Color Correcting LED Driver Eliminates Inductors via AC Synchronization
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Solution Overview
Problem
Existing color correcting device drivers for LEDs face inefficiencies due to large, costly, and unreliable capacitors and inductors, which increase size and reduce lifespan, while also requiring more components to achieve power factor correction and efficient LED lighting.
Innovation Solution
A color correcting device driver that varies the equivalent current into LEDs with the frequency of the AC input, reducing the need for large capacitors and inductors by using ceramic capacitors and removing unnecessary components like recirculating diodes and inductors, while implementing PWM signals and fly-back controllers for power factor correction and efficient LED operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional color correcting device drivers are used with large capacitors and inductors for power factor correction, then power factor correction and efficient energy delivery are achieved, but the system size increases, cost increases, and reliability decreases
Solution Approach 1:
The patent removes the inductor and recirculating diode from the traditional LED driver circuit, extracting unnecessary components that contribute to system complexity and reliability issues. The color correcting LED string is driven directly from the rectified AC voltage without requiring these additional components, thereby improving reliability while reducing device complexity.
Solution Approach 2:
The device controller performs multiple functions: it controls the switching of both the white LED string and color correcting LED string, implements power factor correction by varying equivalent current with AC input frequency, and regulates LED current without requiring separate dedicated components for each function. This multi-functionality reduces the overall component count while maintaining system reliability.
2Reliability
If large capacitors are used to compensate for current supplied by the PFC controller, then power factor correction is achieved, but the capacitor size and cost increase
Solution Approach 1:
The device controller varies the equivalent current into the LEDs periodically at the frequency of the rectified AC input voltage. This periodic current variation synchronizes with the AC input, reducing the need for large capacitors to smooth current fluctuations. The controller adjusts the duty cycle of PWM signals to white LED and CA LED transistors in sync with the rectified AC voltage, thereby reducing capacitor size while maintaining reliable power factor correction.
3Ease of operation
If inductors and recirculating diodes are included in the circuit for proper current regulation, then current control is achieved, but the system becomes more complex and less reliable
Solution Approach 1:
The patent replaces the traditional inductor-based current control mechanism with an electronic control system. The device controller uses PWM switching of transistors to regulate current through both white LED and color correcting LED strings, eliminating the need for physical inductors and recirculating diodes. This substitution maintains precise current control while significantly reducing circuit complexity and improving reliability.
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 achieves power factor correction, high efficiency, and extended product lifespan with reduced component costs and size, using smaller capacitors and eliminating unnecessary components, thereby enhancing LED lighting performance and reliability.
Implementation Method 1
the color correcting device driver can create a pulse width modulation (PWM) signal by detecting the starting point for a sine wave PWM approximation
Implementation Method 2
The output color of a white Light Emitting Diode (LED) has some deficiencies in the form of reduced color in some parts of the visible spectrum
Data Source
AI summary
A color correcting device driver is configured to vary the equivalent current into light emitting elements (e.g., LEDs) with the frequency of the AC input current (e.g., 120 Hz). In implementations that include a fly-back controller with a power factor correction (PFC) controller on the primary side, the color correcting device driver performs the method of: 1) turning on the loads (e.g., white and CA strings of LEDs); 2) determining if the voltage supplied to the loads has dropped by a first threshold amount; 3) turning off the loads; and 4) determining if the voltage supplied to loads has recovered by a second threshold amount (or waiting for a fixed amount of time). The method is repeated. In implementations that do not include a PFC controller on the primary side, the color correcting device driver can create a pulse width modulated (PWM) signal.