Abstract:

SC91F721 microcontroller, as the control core of the flash power supply, raises the low DC input voltage by using current
mode chopper circuit to supply power to microcontroller, and stabilizes the output current of the switch control circuit by the metaloxide
semiconductor. Using the feedback output current of the sampling circuit, the output Pulse Width Modulation（PWM）signal and
the constant current source control circuit are effective. The experimental results show that the converter can realize two kinds of output
mode: continuous and pulse, battery power conversion to constant current output, high brightness white light emitting diode, current
profile selection, output voltage limiting protection and overload alarm function. The relative error is less than 1.5% and the efficiency
is 91.8%, which can meet the requirement of constant current power supply.

Key words: Pulse Width Modulation（PWM）, constant-current source, sampling circuit