Voltage Controlled Current Source with Dynamic Element Matching
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Solution Overview
Problem
Voltage controlled current source devices face limitations due to the need for high accuracy and low drift in shunt resistors and instrumentation amplifiers, which increase costs and reduce voltage headroom and power efficiency, and require complex compensation to maintain performance across varying current levels.
Innovation Solution
A voltage controlled current source device utilizing a current mirror with dynamic element matching, eliminating the need for a shunt resistor and instrumentation amplifier, and employing a clock-controlled switching arrangement to cycle current sources for improved accuracy and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a shunt resistor and instrumentation amplifier are used to sense and measure load current, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts and eliminates the shunt resistor and instrumentation amplifier from the feedback loop, replacing them with a simplified current sensing mechanism that uses the existing operational amplifier feedback to directly control the current through the load, thereby reducing device complexity while maintaining measurement precision
Solution Approach 2:
The operational amplifier in the feedback loop serves multiple functions: it both regulates the voltage to maintain accurate current control and senses the load current simultaneously, eliminating the need for separate measurement components and reducing overall device complexity
2Measurement precision
If high accuracy shunt resistors and instrumentation amplifiers are used, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent replaces expensive, high-precision shunt resistors and instrumentation amplifiers with simpler, lower-cost components that achieve the same measurement accuracy through the feedback mechanism, significantly reducing manufacturing cost while maintaining measurement precision
Solution Approach 2:
The patent uses the feedback voltage across the current set resistor as a proxy for direct current measurement, copying the current information through voltage measurement in a controlled loop, which allows using less precise but cheaper components while maintaining accuracy
3Measurement precision
If a shunt resistor is used to sense load current, then measurement precision is improved, but voltage headroom is reduced
Solution Approach 1:
The feedback voltage across the current set resistor serves dual purposes: it provides accurate current sensing information and simultaneously regulates the output voltage to maintain proper operating conditions, eliminating the need for additional voltage drops and preserving voltage headroom
4Measurement precision
If a shunt resistor and instrumentation amplifier are used, then measurement precision is improved, but power efficiency is reduced
Solution Approach 1:
The patent removes the power-hungry instrumentation amplifier from the circuit and replaces it with a simplified sensing approach that uses the operational amplifier's existing feedback capability, significantly reducing power consumption while maintaining measurement precision
Solution Approach 2:
The feedback loop uses the voltage drop across the current set resistor to automatically regulate and sense the current without requiring additional active components, making the system self-sufficient and minimizing power loss
5Adaptability or versatility
If the potential at the load changes significantly, then adaptability is improved, but common mode rejection requirements increase
Solution Approach 1:
The patent employs a feedback mechanism where the operational amplifier continuously monitors the voltage across the current set resistor and adjusts the gate voltage to maintain constant current flow, automatically compensating for load potential changes and maintaining measurement precision across a wide adaptability range
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
This solution achieves high accuracy and efficiency across a wide range of output currents without reducing voltage headroom or power efficiency, and simplifies the feedback loop, reducing the need for additional compensation.
Implementation Method 1
a current mirror that mirrors the reference current from the selected leg(s) of the current mirror to the load output current
Implementation Method 2
a dynamic element matching approach employed in the current mirror ensures high accuracy throughout a large range of the output current
Implementation Method 3
causing a reference current to flow through the current set resistor
Data Source
AI summary
An integrated voltage controlled current source device is provided, that extends the high accuracy, low drift output current over a large current range, and provides more headroom and better power efficiency than the standard shunt resistor and INA (instrumentation amplifier) current source arrangement. The device has a control voltage input, a load current output and a current set terminal for a connection of a current set resistor. It contains a selected leg biasing set voltage, corresponding to a control voltage applied to the control voltage input of a regulating driver amplifier providing a regulated voltage to be applied across the current set resistor, thereby causing a reference current to flow through the current set resistor and selected leg(s) of a current mirror. Furthermore, the device contains a dynamically matched current mirror that mirrors the reference current to the load output current. The algorithm for selecting the current mirror legs may be a pseudo-random or a defined pattern.