Voltage Conversion Circuit for LED Brightness Control
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Solution Overview
Problem
Existing circuit arrangements for voltage conversion lack flexibility in powering electrical loads, particularly in devices like mobile communications and cameras, where they often fail to maintain consistent brightness and color spectrum of LEDs while minimizing audible vibrations.
Innovation Solution
A circuit arrangement with a forward branch and a feedback branch, utilizing pulse width modulation and a sampling device to control voltage conversion, allowing for flexible power supply to LEDs with independent clock phases and frequency modulation above 20 kHz, ensuring constant current operation and linear brightness control without color spectrum changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If pulse width modulation is used to control LED brightness, then brightness control flexibility is improved, but audible mechanical vibrations are generated in components
Solution Approach 1:
The patent changes the frequency parameter of the pulse width modulation from audible range (below 20 kHz) to ultrasonic range (above 20 kHz). This parameter change eliminates audible mechanical vibrations in components while preserving the brightness control flexibility through pulse duty ratio adjustment. The sampling device captures voltage information at specific clock phases to maintain proper control despite the frequency change.
Solution Approach 2:
The patent uses periodic pulse width modulation with clock phases to control LED brightness. The periodic sampling at specific clock phases (first clock phase for sampling, second clock phase for holding) ensures proper control signal generation while operating at frequencies above 20 kHz to avoid audible vibrations. The periodic action maintains both control flexibility and eliminates harmful audible effects.
2Object-affected harmful factors
If pulse width modulation frequency is increased above 20 kHz to avoid audible vibrations, then harmful vibrations are reduced, but control precision may be affected
Solution Approach 1:
The sampling device performs preliminary sampling of the voltage at the first load terminal during the first clock phase before the second clock phase begins. This preliminary action captures the necessary voltage information at the optimal moment in the pulse width modulation cycle, ensuring precise control signals are generated even at ultrasonic frequencies above 20 kHz where audible vibrations are eliminated.
Solution Approach 2:
The feedback branch with the sampling device provides feedback by sampling the voltage at the first load terminal and using this information to control the forward branch. This feedback mechanism ensures precise control of the voltage conversion process, maintaining control precision even when operating at high frequencies above 20 kHz to avoid audible vibrations.
3Illumination intensity
If LED current is varied to change brightness, then brightness control is achieved, but color spectrum changes occur
Solution Approach 1:
The patent uses periodic pulse width modulation to control LED brightness by adjusting the pulse duty ratio rather than varying the LED current. The LED operates at constant current during its activated phase, which maintains stable color spectrum. The brightness variation is achieved through the periodic on-off switching with different duty ratios, not through current variation, thus decoupling brightness control from color spectrum stability.
Data Source
AI summary
A circuit arrangement (1) for voltage conversion comprises a forward branch (60) with a first load terminal (45) to which an electrical load (47) can be coupled and a feedback branch (61) with a sampling device (30). The electrical load (47) can be operated with pulse width modulation. A method for voltage conversion comprises the following steps: an electrical load (47) is supplied with energy using pulse width modulation. A feedback voltage (Vfb) that can be tapped at a terminal of the electrical load (47) is sampled in a first clock phase during which the electrical load (47) is supplied with energy. The voltage conversion is controlled as a function of the feedback voltage (Vfb).