LED Driver Average Current Regulation Eliminates Output Capacitors
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Solution Overview
Problem
Existing LED lighting control methods require large and costly output capacitors and rectifier diodes, and constant peak current control leads to variations in average LED current with input voltage changes, affecting illumination stability.
Innovation Solution
An LED driver that extracts LED lighting current information to produce signals for regulating average current, eliminating the need for output capacitors and rectifier diodes, and using a feedback loop with a filter to maintain constant average current, with control signals having constant on-time or off-time and switching frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If constant peak current control is used to regulate LED current, then the control circuit can operate without large output capacitors, but the average LED current varies with input voltage changes
Solution Approach 1:
The patent implements a feedback mechanism that senses the LED current and adjusts the power switch duty cycle to maintain constant average current. The controller monitors the actual LED current and compares it with the desired average current level, then dynamically adjusts the switching ratio to compensate for input voltage variations, thereby stabilizing the average LED current without requiring large output capacitors.
Solution Approach 2:
The patent transitions from static peak current control to dynamic average current control. The controller continuously adjusts the power switch duty cycle based on real-time conditions to maintain constant average current. This dynamic adjustment allows the system to adapt to varying input voltages while keeping the average LED current stable, eliminating the need for large filtering capacitors.
2Stability of the object's composition
If large output capacitors are used to filter LED current, then the average current becomes stable, but the component size and cost increase
Solution Approach 1:
The patent uses a feedback control mechanism that senses LED current and adjusts the power switch duty cycle to maintain stable average current without large capacitors. The controller continuously monitors the current and dynamically adjusts the switching ratio, replacing the need for large passive filtering components with an active control system.
Solution Approach 2:
The patent replaces the passive mechanical filtering approach (large output capacitors) with an active electronic control system. Instead of using large capacitors to physically filter and smooth the current, the system uses intelligent switching control to synthesize a stable average current, substituting electronic control for passive component filtering.
3Adaptability or versatility
If rectifier diodes are used in the LED driver circuit, then the circuit can handle varying input voltages, but the component cost and size increase
Solution Approach 1:
The patent makes the power switch perform multiple functions: it acts as both the main power switching element and the rectifying element. By controlling the duty cycle of the power switch, the circuit can handle varying input voltages without requiring separate rectifier diodes. The single power switch replaces multiple components, reducing circuit complexity and cost while maintaining adaptability to different input voltage conditions.
Data Source
AI summary
An LED driver providing an LED lighting current to an LED path, extracts the LED lighting current information from the LED path to produce a first signal including an AC component and a DC component, and extracts the DC component information of the first signal to produce a second signal to regulate an average of the LED lighting current. This LED driver implements real constant average current regulation for an LED lighting apparatus, eliminates the need of output capacitor as well as rectifier diode in most applications to simplify the circuit of the power stage, and is applicable to power stages of various modes.