LED Lighting Apparatus Feedback Circuit for Current Peak Reduction
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Solution Overview
Problem
Conventional LED lighting devices using double pulse width modulation (PWM) control subject LEDs to stress due to current peaks when switched off, reducing their lifespan and causing perceivable flicker, which limits the frequency of the low-frequency PWM signal.
Innovation Solution
A LED lighting apparatus with a feedback circuit that maintains a non-zero current through LEDs by adjusting the duty-cycle of high-frequency PWM control, ensuring the LEDs remain powered and reducing current peaks through a Buck configuration and a feedback circuit with two impedance states, allowing for continuous operation without cutting off the LEDs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If double PWM control is used to regulate LED intensity, then lighting intensity can be controlled according to user commands, but current peaks occur when LEDs are cut off causing stress and reducing lifespan
Solution Approach 1:
The patent applies continuity of useful action by ensuring the LED current never drops to zero through the feedback circuit that activates the switch when current falls below a threshold. This continuous operation eliminates the current peaks and stress caused by conventional PWM cutting off LEDs, while maintaining intensity control functionality.
Solution Approach 2:
The patent implements feedback by monitoring the actual LED current and using this information to control the switch activation. The feedback circuit compares the current with a reference threshold and adjusts switch operation accordingly, preventing current peaks while maintaining proper intensity regulation.
2Object-affected harmful factors
If low-frequency PWM signal frequency is reduced to minimize flicker, then perceivable flicker is reduced, but current peaks become more pronounced and LED stress increases
Solution Approach 1:
The feedback circuit ensures continuous LED operation by activating the switch when current drops below threshold, eliminating the on-off cycles that cause both flicker and current peaks. This resolves the contradiction by making the lighting continuous without introducing new harmful effects.
Solution Approach 2:
The patent converts the potentially harmful effect of low-frequency PWM into a benefit by using the feedback mechanism to maintain continuous operation. The low-frequency signal still provides intensity control, but the feedback circuit prevents the harmful current peaks and flicker that would otherwise occur.
3Illumination intensity
If switch is deactivated during inactive phase of low-frequency PWM, then lighting intensity is reduced, but current peaks occur during subsequent cycle causing LED stress
Solution Approach 1:
The feedback circuit maintains continuous LED operation by detecting when current falls below threshold and activating the switch accordingly. This eliminates the complete shutdown and subsequent current peak problems, while still allowing intensity control through duty-cycle adjustment.
Solution Approach 2:
The patent applies dynamics by making the switch operation adaptive rather than fixed. The feedback circuit dynamically adjusts switch activation based on real-time current conditions, allowing the system to transition smoothly between different operating states without creating harmful current peaks.
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
Extends the lifespan of LEDs by preventing current peaks and maintaining continuous operation, while minimizing perceivable flicker by adjusting the duty-cycle based on feedback signals, thus enhancing the reliability and longevity of the lighting system.
Implementation Method 1
An inductor, connected between the switch and the LED lighting elements, is charged when the switch is closed and is discharged through the LED lighting elements and a recirculation diode when the switch is open.
Implementation Method 2
discharged through the LED lighting elements and a recirculation diode when the switch is open
Data Source
Figure 1~2
Figure 3~4
AI summary
A LED lighting apparatus includes at least one LED lighting element (3,4), a control unit (5) and a switching converter (7), for supplying the LED lighting element (3,4). A feedback circuit (8) is connected between the LED lighting element (3,4) and a ground line (13) and co-operates with the switching converter (7) for determining a LED current (IL) through LED lighting element (3,4). The feedback circuit (8) has a first impedance (R1) in a first state, to which a non-zero first regulation value (IL1) of the LED current (IL) corresponds, and a second impedance (R1//R2) in a second state, to which a non-zero second regulation value (IL2) of the LED current (IL) corresponds. The control unit (5) is configured to cyclically switch the feedback circuit (8) between the first state and the second state with a controllable duty-cycle.