Split Control Node Power Transistor Current Sensing
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Solution Overview
Problem
Power transistor modules face challenges in accurately measuring current while minimizing power consumption, especially in switching mode applications like buck converter power supplies.
Innovation Solution
A power transistor module design featuring a split control node and interconnect clips, with a current sense resistor (shunt) in series, allows for accurate current estimation through voltage drop measurement, while maintaining a desired power consumption level by configuring the ratio of transistor portions and using optional bias compensation circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a current sense resistor is used to measure current through the power transistor, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The power transistor is divided into two portions with different area ratios (5% to 75%), allowing the system to measure current through a smaller effective area while maintaining overall power handling capability. The first portion carries a proportional share of the total current that can be accurately measured, while the second portion handles the remaining current, thus reducing the power dissipation in the sensing path while preserving measurement accuracy.
2Measurement precision
If the area ratio of the first portion to the second portion is set between 5% to 75%, then measurement precision is improved, but device complexity increases
Solution Approach 1:
Different portions of the power transistor are assigned different functional qualities: the first portion is optimized for current sensing with a smaller area suitable for accurate measurement, while the second portion is optimized for power handling with a larger area. This local differentiation allows the device to simultaneously achieve precise current measurement and high power capability without requiring entirely separate sensing and power transistor structures.
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 design enables precise current measurement with controlled power consumption, achieving the desired accuracy and efficiency in power transistor modules.
Implementation Method 1
A current sense resistor, referred to as a shunt, is coupled in series to the first clip. A voltage drop across the shunt is used to estimate current through the first portion of the power transistor.
Data Source
AI summary
A power transistor module including a power transistor with a first common power node, and a split control node. A first clip is connected to a portion of a second power node so that current through a first control segment of the control node is directed through a first transistor portion and through the first clip. A second clip is connected to another portion of the second power node so that current through a second control segment is directed through a second transistor portion and through the second clip. A ratio of an area of the first transistor portion to a combined area of the first and second portions is 5 percent to 75 percent. A shunt is coupled in series to the first clip. The shunt may be directly electrically connected to the first portion of the power transistor.