DC-DC Converter Current Sensing via Parallel Sense Transistor
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current systems for sensing current through transistors, particularly in DC-DC converters, face challenges in efficiently and accurately measuring currents across transistors, especially when dealing with high voltages and bidirectional current flows, which can lead to safety issues and inefficiencies.
Innovation Solution
A system comprising a primary transistor and a secondary transistor connected in a specific configuration, along with a current sensing module that uses a voltage difference between terminals to sense current without direct exposure to high voltages, enabling bidirectional current sensing with minimal additional terminals and reduced power consumption, and incorporating temperature compensation for accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct current sensing through the transistor is implemented, then measurement precision is improved, but the current sensing module is exposed to high voltages causing safety issues and reliability degradation
Solution Approach 1:
A sense transistor is introduced as an intermediary element to sense the current through the main power transistor. The sense transistor is electrically connected in parallel with the power transistor and shares the same gate control, allowing it to replicate the current flow at a reduced voltage level. This intermediary structure enables accurate current sensing without exposing the sensing circuitry to dangerous high voltages, thus resolving the contradiction between measurement precision and safety/reliability
Solution Approach 2:
The sense transistor creates a scaled-down copy of the current flow through the main power transistor. By matching the gate voltage and operating conditions, the sense transistor reproduces the current characteristics at a lower voltage level that is safe for sensing circuits. This copying approach maintains measurement accuracy while eliminating the high voltage exposure risk
2Adaptability or versatility
If bidirectional current sensing is implemented, then adaptability is improved, but device complexity increases due to additional terminals and circuitry
Solution Approach 1:
The sense transistor is designed with multi-functionality to handle both forward and reverse current directions. By configuring the sense transistor with appropriate body diode orientation and control circuitry, it can sense currents flowing in either direction through the main power transistor. This universal design enables bidirectional sensing without requiring separate sensing circuits for each direction, thus improving adaptability while controlling complexity
Solution Approach 2:
The sensing circuit for bidirectional current is merged into a single integrated structure using the sense transistor. The gate control circuitry is shared between the power transistor and sense transistor, and the sensing output is combined into a unified signal that represents the magnitude and direction of current flow. This merging approach achieves bidirectional sensing capability while minimizing the number of additional terminals and components required
3Measurement precision
If temperature compensation is added to improve sensing accuracy, then measurement precision is improved, but device complexity and power consumption increase
Solution Approach 1:
The sense transistor inherently provides temperature compensation through its own physical characteristics. Since the sense transistor operates under the same thermal conditions as the main power transistor and has matched semiconductor properties, its threshold voltage and current characteristics naturally track with temperature variations. This self-service approach to temperature compensation maintains measurement precision across varying temperatures without requiring external temperature sensors or complex compensation circuits, thus avoiding increased device complexity
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 solution allows for precise and efficient current sensing in both directions across transistors, reducing the risk of exposure to high voltages and minimizing power consumption, while maintaining area efficiency and cost-effectiveness.
Implementation Method 1
a current sensing module electrically connected to the transistor module and having an output terminal, wherein the current sensing module is configured to output, at the output terminal, a first output signal indicative of a current through the primary transistor in a first current direction based on a voltage difference between the third terminal and the second terminal
Data Source
AI summary
A system for sensing a current through a transistor is provided and a DC-DC converter including one or more such systems. The system includes a transistor module, including: a primary transistor electrically connected between a first and a second terminal; and a secondary transistor electrically connected between the first and a third terminal, a control terminal of the secondary transistor is electrically connected to a control terminal of the primary transistor. The system includes a current sensing module electrically connected to the transistor module and having an output terminal. The system is operable in a first mode in which the current sensing module outputs, at the output terminal, a first output signal indicative of a current through the primary transistor in a first current direction based on a voltage difference between the third and the second terminal, the first current direction being from the first to the second terminal.