Solid State Relay Zero-Crossing Control for Capacitor Recharging
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Solution Overview
Problem
Existing relay circuits that derive power from a load face challenges in accurately charging a supply capacitor, leading to incomplete charging or unnecessary disconnection due to variable charging times, and high load currents can cause voltage spikes, stressing protection components and inducing circuit noise.
Innovation Solution
A solid state relay circuit with a control circuit that includes a voltage detection circuit and a zero crossing circuit, which automatically toggles the relay switch between ON and OFF states based on capacitor voltage thresholds, ensuring optimal charging and minimizing load current during switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the relay is turned off for a fixed time to recharge the capacitor, then the capacitor can be recharged, but the relay may be turned off for too little time (incomplete charging) or too much time (unnecessary disconnection)
Solution Approach 1:
The patent employs a feedback mechanism by monitoring the voltage level of the supply capacitor through a voltage detection circuit. When the capacitor voltage drops below a predetermined threshold, the relay is automatically turned off to enable recharging. This closed-loop feedback ensures the relay is switched at the optimal moment, preventing both incomplete charging and excessive disconnection time.
Solution Approach 2:
The patent replaces the mechanical timing-based fixed-duration switch-off mechanism with an electronic voltage-threshold-based control system. Instead of using a mechanical timer to determine when to switch the relay off, the system uses electronic voltage detection and comparison circuits to intelligently determine the optimal switching moment based on actual capacitor charge status.
2Reliability
If the relay is switched off when load current is high, then the capacitor can be recharged, but the load voltage may spike to a very high level, causing protection components to trigger and causing circuit noise
Solution Approach 1:
The system continuously monitors capacitor voltage and uses this feedback to determine the optimal moment for switching the relay off. By switching based on actual voltage thresholds rather than fixed timing, the system ensures the capacitor is sufficiently charged before disconnection, preventing the need for high-load-current switching and avoiding voltage spikes and associated noise.
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
This solution ensures efficient and reliable power harvesting from a load, maintaining sufficient charge in the capacitor while reducing stress on protection components and minimizing circuit noise by precisely controlling the relay switch's state changes.
Implementation Method 1
a zero crossing circuit, coupled to the first relay line and the second relay line, and having an output to generate a clock signal when a zero crossing event takes place between the first relay line and the second relay line
Implementation Method 2
charge a supply capacitor in the power control circuit to a DC voltage using the load voltage when the relay is off
Data Source
AI summary
A relay circuit, including a solid state relay switch, connected to a first relay line and to a charging capacitor, and connected to a second relay line. The relay circuit may also include a solid state relay control circuit, coupled between the charging capacitor and the solid state relay switch. The solid state relay control circuit may include a voltage detection circuit, having an input coupled to an output of the charging capacitor, and having an output arranged to generate a LOW voltage signal when a voltage level of the charging capacitor is below a low threshold value. The solid state relay control circuit may also include a zero crossing circuit, coupled to the first relay line and the second relay line, and having an output to generate a clock signal when a zero crossing event takes place between the first relay line and the second relay line.