Rate-of-Voltage Change Detection Circuit for EV Motor Control

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Solution Overview

Problem

Existing power transducers in EVs and HVs face instability due to fluctuations in AC voltage generated by switching elements, making it difficult to accurately measure the rate of change over time, which is crucial for motor operation, and current methods are not capable of real-time detection.

Innovation Solution

A rate-of-voltage change detection circuit comprising a first capacitor, a resistor, and a rectifier circuit connected in series, with a second capacitor to accumulate charge and output a DC signal indicating the rate of change over time, allowing for continuous detection and discharge of accumulated charge to maintain voltage levels.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If waveform analysis is used to measure the rate of change over time, then measurement accuracy is improved, but detection speed deteriorates due to time-consuming analysis

Engineering Contradiction:

Improverate of change measurement accuracyVSAvoiddetection time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The circuit performs preliminary transformation of the voltage signal into its rate of change form through capacitor differentiation and rectification, so that the output directly represents the instantaneous rate of change without requiring subsequent time-consuming waveform analysis

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces the mechanical/manual waveform analysis process with an electronic circuit system that automatically computes and outputs the rate of change in real-time, eliminating the need for oscilloscope-based measurement and manual calculation

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Productivity

If real-time detection is implemented, then productivity is improved, but measurement precision deteriorates due to voltage level fluctuations

Engineering Contradiction:

Improvereal-time detection capabilityVSAvoidrate of change measurement accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The circuit transforms the measurement parameter from voltage level to rate of change of voltage, using capacitor differentiation to convert the fluctuating voltage signal into a proportional rate-of-change signal that can be accurately measured in real-time despite voltage variations

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The capacitor and rectifier circuit act as intermediaries that transform the difficult-to-measure fluctuating voltage signal into a stable, proportional DC voltage signal that accurately represents the rate of change, enabling precise real-time measurement

Inventive Principle:

Principle #24Intermediary (Mediator)

3Measurement precision

If complex waveform analysis is used, then measurement precision is improved, but device complexity increases

Engineering Contradiction:

Improverate of change measurement accuracyVSAvoidcircuit complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent extracts only the essential function needed for rate-of-change measurement from complex waveform analysis, using a simple capacitor-resistor-rectifier circuit configuration that directly outputs the rate of change without requiring full waveform processing

Inventive Principle:

Principle #2Taking out (Extraction)

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

Enables accurate and real-time detection of the rate of change over time of AC voltage, stabilizing motor operation and simplifying the detection process without the need for complex waveform analysis, while maintaining a cost-effective and practical solution.

Implementation Method 1

a first capacitor and a first resistor connected in series between a measurement target node and a reference voltage node

Methodology Applied

Scientific EffectCapacitive differentiation: Capacitance

Implementation Method 2

a first rectifier circuit connected between an output node and a connection node of the first capacitor and the first resistor

Methodology Applied

Scientific EffectRectification: Diode

Implementation Method 3

a second capacitor connected between the output node and the reference voltage node

Methodology Applied

Scientific EffectCapacitive charge accumulation: Capacitance

Data Source

PatentUS11489434B2Power transducer including a rate of voltage change detection circuit

Publication Date: 2022.11.01 KK TOSHIBA

AI summary

An electronic circuit includes an output node configured to output a DC signal indicating a rate of change over time of voltage at a measurement target node. The rate-of-voltage change detection circuit includes a first capacitor and a first resistor connected in series between the measurement target node and a reference voltage node, a first rectifier circuit connected between the output node and a connection node of the first capacitor and the first resistor, and a second capacitor connected between the output node and the reference voltage node.