Operational Amplifier Saturation Prevention Circuit
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Solution Overview
Problem
Existing current measurement circuits face challenges in preventing operational amplifier saturation and recovering from it quickly, especially when measuring low currents, due to large current detection resistors and parasitic capacitors, leading to prolonged stabilization times and potential saturation during sudden voltage changes.
Innovation Solution
A current measurement circuit with a saturation prevention and recovery circuit that includes shunt circuits with diodes and resistors connected in parallel with the current detection resistor, allowing for high-speed self-detection and control operations to adjust resistance dynamically and prevent amplifier saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large resistance current detection resistor is used to measure low current, then measurement precision is improved, but the operational amplifier takes longer to recover from saturation and stabilize
Solution Approach 1:
The patent applies dynamics by making the current detection resistance variable rather than fixed. The circuit dynamically switches between a large resistance value (for low current measurement precision) and a small resistance value (for fast stabilization) based on the operational amplifier's saturation state and current measurement requirements, resolving the contradiction between measurement precision and stabilization time
Solution Approach 2:
The patent changes the resistance parameter of the current detection resistor from a fixed large value to a variable value that can switch between large and small resistance states. This parameter change allows the circuit to optimize for either measurement precision or stabilization speed depending on the operating conditions
2Measurement precision
If a large resistance current detection resistor is used, then low current measurement capability is improved, but the load current cannot be large and stabilization is slow
Solution Approach 1:
The circuit dynamically adjusts the current detection resistance based on load current requirements. When high load current is needed, the resistance switches to a small value to enable fast stabilization and high productivity. When low current measurement is needed, the resistance switches to a large value for precise measurement capability
3Ease of operation
If parasitic capacitors are present in the circuit, then circuit functionality is maintained, but large transient current flows during voltage changes causing operational amplifier saturation
Solution Approach 1:
The patent applies preliminary anti-action by detecting the saturation state of the operational amplifier in advance and proactively switching the current detection resistance to a small value before the saturation fully develops. This preventive measure counteracts the harmful effect of transient current caused by parasitic capacitors during voltage changes
4Adaptability or versatility
If reed relays are used to switch current detection resistors, then resistance changing is achieved, but the operation speed is slow and saturation cannot be prevented in time
Solution Approach 1:
The patent replaces the mechanical reed relay switching system with an electronic switching mechanism controlled by saturation detection circuitry. This substitution eliminates the mechanical inertia and slow response of reed relays, enabling rapid detection and response to saturation conditions
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 prevents operational amplifier saturation and reduces recovery time by dynamically adjusting resistance, enabling faster stabilization of load current and preventing amplifier saturation, even during sudden voltage changes.
Implementation Method 1
a shunt circuit including a diode and a resistor connected in parallel with the current detection resistor
Data Source
AI summary
A current measurement circuit includes: a constant-voltage loop circuit including an operational amplifier, and a first resistor for current detection connected to an output of the operational amplifier, the output of the operational amplifier being fed back to an inverting input terminal of the operational amplifier via the first resistor; a differential amplifier for current detection with an input of a voltage between both ends of the first resistor; and a saturation prevention and recovery circuit connected to the both ends of the first resistor for preventing saturation of the operational amplifier and/or accelerating recovery from the saturation thereof.