Current Correction Circuit for Phase-Cutting Dimmer Resonance
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Solution Overview
Problem
In lighting systems with phase-cutting dimmers, resonances between the dimmer's inductor and the driver's filtering circuitry can cause the TRIAC to switch off prematurely, leading to flicker and audible humming due to repeated ignition, especially at low dim levels.
Innovation Solution
A current correction circuit with active current sink means, including a differentiator and voltage comparator, generates brief current pulses to maintain TRIAC conductivity and prevent resonant oscillations, ensuring stable current output without adapting the dimmer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If phase-cutting dimming is used to reduce light intensity, then power consumption is reduced, but resonances between the dimmer's inductor and driver's filtering circuitry cause the TRIAC to switch off prematurely, leading to flicker and audible humming
Solution Approach 1:
The patent applies preliminary anti-action by introducing a current correction circuit that proactively compensates for the harmful resonance effects before they can cause TRIAC switch-off. The circuit detects the resonance condition and applies counteracting current to maintain TRIAC conductivity, preventing the flicker and humming problems that would otherwise occur during phase-cutting dimming operation.
Solution Approach 2:
The current correction circuit acts as an intermediary between the phase-cutting dimmer and the LED driver. It mediates the interaction by detecting resonance conditions and injecting corrective current to maintain stable TRIAC operation, thereby enabling the safe use of phase-cutting dimming without the harmful effects of resonance-induced switch-off.
2Stability of the object's composition
If the driver's filtering circuitry is used to smooth current output, then current stability is improved, but resonances with the dimmer's inductor cause repeated TRIAC ignition and audible humming
Solution Approach 1:
The patent converts the harmful resonance effect into a beneficial one by using the same filtering circuitry that causes resonance as part of the solution. The current correction circuit utilizes the circuit's existing components and resonance characteristics to generate corrective action, transforming the problematic resonance into a mechanism that maintains TRIAC conductivity and eliminates the harmful effects.
3Illumination intensity
If deep dimming is implemented to achieve low light levels, then illumination intensity is reduced, but the TRIAC switches off prematurely due to resonance, causing flicker
Solution Approach 1:
The current correction circuit applies preliminary anti-action by detecting the conditions that lead to premature TRIAC switch-off during deep dimming and proactively compensating with corrective current. This prevents the flicker that would otherwise occur when the TRIAC switches off due to resonance, enabling reliable deep dimming operation.
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 reduces flicker and humming by maintaining TRIAC conductivity, eliminating refiring and oscillations, and allowing for deep dimming without disturbing the dimmer's operation.
Implementation Method 1
a differentiator or slope detector or edge detector (210) having an input coupled to the circuit input and having an output coupled to the first current source
Implementation Method 2
a voltage comparator (230) having an input coupled to the circuit input and having an output coupled to the second current source
Implementation Method 3
active current sink means for increasing the current drawn from the driver at times close to the margins of the TRIAC's conductive periods
Data Source
Figure 1A~1C
Figure 2~3A
Figure 3B
AI summary
A current correction circuit (200) has an input (201) and comprises: -a first controllable current source (220) having an input connected to the circuit input for drawing a first current (I 220 ) from said circuit input; -a differentiator (210) having an input coupled to the circuit input and having an output coupled to the first current source; and/or -a second controllable current source (240) having an input connected to the circuit input for drawing a second current (I 240 ) from said circuit input; -a voltage comparator (230) having a first input coupled to the circuit input (201), having a second input coupled to receive a reference signal (Vref), and having an output coupled to the second current source. The circuit is responsive to voltage changes by drawing first current pulses (221) from said circuit input, and/or to low voltages by drawing second current pulses (241) from said circuit input.