| 摘要 |
PURPOSE: A circuit for preventing a voltage drop is provided to apply a fixed electric current on a display unit at all times by forming a voltage drop sensing unit and an electric current buffer for preventing a voltage from being dropped when a power source of a computer terminal is operated and a mode thereof is changed. CONSTITUTION: A voltage drop sensing unit(4) is connected to one end of the first resistance(10) and the second resistance(12), respectively, and connected to a cathode end of an OP amp(OPerational Amplifier, 18). A standard voltage is connected to the anode end of the OP amp(18). An output end of the OP amp(18) is connected to the third resistance(14) connected to one end of a power supplying unit and is connected to a base end of a transistor(22). An emitter end of the transistor(22) is grounded. An electric current buffer(6) comprises an inverter(24) connected to the power supplying unit, a transmission gate(26) connected to the inverter(24), and an OP amp(28). The cathode end of the OP amp(28) is connected to the power supplying unit, the anode end thereof is grounded, the output end thereof is connected to a thin film register-liquid crystal display module(8). When a voltage is dropped under a predetermined level, the voltage drop sensing unit(4) operates the electric current buffer(6) and supplies an electric current requested in a voltage supply line, and a prompt voltage drop is prevented caused by an undercharge of an electric current.
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