LED Power Circuit Noise Suppression via Ground Capacitance Segmentation
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Solution Overview
Problem
Prior art LED power-source circuits face challenges in reducing high-frequency noise propagation to the input power-source line and improving surge performance, as increased capacitance for noise reduction compromises surge voltage tolerance.
Innovation Solution
The proposed LED power-source circuit incorporates an input filter circuit with noise prevention capacitors and a line filter, a diode bridge for rectification, a smoothing capacitor with a capacitance of 1 μF or less, and a DC-DC conversion circuit, with additional capacitors connected from the power-source line to the fixture ground, setting the total capacitance to 1/200 or less of the smoothing capacitor to suppress noise and surge voltage effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the capacitance between the circuit ground and the fixture ground is increased to suppress noise terminal voltage, then the noise propagation to the input power-source line is reduced, but the ability of the circuit to tolerate surge voltage (common mode) decreases
Solution Approach 1:
The patent segments the capacitance function by separating the noise suppression capacitance (connected between circuit ground and fixture ground) from the surge protection capacitance (connected between power-source line and fixture ground). This segmentation allows each capacitance to be optimized for its specific function without compromising the other, resolving the contradiction between noise suppression and surge tolerance.
Solution Approach 2:
The patent introduces an intermediary capacitance configuration where the total capacitance from the power-source line to the fixture ground is set to 1/200 or less of the smoothing capacitor's capacitance. This intermediary capacitance acts as a mediator that allows noise suppression while maintaining surge voltage tolerance by providing a controlled impedance path.
2Stability of the object's composition
If a smoothing capacitor with larger capacitance is used to smooth the pulsating voltage, then the voltage smoothing performance is improved, but the high-frequency noise propagation to the input power-source line increases
Solution Approach 1:
The patent applies parameter changes by setting the smoothing capacitor's capacitance to 1 μF or less, which is a significant reduction from conventional values. This parameter change reduces the capacitor's ability to filter high-frequency noise while maintaining adequate voltage smoothing for the LED driver circuit, thereby resolving the contradiction between voltage stability and noise suppression.
Solution Approach 2:
The patent segments the filtering function by separating the smoothing capacitor's role in voltage stabilization from the noise filtering role, which is handled by the input filter circuit and ground capacitance. This segmentation allows the smoothing capacitor to have small capacitance without compromising overall noise suppression performance.
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 configuration effectively reduces high-frequency noise propagation and protects the lamp fixture from damage by maintaining surge voltage within acceptable limits, enhancing the circuit's ability to handle common-mode voltage surges.
Implementation Method 1
a diode bridge for rectifying an AC input voltage
Implementation Method 2
a smoothing capacitor for smoothing a pulsating voltage from the diode bridge
Data Source
AI summary
An LED power-source circuit includes an input filter circuit including noise prevention capacitors and a line filter, a diode bridge connected to the input filter circuit, a smoothing capacitor connected to an output of the diode bridge and having a capacitance of 1 μF or less, a DC-DC conversion circuit connected to the smoothing capacitor, and an LED assembly connected to an output of the DC-DC conversion circuit. Grounding capacitors are coupled to ground from an input power line between the line filter and the diode bridge. The total capacitance from the input power line to ground is set to be 1/200 or less of that of the smoothing capacitor.