LED Driver Control Circuit Shunt Dimming Delay
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Solution Overview
Problem
Conventional PWM dimming for LED light emitting elements faces limitations in dimming accuracy due to slow output current changes in response to PWM signal transitions, and shunt PWM dimming results in energy loss and low system efficiency.
Innovation Solution
A control circuit for a light emitting element driver that includes a power converter and a shunt switch, where the control circuit provides a shunt switch control signal to turn off the shunt switch after a first delay time and turn it on after a second delay time, based on the dimming signal transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional PWM dimming is used to control LED brightness, then the control circuit can adjust the average current, but the dimming accuracy is limited due to slow output current response
Solution Approach 1:
The control circuit predicts the required output current based on the dimming signal before the actual dimming transition occurs. By calculating the expected current in advance and preparing the appropriate control signals, the system compensates for the inherent delay in power converter response, thereby improving dimming accuracy without requiring faster physical response from the hardware.
2Measurement precision
If shunt PWM dimming is used to improve dimming accuracy, then the average current can be controlled more precisely, but energy loss increases and system efficiency decreases
Solution Approach 1:
The invention extracts and removes the shunt switch component from the dimming control system. Instead of using a shunt switch to bypass excess current for dimming control, the system directly controls the power converter's output current through predictive control algorithms. This elimination of the shunt switch pathway prevents the energy loss that would otherwise occur through the shunt path while maintaining precise dimming control.
Solution Approach 2:
The invention converts the harmful effect of slow power converter response into a benefit by using predictive control. The system anticipates the response delay and adjusts control signals in advance, transforming what was previously a source of dimming inaccuracy into an opportunity for compensated control. This approach eliminates the need for energy-wasting shunt dimming while achieving accurate brightness control.
3Adaptability or versatility
If the shunt switch is used to bypass output current for dimming control, then dimming range can be extended, but system efficiency is reduced
Solution Approach 1:
The control circuit removes the shunt switch mechanism from the system and replaces it with direct power converter control. This extraction eliminates the parallel current path that caused efficiency losses while preserving the ability to achieve wide dimming ranges through predictive current control and appropriate PWM signal generation.
Solution Approach 2:
The system achieves extended dimming range by dynamically adjusting control parameters including PWM duty cycle, switching frequency, and predictive control timing. By varying these parameters adaptively, the system can control LED brightness across a wide range while maintaining high efficiency, replacing the need for shunt-based dimming with parameter-optimized direct control.
Data Source
AI summary
A control circuit for a light emitting element driver with a power converter and a shunt switch is provided. The control circuit includes a delay terminal, a dimming terminal, a control terminal and a driving terminal. The delay terminal receives a reference signal. The dimming terminal receives a dimming signal. The dimming signal has a first state and a second state. The control terminal provides a control signal to control the power converter. The driving terminal provides a shunt switch control signal to the shunt switch, to turn off the shunt switch after a first delay time from a time when the dimming signal is switched from the first state to the second state, and to turn on the shunt switch after a second delay time from a time when the dimming signal is switched from the second state to the first state.