LED Driver Circuit Using Shared Capacitor for EMI Filter Reduction
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Solution Overview
Problem
Current LED driving circuits require separate EMI filters due to high switching frequencies, increasing system costs and component count, which is not ideal for highly integrated designs.
Innovation Solution
The LED driving circuit shares a large electrolytic capacitor between the auxiliary power supply circuit and the LED load, eliminating the need for a separate filtering circuit and adaptively controls the voltage to match the load voltage, thereby operating at higher efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an EMI filter is added to the auxiliary power supply circuit, then electromagnetic interference is reduced, but system cost and component count increase
Solution Approach 1:
The patent combines the EMI filtering function with the existing output capacitor of the auxiliary power supply circuit. The capacitor serves dual purposes: power storage for the dimming control circuit and electromagnetic interference filtering. This integration eliminates the need for separate EMI filter components while maintaining both power supply and EMI protection functions.
Solution Approach 2:
The output capacitor of the auxiliary power supply circuit is designed to perform multiple functions simultaneously: it acts as both a power storage element for the dimming control circuit and an EMI filter for the high-frequency switching noise. This multi-functional design reduces overall system complexity and component count.
2Device complexity
If the voltage of the electrolytic capacitor is not regulated, then the circuit structure remains simple, but the power consumption of the linear driving circuit increases
Solution Approach 1:
The patent implements dynamic voltage regulation for the electrolytic capacitor through the dimming control circuit. The capacitor voltage is adjusted in real-time based on the dimming signal and operating conditions, allowing the system to optimize power consumption across different brightness levels while maintaining efficient linear driving circuit operation.
Solution Approach 2:
The voltage parameter of the electrolytic capacitor is dynamically changed according to the dimming control signal. By varying the capacitor voltage within a controlled range, the system achieves optimal power efficiency for the linear driving circuit while maintaining simple circuit architecture without requiring complex voltage regulation hardware.
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 design reduces system volume and cost by eliminating additional filters while maintaining high efficiency and power factor, and minimizing power consumption.
Implementation Method 1
The rectifier circuit 11 is used to convert alternate currents (AC) into direct currents (DC)
Implementation Method 2
An electrolytic capacitor EC1 is connected in parallel with the LED load 15 and in series with the linear driving circuit 14
Implementation Method 3
The auxiliary power supply circuit 12, which is typically a switch-mode power converter
Implementation Method 4
The EMI filter includes a diode D1, an inductor L1, and capacitors EC2 and EC3
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
An LED driving circuit is provided. By sharing a large capacitor between an auxiliary power supply circuit and an LED load, the LED driving circuit of the present disclosure has a simple structure without a separate filtering circuit for the auxiliary power supply circuit. The auxiliary power supply circuit is connected in parallel with an electrolytic capacitor of the LED driving circuit, and the LED load is connected in series with a linear driving circuit and then in parallel with the electrolytic capacitor. Furthermore, the LED driving circuit adaptively controls a voltage across the electrolytic capacitor, ensuring it closely matches a load voltage of the LED load, minimizing a potential difference of the linear driving circuit, allowing the LED driving circuit to operate at a relatively higher or the highest efficiency.