DC Brushless Motor Controller Phase Lag Compensation

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Solution Overview

Problem

Existing DC brushless motor control technologies using terminal voltage comparison estimation methods suffer from phase lagging issues, leading to commutation time delays and surge currents, affecting electromagnetic compatibility and motor efficiency.

Innovation Solution

A controller for DC brushless motors that includes a commutation circuit with three voltage dividers and comparators, where bias resistors and a control circuit detect counter EMF signals to supply offset voltages, enabling early commutation by compensating for phase lagging through timely adjustments.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If terminal voltage comparison estimation method is used to obtain commutation signal, then the control can be widely applied to various types of motors with different driving parameters, but the commutation time delay generates surge current affecting electromagnetic compatibility and motor output efficiency

Engineering Contradiction:

Improveapplicability to various motorsVSAvoidcommutation timing accuracy

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent applies preliminary action by detecting the counter EMF signal in advance and providing compensation offset voltage before the commutation point is reached. The control circuit detects the counter EMF signal of each phase coil and determines the timing of the commutation point, then provides compensation offset voltage to the node of the voltage divider in advance to compensate for phase lagging, thereby achieving accurate commutation timing without surge current.

Inventive Principle:

Principle #10Preliminary action

2Measurement precision

If counter EMF zero-crossing estimation method is used, then the commutation point can be accurately detected, but it is hard to control when driving motors with various parameters

Engineering Contradiction:

Improvecommutation point detection accuracyVSAvoidcontrol flexibility for various motors

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent applies parameter changes by dynamically adjusting the compensation offset voltage based on detected counter EMF signals. The control circuit detects the counter EMF signal and determines when to provide compensation offset voltage to the voltage divider node, thereby adapting the commutation timing to different motor parameters while maintaining accurate commutation point detection.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If filtering is applied to counter EMF signal, then noise can be reduced, but the commutation time delay increases generating surge current

Engineering Contradiction:

Improvesignal qualityVSAvoidcommutation timing

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent applies preliminary action by providing compensation offset voltage before the commutation point is reached. The control circuit detects the counter EMF signal and determines the timing of the commutation point, then provides compensation offset voltage to the node of the voltage divider in advance. This preliminary compensation action eliminates the need for excessive filtering while maintaining accurate commutation timing.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent applies preliminary anti-action by using the compensation offset voltage to counteract the phase lagging effect before it occurs. By detecting the counter EMF signal and providing compensation voltage in advance, the system pre-compensates for the timing delay that would otherwise be caused by filtering, thereby preventing surge current generation.

Inventive Principle:

Principle #9Preliminary anti-action

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 effectively compensates for phase lagging and delaying issues, achieving early commutation control and improving motor performance by reducing surge currents and enhancing electromagnetic compatibility.

Implementation Method 1

the control circuit is configured to detect a counter EMF signal of each of the three-phase coils and to supply an electric energy based on a detecting result

Methodology Applied

Scientific EffectCounter EMF (Back Electromotive Force): Electromagnetic Induction

Data Source

PatentUS10622926B1Controller of DC brushless motor and control method thereof

Publication Date: 2020.04.14 JYEN HERR ENTERPRISE CO LTD

AI summary

A controller of a DC brushless motor and a control method thereof are disclosed. The controller is connected to a commutation circuit including three voltage dividers and three comparators. Each voltage divider includes a first resistor and a second resistor connected in series. Each first resistor is connected to a terminal voltage of three-phase coils of the DC brushless motor. Each comparator includes a positive input end connected to a node connected to the first resistor and the second resistor of the corresponding voltage divider and a negative input end connected to the node of the adjacent voltage divider. The controller includes a control circuit and three bias resistors respectively connected to a voltage source and the node of the corresponding voltage divider. The control circuit detects a counter EMF signal of each phase coil and controls the voltage source to supply an offset voltage to the corresponding node.