AC/DC Linear LED Driver Circuit Eliminates EMI Noise
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Solution Overview
Problem
Conventional driving circuits for LEDs generate electromagnetic interference (EMI) noise and require bulky components like inductors, making them difficult to integrate into compact lighting fixtures, such as E12, E14, E17 light bulbs, or T-5 and T-8 tubes, while also being less efficient and more costly.
Innovation Solution
The implementation of an AC/DC linear converter that eliminates EMI noise by using a bridge rectifier, a power MOSFET switch, and control circuitry to regulate current through the LED array, allowing for high power efficiency and factor without the need for additional filtering components, and can be mounted on a thin printed circuit board for easier integration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a switching-mode DC/DC converter is used to power LEDs, then power conversion is achieved, but electromagnetic interference (EMI) noise is generated requiring additional EMI filter components
Solution Approach 1:
The patent extracts and removes the EMI filter component from the conventional LED driving circuit by eliminating the source of EMI noise through the use of a switching regulator that directly drives the LED string without requiring separate EMI filtering components
Solution Approach 2:
The patent converts the harmful EMI noise generation into a benefit by using a switching regulator topology that inherently suppresses EMI through its switching mechanism and integrated design, transforming the problem of EMI into an advantage of reduced component count
2Power
If a switching-mode DC/DC converter with inductor and capacitor is used, then power conversion is achieved, but the circuit size becomes large and difficult to fit into compact lighting fixtures
Solution Approach 1:
The patent merges the power conversion function and LED driving function into a single integrated switching regulator circuit, eliminating the need for separate bulk capacitor and EMI filter components, thereby reducing overall circuit volume while maintaining power conversion capability
Solution Approach 2:
The patent extracts and removes the bulky inductor and large capacitor components from the conventional circuit design, replacing them with a compact switching regulator topology that achieves the same power conversion function in a smaller form factor suitable for compact LED lighting fixtures
3Power
If a bridge rectifier and large electrolytic capacitor are used to convert AC to DC, then voltage rectification and filtering is achieved, but the circuit complexity and component size increase
Solution Approach 1:
The patent merges the AC-to-DC rectification function with the LED driving function into a single integrated circuit, eliminating the need for separate bridge rectifier and large electrolytic capacitor components, thereby reducing circuit complexity while maintaining voltage rectification capability
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 high power efficiency and factor, reduces component bulk, eliminates the need for EMI filters, and allows for smaller, more cost-effective LED driving circuits suitable for compact lighting fixtures, enhancing both performance and design flexibility.
Implementation Method 1
a bridge rectifier (204) for rectifying an AC voltage (VAC) to a rectified AC voltage (VREC)
Implementation Method 2
a power MOSFET switch (Q1) controlling a current flowing through the LED array (210)
Implementation Method 3
an LED array (210) having a plurality of LED strings
Implementation Method 4
Light-emitting diodes (LEDs) generate virtually no heat and utilize a fraction of the energy to produce an equivalent lumen of lighting
Data Source
AI summary
Embodiments in accordance with the present invention provide circuits and methods for driving light sources, e.g., a light-emitting diode (LED) light source. In one embodiment, a lamp includes a rectifier rectifying an AC voltage to a rectified AC voltage, an LED light source, and a switch coupled to the LED light source in series controlling a current through the LED light source according to a predetermined current reference. The LED light source and the switch coupled in series receive the rectified AC voltage while the switch is controlled linearly.