| 摘要 |
PURPOSE: A start-up circuit is provided to rapidly supply much current when a main circuit is started in order to shorten a start-up period and be surely separated from the main circuit when the main circuit arrived at a desired operational point. CONSTITUTION: The start-up circuit comprises first to forth transistors(M3,M2,M1,M4). The first transistor(M3) is turned on by the start-up voltage(V1=0V) of a main circuit(32). The second transistor(M2) is turned on by the voltage(V3) according the current(I1) of the first transistor(M3) to supply a start current(I2) from the main circuit(32) and increase the start-up voltage(V1) of the circuit(32). The third transistor(M1) is turned on by the voltage(V3) according to the current(I1) of the first transistor to ground the current(I3) of the transistor(M3). The transistor(M4) is turned on by the start-up voltage(V1) to ground the current(I1).
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