| 摘要 |
In one embodiment, a startup circuit for a power supply is provided. The startup circuit comprises a resistance coupled between a voltage source and a first node. A first capacitor, coupled to the first node, is operable to be charged by current flowing through the resistance. A first transistor has an emitter, a base, and collector, wherein the collector is coupled to the voltage source and the base is coupled to the first node. A diac circuit, coupled to the emitter of the first transistor, is operable to fire to turn on the first transistor, thereby allowing discharge of the first capacitor through the base-emitter junction of the first transistor. A second capacitor is operable to be charged by current related to a discharge voltage resulting from the firing of the diac circuit. The second capacitor operable to store charge to provide VCC voltage to a controller of the power supply. |
