Asymmetric Charge Pump for Audio Amplifier Voltage Generation
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Solution Overview
Problem
Conventional audio amplifiers face challenges in efficiently generating a negative voltage (VSS) that is lower in magnitude than the positive voltage (VDD) without exceeding a certain voltage limit, which restricts the use of higher breakdown voltage processes and increases fabrication costs.
Innovation Solution
An asymmetric charge pump is integrated into the audio amplifier circuit to generate a negative voltage (VSS) from a positive voltage (VDD), using an inverting DC-DC power converter and a charge pump that adjusts VSS within a predefined limit, eliminating the need for an output capacitor and VDD/2 buffer, allowing for a lower breakdown voltage process and smaller geometry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a conventional symmetric charge pump is used to generate VSS, then the voltage swing range is increased, but the breakdown voltage requirement increases and fabrication cost increases
Solution Approach 1:
The patent applies asymmetry by designing a charge pump where the down-conversion stage uses a single capacitor while the up-conversion stage uses two capacitors. This asymmetric configuration allows the circuit to generate a negative voltage (VSS) that is lower in magnitude than the positive supply voltage (VDD), thereby reducing the overall voltage swing range and allowing the use of lower breakdown voltage processes for fabrication.
2Adaptability or versatility
If higher breakdown voltage processes are used to accommodate larger voltage swings, then the voltage range is improved, but fabrication cost increases
Solution Approach 1:
The asymmetric charge pump configuration with one capacitor in the down-conversion stage and two capacitors in the up-conversion stage enables the circuit to operate with a reduced voltage swing range. This allows the use of standard lower breakdown voltage fabrication processes, thereby reducing fabrication costs while still providing adequate voltage range for audio amplifier operation.
Solution Approach 2:
The patent changes the voltage swing parameter by using an asymmetric capacitor configuration that limits the maximum voltage excursion. By carefully selecting capacitor ratios and switching sequences, the circuit generates VSS as a negative voltage lower in magnitude than VDD, thus reducing the peak-to-peak voltage swing and enabling the use of lower breakdown voltage processes.
3Reliability
If an output capacitor and VDD/2 buffer are used in the charge pump, then the voltage regulation is improved, but the device complexity increases
Solution Approach 1:
The patent extracts and eliminates the need for external output capacitors and VDD/2 buffer components by integrating the voltage regulation function directly into the asymmetric charge pump circuit. The switching network and capacitor configuration inherently provide the necessary voltage regulation, simplifying the overall circuit architecture and reducing component count.
Solution Approach 2:
The patent merges the voltage regulation function with the voltage conversion function in a single integrated charge pump circuit. The asymmetric capacitor configuration and switching network simultaneously perform both voltage conversion and regulation, eliminating the need for separate regulation stages and reducing overall device complexity.
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 enables the use of lower breakdown voltage processes, reduces fabrication costs, and improves performance by allowing adjustable VSS within a defined limit, while avoiding the risks associated with higher voltage swings and capacitor requirements.
Implementation Method 1
An asymmetric charge pump is integrated into the audio amplifier circuit to generate a negative voltage (VSS) from a positive voltage (VDD)
Data Source
AI summary
An audio amplifier with an integrated asymmetric charge pump is provided. The audio amplifier receives VDD and VSS as power supply signals. The integrated charge pump is arranged to provide VSS from VDD, such that VSS is a negative voltage that is lower in magnitude than VDD.