Low-side bidirectional battery disconnect switch
AssigneeSiliconix Incorporated
InventorsRichard K. Williams, Robert G. Blattner
Life of this patent
Estimating the term…
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.
Claims17
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.
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.
A combination comprising:
- 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.
A combination comprising:
- 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.
An arrangement comprising:
- 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.
Dependencies are inferred from the claim text.