Condenser Microphone Bias Circuit for Variable Phantom Power
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Solution Overview
Problem
Conventional condenser microphones face issues with bulkiness in compact designs due to the need for external bias components, and they struggle to operate effectively across a wide range of phantom power supply voltages, resulting in suboptimal distortion ratios and output levels.
Innovation Solution
A condenser microphone design featuring a transistor in emitter-follower connection immediately after an impedance converter with a constant current diode and voltage-dividing resistors ensures that the bias voltage adjusts automatically with phantom power supply voltage changes, maintaining stable operation across various voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If an FET does not incorporate a bias part, then the microphone unit section remains compact, but external bias components must be attached making the microphone bulky
Solution Approach 1:
The patent merges the FET with integrated bias components (bias diode and resistor) into a single unified structure. This integration eliminates the need for separate external bias components, achieving both compactness and functional completeness in the microphone unit section.
2Device complexity
If the bias circuit constant is set fixedly, then the circuit design is simple, but the distortion ratio deteriorates at high power supply voltages like 48V
Solution Approach 1:
The patent introduces a dynamic bias circuit that automatically adjusts its operation based on the power supply voltage. The bias circuit constants are designed to vary with the power supply voltage, enabling the circuit to maintain optimal distortion ratio across different voltage levels (12V, 24V, 48V) without requiring manual adjustment or complex switching mechanisms.
3Adaptability or versatility
If the FET incorporates a bias resistor and diode, then the microphone can operate at high power supply voltages, but the microphone unit section becomes bulky
Solution Approach 1:
The patent combines the FET and bias components into a single integrated unit, eliminating the need for separate external bias components. This merging approach enables the microphone to operate across high power supply voltages (including 48V) while maintaining a compact microphone unit section design.
4Stability of the object's composition
If the bias voltage is fixed, then the circuit operation is stable at one voltage level, but the microphone cannot operate properly across the entire power supply voltage range
Solution Approach 1:
The patent designs a dynamic bias circuit that automatically adjusts bias voltage according to the power supply voltage level. The bias circuit constants are specifically configured to vary with the power supply voltage, enabling stable operation across the entire range of power supply voltages (12V, 24V, 48V) without requiring manual intervention or complex voltage switching circuits.
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 design allows for normal operation at any phantom power supply voltage, significantly increasing the maximum output level and permissible input sound pressure levels, while maintaining stability even with extended connections.
Implementation Method 1
voltage-dividing resistors ensures that the bias voltage adjusts automatically with phantom power supply voltage changes
Implementation Method 2
constant current diode and voltage-dividing resistors ensures that the bias voltage adjusts automatically
Implementation Method 3
a transistor in emitter-follower connection immediately after an impedance converter
Data Source
AI summary
A condenser microphone is obtained, in which the bias of a current amplifier circuit in emitter-follower connection immediately after an impedance converter automatically changes in accordance with the switching of phantom power supply voltages and the maximum output level and the maximum permissible input sound pressure level are increased at any power supply voltage. The condenser microphone comprising a transistor Q2 in emitter-follower connection immediately after an FET 2 that constitutes an impedance converter Q1 has a constant current diode D2 connected to an output transformer TRS that also serves as a transformer for phantom power source supply and resistors R0 and R1 that divide the voltage on the cathode side of the constant current diode D2 into a bias voltage that causes the transistor Q2 to operate.