Inductor Current Detection Using Emulated Sampling in Switching Converters

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Solution Overview

Problem

Conventional current detection circuits in switched-mode power supply converters suffer from ringing and delay issues due to parasitic inductances and capacitances, leading to inaccurate and delayed detection of inductor current, especially during short conduction times of power switches.

Innovation Solution

A current detection circuit comprising a current sampling module, an emulated current generation module, an error determination module, and an error adjustment module, which adjusts the rate of variation of the emulated current to match the actual inductor current, eliminating delays and ensuring accurate detection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a blanking time is added to avoid ringing during power switch turn-on and turn-off, then the ringing is suppressed, but a delay occurs between the sampled current and the actual inductor current

Engineering Contradiction:

ImproveringingVSAvoiddetection delay

Core Design Contradiction:

Object-affected harmful factorsVSLoss of time

Solution Approach 1:

The patent applies preliminary action by performing current sampling during the blanking time period before the actual current measurement is needed. The sampled current is stored and then used as the detection result, eliminating the delay that would otherwise occur when waiting for the blanking time to end. This allows the system to prepare the current measurement in advance during the ringing suppression period.

Inventive Principle:

Principle #10Preliminary action

2Productivity

If the conduction time of the power switch is very short (shorter than blanking time), then the switching converter operates with high frequency, but the sampled current has large error or is lost completely

Engineering Contradiction:

Improveswitching frequencyVSAvoidcurrent sampling accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent performs current sampling during the blanking time period in advance, storing the sampled value for later use. This ensures that even when the power switch conduction time is shorter than the blanking time, the current measurement is captured during the available blanking period rather than being lost or requiring error-prone sampling during the actual conduction period.

Inventive Principle:

Principle #10Preliminary action

3Loss of time

If conventional current detection is used during power switch conduction, then real-time current information is obtained, but ringing causes measurement errors

Engineering Contradiction:

Improvedetection response timeVSAvoidcurrent measurement accuracy

Core Design Contradiction:

Loss of timeVSMeasurement precision

Solution Approach 1:

The patent performs current sampling during the blanking time period before the power switch conduction begins. By sampling in advance during this quiet period free from ringing, the system obtains accurate current measurements without the measurement errors that would result from sampling during the ringing-prone conduction period.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses the blanking time period as an intermediary window for current sampling. This intermediate period serves as a buffer zone where current measurement can occur without the interference of ringing, decoupling the measurement process from the problematic switching transitions while still providing timely current information for control purposes.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS12525862B2Current detection circuit and controller for switching converter circuit

Publication Date: 2026.01.13 SHANGHAI BRIGHT POWER SEMICONDUCTOR CO LTD

AI summary

A current detection circuit and a controller for a switching converter circuit are disclosed. An emulated current generation module emulates a current flowing through an inductor, and a current sampling module actually samples the inductor current. Moreover, an error determination module determines an error between the actually sampled and emulated currents and adjusts, based on the error, a rate of variation of the emulated current.