Temperature Compensated Voltage Pump for Condenser Microphones
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Solution Overview
Problem
Integrated circuit voltage pumps used in condenser microphones experience significant temperature-induced changes in DC output voltage due to diode voltage drops, leading to inaccuracies across the operational temperature range, which is undesirable for applications requiring precise DC bias voltage.
Innovation Solution
Incorporating a compensation circuit that generates non-overlapping voltage pulses to adjust for temperature-induced changes in diode voltage drops, using a temperature-sensitive DC voltage source and a temperature-independent DC voltage source to track and compensate for diode voltage variations, thereby maintaining accurate DC output voltage across the temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a voltage pump uses semiconductor diodes in cascaded pump stages, then voltage multiplication is achieved, but temperature-induced changes in diode voltage drops cause significant variations in DC output voltage
Solution Approach 1:
The patent implements a feedback mechanism where the DC output voltage is continuously monitored and compared against a reference value. Based on this comparison, the control circuit adjusts the drive signals to the pump capacitors to compensate for temperature-induced diode voltage drop changes, thereby maintaining accurate DC output voltage across the operational temperature range.
Solution Approach 2:
The patent changes operational parameters by dynamically adjusting the voltage pulses applied to pump capacitors based on detected output voltage levels. This parameter adjustment compensates for temperature effects on diode characteristics, allowing the system to maintain reliable DC output voltage accuracy while achieving voltage multiplication.
2Power
If the number of pump stages is increased to achieve higher DC output voltage, then voltage multiplication is improved, but the cumulative effect of diode voltage drop variations is amplified
Solution Approach 1:
The feedback mechanism monitors the final DC output voltage after all pump stages and provides corrective control signals that account for the cumulative temperature effects across all diodes in the cascade, thereby maintaining precision even with multiple pump stages.
Solution Approach 2:
The control circuit acts as an intermediary that processes temperature and output voltage information, then generates compensating control signals for each pump stage. This intermediary function coordinates the operation of multiple stages to maintain overall output accuracy despite individual diode variations.
3Device complexity
If standard diodes are used in the voltage pump, then device complexity is minimized, but temperature compensation requires additional circuitry
Solution Approach 1:
The feedback-based temperature compensation circuitry monitors output voltage and automatically adjusts operating parameters to compensate for temperature effects, providing reliable temperature stability without requiring replacement of standard diodes with specialized temperature-compensated components.
Solution Approach 2:
The voltage pump system performs self-compensation by using its own output voltage as feedback to automatically adjust its operation. This self-service mechanism provides temperature stability without requiring external compensation circuits or specialized components beyond the standard diodes.
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
The solution effectively reduces temperature-induced variations in DC output voltage, ensuring high accuracy and stability of the voltage pump's output over the operational temperature range, which is crucial for maintaining the electroacoustical sensitivity of condenser microphones.
Implementation Method 1
A diode voltage drop across a diode such as a diode-connected PMOS transistor has a temperature coefficient of about 2 mV per degree C.
Data Source
AI summary
The present invention relates to an integrated circuit voltage pump with temperature compensation circuitry providing improved DC output voltage accuracy over an operational temperature range. The compensation circuitry is operative to eliminate or reduce temperature induced changes of voltage drops across semiconductor diodes of the integrated circuit voltage pump.