LED Driver Voltage Regulation for Current Limiter Loss Reduction
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Solution Overview
Problem
Existing direct mains linear LED drivers experience significant losses due to the LED current limiter, which are proportional to the AC supply voltage and LED forward voltages, with an operating window limited to the worst-case scenario of lowest mains supply voltage and maximum forward voltage, leading to inefficient operation.
Innovation Solution
An LED driver with a voltage regulating branch and feedback circuit that stabilizes the minimum residual headroom voltage on the LED current limiter, independent of mains voltage and LED forward voltages, by modulating the charging current of the capacitor using a comparator and minimum voltage detector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the LED current limiter is placed in series with the LEDs with fixed amplitude to meet regulatory guidelines, then the mains input current width is enlarged to comply with IEC 61000-3-2, but the voltage over the LED current limiter and accompanying losses increase linearly with AC supply voltage and LED forward voltages
Solution Approach 1:
The patent applies dynamics by making the LED current limiter amplitude adjustable rather than fixed. The control circuit dynamically adapts the amplitude of the LED current limiter based on operating conditions (mains voltage, LED forward voltage), allowing the system to meet regulatory guidelines while minimizing losses under different operating points.
Solution Approach 2:
The patent implements feedback through a control circuit that monitors the operating conditions and adjusts the LED current limiter amplitude accordingly. The feedback mechanism ensures that the current limiter operates at optimal amplitude to satisfy regulatory requirements while reducing unnecessary voltage drop and power losses.
2Reliability
If the driver is operated at the tuning point corresponding to lowest mains supply voltage and highest forward voltage drop, then the worst-case scenario is covered, but the loss in the LED current limiter increases linearly above the tuning point resulting in a rather small operating window
Solution Approach 1:
The patent enables dynamic operation across a wide range of conditions by allowing the LED current limiter amplitude to be adjusted in real-time. This dynamic adaptation allows the driver to operate efficiently not just at the worst-case tuning point but across a broad operating window including higher mains voltages and varying LED forward voltages.
Solution Approach 2:
The patent changes the parameter of LED current limiter amplitude from fixed to variable. By adjusting this parameter based on operating conditions, the system maintains reliable operation at the tuning point while significantly expanding the operating window to include higher mains voltages and different LED configurations.
3Reliability
If the LED current limiter amplitude is fixed to meet regulatory guidelines, then compliance is ensured, but the voltage over the LED current limiter and accompanying losses are linearly proportional to AC supply voltage and LED forward voltages
Solution Approach 1:
The patent applies dynamics by making the LED current limiter amplitude adjustable rather than fixed. The control circuit dynamically adapts the amplitude of the LED current limiter based on operating conditions (mains voltage, LED forward voltage), allowing the system to meet regulatory guidelines while minimizing losses under different operating points.
Solution Approach 2:
The patent changes the parameter of LED current limiter amplitude from fixed to variable. By adjusting this parameter based on operating conditions, the system maintains reliable operation at the tuning point while significantly expanding the operating window to include higher mains voltages and different LED configurations.
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
Reduces overall losses in the LED driver by controlling the minimum headroom voltage to a predefined value, improving efficiency and equalizing thermal load distribution across the current limiter.
Implementation Method 1
The AC mains supply voltage is rectified by utilizing, for example, a full wave rectifier
Implementation Method 2
a capacitor arranged for providing said LED voltage to said at least one LED
Implementation Method 3
a feedback circuit comprising a comparator block arranged for providing an output based on a potential difference between two input terminals of said comparator block
Data Source
AI summary
A Light Emitting Diode, LED, driver arranged for driving at least one LED, said LED driver comprising a rectifier arranged for receiving an Alternating Current, AC, supply voltage and for providing an output Direct Current, DC, voltage to said at least one LED, a voltage regulating branch arranged for controlling an LED voltage provided to said at least one LED, via a supply line, wherein said voltage regulating branch is arranged for receiving said DC voltage from said rectifier, wherein said voltage regulating branch comprises, a capacitor arranged for providing said LED voltage to said at least one LED, a current limiter, connected in series with said capacitor, and arranged for charging said capacitor thereby providing said LED voltage and a feedback circuit arranged for controlling the charging of said capacitor by said current limiter, and thereby controlling the LED voltage provided to said at least one LED, by regulating a minimum residual headroom voltage present on a LED current limiter coupled in series with said at least one LED.