Coil Current Sensing via Transistor Working Point Matching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional current sensors in mobile systems face challenges in measuring high-frequency currents with low energy consumption and high accuracy, as they often require operational amplifiers with high bandwidth, leading to increased energy consumption and signal distortion due to electromagnetic interference.
Innovation Solution
A current sensor that measures the average value of a switched current within a coil using a detection transistor, a sample-and-hold circuit, and a control element to match the working points of the switching and detection transistors, allowing for low supplementary losses and reduced energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If operational amplifiers with large bandwidths are used to measure current at high clock frequencies, then measurement accuracy is improved, but current consumption increases significantly
Solution Approach 1:
The patent employs periodic sampling of the current signal synchronized with the switching frequency of the DC/DC converter. Instead of continuous measurement requiring high bandwidth, the system samples the current at specific moments during each switching period, allowing the use of lower bandwidth operational amplifiers that consume less quiescent current while still providing accurate average current measurement.
2Volume of moving object
If high switching frequency is used to reduce design volume of passive devices, then power supply efficiency is improved, but electromagnetic interference increases
Solution Approach 1:
The patent introduces an intermediary RC filtering network between the current sensor and the control circuit. This filtering network acts as a mediator that smooths out the high-frequency switching edges and electromagnetic interference, converting the noisy high-frequency signal into a cleaner average current signal that can be processed accurately without being affected by the harmful electromagnetic effects of high-frequency switching.
3Loss of energy
If average current value is used for control purposes, then system efficiency is improved, but additional complex circuitry is required
Solution Approach 1:
The patent combines the current sensing function with the existing control circuitry of the DC/DC converter. The same operational amplifier and control logic that manage the switching operation are also used to measure and regulate the average current. This merging of functions eliminates the need for separate complex average current calculation circuits, achieving energy-efficient control while maintaining circuit simplicity.
Data Source
AI summary
A method of sensing a current within a coil, said current being applied to the coil such that it is switched via a switching transistor, includes a detection transistor, a circuit and a control element. The detection transistor is configured to sense the current. The circuit is configured to provide, at a predetermined point in time during a current sensing period, a voltage across the switching transistor. The control element is configured to match, in response to the voltage provided by the circuit, the working points of the switching transistor and of the detection transistor, and to output an output signal which corresponds to the current to be sensed.