Auxiliary MOSFETs for Stable Current Sensing
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Solution Overview
Problem
Power MOSFETs experience instability in sizing ratio with their corresponding sense MOSFETs due to aging and high-voltage, high-current operating conditions, leading to inaccurate current measurement in power sensing applications.
Innovation Solution
A system comprising a main MOSFET and multiple auxiliary MOSFETs, where the auxiliary MOSFETs switchably couple to both the power MOSFET and a feedback voltage regulator, ensuring they experience identical electrical and switching conditions, thereby mitigating sizing ratio drift and maintaining accurate current determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single sense MOSFET is used to measure current through the power MOSFET, then the measurement system is simple, but the sizing ratio between the power MOSFET and sense MOSFET becomes unstable due to aging and hot carrier effects
Solution Approach 1:
The patent divides the sensing function across multiple auxiliary MOSFETs (first, second, and third auxiliary MOSFETs) rather than relying on a single sense MOSFET. Each auxiliary MOSFET can be selectively coupled to the power MOSFET or the amplifier, allowing the system to segment the measurement task and rotate through different sensing elements to distribute aging effects.
Solution Approach 2:
The patent changes the operational state parameters of the auxiliary MOSFETs by selectively coupling them to different circuits. The switch network dynamically changes which auxiliary MOSFET is connected to the amplifier for sensing and which are connected to the power MOSFET for aging exposure, thereby managing the sizing ratio stability through parameter variation.
2Power
If the power MOSFET operates under high-voltage, high-current conditions, then it provides sufficient power, but the hot carrier phenomena cause drift in the sizing ratio with sense MOSFETs
Solution Approach 1:
The patent applies preliminary action by exposing auxiliary MOSFETs to the same high-voltage, high-current conditions as the power MOSFET through selective coupling via the switch network. This preliminary exposure ensures that auxiliary MOSFETs experience similar hot carrier effects and aging, maintaining stable sizing ratios before they are used for sensing measurements.
Solution Approach 2:
The patent creates copies of the power MOSFET's operational conditions by coupling auxiliary MOSFETs to experience identical electrical and switching conditions. The first, second, and third auxiliary MOSFETs are alternately coupled to the power MOSFET to replicate the hot carrier phenomena and aging effects, ensuring consistent sizing ratios across all MOSFETs in the system.
3Measurement precision
If multiple auxiliary MOSFETs are used to maintain stable sizing ratios, then current measurement accuracy improves, but the device complexity increases
Solution Approach 1:
The patent implements universality by designing auxiliary MOSFETs that can serve multiple functions: they can be coupled to the power MOSFET to experience aging effects, or coupled to the amplifier to perform current sensing. The same auxiliary MOSFETs are used for both aging exposure and measurement, reducing the need for separate components and managing system complexity through multi-functionality.
Solution Approach 2:
The patent applies periodic action by rotating the coupling states of the first, second, and third auxiliary MOSFETs through the switch network. The switch network periodically changes which auxiliary MOSFET is connected to the amplifier for sensing and which are connected to the power MOSFET for aging, creating a periodic cycle that distributes wear and maintains measurement accuracy over time.
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 ensures that all MOSFETs, including auxiliary ones, experience similar hot carrier phenomena, maintaining a stable sizing ratio and enabling precise current measurement through the power MOSFET by rotating their coupling states.
Implementation Method 1
a feedback voltage regulator configured to cause a voltage at one or more of the plurality of auxiliary MOSFETs to match a voltage at the power MOSFET
Implementation Method 2
ensuring they experience identical electrical and switching conditions, thereby mitigating sizing ratio drift and maintaining accurate current determination
Data Source
AI summary
In some embodiments, a system comprises a power metal oxide semiconductor field effect transistor (MOSFET) configured to provide power in the system, a plurality of auxiliary MOSFETs, and a switch network configured to switchably and simultaneously couple a first of the plurality of auxiliary MOSFETs to the power MOSFET and a second of the plurality of auxiliary MOSFETs to a feedback voltage regulator. The switch network is further configured to switchably and simultaneously couple the first of the plurality of auxiliary MOSFETs to the feedback voltage regulator and the second of the plurality of auxiliary MOSFETs to the power MOSFET. The feedback voltage regulator is configured to cause a voltage at one or more of the plurality of auxiliary MOSFETs to match a voltage at the power MOSFET.