Optocoupler Isolation Amplifier Current Source With Temperature Compensation
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Solution Overview
Problem
Optocoupler isolation amplifier circuits in semiconductor integrated circuits require a high-performance constant current source that remains independent of temperature changes, power supply voltage variations, and changes in process parameters, but existing designs fail to achieve this precision.
Innovation Solution
A constant current generation circuit integrated on a single substrate, comprising a start circuit, negative and positive temperature change rate current generation circuits, and a precision adjustment and output circuit, which generates and adjusts currents to meet application requirements by leveraging triodes and ion-implanted resistors with specific temperature coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional constant current source is used in optocoupler isolation amplifier, then the circuit can operate, but the current precision deteriorates due to temperature changes, power supply voltage variations, and process parameter changes
Solution Approach 1:
The constant current source is segmented into multiple functional modules: a basic current source generating circuit, a first temperature compensation circuit, and a second temperature compensation circuit. Each module performs a specific function, allowing independent optimization of current generation and temperature compensation to achieve high precision and stability simultaneously.
Solution Approach 2:
Temperature compensation circuits are introduced as intermediary elements between the basic current source and the optocoupler isolation amplifier. These compensation circuits generate compensation currents that counteract the effects of temperature variations, power supply voltage changes, and process parameter deviations, thereby maintaining current precision and stability.
2Measurement precision
If temperature compensation circuits are added to improve current precision, then current precision improves, but device complexity increases
Solution Approach 1:
The temperature compensation circuits utilize parameters such as base-emitter voltages of triodes and resistance values of resistors that have known temperature dependencies. By carefully selecting and combining these parameters, the circuits generate compensation currents that precisely counteract temperature effects without requiring complex control logic or additional components.
Solution Approach 2:
The invention exploits the thermal characteristics of semiconductor devices, specifically the temperature dependence of base-emitter voltages in triodes. The compensation circuits are designed to generate currents that increase or decrease with temperature in a controlled manner, directly counteracting the thermal drift of the main current path and maintaining current stability across temperature variations.
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 provides a high-performance constant current source that is independent of temperature changes and power supply voltage variations, ensuring current precision and stability, thereby meeting the precise requirements of optocoupler isolation amplifiers.
Implementation Method 1
the current generation circuit includes a negative temperature change rate current generation circuit and a positive temperature change rate current generation circuit
Implementation Method 2
the start circuit includes a diode D1, a resistor R1 and a diode D2 which are connected with a power supply in sequence
Data Source
AI summary
A constant current generation circuit for optocoupler isolation amplifier and a current precision adjustment method are provided. The constant current generation circuit includes a start circuit, a current generation circuit and a precision adjustment and output circuit integrated into a same substrate. The start circuit can generate and output a first start current and a second start current. The current generation circuit includes a negative temperature change rate current generation circuit connected to a first start current output and a positive temperature change rate current generation circuit connected to a second start current output. The precision adjustment and output circuit outputs constant current meeting application requirements of optocoupler isolation amplifier by adjusting proportional precision of two currents output from a current generation circuit.