LED Driver Circuit Residual Current Bypass and Compensation
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Solution Overview
Problem
Light emitting devices experience residual current leakage due to temperature-dependent semiconductor switches, leading to partial brightness when turned off or dimmed, affecting the on/off illumination ratio and color accuracy in color-mixed applications.
Innovation Solution
A light emitting driver circuit with a bypass circuit and logic control to divert residual current away from the device when switched off, or a sense circuit to measure and compensate for leakage current by adjusting the dimming signal, ensuring complete shutdown and accurate color output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a semiconductor switch is used to control the light emitting device, then the device can be turned on and off, but residual leakage current increases with temperature causing partial brightness when the device should be dark
Solution Approach 1:
A bypass circuit is introduced as an intermediary component that provides an alternative current path. When the main switch is turned off, the bypass circuit actively conducts the residual leakage current away from the light emitting device, preventing it from causing partial brightness while the temperature-dependent leakage continues to exist in the switch.
Solution Approach 2:
The harmful residual leakage current is extracted from the light emitting device's current path by directing it through the bypass circuit. This separates the leakage current from the device that should remain dark, effectively removing the harmful effect without requiring the switch to be perfectly off.
2Reliability
If the driver circuit is made more complex to compensate for leakage current, then the on/off illumination ratio improves, but the device complexity increases
Solution Approach 1:
The driver circuit is segmented into distinct functional blocks: a main switch for normal operation, a bypass circuit for handling leakage current, and a control circuit for managing both paths. This segmentation allows each component to perform its specific function efficiently without requiring the entire circuit to be overly complex.
Solution Approach 2:
The bypass circuit is designed to serve multiple purposes: it handles residual leakage current during normal operation, provides a path for current during switching transitions, and can be controlled to affect the dimming characteristics. This multi-functionality reduces the need for separate dedicated components for each function.
Data Source
AI summary
A light emitting driver circuit, system, and method are provided. The driver circuit system and method can be implemented in various ways. An embodiment includes a bypass circuit which diverts current from the LEDs whenever a switch coupled to the LEDs incurs residual current when turned off. In an additional or alternative embodiment, the residual current can be sensed and the amount of residual current used to trigger fetching of a compensation value. That compensation value can change a dimming function forwarded to the switch in order to compensate for, offset, or substantially eliminate the residual current through that switch.