Dimming Device Using Composite Harmonic Inverter Waveforms
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Solution Overview
Problem
Existing dimming devices using rectangular or trapezoidal wave signals generate harmonic noise, leading to reduced marketability and increased cost and size due to the need for noise filters.
Innovation Solution
A dimming device and method that uses a DC/AC inverter driven by an opening and closing control signal with overlapping harmonic components of a fundamental sine wave to generate arc-shaped peak and bottom regions, reducing steep waveform rises and preventing noise without additional filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a rectangular wave or trapezoidal wave is used to drive the liquid crystal dimming element, then the dimming control is simple and direct, but harmonic noise is generated reducing marketability and requiring additional noise filters that increase cost and size
Solution Approach 1:
The patent changes the waveform parameters from rectangular or trapezoidal waves to a composite wave formed by overlapping multiple harmonic components (sine wave + 3rd harmonic + 5th harmonic). This parameter change eliminates the steep waveform rise that causes harmonic noise while maintaining effective dimming control capability
Solution Approach 2:
The patent converts the harmful harmonic components into a beneficial solution by deliberately adding controlled harmonic components to the drive signal. Instead of filtering out harmonics, the invention uses specific harmonic combinations to create a waveform that reduces noise generation while maintaining dimming effectiveness
2Object-generated harmful factors
If a noise filter is provided to reduce harmonic noise, then the noise level is reduced, but the cost and size of the dimming device are increased
Solution Approach 1:
Instead of using a noise filter to remove harmful harmonics, the patent converts the approach by deliberately constructing the drive signal with specific harmonic components that inherently reduce noise generation. This eliminates the need for additional filtering hardware, reducing both cost and device size
Solution Approach 2:
The patent extracts and eliminates the need for noise filtering hardware by addressing the root cause of noise through waveform design. The harmful noise generation mechanism is removed by changing the drive signal characteristics rather than adding filtering components
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 solution reduces harmonic noise, allows for improved dimming quality without flickering, and decreases power consumption by optimizing the dimming rate, while using less expensive switching elements.
Implementation Method 1
a DC/AC inverter configured to convert a direct-current voltage into an alternating-current voltage requiring a predetermined period and amplitude
Implementation Method 2
a liquid crystal dimming element whose transmittance of parallel lines is 100% or more
Data Source
AI summary
A dimming device for controlling a dimming rate of a dimming member includes a DC/AC inverter to convert a direct-current voltage into an alternating-current voltage requiring a predetermined period and amplitude; and an inverter drive unit to drive the DC/AC inverter based on an opening and closing control signal. The inverter drive unit includes a command value generation unit to generate an opening and closing command value for controlling an opening and closing state of a switching element provided in the DC/AC inverter.