| 摘要 |
A two-stage power supply start-up circuit (131 and 132) is provided for pulse width modulator controllers (100) that operate at a low steady state voltage. The invention provides for high energy storage in low capacitance star- up by cascading switched start-up stages, thereby allowing for the utilization of smaller, less expensive components. The invention utilizes a three phase start-up process with positive feedback (108) ensuring both reliable start-up (S1) and steady state operation. The three phases are as "first phase start-up" (S1) which provides power to the control circuit, "second phase start-up" (101) where the control chip starts switching, and "steady state" (121) where the power supply runs in its normal mode.
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