LED Linear Driving Circuit High Power Factor Heat Dissipation
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Solution Overview
Problem
Existing LED linear driving circuits have a low power factor and high harmonic content due to rectangular wave currents, and they face heat dissipation issues with constant LED loads, limiting flexibility and efficiency.
Innovation Solution
The proposed LED linear driving circuit uses discrete MOS tubes arranged on a PCB in parallel, with a current detecting circuit comprising a diode and resistors to regulate the current waveform, allowing for flexible LED load configuration and improved heat dissipation, resulting in a high power factor and low harmonic content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If rectangular wave currents are used to form input current, then the circuit structure is simple, but the power factor is low and harmonic wave content is high
Solution Approach 1:
The patent transforms the static rectangular wave current into a dynamic sine wave current that continuously adjusts its shape to match the input voltage waveform. This is achieved through the control circuit that dynamically modulates the switching signals to the MOS tubes, converting the fixed-frequency rectangular waves into variable-waveform currents with sinusoidal characteristics, thereby improving power factor while maintaining circuit simplicity
Solution Approach 2:
The patent changes the waveform parameter of the input current from rectangular to sinusoidal by adjusting the switching duty cycles and timing of the MOS tubes. The control circuit modifies the current waveform parameters in real-time to follow the voltage waveform, transforming the harmonic-rich rectangular current into a low-harmonic sine wave current without fundamentally changing the circuit topology
2Device complexity
If chip package with integrated power MOS tubes is used, then the integration degree is high, but the heat dissipation performance is poor
Solution Approach 1:
The patent divides the integrated power MOS tube into separate discrete components: the MOS tubes are no longer integrated within the chip package but are instead implemented as external discrete devices mounted on the PCB. This segmentation allows each MOS tube to be independently positioned for optimal heat dissipation, separating the high-current power switching function from the integrated control circuitry, thereby improving thermal management while maintaining integration through careful PCB layout
Solution Approach 2:
The patent moves the power MOS tubes from a two-dimensional integrated layout within the chip package to a three-dimensional PCB mounting arrangement. By utilizing the PCB as a heat dissipation substrate with larger surface area and better thermal pathways, the system transitions from confined internal heat management to external dimensional heat dissipation, allowing for improved thermal performance through PCB trace design and heat sink attachment
3Device complexity
If constant number of LED loads is used, then the circuit design is simple, but the flexibility and efficiency are low
Solution Approach 1:
The patent introduces dynamic load switching capability that allows the number of LED loads to be adjusted in real-time based on system requirements. The control circuit dynamically selects and switches between different LED load configurations, transforming the static constant-load design into a dynamic multi-load system that can adapt its LED count to match power availability and lighting requirements, thereby improving flexibility without significantly increasing circuit complexity
Solution Approach 2:
The patent designs the circuit to support multiple LED load configurations simultaneously, where the same circuit infrastructure can drive different numbers of LED loads based on switching control. The load switching circuit provides universal functionality to accommodate various LED array arrangements (series, parallel, or combinations), allowing the system to serve multiple operating modes and applications through a single unified design rather than requiring separate circuits for each load configuration
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 enables the input current waveform to follow the input voltage waveform, enhancing compliance with standards and achieving higher efficiency by dynamically adjusting the number of LED loads based on system requirements.
Implementation Method 1
the current detecting circuit comprises the first diode, the fifth resistor and the sixth resistor, the first diode is configured to counteract BE junction voltage of the triode Q2 of the error amplifying circuit so that the waveform of the current is closer to the waveform of the output voltage of the input voltage sampling circuit
Implementation Method 2
an AC power supply and a rectifier bridge circuit are marked as 11
Data Source
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Figure 6
AI summary
The disclosure relates to an LED linear driving circuit, which is used for driving sequentially series-connection n LED loads, wherein the anode of a first LED load is connected with the anode of a direct current (DC) voltage, and the cathode of an (n-1)-th LED load is connected with the anode of an n-th LED load; the n is greater than or equal to 2; and the LED linear driving circuit is characterized by comprising an input voltage sampling circuit, an error amplifying circuit, an adder circuit, a current detecting circuit and a load switching circuit. The LED linear driving circuit may help the waveform of the input current to basically follow the waveform of the input voltage to show a waveform of the sine wave; in the LED linear driving circuit, MOS tubes utilize discrete devices and are arranged on a PCB in parallel, so that the arrangement positions of the MOS tubes are flexible, and excellent heat dissipation performance and reliability are achieved; additionally, one or a plurality of LED loads can be randomly utilized according to system efficiency requirements, and the more the utilized LED loads are, the higher the efficiency is.