Solid-State Photocontrol for Luminaire Power Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional photocontrols for luminaires consume significant power and have short lifespans, especially when used with solid-state light sources, due to high inrush currents and contactor damage, necessitating a solution for low-power consumption and long-term reliability.
Innovation Solution
A photocontrol apparatus utilizing an ambient light sensor, AC sense circuit, and switch control circuit with MOSFET switches, which consumes minimal power and switches at zero-crossing of the AC input voltage, eliminating mechanical relays and reducing inrush currents, and includes a DC power supply circuit and microcontroller for enhanced control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electro-mechanical relays are used to switch power to luminaires, then the photocontrol can reliably control high voltage and current loads, but the relay contactors suffer from corrosion due to arcing and inrush currents, reducing their lifespan
Solution Approach 1:
The patent replaces electro-mechanical relays with solid-state switching devices (MOSFETs or triacs) that have no moving parts or contactors. This eliminates the mechanical wear and arcing problems that limited relay lifespan, while maintaining the ability to switch high voltage and current loads reliably. The solid-state switch is controlled by a photocontrol circuit that detects ambient light levels and switches the load accordingly.
2Adaptability or versatility
If conventional photocontrol circuits are used with solid-state light sources, then the luminaires can be controlled, but the high inrush currents from LED drivers cause additional damage to relay contactors
Solution Approach 1:
By replacing the electro-mechanical relay with a solid-state switch, the system can handle the high inrush currents from LED drivers without the contactor damage that plagues mechanical relays. Solid-state devices can withstand these current spikes without physical degradation.
Solution Approach 2:
The photocontrol circuit detects ambient light levels and prepares to switch the load before the actual lighting transition occurs. This allows the solid-state switch to be ready to handle inrush currents smoothly, preventing damage by anticipating the switching event.
3Power
If capacitive drop technology is used to power photocontrol circuits, then the circuits can operate at line voltages, but the photocontrols consume considerable amounts of power
Solution Approach 1:
The patent employs a high-impedance photocontrol circuit design that dramatically reduces power consumption while maintaining the ability to operate at line voltages. The circuit uses minimal current to sense light levels and control the solid-state switch, reducing power consumption from the milliwatt range to the microwatt range.
Solution Approach 2:
The solid-state switching device requires minimal drive current compared to electro-mechanical relays, allowing the photocontrol circuit to operate with very low power consumption while still effectively controlling high voltage and current loads.
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 power savings, extended lifespan, and reliability by reducing power consumption to microwatts and eliminating mechanical relay contacts, making it suitable for both low and high power loads with a power factor near one.
Implementation Method 1
an ambient light sensor having an output terminal which provides a signal responsive to an amount of light sensed by the ambient light sensor
Implementation Method 2
an AC sense circuit having an input terminal and an output terminal, the input terminal of the AC sense circuit electrically coupleable to the AC power source, the output terminal provides an AC sense signal indicative of at least one characteristic of the AC power source
Implementation Method 3
a switch including an input terminal, an output terminal and a control terminal, the input terminal electrically coupleable to a line terminal of the AC power source, the output terminal electrically coupleable to a load terminal of the luminaire
Data Source
AI summary
Photocontrol apparatus that controls a luminaire or other load such that the luminaire is switched on during nighttime hours and off during the daytime. The photocontrol consumes only microwatts of power in either the ON or the OFF state, unlike traditional relay- or triac-based photocontrols. The photocontrol does not require a voltage generating photo sensor to generate power for the photocontrol. A solar cell, semiconductor photo diode or photo diode string, cadmium sulfide cell, semiconductor ambient light sensor, etc., may be used as the sensor element. The photocontrol switches power to the load at the zero-crossing of an AC input voltage, which reduces inrush current and the switching currents caused by traditional photocontrols which may switch at any point on the AC input voltage waveform.