LED Tube Dimming Circuit Using Power Switch Timing
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Solution Overview
Problem
Existing LED lamp tubes lack dimming or lightness adjustment functionality, limiting user experience, and most control devices only utilize a power switch to regulate current through the LED source by changing the duty cycle of PWM signals.
Innovation Solution
A dimmable LED lamp with a driving circuit that includes a dimming controller and power conversion unit, where the dimming controller monitors switch states and supply voltage to output dynamic driving signals, adjusting current through the LED light source by changing the duty cycle of PWM signals, and a power conversion unit comprising a switch tube, autotransformer, and freewheeling diode to provide energy to the LED source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a power switch is used to control the LED lamp, then the lamp can be turned on and off, but the brightness cannot be adjusted
Solution Approach 1:
The system uses the power switch itself as the dimming control by detecting its on/off state and the power supply voltage level. The controller automatically adjusts brightness based on how long the switch has been off, eliminating the need for separate dimming controls and allowing brightness adjustment through simple switch operation
Solution Approach 2:
The system changes the duty cycle parameter of the PWM signal based on the power supply voltage level. When voltage is between first and second thresholds, a first duty cycle is used; when voltage is between second and third thresholds, a second duty cycle is used, thereby adjusting brightness through parameter modification
2Illumination intensity
If traditional dimming circuits are added to LED lamps, then brightness adjustment is achieved, but the circuit complexity increases
Solution Approach 1:
The power switch serves dual functions: traditional on/off control and brightness adjustment. The same switch operation that controls power delivery also triggers dimming sequences, making the switch universal for both functions and eliminating the need for separate dimming circuitry
Solution Approach 2:
The controller acts as an intermediary between the power switch and the LED driver. It monitors the switch state and power supply voltage, then generates appropriate PWM signals to achieve dimming without requiring additional physical dimming components in the circuit
3Loss of energy
If the switch is turned off to save energy, then power consumption decreases, but the lamp cannot be quickly restored to original brightness
Solution Approach 1:
The system prepares for quick brightness restoration by monitoring the power supply voltage level during the off state. When voltage is within the second threshold range, the system pre-conditions the circuit so that upon switch-on, the LED can quickly reach maximum brightness without gradual ramp-up delays
Data Source
AI summary
The present invention discloses an LED lamp tube, comprising a driving circuit controlled by a switch when used, the driving circuit comprises: a dimming controller having a switch state monitoring port and a power supply port, and the power supply voltage is gradually formed after the switch is disconnected. When the switch is turned on again, if the supply voltage is between the first set value and the second set value, the output of the drive signal is the same as the signal when the switch is turned off, so that the current flowing through the LED light source remains unchanged. If the supply voltage is lower than the second set value, it outputs a dynamically changing driving signal, so that the current flowing through the LED light source gradually changes from the first extreme value to the second extreme value; and the power conversion unit is configured to receive the drive signal and provide energy to the LED light source. The LED lamp of the present invention can achieve dimming function by only operating the power switch, and does not need to modify the original circuit, and is easy to implement.