Lips Backlight Control Architecture for Low Cost Dead Time Transfer
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Solution Overview
Problem
Existing LIPS architectures face challenges in reducing power consumption and cost due to excessive power loss and high switching losses, particularly in transferring drive signals across isolation transformers, which are necessary for efficient operation of CCFL and LED lighting systems.
Innovation Solution
The proposed solution involves driving an isolation transformer with a drive signal that exhibits high, low, and high impedance states, coupled via a capacitor, allowing for efficient transfer of switching dead time across the transformer, thereby reducing the need for additional circuitry and minimizing power losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional LIPS architecture uses standard switching networks to drive CCFL or LED lamps, then the system can provide basic lighting function, but excessive power loss and high switching losses occur due to hard switching characteristics
Solution Approach 1:
The patent implements resonant half-bridge switching where the switching frequency is modulated to match the resonant frequency of the lamp circuit. This periodic resonant action enables soft switching, reducing switching losses and improving power efficiency while maintaining ease of operation through automatic frequency synchronization.
Solution Approach 2:
The patent changes the switching frequency parameter dynamically to match the resonant frequency of the lamp circuit. By adjusting this parameter, the system transitions from hard switching to soft switching, reducing power losses while maintaining operational simplicity through automatic frequency adaptation.
2Reliability
If isolation transformers are used to transfer drive signals across primary and secondary sides, then galvanic isolation is achieved, but additional circuitry is required increasing device complexity and cost
Solution Approach 1:
The patent makes the isolation transformer perform multiple functions: it provides galvanic isolation, transfers drive signals, and enables resonant half-bridge switching operation. By making the transformer multi-functional, the system achieves reliable galvanic isolation without requiring additional separate circuitry, thereby reducing device complexity.
Solution Approach 2:
The isolation transformer serves as an intermediary that transfers resonant drive signals from the primary side to the secondary side while maintaining galvanic isolation. This intermediary function is integrated directly into the transformer, eliminating the need for additional signal transfer circuitry and reducing overall device complexity.
3Power
If high voltage DC is converted to low voltage DC and then to AC voltage for driving fluorescent lamps, then voltage matching is achieved, but excessive power loss occurs due to multiple conversion stages
Solution Approach 1:
The patent extracts and eliminates the intermediate low voltage DC conversion stage from the traditional power conversion path. By directly resonant half-bridge switching from high voltage DC to AC output, the system achieves voltage matching without the power losses associated with multiple conversion stages, thereby reducing energy loss while maintaining required voltage output.
Solution Approach 2:
The patent maintains continuous resonant oscillation from the primary side through the transformer to the secondary side, eliminating interruptions from multiple conversion stages. This continuous resonant action preserves energy throughout the power conversion process, reducing power losses while maintaining the required AC voltage output for lamp driving.
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 reduces power consumption and costs by enabling soft switching with reduced switching losses and EMI emissions, while maintaining efficient operation of CCFL and LED lighting systems.
Implementation Method 1
driving an isolation transformer with a drive signal that exhibits high, low, and high impedance states, coupled via a capacitor
Implementation Method 2
driving an isolation transformer with a drive signal that exhibits high, low, and high impedance states
Data Source
AI summary
A driving circuitry arranged to pass a dead time over an isolation transformer, the driving circuitry constituted of: a three-state driver arranged to output a first signal, the first signal selectively at one of two complementary voltage levels and a high impedance state; a first capacitor, a first end of the first capacitor coupled to receive the first signal; and a first isolation transformer, a first end of a first winding of the first isolation transformer coupled to a second end of the first capacitor.