Light-emitting Element Driving Circuit with Auxiliary Potential Control Unit
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Solution Overview
Problem
Conventional light-emitting element driving circuits require a long start-up time due to the limited charging speed of capacitors, which hampers the speed of Auto Power Control (APC) operations.
Innovation Solution
Incorporating an auxiliary potential control unit with a higher drivability current source to assist the potential control unit, allowing for faster charging and discharging of the capacitor, thereby reducing the start-up time and accelerating the APC operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single operational amplifier is used for both charging operations before APC and at the time of APC operation, then the circuit complexity is reduced, but the charging speed is limited by the drivability of the operational amplifier, resulting in long start-up time
Solution Approach 1:
The potential control function is segmented into two independent units: a potential control unit for normal APC operation and an auxiliary potential control unit for fast charging during start-up. This segmentation allows each unit to be optimized for its specific function, with the auxiliary unit providing high-speed charging capability without limiting the normal operation of the main potential control unit.
Solution Approach 2:
The circuit dynamically switches between the auxiliary potential control unit and the potential control unit based on the operational state. During start-up when the light amount difference is large, the auxiliary unit with higher drivability is activated for fast charging. During normal APC operation, the standard potential control unit is used, providing a dynamic adaptation to different operational requirements.
2Productivity
If the capacitor is charged in advance to a predetermined voltage before APC operation, then the APC operation speed is improved, but the start-up time is extended due to the charging time requirement
Solution Approach 1:
The circuit employs dynamic control by activating the auxiliary potential control unit only during the initial phase when the light amount difference exceeds the reference value. This dynamic switching allows the capacitor to be charged rapidly at start-up without requiring advance charging to a predetermined voltage, thus improving both start-up time and APC operation speed.
Solution Approach 2:
The drivability parameter is changed by introducing the auxiliary potential control unit with higher drivability current source. This parameter change enables the capacitor charging speed to be increased significantly during the critical start-up phase, eliminating the need for advance charging and reducing overall start-up time while maintaining fast APC operation.
3Loss of time
If the drivability of the potential control unit is increased to speed up capacitor charging, then the start-up time is reduced, but the power consumption and circuit complexity increase
Solution Approach 1:
The control function is segmented into two independent units with different drivability characteristics. The auxiliary potential control unit with high drivability is used only when needed (during start-up), while the standard potential control unit handles normal operation. This segmentation achieves fast start-up without requiring the entire circuit to have high complexity.
Solution Approach 2:
The auxiliary potential control unit automatically activates when the light amount difference exceeds the reference value, providing high-speed charging assistance without requiring external control. The unit self-regulates based on the operational conditions, reducing the need for additional control circuitry and minimizing overall circuit complexity while achieving fast start-up.
Data Source
AI summary
A light-emitting element driving circuit comprising, a light-emitting element, a driving unit which has a control terminal and is configured to drive the light-emitting element according to a potential of the control terminal, a node connected to the control terminal, a monitor configured to monitor an emitted light amount of the light-emitting element, a potential control unit configured to control a potential of the node so that the emitted light amount of the light-emitting element approaches a target value, and an auxiliary potential control unit configured to assist potential control of the node by the potential control unit when a difference between the emitted light amount of the light-emitting element detected by the monitor and the target value is larger than a reference amount.