Differential Amplifier Gain Control for Stable Slew Rate Throttling
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Solution Overview
Problem
High voltage amplifiers in haptic drivers using piezoelectric actuators face challenges in maintaining controlled slew rate during battery throttling, leading to system malfunction and reduced battery life due to excessive current demand.
Innovation Solution
A method and circuit that control the gain of a differential amplifier by comparing the DC voltage input against a reference voltage, generating a gain control signal, and adjusting the bias current to maintain a constant rise time during throttling, using a Miller compensation capacitance and multi-bit digital signal control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the gain of the amplifier is reduced automatically to preserve battery life duration during voltage drops, then battery life duration is improved, but the waveform slew rate changes and normal operation becomes difficult to achieve
Solution Approach 1:
The patent dynamically adjusts the bias current of the differential amplifier in response to detected voltage drops, allowing the amplifier to adapt its operating characteristics. This dynamic adjustment maintains controlled slew rate during throttling while preserving battery life, resolving the contradiction between extending battery duration and maintaining normal operational reliability.
Solution Approach 2:
The invention changes the bias current parameter of the amplifier based on the detected voltage conditions. By modifying this key parameter, the amplifier's slew rate is controlled during battery throttling, enabling both battery life extension and maintained operational normality to be achieved simultaneously.
2Use of energy by moving object
If the gain of the amplifier is reduced automatically during battery throttling to decrease current consumption, then current consumption is reduced, but the slew rate control becomes uncontrolled and system malfunction may occur
Solution Approach 1:
The patent employs a feedback mechanism where the amplifier's operation is monitored and the bias current is adjusted in response to voltage drop detection. This feedback loop ensures that slew rate remains controlled even as gain is reduced to decrease current consumption, preventing system malfunction while achieving energy savings.
Solution Approach 2:
The bias current is dynamically adjusted based on real-time voltage monitoring, creating a adaptive system that maintains slew rate control during throttling. This dynamic response allows current consumption to be reduced while preserving reliable slew rate control.
3Use of energy by moving object
If the bias current is decreased to reduce power consumption during voltage drops, then power consumption is reduced, but the rise time of the amplifier increases and waveform quality deteriorates
Solution Approach 1:
The patent optimizes the bias current parameter to achieve the best compromise between power consumption and rise time performance. By carefully controlling the bias current during voltage drops, the system reduces power consumption while maintaining acceptable rise time and waveform quality through optimized amplifier design.
Data Source
AI summary
A differential amplifier generates an output voltage waveform exhibiting a slew rate over a rise time. The amplifier is powered from a dc voltage input and includes a set of differential pairs having a bias current flowing therethrough and a Miller compensation capacitance. A comparator functions to compare a voltage at the dc voltage input against a reference voltage in order to detect when the voltage drops below the reference voltage. A gain stage controls the gain of the differential amplifier and a bias current control circuit controls the bias current of the differential amplifier. In response to the detection by the comparator of the voltage dropping below the reference voltage, the gain stage and the bias current control circuit decrease the gain of the amplifier and jointly decrease the bias current in order to maintain a value of the rise time.