Discharge Lamp Control Circuit for Flicker Prevention
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Solution Overview
Problem
Conventional discharge lamp lighting control apparatuses experience flicker phenomena due to fluctuations in lamp voltage, leading to unstable lamp current and potential damage from excessive power output, especially during the transition from constant-current to constant-power control modes.
Innovation Solution
A control circuit that adjusts the current command value to maintain constant-current control even in stable lamp states, using a smaller second current command value when the lamp voltage stabilizes, preventing flicker and reducing power supply capacity needs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If constant-power control is performed when lamp voltage rises to reach rated power, then output power of power supply portion does not exceed rated value, but lamp current decreases causing brightness changes and flicker phenomenon
Solution Approach 1:
The control apparatus dynamically switches between constant-current control and constant-power control modes based on the lamp voltage rise rate. When the lamp voltage stabilizes (low rise rate), constant-current control maintains stable brightness. When voltage rises rapidly, constant-power control prevents excessive power output. This dynamic mode switching resolves the contradiction by adapting the control strategy to the operational state.
Solution Approach 2:
The control apparatus changes the control parameter from power-based control to current-based control when the lamp enters stable operation. By detecting the lamp voltage rise rate and switching the control mode accordingly, the system changes the controlled parameter to eliminate flicker while maintaining power safety limits.
2Reliability
If constant-current control is performed continuously from initial lighting stage, then brightness remains stable, but output power of power supply portion may exceed rated value when lamp voltage is high
Solution Approach 1:
The control apparatus uses dynamic mode switching based on the lamp voltage rise rate. During initial lighting with high voltage rise, constant-power control limits output power. When the lamp stabilizes and voltage rise rate decreases, constant-current control takes over to maintain brightness stability. This resolves the contradiction by applying the appropriate control mode at each operational stage.
Solution Approach 2:
The control apparatus performs preliminary constant-power control during the initial lighting stage to prevent excessive power output before the lamp stabilizes. This preliminary action protects the power supply and lamp from overload, then transitions to constant-current control for stable operation.
3Power
If control mode switches from constant-current to constant-power when lamp voltage rises, then power output is limited, but flicker phenomenon occurs due to lamp current changes
Solution Approach 1:
The control apparatus dynamically determines the switching point between control modes based on the lamp voltage rise rate. By switching to constant-current control when the rise rate becomes low (stable operation), the system eliminates the flicker caused by constant-power control while maintaining power limits during transient states through earlier constant-power control.
Solution Approach 2:
The control apparatus uses feedback from the lamp voltage rise rate detection to determine control mode switching. By continuously monitoring the voltage change and adjusting the control mode accordingly, the system feedback-controlled to eliminate flicker while maintaining power safety.
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
Prevents flicker generation and maintains stable lamp operation without increasing power supply capacity, ensuring the lamp operates within rated power limits and extends its service life.
Implementation Method 1
after the lamp is turned on an arc discharge occurs between the electrodes when a breakdown takes place caused by an igniter or the like
Implementation Method 2
a control circuit that performs a constant-current control of the lamp current and outputs a current command value to perform the constant-current control to the inverter circuit
Data Source
AI summary
Realizing a constant-current control even in a stable state of a lamp without increasing a rated output of a power supply. In a stable state of the lamp in which a change value of a lamp voltage after a discharge lamp is turned on becomes less than a certain value, when the lamp voltage rises, a discharge lamp lighting control apparatus changes a current command value to perform a constant-current control. This change is a change from a first current command value at the time when the discharge lamp is turned on to a second current command value that is smaller than the former by a predetermined value. Using this second current command value, the constant-current control is performed. Even after that, the second current command value is changed to a smaller value every time the lamp voltage rises, and the constant-current control is performed using the second current command value.