Digitally Programmable Current Control Circuit for Fast Accurate Load Drive
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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 restricts high-rate and high-accuracy current adjustments.
Innovation Solution
The implementation of current control circuitry using amplifier circuitry with a variable resistance based on digital codes, a resistive digital-to-analogue converter (DAC), and a feedback path for precise current control, allowing for independent adjustment of load current through the variable resistance rather than relying on MOSFET matching, thereby enhancing speed and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If matched MOSFET devices are used for current control, then device simplicity is maintained, but current control accuracy and speed are limited
Solution Approach 1:
The patent replaces the mechanical/electronic matching approach (using matched MOSFET devices) with a digital control approach (using a DAC and amplifier circuitry). The digital code input to the DAC allows precise control of the resistance value, thereby achieving accurate current control without relying on MOSFET matching. This substitution of control methodology resolves the contradiction by prioritizing accuracy over circuit simplicity.
2Speed
If feedback loop bandwidth is increased for faster current adjustment, then current control speed improves, but system stability and accuracy deteriorate
Solution Approach 1:
The patent segments the current control function into two independent parts: a digital-to-analogue conversion stage (DAC) that determines accuracy, and an amplifier stage that determines speed. The DAC converts digital codes to precise resistance values, while the amplifier provides high-bandwidth current amplification. This segmentation allows each stage to be optimized independently, resolving the contradiction between speed and accuracy.
Solution Approach 2:
The patent introduces an intermediary amplifier circuit between the DAC and the load. The amplifier acts as a buffer that isolates the high-precision DAC from the high-speed current delivery requirement. The amplifier's high bandwidth enables fast current adjustment without affecting the DAC's precision, thus resolving the speed-accuracy trade-off.
3Productivity
If MOSFET matching is relied upon for current control, then circuit design is simplified, but high-rate current adjustments are restricted
Solution Approach 1:
The patent introduces dynamic control through a digitally programmable resistance (DAC) that can be rapidly adjusted by changing digital codes. Unlike static MOSFET matching, the DAC allows the resistance value to be dynamically changed at high rates according to digital input signals. This dynamic control mechanism enables high-rate current adjustments while accepting increased circuit complexity as the trade-off for improved productivity.
Data Source
AI summary
The present disclosure relates to current control circuitry for controlling a current through a load, the current control circuitry comprising: amplifier circuitry; reference voltage generator circuitry configured to supply a fixed reference voltage to a first input of the amplifier circuitry; 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; a current output terminal; a clock-controlled variable resistance coupled to the current output terminal of the output stage, wherein a resistance of the variable resistance is based on a digital code input to the variable resistance; 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.