RDSON Correction for Accurate Current Sensing in MOS Transistor Switches
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Solution Overview
Problem
Conventional switching power supplies fail to accurately calculate current through MOS transistor switches due to variability in on-state resistance (RDSON), which is influenced by device characteristics and temperature, leading to inaccurate current determination.
Innovation Solution
A driver with RDSON correction, incorporating an on-chip temperature sensor, processing device, and correction functions, calculates a corrected RDSON voltage drop by applying temperature and voltage correction factors, allowing for precise current determination using Ohm's Law.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional current sensing is used without RDSON correction, then the device complexity is low, but the measurement precision of current is inaccurate
Solution Approach 1:
The patent applies parameter changes by measuring RDSON at multiple temperatures and gate drive voltages to create a comprehensive correction table. This allows the system to select appropriate correction parameters based on actual operating conditions, significantly improving current measurement accuracy while managing complexity through structured data organization
Solution Approach 2:
The patent introduces an intermediary correction mechanism that measures RDSON voltage drop separately and uses it to calculate accurate current. The correction table acts as a mediator between temperature/voltage conditions and current calculation, enabling precise measurement without directly complicating the main current sensing path
2Measurement precision
If RDSON correction with temperature sensing is implemented, then the measurement precision of current is improved, but the device complexity increases
Solution Approach 1:
The patent implements self-service by using an on-chip temperature sensor to automatically monitor and compensate for temperature effects on RDSON. The system self-adjusts correction parameters based on measured temperature, eliminating the need for external temperature compensation circuits and reducing overall system complexity despite added measurement capability
Solution Approach 2:
The patent merges the temperature sensing function and RDSON correction logic into the existing driver circuit. By combining these functions within the same integrated circuit, the patent reduces the need for separate discrete components and simplifies the overall system architecture while maintaining high measurement precision
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
Enables accurate current measurement through MOS transistor switches by accounting for RDSON variability, improving control and reporting in switching power supplies.
Implementation Method 1
Analog-to-digital (A/D) converter 304 receives an output signal from an on-chip temperature sensor 302
Implementation Method 2
the current through the switch can be determined according to Ohm's Law, V=I*R
Data Source
AI summary
Current sensing with RDSON correction is disclosed. In an embodiment, a method comprises: measuring an approximate temperature of a MOS transistor switch by a temperature sensor to yield a measured temperature; calculating a corrected temperature from the measured temperature using a stored temperature sensor gain and offset correction function; measuring a gate drive voltage for the MOS transistor; calculating a voltage correction factor using a stored voltage correction function, wherein the stored voltage correction function is a function of the corrected temperature and the gate drive voltage; measuring a RDSON voltage drop across the MOS transistor switch to yield a measured RDSON voltage drop; and calculating the current using the measured RDSON drop and the voltage correction factor.