Pulse Density Modulator Feedback Correction for Switch On-Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Pulse density modulators in sensing applications introduce errors due to the variation of on-resistance in power switches, which affects the linear dependence between bitstream density and sensed current.
Innovation Solution
A pulse density modulator system with a digital to analog converter and an adjuster circuit to correct errors in the data stream by adjusting the output based on the sensed parameter, using a filter circuit to generate a correction current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a pulse density modulator is used to sense current through a power switch, then the bitstream density is proportional to the average current, but the varying on-resistance of the power switch introduces measurement errors
Solution Approach 1:
The patent implements a feedback mechanism where the bitstream signal is fed back to an adjuster circuit that modifies the source current based on the bitstream density. This feedback loop compensates for errors caused by varying on-resistance by dynamically adjusting the source current to maintain accurate current measurement despite changes in switch resistance
Solution Approach 2:
The patent changes the source current parameter dynamically based on the bitstream signal to compensate for on-resistance variations. By adjusting the source current in response to detected errors, the system maintains the linear relationship between bitstream density and actual current, thereby improving measurement accuracy
2Measurement precision
If the on-resistance of the power switch varies with current, then the relationship between bitstream density and sensed current becomes non-linear, but adding correction circuits increases system complexity
Solution Approach 1:
The patent introduces an adjuster circuit as an intermediary component that sits between the digital-to-analog converter and the power switch. This intermediary modifies the source current based on the bitstream signal, providing error compensation without requiring complex changes to the core pulse density modulator architecture
Solution Approach 2:
The system uses its own output signal (the bitstream) to generate the correction needed for measurement accuracy. The bitstream is fed back to control the source current adjustment, allowing the system to self-correct for on-resistance variations without requiring external calibration or additional complex control circuits
Data Source
AI summary
A pulse density modulator encodes an electrical parameter of an external element into a data stream signal. The electrical parameter has a property which causes a predetermined error in the data stream signal. The pulse density modulator includes a digital to analog converter having a sensor element connectable to the external element, and an adjuster circuit adapted to adjust an output of the digital to analog converter based on the data stream signal to correct the predetermined error in the data stream signal. A corresponding method of correcting a data stream signal of a pulse density modulator is also presented.