Zero-Crossing Detection Circuit Eliminates Photocoupler
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Solution Overview
Problem
Conventional zero-crossing detection circuits face issues with high power consumption, numerous discrete components, low detection accuracy due to temperature characteristics, and reliability concerns, particularly in high-voltage applications like washing machines where resistor corrosion occurs.
Innovation Solution
A zero-crossing detection circuit that eliminates the use of photocouplers by incorporating a peak detection unit, a zero-crossing detection unit, and a logic unit to estimate zero crossings from AC signals, utilizing a semiconductor integrated circuit device and diodes to reduce component count and improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a photocoupler is used in the zero-crossing detection circuit, then the circuit can detect zero crossings, but the power consumption increases
Solution Approach 1:
The patent removes the photocoupler from the circuit and extracts only the essential zero-crossing detection function, implementing it through a simplified voltage divider circuit with resistors and a comparator. This eliminates the power-consuming photocoupler while maintaining the core detection capability.
Solution Approach 2:
The patent replaces the optical-mechanical photocoupler system with an electrical circuit system using resistors, capacitors, and comparators. This substitution eliminates the need for light-based detection and reduces power consumption significantly.
2Reliability
If a photocoupler-based zero-crossing detection circuit is used, then the circuit functions, but the number of discrete components increases
Solution Approach 1:
The patent merges multiple discrete components into a single integrated circuit chip. The zero-crossing detection function is integrated along with other control functions, reducing the component count from eleven discrete parts to a single integrated circuit with only a few external passive components.
Solution Approach 2:
The integrated circuit performs multiple functions including zero-crossing detection, voltage monitoring, and control signal generation. This multi-functional approach eliminates the need for separate dedicated circuits for each function, thereby reducing overall component count.
3Reliability
If a photocoupler is used for zero-crossing detection, then the circuit can operate, but detection accuracy decreases due to temperature characteristics
Solution Approach 1:
The patent replaces the temperature-sensitive photocoupler with an electrical comparator-based detection system. The comparator uses voltage thresholds that are less sensitive to temperature variations, thereby improving detection accuracy and stability across different operating conditions.
4Ease of manufacture
If high-voltage components like resistors are used in the zero-crossing detection circuit, then the circuit can be built, but reliability decreases due to corrosion
Solution Approach 1:
The patent integrates high-voltage tolerant components directly into the integrated circuit chip, eliminating the need for discrete high-voltage resistors that are prone to corrosion. The integrated circuit is designed to handle high voltages internally, improving reliability while maintaining ease of manufacture.
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 reduces power consumption, minimizes the number of components, and enhances detection accuracy, making it suitable for high-voltage applications while avoiding photocoupler-related issues.
Implementation Method 1
a peak detection unit arranged to detect a peak of a monitoring target signal input through a diode from an AC signal input terminal
Data Source
AI summary
A zero-crossing detection circuit includes a zero-crossing detection unit arranged to compare a first monitoring target signal and a second monitoring target signal respectively input through diodes from a first node and a second node between which an AC signal is applied, so as to generate a first comparison signal, and a logic unit arranged to estimate a zero cross of the AC signal from the first comparison signal so as to generate a zero-crossing detection signal. The zero-crossing detection circuit preferably includes a monitoring unit arranged to adjust the first monitoring target signal and the second monitoring target signal to be suitable for input to the zero-crossing detection unit. The logic unit preferably counts a period of the first comparison signal and estimates a zero cross of the AC signal using a count value thereof.