Current Sensor Circuit with Extended Voltage Range
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Solution Overview
Problem
Current sensor circuits face challenges in accurately sensing current over a wide voltage range, particularly during low voltage conditions such as short-circuit scenarios, due to limitations in replicating source voltage across transistors without complex negative charge-pump circuits.
Innovation Solution
A current sense circuit design that includes a copy transistor and an error amplifier to maintain voltage equality across transistors, allowing accurate current sensing without a negative charge-pump, by using a current-to-voltage converter and error amplifier to manage voltage levels across the circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a negative charge-pump circuit is used to replicate source voltage across transistors, then accurate current sensing is achieved, but device complexity increases
Solution Approach 1:
The patent extracts and eliminates the negative charge-pump circuit from the system by using an alternative approach. The error amplifier directly compares source voltages and controls the copy transistor gate to maintain voltage equality without requiring voltage inversion or charge pumping, thereby removing the complex charge-pump components while preserving current sensing accuracy.
Solution Approach 2:
The error amplifier serves as an intermediary device that mediates between the output transistor source voltage and the copy transistor source voltage. It continuously compares these voltages and adjusts the copy transistor gate voltage to maintain equality, enabling accurate current sensing through a simpler direct comparison mechanism rather than complex voltage replication.
2Adaptability or versatility
If the circuit supports a wide voltage range (5V to 18V), then adaptability is improved, but maintaining accurate sensing across this range becomes more difficult
Solution Approach 1:
The patent employs parameter changes by allowing the error amplifier and transistors to operate across different voltage conditions (5V to 18V). The error amplifier dynamically adjusts its operation to maintain source voltage equality regardless of the input voltage level, enabling the circuit to adapt to wide voltage variations while preserving sensing accuracy through continuous parameter adjustment rather than fixed operating conditions.
Data Source
AI summary
In an embodiment, a current sense circuit includes a copy transistor having a gate configured to be coupled to a gate of an output transistor, and a drain coupled to an input terminal. The drain of the copy transistor is configured to be coupled to a drain of the output transistor. A first transistor has a current path coupled to a current path of the copy transistor. An error amplifier has a non-inverting input coupled to a source of the copy transistor, an inverting input configured to be coupled to a source of the output transistor, an output coupled to a gate of the first transistor, a positive power supply terminal coupled to the input terminal and a negative power supply terminal coupled to a reference supply terminal. A current-to-voltage converter has an input coupled to the current path of the copy transistor.