Charge Pump Current Mode Output Power Throttling

Solution Overview

Problem

Charge pumps in personal audio devices face issues with large inrush or sink currents when switching between output voltage modes, which can lead to system damage due to the inability of capacitors to absorb these currents, necessitating methods for current limiting.

Innovation Solution

A system with a charge pump configured to boost input voltage, a current mode control loop, and a controller that controls the power amplifier into a high-impedance mode and attenuates reference signals to maintain input current below a limit, managing state variables of the loop filter during current-limiting modes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the charge pump switches between output voltage modes, then the output voltage can be adjusted to match signal levels, but large inrush or sink currents are generated that can damage the system

Engineering Contradiction:

Improveoutput voltage adjustmentVSAvoidinrush current

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The control circuit detects the current operating mode of the charge pump before switching occurs. Based on this detection, it proactively generates an appropriate reference voltage in advance that accounts for the upcoming mode transition, ensuring the switching current remains controlled rather than allowing large inrush currents to develop

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The control circuit dynamically adjusts the reference voltage parameter based on the detected charge pump mode. By changing the reference voltage to match the operating conditions and anticipated transitions, the system maintains controlled current flow while enabling output voltage adjustment across different modes

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If the charge pump switches between output voltage modes, then the output voltage can be adjusted to match signal levels, but large sink currents are generated that can damage the system

Engineering Contradiction:

Improveoutput voltage adjustmentVSAvoidsink current

Core Design Contradiction:

Adaptability or versatilityVSObject-generated harmful factors

Solution Approach 1:

The control circuit detects the current operating mode of the charge pump before switching occurs. Based on this detection, it proactively generates an appropriate reference voltage in advance that accounts for the upcoming mode transition, ensuring the switching current remains controlled rather than allowing large sink currents to develop

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The control circuit dynamically adjusts the reference voltage parameter based on the detected charge pump mode. By changing the reference voltage to match the operating conditions and anticipated transitions, the system maintains controlled current flow while enabling output voltage adjustment across different modes

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If a linear power amplifier is used, then the circuit is simple to implement, but power is wasted during low signal level outputs

Engineering Contradiction:

Improvecircuit simplicityVSAvoidpower waste

Core Design Contradiction:

Ease of manufactureVSLoss of energy

Solution Approach 1:

The system dynamically adjusts the charge pump output voltage based on the signal level detected at the power amplifier output. During low signal level outputs, the charge pump provides a reduced voltage that matches the actual power requirements, thereby reducing power waste while maintaining the simplicity of the linear power amplifier topology

Inventive Principle:

Principle #15Dynamics

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This solution effectively limits input currents during mode switching, preventing system damage and improving power efficiency by ensuring the charge pump operates within safe current limits, thereby enhancing the reliability and performance of charge pumps in personal audio devices.

Implementation Method 1

a charge pump configured to boost an input voltage of the charge pump to an output voltage greater than the input voltage

Methodology Applied

Scientific EffectCapacitive energy transfer: Capacitance

Data Source

PatentUS11152906B2Charge pump with current mode output power throttling

Publication Date: 2021.10.19 CIRRUS LOGIC INC

AI summary

A system may include a charge pump configured to boost an input voltage of the charge pump to an output voltage greater than the input voltage, a current mode control loop for current mode control of a power amplifier powered by the output voltage of the charge pump, and a controller configured to, in a current-limiting mode of the controller, control an output power of the charge pump to ensure that an input current of the charge pump is maintained below a current limit, control the power amplifier by placing the power amplifier into a high-impedance mode during the current-limiting mode, and control state variables of a loop filter of the current mode control loop during the current-limiting mode.