Hearing Aid IC AC Filter for DC Blocking Without Signal Loss
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In hearing assistive devices, DC from microphones can overload or limit the dynamic range of A/D converters, and traditional methods using external capacitors are undesirable due to cost and manufacturing considerations.
Innovation Solution
An integrated circuit component with an AC filter, comprising a coupling capacitor and a pair of parallel diodes, is used to prevent DC from entering the delta sigma converter, allowing AC-coupling directly into the chip and integrating all components within the circuit to avoid audible signal losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a capacitor is provided between the microphone and the A/D converter to prevent DC from entering the converter, then DC blocking is achieved, but discrete external components increase cost and manufacturing complexity
Solution Approach 1:
The patent combines the capacitor and resistive element into a single integrated AC filter circuit within the integrated circuit component. This merging eliminates the need for discrete external components while maintaining the DC blocking function, thereby reducing device complexity and manufacturing cost.
Solution Approach 2:
The integrated circuit component performs multiple functions: it acts as both the A/D converter and incorporates the AC filter circuit with the capacitor and resistive element. This multi-functionality eliminates the need for separate external components, resolving the contradiction between DC blocking capability and device complexity.
2Object-affected harmful factors
If discrete external components are used for DC blocking, then DC prevention is achieved, but cost and manufacturing complexity increase
Solution Approach 1:
The capacitor and resistive element are merged into a single integrated circuit component, eliminating the need for separate discrete components. This integration reduces manufacturing cost and simplifies the manufacturing process while maintaining effective DC prevention.
Solution Approach 2:
The integrated circuit component provides its own DC blocking capability through the integrated AC filter circuit, eliminating the need for external components. This self-service approach reduces both cost and manufacturing complexity.
3Ease of manufacture
If all filter components are integrated in the integrated circuit component, then manufacturing cost is reduced, but the AC filter must effectively block DC while maintaining dynamic range
Solution Approach 1:
The patent uses a pair of parallel and opposite diodes as the resistive element, which exhibits very high resistance on a small silicon area. This parameter change (using diodes instead of traditional resistors) enables effective DC blocking while maintaining a compact integrated structure, thereby ensuring reliability without compromising integration.
Solution Approach 2:
The capacitor is connected between the feedback node and a virtual ground node, with the diodes providing a high-resistance path. This intermediary arrangement effectively blocks DC from the feedback node while maintaining the integrity of the integrated circuit, ensuring reliable DC blocking.
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 blocks DC while maintaining the dynamic range and preventing audible signal losses, enabling efficient AC-coupling within the integrated circuit component of hearing assistive devices.
Implementation Method 1
The AC filter includes a coupling capacitor and a resistive element. The capacitor of the AC filter is connected between the feedback node of the at least one delta sigma converter and a virtual ground node, whereby the capacitor effectively blocks DC from the feedback node.
Implementation Method 2
The resistive element is preferably provided by a pair of parallel and opposite diodes, as diodes exhibit very high resistance on a small silicon area and consequently these are attractive to use when high resistance is required. The diodes are connected between the output of a first amplifier in the at least one delta sigma converter and the virtual ground node, whereby the first amplifier receives DC feedback via the diodes.
Data Source
AI summary
A hearing assistive device having an input transducer (18) for picking up sound from the environment, a digital signal processor (27) for alleviating a hearing loss of a specific user by compensating an audio signal according to the users hearing deficit, and an output transducer (29) for reproducing the compensated audio signal. The hearing assistive device further includes an integrated circuit component (40) having at least one analog-to-digital converter adapted for receiving an audio input signal from a microphone and providing a data output for signal processing. The at least one analog-to-digital converter includes an AC filter (50) preventing audible signal losses towards the microphone, and the AC filter (50) is provided with all components integrated in the integrated circuit component (40).