| 摘要 |
An embodiment of the present invention is a switching power supply that includes a full-wave bridge rectifier to rectify incoming AC line voltage, a transformer having a primary winding and two secondary windings and a switched mode power supply chip that includes an integrated high voltage power MOSFET with a low voltage tap in the drift region. The MOSFET controls power switching of the primary winding of the transformer and has a high voltage present during initial power-up. This high voltage is dropped across the JFET part of the MOSFET and supplies a safe operating area protection circuit with a low voltage signal that will shut-off the MOSFET if the current passing through the MOSFET produces a voltage drop at the tap that exceeds a predetermined maximum.
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