Cirrus Logic Inc.

Thomas H Hoff

Eric Jerome King

John L Melanson

Axel Thomsen

Anthony Stephen Doy

Lingli Zhang

Ross Crawford Morgan

Tejasvi Das

Siddharth Maru

Xiaofan Fei

Johann Guy Gaboriau

Xin Zhao

Lei Zhu

Zhaohui He

Graeme G Mackay

Willem Zwart

Roberto Napoli

Bhoodev Kumar

Yongjie Cheng

Malcolm Blyth

Vivek Oppula

Angus Black

Muraleedharan Ramakrishnan

Kemal S Demirci

This application relates to methods and apparatus for clipping prevention. A driver apparatus for driving a transducer has a switching driver configured to switch at least one output node between different switching voltages with a controlled duty-cycle to drive an output signal across the transducer. A clipping prevention controller is configured to control a gain applied to the input signal so as to provide limiting of the input signal to avoid clipping of the output signal. The clipping prevention controller is configured to dynamically control at least one limiting threshold used to determine when to apply limiting of the input signal based on an indication of load resistance of the transducer and the input voltage to the switching driver.

Clipping prevention in switched mode drivers

This application relates to methods and apparatus for driving a transducer. A transducer driver has a switch network that is operable to selectively connect a driver output to any of a first set of at least three different switching voltages which are, in use, maintained throughout a switching cycle of the driver apparatus. The switch network is also operable to selectively connect the driver output to flying capacitor driver. A controller is configured to control the switch network and flying capacitor driver to generate a drive signal at the driver output based on an input signal, wherein in one mode of operation the driver output is switched between two of the first set of switching voltages with a controlled duty cycle and in another mode of operation the driver output is connected to the flying capacitor driver which is switched between first and second states with a controlled duty cycle.

Driver circuitry and operation

This application relates to methods and apparatus for driving a transducer with switching drivers. A driver circuit has first and second switching drivers for driving the transducer in a bridge-tied-load configuration, each of the switching drivers having a respective output stage for controllably switching the respective driver output node between high and low switching voltages with a controlled duty cycle. Each of switching drivers is operable in a plurality of different driver modes, wherein the switching voltages are different in said different driver modes. A controller controls the driver mode of operation and the duty cycle of the switching drivers based on the input signal. The controller is configured to control the duty cycles of the first and second switching drivers within defined minimum and maximum limits of duty cycles; and to transition between driver modes of operation when the duty cycle of one of the switching drivers reaches a duty cycle limit.

Pulse width modulation (PWM) driver circuitry comprising: a loop filter configured to receive an analog input signal and to output a digital loop filter output signal based on the analog input signal and an analog feedback signal; and a PWM modulator configured to receive a digital signal based on the digital loop filter output signal and to output a PWM signal, wherein the PWM driver circuitry further comprises a feedback path coupled to an output of the PWM driver circuitry for the analog feedback signal.

Circuitry comprising a loop filter

This application relates to methods and apparatus for driving a transducer with switching drivers. A switching driver has first and second supply node for receiving supply voltages and includes an output bridge stage, a capacitor and a network of switches. The network of switches is operable in different switch states to provide different switching voltages to the output bridge stage. A controller is configured to control the switch state of the network of switches and a duty cycle of output switches of the output bridge stage based on an input signal to generate an output signal for driving the transducer.

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.

Nonlinear feedforward correction in a multilevel output system

This application relates to methods and apparatus for driving a transducer with switching drivers where the switching driver has an output bridge stage for switching an output node between switching voltages and a modulator for controlling the duty cycle of the output bridge stage based on an input signal. The switching driver also includes a voltage controller for providing the switching voltages which is operable to provide different switching voltages in different driver modes. A controller is provided to control the driver mode of operation and the duty cycle of the switching driver based on the input signal, and the controller is configured to transition from a present driver mode to a new driver mode by controlling the voltage controller to provide the switching voltages for the new mode and controlling the modulator to vary the duty cycle of the output bridge stage. The change in duty cycle is controlled such that there is no substantial discontinuity in switching ripple due to the mode transition.

Driver circuitry for driving a load based on an input signal, comprising: at least one variable boost stage comprising: first and second input nodes configured to receive a first voltage and a second voltage respectively; first and second flying capacitor nodes for connection to a flying capacitor therebetween; a network of switching paths for selectively connecting the first and second input nodes with the first and second flying capacitor nodes; an output stage for selectively connecting a driver output node to each of the first and second flying capacitor nodes; and a controller operable in a first boost mode to: control the output stage to selectively connect the driver output node to the first flying capacitor node; control the network of switching paths to switch connection of the second flying capacitor node between the first and second input nodes at a controlled duty cycle; and in a first charge top-up cycle, control the network of switching paths to connect the first input node to the first flying capacitor node during a phase of the controlled duty cycle in which the first input node is connected to the second flying capacitor node; wherein the frequency of the controlled duty cycle is greater than the frequency of the charge top-up cycle.

Driver circuitry

Driver circuitry for driving a load based on an input signal, comprising: at least one variable boost stage comprising: first and second input nodes configured to receive a first voltage and a second voltage respectively; first and second flying capacitor nodes for connection to a flying capacitor therebetween; a network of switching paths for selectively connecting the first and second input nodes with the first and second flying capacitor nodes; an output stage for selectively connecting a driver output node to each of the first and second flying capacitor nodes; and a controller operable in a first boost mode to: control the output stage to selectively connect the driver output node to the first flying capacitor node; control the network of switching paths to switch connection of the second flying capacitor node between the first and second input nodes at a controlled duty cycle; and in a first charge top-up cycle, control the network of switching paths to connect the first input node to the first flying capacitor node during a phase of the controlled duty cycle in which the first input node is connected to the second flying capacitor node; wherein the frequency of the controlled duty cycle is a greater than the frequency of the charge top-up cycle.

A power output circuit supplies an audio power output signal that is adjusted to prevent clipping when needed based on an estimate of available energy from the power supply supplying the power output circuit. The power output circuit may be an audio power output circuit that generates an audio power output signal from samples of an audio program that are stored in a buffer. A processing block determines an energy requirement for producing the audio power output signal from the audio program and adjusts an amplitude of the audio power output signal in conformity with the determined energy requirement and an available energy determined for the power supply so that the audio power output signal is reproduced without clipping of the audio power output signal.

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Austin, TX, United States of America

Thomas H Hoff