H-Bridge Hearing Aid Output Stage With Time-Averaged Three-State Drive
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Solution Overview
Problem
Existing hearing aid output stages consume high power due to frequent switching of transistors for low-amplitude signals, reducing battery life, and complex designs with three-state signals are not suitable for hearing aids.
Innovation Solution
A time-averaging output stage for hearing aids using a single-bit Sigma-Delta modulator with an H-bridge driver, where one branch is controlled by a binary signal and the second branch by a time-delayed version, transforming the two-state bitstream into a three-state drive condition to reduce transistor switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a push-pull driver with high-bit-rate Sigma-Delta modulator is used, then the output signal can be driven effectively, but power consumption increases due to frequent transistor switching for low-amplitude signals
Solution Approach 1:
The patent applies periodic action by using a time-averaging output stage that converts high-speed single-bit signals into time-averaged three-state drive conditions. The H-bridge driver alternates between different states in a periodic manner, where the output transducer experiences averaged drive conditions over time rather than rapid switching. This periodic operation allows low-amplitude signals to be represented by extended periods in the same state rather than frequent transitions, thereby reducing power consumption while maintaining effective signal representation through temporal averaging.
2Duration of action of moving object
If a three-state signal system is implemented to reduce power consumption, then battery life is extended, but device complexity increases making it unsuitable for hearing aids
Solution Approach 1:
The patent applies segmentation by dividing the H-bridge driver into two separate branches, each controlled by its own binary control signal. This segmentation allows each branch to be independently controlled with simple binary signals, avoiding the need for complex three-state signal generation logic. The time-delayed version of the first control signal drives the second branch, creating the three-state effect through the interaction of two simple binary control systems rather than requiring a single complex three-state controller.
Solution Approach 2:
The patent uses a time-delay element as an intermediary between the first binary control signal and the second branch of the H-bridge. This time-delay intermediary transforms the first control signal into a time-delayed version that drives the second branch, enabling the creation of three-state drive conditions through the interaction of two binary signals with a temporal relationship. This intermediary approach simplifies the overall system by using basic time-delay circuitry rather than complex three-state signal generation.
3Device complexity
If high-speed single-bit Sigma-Delta modulator is used, then signal representation is simplified, but transistor switching frequency increases causing high power consumption
Solution Approach 1:
The patent applies continuity of useful action by implementing a time-averaging output stage that maintains continuous drive to the output transducer while reducing the effective switching frequency. The H-bridge driver operates continuously with binary control signals, but the time-averaging effect ensures that the output transducer experiences continuous averaged drive conditions rather than discontinuous high-frequency switching. This continuous operation with temporal averaging maintains signal fidelity while reducing power consumption by eliminating frequent transistor switching events.
Data Source
AI summary
In an output stage for a hearing aid (62), a reduction in the power consumption for low level input signals is obtained through the use of a time-averaging output driver (42), whereby the output transducer is subject to three different conditions of operations, this being obtained through the generation of three-state control signals for control of a H-bridge. The three-state control signals are generated through the use of a time-averaging device whereby the two-level output of a single bit Sigma-Delta modulator (21) is transformed to a set of control signals that, at any given time, can assume one of three states. In a preferred embodiment the time-averaging device is a delay (40).