Zero-Crossing AC Voltage Detection With Pulsed Optocoupler Drive
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Solution Overview
Problem
Existing devices for detecting AC voltage are inefficient in terms of energy usage and often detect direct current in addition to alternating current, which is not desirable in all applications.
Innovation Solution
A device and procedure that utilize a zero-through detector to supply the coupler's operating current, allowing the switching element to be temporarily activated only during zero crossings of the AC voltage, thereby reducing energy loss and selectively identifying alternating voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the switching element is continuously controlled to detect alternating voltage, then the detection reliability is improved, but the energy consumption increases significantly
Solution Approach 1:
The patent applies periodic action by controlling the switching element to operate only during specific intervals (when the alternating voltage is present and above a threshold) rather than continuously. The control unit activates the switching element periodically in synchronization with the alternating voltage cycles, thereby reducing energy consumption while maintaining reliable detection of voltage presence.
2Device complexity
If a simple series circuit with rectifier diode and series resistor is used to power the optocoupler, then the device complexity is reduced, but the power loss increases to tens or hundreds of milliwatts
Solution Approach 1:
The patent applies dynamics by replacing the static series resistor with a dynamic switching element controlled by the control unit. The switching element dynamically adjusts its state based on the alternating voltage conditions, enabling the system to minimize power loss by activating the optocoupler only when necessary, rather than continuously dissipating power through a fixed resistor.
Solution Approach 2:
The patent applies parameter changes by modifying the operating state of the optocoupler from continuous operation to intermittent operation. The control unit changes the activation parameters of the switching element based on detected voltage conditions, thereby optimizing the balance between detection reliability and energy efficiency.
3Ease of manufacture
If the series resistor is used to limit current to the optocoupler LED, then the circuit design is simplified, but energy efficiency deteriorates due to continuous power dissipation
Solution Approach 1:
The patent applies the extraction principle by removing the continuously active series resistor from the current path and replacing it with a switching element that is activated only when needed. This extraction of the always-on power-dissipating component eliminates unnecessary energy loss while preserving the simple circuit topology through the use of a controllable switch.
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 achieves significant energy savings, reducing energy loss by 90% compared to continuous control of the switching element, while ensuring that only alternating current is detected.
Implementation Method 1
an optocoupler with a light-emitting diode (LED) as the control element for galvanic isolation is used. The LED of the optocoupler is supplied with operating current by the applied alternating current, causing the switching element of the optocoupler, usually a phototransistor, to become conductive.
Implementation Method 2
The LED of the optocoupler is supplied with operating current by the applied alternating current, causing the switching element of the optocoupler, usually a phototransistor, to become conductive.
Data Source
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AI summary
The invention relates to a device (1) for detecting alternating voltage, comprising input terminals (2) for the application of an alternating voltage (Vin) to be detected and output terminals (3), at which application of the alternating voltage (Vin) is indicated, wherein the input terminals (2) and the output terminals (3) are galvanically separated from each other by means of a coupler (13), and wherein a control element (131) of the coupler (13) is supplied with operating current from the applied alternating voltage, and a switching element (132) of the coupler (13) is connected to the output terminals (3). The device (1) is characterized by a zero-crossing detector (12) for the alternating voltage (Vin) to be detected, which zero-crossing detector supplies the control element (131) of the coupler (13) with the operating current in pulses. The invention also relates to a method for detecting alternating voltage.