LED Lighting Device with Feedback and Feedforward PWM Control
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Solution Overview
Problem
Existing LED lighting devices require additional circuits to prevent flicker caused by input voltage fluctuations, which increase the size and power consumption of the circuit.
Innovation Solution
Implementing a feedback-controlled and feedforward-controlled system that adjusts the PWM signal based on output current deviations and input voltage fluctuations to maintain a constant current supply to the LED, eliminating the need for a separate flicker-preventing circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a voltage fluctuation absorbing circuit is added to prevent LED flicker, then the flicker is suppressed, but the circuit size increases
Solution Approach 1:
The patent combines the flicker suppression function with the existing output smoothing circuit by adding a transistor in parallel. This merging approach integrates the voltage fluctuation absorbing capability into the existing circuit structure rather than adding a completely separate circuit, thereby suppressing flicker while minimizing the increase in overall circuit size
Solution Approach 2:
The transistor-based voltage fluctuation absorbing circuit serves multiple functions: it absorbs voltage ripples, prevents LED flicker, and works in conjunction with the output smoothing circuit. This multi-functionality allows a single circuit element to address flicker suppression without requiring dedicated separate circuits for each function
2Reliability
If a voltage fluctuation absorbing circuit is added to prevent LED flicker, then the flicker is suppressed, but the power consumption increases
Solution Approach 1:
The transistor in the voltage fluctuation absorbing circuit is controlled through feedback mechanisms that monitor the output voltage and adjust the transistor's conduction accordingly. This feedback control ensures the transistor only activates when voltage fluctuations occur, preventing continuous power consumption while maintaining flicker suppression effectiveness
Solution Approach 2:
The circuit employs dynamic control of the transistor switching based on real-time voltage conditions. The transistor transitions between on and off states according to the presence of voltage ripples, making the power consumption dynamic rather than static. This dynamic operation suppresses flicker during fluctuations while minimizing power consumption during stable operation
3Reliability
If feedback control and feedforward control are implemented, then output current fluctuation is suppressed without additional circuits, but the control system complexity increases
Solution Approach 1:
The feedforward control component anticipates voltage fluctuations by monitoring the input voltage and proactively adjusts the PWM duty ratio before the fluctuations affect the output current. This preliminary action prevents output current variation without requiring complex reactive compensation circuits, as the control system prepares in advance for expected disturbances
Data Source
AI summary
An LED lighting device 2 according to this embodiment includes a lighting circuit that supplies a current to an LED, and a dimmer 7 that generates a PWM signal for controlling the supply of the current to the LED from the lighting circuit, in which the dimmer 7 feedback-controls the PWM signal that controls the supply of the current to the LED by comparing the output current to be output to the LED with a target current and feedforward-controls the PWM signal according to a fluctuation of an input voltage from a commercial power supply 1.