LED Driver Short Circuit Detection Before Dimming
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Solution Overview
Problem
LED emitting devices lack a method to sense short circuits between the LED channel and external components before dimming operations, leading to potential damage from overcurrents during dimming.
Innovation Solution
An LED emitting device with a short circuit sense protector, power controller, and comparators to detect a predetermined threshold voltage reduction, stopping power supply and controlling switches to prevent damage before dimming, and maintaining normal operation when no short circuit is detected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If no short circuit sensing method is implemented before dimming operation, then the device structure remains simple, but the LED channel may be damaged by overcurrent during dimming operation
Solution Approach 1:
The patent implements preliminary short circuit detection before the dimming operation begins. The sensing circuit checks for short circuits in advance by monitoring voltage levels during a predetermined period after power supply activation, preventing overcurrent damage before it can occur during dimming.
Solution Approach 2:
The patent introduces a sensing circuit as an intermediary component that mediates between the power supply and the LED channel. This circuit includes voltage detection units and control logic that act as intermediaries to detect short circuits and control the power supply switching element accordingly.
2Ease of manufacture
If short circuit detection is performed during dimming operation, then the sensing method is simpler, but overcurrent has already damaged the LED channel by then
Solution Approach 1:
The patent performs short circuit detection during a predetermined period immediately after power supply activation, before the dimming operation starts. This timing ensures that any short circuits are detected and addressed before overcurrent conditions can develop and damage the LED channel during subsequent dimming operations.
3Reliability
If the power supply is continuously monitored for short circuits, then the LED channel is fully protected, but the device complexity and power consumption increase
Solution Approach 1:
The patent implements periodic short circuit detection during a predetermined period after power supply activation rather than continuous monitoring. The sensing circuit operates intermittently, checking for short circuits at specific intervals during the initialization phase, which reduces power consumption while maintaining adequate protection.
Solution Approach 2:
The short circuit detection is concentrated in a predetermined initial period after power supply activation, before normal operation begins. This preliminary detection phase ensures protection is established upfront without requiring continuous monitoring throughout operation, thereby reducing overall power consumption.
Data Source
AI summary
The present invention relates to an LED emitting device and a driving method thereof. The LED emitting device receives an input voltage and supplies a power supply voltage needed for operating an LED channel according to a switching operation of a power switch. The LED emitting device controls the power supply and also controls a load switch between the LED channel and an output voltage. The LED emitting device determines the LED channel to be short circuited when the output voltage is reduced to a predetermined threshold voltage during a predetermined short circuit sense period starting from the time when the output voltage reaches a regulated voltage before the LED channel is dimmed. During the short circuit sense period, the power supply is stopped and the load switch is turned on.