LED Drive Circuit Combinational Control for Flicker-Free Switching
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Solution Overview
Problem
LED products experience flickering when switching color temperature or brightness due to the slow discharge of output electrolytic capacitors, leading to a poor user experience, especially in high power factor applications.
Innovation Solution
A combinational circuit with a detection module and a drive and logic conversion module that generates a driving signal to control a discharge module, allowing for rapid discharge of the output electrolytic capacitor when the external switch is turned off, preventing residual energy from causing flickering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the output electrolytic capacitor is used to maintain stable voltage in the LED drive circuit, then the voltage stability is improved, but the discharge time becomes too slow causing flickering during switch transitions
Solution Approach 1:
The discharge path is segmented into two modes: normal operation mode where the capacitor maintains voltage stability, and rapid discharge mode where a dedicated discharge switch connects the capacitor to ground through a low-impedance path. This segmentation allows the capacitor to serve dual purposes without conflict.
Solution Approach 2:
The discharge resistance is made dynamic by introducing a control switch that can change the discharge path's impedance state. During normal operation, the discharge path is high-impedance (effectively open); during transition, it switches to low-impedance for rapid discharge. This dynamic adjustment resolves the contradiction between maintaining stability and enabling rapid discharge.
2Device complexity
If a traditional discharge path without control switch is used, then the circuit complexity is reduced, but the discharge speed is too slow causing visual stroboscopic phenomena
Solution Approach 1:
A control switch acts as an intermediary element between the electrolytic capacitor and the discharge path. This intermediary enables the discharge speed to be dynamically adjusted without fundamentally changing the circuit topology, thus limiting the increase in complexity while achieving rapid discharge capability.
Solution Approach 2:
The discharge path's resistance parameter is changed dynamically by controlling the switch state. The control circuit adjusts the switch's on/off state based on detection signals from the LED drive circuit's operational state, thereby changing the discharge resistance from high (normal operation) to low (rapid discharge) without adding complex discharge circuitry.
3Object-affected harmful factors
If the discharge module operates continuously to ensure rapid discharge, then the flickering is eliminated, but the energy loss increases
Solution Approach 1:
The discharge module operates periodically rather than continuously - it activates only during transition periods when the LED drive circuit switches between different LED groups. During normal operation, the discharge path remains inactive (high-impedance state), preventing unnecessary energy loss while maintaining the capability for rapid discharge when needed.
Solution Approach 2:
The control circuit uses feedback from detection signals that monitor the LED drive circuit's operational state to determine when rapid discharge is needed. This feedback mechanism ensures the discharge module operates only during necessary transition periods, avoiding continuous operation and associated energy losses while still effectively eliminating flickering during switching events.
Data Source
AI summary
The present disclosure provides a combinational circuit and a control circuit. The combinational circuit is applied to an LED drive circuit and includes a detection module and a drive and logic conversion module connected with the detection module. The detection module is configured to detect a state of an external switch, generate a detection signal according to the state of the external switch as detected, and send the detection signal to the drive and logic conversion module; and the drive and logic conversion module is configured to receive the detection signal from the detection module, generate a driving signal according to the detection signal, and drive an operation state of a discharge module for discharging an output electrolytic capacitor of the LED drive circuit by using a state of the driving signal.