Zero-Crossing Circuit Without Photocouplers for Accurate AC Detection
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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 applications like washing machines where high-voltage components are prone to corrosion.
Innovation Solution
A zero-crossing detection circuit that eliminates the use of photocouplers by incorporating a peak detection unit to generate a peak detection signal and a zero-crossing detection unit to estimate the zero-crossing point from this signal, utilizing a semiconductor integrated circuit device with diodes and capacitors to reduce component count and improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a photocoupler is used in the zero-crossing detection circuit, then the circuit can detect zero-crossing points, but the power consumption is large
Solution Approach 1:
The patent extracts and removes the photocoupler component from the zero-crossing detection circuit. By eliminating the photocoupler, the circuit achieves lower power consumption while maintaining zero-crossing detection functionality through alternative circuitry involving operational amplifiers and voltage dividers.
Solution Approach 2:
The patent replaces the optical coupling mechanism (photocoupler) with an electrical circuit approach using operational amplifiers, voltage dividers, and comparison circuits. This substitution eliminates the need for optical components and reduces power consumption while achieving the same detection function.
2Measurement precision
If a photocoupler and multiple discrete components are used in the zero-crossing detection circuit, then the circuit can detect zero-crossing points, but the number of components is large
Solution Approach 1:
The patent merges multiple discrete components into an integrated circuit design. The zero-crossing detection function is implemented using a combination of operational amplifiers, voltage dividers, and comparison circuits that are interconnected to perform detection with fewer external components, eliminating the need for separate photocoupler, transistor, and multiple resistor components.
Solution Approach 2:
The operational amplifiers and comparison circuits in the patent serve multiple functions: they perform voltage division, signal amplification, zero-crossing detection, and threshold comparison all within a unified circuit architecture, reducing the need for separate dedicated components for each function.
3Measurement precision
If a photocoupler is used in the zero-crossing detection circuit, then the circuit can detect zero-crossing points, but the detection accuracy is low due to temperature characteristics
Solution Approach 1:
The patent replaces the temperature-sensitive photocoupler with an operational amplifier-based circuit that uses voltage dividers and comparison circuits. This electrical approach is less sensitive to temperature variations, providing more stable and accurate zero-crossing detection across different temperature conditions.
Solution Approach 2:
The patent changes the detection mechanism from optical (photocoupler) to electrical (operational amplifier voltage comparison). This parameter change in the detection method eliminates the temperature-dependent characteristics of the photocoupler and provides more stable detection accuracy across temperature ranges.
4Measurement precision
If high-voltage components are used in the zero-crossing detection circuit, then the circuit can detect zero-crossing points, but the reliability is low due to corrosion
Solution Approach 1:
The patent removes high-voltage components from the detection circuit by using operational amplifiers and voltage dividers that can operate at lower voltages. The high-voltage AC signal is divided down to safe levels before being processed by the detection circuitry, eliminating the need for corrosion-prone high-voltage resistors and components.
Solution Approach 2:
The patent introduces voltage dividers as intermediary components that step down the high-voltage AC signal to lower voltage levels before the signal reaches the zero-crossing detection circuitry. This intermediary voltage reduction protects the detection components from high-voltage corrosion while maintaining detection accuracy.
Data Source
AI summary
A semiconductor integrated circuit device includes: a zero-crossing detection unit configured 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 comparison signal; a logic unit configured to count a period of the comparison signal and estimate a zero-cross of the AC signal using the count value, so as to generate a zero-crossing detection signal; and a monitoring unit configured to adjust the first monitoring target signal and the second monitoring target signal to be suitable for input to the zero-crossing detection unit, where a first chip, in which the monitoring unit is integrated, is cut out in a rectangular shape having a substantially equal ratio between a short side and a long side in a plan view.