Single-Supply Audio Amplifier Biasing With Switched Capacitor Inversion
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Solution Overview
Problem
Conventional Class D audio amplifiers require two ports for biasing the output stage MOSFET with opposite voltage sources, increasing the complexity and number of ports needed for operation.
Innovation Solution
An audio amplifier driven by a single voltage source, where the voltage supply circuit generates a second voltage source with opposite electrical polarity using a series of switches and capacitors, allowing the single voltage source to drive the amplifier with reduced port requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pair of voltage sources (positive and negative) is used to bias the output stage MOSFET of a Class D amplifier, then the amplifier can operate with proper biasing, but the number of ports required increases to two
Solution Approach 1:
The patent combines the functions of two separate voltage sources (positive and negative) into a single voltage source by using a capacitor to generate the negative voltage. The capacitor is charged to the positive voltage level and then used to generate the negative voltage through switching operations, effectively merging two voltage source functions into one physical voltage source connection.
Solution Approach 2:
The patent introduces a capacitor as an intermediary element that mediates between the single voltage source and the need for dual voltage sources. The capacitor stores energy and enables the generation of negative voltage from a single positive voltage source, acting as a mediator that resolves the contradiction between single-source simplicity and dual-source functionality.
2Ease of manufacture
If two ports are added to receive positive and negative voltage sources, then the MOSFET can be properly biased, but the circuit complexity and port requirements increase
Solution Approach 1:
The patent merges the biasing implementation into a single port by using a capacitor to generate both positive and negative voltage levels from one voltage source. This reduces the manufacturing complexity associated with connecting two separate voltage sources while maintaining the ease of operation through a simplified single-port interface.
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
The solution enables the audio amplifier to operate with a pair of voltage sources having the same electrical level but opposite poles, reducing the number of ports needed for biasing the output stage MOSFET from two to one, simplifying the design and operation.
Implementation Method 1
a first capacitor having a first terminal coupled to the second terminal of the first switch, and a second terminal, a third switch having a first terminal coupled to the second terminal of the first capacitor
Data Source
AI summary
After coupling a first voltage source to a voltage supply circuit, a second voltage source having a same electrical level but an opposite electrical pole with said first voltage source is generated. An audio amplifier is then driven by both the first voltage source and the second voltage source, where said audio amplifier requires a pair of voltage sources having the same electrical level but opposite electrical poles to be driven. The voltage supply circuit generates the second voltage source from the first voltage source by simultaneously switching two sets of switches, where said both sets of switches have non-synchronous statuses in switching.