Switched-Capacitor Amplifier Output Stage Without DC Blocking Capacitors
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Solution Overview
Problem
Amplifiers in portable audio devices face challenges in miniaturization due to the need for large capacitors to remove DC components from the output signal, and existing solutions requiring additional capacitors or dual supply voltages complicate the design and increase costs.
Innovation Solution
A circuit with an analogue-to-digital conversion stage and switched capacitor output stages that produce charge pulses based on digital signal values, eliminating the need for external capacitors and dual supply voltages, allowing for a compact and cost-effective design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a large capacitor is used to remove DC component from the output signal, then the DC component is effectively blocked, but the physical dimensions of the capacitor become large and cannot be integrated onto a microchip
Solution Approach 1:
The patent changes the operating parameters by using a small capacitor (1μF) in combination with a DC voltage-to-voltage converter that dynamically adjusts the negative supply voltage. This allows the same DC blocking function to be achieved with a much smaller capacitor value compared to traditional approaches.
Solution Approach 2:
The patent introduces a DC voltage-to-voltage converter as an intermediary component that generates a negative supply voltage from the positive supply voltage. This intermediary enables the use of a smaller capacitor while maintaining effective DC component removal through dynamic voltage adjustment.
2Object-affected harmful factors
If a DC voltage-to-voltage converter is used to provide negative supply voltage, then no DC component reaches the speaker, but additional capacitors and inductors are required which cannot be integrated onto a microchip
Solution Approach 1:
The patent merges the DC voltage-to-voltage converter functionality with the existing amplifier circuitry on the microchip. The converter uses the positive supply voltage pin and ground pin already present on the microchip, eliminating the need for separate external components for negative voltage generation.
Solution Approach 2:
The patent makes the existing microchip pins multi-functional. The positive supply voltage pin and ground pin serve dual purposes: providing power to the amplifier and enabling the DC voltage-to-voltage converter operation, thereby eliminating the need for additional dedicated pins.
3Reliability
If regulation of the DC voltage-to-voltage converter is implemented, then the correct output voltage is provided, but cost implications arise and potential instability occurs if regulation is unsuccessful
Solution Approach 1:
The patent implements a self-regulating voltage-to-voltage converter that automatically adjusts the negative supply voltage based on the operating conditions. The converter uses feedback from the amplifier circuitry to maintain proper voltage levels without requiring external regulation components, thereby reducing cost while maintaining reliability.
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 provides an output signal with no DC component, enabling miniaturization of the amplifier and reducing complexity and cost, while maintaining high symbol rates to avoid interference with audio frequencies.
Implementation Method 1
an output stage coupled to receive the digital signal from the analogue-to-digital conversion stage, the output stage comprising an energy storage element and being operable to discharge the energy storage element to produce charge pulses in an output signal
Data Source
AI summary
An amplifier (1) includes an analogue-to-digital converter (ADC) (7) and a switched capacitor output stage (8). The ADC (7) converts an analogue signal into a digital signal containing a sequence of symbols. The switched capacitor output stage (8) charges and discharges a capacitor to produce charge pulses at an output (3). During discharge, switches selectively couple the capacitor to the output (3) in opposite directions to produce charge pulses of opposing polarity. The values of the symbols in the digital signal are used to decide the polarity of charge pulses. In this manner, amplification can be achieved without introducing a direct current (DC) component to the signal at the output (3).