Buck-Boost Converter Current Detection with One Shunt Resistor

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Solution Overview

Problem

Existing control modules for buck-boost switching converters require two shunt resistors for overcurrent detection and current cancellation, occupying space and dissipating power, and necessitate additional pins in the package.

Innovation Solution

A control module that utilizes a low-pass filtering circuit with filtering resistors and a capacitor to generate a filtered voltage for overcurrent detection, eliminating the need for one shunt resistor and reducing package size and power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If two shunt resistors are used for overcurrent detection and current cancellation, then reliable current detection is achieved, but package size and power consumption increase

Engineering Contradiction:

Improvecurrent detection reliabilityVSAvoidpackage size

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent combines the functions of overcurrent detection and current cancellation into a single shunt resistor circuit. The control module processes both detection tasks using one resistor rather than two separate resistors, thereby reducing package size while maintaining detection reliability through integrated signal processing

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The single shunt resistor serves multiple functions: it enables both overcurrent detection and current cancellation detection. The control module processes the voltage signal from this single resistor to achieve both detection purposes, making the resistor a multi-functional component that reduces overall circuit complexity and package requirements

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Measurement precision

If two shunt resistors are used for overcurrent detection and current cancellation, then accurate current monitoring is achieved, but power consumption increases

Engineering Contradiction:

Improvecurrent monitoring accuracyVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by stationary object

Solution Approach 1:

The patent merges the current monitoring functions into a single shunt resistor circuit, reducing the total power consumption associated with multiple resistors while maintaining measurement precision through sophisticated signal processing in the control module that extracts multiple detection signals from the single resistor's voltage output

Inventive Principle:

Principle #5Merging (Combining)

3Reliability

If two shunt resistors are used, then comprehensive current detection is achieved, but the number of package pins increases

Engineering Contradiction:

Improvecurrent detection capabilityVSAvoidpackage pin count

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent combines multiple detection functions into a single shunt resistor connection, reducing the number of required package pins. The control module internally processes the single resistor's signal to provide both overcurrent and current cancellation detection capabilities, thereby simplifying the package interface while maintaining comprehensive detection

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The single shunt resistor connection serves as a universal interface for multiple detection purposes. The control module derives both overcurrent and current cancellation signals from this single connection point, reducing the number of external pins required while maintaining comprehensive current detection capability

Inventive Principle:

Principle #6Universality (Multi-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

The solution allows for effective overcurrent detection and reduced power consumption by using a filtered voltage to determine when the current has canceled out, enabling rapid control actions without the need for two shunt resistors, thus minimizing package size and pin count.

Implementation Method 1

A control module that utilizes a low-pass filtering circuit with filtering resistors and a capacitor to generate a filtered voltage for overcurrent detection

Methodology Applied

Scientific EffectLow-pass filtering: Filter (electronic)

Data Source

PatentEP4333281A1Control module for a buck-boost switching converter with overcurrent and null-current detection and method for controlling a buck-boost switching converter

Publication Date: 2024.03.06 STMICROELECTRONICS SRL

Figure 1
Figure 2A~2B
Figure 3A~3B

AI summary

Control module for a buck-boost switching converter (101), which includes an inductor (12) and a shunt resistor (14) and is coupled to a load (13) which draws a load current (ILOAD). The control module includes: a control stage (18,19) which performs charge (T'ON) and discharge (T'OFF) cycles of the inductor (12), during which the inductor (12) is traversed by an inductor current (IL), the shunt resistor (14) being subject to a respective voltage (vdcm) and being traversed by a resistor current (idcm); a first comparator stage (17A), which generates a first signal (sV1), which is indicative of the direction of the resistor current (idcm) and is provided to the control stage; a filtering circuit (102,104,106) of low-pass type, which generates a filtered electrical quantity (Vfilt) as a function of the voltage (vdcm) on the shunt resistor (14); a second comparator stage (52,56,117), which generates a second signal (sVx) indicative of a comparison between the filtered electrical quantity (Vfilt) and a reference electrical quantity (Vth); and a detection stage (52,56) which detects the occurrence of an overcurrent in the load (13), on the basis of the second signal (sVx).