Trailing-Edge Light Modulating Circuit for Surge Current Suppression
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Solution Overview
Problem
Existing light bulb dimming circuits face issues with large surge current spikes in capacitive impedance lamps and require complex installations with additional wires, limiting their applicability and increasing costs.
Innovation Solution
A single pole two-wire system phase control trailing edge light modulating circuit using a full-bridge rectification circuit, power supply circuit, light-modulating control circuit, and active switch, which converts AC supply to stable DC voltage and controls the conduction phase angle of the active switch using a retriggerable dual monostable IC and voltage detection circuit, allowing for simple installation and wide application range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If leading-edge light bulb dimming circuit uses triad to control phase of supply voltage, then dimming control is achieved, but large surge current spikes are produced
Solution Approach 1:
The patent inverts the conventional leading-edge phase control approach by implementing trailing-edge phase control. Instead of controlling the phase at the beginning of the AC cycle (leading-edge), the circuit controls the phase at the end of the AC cycle (trailing-edge). This inversion eliminates surge current spikes because the triac turns off at the zero-crossing point of the AC waveform, allowing current to decay naturally without abrupt interruption that causes spikes.
2Ease of operation
If trailing-edge light bulb dimmer uses 2 input and 2 output wires (4 wires) system, then phase control is achieved, but installation becomes more complicated
Solution Approach 1:
The patent merges the neutral wire connection into the existing two-wire system by utilizing the neutral wire that is already present in standard electrical outlets. The circuit combines the hot wire and neutral wire connections to provide both power input and control signal paths, eliminating the need for separate control wires. This merging approach maintains full phase control functionality while reducing installation complexity to match standard two-wire configurations.
3Device complexity
If existing two-wire system trailing edge dimmer connects triggering circuit and power supply circuit together, then installation is simplified, but voltage level changes affect dimming adjustment
Solution Approach 1:
The patent segments the circuit into independent functional modules: the power supply circuit and the triggering circuit are separated and operated independently. The power supply circuit processes the AC input to generate stable DC voltages for controlling the triac, while the triggering circuit generates precise phase-control signals based on user input. This segmentation allows each circuit to be optimized for its specific function without mutual interference, maintaining both installation simplicity and dimming adjustment precision.
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 enables simple installation with only two wires, supports both resistive and capacitive load lamps, and maintains independence between the triggering and power supply circuits, providing effective dimming control without mutual restrictions.
Implementation Method 1
a full-bridge rectification circuit, adapted to convert an AC electrical supply into electrical supply of positive half cycle of a sine wave
Implementation Method 2
the power supply circuit is adapted to provide a stable DC working voltage to the light modulating control circuit and to the active switch in a linear voltage manner
Data Source
Figure 1~2
AI summary
A single pole (two-wire system) phase control trailing edge light modulating circuit, which comprises: a full-bridge rectification circuit (1), a power supply circuit (2), a light modulating control circuit (3), and a voltage detection circuit (4). The light modulating circuit (3), utilizes a CMOS chip as the control circuit, controls the field effect transistor (Ql) by detecting specific voltage level to perform a trailing edge phase control action for modulating light output of resistive and/or capacitive loading light bulbs, e.g. LED light bulbs. The light modulating circuit (3) connects to various lighting loads in series. In addition, the triggering circuit and the power supply circuit (2) are independent to avoid mutual restrictions to each other that might affect the adjustment of the maximum conduction phase angle.