LED Dimming Circuit Dynamic Frequency Control
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Solution Overview
Problem
Conventional LED illumination dimming circuits face issues with increased noise and decreased efficiency due to higher switching frequencies during dimming, limited dimming range, and the need for multiple terminals for control signals, which restricts the ability to lower switching frequency below audio frequencies and increases component size.
Innovation Solution
An LED illumination dimming circuit that modulates the switching period and ratio of on and off periods based on dimming signal thresholds, using a controlling circuit with a switch element, capacitor, resistor, and diode to achieve dimming across multiple modes, reducing the frequency change range and requiring only one signal input terminal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the conventional LED illumination dimming circuit lowers the peak current to achieve dimming, then the dimming function is achieved, but the switching frequency of the bipolar transistor increases
Solution Approach 1:
The circuit dynamically adjusts the switching frequency based on the dimming level. At higher dimming levels, the switching frequency is kept lower, and at lower dimming levels, the frequency increases. This dynamic adjustment resolves the contradiction by adapting the switching frequency to the operational requirements rather than maintaining a fixed frequency throughout all dimming ranges.
Solution Approach 2:
The patent changes the operational parameters of the bipolar transistor, specifically transitioning from constant current control to a mode where the transistor operates as a switch with variable duty cycle. This parameter change allows the circuit to achieve dimming through pulse-width modulation rather than continuous current reduction, thereby controlling the switching frequency independently from the dimming level.
2Object-affected harmful factors
If the switching frequency is lowered when dimming is not performed, then the noise is reduced, but the dimming range is limited
Solution Approach 1:
The switching frequency is made dynamic rather than fixed. The circuit automatically adjusts the frequency based on the desired dimming level, allowing low frequency operation at high brightness (reducing noise) while maintaining the capability to operate at higher frequencies when deep dimming is required (expanding dimming range).
3Object-affected harmful factors
If the switching frequency is lowered, then the noise is reduced, but the size of components such as transformer increases
Solution Approach 1:
By making the switching frequency dynamic and operating at higher frequencies when needed, the patent reduces the size of magnetic components like transformers and inductors. Higher switching frequencies allow for smaller component sizes, while the dynamic nature ensures noise is minimized during normal operation when high frequency is not required.
4Measurement precision
If the conventional LED illumination dimming circuit uses multiple terminals for control signals, then the control precision is improved, but the device complexity increases
Solution Approach 1:
The patent implements a universal control interface where a single terminal accepts dimming control signals that can operate the circuit across all dimming ranges. The controlling circuit internally generates the necessary control waveforms and adjusts parameters dynamically, eliminating the need for separate terminals for different control functions while maintaining precise control throughout the entire dimming range.
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 circuit provides a wide dimming range with reduced frequency change, minimizing audible noise and maintaining high efficiency by adjusting switching frequencies and periods according to dimming rates, while reducing the number of required terminals.
Implementation Method 1
a coil connected in series with the LED element... a switch element that switches the coil on and off based on a switch controlling signal
Implementation Method 2
a capacitor connected in parallel with the LED element
Implementation Method 3
a diode connected in parallel with the coil
Data Source
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AI summary
An LED illumination dimming circuit comprises a capacitor connected to the first output terminal at a first end thereof and to the second output terminal at a second end thereof; a coil connected to the second end of the capacitor at a first end thereof; a switch element connected to a second end of the coil at a first end thereof; a resistor connected to a second end of the switch element at a first end thereof and to the ground terminal at a second end thereof; a diode connected to the power supply terminal at a cathode thereof and to the second end of the coil at an anode thereof; and a controlling circuit that controls an operation of the switch element with a switch controlling signal depending on a dimming signal that indicates a dimming rate of the LED element, a detection voltage responsive to a voltage drop in the resistor and a detection current flowing through the coil.