US 5,510,747 A · Gate drive technique for a bidirectional blocking lateral MOSFET

Abstract

A gate drive circuit for a bidirectional blocking MOSFET, the bidirectional blocking MOSFET being characterized in the source region is not shorted to the body region. In one embodiment, the gate drive circuit includes diodes connected between the source/drain regions and a charge pump, the charge pump generating a gate drive voltage applied to a gate of the bidirectional blocking MOSFET. In a second embodiment, a charge pump generates a gate drive voltage which is applied to the gate of the bidirectional blocking MOSFET, and is also connected to the source/drain regions through zener diodes. In the second embodiment, the potential applied to the gate of the bidirectional blocking MOSFET is limited to a zener diode drop above the lower of the voltages of the source/drain regions. In a fourth embodiment, a charge pump generates a floating gate drive voltage which is applied to gate of the bidirectional blocking MOSFET through first and second depletion mode MOSFETS. In the fourth embodiment, the gate drive voltage is limited to the threshold level of the first and second depletion mode MOSFETs and the voltage present on the more negative of the source/drain regions. In the second and fourth embodiments, the limited gate drive allows for a minimal gate oxide thickness, thereby improving switch resistance.

Claims22

Dependent claims

A gate drive circuit for generating a gate drive voltage on a gate of a bidirectional MOSFET, the bidirectional MOSFET including a body, first and second regions of a first conductivity type formed in the body and separated by a channel region of a second conductivity type also formed in the body, the gate being located over the channel and separated from the body by a gate oxide layer, wherein the first and second regions of the bidirectional MOSFET are electrically isolated from the body and the body is maintained at a voltage level which is either higher or lower than voltage levels of both the first and second regions, the gate drive circuit comprising:

a voltage generating circuit comprising a charge pump having an input terminal connected to the first region through a first rectifying device, the input terminal also being connected to the second region through a second rectifying device, the voltage generating circuit also having an output terminal connected to the gate of the bidirectional MOSFET for producing the gate drive voltage at a level less than or equal to a maximum voltage determined by a thickness of the gate oxide layer.

A gate drive circuit for generating a gate drive voltage on a gate of a bidirectional MOSFET, the bidirectional MOSFET including a body, first and second regions of a first conductivity type formed in the body and separated by a channel region of a second conductivity type also formed in the body, the gate being located over the channel and separated from the body by a gate oxide layer, wherein the first and second regions of the bidirectional MOSFET are electrically isolated from the body, and the body is maintained at a predetermined voltage, the gate drive circuit comprising:

a voltage generating circuit comprising a charge pump having an input terminal connected to the first region through a first rectifying device, the input terminal also being connected to the second region through a second rectifying device, the charge pump generating an output voltage which drives the gate of the bidirectional MOSFET, the output voltage being generated solely from current received from the first and second rectifying devices, wherein the output voltage from the charge pump produces the gate drive voltage at a level less than or equal to a maximum voltage determined by a thickness of the gate oxide layer.

A method for generating a gate drive voltage on a gate of a bidirectional MOSFET, the bidirectional MOSFET including a body, first and second regions of a first conductivity type formed in the body and separated by a channel region of a second conductivity type also formed in the body, the gate being located over the channel and separated from the body by a gate oxide layer, wherein the first and second regions of the bidirectional MOSFET are electrically isolated from the body and the body is maintained at a predetermined voltage potential, the method comprising:

connecting the first region and the second region to an input terminal of a voltage generating circuit, wherein the voltage generating circuit includes a charge pump, through first and second rectifying devices such that the first region is connected to the input terminal through a first rectifying device, and the second region is connected to the input terminal through a second rectifying device;
connecting the gate of the bidirectional MOSFET to an output terminal of the charge pump, wherein the charge pump generates an output voltage which produces the gate drive voltage at the gate of the bidirectional MOSFET, the output voltage being generated solely from current received from the first and second rectifying devices;
and
limiting the gate drive voltage to a level less than or equal to a maximum voltage determined by a thickness of the gate oxide layer.

1 more element

Dependencies are inferred from the claim text.

Gate drive technique for a bidirectional blocking lateral MOSFET

Life of this patent

Gate drive technique for a bidirectional blocking lateral MOSFET

Life of this patent

Abstract

Claims22