Electric power conversion systems – Current conversion – With condition responsive means to control the output...
Reexamination Certificate
2000-05-12
2001-06-26
Berhane, Adolf Deneke (Department: 2838)
Electric power conversion systems
Current conversion
With condition responsive means to control the output...
C363S068000, C363S021040
Reexamination Certificate
active
06252787
ABSTRACT:
TECHNICAL FIELD
This invention relates to bi-directional current circuits.
BACKGROUND OF THE INVENTION
Airplanes often have an on-board gas turbine engine referred to as an auxiliary power unit that provides electrical power and compressed air to various systems throughout the airplane. When the airplane is on the ground, the auxiliary power unit is the main source of power to drive the environmental control systems, air driven hydraulic pumps, and the starters for the engines. Auxiliary power units may also provide pneumatic and electric power during flight.
FIG. 1
shows a typical Auxiliary Power Unit (APU) generally denoted by the reference numeral
10
. The APU
10
includes in flow series arrangement an air inlet
14
, a compressor
16
, a bleed port
18
for providing compressed air to the aircraft, a combustor
20
having a primary fuel nozzle
22
and a secondary fuel nozzle
24
, a turbine
26
and a gas exhaust
28
. Of the two nozzles
22
and
24
, only the primary nozzle
22
operates during the initial stages of a startup. The compressor
16
and the turbine
26
are mounted for rotation on a shaft
30
which extends to a gearbox
32
.
Mounted to the gearbox
32
is a fuel control unit
40
in fluid communication with a fuel source, (not shown), aboard the aircraft. Preferably, the fuel control unit
40
is a single stage, electromechanical fuel metering valve of the type which is well known in the art. The fuel control unit
40
includes an electrically operated torque motor
42
which has a known and repeatable relationship with a power signal from an electronic control unit (ECU)
80
which may be analog or digital. The motor
42
is directly coupled to a metering valve, not shown, and controls the valve position so that a known flow area in the metering valve corresponds to a known power signal from the ECU
80
. The ECU
80
communicates with the torque motor
42
through a bi-directional circuit such as an H-bridge, and commands the motor
42
to open the valve, when an increase in fuel flow is needed, and to close the valve when a decrease in fuel is required. The ECU
80
also controls the speed at which the torque motor opens and closes the valve. From the fuel control unit
40
metered fuel flows through a conduit
46
to a flow divider
50
. From the flow divider
50
the stream of fuel splits with a portion flowing through a conduit
52
which leads to the primary fuel nozzle
22
and the remainder through a conduit
54
to a secondary fuel nozzle
24
.
One type of bi-directional circuit used between the ECU
80
and the torque motor
42
is the conventional H-bridge. This configuration typically uses one power supply and four power switches (i.e. power transistors) to produce the desired current flow through a load. The load is the device to which power is delivered, (i.e. the torque motor
42
). It can be resistive, or inductive. The advantage of the H-bridge configuration is that it uses a single power source (i.e. the ECU
80
). Referring to
FIG. 2
, the current to the load is controlled by means of the four power switches. During one half cycle, current flows from switch A through the load to switch D. During the other half cycle, current flows from switch B through the load to switch C.
There are, however, several disadvantages to using an H-bridge. The H-bridge requires four power switching devices for each load. Since power switching devices are usually the most expensive components of a driver, these types of switches drive up the cost of the ECU
80
in which they are mounted. There is also a size limitation. With four power switching devices, the power driver might grow beyond the size limitations of the overall design. Another disadvantage is that during any half cycle power is always being dissipated in two power switching devices, either A and D or B and C.
Accordingly, there is a need for bi-directional current circuit that has fewer switches and thus takes up less board area, costs less, dissipates less power and has fewer parts than an H-bridge.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an improved bi-directional current circuit.
The present invention meets this objective by providing a bi-directional current circuit disposed between two power sources and a load. First and second switches are arranged in series with the load and connect the load to one of the power sources, whereby when said first switch is closed and said second switch is open current flows to the load in a first direction and when said first switch is open and said second switch is closed current flows to the load in a second direction opposite to the first direction.
Thus a bi-directional current circuit or source is provided that has fewer switches, takes up less board area, dissipates less power and costs less to manufacture than an H-bridge circuit.
These and other objects, features and advantages of the present invention are specifically set forth in or will become apparent from the following detailed description of a preferred embodiment of the invention when read in conjunction with the accompanying drawings.
REFERENCES:
patent: 4150413 (1979-04-01), Nerem
patent: 4438411 (1984-03-01), Rubin et al.
patent: 4471289 (1984-09-01), Duley et al.
patent: 4520296 (1985-05-01), Lepper et al.
patent: 4562522 (1985-12-01), Adams et al.
patent: 4593213 (1986-06-01), Vesce et al.
patent: 4710686 (1987-12-01), Guzik
patent: 4827366 (1989-05-01), McNally et al.
patent: 4881014 (1989-11-01), Okochi
patent: 5267137 (1993-11-01), Goebel
patent: 5317254 (1994-05-01), Olson
patent: 5398182 (1995-03-01), Crosby
patent: 5552685 (1996-09-01), Young et al.
patent: 5886889 (1999-03-01), Escallier
Berhane Adolf Deneke
Honeywell International , Inc.
Keith Newburry, Esq.
LandOfFree
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