LED Driver Dimming via Pause Duration Current Adjustment
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Solution Overview
Problem
LED luminaire designers face challenges in designing products that can work with various legacy dimming-control technologies and emerging wireless-network-control scenarios, as existing solutions require multiple components to respond correctly to phase-control dimmers, increasing complexity and cost.
Innovation Solution
The proposed solution utilizes the length of the pause in the input voltage during phase-cut dimming to adjust the current to LEDs, generating a pulse signal proportional to the pause duration, which is used in the current control loop to decrease the LED output current accordingly, thereby simplifying the driver design and reducing system costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple functional blocks are added to support phase-control dimming, then LED dimming response accuracy is improved, but device complexity and system cost increase
Solution Approach 1:
The patent extracts the dimming control function from complex separate functional blocks and integrates it into the existing current control loop. By measuring the pause duration between AC half-cycles and converting it directly into a current adjustment signal, the solution eliminates the need for separate sensors, processors, and control circuits while maintaining accurate dimming response.
Solution Approach 2:
The patent merges the phase-cut detection function with the existing current measurement and control functions. The pause duration measurement is performed using the same timing circuitry that monitors LED current, and the dimming control signal is generated by directly adjusting the current reference level, combining multiple functions into a unified control approach.
2Reliability
If multiple functional blocks are added to support phase-control dimming, then LED dimming response accuracy is improved, but system cost increases
Solution Approach 1:
The patent removes the need for expensive separate dimming control components by extracting the essential dimming function and implementing it through simple pause duration measurement and current reference adjustment, significantly reducing component count and system cost.
Solution Approach 2:
The existing current control loop and timing circuitry serve dual purposes: they monitor LED current for protection and control, and simultaneously measure the pause duration for dimming control. The system uses its own existing resources to perform the dimming function without requiring additional dedicated hardware.
3Device complexity
If analog dimming is used to control LED drive current, then implementation simplicity is improved, but LED color consistency deteriorates at lower currents
Solution Approach 1:
The patent implements a feedback mechanism where the measured pause duration continuously adjusts the current reference level in real-time. This closed-loop control ensures that the LED current is precisely controlled according to the desired dimming level, maintaining color consistency across different brightness levels by dynamically adapting the drive current rather than using fixed analog reduction.
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 approach allows for efficient dimming of LEDs by using the pause duration in the input voltage to control the current, reducing the number of components needed and enhancing the simplicity and cost-effectiveness of LED driver designs while maintaining consistent brightness and color performance.
Implementation Method 1
a transformer having a primary side and a secondary side. The primary side is operable to transfer energy to the secondary side responsive to an input signal
Implementation Method 2
A current control loop of the LED driver is operable to control current in the primary side so that the output current equals a reference current signal
Data Source
AI summary
An LED driver includes a transformer, current control loop and current adjustment circuit. The primary side of the transformer transfers energy to the secondary side of the transformer responsive to an input signal. The secondary side delivers output current to one or more LEDs at a magnitude corresponding to the amount of energy transferred to the secondary side. The current control loop controls current in the primary side so that the output current equals a reference current signal. The current adjustment circuit injects a current adjustment signal into the current control loop responsive to a phase-cut signal which removes a portion of the input signal. The current control loop also decreases the current in the primary side responsive to the current adjustment signal so that a brightness of each LED connected to the secondary side is decreased by an amount corresponding to the magnitude of the current adjustment signal.