Class D Amplifier Voltage Multiplication for Hearing Aid Power
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Solution Overview
Problem
Hearing aids typically operate with a supply voltage of 1.5 Volts, which is insufficient for many sensors and actuators, as well as other components like preamplifiers and microphones, limiting their dynamic range and functionality.
Innovation Solution
A method and arrangement where a Class D amplifier output signal drives a voltage multiplier to generate a higher DC output voltage, using rectification and filtering to produce a stable supply voltage exceeding 1.5 Volts, thereby enabling higher voltage levels for devices within the hearing aid without additional circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a higher supply voltage is used to increase dynamic range and enable additional functionalities, then the functionality and dynamic range improve, but the power consumption increases
Solution Approach 1:
The patent employs a voltage multiplier circuit that operates periodically during the off-time of the Class D amplifier to generate higher voltage only when needed, rather than continuously maintaining high voltage. The multiplier charges capacitors during specific time windows when the amplifier is not driving the receiver, thus providing high voltage functionality only during periods when full power is not required, reducing overall power consumption while enabling enhanced functionality.
2Adaptability or versatility
If a separate power line is added to provide higher voltage to the microphone, then the dynamic range improves, but the device complexity increases
Solution Approach 1:
The patent merges the power supply function with the existing Class D amplifier circuit by using the amplifier's output signal to drive a voltage multiplier that generates the higher voltage needed by the microphone. Instead of adding a completely separate power line with its own battery and regulation circuitry, the solution combines the audio signal path with the power generation function, using the same circuit components (capacitors, diodes) to create the elevated voltage from the amplifier's switching output.
Solution Approach 2:
The voltage multiplier circuit is self-powered by drawing energy from the Class D amplifier's output signal itself. The multiplier uses the amplifier's switching voltage to charge its capacitors and generate the higher voltage, without requiring an external power source or additional battery. The circuit serves itself by converting the amplifier's own output into the elevated voltage needed for the microphone, eliminating the need for separate power supply infrastructure.
3Power
If voltage multiplication is implemented to generate higher DC voltage, then the supply voltage level increases, but the circuit complexity increases
Solution Approach 1:
The patent implements voltage multiplication only in the specific local area where higher voltage is needed - specifically for the microphone and associated signal processing circuits. The voltage multiplier is strategically placed and configured to provide elevated voltage locally to these components, while other parts of the hearing aid continue to operate at the standard 1.5V level. This localized approach avoids the complexity of raising the entire system voltage while still achieving the benefits of higher voltage where required.
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 allows for increased dynamic range, improved functionality, and reduced need for extra components by providing a higher supply voltage, up to 10 Volts, for devices like microphones and memory functionalities within hearing aids, enhancing their performance and reliability.
Implementation Method 1
The power supply unit is adapted to generate an appropriate DC output voltage... The power supply unit comprises rectifying means, such as for example a diode or an active rectifier
Implementation Method 2
The rectifier means may be arranged to form a voltage multiplier, such as a voltage doubler... Depending on how the voltage multiplier is implemented, a DC output voltage level of 2-10 Volts may be reached
Implementation Method 3
the power supply unit further comprises filter means adapted to filter or smoothen a rectified voltage. Such filter means may comprise a capacitor for smoothening the rectified voltage
Data Source
AI summary
The present invention relates to a hearing aid comprising a receiver and signal processor circuitry operatively connected hereto. The signal processor circuitry comprises amplifying means (e.g., a Class D amplifier) adapted to generate a switched output voltage for driving the receiver of the hearing aid. Moreover, a power supply unit is included and is adapted to generate a DC output voltage from the switched output voltage. The present invention further relates to an associated method for generating a DC output voltage.