Virtual-Ground Current Detection Circuit for Load Drive Accuracy
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Solution Overview
Problem
Current current detection circuits in load drive control devices experience amplification errors due to common mode voltage fluctuations and detection errors due to currents not passing through the detection resistor, particularly in configurations using silicon on insulator (SOI) processes which are costly and inefficient.
Innovation Solution
A current detection circuit with a detection resistor between the driver circuit and the load, a power supply circuit operating between a first power supply and a virtual ground potential to generate a second power supply, and a signal processing circuit operating between the second power supply and the virtual ground potential, with a virtual ground line connected between the driver circuit and the detection resistor, reducing amplification errors and detection errors without using the SOI process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional current detection circuit is used with a detection resistor, then current detection is achieved, but amplification errors occur due to common mode voltage fluctuations
Solution Approach 1:
The patent introduces a virtual ground potential as an intermediary reference point between the detection resistor and the amplifier. This virtual ground acts as a mediator that stabilizes the common mode voltage at the amplifier input, preventing common mode voltage fluctuations from causing amplification errors while maintaining accurate current detection through the detection resistor.
2Measurement precision
If the amplifier and AD converter are located in an area surrounded by an insulator layer on an SOI substrate, then current detection accuracy is improved, but manufacturing costs increase
Solution Approach 1:
The patent replaces the expensive SOI substrate process with a conventional substrate approach combined with a virtual ground potential technique. Instead of using costly specialized substrates with insulator layers, the invention achieves similar noise isolation and accuracy using a virtual ground reference, making the solution more economically viable for mass production.
3Measurement precision
If the current consumed by the signal processing circuit flows through the detection resistor, then detection accuracy is improved, but the circuit complexity increases
Solution Approach 1:
The detection resistor serves multiple functions simultaneously: it detects the output current to the load and also carries the current consumed by the signal processing circuit (amplifier and AD converter). This multi-functionality ensures that all currents are accounted for in the detection, improving accuracy without requiring separate detection paths or additional components.
Solution Approach 2:
The virtual ground potential acts as an intermediary that enables the signal processing circuit to be powered from the same detection path without creating separate current loops. By providing a stable reference potential, it allows the amplifier and AD converter to draw current through the detection resistor while maintaining proper biasing and signal integrity.
Data Source
AI summary
A current detection circuit includes: a detection resistor provided between an output of a driver circuit and a load; a power supply circuit configured to operate between a first power supply and a virtual ground potential, and generate a second power supply having a predetermined voltage difference from the virtual ground potential; and a signal processing circuit configured to operate between the second power supply and the virtual ground potential, and generate a detection signal corresponding to a voltage generated at the detection resistor. A virtual ground line for supplying the virtual ground potential is connected between the output of the driver circuit and the detection resistor.