Current Sensing Circuit for Load Switch with Voltage-Dependent Adjustment
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Solution Overview
Problem
Current sensing circuits struggle to precisely measure current through load switches, especially when the output voltage is low or decreasing, leading to inaccurate readings, particularly in the saturation region of MOSFETs.
Innovation Solution
A current sensing circuit comprising a first circuit coupled to the load switch through a resistor and a second circuit that generates an adjusting current based on the output voltage, maintaining a predetermined ratio of currents when the output voltage is below a threshold, allowing precise current calculation regardless of the load switch's operation region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional current sensing circuit is used to sense current through a load switch, then the circuit structure is simple, but the current measurement precision deteriorates when the output voltage is low or decreasing
Solution Approach 1:
The patent introduces a second circuit as an intermediary component that generates an adjusting current based on the output voltage. This adjusting current is superimposed on the sensing current to maintain a predetermined ratio relationship, thereby enabling accurate current measurement even when the output voltage is low. The intermediary circuit acts as a mediator between the voltage condition and the current sensing mechanism.
Solution Approach 2:
The patent dynamically changes the sensing current parameter by adding an adjusting current that is generated according to the output voltage. When the output voltage is low, the adjusting current compensates to maintain the predetermined ratio. This parameter change approach allows the sensing system to adapt to varying voltage conditions and maintain measurement precision.
2Reliability
If the load switch operates in saturation region due to low output voltage, then the voltage condition is maintained, but the current sensing accuracy deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the second circuit continuously monitors the output voltage and generates an adjusting current accordingly. When the output voltage is low causing the load switch to operate in saturation region, the feedback loop adjusts the sensing current to maintain the predetermined ratio, thereby preserving current sensing accuracy despite the changed operating condition.
3Productivity
If the output voltage decreases due to load power consumption, then the load power supply is maintained, but the current measurement precision deteriorates
Solution Approach 1:
The patent introduces dynamic adaptability to the current sensing circuit through the second circuit that generates an adjusting current based on real-time output voltage conditions. As the output voltage dynamically changes due to load power consumption, the adjusting current dynamically compensates to maintain the predetermined ratio, enabling the system to adapt to varying productivity conditions while preserving measurement precision.
Data Source
AI summary
Disclosed is a current sensing circuit to sense a current flowing through a load switch. The load switch receives a supply voltage to generate an output voltage. The current sensing circuit includes a first circuit and a second circuit. The first circuit is coupled the load switch through a first resistor, and senses the current flowing through the load switch. The second circuit is coupled to the first circuit and the load switch, senses the output voltage, and generates an adjusting current according to the output voltage. The second circuit generates the adjusting current when the output voltage is smaller than a threshold voltage, such that the ratio of the current flowing through the load switch to a current flowing through the first circuit is maintained at certain ratio, but the second circuit is disabled when the output voltage is larger than or equal to the threshold voltage.