LED Control Circuit Varies Clock Period to Disperse Spike Noise
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Solution Overview
Problem
Existing control circuits for light-emitting elements, such as LEDs, generate spike noise and electromagnetic interference (EMI) near the clock frequency, exceeding standard values due to fixed clock frequencies.
Innovation Solution
A control circuit that varies the period of the clock signal generated by a clock generator, using a counter to cyclically count values and adjust the switching intervals of the switching element, thereby widening the frequency distribution of spike noise and reducing noise influences at specific frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed clock frequency is used in the control circuit, then the current control and light emission intensity management are simple and stable, but spike noise and electromagnetic interference exceed standard values
Solution Approach 1:
The patent applies dynamics by making the clock frequency variable rather than fixed. The control circuit dynamically adjusts the clock frequency within a predetermined range, transforming the static timing signal into a dynamic one that adapts to reduce electromagnetic interference while maintaining reliable current control of the light-emitting element
Solution Approach 2:
The patent changes the frequency parameter of the clock signal to resolve the contradiction. By varying the clock frequency within a specified range, the system alters the timing characteristics of the switching element, which disperses the spike noise energy across different frequencies and reduces electromagnetic interference to within standard values while preserving control stability
2Object-generated harmful factors
If the clock frequency is varied to reduce electromagnetic noise, then noise levels are reduced to within standards, but the control complexity increases
Solution Approach 1:
The patent employs periodic action by implementing a clock generator that produces periodic timing signals with variable frequency. The switching element operates in synchronization with this periodic clock signal, maintaining regular switching intervals while adapting the frequency to minimize electromagnetic interference, thus reducing noise without requiring complex non-periodic control mechanisms
Solution Approach 2:
The control circuit achieves multi-functionality by integrating frequency variation capability into the existing clock generator and switching control structure. The same basic circuit architecture that provides stable current control also generates the variable frequency clock signal, allowing the system to perform both noise reduction and reliable control functions without significantly increasing overall circuit complexity
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
The varying clock signal period reduces electromagnetic noise, ensuring that the light-emitting element's current control and emission intensity are managed effectively, minimizing interference and adhering to standard noise levels.
Implementation Method 1
a rectifying unit which full-wave rectifies an alternating current power supply
Implementation Method 2
There is being developed an illumination system which uses a light-emitting diode (LED) as a light-emitting element for illumination
Data Source
AI summary
A control circuit of a light-emitting element comprises a rectifying unit which full-wave rectifies an alternating current power supply, a clock generator which generates and outputs a clock signal (CLK), a first comparator which compares a comparison voltage (CS) corresponding to a current flowing to the light-emitting element and a reference voltage (REF), and a switching element which is set to an ON state in synchronization with the clock signal (CLK) and which is set to an OFF state when the comparison voltage (CS) becomes greater than the reference voltage (REF) at the first comparator, to switch the current flowing to the light-emitting element. In this structure, a period of the clock signal (CLK) generated in the clock generator is varied, to reduce or inhibit noise.