| 摘要 |
An improved series-pass over-voltage protection circuit includes a P-channel enhancement mode MOSFET (PFET) continuously coupling a DC voltage supply such as a motor vehicle storage battery to one or more electrical loads. The source of the PFET is connected to the positive terminal of the DC voltage supply, and in normal operation, low quiescent current draw is achieved by coupling the gate of the PFET to the negative terminal of the power supply through a low-current current sink. A gate discharge amplifier including a high current capability transistor connected across the source-to-gate circuit of the PFET is activated by a controlled current sink when an over-voltage occurs at the drain of the PFET, and the inherent high impedance of the current sinks relative to the gate discharge amplifier provides high immunity of the PFET to input voltage transients. The result is a practical and highly effective over-voltage protection circuit for continuously powered electrical loads.
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