LED Lighting Apparatus Current Control Circuit
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Solution Overview
Problem
PWM dimming of LEDs often results in variations in current amplitude due to characteristics of LEDs and power supply outputs, leading to potential damage from overshoot or inrush currents.
Innovation Solution
A lighting apparatus comprising a lighting unit, a converting circuit, a sensing circuit, and a current control circuit that indirectly detects the current flowing through the LED, generating feedback signals to control the current amplitude, preventing overshoot and inrush currents by using a sensing circuit configured at different positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If PWM dimming is used to control LED brightness, then dimming depth and color change are improved, but current amplitude stability deteriorates due to LED and power supply variations
Solution Approach 1:
The patent implements a feedback mechanism where a sensing circuit detects the actual current flowing through the LED and feeds this information back to the control circuit. The control circuit then adjusts the PWM duty cycle based on this feedback to compensate for variations in LED characteristics and power supply output, thereby maintaining stable current amplitude while preserving PWM dimming capabilities.
Solution Approach 2:
The system uses the LED's own current flow as the sensing signal, eliminating the need for separate sensing resistors or additional components in the current path. The sensing circuit indirectly detects the LED current through the existing circuit configuration, allowing the system to self-regulate without external intervention.
2Stability of the object's composition
If direct current detection is used to control LED current, then current amplitude stability is improved, but device complexity increases due to additional sensing components
Solution Approach 1:
The patent introduces an intermediary sensing circuit that indirectly detects the LED current through the existing power supply and switching circuitry. Instead of placing a sensing resistor directly in series with the LED, the system uses the voltage across existing components (such as the switching device or power supply output) as a proxy signal to infer the LED current, thereby reducing the need for additional components.
Solution Approach 2:
The sensing circuit is designed to serve multiple functions: it detects current for regulation purposes, provides feedback for PWM control, and can potentially serve as a protection mechanism. By making the sensing circuit multi-functional, the patent reduces the need for separate dedicated current sensing components, thereby reducing overall device complexity.
3Device complexity
If no sensing circuit is used, then device complexity is reduced, but overshoot and inrush currents may damage the apparatus
Solution Approach 1:
The patent implements preliminary action by using the sensing circuit to detect current conditions before damage can occur. The feedback signal is continuously monitored during the startup and operation phases, allowing the control circuit to preemptively adjust PWM duty cycles or switching timings to prevent overshoot and inrush currents from damaging the LED or other components.
Solution Approach 2:
The sensing circuit provides continuous feedback on the actual current flowing through the LED, enabling the control circuit to detect abnormal conditions (such as inrush current during startup or overshoot during switching transitions) and respond in real-time by adjusting PWM parameters or switching timings to prevent damage.
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
Maintains constant current amplitude, preventing damage from overshoot and inrush currents, and ensuring stable operation of the LED lighting apparatus.
Implementation Method 1
The sensing circuit includes a sensing element for indirectly detecting the current flowing through the LED and outputting a feedback signal
Data Source
AI summary
A lighting apparatus includes a lighting unit, a converting circuit, a sensing circuit, and a current control circuit. The lighting unit includes at least one light emitting diode and a switching device connected with each other in series. The converting circuit has an output end electrically connected to the lighting unit for driving it. The sensing circuit includes a sensing element capable of indirectly detecting the current flowing through the light emitting diode and outputting a feedback signal. The current control circuit receives a reference current, the feedback signal and a dimming command, and sends a dimming control signal to the lighting unit and a current control signal to the converting circuit, capable of controlling the amplitude of the current flowing through the light emitting diode.