POWER SUPPLY HAVING LAMP PROTECTION FUNCTION USING EXTERNAL VOLTAGE

摘要

A power supply unit is provided to perform the lamp protective function by determining the malfunction state of lamp based on comparison between the inducted voltage from the output winding of transformer and the outside constant voltage. A switching unit(100) converts the DC power source into the AC power. The transformer(120) comprises the primary winding (pw), the secondary winding (sw) and the inducted terminal. The primary winding receives the AC power through the input terminal from the switching unit. The secondary winding converts the AC power into the AC power for the lamp drive according to the predetermined winding ratio. The secondary winding outputs the AC power for the lamp drive to the lamp(130) through the output terminal. The inducted terminal receives the voltage from the secondary winding. The detection unit(140) detects the malfunction of transformer based on comparison between the inducted voltage from the inducted terminal and the predetermined reference voltage. According to the detection result of the detection unit, the controller(150) controls the switching of the switching unit. The inducted terminal includes at least one positive inducted terminal and at least one negative inducted terminal. The positive inducted terminal receives the positive (+) voltage of the inducted voltage from the secondary winding. The negative inducted terminal receives the negative (-) voltage of the inducted voltage from the secondary winding.