Dimmer Control Circuit Stabilizes LED Operation
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Solution Overview
Problem
Phase cut dimmers used in LED illumination systems experience flickering issues due to transient voltages and oscillating currents when turning on, causing the dimmer to turn off immediately and resulting in unstable LED lamp operation.
Innovation Solution
A dimmer control circuit and method that provides compensation current greater than the holding current of the dimmer when specific voltage conditions are met, ensuring stable operation by using a rectifier circuit, input voltage detecting circuit, processor, and constant current circuitry to manage the compensation current based on preset conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the full-wave voltage is divided by sample resistors R4 and R5, then the voltage detection is achieved, but when the full-wave voltage is in higher level range, the FET Q1 remains turned off and no current flows through the loop
Solution Approach 1:
The patent introduces a compensation current source as an intermediary element that provides additional current through resistor R2 to ensure the voltage drop reaches the transistor Q2 turn-on threshold. This mediator compensates for the insufficient holding current caused by the voltage division network, enabling reliable dimmer turn-on while maintaining accurate voltage detection through R4 and R5.
2Ease of operation
If the transistor Q2 turns on when voltage on R5 reaches threshold, then the FET Q1 turns off, but this causes large transient voltage and ringing when dimmer is turned on
Solution Approach 1:
The patent applies preliminary anti-action by introducing a compensation current that opposes the harmful effect of insufficient holding current. The compensation current is activated before the dimmer turn-on issue occurs, ensuring the total current through R2 is sufficient to turn on transistor Q2 at the correct moment, thereby preventing the harmful transient voltage and ringing that would otherwise occur.
Solution Approach 2:
The patent employs feedback control where the voltage drop across resistor R2 is continuously monitored by transistor Q2, which adjusts its conduction state based on the current level. This feedback mechanism ensures that the FET Q1 is turned off at the appropriate moment when the holding current is sufficient, preventing excessive transient voltage and ringing while maintaining stable operation.
3Reliability
If the holding current is insufficient, then the dimmer turns off immediately after being turned on, but increasing the current requires higher power consumption
Solution Approach 1:
The patent applies partial action by providing compensation current only during the specific condition when holding current is insufficient (during dimmer turn-on phase). The compensation current source is activated selectively based on the operating conditions, providing just enough additional current to ensure reliable turn-on without continuously consuming excess power during normal 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 prevents disconnection of the dimmer and flickering of the light source by maintaining the dimmer in a conducting state during power transitions, ensuring stable LED lamp operation.
Implementation Method 1
a rectifier circuitry, coupled to an output terminal of the dimmer and configured to rectify the output voltage of the dimmer to output a rectified voltage
Implementation Method 2
a constant current circuitry, provided with a control terminal coupled to an output terminal of the processor and an output terminal coupled to the rectifier circuitry, and configured to output or stop outputting a preset current to the rectifier circuitry in response to the control signal
Data Source
AI summary
A dimmer control circuit for controlling a phase cut dimmer includes: a rectifier circuitry, configured to rectify the output voltage of the phase cut dimmer to output a rectified voltage; an input voltage detecting circuitry, configured to output a detected voltage according to the rectified voltage; a processor, configured to output a control signal when the detected voltage meets a preset condition; and a constant current circuitry, configured to output or stop outputting a preset current to the rectifier circuitry in response to the control signal; wherein the preset current has a value greater than a holding current of the phase cut dimmer.