Current-to-Voltage Conversion Circuit for Stable Digital Isolation
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Solution Overview
Problem
The power supply voltage in digital isolators based on OOK modulation is sensitive to frequency changes, affecting the normal operation and accuracy of signal transmission due to variations in input current and temperature.
Innovation Solution
A current-to-voltage conversion circuit using MOS transistors operating in the sub-threshold region, coupled with a voltage regulation circuit comprising an operational amplifier and a voltage regulation switch, adjusts the power supply voltage based on input current thresholds to maintain stability and precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional current-to-voltage conversion circuit is used, then the circuit can operate with simple structure, but the generated power supply voltage is sensitive to temperature and process variations, affecting frequency stability
Solution Approach 1:
The patent changes the operating parameter of MOS transistors from above-threshold to sub-threshold region. This parameter change enables the voltage generation circuit to produce temperature-compensated output voltage while maintaining reasonable circuit complexity. The sub-threshold operation provides inherent temperature compensation characteristics that improve frequency stability without requiring complex additional circuits.
Solution Approach 2:
The patent implements a feedback mechanism using an operational amplifier that monitors the output voltage and adjusts the gate voltage of the MOS transistor accordingly. This closed-loop feedback system compensates for temperature and process variations, maintaining stable power supply voltage and thus stable frequency output, while the feedback circuit complexity is justified by the significant improvement in reliability.
2Productivity
If the power supply voltage varies with input current, then the circuit can respond dynamically to input changes, but the frequency of the high-frequency carrier signal changes, affecting normal operation
Solution Approach 1:
The operational amplifier in the patent provides continuous feedback control that adjusts the MOS transistor gate voltage in response to input current changes while maintaining constant output voltage. This feedback mechanism allows the circuit to respond dynamically to input variations (maintaining productivity) while keeping the power supply voltage stable (maintaining reliability and frequency stability).
Solution Approach 2:
The patent utilizes the sub-threshold region operation of MOS transistors, where small changes in gate voltage produce controlled changes in drain current. This parameter regime allows for high-gain transconductance that enables rapid response to input current changes while the feedback loop maintains stable output voltage, thus achieving both fast response and operational stability.
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 circuit generates a high-precision voltage that is insensitive to temperature and process variations, enhancing the stability and transmission reliability of digital isolators by maintaining consistent power supply voltage.
Implementation Method 1
The current-to-voltage conversion circuit can generate a high-precision voltage by using MOS transistors (such as M1 and M2) working in a sub-threshold region
Implementation Method 2
a voltage regulation circuit, comprising an operational amplifier and a voltage regulation switch device, a control end of the voltage regulation switch device is coupled to an output end of the operational amplifier
Data Source
AI summary
A current-to-voltage conversion circuit used in a digital isolator. The current-to-voltage conversion circuit has an input terminal to receive an input current, an output terminal to output a power supply voltage generated based on the input current. The current-to-voltage conversion circuit has an operational amplifier and a voltage regulation switch device, the voltage regulation switch device has a control end coupled to an output end of the operational amplifier. When the input current is less than an adjustment threshold, the voltage regulation switch device is turned off, and when the input current is greater than the adjustment threshold, the voltage regulation switch device is turned on.