DC LED Control Circuit Dimming via PWM Feedback
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Solution Overview
Problem
Existing direct current light emitting device control circuits with dimming functions require multiple IC chips and degrade the power factor due to the use of TRIAC devices for adjusting brightness.
Innovation Solution
A direct current light emitting device control circuit with a novel dimming control mechanism that uses a power switch, switch control circuit, feedback circuit, and dimming circuit to adjust the output current, eliminating the need for TRIAC devices and improving power factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a TRIAC device is used to adjust brightness for dimming function, then the dimming function is achieved, but the power factor is degraded
Solution Approach 1:
The patent changes the control parameter from TRIAC phase-angle control to PWM duty cycle control. The PWM control circuit adjusts the duty cycle of the power switch based on feedback voltage, which directly controls the average current to the LED without degrading power factor. This parameter change resolves the contradiction by achieving dimming through a different control mechanism that doesn't disrupt the power factor.
2Ease of operation
If an AC-DC power regulator and LED driver circuit are used to control LED current, then the LED current control is achieved, but at least three IC chips are needed increasing cost
Solution Approach 1:
The patent merges the AC-DC power regulator and LED driver circuit into a single integrated control system. The feedback circuit generates a feedback voltage that is directly used by the PWM control circuit to regulate LED current. This consolidation eliminates the need for separate IC chips while maintaining effective LED current control, resolving the contradiction between ease of operation and device complexity.
3Adaptability or versatility
If a TRIAC device is used for dimming control, then brightness adjustment is achieved, but power consumption increases
Solution Approach 1:
The patent changes from TRIAC-based phase control to PWM-based duty cycle control. The PWM control switches the power transistor fully on or off, minimizing resistive losses. The duty cycle adjustment controls average power delivery without the continuous conduction losses inherent in TRIAC phase control, thereby reducing overall power consumption while maintaining brightness adjustment capability.
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 reduces power consumption and maintains a better power factor while allowing for adjustable brightness without the need for additional IC chips, enhancing the efficiency and cost-effectiveness of the dimming function.
Implementation Method 1
a feedback circuit generating a feedback signal according to a signal related to the output current
Implementation Method 2
a power switch; a switch control circuit controlling the power switch to convert an input voltage to an output current which is supplied to at least one direct current light emitting device
Implementation Method 3
at least one direct current light emitting device
Implementation Method 4
direct current light emitting device
Data Source
AI summary
The present invention discloses a direct current (DC) light emitting device control circuit with dimming function, and a method thereof, wherein the dimming function is provided in a feedback loop for feeding back a feedback signal from an output terminal to a power switch control circuit; the feedback signal relates to an output current supplied to the DC light emitting device. The present invention adjusts the feedback signal according to the desired brightness of the DC light emitting device. The present invention controls a power switch according to the adjusted feedback signal, such that the output current supplied to the DC light emitting device is adjusted, and accordingly the brightness of the DC light emitting device is adjusted below the full brightness.