Multi-Sense Power Transistor Circuit for Temperature-Stable Current Sensing
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Solution Overview
Problem
Indirect measurement of high-magnitude currents in power systems, such as electronic fuses, is challenged by errors introduced due to varying parasitic resistances and gate-to-source bias in sense transistors, which affect the accuracy of load current computation with temperature changes.
Innovation Solution
The use of at least two sense transistors coupled to a power transistor with compensation resistors having different temperature coefficients, fabricated from materials like metal and polysilicon, to mitigate errors in sense current measurement and computation of load current, by compensating for parasitic resistance and temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single sense transistor is used to measure high-magnitude current indirectly, then the measurement system can compute load current from low-magnitude sense current, but measurement precision deteriorates due to errors from parasitic resistance variations and temperature changes
Solution Approach 1:
The patent divides the single sense transistor into multiple parallel sense transistors (first sense transistor and second sense transistor). Each transistor processes a portion of the sense current, and their combined measurements provide a more accurate representation of the total load current while reducing the impact of individual transistor parasitic variations
Solution Approach 2:
The patent introduces compensation resistors with different temperature coefficients (first compensation resistor with first temperature coefficient, second compensation resistor with second temperature coefficient) to actively counteract the temperature-dependent parasitic resistance changes in the sense transistors, thereby maintaining measurement accuracy across varying temperature conditions
2Measurement precision
If compensation resistors with different temperature coefficients are introduced, then measurement precision improves by compensating for parasitic resistance variations, but device complexity increases
Solution Approach 1:
The compensation resistors are integrated into the existing sense transistor circuit structure, serving dual purposes: they compensate for temperature-induced parasitic resistance changes while also functioning as part of the current sensing path. This multi-functionality reduces the need for separate compensation circuits
Solution Approach 2:
The patent combines the sense transistors and compensation resistors into an integrated circuit structure where the compensation resistors are positioned in parallel with the sense transistors. This merging approach allows the compensation function to be embedded within the sensing circuit itself, reducing overall system complexity compared to separate compensation mechanisms
Data Source
Figure 1
Figure 2(a)~3
AI summary
An electronic device comprises a first semiconductor die (102); a power transistor (104) integrated in the first semiconductor die, the power transistor comprising a first gate (104g), a first terminal (104s), and a second terminal (104d); a first sense transistor (106) integrated in the first semiconductor die, the first sense transistor comprising a second gate (106g) and third (106s) and fourth terminals (106d), the second gate coupled to the first gate and the fourth terminal coupled to the second terminal; a first resistor (106R) having a first temperature coefficient; a second sense transistor (108) integrated in the first semiconductor die, the second sense transistor comprising a third gate (108g) and seventh (l08s) and eighth (108d) terminals, the third gate coupled to the first gate and the eighth terminal coupled to the second terminal; and a second resistor (108R) having a second temperature coefficient.