission power information associated with the encoded symbols; a peak detector configured to receive the transmission power information, detect a peak transmission power from two or more sequential data points of the received transmission power information, and to generate a power regulation signal representative of the detected peak transmission power; and a digital to analog converter (DAC) configured to receive the power regulation signal and to provide a reference voltage to a power supply associated with an RF amplifier.
摘要:
A switching amplifier includes a power stage, a low pass filter, a combining circuit, and a feedback correction circuit. The power stage has an input terminal and an output terminal. The low pass filter has an input terminal coupled to the output terminal of the power stage, and an output terminal for providing a filtered pulse width modulated signal. The combining circuit has a first input terminal coupled to the output terminal of the power stage, a second input terminal coupled to the output terminal of the low pass filter, and an output terminal. The feedback correction circuit has a first input terminal for receiving a reference pulse width modulated signal, a second input terminal coupled to the output terminal of the combining circuit, and an output terminal coupled to the input terminal of the power stage.
摘要:
A closed loop audio amplifier system and method of powering up/down the system without producing audible artifacts are provided. During power up, a prebias voltage is provided to each output connected to a speaker to increase the voltage to a nominal output level. High impedance switches are then driven at a 50% duty cycle. Feedback from the output is supplied to a servo, which is enabled to fine tune the output voltage. Low impedance switches are then driven at a 50% duty cycle at a quarter cycle timing. The order of the feedback loop depends on which of the high or low impedance switches are driven. The prebias voltage is then removed before audio signals to be amplified are supplied to the system. Timing of driving of the switches is programmable. To power down, essentially the reverse sequence is provided.
摘要:
An audio amplifier includes a digital signal processor (DSP) that contains a noise shaping quantizer having an integrating error amplifier. The integrating error amplifier contains integrators connected in a feedback loop, a summer supplied with an output of each of the integrators, and a saturation function module producing a saturation function. A multiplier is disposed between each pair of adjacent integrators. The multiplier receives a signal from one of the adjacent integrators and the saturation function and supplies a signal to the other of the adjacent integrators. The saturation function decreases the effect of all of the integrators except an integrator to which an input signal to the integrating amplifier is supplied using an input signal to and/or an output signal from the noise shaping quantizer. This permits the duty ratio of the output signal from the noise shaping quantizer to extend from 0% to 100%.
摘要:
A system and method for analog-to-digital conversion using digital pulse width modulation (PWM) is disclosed. The method and system according to the disclosed invention converts an analog input signal to a digital signal in pulse code modulated (PCM) form. The disclosed invention uses a feedback circuit to perform PWM of the analog input signal. The PWM signal is then decimated to obtain the digital signal in PCM form. The system according to the disclosed invention requires lower operating frequency and dissipates lesser power than prior art systems providing the same sampling frequency and resolution. The operation at a lower frequency is achieved by obtaining two samples from every pulse of the PWM signal; the first sample being obtained from the right duty ratio, and the second sample being obtained form the left duty ratio. Further, the disclosed invention has lesser implementation complexity and higher signal-to-noise ratio than prior art.
摘要:
Disclosed is a method and/or apparatus for adjusting the sample time and order associated with a digital correction system for maximizing output power and minimizing power stage delay sensitivity of a switching power stage. In certain embodiments, the sample point of an ADC may be changed as a function of the duty ratio of the PWM signal thus allowing higher performance and use of less expensive power stage components. In addition, adjustment of the order of an integrating error amplifier in the system permits operation of the power stage with an output being permitted to saturate up to the power supply rails, thus increasing a power output of the power stage.
摘要:
A power amplifier circuit for receiving a variable envelope input signal and for producing an amplified output signal is provided. The power amplifier circuit includes an envelope approximation circuit, an envelope amplifier circuit, a phasor approximation circuit, a quadrature modulation circuit, and a power amplifier. The envelope approximation circuit receives the variable envelope input signal and produces a bandlimited estimated envelope signal, corresponding to the amplitude of the variable envelope input signal. The bandlimited estimated envelope signal is then amplified by an envelope amplifier circuit. The amplified envelope signal is then coupled to the supply input of the power amplifier. The phasor approximation circuit receives the variable envelope input signal and produces a bandlimited estimated phasor signal. The quadrature modulation circuit receives the estimated phase signal and produces a modulated phase signal. The modulated phase signal is then coupled to the signal input of the power amplifier. The power amplifier then produces an amplified output signal.
摘要:
A device for implementing a method for receiving a complex baseband signal in analog form or in digital form, and providing a pulse modulated signal as a linear modulation of the complex baseband signal is disclosed. First, a complex modulated signal as a function of the complex baseband signal is generated. Second, a bandlimited exponential signal as a function of the complex modulated signal as computed with a truncated Taylor series for an exponential is generated, or a coefficient vector as a function of the complex modulated signal is generated. Finally, a pulse modulated signal as either a function of the bandlimited exponential signal or the coefficient vector is generated.