LED Driver Delay Circuit for PWM Dimming Overshoot Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing light-emitting device driving systems experience overshoot in current due to abrupt switching of the error amplifier from a non-operating to an operating state, leading to inefficiencies and potential damage, especially when using PWM dimming signals.
Innovation Solution
Incorporating a delay circuit within the LED driver IC to delay the switching of the error amplifier from a non-operating to an operating state, allowing the output capacitor to charge fully before initiating operation, thereby suppressing overshoot in the current flowing through the light-emitting diodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the error amplifier switches abruptly from non-operating to operating state to respond to PWM dimming signals, then the light-emitting device can quickly adjust brightness, but current overshoot occurs causing instability and potential damage
Solution Approach 1:
The delay circuit is activated in advance when the PWM dimming signal transitions to the high level, delaying the switching of the error amplifier from non-operating to operating state. This preliminary action allows the output capacitor to charge fully before the error amplifier begins operation, preventing current overshoot while maintaining quick response capability.
2Productivity
If the error amplifier switches immediately upon receiving PWM dimming signal, then brightness adjustment is rapid, but voltage changes abruptly causing current spikes
Solution Approach 1:
The delay circuit provides preliminary anti-action by delaying the error amplifier's switching action, which prevents the harmful current spikes that would otherwise occur during abrupt transitions. This counter-measure is applied in advance to offset the potential harm before it can manifest.
3Loss of time
If the error amplifier operates immediately without delay, then the system responds quickly to dimming commands, but the output capacitor cannot charge fully leading to overshoot
Solution Approach 1:
The delay circuit is configured to activate the error amplifier only after the output capacitor has had sufficient time to charge fully. This preliminary timing action ensures that when the error amplifier begins operation, the capacitor is ready, preventing current overshoot while minimizing the delay to the essential minimum required for stable operation.
Data Source
AI summary
A light-emitting element driving device includes an error amplifier configured to output a voltage corresponding to the difference between a voltage corresponding to the current flowing through a light-emitting element and a reference voltage, and to switch between an operating state and a non-operating state according to a control signal; a driver configured to drive, based on the output voltage of the error amplifier, a switching element in a voltage feeder configured to feed a voltage to the light-emitting element; and a suppressor configured, when the error amplifier switches from the non-operating state to the operating state, to suppress a rise in the output voltage of the error amplifier.