Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Current driver
Reexamination Certificate
2003-07-07
2004-08-24
Ton, My-Trang Nu (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Current driver
C327S448000
Reexamination Certificate
active
06781423
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The invention relates generally to electronic circuits for higher voltages and in particular to half-bridge interface and driver circuits or interfaces realized with integrated-circuit technologies.
(2) Description of the Prior Art
Particularly designed special interface and driver circuits in electronic applications are required, when it comes to handling higher power and voltage levels within half-bridge driver control circuits for lights, motors and other types of actuators. This is a noted and quite common requirement for such electronic circuits very frequently employed in the home appliances and automotive industries; for example for lighting purposes, for drives in washing machines, for engine fan control, for electric power assisted steering, or for wiper and seat positioning systems and so on Therefore the handling of higher voltage levels is an elementary demand. The specific and eligible circuits for these applications are so-called half-bridge branches and full-bridge or H-bridge circuits normally used in single or triple phase configurations. The H-bridge designation vividly depicts the arrangement of the four utilized field effect switching transistors. Said circuits are generally operating together with so-called low-side or bottom and high-side or top control and gate driver interfaces.
Realizations of the prior art for such driver circuits are often implemented as specifically tailored semiconductor circuits, fulfilling the operational demands regarding the higher voltages and the elevated power requirements. Therefore, when a higher voltage handling and mastery is obligatory sometimes DMOS (Double diffused Metal Oxide Semiconductor) transistor devices are used, making necessary an expensive process in semiconductor fabrication. Alternatively specialized integrated circuits incorporating CMOS (Complementary MOS) devices with extended drain realizations are employed, which leads also to more expensive components. Another solution is the choice of discrete high-voltage transistor or thyristor devices fabricated with e.g. IGBT (Insulated Gate Bipolar Transistor) technologies or VMESH (Vertical MESHed transistor arrays). Furthermore these driver circuits have to be interconnected with some logic circuitry, which is controlling the overall operation of the driven electrical devices. These logic circuits or even microprocessor systems normally are working with low voltages. The cooperation within these two voltage domains—one for higher, the other for lower voltages—has to be realized. Thereto an appropriately combined semiconductor technology capable of handling all these demands is chosen, which most often leads to costly solutions.
Referring now to
FIGS. 1A
prior art,
1
B prior art,
1
C prior art, and
1
D prior art, the description of a circuit in prior art integrated circuit (
1
C) realization of said half-bridge is given. The so-called half-bridge is made up of two NMOS (N-channel MOS) transistors, named High-Side (HS) and Low-Side (LS) transistors, which are the only external components in this implementation, and which are shown as externally separated by the waved line in the drawing from the internal parts of the IC described here, all arranged to the left of this line. The HS-transistor is connected at one side to the main high voltage supply (400V) and at its other side to the output or Mid-Point (MP) terminal of said half-bridge. From there the connection is carried on to one side of the LS-transistor, which in turn is leading via its other side to the ground terminal of the circuit. These two transistors are forming one branch of a bridge structure, the other branch being of identical formation and the load balance in the full bridge being achievable or established between the two mid-points respectively. The gates of each of the two transistors in said half-bridge branch are controlled and driven by corresponding gate driver circuit blocks, named HS-Driver and LS-Driver respectively (shown with dashed outlines in the drawing). These driver circuits are differing from each other in such a way, that the HS-Driver includes a data storing means (e.g. an RS—flip-flop), for memorizing the information pertaining to the on-off status of the HS-transistor of the branch. This allows for controlling the HS-Driver circuit with short on-off impulses HS
On
and HS
Off
(see
FIG. 1B
prior art) via the two level shifting field effect transistors FET
S
and FET
R
. This voltage level translation is necessary, because the potential of the reference pin—which is connected to the mid-point (MP) with voltage U
Out
—of the HS-Driver block is elevated to the high voltage level (400V), when the HS-transistor is closed. The short controlling impulses are advantageous, because they allow for a simpler since less powerful and therefore cheaper implementation of the level shifting high-voltage transistors FET
S
and FET
R
, which have to exhibit a high U
DS
break-through voltage, withstanding the maximum occurring potential shift value. A current technology for e.g. 500V as needed here, exhibits therefore a 2-3 &mgr;m oxide sheet strength. The LS-Driver circuit does not need such precautions; the reference potential of which is never rising because of its permanent tie to ground. The control signal LS may therefore be a direct image of the LS-transistor on-off state and thus of the voltage curve for the mid-point voltage U
Out
. It should be understood, that this prior art solution for the engineering task and its circuit is only one possible example, there are many other solutions not discussed here. Nevertheless they altogether contain means for the level translation problem.
Looking now at
FIG. 1B
prior art the aforementioned characteristics of the control signals HS
On
and HS
Off
together with signal LS are depicted, governing the behavior of the mid-point voltage U
Out
.
Referring now to
FIGS. 1C
prior art and
1
D prior art, two possible circuits for the creation of the auxiliary supply voltage U
Supply
(e.g.+12V) for the two driver circuits in
FIG. 1B
prior art are given. The first circuit (
FIG. 1D
prior art) to be explained is a simple Zener-diode (ZD) stabilized voltage generation (derived from the pulsed DC voltage U
DC
) circuit with a resistor R (for high voltage to current conversion) and a capacitor C (for energy storage). However here the current, that can be drawn from this standard circuit is limited to very low values (appr. 1 mA), due to the high internal resistance of the circuit. The second circuit (
FIG. 1C
prior art) should overcome this limitation and could be described as a two-way rectifying diode network, its internal resistance being parameterizable to much lower values. The usable current (also derived from a pulsed DC voltage, here U
Out
at the mid-point MP of a half-bridge) may then be increased to several 10 mA. The function of the coil L
ext
is to simply limit the inrush current into the capacitor C
ext
.
Amongst the prior art solutions more elaborate voltage shifter or voltage translation circuits can be found, as well as potential level isolating solutions with e.g. transformers or optical couplers. It is therefore a challenge for the designer of such circuits to achieve a high-quality, but lower-cost solution.
There are various patents referring to such solutions.
U.S. Pat. No. RE36,480 (to Bourgeois, et al.) describes a control and monitoring device for a power switch, one terminal of which is at a floating reference voltage. The circuit comprises a level translating portion, which is designed to transmit, from another control circuit, orders to the power switch control circuit, or conversely, to receive monitoring information.
U.S. Pat. No. 6,151,233 (to Kondo) discloses a synchronous rectifier circuit. In a switching power circuit adopting this synchronous rectifying system, when a first switch is cut-off, current I
L
of an inducing element is maintained by a commutating diode, and the inducing element releases energy which was stored in the conduction period
Ackerman Stephen B.
Dialog Semiconductor GmbH
Nu Ton My-Trang
Saile George O.
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