# US 11,906,993 B2 · Nonlinear feedforward correction in a multilevel output system

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- Number: US 11,906,993 B2
- Document ID: US11906993B2
- Status: Granted
- Kind: B2
- Application number: 17/960,335
- Filed: 2022-10-05
- Published: 2023-05-04
- Granted: 2024-02-20
- Earliest claimed: 2021-11-03
- Assignees: Cirrus Logic, Inc.
- Applicants: Cirrus Logic International Semiconductor Ltd.
- Inventors: John L. Melanson; Thomas H. Hoff
- Web page: https://patentgrep.com/patent/US11906993B2

## CPC

- G05F 1/46: wherein the variable actually regulated by the final control device is DC (G05F1/625 takes precedence)
- G05F: SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES

## Abstract

A feedforward correction block for use in a multi-level output system may include circuitry configured to determine an occurrence of a mode transition between operating modes of the multi-level output system, capture a loop filter output of a signal path of the multi-level output system occurring before and after the occurrence of the mode transition, and based on the transition and a change in the loop filter output responsive to the transition, determine a transition-specific compensation function to apply to a feedforward input signal of the signal path that is combined with the loop filter output.

## Claims

### Claim 1

A feedforward correction block for use in a multi-level output system having an output driver subsystem for outputting an output driving signal response to an input signal, comprising:
circuitry configured to:
determine an occurrence of a mode transition between operating modes of the multi-level output system;
capture a loop filter output of a signal path of the multi-level output system occurring before and after the occurrence of the mode transition; and
based on the transition and a change in the loop filter output responsive to the transition, determine a transition-specific compensation function to apply to a feedforward input signal of the signal path that is combined with the loop filter output;
wherein:
the multi-level output system is configured to operate in a selected operating mode selected from a plurality of operating modes based on the input signal; and
a supply voltage for the output driver subsystem is selected based on the selected operating mode.

### Claim 2 (depends on 1)

The feedforward correction block of claim 1, wherein the transition-specific compensation function defines a gain value as a function of the feedforward input signal.

### Claim 3 (depends on 2)

The feedforward correction block of claim 2, wherein the transition-specific compensation function defines a gain value as a piecewise linear function of the feedforward input signal.

### Claim 4

A method for feedforward correction in a multi-level output system having an output driver subsystem for outputting an output driving signal response to an input signal, comprising:
determining an occurrence of a mode transition between operating modes of the multi-level output system;
capturing a loop filter output of a signal path of the multi-level output system occurring before and after the occurrence of the mode transition; and
based on the transition and a change in the loop filter output responsive to the transition, determining a transition-specific compensation function to apply to a feedforward input signal of the signal path that is combined with the loop filter output;
wherein:
the multi-level output system is configured to operate in a selected operating mode selected from a plurality of operating modes based on the input signal; and
a supply voltage for the output driver subsystem is selected based on the selected operating mode.

### Claim 5 (depends on 4)

The method of claim 4, wherein the transition-specific compensation function defines a gain value as a function of the feedforward input signal.

### Claim 6 (depends on 5)

The method of claim 5, wherein the transition-specific compensation function defines a gain value as a piecewise linear function of the feedforward input signal.

### Claim 7

A multi-level output system, comprising:
an output driver subsystem for outputting an output driving signal response to an input signal, wherein:
the multi-level output system is configured to operate in a selected operating mode selected from a plurality of operating modes based on the input signal; and
a supply voltage for the output driver subsystem is selected based on the selected operating mode; and
a feedforward correction block comprising circuitry configured to:
determine an occurrence of a mode transition between operating modes of the multi-level output system;
capture a loop filter output of a signal path of the multi-level output system occurring before and after the occurrence of the mode transition; and
based on the transition and a change in the loop filter output responsive to the transition, determine a transition-specific compensation function to apply to a feedforward input signal of the signal path that is combined with the loop filter output.

### Claim 8 (depends on 7)

The multi-level output system of claim 7, wherein the transition-specific compensation function defines a gain value as a function of the feedforward input signal.

### Claim 9 (depends on 8)

The multi-level output system of claim 8, wherein the transition-specific compensation function defines a gain value as a piecewise linear function of the feedforward input signal.