Integrated Single-Stage AC-DC LED Driver for Weight Reduction
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Solution Overview
Problem
Aircraft electrical distribution systems face challenges in reducing weight and increasing efficiency while meeting the demands for power factor correction and high power density, particularly in AC-DC converters used for LED loads, which often result in high ripple and harmonic distortion.
Innovation Solution
An integrated single-stage AC-DC driver is developed, combining a boost converter operating in Discontinuous Conduction Mode with a Zeta Asymmetrical Half Bridge, sharing a half-bridge for power factor control and using a feedforward feedback loop to eliminate ripple and flicker, along with a resonant inductor for zero voltage switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional two-stage AC-DC converter is used, then power factor correction and output voltage control are achieved, but the device weight and complexity increase
Solution Approach 1:
The patent merges the Power Factor Correction (PFC) stage and the DC-DC conversion stage into a single integrated circuit. The PFC boost converter and the Zeta Asymmetrical Half Bridge are combined to share common components including the half-bridge switches, input capacitor, and magnetic elements, thereby reducing overall device weight and complexity while maintaining both PFC and output voltage control functions
Solution Approach 2:
The integrated converter achieves multi-functionality by making the single-stage circuit perform both PFC and DC-DC conversion tasks simultaneously. The shared half-bridge and magnetic components serve dual purposes: enabling power factor correction while also providing output voltage regulation, thus eliminating the need for separate dedicated stages
2Weight of stationary object
If capacitor size is reduced to decrease weight, then weight is reduced, but ripple and harmonic distortion increase
Solution Approach 1:
The patent employs resonant inductors that create controlled oscillations to cancel out harmful voltage ripples. The resonant elements are designed to operate at specific frequencies that counteract the ripple components, allowing for reduced capacitor sizing without compromising output voltage quality
Solution Approach 2:
The integrated control system incorporates feedback mechanisms that actively monitor and compensate for voltage ripple and harmonic distortion. By using the shared control circuitry to detect and correct ripple issues in real-time, the system maintains low distortion levels even with smaller capacitors
3Power
If switching frequency is increased to improve power density, then power density increases, but switching losses and EMI increase
Solution Approach 1:
The converter operates in Discontinuous Conduction Mode (DCM) with periodic switching cycles that allow complete demagnetization of the inductors. This periodic operation at optimized frequencies enables high power density while controlling switching losses through the natural reset of magnetic elements during each cycle
Solution Approach 2:
The patent optimizes switching frequency as a variable parameter to achieve the best compromise between power density and switching losses. By carefully selecting and adjusting the switching frequency based on load conditions and component characteristics, the system maximizes power density while minimizing energy losses and electromagnetic interference
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 solution achieves high power density, reduced capacitor requirements, and compliance with harmonic regulations, ensuring stable LED lighting with extended lifetime and improved efficiency, suitable for both aircraft and household applications.
Implementation Method 1
a resonant inductor, Llkg, configured to completely discharge a first and a second primary switch of the half-bridge to enable zero voltage switching of the primary switches
Implementation Method 2
a feedforward feedback loop configured to provide proportional integral feedback control to remove ripple and eliminate flicker at the output voltage
Data Source
AI summary
An integrated single stage ac-dc driver for powering LED loads includes a boost converter operating in a Discontinuous Conduction Mode, DCM, comprising a half-bridge, and a Zeta Asymmetrical Half Bridge, ZAHB, integrated with the boost converter such that the boost converter and the ZAHB share the half-bridge to perform power factor control, PFC, with a fixed duty cycle and control an output voltage.