LED Dimming Control via Transformer Isolation and Offset Cancellation
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Solution Overview
Problem
Existing LED lighting devices with dimming circuits face challenges in accurately controlling dimming due to high circuit complexity and large inductance requirements, leading to increased costs and potential secondary damage from overvoltage failures.
Innovation Solution
A dimming control method using a first control unit with a rectifier and offset voltage cancellation part, which includes resistors and a Zener diode, to cancel offset voltage and generate a correction voltage, combined with a transformer for isolation, allowing for precise dimming control with a simple structure and reduced inductance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dimming circuit with isolation structure is used to prevent failure spread, then reliability is improved, but device complexity increases due to multiple semiconductor elements
Solution Approach 1:
The patent extracts the isolation function from a complex multi-semiconductor circuit and implements it using a simple transformer-based isolation structure. The transformer isolates the primary side (LED array) from the secondary side (dimmer), achieving failure isolation without requiring multiple semiconductor elements, thus reducing circuit complexity while maintaining reliability.
2Reliability
If a general isolation structure is used, then failure isolation is achieved, but the size of isolation transformer increases due to large inductance requirements
Solution Approach 1:
The patent changes the inductance parameter of the transformer to a low value, which directly reduces the transformer size. By optimizing the transformer design with low inductance requirements, the patent achieves failure isolation without the need for a large-sized transformer, thus resolving the contradiction between reliability and transformer volume.
3Reliability
If a dimming circuit with multiple semiconductor elements is used, then isolation function is achieved, but manufacturing cost increases
Solution Approach 1:
The patent replaces expensive multiple semiconductor elements with a simpler transformer-based isolation structure that uses fewer and less expensive components. This substitution achieves the same isolation function while significantly reducing manufacturing costs, making the dimming circuit more economically viable.
4Reliability
If large inductance is demanded for isolation, then failure isolation is achieved, but space efficiency decreases
Solution Approach 1:
The patent changes the inductance parameter to a low value, which reduces the physical size of the transformer and consequently the space required on the circuit board. This parameter optimization achieves failure isolation while improving space efficiency and reducing the overall circuit footprint.
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 approach results in a high-accuracy dimming circuit with reduced production costs and prevents failure propagation between LED lighting devices, using a small-sized transformer and minimizing inductance value impact.
Implementation Method 1
transmitting the pulse signal generated in the first control unit to a second control unit including a dimmer through a transformer
Implementation Method 2
rectifying, by the first control unit, the dimming control signal, which is an alternating current signal transmitted through the transformer, to a direct current signal
Implementation Method 3
The correction voltage may be generated by the plurality of resistors connected in series to the dimmer and the Zener diode or shunt regulator connected to the one of the plurality of resistors in parallel
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
An LED lighting device according to one embodiment of the present invention comprises: an LED array; a first control unit for controlling the dimming of the LED array; a second control unit for transmitting, to the first control unit, a dimming control signal for controlling the dimming of the LED array; and a transformer comprising a primary coil and a secondary coil spaced apart from each other, wherein the first control unit is connected to the primary coil, the second control unit is connected to the secondary coil, the primary coil and the secondary coil are insulated from each other, the transformer transmits a pulse signal that repeats on/off at predetermined intervals from the first control unit to the second control unit, and, when the pulse signal transmitted from the first control unit to the second control unit via the transformer becomes off, the dimming control signal is transmitted from the second control unit to the first control unit via the transformer and is used to control the dimming of the LED array.