LED Driver Circuit for AC Line Power with Segment Switching
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Solution Overview
Problem
Existing LED drivers for AC line power are inefficient, costly, and unsuitable for direct replacement of incandescent bulbs, with issues including low power delivery, lack of temperature compensation, no dimming arrangements, and incompatibility with existing dimmer switches, leading to reduced efficiency and increased energy costs due to variable AC input voltage and low LED utilization.
Innovation Solution
A system that adapts to a wide AC input voltage range by monitoring current levels and switching LED segments in and out of the current path, maintaining constant current, and providing power factor correction, allowing for efficient power delivery and control of brightness, color temperature, and color, while reducing component count and size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If LED drivers are designed without isolation transformers to reduce component count, then device complexity is reduced, but the converter size increases due to low operating frequency
Solution Approach 1:
The patent implements dynamic frequency adjustment where the converter operates at variable frequencies depending on the duty cycle. When duty cycle exceeds 50%, the frequency is increased to maintain stable operation, preventing the converter size from increasing while still eliminating the need for isolation transformers.
Solution Approach 2:
The patent changes the operating parameters by allowing duty cycle to exceed 50% and adjusting frequency dynamically based on operating conditions. This parameter flexibility enables the converter to maintain compact size without isolation transformers by operating in a regime where high-frequency switching is sustained even at high duty cycles.
2Illumination intensity
If high brightness LEDs are used requiring large currents, then illumination intensity is improved, but system efficiency decreases and energy costs increase
Solution Approach 1:
The patent implements feedback control where the output current is monitored and used to regulate the switching duty cycle. This ensures that LEDs receive precisely the current needed for optimal brightness without excessive current that would waste energy, maintaining high efficiency while achieving high illumination intensity.
Solution Approach 2:
The patent uses periodic PWM switching to deliver current to LEDs in controlled pulses rather than continuous large currents. This periodic action achieves high average brightness while reducing peak current demands and associated energy losses, improving overall system efficiency.
3Measurement precision
If current mode regulator with ramp compensation is used in PWM circuit, then control precision is improved, but device complexity increases and stability problems persist at duty cycle over fifty percent
Solution Approach 1:
The patent extracts and eliminates the complex ramp compensation circuitry from the PWM controller by implementing current mode control with inherent stability characteristics. The design uses simplified current sensing and feedback that naturally provides stable operation at duty cycles exceeding 50% without requiring additional compensation networks.
Solution Approach 2:
The patent replaces complex analog ramp compensation circuits with a digital or microcontroller-based control system that calculates and adjusts PWM duty cycle based on sensed current feedback. This substitution reduces hardware complexity while maintaining or improving control precision and stability at high duty cycles.
4Stability of the object's composition
If constant off-time boost converter or hysteretic pulse train booster is used to address instability, then stability is improved, but electromagnetic interference increases and efficiency decreases
Solution Approach 1:
The patent implements dynamic frequency adjustment where the switching frequency varies based on the duty cycle and load conditions. This dynamic operation allows the converter to maintain stability at high duty cycles while avoiding the fixed-frequency limitations of constant off-time converters, thereby reducing electromagnetic interference and improving efficiency.
Solution Approach 2:
The patent changes the operating parameters by allowing duty cycle to exceed 50% and adjusting frequency dynamically based on operating conditions. This parameter flexibility enables the converter to maintain compact size without isolation transformers by operating in a regime where high-frequency switching is sustained even at high duty cycles.
5Adaptability or versatility
If multiple different products are required for different input voltage levels, then adaptability to specific voltage levels is improved, but device complexity and cost increase
Solution Approach 1:
The patent designs a universal LED driver circuit that can operate across a wide range of input voltages (including both 110V and 220V AC) using the same hardware platform. The controller adapts its operation based on detected voltage level, eliminating the need for multiple product variants and reducing complexity while maintaining broad voltage compatibility.
Solution Approach 2:
The patent implements dynamic voltage detection and adaptation where the controller automatically adjusts its operating parameters based on the detected input voltage level. This dynamic adaptation allows a single product design to universally support multiple voltage standards without requiring physical switches or multiple circuit boards.
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 system achieves high LED utilization, energy savings, and reduced component costs by maintaining constant current and power factor correction, enabling efficient operation over a wide AC voltage range and providing control over lighting parameters.
Implementation Method 1
a plurality of light emitting diodes coupled in series to form a plurality of segments of light emitting diodes
Data Source
AI summary
An apparatus, method, and system are disclosed for providing AC line power to lighting devices such as light emitting diodes (“LEDs”). A representative apparatus comprises: a plurality of LEDs coupled in series to form a first plurality of segments of LEDs; a plurality of switches coupled to the plurality of segments of LEDs to switch a selected segment into or out of a series LED current path in response to a control signal; a current sensor; and a controller which, in response to a first parameter and during a first part of an AC voltage interval, generates a first control signal to switch a corresponding segment of LEDs into the series LED current path; and during a second part of the AC voltage interval, generates a second control signal to switch the corresponding segment of LEDs out of the first series LED current path.