Analysis of distributed constant current source for LED lamps
In the past incandescent lamps and energy-saving lamps market, the mainstream lamps and lanterns with limited specifications formed by large companies, in the daily driving power design, it is very difficult to deal with the cumulative error of peripheral devices, resulting in the driving power parameters are far from the original intention of the design. LED has its application flexibility, which will bring more power supply specifications in future design. The principle of distributed constant current is to set up independent constant current source at each parallel branch point to manage, maintain and control the branch. Road and branch, branch and overall line stability.
At present, there is a big gap between the claims of LED products and the actual service life. The stability of the drive line will directly affect the overall stability of the product. The reason for the high reliability of the distributed constant current technology is that the AC power supply part continues to use the traditional switching power supply and adopts a constant voltage power supply mode. The accumulation of switching power supply technology will create quality conditions for LED power supply design. Under the same power supply specifications, there is no need to develop new power supply models, and the power can be backward compatible, greatly reducing power supply specifications and improving power supply uniformity.
Constant current drive requires current detection. The usual practice is to connect milli-even resistors in series to obtain feedback information. To achieve high efficiency, the resistance value will be smaller. Too small milli-even resistors will bring inconvenience to production and testing. , Ordinary instruments cannot verify the correct value, and the production process will also affect the accuracy. The resistance mode setting current is a fixed method, and the adjustment is not convenient. The combination of software and hardware will open a leap in LED application technology. The LED constant current precision value is software-based, which can greatly improve the flexibility of LED applications. Through the computer operating software, the circuit current setting can be completed with intuitive digital writing, and the zero devices around the circuit can be driven. This is our goal. Peripheral zero devices will not bring the accumulation of design device parameter errors, thus greatly improving the accuracy of constant current.
It is feasible to drive LEDs with AC power in a single series connection, but single series connection is only a small part of LED driving applications, and most applications have parallel connections. In the case of parallel LED drivers, the branch LEDs in the overall constant current design do not necessarily work in a constant current state, and the LED currents of the entire product affect each other. For example, in the design of LED street lamps, the designer will not directly connect multiple LEDs in parallel. Go up, because then the danger will occur immediately. The usual practice is to first constant voltage and then DC constant current, which is completed through two-stage design. We know that the DC drive efficiency is that under reasonable voltage and load conditions, the distributed constant current driver can provide the optocoupler drive capability, and one branch can be used as a representative of all branches. Distributed constant current branches can communicate with each other to realize an adaptive linkage mechanism, and are compatible with control, data read and write interface functions.
Our country's IC manufacturing process cannot currently meet the LED drive accuracy requirements, but we can use new technologies and new methods to achieve the world's top constant current accuracy level. Precise drive control is one of the methods. Distributed constant current circuit can be regarded as a complete circuit structure in use, but the actual application is distributed in each node of the circuit. It is a circuit that can be controlled by constant current and can communicate with each other. Circuit configuration
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