Light-emitting Device Control Circuit for Stable LED Current
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional control circuits for light-emitting devices experience variations in light intensity and power factor due to changes in AC input voltage amplitude, leading to inconsistent LED current and light emission, as the reference voltage amplitude increases with varying AC input voltage, affecting the duration of LED current flow.
Innovation Solution
The control circuit incorporates a reference voltage generation circuit that suppresses changes in reference voltage amplitude by generating a reference voltage through a subtraction circuit using a differential amplifier, ensuring the peak voltage remains constant regardless of AC input voltage variations, thereby stabilizing the LED current and light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the reference voltage is generated by simple voltage division from the rectified AC voltage, then the circuit structure is simple, but the reference voltage amplitude varies with AC input voltage changes, causing LED current and light intensity to become unstable
Solution Approach 1:
The patent changes the parameter of reference voltage generation from simple voltage division to a circuit that suppresses amplitude changes. The reference voltage generation circuit uses a combination of voltage division and amplitude suppression mechanisms to maintain stable reference voltage amplitude regardless of AC input voltage variations, thereby stabilizing LED current and light intensity.
2Adaptability or versatility
If the reference voltage amplitude increases with AC input voltage variations, then the circuit responds to input changes, but the LED current duration becomes inconsistent, affecting light emission stability
Solution Approach 1:
The patent implements a feedback mechanism where the reference voltage generation circuit continuously monitors and adjusts the reference voltage to suppress amplitude changes. This feedback control ensures that the comparison voltage threshold remains stable, maintaining consistent LED current duration and stable light emission intensity regardless of AC input voltage fluctuations.
3Device complexity
If the comparator uses the varying reference voltage for comparison, then the circuit operates with simple comparison logic, but the LED current flow duration varies, causing inconsistent light output
Solution Approach 1:
The patent applies preliminary action by pre-stabilizing the reference voltage amplitude before it reaches the comparator. The reference voltage generation circuit performs amplitude suppression in advance, ensuring that the comparator receives a stable reference voltage. This preliminary stabilization ensures consistent comparison results and reliable LED current control, maintaining steady light output.
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 solution reduces the variation in light emission intensity and improves the power factor by maintaining a consistent current through the LED, even with changes in AC input voltage amplitude, ensuring stable light output and efficient energy use.
Implementation Method 1
a rectification circuit (10) that rectifies an AC voltage to generate a rectified voltage
Implementation Method 2
generating a reference voltage through a subtraction circuit using a differential amplifier
Implementation Method 3
A full-wave rectified voltage Vrc is supplied to an anode of an LED 60 as a drive voltage
Data Source
AI summary
In a control circuit for a light-emitting device, a reference voltage generation circuit detects a full-wave rectified voltage and generates a first voltage as well as generating a second voltage by converting the rectified voltage into a DC voltage. A voltage corresponding to a difference between the first voltage and the second voltage or a voltage corresponding to a ratio of the first voltage to the second voltage is generated as a reference voltage by a subtraction circuit or by a division circuit, respectively. As a result, a change in amplitude of the reference voltage can be suppressed when amplitude of the rectified voltage is varied due to a variation in an AC input voltage supplied from an AC power supply.