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US 7,750,731 B2Granted
PWM loop filter with minimum aliasing error
AssigneeTexas Instruments Incorporated
InventorsSoeren Poulsen, Lars Risbo
Life of this patent
Estimating the term…
Abstract
One embodiment of an apparatus for filtering an electrical signal includes a loop filter with an input and an output that applies a transfer function to a signal at the input. The transfer function has substantially no real part. The loop filter has a dominant pole placed substantially at or above an upper frequency in the frequency range of interest for the loop filter.
Claims11
An audio amplifier comprising:
- a loop filter having a transfer function with a real part being minimized at and above a switching frequency of the audio amplifier, wherein the loop filter has a dominant pole placed substantially at or above an upper frequency in a range of input frequencies processed by the audio amplifier;
- an adder having:
- a first resistor that receives a clock signal and that is coupled to the loop filter;
- a second resistor that receives the input signal and that is coupled to the loop filter;
- and
- a third resistor that is receives the feedback signal and that is coupled to the loop filter;
- and
- an output stage that is coupled to the adder.
5 more elements
An audio amplifier comprising:
- a loop filter having a transfer function with a real part being minimized at and above a switching frequency of the audio amplifier, wherein the loop filter has a dominant pole placed substantially at or above an upper frequency in a range of input frequencies processed by the audio amplifier;
- an adder that receives a feedback signal and that is coupled to the loop filter, wherein at least one of the loop filter and the adder receives an input signal;
- and
- an output stage having:
- a comparator that is coupled to at least one of the loop filter and the adder;
- and
- a switching power stage that is coupled to the comparator.
4 more elements
An audio amplifier comprising:
- a loop filter having a transfer function with a real part being minimized at and above a switching frequency of the audio amplifier, wherein the loop filter has a dominant pole placed substantially at or above an upper frequency in a range of input frequencies processed by the audio amplifier, and wherein the loop filter includes:
- a first resistor;
- a first leg having a second resistor and a first capacitor coupled in series with one another;
- a third resistor;
- and
- a second leg having a second capacitor, wherein the first resistor, the first leg, the third resistor, and the second leg are coupled in series with one another;
- an adder that receives a feedback signal and that is coupled to the loop filter, wherein at least one of the loop filter and the adder receives an input signal;
- and
- an output stage that is coupled to the adder.
6 more elements
Dependencies are inferred from the claim text.