Electric Motor Control Circuit Galvanic Isolation via Optical Transmission
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Solution Overview
Problem
Existing electric motor control circuits face precision issues due to complex and costly galvanic isolation elements, which impair the transmission of analog signals and result in reduced signal-to-noise ratio and resolution in current measurement, particularly in high-voltage zones.
Innovation Solution
A control circuit with a bleeder resistor, differential amplifier, and an analog-to-digital converter in the high-voltage zone, along with a galvanic isolation element downstream of the converter, and a DC/DC voltage converter providing floating low voltage to power the analog-to-digital converter, allowing precise measurement and transmission of digital signals, thereby reducing the need for complex isolation elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If galvanic isolation elements are used to separate high-voltage and low-voltage zones, then electrical safety is improved, but signal transmission precision deteriorates due to complexity and noise
Solution Approach 1:
The patent replaces the traditional magnetic galvanic isolation elements with an optical isolation system. The measurement signal from the high-voltage zone is converted to optical signals via LED modulators, transmitted through optical fibers across the galvanic barrier, and converted back to electrical signals in the low-voltage zone. This optical substitution eliminates the noise and complexity issues of magnetic isolation while maintaining electrical safety.
Solution Approach 2:
The patent introduces optical fibers as an intermediary medium between the high-voltage and low-voltage zones. The optical fiber serves as a galvanically isolated transmission channel that carries measurement signals without being affected by electrical noise or ground potential differences, thus preserving signal precision while ensuring electrical safety.
2Reliability
If complex galvanic isolation devices are used, then electrical safety is improved, but device complexity increases
Solution Approach 1:
The patent replaces complex magnetic isolation devices with a simpler optical isolation system consisting of LED modulators, optical fibers, and photodetectors. This substitution reduces device complexity while maintaining galvanic isolation and electrical safety, as optical components are inherently isolated from electrical interference.
3Reliability
If magnetic sensors are used for current measurement, then galvanic isolation is achieved, but measurement precision deteriorates due to sensitivity to ambient magnetic fields
Solution Approach 1:
The patent replaces magnetic sensors with an optical measurement and transmission system. Current measurement is performed in the high-voltage zone using resistive sensing, and the resulting electrical signal is converted to optical signals for transmission. This eliminates the problem of magnetic sensor sensitivity to ambient magnetic fields while maintaining galvanic isolation through the optical interface.
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
This configuration enables precise regulation of the electric motor current with reduced manufacturing costs, achieving high precision in current measurement and control without the need for expensive components, by using a digital signal transmission through optocouplers and high-resolution analog-to-digital converters.
Implementation Method 1
means for measuring the supply current providing a first analog signal whose value corresponds to the target current and an electronic control unit located in a low voltage zone, wherein the control circuit comprises an analog-to-digital converter to convert the first analog signal or another analog signal functioning as the first analog signal into an equivalent digital signal provided to the electronic control unit
Implementation Method 2
an analog-to-digital converter to convert the analog signal or another analog signal functioning as the analog signal into an equivalent digital signal which is provided to the electronic control unit
Implementation Method 3
DC/DC voltage converter providing floating low voltage to power the analog-to-digital converter
Data Source
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AI summary
The control circuit of an electric motor, which has at least one phase (2) supplied with high voltage and has a defined high-voltage zone (zone HV), is provided with a controller for the supply current of the phase with a nominal-value current, and has means for measurement (22, 24) of the supply current, which means produces a first analog signal (lM), whose value corresponds to the measured current, wherein an electronic control unit (6A) is arranged in a low-voltage zone (zone LV), and having an analog/digital converter (36) for conversion of the first analog signal or of some other analog signal, which acts as the first analog signal, to an equivalent digital signal (??*), which is supplied to the electronic control unit. The control circuit is characterized in that the means for measurement is formed by an output resistor (22), which is arranged in series with the phase, and by a differential amplifier (24), the two inputs of which are respectively connected to two contacts of the output resistor; in that the analog/digital converter (36) is arranged in the high-voltage zone, a conductive disconnecting element (38) is arranged between the analog/digital converter and the electronic control unit, and in that the control circuit has, inter alia, a voltage converter (40) which produces a floating low voltage (LVFL) in the high-voltage zone, which floating low voltage (LVFL) supplies the analog/digital converter.