Controlled Feedback Charge Pump for MEMS Bias Stability
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Solution Overview
Problem
Charge pumps used in MEMS transducers, such as microphones, face challenges in maintaining sensitivity and stability due to voltage supply variations and large signals, which affect the bias voltage applied, leading to reduced performance and increased power consumption.
Innovation Solution
A controlled feedback charge pump system that includes a feedback circuit coupled to the charge pump, allowing for regulation of the output voltage by comparing it with a reference signal and enabling/disabling the feedback loop to optimize power efficiency, with an offset voltage applied to both the charge pump and the transducer to stabilize the bias voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a charge pump is used to generate bias voltage for MEMS transducers, then the transducer can operate with elevated voltage for improved sensitivity, but the bias voltage becomes unstable due to supply variations and large signals
Solution Approach 1:
The patent implements a feedback circuit that monitors the charge pump output voltage and adjusts the pumping action to maintain a stable bias voltage despite supply variations. The feedback loop compares the actual output with the desired reference voltage and modulates the charge pump switching to eliminate deviations, thereby stabilizing the bias voltage applied to the MEMS transducer.
Solution Approach 2:
The patent dynamically adjusts the charge pump operating parameters (switching frequency, duty cycle) based on feedback signals to maintain constant bias voltage. By changing these parameters in response to detected voltage deviations, the system compensates for supply variations and large signal conditions while preserving transducer sensitivity.
2Stability of the object's composition
If the feedback loop is continuously enabled to maintain bias voltage stability, then the voltage remains stable, but power consumption increases
Solution Approach 1:
The patent employs periodic sampling and burst-mode feedback operation where the feedback loop is activated only when voltage deviations are detected or at predetermined intervals. During steady-state operation with stable bias voltage, the feedback loop enters a low-power sleep mode, reducing overall power consumption while maintaining voltage stability when needed.
Solution Approach 2:
The patent implements dynamic feedback control where the feedback loop bandwidth and activation are adjusted based on operating conditions. The system transitions between active feedback mode (when stability is needed) and power-saving mode (when voltage is stable), optimizing the trade-off between voltage stability and power consumption in real-time.
Data Source
AI summary
According to various embodiments, a circuit includes a charge pump and a feedback circuit. The charge pump includes a first input, a second input configured to receive an offset signal, and an output terminal configured to provide a charge pump signal based on the first and second inputs. The feedback circuit includes a first input coupled to the output of the charge pump, a second input configured to be coupled to a reference signal, an enable input configured to enable and disable the feedback circuit, and a feedback output coupled to the first input of the charge pump.