Half-bridge circuit

Details Half-bridge circuit Half-bridge circuit

2002-01-24

2004-11-23

Philogene, Haissa (Department: 2821)

Electric lamp and discharge devices: systems

Periodic switch in the supply circuit

Silicon controlled rectifier ignition

C315S291000, C315S244000, C257SE27060, C257S388000, C363S144000

Reexamination Certificate

active

06822399

ABSTRACT:

BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a half-bridge circuit having a first and a second transistor that are connected in series, and having a drive circuit for driving the transistors. The invention relates, in particular, to a half-bridge circuit for use in a switching regulator.
The handbook “1999/2000 Industrial Power Seminar”, pages 6-3 and 6-7, from Intersil Corporation™, Irvine, Calif. USA 92618, describes a switching regulator with a half-bridge circuit as shown in FIG.
1
. The half-bridge circuit shown in
FIG. 1
has two n-channel MOSFETs M
1
, M
2
, whose drain-source paths are connected to form a series circuit. This series circuit is connected to a supply voltage U
1
. A drive circuit
100
is provided for driving the MOSFETs M
1
, M
2
. The drive circuit
100
is connected to the gate connections of the MOSFETs M
1
, M
2
and to the supply voltage for voltage supply purposes. So that the required drive potential for the first MOSFET M
1
, which functions as a high-side switch, can be made available in the drive circuit
100
, a bootstrap circuit with a capacitor C
2
and a diode D
1
is provided, which is likewise connected to the drive circuit
100
. The drive potential required for the first MOSFET M
1
is higher than the supply voltage U
1
.
The known half-bridge circuit shown in
FIG. 1
is part of a switching regulator, a so-called buck converter in the example illustrated, which provides a smaller output voltage U
2
from the supply voltage U
1
. In this case, a series circuit including a coil L
1
and a capacitor C
1
is connected in parallel with the second MOSFET M
2
, which functions as a low-side switch. It is possible to tap off the output voltage U
2
across the capacitor C
1
.
Switching regulators of this type are used, in particular, in computers for supplying voltage to the CPU. In this case, the input voltage is usually 5.0 V and the output voltage is between 1.3 V and 2.0 V. A customary clock frequency with which the two MOSFETs are switched is about 200 kHz. In this case, the two MOSFETs M
1
, M
2
are driven, depending on the output voltage U
2
, such that the output voltage is at least approximately constant—independently of the load and of fluctuations in the input voltage.
For future applications in computers, the switching regulators ought to be able to correct a load change at the output of the switching regulator within a time period of less than 100 ns. That requires clock frequencies of 2 MHz or more for the switches.
In this case, the line connections between the components and the half-bridge should be as short as possible. Furthermore, the two transistors should be accommodated in one housing, as much as possible, to save space.
In the case of the known half-bridge circuit, a comparatively high outlay is required to accommodate the two transistors and possibly also the drive circuit. Vertically designed transistors are usually used as the power transistors in switching regulators. Such transistors are usually applied to a printed circuit board by their rear side, which forms the drain connection of the transistor. In the case of the known circuit arrangement shown in
FIG. 1
, different potentials are required at the drain connections of the transistors, so that a printed circuit board on which the two transistors are to be jointly applied must have at least two islands with different potentials. Moreover, if the intention is to accommodate the drive circuit on the same printed circuit board, at least three such potential islands must be provided.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a half-bridge circuit which overcomes the above-mentioned disadvantages of the prior art apparatus of this general type.
In particular, it is an object of the invention to provide a half-bridge circuit for switching regulators, which can be realized in a space-saving manner and which can be used at comparatively high switching frequencies.
With the foregoing and other objects in view there is provided, in accordance with the invention, a half-bridge circuit including a first semiconductor body having a first MOS transistor that is integrated in the first semiconductor body. The first MOS transistor is a vertically designed n-conducting MOS transistor. The half-bridge circuit includes a second semiconductor body having a second MOS transistor that is integrated in the second semiconductor body. The second MOS transistor is a vertically designed p-conducting MOS transistor. The half-bridge circuit also includes: a drive circuit for driving the first MOS transistor and the second MOS transistor; a common connection plate to which the first MOS transistor and the second MOS transistor are applied; and a first connection terminal and a second connection terminal. The first MOS transistor and the second MOS transistor are connected in series between the first connection terminal and the second connection terminal.
In accordance with an added feature of the invention, the first semiconductor body has a front side and a rear side; the first MOS transistor has a drive connection and a first load path connection that are accessible at the front side of the first semiconductor body; the first MOS transistor has a second load path connection that is accessible at the rear side of the first semiconductor body; the second semiconductor body has a front side and a rear side; the second MOS transistor has a drive connection and a first load path connection that are accessible at the front side of the second semiconductor body; and the second MOS transistor has a second load path connection that is accessible at the rear side of the second semiconductor body.
In accordance with an additional feature of the invention, a capacitor is connected between the first load path connection of the first transistor and the first load path connection of the second transistor.
In accordance with another feature of the invention, the capacitor is applied to the first semiconductor body and to second semiconductor body; the capacitor has a first connection connected to the first semiconductor body; and the capacitor has a second connection connected to the second semiconductor body.
In accordance with a further feature of the invention, a bonding wire electrically connects the first connection of the capacitor to the first semiconductor body; and a bonding wire electrically connects the second connection of the capacitor to the second semiconductor body.
In accordance with yet an added feature of the invention, a first layer electrically connects the first connection of the capacitor to the first semiconductor body; and a second layer electrically connects the second connection of the capacitor to the second semiconductor body. The first layer and the second layer are made of either a soldering material or an electrically conductive adhesive.
In accordance with yet an additional feature of the invention, an electrically conductive adhesive solders or bonds the first semiconductor body and the second semiconductor body onto the common connection plate.
In accordance with yet another feature of the invention, the drive circuit is integrated into a third semiconductor body; the first semiconductor body has a front side; and the third semiconductor body is applied to the front side of the first semiconductor body.
In accordance with yet a further feature of the invention, a common housing surrounds the first semiconductor body, the second semiconductor body, and the drive circuit.
The invention makes use of the fact that in a half-bridge circuit with a p-conducting transistor and an n-conducting transistor, of which only one at a time is to be driven conductively, the drain connections of the two transistors are connected to one another and are thus at a common potential. The rear sides of the two semiconductor bodies in which the two transistors are integrated can thus be applied to a common electrically conductive connection plate. The respective drain connection is accessible at each of the rear s

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