This paper discusses the precise control of led constant current drive, and tells the difference between different drivers in different applications, including the introduction of distributed constant current drive principle, the precision control idea of ​​soft and hard combination, and the new design method to improve LED drive efficiency.
Introduction to distributed constant current drive principle
In the past incandescent and energy-saving lamps market, LEDs have become a mainstream lamp type with limited specifications, and it is difficult for LEDs to continue to comply. LEDs have the flexibility of application and will bring more power specifications in future designs. We have to avoid too many power supply specifications and do not bring many obstacles to mass production in the future. Based on the idea of ​​not limiting design flexibility while also taking into account as few power supply design specifications as possible, we propose a distributed constant current architecture.
The principle of distributed constant current is to establish independent constant current sources at each parallel branch point to manage, maintain and control the stability of branches and branches, branches and overall lines. The distributed constant current circuit can be regarded as a complete line structure in use, and the practical application is distributed in each node of the line, which is a circuit structure that can be controlled by constant current and can communicate with each other. Distributed constant current design LED products have very high product stability and unique design advantages.
At present, LED products claim a big gap with the actual service life. In the case where the accumulation of drive line design technology is limited, the actual service life is measured by the method of evaluating the life of the product, which is easy to cause errors. The stability of the drive line will directly affect the overall stability of the product.
The reason why the distributed constant current technology has high reliability is that the AC power supply section continues to use the conventional switching power supply, and the constant voltage power supply mode is adopted. The accumulation of switching power supply technology will create quality conditions for LED power supply design. Under the same power supply specification, it is no longer necessary to develop a new power supply model, the power can be backward compatible, greatly reducing power supply specifications and improving power supply uniformity.
Soft and hard combination precision control ideas
In the daily drive power supply design, the cumulative error of peripheral devices is very difficult to handle, resulting in a far cry from the original design of the drive power parameters. Constant current driving requires current detection. The usual method is to connect the millicouple resistors in the branch to obtain feedback information. To achieve high efficiency, the resistance value will be smaller. Too small millicouple resistors will cause inconvenience to production and testing. The general instrument can not verify the correct value, the production process will also affect the accuracy, and the resistance mode setting current is a fixed mode, and the adjustment is not convenient.
The combination of software and hardware will open the leap in LED application technology. The LED constant current accuracy value is softwareized, which can greatly enhance the flexibility of LED applications. The constant current driver current setting software is actually setting up the register inside the IC, and setting the output current according to the actual product application storage method. All of these are software-based processes, and there is no need to change the circuit design. The circuit current setting can be done with intuitive digital writing through the microcomputer operating software.
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