Dual Current Sensing Circuit With Shared Transconductance Stage
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Solution Overview
Problem
Conventional systems require separate circuits for high-side and low-side current sensing, leading to additional cost and frequent mismatches in current sense gain, which are not effectively addressed.
Innovation Solution
A single transconductance stage is used to measure both high-side and low-side current flows through a load by alternating the operation of high-side and low-side FET components, with a single circuit configured to input signals from the voltage drop across either component and output corresponding current flow signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two entirely separate circuits are employed for sensing high-side and low-side current, then both current flows can be measured, but the cost increases and mismatches in current sense gain occur
Solution Approach 1:
The patent combines two separate current sensing circuits into a single integrated circuit that can sense both high-side and low-side current flows. The single circuit includes a transconductance stage that processes voltage drops from either the high-side FET or low-side FET through switching mechanisms, eliminating the need for two independent sensing circuits while maintaining measurement accuracy and gain matching.
Solution Approach 2:
The single current sensing circuit is designed to perform multiple functions: it can sense current flow through the high-side FET, sense current flow through the low-side FET, and provide matched gain for both sensing paths. The circuit achieves this universality through a shared transconductance stage and switching architecture that routes signals from either FET to the same processing path.
2Device complexity
If a single circuit is used to measure both high-side and low-side current flows, then cost is reduced and gain matching is improved, but the circuit must alternate between sensing modes
Solution Approach 1:
The patent implements periodic switching between high-side and low-side sensing modes using control signals that alternately activate the high-side FET and low-side FET. The switching mechanism rapidly transitions between sensing the voltage drop across the high-side FET and the voltage drop across the low-side FET, providing continuous current monitoring through time-division multiplexing.
Solution Approach 2:
The circuit employs dynamic switching mechanisms that allow the sensing path to change state between high-side and low-side configurations. Control signals dynamically enable or disable specific FETs and routing paths based on which current flow needs to be sensed at any given moment, allowing a single static circuit to perform dynamic sensing functions.
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
This approach eliminates the need for separate circuits, reduces cost, and minimizes mismatches in current sense gain by using a single circuit to accurately measure both high-side and low-side current flows.
Implementation Method 1
a single transconductance stage is configured to: input signals indicating a voltage drop across whichever one of the high-side FET component or the low-side FET component currently is on, and output a signal indicating a current flow that corresponds to such voltage drop
Data Source
AI summary
Provided is a current-sensing circuit that includes a power-supply line providing electrical power to a high side of a load, a high-side field-effect transistor (FET) component between the power-supply line and the high side of the load, and a low-side FET component coupled to a low side of the load. Gate signals continually repeat a cycle that includes: a first part in which the high-side FET component is turned on and the low-side FET component is turned off, and a second part in which the high-side FET component is turned off and the low-side FET component is turned on. In addition, a single transconductance stage is configured to: input signals indicating a voltage drop across whichever one of the high-side FET component or the low-side FET component currently is on, and output a signal indicating a current flow that corresponds to such voltage drop.