US 5,510,641 A · Majority carrier power diode

Abstract

A power diode having substantially no reverse-recovery time and relatively high conductance. The power diode is a majority carrier semiconductor having a structure that is similar to that of a metal oxide semiconductor field effect transistor (MOSFET), in that it includes a source, a drain, a gate, and a body. In one embodiment, to increase conductance of the power diode, a linked-cell configuration that reverses the geometry of a conventional cell-type MOSFET is employed, thereby increasing the width of a conductance channel over that of a conventional MOSFET, and compensating for a relatively low level of inversion in the channel region. Negative and positive feedback circuits are used to further improve the conductance of the power diode by dynamically setting a bias voltage applied between the gate and the source to a level just below a threshold voltage. In the positive feedback circuit, the magnitude of the bias voltage is greater than the threshold voltage if the power diode is forward biased, but substantially reduced if the power diode is reverse biased, thereby minimizing its turn-on delay without risking reverse conductance. Although separate components are used for biasing the device in the disclosed embodiments, it is contemplated that these components be integrated on a common substrate with the source, drain, and gate in a commercially practiced preferred embodiment. Another embodiment employs a charge carrier region diffused into the body and at least in part underlying the gate. This region provides a variable threshold voltage along the channel and reduces the effective length of the channel to increase its conductance. A threshold voltage ranges between a higher value, V.sub.TMAX, adjacent the source, to a lower value, V.sub.T, elsewhere in the device.

Claims40

Dependent claims

A majority carrier semiconductor diode comprising:

(a) an N-type region having a conductive contact, forming a drain;
(b) a P-type material having a conductive contact, forming a body;
(c) an N-type material applied to the P-type material forming the body and having a conductive contact, forming a source;
(d) a dielectric material disposed adjacent the source and the drain and having a conductive contact that is not connected to the source or the drain, the conductive contact forming a gate;
and
(e) biasing means for biasing the gate to provide a conducting N-channel for electrical current flow between the source and the drain for a negative drain-source voltage, while blocking electrical current flow between the source and the drain for a positive drain-source voltage.

3 more elements

A biasing circuit for operating a metal oxide field effect transistor (MOSFET) as a diode that conducts electrical current between a drain and a source of the MOSFET in a forward direction, but not in a reverse direction, said biasing circuit comprising:

(a) conductance monitoring means for sensing one of:
(i) an electrical current flowing through a drain and a source of a MOSFET, or
(ii) a voltage across the drain and source of the MOSFET, said conductance monitoring means producing a feedback signal indicative of said one of the electrical current and the voltage;
and
(b) biasing means, coupled to the conductance monitoring means to receive the feedback signal, for providing a bias voltage in response to the feedback signal, said bias voltage being supplied to a gate of the MOSFET, said biasing means controlling the bias voltage so that the bias voltage is less than a threshold voltage necessary to bias the MOSFET into conductance in the reverse direction, but sufficient to minimize conductance through a body diode portion of the MOSFET in the forward direction.

2 more elements

A biasing circuit for biasing a majority charge carrier device to conduct an electrical current in a forward direction and block a flow of electrical current in a reverse direction through the device, the majority charge carrier device having a body, a gate, a source, and a drain, said biasing circuit comprising:

leakage current monitoring means, coupled to a source and a gate of a majority charge carrier device, for monitoring a leakage current through the majority charge carrier device and controlling a voltage applied to the gate of said device as a function of variations in the leakage current through said device, said static conduction mode enabling current to flow in a forward direction between the source and a drain of said device while the voltage applied to the gate is less than a threshold voltage that would cause conduction of electrical current between the source and the drain in a reverse direction;
and
current comparator means, coupled to the majority charge carrier device to sense electrical current flow between a body and the drain of the majority charge carrier device, and in response to the electrical current, controlling a gate voltage applied to the gate of the majority charge carrier device to control conduction between the source and the drain of said device, said current comparator means applying a voltage greater than the threshold voltage to the gate to initiate conduction in a dynamic mode after conduction of the electrical current between the source and the drain in a forward direction has already been initiated in the static mode and the electrical current flow has exceeded a predefined level, conductance of the device in the dynamic mode being much greater than in the static mode.

Dependencies are inferred from the claim text.

Majority carrier power diode

Life of this patent

Majority carrier power diode

Life of this patent

Abstract

Claims40