LED Driver Compensation Memory for Fast PWM Dimming Response
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Solution Overview
Problem
Existing LED drivers experience delays and inaccuracies in brightness control due to the control loop adjusting to different PWM states, causing slow response times when switching between load levels.
Innovation Solution
A driver with a current control loop that saves and re-applies an electrical value, such as a capacitor voltage, to quickly adjust between load states, using two compensation circuits to maintain stable current regulation during PWM dimming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If PWM control is used to extend dimming range, then dimming range is improved, but control loop settling time increases causing delays and brightness inaccuracies
Solution Approach 1:
The patent applies preliminary action by pre-storing the compensation electrical value (capacitor voltage) before PWM dimming begins. When the load changes during PWM operation, the stored value is immediately re-applied to the control loop, bypassing the slow natural settling process. This pre-storation of the electrical value enables instant recovery of accurate current regulation without waiting for the control loop to naturally settle.
2Extent of automation
If the control loop adjusts to different PWM states, then PWM dimming control is achieved, but brightness level accuracy deteriorates due to settling delays
Solution Approach 1:
The patent applies copying by creating a stored copy of the compensation electrical value (the capacitor voltage) before PWM dimming operates. This copied value represents the optimal compensation state for accurate current regulation. When PWM operation causes brightness inaccuracies, the control loop retrieves this pre-stored copy and re-applies it, instantly restoring accurate brightness control without relying on slow natural settling.
3Device complexity
If a single compensation circuit is used in the control loop, then circuit simplicity is maintained, but response speed to load changes is insufficient
Solution Approach 1:
The patent applies dynamics by making the compensation circuit configurable rather than fixed. The system can switch between different compensation configurations (different electrical values) depending on the operating state. Specifically, the compensation circuit can be reconfigured by re-applying the pre-stored electrical value when load changes occur during PWM dimming, enabling the circuit to adapt dynamically to different operating conditions and achieve fast response speed without increasing structural complexity.
Data Source
AI summary
A driver has a current control loop for regulating an output current, the current control loop having a controllable configuration including an electrical value with influences the conversion function of the converter. An adjusting circuit is provided to selectively deliver or not deliver output current of the converter to the load and effectively adjust a load as seen by the driver between a first level and a second level. This adjustment for example enables PWM control of the output current, in addition to the output current regulation implemented by the current control loop. The electrical value of the current control loop is saved before the adjusting circuit changes the load as seen by the driver from the first level to the second level and the saved electrical value is reapplied to the current control loop, when the adjusting circuit changes the load as seen by the driver back from the second level to the first level. A response time of the current control loop when controlling the converter to output the desired output current is reduced. The electrical value is a voltage of a capacitor in a compensation circuit of an error amplifier of the current control loop.