Dim-To-Warm LED Circuit With Single-Control CCT Dimming
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Solution Overview
Problem
Contemporary lighting systems require separate devices for controlling light output and correlated color temperature (CCT), which is costly and inefficient, especially for applications like retail and hospitality where a dim-to-warm LED lighting solution is desired.
Innovation Solution
A hybrid-driving scheme using a single control-device to manage both luminous flux and CCT, employing a dim-to-warm LED circuit that adjusts color temperature in response to dimming, utilizing a combination of desaturated RGB LEDs and a hybrid driving-circuit with analog current-division and PWM time-slicing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If LEDs are operated at high drive currents to achieve fast dimming response, then the dimming speed is improved, but the LED lifespan deteriorates due to increased stress on LED components
Solution Approach 1:
The patent applies preliminary action by pre-charging the capacitor during the LED's normal operation phase before the dimming event occurs. This stored energy in the capacitor is then discharged during dimming to provide the necessary drive current, enabling fast dimming response without subjecting the LED to high stress currents that would otherwise reduce its lifespan.
Solution Approach 2:
The patent introduces a capacitor as an intermediary energy storage element between the power supply and the LED. This intermediary stores electrical energy during normal operation and releases it during dimming events, mediating the current delivery to achieve fast response without direct high-current stress on the LED components.
2Device complexity
If conventional LED dimming control is used, then the circuit complexity is low, but the dimming precision and control accuracy deteriorate
Solution Approach 1:
The patent implements feedback control by continuously monitoring the LED's actual brightness output and comparing it against the desired dimming level. The control circuit adjusts the capacitor charging/discharging characteristics based on this feedback to achieve precise dimming control, overcoming the limitations of simple resistive dimming methods.
Solution Approach 2:
The patent changes the operational parameters of the LED circuit by dynamically controlling the capacitor's charge and discharge rates. By adjusting these temporal parameters rather than relying on static resistive control, the system achieves precise dimming control with moderate circuit complexity.
3Ease of manufacture
If simple resistive dimming control is used, then the circuit design is simple, but the dimming response time and precision deteriorate
Solution Approach 1:
The patent applies preliminary action by pre-charging the capacitor during normal LED operation. This stored energy enables the circuit to respond instantly to dimming commands without the delay inherent in resistive dimming circuits, achieving both simplicity and speed through the capacitor's pre-positioned energy.
Solution Approach 2:
The patent utilizes periodic charging and discharging of the capacitor to achieve rapid dimming transitions. The capacitor charges during normal operation and discharges during dimming events, creating a periodic energy transfer mechanism that enables fast response while maintaining circuit simplicity.
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
Enables efficient control of color temperature and luminous flux with a single device, maintaining high color-rendering index (CRI) and power efficiency, mimicking the dim-to-warm behavior of incandescent bulbs, while reducing installation costs.
Implementation Method 1
a capacitor connected in parallel to the LED circuit, wherein the capacitor is charged by the LED circuit and discharged to provide high drive current to the LED circuit during a dimming event
Implementation Method 2
Light Emitting Diode (LED) circuit
Data Source
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AI summary
Various embodiments include apparatuses and methods enabling a dim-to-warm circuit operation of an LED multi-colored array. In one example, an apparatus includes a hybrid driving-circuit coupled to the LED array and to a single control- device to receive an indication of a luminous flux desired from the LED array. A color temperature for the LED array is determined based on the desired luminous flux of the LED array. In various embodiments, the hybrid driving-circuit includes an analog current - division circuit to produce current for at least two LED current -driving sources and a multiplexer array coupled between the analog current - division circuit and the LED to provide periodically, for a predetermined amount of time, current from at least one of the at least two LED current¬ driving sources to at least two colors of the LED array. Other apparatuses and methods are described.