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Switching amplifierSwitching amplifier description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20090251212, Switching amplifier. Brief Patent Description - Full Patent Description - Patent Application Claims
This application claims the priority benefit of European patent application number 08300125.5, filed on Feb. 29, 2008, entitled “SWITCHING AMPLIFIER,” which is hereby incorporated by reference to the maximum extent allowable by law. 1. Field of the Invention The present invention relates to an amplifier and in particular to an amplifier comprising one or more switches controlled by a hysteresis block. 2. Discussion of the Related Art Switching amplifiers, such as class D audio amplifiers, are amplifiers that generate an output voltage by switching an output node between a supply voltage and a ground voltage. The duration of the pulses during which the output node is coupled to the supply voltage determines the output voltage level. This is controlled by a feedback loop that drives the switches. It has been proposed to provide a hysteresis stage in the feedback loop for controlling the switches. It is often an aim when designing such amplifiers to minimize noise and distortion at the output node. However, known designs that use hysteresis stages tend to have poor power supply rejection ratio (PSRR) meaning the effect of ripples in the power supply is relatively high on the output voltage. There is thus a need for a switching amplifier with a good PSRR. It is one aim of embodiments of the present invention to at least partially address one or more needs in the prior art. According to one aspect of the present invention, there is provided an amplifier comprising at least one switch controlled by an output voltage of a hysteresis block, wherein the hysteresis block is adapted to receive a low threshold voltage, a high threshold voltage and an input voltage signal based on an integration of an error signal, the hysteresis block being arranged to change the output voltage from a first value to a second value when the input voltage signal is higher than the high threshold voltage and to change the output voltage from the second value to the first value when the input voltage signal is lower than the low threshold voltage, and wherein the low threshold voltage is equal to a reference voltage level minus a supply voltage level, and the high threshold voltage is equal to the reference voltage level plus the supply voltage level. According to an embodiment of the present invention, the low threshold voltage is equal to Vref−αVDD and the high threshold voltage is equal to Vref+αVDD, where Vref is the reference voltage level, α is a non-zero constant, and VDD is a power supply voltage. According to another embodiment of the present invention, the amplifier further comprises an integrator coupled to the hysteresis block to provide the input voltage signal; a power stage comprising the switches and coupled to receive the output voltage; and adder circuitry arranged to receive an input signal of the amplifier and an output voltage of the power stage, and to provide the error signal to an input of the integrator, the error signal based on the input signal and the output voltage. According to another embodiment of the present invention, the hysteresis block comprises a first comparator for comparing said input voltage signal to the high threshold voltage and a second comparator for comparing the input voltage signal to the low threshold voltage. According to another embodiment of the present invention, the hysteresis block further comprises an SR flip-flop adapted to be set by the output of one of the first and second comparators and reset by the output of the other of the first and second comparators. According to another embodiment of the present invention, the amplifier further comprises a class D amplifier coupled to receive the output voltage of the hysteresis block, the class D amplifier comprising the switches. According to another embodiment of the present invention, the amplifier further comprises circuitry adapted to generate the high and low threshold voltages, the circuitry comprising at least one variable resistance for allowing the supply voltage level to be adjusted. According to a further aspect of the present invention, there is provided an electronic device, or a mobile communications device comprising the above amplifier. According to yet a further aspect of the present invention, there is provided a method of controlling a power stage of an amplifier comprising: performing integration on an error signal to generate an integrated signal, the error signal being based on an input signal to be amplified and the output voltage of the power stage; comparing by a hysteresis block the integrated signal with a high threshold voltage and a low threshold voltage, and generating an output signal that changes from a first value to a second value if the integrated signal is higher than the high threshold voltage and changes from the second value to the first value if the integrated signal is lower than the low threshold voltage, wherein said low threshold voltage is equal to Vref−αVDD and said high threshold voltage is equal to Vref+αVDD, where Vref is a common mode voltage level, α is a constant, and VDD is a power supply voltage. Continue reading about Switching amplifier... Full patent description for Switching amplifier Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Switching amplifier patent application. Patent Applications in related categories: 20090289710 - Amplifier providing power recovery from a narrow-band antenna - A method, amplifier and system are provided for enabling power recovery from a narrow-band antenna when a signal having bandwidth exceeding that of the antenna is utilized. The amplifier provides amplification of a source signal to the antenna and recovery of power stored in the antenna during periods when the ... 20090289709 - Closed loop timing feedback for pwm switching amplifiers using predictive feedback compensation - Methods and systems are disclosed for closed loop feedback for pulse width modulated (PWM) switching amplifiers using predictive feedback compensation (PFC) for suppressing distortions caused by supply voltage variations and output amplitude switching non-idealities in pulse width modulated (PWM) switching amplifiers by pre-compensating the PWM input based upon the supply ... ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Switching amplifier or other areas of interest. ### Previous Patent Application: Feedforward linearization of rf power amplifiers Next Patent Application: Method for adjusting threshold voltage and circuit therefor Industry Class: Amplifiers ### FreshPatents.com Support Thank you for viewing the Switching amplifier patent info. IP-related news and info Results in 2.41132 seconds Other interesting Feshpatents.com categories: Canon USA , Celera Genomics , Cephalon, Inc. , Cingular Wireless , Clorox , Colgate-Palmolive , Corning , Cymer , paws |
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