Inductor Current Sensing via Switching Node Voltage
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Solution Overview
Problem
Accurate average output current regulation in high efficiency power supplies is challenging due to the addition of sense elements, which increase circuit size and cost.
Innovation Solution
A power conversion system with a regulator circuit and a compensation sense circuit that generates a compensation pulse signal representing the percentage of time the inductor current is above a threshold, allowing for current compensation and regulation without external sensing circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sense element is used for accurate average output current regulation, then current regulation precision is improved, but circuit die size and cost increase
Solution Approach 1:
The patent extracts the current sensing function from external sense elements and relocates it to the switching node voltage signal itself. By monitoring the voltage at the switching node during MOSFET on-states, the system derives current information without requiring separate sense resistors or current transformers, thereby eliminating the area overhead of external sensing components while maintaining regulation precision
Solution Approach 2:
The switching node voltage signal serves multiple functions: it drives the power MOSFETs during normal operation and simultaneously provides current sensing information for regulation. This multi-functionality eliminates the need for dedicated sense elements, reducing circuit die size while achieving accurate average output current regulation through the existing voltage signal
2Measurement precision
If a sense element is used for accurate average output current regulation, then current regulation precision is improved, but cost increases
Solution Approach 1:
The patent removes the requirement for external current sense elements (such as sense resistors or current transformers) by extracting current information from the switching node voltage signal. This elimination of additional components directly reduces component count, assembly complexity, and overall manufacturing cost while maintaining regulation precision
Solution Approach 2:
Instead of using physical sense elements to measure current, the system creates an electrical copy of the current information through the switching node voltage signal. During MOSFET on-states, the voltage signal replicates current information, which can then be processed by the control circuit to achieve regulation without requiring expensive external sensing components
3Measurement precision
If external current sensing circuitry is used, then current sensing accuracy is improved, but device complexity increases
Solution Approach 1:
The switching node voltage signal performs dual roles: it is both the drive signal for the power MOSFETs and the sensing signal for current measurement. This eliminates the need for separate sensing circuitry and reduces overall device complexity while maintaining the ability to accurately sense and regulate output current
Solution Approach 2:
The power conversion circuit's own switching node voltage signal serves the dual purpose of both driving the power devices and providing current sensing information. The circuit uses itself for sensing purposes, eliminating the need for external sense elements and reducing overall system complexity
Data Source
AI summary
In described examples of methods and control circuitry to control a power conversion system, a regulator circuit is coupled to provide switching control signals according to a regulation signal to operate a plurality of converter switches to generate a voltage signal at a switching node. A compensation sense circuit is coupled to provide a compensation pulse signal having a duty cycle that represents a percentage of time that a current flowing through the switching node is above a threshold value. A current compensation circuit adjusts the regulation signal according to the compensation pulse signal.