LED Driving Circuit Inrush Current Suppression
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Solution Overview
Problem
Conventional LED driving circuits face issues with sudden current surges due to failed LED strings, leading to reduced LED lifespan and increased line impedance when using PTC elements for protection, necessitating a cost-effective solution to suppress current impacts.
Innovation Solution
A driving apparatus and method featuring a cycle-by-cycle control unit that samples current instantaneous values and adjusts the output when exceeding a preset reference, using a sampling circuit and adjusting circuit to limit current peaks by adjusting the operating frequency or duty cycle, thereby reducing current impacts on semiconductor light-emitting devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protection circuit is connected in parallel with the LED string to short out the failed LED string, then the remained strings can continue operating, but a sudden current surge occurs when an LED string fails
Solution Approach 1:
The patent applies preliminary action by detecting LED string failures before they cause current surges. The control circuit continuously monitors the voltage across each LED string and identifies open-circuit failures early, allowing the system to switch to alternative strings proactively rather than reactively after a surge occurs.
Solution Approach 2:
The patent implements feedback by using a control circuit that continuously samples the voltage across each LED string and adjusts the driving current accordingly. When a failure is detected, the feedback mechanism immediately modifies the current distribution to prevent current surges and maintain stable operation of remaining strings.
2Object-affected harmful factors
If a PTC element is connected in series to the LED load to suppress current impact, then the current impact is reduced, but the line impedance increases causing higher loss in normal state
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the driving current parameters based on the operational status of LED strings. The control circuit modifies current magnitude and distribution in real-time according to detected failures, achieving current impact suppression without the continuous impedance increase associated with PTC elements.
3Reliability
If the feedback loop speed is increased to adjust inrush current in time, then the LED life is improved, but the device complexity increases
Solution Approach 1:
The patent extracts the essential control function from a complex high-speed feedback loop and implements a simplified detection and switching mechanism. By focusing on key parameters like voltage across each LED string and using predetermined switching logic, the system achieves reliable inrush current management without the complexity of sophisticated feedback loops.
Data Source
AI summary
The disclosure provides a driving apparatus and a method for driving a semiconductor light-emitting device assembly. The apparatus includes: a driving unit configured to drive the semiconductor light-emitting device assembly; and a cycle by cycle control unit. The cycle by cycle control unit may include: a sampling circuit configured to sample a current instantaneous value of the driving unit or the semiconductor light-emitting device assembly; and an adjusting circuit configured to adjust an output of the driving unit when the current instantaneous value sampled by the sampling circuit is larger than or equal to a preset reference value. The driving apparatus and method for driving the semiconductor light-emitting device assembly may effectively reduce an inrush current on the light-emitting devices and have a lower cost.