Configurable Driver Circuit With Current Mirror Output Scaling
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Solution Overview
Problem
In industrial automation, programmable logic controllers and field extension modules require customized signal drives for various actuators with different voltage and current ranges, leading to the need for proprietary interfaces and separate board designs, which is inefficient and lacks a unified solution for accurate voltage-controlled current and voltage supply.
Innovation Solution
An integrated driver circuit structure that is digitally configurable to operate in current or voltage output modes, utilizing an operational amplifier, voltage-to-current converter, and current mirror, eliminating the need for a shunt resistor and instrumentation amplifier by employing dynamic element matching for high accuracy and efficient power management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional control loop with shunt resistor and instrumentation amplifier is used to measure current, then current measurement can be achieved, but the device complexity increases and voltage headroom is limited
Solution Approach 1:
The patent extracts the current sensing function from the traditional shunt resistor and instrumentation amplifier combination, and implements it through a dedicated sensing transistor integrated into the driver circuit. This removes the need for external passive components and complex amplifier circuits while maintaining accurate current measurement capability through the sensing transistor's voltage drop detection.
Solution Approach 2:
The patent merges the current sensing function with the existing driver transistor structure by using a sensing transistor that is part of the same integrated circuit block. This combines the drive function and sensing function into a single integrated unit, eliminating the need for separate external measurement components and reducing overall device complexity.
2Power
If high output current is provided to actuators, then drive capability is improved, but power efficiency deteriorates due to voltage headroom limitations
Solution Approach 1:
The patent changes the operating parameters of the sensing transistor dynamically by adjusting its width-to-length ratio (W/L) based on the required output current level. This allows the transistor to operate in optimal regions for different current levels, minimizing voltage headroom requirements and improving power efficiency while maintaining the ability to provide high output current when needed.
3Adaptability or versatility
If separate board designs are used for each actuator type, then customization accuracy is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent implements a universal driver circuit design that can accommodate multiple actuator types through software configuration rather than hardware customization. The single integrated circuit can be programmed via I2C interface to provide different current ranges, voltage levels, and control characteristics, eliminating the need for separate board designs for each actuator type while maintaining precise control capability.
4Stability of the object's composition
If external compensation components are added to the feedback loop, then stability is improved, but device complexity and board space increase
Solution Approach 1:
The patent implements self-compensation mechanisms within the integrated circuit by using the sensing transistor's inherent characteristics and internal compensation circuits that automatically adjust for stability requirements. This eliminates the need for external compensation components while maintaining feedback loop stability, as the compensation is performed internally by the circuit itself.
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 scalable output levels with high accuracy and efficiency, eliminating limitations on voltage headroom and power efficiency at high output currents, and allows for independent selection of current and voltage ranges without impacting power efficiency, enabling fast feedback loops and reduced need for external compensation.
Implementation Method 1
The output of the operational amplifier provides the gate drives for the current mirror transistors
Implementation Method 2
the feedback is closed through the current mirror and the reference current generated across the set resistor is mirrored to the output terminal
Implementation Method 3
The external control voltage determines the current available at the output terminal in the current output mode
Data Source
AI summary
An integrated circuit driver structure, comprising an amplifier, a current mirror block and an external current set resistor, is provided that is digitally configurable to operate in a current output mode or in a voltage output mode with its output level controlled by an external voltage. The current mirror block comprises multiple current sources, all having the same gate bias supplied by the output of amplifier. At any time, at least one current source is connected to supply the reference current to resistor, while all other current sources are connected to mirror the reference current to the load current output towards the load. A current gain ratio is based on the number of current sources connected to supply resistor and the number connected to mirror the reference current.