Dimmer Control System for Fluorescent Lamps Using SCR and Charge Pump
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional dimmer control systems for fluorescent lamps face issues with frequent restarts and flickering due to energy shortages, and require complex additional circuit designs to adjust illumination levels, which complicates the control of AC power conversion to DC power needed for fluorescent lamps.
Innovation Solution
A dimmer control system comprising a SCR circuit, charge pump circuit, RC attenuator, control circuit, and half bridge driving circuit, which generates adjustment signals and DC power to control the illumination level of fluorescent lamps by maintaining SCR conduction and adjusting current flow through an external inductor, using a hysteretic comparator, subtractor, and voltage-controlled oscillator to manage turn-on angles and prevent restart issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional SCR circuit with bridge rectifier and capacitor is used to control fluorescent lamp illumination, then the illumination level can be adjusted, but the SCR leakage when turned off charges the capacitor and reduces voltage across capacitor C1, preventing the bi-directional diode from reaching turn-on voltage and causing frequent restarts and flickering
Solution Approach 1:
The patent introduces an intermediary capacitor C2 connected in parallel with capacitor C1 to serve as a voltage support element. When the bi-directional diode Db3 turns off, capacitor C2 supplies charge to maintain the voltage across C1 above the turn-on threshold, preventing SCR leakage from causing voltage drops that would trigger frequent restarts. This intermediary capacitor acts as a buffer to stabilize the triggering circuit voltage.
Solution Approach 2:
The patent applies beforehand cushioning by pre-charging capacitor C2 during the SCR conduction period so that it is ready to supply charge when the SCR turns off. This prior preparation ensures that the voltage across C1 is maintained above the turn-on voltage threshold, cushioning against the harmful effect of SCR leakage current that would otherwise cause voltage drops and trigger frequent restarts.
2Illumination intensity
If an extra control circuit is added to the electronic dimmer ballast to generate and pass dimming signals, then the illumination level can be controlled, but the circuit becomes complicated
Solution Approach 1:
The patent merges the dimming control function with the existing power supply circuit by utilizing the SCR triggering circuit and associated capacitors (C1 and C2) that are already present in the power supply architecture. The dimming control is achieved by adjusting the turn-on angle of the SCR through the existing bi-directional diode Db3 and resistor R1, eliminating the need for separate control circuits and reducing overall circuit complexity.
Solution Approach 2:
The patent makes the existing power supply components multi-functional by using capacitor C1 and C2 not only for power factor correction and voltage stabilization but also for dimming control through turn-on angle adjustment. The SCR and bi-directional diode circuit serves both power conversion and illumination control functions, reducing the need for dedicated control circuitry.
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 effectively controls the illumination level of fluorescent lamps by maintaining consistent operation and preventing frequent restarts, while simplifying the dimming process by integrating control signals within the power supply, thus enhancing the reliability and efficiency of dimmer control without reducing the dimming range.
Implementation Method 1
SCR is turned on and the incandescent lamp RL is illuminated. The incandescent lamp RL is also illuminated in the same manner during the negative half cycle of power PS sine wave.
Implementation Method 2
The charge pump circuit is coupled to the SCR control circuit, receiving a charge pump signal, a second signal from the utility power and an adjusted adjustment signal to rectify and generate a DC power signal as a DC power source for fluorescent lamp.
Implementation Method 3
The RC attenuator is also coupled to the SCR control circuit, attenuating the adjustment signal output from the SCR control circuit and generating an attenuated DC signal.
Implementation Method 4
The half bridge driving circuit is coupled to the charge pump circuit, the control circuit and the fluorescent lamp, receiving the first output signal, the second output signal and the DC power signal to generate the charge pump signal, such that a charge pump circuit is formed in the charge pump circuit to maintain conducting of the SCR. The half bridge driving circuit generates an illuminating signal by controlling the amount of current through an external inductor based on the first output signal, the second output signal and the DC power signal.
Data Source
AI summary
A system for controlling illumination of a fluorescent lamp includes a silicon controlled rectifier (SCR) control circuit receiving a first signal of a power source and generating an adjustment signal. A charge pump circuit receives a charge pump signal, a second signal of the power source and the adjustment signal to generate a direct current (DC) power signal. An RC attenuator attenuates the adjustment signal to generate an attenuated DC signal. A control circuit receives the attenuated DC signal and generates first and second output signals according to a first reference voltage, a second reference voltage and a power feedback signal of the fluorescent lamp. A half bridge driving circuit receives the first output signal, the second output signal and the DC power signal to generate an illuminating signal and the charge pump signal. The illumination of the fluorescent lamp is adjustable by the illuminating signal.