Power switch with a controlled DI/DT

Details Power switch with a controlled DI/DT Power switch with a controlled DI/DT

1999-12-20

2001-12-04

Meier, Stephen D. (Department: 2822)

Active solid-state devices (e.g., transistors, solid-state diode

Regenerative type switching device

Bidirectional rectifier with control electrode

C257S139000, C257S140000

Reexamination Certificate

active

06326648

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of power regulation. To control the operation of industrial and domestic appliances, semiconductor power components operating in switched mode are often used. So-called conduction angle (or phase angle) controls are thus made, in which a power switch is turned on only for a portion of the duration of each halfwave or of every other halfwave of the supply voltage. Such systems are currently used in the field of domestic lighting to make light dimmers, and in many other applications to form power variators.
2. Discussion of the Related Art
Phase angle power regulation has the well known disadvantage of generating harmonics on the mains due to the fact that the switch closes while a relatively high voltage is present thereacross. These harmonics cause electromagnetic disturbances and are a major problem. Various standards have been developed to require manufacturers to avoid generating such disturbances. A simple way of avoiding the reinjection of harmonics onto the mains is to filter them. However, the addition of a passive filter to a variator is a serious handicap in terms of size, weight and cost. To avoid this filter, it has also been devised to tackle the problem from the base by controlling the current variation speed (di/dt) upon switchings. Unfortunately, neither a thyristor, nor a triac which are ideal components to manufacture a variator due to their robustness, their breakdown voltage, their easy switching and their small on-state dissipated power enable this di/dt control.
It has thus been provided, in the art, to use systems of the type schematically shown in
FIG. 1
, which include power components
1
and
2
in parallel. Component
1
is a component such that the variation of the main current upon turning-on is linked to the variation of the control voltage, for example, a power MOS transistor or an isolated-gate bipolar transistor (IGBT). Component
2
is a component of thyristor or triac type which has the advantage, once on, of exhibiting a very small on-state current drop and which further has the advantage of automatically turning off when the current flowing therethrough becomes substantially zero. Thus, it has been attempted to make switches such that their closing is caused by a component of the type of component
1
while most of the on phase and the turning-off are ensured by a component of the type of component
2
. A control circuit
3
is accordingly provided to turn on the second component, of thyristor type, once the first component, of MOS or IGBT type, has been turned on.
Given that a MOS- or IGBT-type power transistor is a component having a multicell structure, it has generally been tried to associate, with each of the cells of the MOS component, a structure having the thyristor function. The general structure thus is of multicell type.
SUMMARY OF THE INVENTION
The present invention is based on the recognition by the present inventors of the fact that such structures of multicell type have various disadvantages. A first disadvantage is that, for a given maximum current, a multicell type thyristor will inevitably have a larger surface than a monocell thyristor. Another disadvantage is that the connections often are most difficult to make between various cells of a multicell component than with monocell components, which requires increasing the number of metallization levels.
Thus, an object of the present invention is to provide a circuit and a structure of a switch with a controlled di/dt which associates, with a MOS or IGBT transistor of multicell type, a monocell power component of thyristor type, to obtain a component of minimum surface for a given maximum current.
To achieve these and other objects, the present invention provides a monolithic power switch with a controlled di/dt including the parallel assembly of a MOS or IGBT type component with a thyristor type component, including means for inhibiting the thyristor type component during the closing phase of the switch, which is ensured by the IGBT type component. The IGBT type component has a vertical multicell structure and the thyristor type component has a vertical monocell structure.
According to an embodiment of the present invention, the switch is formed in a substrate of a first conductivity type, the rear surface of which includes a region of the second conductivity type. This component includes on the upper surface side first cells of vertical MOS or IGBT type, second cells of vertical MOS or IGBT type, and a cathode gale well of the second conductivity type containing a cathode region of a main thyristor and a cathode region of an auxiliary thyristor. The cathode region of the second cells is connected to the cathode and cathode-gate regions of the auxiliary thyristor, the cathode and cathode gate regions of the main thyristor are connected to a cathode terminal and the area of the well included between the cathode regions of the main and auxiliary thyristors is coated with an isolated gate.
According to an embodiment of the present invention, the switch is formed in a substrate of a first conductivity type, the rear surface of which includes a region of the second conductivity type. This component includes on the upper surface side first cells of vertical MOS or IGBT type, and second cells combining structures of vertical MOS or IGBT type and a vertical auxiliary thyristor structure, these second cells being formed in regions of the second conductivity type and containing two rings of the first conductivity type, the first ring being separated from the second one by a first isolated gate and being connected to the central portion of said region by a metallization, and the second ring being separated from the periphery of the region by a second isolated gate connected to the gate of the first cells.
According to an embodiment of the present invention, the switch further includes a diode of vertical type biased inversely to the thyristor biasing.
According to an embodiment of the present invention, the inhibiting means include a MOS transistor connected between the thyristor gate and cathode.
According to an embodiment of the present invention, the switch includes self-biasing means of the MOS transistor.
The foregoing objects, features and advantages of the present invention will be discussed in detail in the following non-limiting description of specific embodiments in connection with the accompanying drawings.


REFERENCES:
patent: 5349212 (1994-09-01), Seki
patent: 5381025 (1995-01-01), Zommer
patent: 5463231 (1995-10-01), Ogura et al.
patent: A-0 559 945 (1993-09-01), None
patent: WO 99/17374 (1999-04-01), None
Lendenmann H., et al. “Switching Behavior and Current Handling Performance of MCT-IGBT Cell Ensembles” Proceedings of the International Electron Devices Meeting, Washington, Dec. 8-11, 1991, pp. 91/149-152, Institute of Electrical and Electronics Engineers.
Patent Abstracts of Japan, vol. 097, No. 001, Jan. 31, 1997 & JP 08 241980 A (Fuji Electric Co. Ltd.).
Patent Abstracts of Japan, vol. 012, No. 246 (E-632), Jul. 12, 1988 & JP 63 036568 A (Toshiba Corp.).

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