Signal-Dependent Amplifier Mode Switching for Low Quiescent Current

Solution Overview

Problem

Class-D amplifiers with closed-loop designs suffer from reduced efficiency at low output power due to high quiescent current, which degrades their performance in applications requiring small power output, such as cellphones or headphones.

Innovation Solution

The amplifier dynamically switches between closed-loop and open-loop modes based on input signal strength, using a digital-to-analog converter, analog signal processing circuit, digital signal processing circuit, and signal detector to optimize power efficiency by enabling or disabling components based on power requirements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If closed-loop mode is used, then performance is improved, but quiescent current increases and efficiency degrades at small output power

Engineering Contradiction:

ImproveperformanceVSAvoidefficiency

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The amplifier dynamically switches between closed-loop and open-loop modes based on the power level of the input signal. A signal detector monitors the input signal power and generates a mode selection signal that controls a switching circuit to select the appropriate processing path, enabling the system to adapt its operation mode to current operating conditions

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes its operational parameters by switching between two distinct modes: closed-loop mode for high-power signals and open-loop mode for low-power signals. This parameter change is controlled by comparing the input signal power against a threshold and adjusting the circuit configuration accordingly

Inventive Principle:

Principle #35Parameter changes

2Reliability

If closed-loop mode is used, then performance is improved, but quiescent current increases

Engineering Contradiction:

ImproveperformanceVSAvoidquiescent current

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The amplifier dynamically switches between closed-loop and open-loop modes based on the power level of the input signal. A signal detector monitors the input signal power and generates a mode selection signal that controls a switching circuit to select the appropriate processing path, enabling the system to adapt its operation mode to current operating conditions

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The harmful element (high quiescent current) is extracted or removed by disabling the analog signal processing circuit and feedback path when operating in open-loop mode for low-power signals, keeping only the essential digital signal processing and driving stage active

Inventive Principle:

Principle #2Taking out (Extraction)

3Power

If amplifier components are enabled for high power output, then power output capability is improved, but power consumption increases at low power levels

Engineering Contradiction:

Improvepower output capabilityVSAvoidpower consumption

Core Design Contradiction:

PowerVSUse of energy by stationary object

Solution Approach 1:

The amplifier dynamically switches between closed-loop and open-loop modes based on the power level of the input signal. A signal detector monitors the input signal power and generates a mode selection signal that controls a switching circuit to select the appropriate processing path, enabling the system to adapt its operation mode to current operating conditions

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes its operational parameters by switching between two distinct modes: closed-loop mode for high-power signals and open-loop mode for low-power signals. This parameter change is controlled by comparing the input signal power against a threshold and adjusting the circuit configuration accordingly

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11205999B2Amplifier with signal dependent mode operation

Publication Date: 2021.12.21 MEDIATEK INC

AI summary

The present invention provides an amplifier including a DAC, an analog signal processing circuit, a digital signal processing circuit, a signal detector and a driving stage is disclosed. The DAC is configured to perform a digital-to-analog conversion operation on a digital input signal to generate an analog input signal. The analog signal processing circuit is configured to generate a first processed signal according to the analog input signal and a feedback signal. The digital signal processing circuit is configured to process the digital input signal to generate a second processed signal. The signal detector is configured to detect strength of the digital input signal to generate a mode selection signal. The driving stage is configured to refer to the mode selection signal to receive one of the first processed signal and the second processed signal to generate an output signal, wherein the feedback signal is generated by the output signal.