Inductor Current Measurement Circuit Using Switched Sense Transistors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for measuring inductor current in electronic devices, such as DC-DC converters, either consume excessive power or are overly complex, reducing efficiency and precision.
Innovation Solution
A circuit using two power transistors and two sense transistors, with a configurable amplifier that alternates between configurations to sense current through either transistor, allowing for precise measurement of inductor current with reduced power consumption and complexity by leveraging different switching phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a series resistor is used to measure inductor current, then the current measurement is simple to implement, but power dissipation increases and efficiency decreases
Solution Approach 1:
The patent replaces the passive resistor-based current measurement (Ohm's law) with an active transistor-based sensing system. The sense transistors actively sense the current through the power transistors by replicating their behavior, substituting a mechanical/electrical passive measurement with an active electronic sensing mechanism that consumes minimal power.
Solution Approach 2:
The sense transistors create a copy of the current flowing through the power transistors. By configuring the sense transistors to mirror the behavior of the power transistors (same gate voltage, proportional current), the system obtains a copy of the inductor current signal without requiring the main current path to pass through a dissipative resistor.
2Loss of energy
If sense transistors are used to measure current through power transistors, then power dissipation is reduced, but circuit complexity increases
Solution Approach 1:
The patent merges the sensing function with the existing power transistor structure. The sense transistors are integrated alongside the power transistors, sharing the same current path and control signals. This combining of sensing and power delivery functions reduces overall circuit complexity compared to separate sensing circuits.
Solution Approach 2:
The amplifier is designed to serve multiple functions: it amplifies the sense transistor output signals and can operate in different configurations depending on which power transistor is active. This multi-functional design reduces the need for separate dedicated circuits for each sensing scenario, thereby reducing overall complexity.
3Measurement precision
If separate amplifiers are used for each sense transistor, then measurement precision is maintained, but power consumption and complexity increase
Solution Approach 1:
A single amplifier is designed to handle both sense transistor outputs by switching between different input configurations. The amplifier can be configured to amplify either the first sense transistor output or the second sense transistor output based on which power transistor is currently active, making one amplifier perform the work of two dedicated amplifiers while consuming less power and occupying less area.
Solution Approach 2:
The system operates in periodic switching phases where one power transistor is active during one phase and the other power transistor is active during another phase. The single amplifier switches between sensing configurations in sync with these periodic phases, allowing precise measurement during each phase without requiring simultaneous amplification capabilities for both channels.
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
The solution enables accurate and efficient measurement of inductor current with a single amplifier, reducing power consumption and circuit complexity while maintaining high precision, as it alternates between sensing currents through the two power transistors during different switching phases.
Implementation Method 1
The first sense transistor is coupled with a control gate to the control gate of the first power transistor and with a second electrode to the second electrode of the first power transistor
Implementation Method 2
The second sense transistor is coupled with the control gate to the control gate of the second power transistor and with the second electrode to the second electrode of the second power transistor
Implementation Method 3
The amplifier is operable to provide an output current being a function of a first current through the first sense transistor during the first period of time
Implementation Method 4
The amplifier is operable to provide the output current as a function of a second current through the second sense transistor during a second period of time
Data Source
AI summary
An electronic device includes a circuit for measuring a current in an inductor, wherein the current in the inductor is controlled by alternately switching a first power transistor and a second power transistor each having a first electrode, a second electrode and a control gate. The measuring circuit includes a first sense transistor having a first electrode, a second electrode and a control gate, the first sense transistor having the control gate coupled to the control gate of the first power transistor. A second electrode is coupled to the second electrode of the first power transistor. A second sense transistor has a first electrode, a second electrode and a control gate, the second sense transistor having the control gate coupled to the control gate of the second power transistor and having the second electrode coupled to the second electrode of the second power transistor. An amplifier is operable in a first configuration for providing an output current that is a function of a first current though the first sense transistor during a first period of time or in a second configuration for providing the output current as a function of a second current through the second sense transistor during a second period of time, so as to alternately sense a current through the first power transistor with the first sense transistor and through the second power transistor with the second sense transistor.