Current Control Circuit with Resistive DAC Feedback for Fast Accuracy

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Solution Overview

Problem

Current control circuitries for loads like LEDs face limitations in accuracy and speed of current control due to reliance on matched MOSFET devices and feedback loop bandwidth, which restrict high-rate and high-accuracy current adjustments.

Innovation Solution

The proposed current control circuitry employs a MOSFET device with a variable resistance implemented as a resistive digital-to-analogue converter (DAC) for precise current control, allowing digital code input to adjust resistance synchronously with a clock signal, and incorporates a feedback path to adjust amplifier output voltage, enabling faster and more accurate current regulation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If matched MOSFET devices are used for current control, then device reliability is improved, but current control accuracy and speed are limited by feedback loop bandwidth

Engineering Contradiction:

Improvedevice reliabilityVSAvoidcurrent control accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent replaces the traditional MOSFET-based current control mechanism with a resistive DAC mechanism. Instead of relying on MOSFET gate voltage control and feedback loop amplification, the invention directly controls current through digital-to-analogue conversion via resistance modulation, eliminating the bandwidth limitations of amplifier-based feedback systems while maintaining reliability through established resistive technology.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention changes the fundamental control parameter from MOSFET gate voltage to resistive element resistance value. By modulating the resistance of the DAC output directly in proportion to the digital input code, the system achieves current control accuracy determined by the DAC resolution rather than feedback loop bandwidth, enabling higher precision and faster response.

Inventive Principle:

Principle #35Parameter changes

2Speed

If feedback loop bandwidth is increased for faster current adjustment, then current control speed is improved, but accuracy deteriorates due to MOSFET matching limitations

Engineering Contradiction:

Improvecurrent control speedVSAvoidcurrent control accuracy

Core Design Contradiction:

SpeedVSMeasurement precision

Solution Approach 1:

The patent substitutes the MOSFET feedback control system with a direct resistive DAC control system. The resistive DAC provides instantaneous current adjustment proportional to digital input without requiring high-bandwidth amplifiers or feedback loops, achieving both high speed and high accuracy simultaneously by eliminating the trade-off inherent in MOSFET-based systems.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Device complexity

If traditional MOSFET-based current control is used, then circuit simplicity is maintained, but current adjustment accuracy and rate of change are restricted

Engineering Contradiction:

Improvecircuit simplicityVSAvoidcurrent adjustment rate

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The invention replaces complex MOSFET gate control circuits with a simpler resistive DAC architecture. The resistive DAC directly converts digital codes to proportional resistance values, providing accurate and fast current adjustment without requiring matched MOSFET pairs, high-bandwidth amplifiers, or complex feedback networks, thus improving productivity while maintaining reasonable circuit complexity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 enables faster and more accurate control of load current, independent of MOSFET matching accuracy, with a higher rate of change and improved precision compared to traditional circuitries, suitable for applications requiring high-speed and high-accuracy current adjustments.

Implementation Method 1

a variable resistance implemented as a resistive digital-to-analogue converter (DAC) for precise current control, allowing digital code input to adjust resistance synchronously with a clock signal

Methodology Applied

Scientific EffectDigital-to-Analogue Conversion:

Implementation Method 2

incorporates a feedback path to adjust amplifier output voltage, enabling faster and more accurate current regulation

Methodology Applied

Scientific EffectFeedback: Feedback

Implementation Method 3

The current sense resistor is configured to generate a signal indicative of the current through the load

Methodology Applied

Scientific EffectOhm's Law: Ohm's Law

Data Source

PatentUS11477868B2Current control circuitry

Publication Date: 2022.10.18 CIRRUS LOGIC INC

AI summary

The present disclosure relates to current control circuitry for controlling a current through a load. The current control circuitry comprises amplifier circuitry, reference voltage generator circuitry configured to supply a fixed reference voltage to a first input of the amplifier circuitry and an output stage comprising: a control terminal coupled to an output of the amplifier circuitry; a current input terminal configured to be coupled to the load; and a current output terminal. The current control circuitry further comprises a variable resistance coupled to the current output terminal of the output stage, and a feedback path between the current output terminal of the output stage and a second terminal of the amplifier circuitry for providing a feedback voltage to a second input of the amplifier circuitry.