Contactor Detection Circuit Using Y-Capacitor Isolation
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Solution Overview
Problem
Existing contactor detection methods for high-voltage systems require costly isolation of power supplies and operational amplifiers, or rely on microcontroller units (MCUs) for high and low voltage isolation, leading to increased costs and complexity.
Innovation Solution
A contactor detection circuit using a comparator, reference voltage generation, and a sampling circuit with Y capacitors for electrical isolation, eliminating the need for isolated power supplies and MCUs, and utilizing a waveform generator to differentiate between open and closed states based on periodic voltage signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-voltage source sampling is used to detect contactor status, then voltage division sampling can determine contactor state, but isolated power supply and operational amplifier are required achieving high and low voltage isolation which is costly
Solution Approach 1:
The patent introduces a Y capacitor as an intermediary element to achieve high-voltage isolation. The Y capacitor connects between the high-voltage side (contactor contacts) and the low-voltage detection circuit, providing galvanic isolation without requiring isolated power supplies or operational amplifiers. This intermediary component enables safe voltage sampling while maintaining cost-effectiveness.
Solution Approach 2:
The patent creates a low-voltage copy of the high-voltage signal through the Y capacitor and voltage division network. Instead of directly measuring high-voltage signals with expensive isolated equipment, the circuit generates a scaled-down replica of the contactor voltage state that can be safely measured by standard non-isolated components, achieving the same detection purpose with lower cost components.
2Measurement precision
If high-voltage source is used as sampling input, then contactor status can be determined through voltage division, but real-time knowledge of high-voltage voltage is required which is inconvenient for practical applications
Solution Approach 1:
The detection circuit uses the contactor's own voltage signal as the input source. The Y capacitor samples the voltage present across the contactor contacts directly, and the voltage division network automatically scales this signal to a measurable range. The system serves itself by using the object being measured as the signal source, eliminating the need for external high-voltage references or additional measurement equipment.
Solution Approach 2:
The patent transforms the high-voltage parameter into a low-voltage parameter through the Y capacitor and voltage division network. By changing the voltage level parameter from high-voltage to low-voltage through passive component division, the circuit makes the measurement convenient for practical applications while preserving the contactor status information for accurate detection.
3Reliability
If PWM waves generated by MCU are used to achieve high and low voltage isolation through Y capacitor, then isolation is achieved, but MCU and software development are required resulting in higher costs
Solution Approach 1:
The patent extracts and removes the MCU and software components from the isolation solution. Instead of using active MCU-generated PWM waves and associated software development, the invention achieves voltage isolation purely through passive Y capacitor and voltage division circuitry. This extraction of active components simplifies the system and eliminates software development requirements while maintaining isolation functionality.
Solution Approach 2:
The patent replaces expensive, complex MCU-based isolation solutions with inexpensive passive components (Y capacitors and resistors). These simple passive components provide the necessary isolation function without requiring costly microcontrollers, reducing both component cost and system complexity while achieving the same safety and isolation objectives.
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
Achieves reliable high and low voltage isolation without the need for isolated power supplies or MCUs, reducing costs and simplifying the detection process.
Implementation Method 1
the capacitors C1 and C2 are Y capacitors used for electrically isolating the high-voltage circuit connected to the two static contacts of the contactor
Implementation Method 2
a comparator; a reference voltage generation circuit, whose output end is connected to the inverting input end of the comparator, for inputting a reference voltage V1 to the inverting input end of the comparator; a sampling circuit electrically connected to two static contacts of a contactor and its output end connected to the in-phase input end of the comparator, for inputting a sampling voltage V2 to the in-phase input end of the comparator
Data Source
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AI summary
The present invention discloses a contactor detection circuit. The contactor detection circuit comprises: a comparator; a reference voltage generation circuit, whose output end is connected to the inverting input end of the comparator, for inputting a reference voltage V1 to the inverting input end of the comparator; a sampling circuit electrically connected to two static contacts of a contactor and its output end connected to the in-phase input end of the comparator, for inputting a sampling voltage V2 to the in-phase input end of the comparator; and a waveform generator, whose output end is connected to the input end of the sampling circuit, is used to input a periodically changing voltage signal V3 to the sampling circuit. When the contactor is in an open state, the sampling voltage V2 output by the sampling circuit is a periodic waveform, causing the comparator to output a periodic square wave signal; when the contactor is in a closed state, the sampling voltage V2 output by the sampling circuit is higher than the reference voltage V1, causing the comparator to output a high level. The present invention does not require the use of isolated power supplies and isolated operational amplifiers, nor does it require the use of MCUs or the development of specialized software, greatly reducing costs.