LED Driver Bridge Switching for Flicker Reduction
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Solution Overview
Problem
Existing LED driver systems face challenges with light output flicker, reduced efficiency, and compatibility issues with dimmers due to the use of fill-in capacitors, which lead to increased costs and complexity, especially when operating with mains voltage.
Innovation Solution
A driver device and method that incorporate a rectifier unit, capacitive storage unit, and bridge switching unit to efficiently manage AC supply voltage, allowing for 100% load current flow and reduced losses by alternately charging and discharging a capacitive storage unit, thereby improving power factor and reducing flicker.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fill-in capacitor is inserted to maintain light output when mains voltage falls below LED string voltage, then light output stability is improved, but device complexity and cost increase
Solution Approach 1:
The bridge switching unit performs multiple functions: it rectifies AC voltage, charges the capacitive storage unit, switches the capacitor into/out of the LED current path, and provides polarity control. This multi-functionality eliminates the need for separate fill-in capacitor circuits while maintaining light output stability, thereby reducing device complexity while improving reliability
Solution Approach 2:
The capacitive storage unit is charged to nearly the peak value of the rectified mains voltage in advance during high voltage periods. This preliminary charging ensures that when mains voltage drops below LED string voltage, the pre-charged capacitor can immediately supply energy to maintain continuous light output without requiring complex real-time detection and switching circuits
2Reliability
If a fill-in capacitor is used to supply energy during low voltage periods, then light output continuity is improved, but energy efficiency deteriorates
Solution Approach 1:
The bridge switching unit operates in periodic cycles, switching the capacitive storage unit into the LED current path during high mains voltage periods to charge the capacitor, and switching it out during low voltage periods to discharge. This periodic switching optimizes energy utilization by capturing energy when available and releasing it when needed, maintaining light continuity while improving overall driver efficiency compared to continuous capacitor discharge approaches
Solution Approach 2:
The capacitive storage unit provides continuous energy supply to the LEDs by being charged during high voltage periods and discharged during low voltage periods without interruption to light output. This continuous energy transfer mechanism ensures uninterrupted useful action (light emission) while minimizing energy losses compared to linear current sources that dissipate excess voltage as heat
3Device complexity
If the number of voltage taps is limited to avoid high complexity, then device complexity is reduced, but voltage mismatch and energy losses increase
Solution Approach 1:
The bridge switching unit dynamically changes the operating parameters by switching the capacitive storage unit into and out of the LED current path based on the instantaneous mains voltage level. This parameter change approach allows the system to adapt to varying voltage conditions without requiring multiple fixed voltage taps, reducing circuit complexity while minimizing voltage mismatch losses through dynamic adjustment
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 achieves a non-lossy, high power factor operation for LED lighting systems, reducing total losses by half and improving compatibility with dimmers, while maintaining stable light output and power efficiency.
Implementation Method 1
a rectifier unit for rectifying a received AC supply voltage
Implementation Method 2
a capacitive storage unit coupled between said rectifier unit and said load terminals for storing electrical energy provided by said rectifier unit and providing electrical energy to said load
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
Driver device and a corresponding driving method for driving a load, in particular an LED assembly comprising one or more LEDs. To provide a better performance, better cost-efficiency, improved power factor and reduced losses, a driver device (1,1', 2, 2') is provided comprising a rectifier unit (10) for rectifying a received AC supply voltage (Vs), load terminals (20) for providing a drive voltage (VL) and/or a drive current (IL) for driving said load, a capacitive storage unit (30) coupled between said rectifier unit and said load terminals for storing electrical energy provided by said rectifier unit and providing electrical energy to said load, and a bridge switching unit (40) coupled between said rectifier unit and said load for switching said capacitive storage unit into a load current path from said rectifier unit to said load terminals with a desired polarity and for switching said capacitive storage unit out of said load current path.