Retrofit LED Driver Impedance Regulation for Ballast Noise Reduction
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Solution Overview
Problem
Retrofit LED lamps experience noise issues and failure to turn off correctly due to incompatible high frequency electronic ballasts, primarily because the impedance seen by the ballast is too small during off periods or deep dimming states, leading to excessive output current from the ballast.
Innovation Solution
A retrofit LED driver that regulates output impedance by introducing additional impedance when the LED load power is below a threshold, using a power conversion circuit, switch arrangement, and regulation circuit to maintain a higher impedance, ensuring the ballast operates within a suitable range and reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the LED load power is reduced below a threshold (deep dimming or off state), then the LED power consumption is reduced, but the impedance seen by the ballast becomes too small causing noise and incorrect turn-off
Solution Approach 1:
The patent introduces an additional impedance element as an intermediary component between the power conversion circuit and the LED light source. This intermediary impedance prevents the ballast from detecting too low an impedance during deep dimming or off states, thereby eliminating audible noise while allowing the LED to consume reduced power. The additional impedance acts as a mediator that decouples the LED's low-power state from the ballast's impedance detection.
Solution Approach 2:
The patent dynamically changes the output impedance parameter of the driver circuit based on the LED load power level. When the LED power is below a threshold, the regulation circuit activates to increase the output impedance. This parameter change ensures the ballast always sees a suitable impedance range, preventing noise generation while allowing the LED to operate at low power consumption levels.
2Loss of energy
If the LED load power is reduced below a threshold, then the LED power consumption is reduced, but the LED lamp fails to turn off correctly due to excessive ballast output current
Solution Approach 1:
The additional impedance element serves as a mediator that prevents excessive current from the ballast during off states. By introducing this impedance, the circuit ensures proper current limitation even when the LED is supposed to be off, thereby achieving reliable turn-off functionality while maintaining low power consumption capability.
Solution Approach 2:
The regulation circuit monitors the LED load power level and provides feedback control. When the LED power drops below a threshold, the feedback mechanism activates the additional impedance to prevent excessive ballast current, ensuring correct turn-off behavior. This closed-loop feedback ensures reliable operation across different power levels.
3Object-affected harmful factors
If additional passive components are added to increase output impedance, then the impedance regulation is achieved, but the circuit cost and complexity increase
Solution Approach 1:
The patent merges the impedance regulation function with the existing regulation circuit in the LED driver. Instead of adding separate passive components, the invention integrates the additional impedance control into the power conversion circuit's regulation mechanism. This merging approach achieves the required impedance regulation while minimizing additional circuit complexity and cost.
Solution Approach 2:
The regulation circuit in the LED driver is made to serve dual purposes: its original function and the additional function of impedance regulation. By enabling the existing regulation circuit to automatically adjust the output impedance when needed, the system achieves noise reduction without requiring separate dedicated components, thereby reducing overall circuit complexity.
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 effectively reduces audible noise and ensures the LED lamp turns off correctly by maintaining a suitable impedance, even during deep dimming or standby modes, without the need for additional passive components, thus reducing cost and complexity.
Implementation Method 1
a power conversion circuit which is arranged to receive AC power at its input from the high frequency ballast and, in use, to convert said AC power to an output power at a power terminal of the power conversion circuit for coupling to the LED light source
Implementation Method 2
a regulation circuit for regulating a voltage at the power terminal so as to regulate an output impedance as seen from the high frequency ballast by introducing an additional impedance of non-LED light source
Data Source
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AI summary
A retrofit LED driver is for connecting to a high frequency ballast and for driving a LED load. A switch arrangement is used to couple the driver output power to the LED load or isolate the output power from the LED load. Voltage regulation is used when the output power is isolated from the LED load, and current regulation is used when the output power is coupled to the LED load. The voltage regulation is used so as to increase an output impedance as seen from the high frequency ballast by introducing an additional impedance of non-LED light source, when the output power coupled to the LED light source is less than a threshold, for example in deep dimming mode or standby mode instructed by the user. In this way, the effective impedance of the lamp is increased, which enables switching noise to be reduced, meanwhile the overall LED output power is not increased, as desired by the user.