Abstract
Spectroscope in examination process, only then the photo source maintains under the high stable premise, can guarantee the survey obtains extinction value accurate reliable. Must make the bromine-tungsten lamp its light spoke flux to stabilize in 0.1%, the corresponding power line voltage fluctuation must below 0.1%, must therefore form a complete set the special-purpose photo source electric power supply. Therefore in view of the fact that the design requirements the request constant current has the stable output current, moreover the accuracy requirement is high.
In this system the DC source is center and 89S52 version single chip microcomputer (SCM) is main controller, output current of DC power can be set by a keyboard which step level reaches 4mA, while the real output current and the set value can be displayed by LED. In the system, the digitally programmable signal from SCM is converted to analog value by DAC (AD7543), then the analog value which is isolated and amplified by operational amplifiers, is sent to the base electrode of power transistor, so an adjustable output current can be available with the base electrode voltage of power transistor. On the other hand, The constant current source can be monitored by the SCM system real-timely, its work process is that output current is converted voltage, then its analog value is converted to digital value by ADC, finally the digital value as a feedback loop is processed by SCM so that output current is more stable, so a stable voltage-controlled constant current power is designed.
Keywords: voltage-controlled constant current source；intelligent power；closed loop control
