Capacitorless LED Driver with Dynamic String Reconfiguration
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Solution Overview
Problem
Conventional AC-DC LED drivers face issues with non-uniform LED usage leading to reduced lifetime, power dissipation, and limited power factor optimization due to the use of electrolytic capacitors and inadequate control schemes for LED string configurations.
Innovation Solution
A LED driver comprising a rectifier circuit, driving current generating circuit, bus voltage detection circuit, and LED configuration control circuit, which adjusts the on/off states of LEDs and driving current based on bus voltage levels to balance LED usage and optimize power factor, using a configuration with LEDs connected in series and switches in parallel to manage power dissipation and factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If electrolytic capacitor is used in AC-DC LED driver, then power factor can be optimized, but lifetime of LED driver is reduced and flicker is caused
Solution Approach 1:
The patent removes the electrolytic capacitor from the circuit by implementing a capacitorless power factor correction scheme using active power discretion control. The control circuit dynamically adjusts the number of LED strings in series based on input voltage levels, eliminating the need for electrolytic capacitors while maintaining power factor optimization and improving reliability.
Solution Approach 2:
The patent changes the operating parameters by dynamically adjusting the series configuration of LED strings based on input voltage levels. The control circuit switches between different LED string configurations (e.g., 12V, 24V, 36V modes) to optimize power factor across different voltage conditions without requiring electrolytic capacitors.
2Device complexity
If control variables are selected in limited scope in single-stage AC-DC LED driver, then device complexity is reduced, but efficiency optimization is limited
Solution Approach 1:
The patent implements a dynamic control scheme where the LED string configuration is continuously adjusted based on real-time input voltage detection. The control circuit dynamically switches between different series configurations to optimize power factor and efficiency across varying operating conditions, transforming a static control structure into a dynamic adaptive system.
3Device complexity
If LED strings are configured with non-uniform usage pattern, then control scheme is simplified, but lifetime of LED system is reduced due to non-uniform LED usage
Solution Approach 1:
The patent implements periodic rotation of LED string usage through dynamic reconfiguration. By periodically changing which LED strings are active based on input voltage levels, the system distributes usage evenly across all LEDs over time, preventing any single LED from being over-used while maintaining a relatively simple control scheme.
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 solution reconfigures the LED array to balance LED usage, extending the driver's lifetime while reducing power dissipation and increasing the power factor, ensuring a constant output power with improved efficiency.
Implementation Method 1
a rectifier circuit has an input for receiving an AC voltage and an output for providing a DC output voltage which is obtained by rectifying the AC voltage
Data Source
AI summary
A LED driver is disclosed herein. In one embodiment, the LED driver comprises a rectifier circuit, a driving current generating circuit, a bus voltage detection circuit, a LED configuration control circuit, and a LED array. The LED driver according to the present disclosure reconfigures the prior LED array, balances usage of each LED by switching operation of each LED, which results in long lifetime of the LED driver while reducing power dissipation or increasing a PF value.