Dimmer Phase Detection Circuit Flicker Prevention
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Solution Overview
Problem
Conventional dimmers using triacs for phase control of AC power sources face issues with flicker and inappropriate switching due to variations in power source voltage from external power failures, leading to unpredictable dimming and light source flicker.
Innovation Solution
A dimmer system incorporating a phase detection circuit and control circuit that generates a trigger signal based on the rising edge of a synchronization signal, with the ability to stop generating the trigger signal when the time interval between subsequent rising edges is outside a predetermined range, ensuring stable conduction angle control and preventing flicker.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If phase control is performed using a triac with trigger signals based on synchronization signal rising timing, then the conduction angle of power source voltage can be controlled to dim the light source, but when the power source voltage varies due to instantaneous power failure, the rising timing of the synchronization signal changes, causing the trigger signal output timing to change and resulting in inappropriate triac switching and light source flicker
Solution Approach 1:
The control circuit monitors the time interval between consecutive rising edges of the synchronization signal and compares it against a predetermined reference range. When the interval falls within the normal range, trigger signals are generated for dimming control. When the interval exceeds the reference range indicating power failure, the control circuit stops generating trigger signals, preventing inappropriate triac switching and light flicker. This feedback mechanism ensures reliable operation under varying power conditions.
2Measurement precision
If the trigger signal is generated based on the rising timing of the synchronization signal, then the period of the trigger signal can correspond to the period of the power source voltage, but when the power source voltage varies, the output timing of the trigger signal changes from normal timing, causing the triac to not be appropriately turned on or off
Solution Approach 1:
The control circuit performs preliminary detection of the time interval between consecutive rising edges of the synchronization signal before generating trigger signals. By detecting and validating the timing interval in advance, the control circuit ensures that trigger signals are only generated when power conditions are normal. This preliminary action prevents synchronization errors and subsequent flicker before they can occur.
3Device complexity
If conventional phase control is implemented without monitoring power source voltage stability, then the dimming function can operate simply, but the triac continues to be turned on during subsequent half period when power source voltage is zero crossed, causing unexpected dimming and flicker
Solution Approach 1:
The control circuit continuously monitors the time interval between rising edges of the synchronization signal as feedback about power source stability. When the interval indicates normal operation, the control circuit generates trigger signals at appropriate times to ensure proper triac switching. When the interval indicates power failure, the control circuit stops generating trigger signals, preventing the triac from remaining incorrectly turned on and eliminating unexpected dimming and flicker.
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 effectively prevents light source flicker by maintaining stable dimming even during instantaneous power failures, ensuring consistent light output by adjusting the conduction angle of the power source voltage.
Implementation Method 1
a phase detection circuit for outputting a synchronization signal when a power source voltage from the external power source reaches a predetermined voltage
Implementation Method 2
a control circuit for generating a trigger signal which varies a conduction angle of the power source voltage that is supplied from the external power source to the lighting apparatus
Implementation Method 3
a switching element connected to a lighting apparatus using a solid-state light emitting element as a light source and an external power source
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
A dimmer includes: a switching element connected to a lighting apparatus using a light emitting element as a light source and an external power source, in series; a phase detection circuit for outputting a synchronization signal when a power source voltage from the external power source reaches a predetermined voltage; and a control circuit for generating a trigger signal which varies a conduction angle of the power source voltage supplied from the external power source to the lighting apparatus to switch on or off the switching element. The control circuit generates the trigger signal based on rising of the synchronization signal and stops generating the trigger signal when a rising interval of the synchronization signal is out of a reference range.