Scaled Sensing Transistor Current Mirror for Switching Regulators
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Solution Overview
Problem
Current current sensing circuits in switching regulators suffer from power losses and inefficiencies due to the use of inefficient power supplies, which limits their ability to accurately sense current while maintaining high efficiency.
Innovation Solution
A current sensing circuit that utilizes a scaled sensing transistor and a current mirror to mirror the current flowing through the power stage, with the sensing transistor being powered and biased by the switching regulator, reducing power dissipation and improving efficiency by eliminating the need for additional power supplies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If traditional current sensing circuits are used in switching regulators, then current sensing function is provided, but power losses increase and efficiency decreases
Solution Approach 1:
The patent uses a sensing transistor that is a scaled-down copy of the power transistor, replicating its structure and characteristics. This copying approach allows the sensing circuit to accurately mirror the power transistor's current behavior while consuming significantly less power due to the scaled dimensions, thus resolving the contradiction between sensing accuracy and power loss.
Solution Approach 2:
The patent changes the physical parameters of the sensing transistor by scaling down its dimensions relative to the power transistor. This parameter change reduces the power consumption of the sensing circuit while maintaining proportional current sensing capability, thereby reducing power losses without completely sacrificing measurement precision.
2Ease of operation
If additional power supplies are used for current sensing circuits, then sensing functionality is enhanced, but device complexity and power consumption increase
Solution Approach 1:
The sensing transistor shares the same gate control as the power transistor and operates from the same power supply rail. This multi-functionality approach allows the sensing circuit to derive its operating voltage from the existing power supply infrastructure, eliminating the need for additional dedicated power supplies and reducing overall device complexity.
Solution Approach 2:
The current sensing circuit serves itself by using the power transistor's gate voltage to control the sensing transistor, and both transistors operate from the same power supply. This self-service mechanism eliminates the need for external power supply circuits, reducing complexity while maintaining sensing functionality.
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 configuration reduces power losses and enhances the efficiency of current sensing, allowing for more accurate monitoring of inductor current while minimizing power dissipation, thereby improving the overall performance of switching regulators.
Implementation Method 1
a current mirror configured to mirror current flowing through the third transistor
Implementation Method 2
a first resistor configured to convert the mirrored current to a current sensed signal
Data Source
AI summary
Apparatus and methods for current sensing in switching regulators include a current sensing circuit to sense current of a power stage of a power converter. The power converter can include first and second transistors. The current sensing circuit comprises a transistor that is a scaled version of one of the transistors of the power converter. A circuit of the current sensing circuit matches a drain-to-source voltage of the transistor of the current sensing circuit to the corresponding transistor of the power converter. A current mirror generates a current that mirrors the current flowing through the transistor of the current sensing circuit. A first resistor converts the mirrored current to a current sensed signal.