Multi-segment LED Driving Circuit for AC Voltage Adaptation
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Solution Overview
Problem
Existing LED lamps with constant current architecture struggle to maintain stable operation and low total harmonic distortion (THD) across varying AC voltages, leading to unstable product quality and increased costs when attempting to adapt to different markets, and result in reduced economic benefits.
Innovation Solution
A multi-segment LED driving circuit with a simple architecture that includes a detection part, comparison part, and adjusting part, using an AND gate, operational amplifier, and N-type metal oxide semiconductor field effect transistor (N-MOSFET) to detect and adjust voltage changes, ensuring constant current flow through LED strings and stabilizing operation quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a constant current architecture with current resistor and operational amplifier is used to control LED drive current, then the drive current can be maintained constant, but the total harmonic distortion (THD) varies with AC voltage changes and becomes difficult to control at high output power levels
Solution Approach 1:
The LED string is divided into multiple segments (first LED string and second LED string) with different numbers of LEDs, allowing independent control of each segment. The control circuit selectively activates different segments based on input voltage levels, enabling THD control across varying AC voltage conditions while maintaining constant current operation in each active segment.
Solution Approach 2:
The control circuit dynamically adjusts the operating state of different LED segments based on real-time detection of input voltage changes. By switching between different segment configurations according to voltage levels, the system adapts to maintain stable THD and constant current operation across different AC voltage conditions.
2Adaptability or versatility
If additional safety components are installed to stabilize THD, then the THD control improves, but the cost of the lamps increases
Solution Approach 1:
The control circuit integrates multiple functions into a single design: it detects input voltage changes, determines active segments, controls drive current, and stabilizes THD. By making the control circuit multi-functional, the patent eliminates the need for separate safety components, thereby stabilizing THD without increasing cost.
Solution Approach 2:
The control circuit incorporates feedback mechanisms that monitor input voltage and adjust the operation of LED segments accordingly. This feedback loop enables the circuit to automatically stabilize THD without requiring additional safety components, as the control circuit itself responds to voltage changes and adjusts operation to maintain stable harmonic distortion.
3Illumination intensity
If LEDs are connected in series to increase output power, then the illumination intensity increases, but the difficulty of controlling THD within a range increases
Solution Approach 1:
The LED string is segmented into multiple groups with different numbers of LEDs, allowing the control circuit to activate different segments based on input voltage levels. This segmentation enables the system to maintain manageable THD levels even when high illumination intensity is required, as the control circuit can selectively activate appropriate segments rather than forcing all LEDs to operate simultaneously.
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 circuit effectively adjusts LED string operation based on AC voltage changes, maintaining constant current and reducing power consumption and operating temperature, thereby improving service life and efficiency while stabilizing THD and reducing costs.
Implementation Method 1
a N-type metal oxide semiconductor field effect transistor (N-MOSFET) and a current resistor to restrict a constant drive current passing through the LEDs by the current resistor
Implementation Method 2
a negative feedback circuit formed by connecting the operational amplifier, the N-MOSFET and the current resistor is provided for stepping down the voltage at both ends of the current resistor and maintaining the voltage constant
Implementation Method 3
it is a main subject for related manufacturers to find a way of controlling the illumination brightness, operating efficiency and service life of LED lamps
Data Source
AI summary
Disclosed is a multi-segment LED driving circuit used in an AC operating mode for outputting a drive current to drive a plurality of serially connected LED strings. The LED driving circuit includes at least one detection part, at least one comparison part and at least one adjusting part. The detection part detects an input voltage and an output voltage at both ends of each string and its next string to form a detected value provided for the comparison part to compare the detected value with a reference value to turn on or off the adjusting part so as to control the strings through which the drive current passes and then sequentially drives the strings to emit light. The LED driving circuit can adjust the load of the circuit immediately based on the change of voltage value of the AC power to ensure the stability of the drive current.