The Study And Design On Constant Current Driver System Of 25A

Semiconductor laser diode is a minitype laser diode based on Pn knot orPin knot formed by direct bandgap semiconductor material. Semiconductorlaser diode has many excellent characters such as small size, light weight, highreliability, high conversion efficiency, low power, simple driving power supply,directly modulating, simple structure, low cost, safety and wide application etc.With the rapid developing of science and technology, the techniques ofsemiconductor laser diode have been applied widely in many fields such asindustry, high technical production and science research.Semiconductor laser diode is a kind of device with high power density andsky-high quanta efficiency. Even weak drive current and temperature changingwill lead to its large changing of output light power and device parameters,which directly damages the safe use of laser diode. Thus in application werequire the laser diode has the lowest electronical yawp and the highest stability.We should keep laser diode matching with the chosen driver. So higher requestto the laser diode is put forward. It is very important for the design andexperiment of constant current driver. And the driver should have higherstability of output current. This paper mainly introduces circuit design andanalyzing result of large output current driver system.The semiconductor laser diode described by this paper is mainly constantcurrent driver. The constant current drive circuit is composed of voltagebenchmark circuit, voltage-current conversion circuit and adjusting circuit. Thewhole design idea is to use the principle of negative feedback to stabilize outputcurrent which obtains the lowest current error and the highest current stability.In order to achieve large current output of constant current driver, we needimprove the adjusting circuit. We can change the circuit from one powerMOSFET to two shunt-wound MOSFET. The reason is that the current outputof one power MOSFET is limited and depends on many environment factorssuch as dispersing heat. When we use two shunt-wound MOSFET, we canincrease stable output current and achieve large current driving. In this paper,we analyze three different solutions of shunt-wound power MOSFET circuit.And we also measure the value of output current, stability and averagedistributing of the two shunt-wound power MOSFET. Using these data, we talkout the advantage and disadvantage of the three different solutions. At last weconfirm a solution of large current output of constant current driver.If we want to improve the constant current driver reliability and stability,we must consider the choice of parts and solve dispersing heat. We shoulddispose of dispersing heat well due to the large output current of whole constantcurrent driver. If we can't solve the heat issue, parts will change specialtybecause of high temperature. As we all known, high temperature also can makeparts permanent invalidation owing to pole touching and semiconductor layermelting. The basic task of dispersing heat design is that we can make a heatflow circuit having the lowest heat resistance according to principle of heattransfer and we should keep parts heat be thrown off. In this way we can ensureinternal knot temperature lower than allowable temperature when parts run.This paper describes the details of radiator design and how to select the methodof dispersing heat.Finally, the paper also discusses the question at present and the developingdirection in future.The work of this paper has positive meaning to the wide applications ofthe semiconductor laser diode. The work also makes the great current output ofthe semiconductor laser diode constant current driver become actualization.According to the practical application, it indicates that the driver is safe andcredible to the semiconductor laser diode;moreover, the driver has manyadvantages such as the high steady output and the strong anti-interferenceability.