Bidirectional Transistor Current Sensing for DC-DC Converters
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Solution Overview
Problem
Existing systems for sensing current through transistors, particularly in DC-DC converters, face challenges in efficiently and accurately measuring currents across transistors without exposing the current sensing module to high voltages, and in implementing bidirectional current sensing in a cost-effective and area-efficient manner.
Innovation Solution
A system comprising a primary transistor and a secondary transistor connected between terminals, with a current sensing module that uses a voltage difference between terminals to sense current direction, allowing for bidirectional sensing without direct connection to high-voltage terminals, and includes a temperature compensation unit to adjust the on-resistance of the compensation transistor, enabling efficient and accurate current sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the current sensing module is directly connected to high-voltage terminals to sense current, then the current measurement accuracy is improved, but the sensing module is exposed to high voltages which reduces system reliability
Solution Approach 1:
The patent introduces an intermediary sensing transistor connected in parallel with the power transistor. This sensing transistor acts as a mediator that allows current sensing without directly exposing the sensing module to high voltages. The voltage difference across the sensing transistor terminals reflects the current through the power transistor, enabling accurate measurement while maintaining electrical isolation and protecting the sensing module.
2Adaptability or versatility
If a secondary sensing transistor is added to enable bidirectional current sensing, then the sensing capability is improved, but the device complexity and area increase
Solution Approach 1:
The sensing transistor is designed with multi-functionality to perform both directional current sensing operations. By controlling the potential at the third terminal, the same sensing transistor structure can sense current in both directions (first current direction and second current direction), eliminating the need for separate sensing circuits for each direction and reducing overall device complexity.
Solution Approach 2:
The patent uses a simplified copy approach where the sensing transistor replicates the essential current-sensing function without needing to be a full-scale power transistor. This copying principle allows the sensing transistor to be smaller and less complex while still accurately reflecting the current through the power transistor, reducing area and complexity overhead.
3Measurement precision
If the on-resistance of the sensing transistor is not compensated for temperature variations, then the device simplicity is maintained, but the measurement precision deteriorates due to temperature-dependent resistance changes
Solution Approach 1:
The patent implements a temperature compensation mechanism that uses feedback to adjust the sensing transistor's on-resistance. A temperature compensation unit monitors temperature variations and applies compensation signals to maintain a substantially temperature-independent on-resistance. This feedback approach ensures accurate current sensing across different operating temperatures while keeping the compensation circuit relatively simple.
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 effective and efficient bidirectional current sensing in a cost-effective and area-efficient manner, minimizing power consumption and protecting the system from high voltages, while maintaining accurate current measurement across transistors.
Implementation Method 1
a current sensing module electrically connected to the transistor module and having an output terminal. The system is configured to be operable in a first mode in which the current sensing module is configured to output, at the output terminal, a first output signal indicative of a current through the primary transistor
Implementation Method 2
includes a temperature compensation unit to adjust the on-resistance of the compensation transistor, enabling efficient and accurate current sensing
Data Source
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AI summary
Aspects of the present disclosure generally relate to a system for sensing a current through a transistor. Aspects of the present disclosure further relate to a DC-DC converter comprising one or more such systems. The system according to the present disclosure comprises a transistor module, comprising: a primary transistor electrically connected between a first terminal and a second terminal; and a secondary transistor electrically connected between the first terminal and a third terminal, wherein a control terminal of the secondary transistor is electrically connected to a control terminal of the primary transistor. The system further comprises a current sensing module electrically connected to the transistor module and having an output terminal. The system is configured to be operable in a first mode in which 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, the first current direction being from the first terminal to the second terminal.