Controllable-Load Circuit for Thyristor Holding Current Control
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Solution Overview
Problem
Existing load control systems for LED light sources often waste power by conducting current through dimmer switches unnecessarily, as they do not have the ability to adjust current delivery in response to changing power requirements, leading to inefficiencies in controlling high-efficiency electrical loads like LED light sources.
Innovation Solution
A load control device with a controllable-load circuit and controller that adjusts the magnitude of the controllable-load current in response to phase-control voltage conduction time, ensuring the current exceeds the rated holding current of the thyristor only when necessary, thereby optimizing power delivery to LED light sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed load circuit conducts current through the dimmer switch, then the thyristor holding current requirement is met, but unnecessary power is dissipated when the load does not require full current
Solution Approach 1:
The load control circuit dynamically adjusts the magnitude of controllable-load current based on real-time monitoring of conduction time. The controller decreases the current magnitude from an initial value to a decreased value when the conduction time indicates the thyristor is already maintaining conduction, thereby reducing power dissipation while ensuring reliable operation.
Solution Approach 2:
The system changes the parameter of controllable-load current magnitude from a fixed initial magnitude to a variable decreased magnitude. This parameter adjustment is triggered by monitoring the conduction time of phase-control voltage, allowing the system to optimize power delivery by reducing current when full current is not necessary for maintaining thyristor conduction.
2Loss of energy
If the controllable-load current magnitude is continuously reduced to minimize power loss, then energy efficiency improves, but the thyristor may fail to maintain conduction
Solution Approach 1:
The controller monitors the conduction time of phase-control voltage as feedback and uses this information to adjust the controllable-load current magnitude. When the conduction time indicates stable thyristor operation, the controller decreases the current magnitude; when conduction time suggests the thyristor is approaching non-conduction, the controller maintains or increases current to ensure reliable operation.
Data Source
AI summary
A load control device for controlling the amount of power delivered from an AC power source to an electrical load is operable to conduct enough current through a thyristor of a connected dimmer switch to exceed rated latching and holding currents of the thyristor. The load control device comprises a controllable-load circuit operable to conduct a controllable-load current through the thyristor of the dimmer switch. The load control device disables the controllable-load circuit when the phase-control voltage received from the dimmer switch is a reverse phase-control waveform. When the phase-control voltage received from the dimmer switch is a forward phase-control waveform, the load control device is operable to decrease the magnitude of the controllable-load current so as to conduct only enough current as is required in order to exceed rated latching and holding currents of the thyristor.