Low-side bidirectional battery disconnect switch
First Claim
Patent Images
1. A battery disconnect switch comprising:
- a first MOSFET comprising a first terminal, a second terminal, a body and a gate;
a second MOSFET connected between said first terminal and said body and having a gate connected to said second terminal;
a third MOSFET connected between said body and said second terminal and having a gate connected to said first terminal; and
a fourth MOSFET connected between said first terminal and said body, a gate of said fourth MOSFET being connected to said body.
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Abstract
A bidirectional battery disconnect switch, i.e., a switch which is capable of blocking a voltage in either direction when open and conducting a current in either direction when closed, is disclosed. The switch includes a four-terminal MOSFET having no source/body short and circuitry for assuring that the body is shorted to whichever of the source/drain terminals of the MOSFET is biased at a lower voltage.
91 Citations
17 Claims
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1. A battery disconnect switch comprising:
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a first MOSFET comprising a first terminal, a second terminal, a body and a gate; a second MOSFET connected between said first terminal and said body and having a gate connected to said second terminal; a third MOSFET connected between said body and said second terminal and having a gate connected to said first terminal; and a fourth MOSFET connected between said first terminal and said body, a gate of said fourth MOSFET being connected to said body. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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- 8. A battery disconnect switch comprising a MOSFET, a first switch and a first voltage clamp being connected in parallel between a first terminal and a body of said MOSFET, and a second switch being connected between a second terminal and said body of said MOSFET, said first switch being closed when a voltage at said second terminal exceeds a voltage at said first terminal by more than a predetermined amount, said second switch being closed when said voltage at said first terminal exceeds a voltage at said second terminal by more than a predetermined amount, said first voltage clamp being for clamping a voltage at said body to a level within a predetermined range from a voltage at said first terminal when both of said first and second switches are open.
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10. A combination comprising:
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a load; a battery for supplying power to said load; and a battery disconnect switch, said battery, said load and said battery disconnect switch being connected in series in a power supply circuit, said battery disconnect switch being connected between a negative terminal of said battery and said load, a first portion of said circuit extending between said negative terminal of said battery and said battery disconnect switch, and a second portion of said circuit extending between said battery disconnect switch and said load, said battery disconnect switch comprising; a first MOSFET; a first conduction path extending between a gate of said first MOSFET and a point in said power supply circuit between a positive terminal of said battery and said load, a first switching element being connected in said first conduction path, said battery disconnect switch being turned on when said first switching element is closed; a second MOSFET connected between said first portion of said circuit and a body of said first MOSFET, a gate of said second MOSFET being connected to said second portion of said circuit; a third MOSFET connected between said second portion of said circuit and said body of said first MOSFET, a gate of said third MOSFET being connected to said first portion of said circuit. - View Dependent Claims (11, 12)
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13. A combination comprising:
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a battery; a battery charger for supplying power to said battery; and a battery disconnect switch, said battery, said battery charger and said battery disconnect switch being connected in series in a power supply circuit, said battery disconnect switch being connected between a negative terminal of said battery and said battery charger, a first portion of said circuit extending between said negative terminal of said battery and said battery disconnect switch, and a second portion of said circuit extending between said battery disconnect switch and said battery charger, said battery disconnect switch comprising; a first MOSFET; a conduction path extending between a gate of said first MOSFET and a point in said power supply circuit between a positive terminal of said battery and said battery charger, a switching element being connected into said conduction path; a second MOSFET connected between said first portion of said circuit and a body of said first MOSFET, a gate of said second MOSFET being connected to said second portion of said circuit; a third MOSFET connected between said second portion of said circuit and said body of said first MOSFET, a gate of said third MOSFET being connected to said first portion of said circuit, said switch further comprising a body bias generator for connecting said body of said first MOSFET to a terminal of said battery charger when said battery charger is properly connected to said battery. - View Dependent Claims (14)
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15. An arrangement comprising:
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a battery; a MOSFET having a drain terminal connected to a negative terminal of said battery; a first body bias generator connected to said drain terminal and a source terminal of said MOSFET, said body bias generator biasing a body of said MOSFET to a lower of a voltage at said drain terminal and a voltage at said source terminal of said MOSFET; and an integrated circuit comprising; a second body bias generator connected to said drain terminal and said source terminal of said MOSFET; an inverter, a first input of said inverter being connected to a positive terminal of said battery and a second input of said inverter being connected to an output of said second body bias generator, an output of said inverter being connected to a gate of said MOSFET. - View Dependent Claims (16, 17)
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Specification