| 摘要 |
A method and a system for controlling electric power using an AC source and a power supply device using the system are provided to prevent an excessive voltage from being applied on a load by supplying low-level voltages to the load frequently. A rectifier(100) includes bridge diodes, which fully rectify a sinusoidal wave of an input AC. A voltage level detector(110) is coupled with the rectifier, sets a control reference voltage, and outputs a signal corresponding to the control reference voltage. A phase determining unit(120) controls a switching operation of the AC voltage according to a magnitude of the control reference voltage, which is set in the voltage level detector. A power controller(130) is coupled with the voltage level detector and the phase determining unit. In a low-power control process, the power controller switches on a low power portion at a voltage lower than the control reference voltage. In a high-power control process, the power controller switches on a high power portion at a voltage higher than the control reference voltage. An excessive current detector(140) is connected to an output portion of the power controller. When an excessive current flows through an output terminal, the excessive current detector turns off the AC voltage.
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