Motor Controller Offset Voltage Addition Circuit

Solution Overview

Problem

Conventional motor controllers experience excessive current in the inverter circuit when reversing the rotation direction of a motor, leading to potential thermal breakdown of MOSFETs due to increased duty ratio of PWM signals and added offset voltage.

Innovation Solution

A motor controller design that includes an inverter circuit, control circuit, rotation speed detection, amplifier circuit, comparison circuits, and an offset voltage addition circuit, where the offset voltage is added to the differential voltage signal instead of the target voltage signal, and the PWM signals' duty ratio is managed to prevent excessive current.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Force

If offset voltage is added to the target voltage signal during motor reversal, then the motor can generate sufficient torque to overcome inertia and start rotating in reverse direction, but the PWM duty ratio becomes excessively high causing excessive current in the inverter circuit

Engineering Contradiction:

Improvemotor torqueVSAvoidexcessive current

Core Design Contradiction:

ForceVSObject-generated harmful factors

Solution Approach 1:

The patent segments the voltage signal processing into two separate stages: the offset voltage is added to the differential voltage signal (after amplification) rather than being added to the target voltage signal (before amplification). This segmentation allows precise control over when and how the offset is applied, preventing excessive PWM duty ratio while ensuring sufficient motor torque during reversal.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the parameter of voltage signal processing by modifying the point of offset voltage addition from the target voltage signal to the differential voltage signal. This parameter change in the signal processing chain ensures that the offset voltage is applied after amplification, maintaining appropriate PWM duty ratio levels while still providing the necessary torque for motor reversal.

Inventive Principle:

Principle #35Parameter changes

2Force

If PWM duty ratio is increased to provide sufficient torque during motor reversal, then the motor can overcome inertia and change rotation direction, but thermal breakdown of MOSFETs occurs due to excessive current

Engineering Contradiction:

Improvemotor torqueVSAvoidMOSFET thermal stability

Core Design Contradiction:

ForceVSReliability

Solution Approach 1:

The patent segments the voltage signal processing into two separate stages: the offset voltage is added to the differential voltage signal (after amplification) rather than being added to the target voltage signal (before amplification). This segmentation allows precise control over when and how the offset is applied, preventing excessive PWM duty ratio while ensuring sufficient motor torque during reversal.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the parameter of voltage signal processing by modifying the point of offset voltage addition from the target voltage signal to the differential voltage signal. This parameter change in the signal processing chain ensures that the offset voltage is applied after amplification, maintaining appropriate PWM duty ratio levels while still providing the necessary torque for motor reversal.

Inventive Principle:

Principle #35Parameter changes

3Object-generated harmful factors

If offset voltage is added to the differential voltage signal instead of the target voltage signal, then excessive current is prevented and MOSFET thermal breakdown is avoided, but the motor may not generate sufficient torque to overcome inertia during reversal

Engineering Contradiction:

Improveexcessive currentVSAvoidmotor torque

Core Design Contradiction:

Object-generated harmful factorsVSForce

Solution Approach 1:

The patent changes the parameter of voltage signal processing by modifying the point of offset voltage addition from the target voltage signal to the differential voltage signal. This parameter change in the signal processing chain ensures that the offset voltage is applied after amplification, maintaining appropriate PWM duty ratio levels while still providing the necessary torque for motor reversal.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS7538515B2Motor controller

Publication Date: 2009.05.26 DENSO CORP

AI summary

A motor controller includes an inverter circuit, a speed detector, an amplifier, a voltage detector, and an offset voltage addition circuit. The inverter circuit drives a motor based on a PWM signal. The speed detector generates an actual speed signal corresponding to an actual speed of the motor. The amplifier outputs a differential voltage by amplifying a difference between the actual speed signal and a target speed signal. The voltage detector outputs a switch signal for switching rotation direction of the motor. The switch signal has a first level, when the differential voltage is equal to or greater than a predetermined value. The switch signal has a second level, when the differential voltage is less than the predetermined value. The offset voltage addition circuit adds an offset voltage to the differential voltage according to the signal level of the switch signal.