LED Driver Shunt Switch Circuit for Ballast Compatibility
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Solution Overview
Problem
Existing LED tube lamps face challenges in compatibility with various electromagnetic ballasts, leading to poor power factor, unbalanced light output, flicker, and safety issues when retrofitted into fluorescent lighting fixtures, particularly with compensated ballast configurations and aluminum tube architectures.
Innovation Solution
A light-emitting diode (LED) tube lamp with a shunt switch circuit and switching mode power supply that includes a rectifier, shunt switching device, output capacitor, diode, voltage sensor, current sensor, and processor to detect ballast types and regulate bus voltage, ensuring high power factor, balanced series connections, and safe operation across different ballast configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional switching mode power supply driver is used behind an electromagnetic ballast, then the LED lamp can operate, but the power factor becomes very poor
Solution Approach 1:
The patent introduces a parallel capacitor as an intermediary component connected across the AC input lines to the electromagnetic ballast. This capacitor compensates for the inductive reactive power consumed by the ballast, thereby improving the overall power factor of the lighting system without affecting the LED driver operation
Solution Approach 2:
The patent modifies the electrical parameters of the system by adding a capacitor with specific capacitance value calculated to compensate for the ballast's inductive reactance. This changes the overall impedance characteristics of the circuit, improving power factor while maintaining LED operation
2Ease of operation
If two TLED lamps are connected in series with a conventional SMPS driver, then the lamp configuration is achieved, but flicker and unbalanced light output occur
Solution Approach 1:
The patent employs a microcontroller-based control system that dynamically adjusts the switching timing and duty cycle of each LED string to balance the light output. The controller monitors the operating conditions and adapts the drive parameters in real-time to eliminate flicker and ensure uniform illumination from both series-connected lamps
Solution Approach 2:
The patent incorporates feedback mechanisms where the microcontroller monitors the voltage and current waveforms across each LED string and adjusts the switching parameters accordingly. This closed-loop control ensures balanced operation and eliminates flicker by synchronizing the drive signals with the ballast's operating cycle
3Strength
If an LED lamp is designed with aluminum tube-based architecture, then structural advantages are achieved, but safety issues arise related to mains power
Solution Approach 1:
The patent introduces a double insulated plastic tube as an intermediary layer between the aluminum tube and the internal electronic components. This non-conductive barrier provides electrical isolation and prevents direct contact with mains voltage, thereby ensuring safety while maintaining the structural advantages of the aluminum tube architecture
Solution Approach 2:
The patent implements preliminary safety measures by designing the aluminum tube with integrated insulation layers and proper grounding paths before the device is put into operation. The insulation coating and structural design prevent electrical hazards from the outset, addressing safety concerns proactively rather than reactively
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 enables LED tube lamps to maintain high power factor, prevent flicker, and ensure safe operation in aluminum tube-based architectures when retrofitted into existing lighting fixtures with various electromagnetic ballasts, addressing compatibility and safety concerns.
Implementation Method 1
The shunt switch circuit includes a shunt switching device configured to switch the bus voltage on and off
Implementation Method 2
The shunt switching device is turned on at a zero crossing of a rectifier current
Implementation Method 3
maintain a high power factor when used in a lighting fixture with a compensated EM ballast configuration... provide galvanic isolation between the shunt switch circuit and the one or more light emitting diodes
Data Source
Figure 1A~1F
Figure 2
Figure 3
AI summary
A lighting driver includes a shunt switch circuit configured to detect when an input of the lighting driver is connected to mains power without a ballast, and in response thereto to disable the lighting driver, and further configured to detect a type of ballast connected to the input of the lighting driver when the input of the lighting driver is connected to the ballast, and to regulate a bus voltage of the shunt switch circuit according to the detected type of ballast; and a switching mode power supply configured to receive the bus voltage of the shunt switch circuit and in response thereto to supply a lamp current to drive one or more light emitting diodes.