LED Driver Over-Shoot Detection Circuit
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Solution Overview
Problem
Conventional LED driver systems experience voltage spikes after soft-start, leading to potential damage due to delayed discharging of the compensating capacitor, which can trigger over-voltage or over-current protection, especially under light loads.
Innovation Solution
An LED driver system with an over-shoot detecting circuit and logic circuit that generates a switching signal to control the main switch, preventing voltage spikes by comparing the load current with a second reference signal and adjusting the switching signal accordingly to manage the output voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If soft-start technology is applied by charging a compensating capacitor, then voltage across LED device rises gently during starting, but after soft-start completion the capacitor discharges slowly causing voltage spike and potential damage
Solution Approach 1:
The patent applies preliminary action by detecting the over-shoot condition before it causes damage. The over-shoot detecting circuit monitors the compensating signal and generates an over-shoot signal when voltage exceeds the safe threshold, allowing the system to take preventive action (stopping capacitor charging) before the voltage spike can damage the LED devices or trigger protection mechanisms.
Solution Approach 2:
The patent implements feedback by using the over-shoot detecting circuit to continuously monitor the compensating signal voltage and provide feedback to the control logic. When the feedback signal indicates over-shoot condition, the logic circuit adjusts the switching signal to stop charging the compensating capacitor, thereby regulating the voltage and preventing damage. This closed-loop feedback mechanism ensures voltage stability while eliminating the harmful voltage spike after soft-start.
2Speed
If compensating capacitor is used to generate compensating signal, then voltage rises gently during starting, but voltage spike occurs after starting completion due to delayed discharging
Solution Approach 1:
The over-shoot detecting circuit performs preliminary detection of the voltage condition before damage occurs. By monitoring the compensating signal and generating an over-shoot signal when voltage exceeds the threshold, the system can preemptively stop the charging process, preventing the voltage spike from developing into a harmful level that could damage LED devices.
Solution Approach 2:
The patent applies preliminary anti-action by introducing a counteracting mechanism that stops the charging of the compensating capacitor when over-shoot is detected. The over-shoot signal triggers the logic circuit to adjust the switching signal, which counteracts the continued charging process and prevents the voltage from rising to dangerous levels, thereby eliminating the harmful voltage spike effect.
Data Source
AI summary
A LED driver system includes a LED converter converting an input voltage to an output voltage to drive a LED load via a main switch; a sensing circuit generating a feedback signal on the output terminal according to a load current through the LED load; an over-shoot detecting circuit generating an over-shoot signal according to the load current and a second reference signal; a logic circuit generating a switching signal according to a control signal and the over-shoot signal to control the main switch. The control signal is generated according to the feedback signal and a first reference signal, and the second reference signal is larger than the first reference signal.