Interface Circuit for ECM Speed Regulation Using Digital Optocouplers

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Solution Overview

Problem

Existing electrical appliance systems with electronically commutated motors (ECM) face challenges in cost-effective and reliable speed regulation due to the need for expensive and complex signal isolation methods using linear optocouplers and serial communication protocols, as the ECM controller and speed controller are not common-grounded.

Innovation Solution

An interface circuit integrating a low-cost micro control unit (MCU), an isolated power supply, and a signal isolating circuit (digital optocoupler) to convert analog voltage signals into pulse width modulation (PWM) or variable frequency signals, allowing for efficient and accurate speed regulation of ECMs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If signal isolation transmission using linear optocouplers and serial communication protocols is employed, then reliable signal transmission is achieved, but cost and system complexity increase

Engineering Contradiction:

Improvesignal transmission reliabilityVSAvoidsystem complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces expensive linear optocouplers with inexpensive digital optocouplers that provide sufficient isolation performance for digital PWM and frequency signals. The digital nature of the optocoupler allows direct transmission of control signals without requiring complex serial communication protocols, thereby reducing both cost and system complexity while maintaining reliable signal transmission across the galvanic isolation boundary

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent extracts the essential function of signal isolation from complex serial communication protocols and reduces it to simple digital signal transmission through optocouplers. By taking out only the necessary isolation capability and eliminating unnecessary protocol complexity, the system achieves reliable transmission with much simpler hardware and software implementation

Inventive Principle:

Principle #2Taking out (Extraction)

2Reliability

If signal isolation transmission using linear optocouplers and serial communication protocols is employed, then reliable signal transmission is achieved, but cost increases

Engineering Contradiction:

Improvesignal transmission reliabilityVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent substitutes costly linear optocoupler-based analog isolation with inexpensive digital optocouplers that directly transmit PWM and frequency signals. This replacement dramatically reduces component cost while maintaining the necessary galvanic isolation and signal transmission reliability for ECM speed control applications

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Ease of operation

If analog voltage signals are used for speed regulation, then simple control is achieved, but accurate signal transmission across isolated grounds is difficult

Engineering Contradiction:

Improvecontrol simplicityVSAvoidsignal transmission accuracy

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent replaces the mechanical/electrical analog voltage signal transmission system with a digital signal transmission system using optocouplers. The MCU converts analog voltage to digital PWM and frequency signals, which are then transmitted through optocouplers to the isolated ECM controller, maintaining control simplicity while ensuring accurate signal transmission across galvanically isolated grounds

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the signal parameter from analog voltage to digital PWM/frequency signals. This parameter transformation allows the signal to be transmitted reliably across isolated grounds through digital optocouplers, preserving both the simplicity of analog-like control and the accuracy of digital transmission

Inventive Principle:

Principle #35Parameter changes

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 provides a cost-effective, accurate, and reliable method for speed regulation of ECMs by using a low-cost MCU and digital optocoupler, reducing complexity and increasing the reliability of signal transmission while maintaining high accuracy.

Implementation Method 1

signal isolating circuit (digital optocoupler)

Methodology Applied

Scientific EffectOptical coupling: Photoelectric Effect

Data Source

PatentUS10135370B2Interface circuit and electrical appliance system comprising the same

Publication Date: 2018.11.20 ZHONGSHAN BROAD OCEAN

AI summary

An interface circuit, including: a micro control unit (MCU), an isolated power supply, and a signal isolating circuit. The MCU, the isolated power supply, and the signal isolating circuit are integrated on a circuit board. The output end of the isolated power supply supplies power for circuits. The input end of the isolated power supply is connected to an external input power supply. The A/D conversion input port of the MCU is connected to the analog voltage signals. The MCU is configured to convert the analog voltage signals into pulse width modulation (PWM) signals or variable frequency signals with certain duty cycles, and output the PWM signals or the variable frequency signals to the input end of the signal isolating circuit. The signal isolating circuit is configured to output the PWM signals or the variable frequency signals with certain duty cycles.