Chopper Amplifier Startup Control for Faster Stable Reference Output
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Solution Overview
Problem
Chopper amplifiers with notch filters experience significant start-up time and output overshoot/undershoot due to the chopping process, leading to increased feedback time and stabilization time in voltage reference circuits.
Innovation Solution
Incorporating a chopping delay switch and control circuit that delays the start of the chopping process until a specific voltage is within a target range, preventing overshoot by establishing feedback control and reducing stabilization time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a chopper amplifier with notch filter is used in a voltage reference circuit, then filtering effectiveness is improved, but start-up time increases and output overshoot/undershoot occurs
Solution Approach 1:
The control circuit activates the chopping function only after detecting that the operational amplifier's output has entered a target voltage range, performing the filtering action at the optimal moment rather than continuously from startup. This preliminary detection and conditional activation reduces unnecessary start-up time while maintaining filtering effectiveness when needed.
Solution Approach 2:
The control circuit continuously monitors the operational amplifier's output voltage and uses this feedback to determine when to activate the chopping function. By detecting when the output enters the target voltage range and using this information to control the chopping switch, the system achieves precise timing that prevents overshoot/undershoot while minimizing start-up delay.
2Measurement precision
If a chopper amplifier with notch filter is used in a voltage reference circuit, then filtering effectiveness is improved, but output stability deteriorates due to overshoot/undershoot
Solution Approach 1:
The control circuit uses real-time feedback from the operational amplifier's output to dynamically control the chopping switch. By monitoring whether the output voltage is within the target range and adjusting the chopping function accordingly, the system maintains output stability while preserving filtering effectiveness, preventing the overshoot and undershoot that would otherwise occur.
Solution Approach 2:
The system performs preliminary detection of the output voltage level before activating the chopping function. This preliminary action ensures that chopping is only enabled when appropriate, preventing destabilizing overshoot/undershoot events while maintaining filtering effectiveness during normal operation.
3Measurement precision
If continuous chopping is applied, then filtering effectiveness is improved, but feedback time increases
Solution Approach 1:
Instead of continuous chopping, the control circuit implements periodic or conditional chopping based on detection of the output voltage reaching the target range. This periodic activation maintains filtering effectiveness when needed while significantly reducing the overall feedback time by eliminating unnecessary continuous chopping operations during start-up and stable operation phases.
Data Source
AI summary
Embodiments of the present disclosure provide a chopper amplifier circuit that includes an operational amplifier, and a notch filter to be operated by a chopping pulse. The notch filter has a first branch that has a first capacitor, and a second branch that has a second capacitor. A chopping delay switch is connected to the first branch and the second branch of the notch filter. A control circuit is to close the chopping delay switch to short-circuit the first branch and the second branch of the notch filter to each other. The control circuit is to detect establishment of feedback signal at the chopper amplifier. The control circuit is to open the chopping delay switch, responsive to detecting establishment of the feedback signal at the chopper amplifier.