Microphone Amplifier Voltage Switching for Hearing Instruments
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Solution Overview
Problem
Hearing instruments face challenges in reducing power consumption of the microphone amplification circuit without compromising noise performance and the ability to handle maximum audio signal levels, due to the high noise level at low bias current and the need for a high power supply voltage to accommodate maximum audio signal levels.
Innovation Solution
A switchable power supply system that dynamically adjusts the DC voltage level based on the detected microphone signal level, using a first lower DC voltage for normal levels and a second higher DC voltage for higher levels, allowing the microphone amplification circuit to operate with low power consumption while maintaining noise performance and handling large sound pressure levels without distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high power supply voltage is used to accommodate maximum audio signal levels, then the ability to handle large sound pressure levels without distortion is improved, but the power consumption of the microphone amplification circuit increases
Solution Approach 1:
The power supply voltage to the microphone amplification circuit is made dynamic through a switchable configuration that selects between a first power supply voltage (higher level) and a second power supply voltage (lower level) based on the detected level of the microphone signal. This dynamic adjustment allows the circuit to consume less power during normal operation while maintaining the capability to handle peak signal levels when needed.
Solution Approach 2:
The invention changes the operating parameter (power supply voltage level) of the microphone amplification circuit based on signal conditions. A level detector monitors the microphone signal level and controls a switch to select between two different power supply voltage levels, thereby adapting the power consumption to the actual signal requirements rather than maintaining a constantly high voltage.
2Use of energy by moving object
If a low bias current is used to reduce power consumption, then the power consumption of the input stage is reduced, but the noise level becomes unacceptably high
Solution Approach 1:
The bias current in the input stage is made dynamic by switching between two different power supply voltage levels. During normal operation with lower signal levels, the circuit operates with lower bias current and lower power consumption. When peak signal levels are detected, the power supply voltage is switched to the higher level, which increases the bias current and reduces noise, ensuring clean signal handling during high-demand conditions.
Solution Approach 2:
The invention changes the bias current parameter of the input stage by switching the power supply voltage. This allows the bias current to be adjusted according to signal requirements - lower during normal operation to save power, and higher during peak signals to maintain low noise performance.
3Object-generated harmful factors
If a high bias current is used to reduce noise level, then the noise performance is improved, but the power consumption of the input stage increases significantly
Solution Approach 1:
The invention dynamically adjusts the bias current by switching between two power supply voltage levels based on signal detection. The high bias current (achieved through higher power supply voltage) is only activated when the level detector identifies high-level microphone signals that require it for low-noise operation. During normal operation, the circuit operates with lower bias current and correspondingly lower power consumption, thus avoiding the continuous high power consumption that would result from maintaining high bias current at all times.
Solution Approach 2:
The power supply voltage parameter is changed based on signal level detection, which indirectly changes the bias current parameter. This parameter change strategy allows the system to achieve low noise performance only when necessary (during high signal levels) while maintaining low power consumption during normal operation, resolving the contradiction between continuous high bias current and power savings.
Data Source
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AI summary
The present invention relates to a hearing instrument which comprises a microphone comprising a microphone transducer element mounted in a microphone housing. The microphone transducer element produces a transducer signal in response to receipt of sound and a microphone amplification circuit is configured to generate an amplified microphone signal from the transducer signal. A control and processing circuit of the hearing instrument is coupled to the microphone amplification circuit for receipt and processing of the amplified microphone signal according to a hearing loss of a user. The microphone amplification circuit has a power supply port coupled to a switchable power supply which is selectively connected to a first power supply voltage, having a first DC voltage level, or a second power supply voltage, having a second DC voltage level, to the power supply port of the microphone amplification circuit. The second DC voltage level is higher than the first DC voltage level. A level detector is configured to detect a level of a microphone signal and connect the first or the second power supply voltage to the power supply port based on the detected level of the microphone signal.