Method of blocking bidirectional flow of current
First Claim
1. A method of blocking a flow of current between a first terminal and a second terminal, respective voltages at the first and second terminals varying such that during a first time interval a first voltage at the first terminal is greater than a first voltage at the second terminal and during a second time interval a second voltage at the second terminal is greater than a second voltage at the first terminal, the method comprising the steps of:
- providing a MOSFET, the MOSFET comprising a first region of a first conductivity type separated from a second region of the first conductivity type by a body region of a second conductivity type, the MOSFET further comprising a gate separated from a channel region of the body region by a dielectric layer, wherein neither the first region nor the second region is shorted by the body region;
conducting said first terminal to said first region;
connecting said second terminal to said second region;
maintaining the body region at at least one potential such that neither a PN junction between the first region and the body region nor a PN junction between the second region and the body region is forward-biased so as to conduct a current as the voltages at the first and second terminals vary;
biasing the gate so as to block a flow of current between the first and second regions in a first direction during the first time interval; and
biasing the gate so as to block a flow of current between the first and second regions in a second direction during the second interval.
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Abstract
A bidirectional current blocking switch is disclosed. The switch includes a four-terminal MOSFET in which there is no source-body short. The voltages applied to the source and drain terminals are both higher than the voltage applied to the body terminal (for an N-channel) device so that the source-body and drain-body junction of the MOSFET never become forward-biased. The switch of this invention is particularly useful for switching a cascaded set of batteries in a portable computer.
26 Citations
15 Claims
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1. A method of blocking a flow of current between a first terminal and a second terminal, respective voltages at the first and second terminals varying such that during a first time interval a first voltage at the first terminal is greater than a first voltage at the second terminal and during a second time interval a second voltage at the second terminal is greater than a second voltage at the first terminal, the method comprising the steps of:
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providing a MOSFET, the MOSFET comprising a first region of a first conductivity type separated from a second region of the first conductivity type by a body region of a second conductivity type, the MOSFET further comprising a gate separated from a channel region of the body region by a dielectric layer, wherein neither the first region nor the second region is shorted by the body region; conducting said first terminal to said first region; connecting said second terminal to said second region; maintaining the body region at at least one potential such that neither a PN junction between the first region and the body region nor a PN junction between the second region and the body region is forward-biased so as to conduct a current as the voltages at the first and second terminals vary; biasing the gate so as to block a flow of current between the first and second regions in a first direction during the first time interval; and biasing the gate so as to block a flow of current between the first and second regions in a second direction during the second interval. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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Specification