Timing Relay Control Circuit Prevents False Triggering
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Solution Overview
Problem
Existing timing relays face limitations in allowing weak on-state elements or external trigger apparatuses to be connected in parallel due to leakage currents, leading to false triggering and restricted functionality, which hinders energy savings and safe operation.
Innovation Solution
A control circuit for timing relays that includes a leakage trigger circuit and a triggering signal processing circuit, allowing a weak on-state element or external trigger apparatus to be connected in parallel, with a leakage current threshold of 100mA, enabling safe and convenient operation by connecting one terminal to either the live wire or ground terminal of an alternating current power supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a weak on-state element (e.g., neon tube pilot lamp) is connected in parallel to the trigger switch for displaying on/off state, then the display function is improved, but leakage current causes false triggering of the timing relay
Solution Approach 1:
The patent introduces an intermediary triggering signal processing circuit between the trigger switch (with parallel weak on-state element) and the timing relay. This circuit includes a comparison amplifier that compares the voltage at the trigger input terminal against a reference voltage, and only generates a triggering signal when the voltage difference exceeds a threshold. The intermediary circuit filters out the small leakage current from the weak on-state element while still detecting legitimate triggering signals, thus preventing false triggering while maintaining display functionality.
2Adaptability or versatility
If external trigger apparatus with leakage current is connected to expand functionality, then adaptability is improved, but false triggering occurs due to leakage current exceeding threshold
Solution Approach 1:
The patent changes the parameter threshold for triggering by introducing a comparison amplifier with a configurable reference voltage. Instead of directly responding to any current at the trigger terminal, the circuit only triggers when the voltage at the trigger input terminal exceeds the reference voltage by a predetermined amount. This parameter-based thresholding allows the system to accommodate external trigger apparatus with leakage currents up to certain levels while maintaining reliable operation, thus expanding adaptability without sacrificing reliability.
3Reliability
If trigger apparatus is connected to pole L or pole N of alternating current power supply for safe operation, then safety is improved, but connection flexibility is reduced due to polarity constraints
Solution Approach 1:
The patent designs the triggering signal processing circuit with universal input characteristics that can accept trigger signals regardless of whether the trigger apparatus is connected to pole L or pole N of the alternating current power supply. The comparison amplifier configuration and reference voltage selection enable the circuit to function correctly in both connection scenarios, making the timing relay universally compatible with different wiring configurations and eliminating the need for polarity-specific connection instructions, thus improving ease of operation while maintaining safety.
Data Source
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AI summary
The present invention relates to a control circuit of a timing relay. A timing/time-delay circuit includes a trigger control signal input node (control) and a control output node (out) connected with the control input terminal of a relay output circuit, and further includes a leakage trigger circuit and a triggering signal processing circuit. A normally-open trigger contact of a trigger switch is optionally connected in parallel to a weak on-state element and an external trigger terminal, a node formed by the connection of the trigger switch, the weak on-state element and the external trigger terminal is connected to an input node of the triggering signal processing circuit, and a node formed by connecting the trigger switch to the other terminal of the weak on-state element can be directly connected to any one of a pole L or a pole N on an alternating current input side of a step-down rectifier regulator circuit. The leakage trigger circuit provides a control signal to the triggering signal processing circuit, and then the timing/time-delay circuit is triggered, and then the timing/time-delay circuit controls the relay output circuit to implement on-off state conversion of a load. When a current generated by the parallel element loop does not exceed a predetermined current threshold, the timing relay will not be triggered. The present invention provides a control circuit of the time delay, which is simple and does not lead to false triggering when a weak current flows through among normally-open contacts of trigger apparatus.