Reverse recovery charge reduction circuit

A method for reducing or eliminating current or voltage transients in a power converter comprising:

• providing the power converter comprising a first switch comprising a first transistor with a gate and a source, a second switch comprising a second transistor with a gate, a drain, a body diode and a backgate, a driver stage and a parallel clamping device, wherein the source of the first transistor is connected to the drain of the second transistor, the gate of the second transistor is connected to the driver stage and the parallel clamping device, and a reverse turn-on voltage of the second transistor is less than a forward threshold voltage of the body diode;
• and
• applying a selected backgate bias voltage to the backgate of the second transistor to lower a reverse-threshold voltage of the second transistor;1
• controlling the switch,
• wherein, (1) a turn-off voltage of the second transistor is a bias voltage greater than zero and less than a threshold voltage of the second transistor and (2) the turn-off voltage is applied to the gate of the second transistor by the driver stage to turn off the second transistor, preventing the forward current flow through the second transistor;
• wherein in a presence of a voltage that crosses above zero in the drain of the second transistor, applying a zero voltage to the gate of the second transistor by the parallel clamping device, thereby reducing or eliminating current or voltage transients.

A method for reducing or eliminating current or voltage transients from accumulated reverse recovery charge in a switch comprising:

• providing the switch, wherein the switch comprises a transistor with a gate, a body diode and a backgate;
• and
• controlling the switch,
• wherein in a presence of a forward current, (1) a turn-off voltage of the transistor is a bias voltage that is greater than zero and less than a threshold voltage of the transistor and (2) the turn-off voltage is applied to the gate, such that the forward current will not flow through the transistor;
• and
• wherein in a presence of a reverse current, (1) a reverse turn-on voltage of the transistor is less than a forward threshold voltage of the body diode and (2) applying a backgate bias voltage to the backgate to lower a reverse-threshold voltage of the transistor, thereby reducing or eliminating current or voltage transients from accumulated reverse recovery charge.

A switch comprising:

• a transistor comprising a gate, a drain, a body diode and a backgate, wherein a reverse turn-on voltage is lowered when a selected backage bias voltage is applied to the backgate, a reverse current will not flow through the body diode, a reverse recovery charge will not accumulate at the body diode, and the reverse turn-on voltage is less than a forward threshold voltage of the body diode;
• wherein, (1) a turn-off voltage of the transistor is a bias voltage greater than zero and less than a threshold voltage of the transistor and (2) the turn-off voltage is applied to the gate to turn off the transistor, and a forward current will not flow through the transistor;
• and
• wherein in a presence of a voltage that crosses above zero in the drain of the transistor, applying a zero voltage to the gate, thereby reducing or eliminating current or voltage transients.

A power converter comprising:

• a first switch comprising a first transistor comprising a gate and a source;
• a second switch comprising a second transistor comprising a gate, a drain, a body diode and a backgate, wherein the drain is connected to the source of the first transistor, a reverse turn-on voltage of the second transistor is lowered when a selected backgate bias voltage is applied to the backgate, and the reverse turn-on voltage of the second transistor is less than a forward threshold voltage of the body diode, and;
• a driver stage connected to the gate of the second transistor;
• a clamping device connected to the gate of the second transistor;
• wherein, (1) a turn-off voltage of the second transistor is a bias voltage that is greater than zero and less than a threshold voltage of the second transistor and (2) the turn-off voltage is applied to the gate of the second transistor by the driver stage to turn off the second transistor, and a forward current will not flow through the second transistor;
• and
• wherein in a presence of a voltage that crosses above zero in the drain of the second transistor, applying a zero voltage to the gate of the second transistor by the clamping device, thereby reducing or eliminating current or voltage transients.

A switch comprising:

• a transistor comprising a gate, a body diode, and a backgate;
• wherein in a presence of a forward current (1) a turn-off voltage of the transistor is a bias voltage that is greater than zero and less than a threshold voltage of the transistor and (2) when the turn-off voltage is applied to the gate, the forward current will not flow through the transistor;
• and
• wherein in a presence of a reverse current, (1) a reverse turn-on voltage of the transistor is less than a forward threshold voltage of the body diode and (2) applying a backgate bias voltage to the backgate to lower a reverse-threshold voltage of the transistor, thereby reducing or eliminating current or voltage transients.