DC-DC Converter Average Current Limit via RC Filtering

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Solution Overview

Problem

Conventional DC-DC converters rely on peak current detection for current-limit protection, which can lead to inaccurate triggering due to noise-induced current ripples, failing to accurately set a fixed average current limit.

Innovation Solution

A current-limit system that employs a current sensing device and a current-to-voltage converting module to detect and convert the average current into a clamp voltage, allowing the DC-DC converter to be controlled based on the average current, thereby preventing inaccurate triggering and allowing external adjustment of the current limit.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If peak current detection is used for current-limit protection, then the protection response is fast and simple, but the current-limit triggering becomes inaccurate due to noise-induced current ripples

Engineering Contradiction:

Improvecurrent-limit protection accuracyVSAvoidaverage current detection accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent introduces an intermediary mechanism (capacitor and resistor network) between the current sensing device and the control circuit to filter noise and extract average current information from the ripple-containing current signal, thereby resolving the contradiction between fast protection response and accurate average current detection

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces the conventional peak current detection mechanism with an average current detection mechanism using passive RC filtering, substituting a noisy direct detection approach with a filtered averaging approach that eliminates noise-induced false triggering

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Productivity

If peak current value is used as current-limit threshold, then the current-limit mode can be triggered quickly, but the average current limit cannot be fixed accurately due to varying current amplitudes

Engineering Contradiction:

Improvecurrent-limit response speedVSAvoidaverage current limit precision

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The RC filtering circuit acts as an intermediary that transforms the peak current signal into an average current representation, allowing the system to maintain fast response while achieving accurate average current limiting through the filtered voltage signal

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If noise filtering is applied to reduce current ripples, then false triggering is reduced, but the system complexity increases

Engineering Contradiction:

Improvecurrent-limit triggering accuracyVSAvoidcurrent detection system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent uses simple passive RC filtering components as intermediaries to achieve noise reduction without introducing complex active filtering circuits or digital signal processing, thereby maintaining system reliability while minimizing complexity increase

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent employs inexpensive passive RC filtering components rather than complex active filters or digital processors, achieving effective noise filtering with minimal cost and complexity overhead

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Data Source

PatentUS8901907B2Current-limit system and method

Publication Date: 2014.12.02 ANPEC ELECTRONICS CORPORATION

AI summary

A current-limit system for limiting an average current of an output signal of a DC-DC converter includes a current sensing device, coupled to the DC-DC converter, for detecting the average current of the output signal of the DC-DC converter; and a current-to-voltage converting module, coupled to the current sensing device, for converting the average current into a clamp voltage, in order to control the DC-DC converter according to the clamp voltage.