Electrical transmission or interconnection systems – Plural supply circuits or sources – Diverse or unlike electrical characteristics
Reexamination Certificate
2000-03-23
2001-12-25
Nguyen, Matthew (Department: 2838)
Electrical transmission or interconnection systems
Plural supply circuits or sources
Diverse or unlike electrical characteristics
Reexamination Certificate
active
06333570
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of priority based on German Application No. 19913131.7, filed on Mar. 23, 1999, which is incorporated by reference herein in its entirety.
BACKGROUND OF THE INVENTION
The invention relates to a power supply system with two batteries of different voltages and at least one load device which is connected in parallel with both batteries, such that if one battery fails, the other battery assures the supply of power. Such duplicate power supplies are gaining interest in areas such as automobiles, where it is necessary to assure operation of apparatus critical to safety.
FIG. 4
shows a block circuit diagram of a conventional power supply system. Voltage terminals
2
and
4
of an electronic control apparatus
6
are connected each through fuses
8
and
10
, respectively, to batteries
12
and
14
, respectively. Battery
12
in the example shown has a voltage of 12 V and battery
14
has a voltage of 42 V. Each voltage terminal leads to power supply centers
16
and
18
, respectively, which are matched to a particular battery voltage. Each power supply center is connected to an electronic control unit
20
whose output signal operates, through an output
22
, a switch
24
which is contained in a unit
26
to be controlled by the control apparatus
6
.
The power is supplied to the unit
26
via power supply lines
28
and
30
, each connected to one of the two batteries
12
and
14
, respectively, and connected by diodes
32
and
34
, respectively, to the input terminal of switch
24
.
A ground conductor
36
runs from the battery
14
to the ground connection of the control apparatus
6
and to the ground connection of the unit
26
. The ground of battery
12
is connected by an additional ground line, which can be the vehicle body itself, to the ground of the control apparatus
6
.
The operation of this conventional power supply system is well known in the art. If either of the two batteries
12
or
14
fails, the remaining battery supplies the power. The diodes
32
and
34
and/or the power supply centers provide assurance that current flows only from the operational battery to the unit
26
and prevents the occurrence of a short circuit discharge.
In order to reduce cost and weight, and to improve safety, it is desirable to eliminate the additional ground connection
36
, which is typically designed with a large cross section.
Additionally, the diagnosis of the two separate grounds can be difficult and is prone to errors.
A short circuit in the lines of connected units or sensors (not shown) should have as little effect as possible on the operation of the overall system.
Another conventional power supply system is disclosed in DE 196 02 171 A1. According to this power supply system, the power input of a voltage regulator is connected through a double diode to both a main line connected to the positive pole of a battery and to a secondary line which is connected through an ignition switch to the positive pole of the on-board network. A buffer condenser is connected to the secondary line and all grounds of the system are brought together. In the event of a voltage collapse on the main line, the power is supplied through the secondary line with current flowing from the buffer condenser. If the voltage on the secondary line collapses, power is supplied through the buffer condenser, which is of sufficient size to buffer the power input.
Yet another conventional power supply system is disclosed in DE 196 45 944 A1. This power supply system contains a controller for an on-board network with at least two batteries which serve to power various load devices. The controller is between the two batteries and contains a power supply center which is connected through diodes to the two batteries. The system has a common ground. The controller also has a bidirectional connection for a bus, such as a CAN bus.
In the event of interruptions of the ground connection between the batteries, failures, which are difficult to diagnose, can occur in the load device of the conventional power supply systems described above.
SUMMARY OF THE INVENTION
The present invention provides for a power supply system with improved operating reliability.
The present invention also provides a power supply that assures power is supplied in the event of a battery failure, and when the ground connections between the batteries on the one hand and the load on the other hand fail, the load is supplied with the voltage difference between the batteries.
With the power supply system according to the present invention, a supply of power is assured in the event of virtually all individual failures. If a failure occurs in the ground of the load device, the potential applied to this device is increased by the smaller battery voltage. The battery of weaker voltage is then charged by the supply current.
In the case of a motor vehicle, the ground terminals of both batteries can be common with the car body. Individual failures in power lines do not lead to a loss of function. With a simple voltage measurement or threshold circuit, the lines can be diagnosed with a trouble signal at which time the car can be taken to a service shop.
The invention is applicable wherever load devices are supplied with current by two batteries of different voltage, so that power will be supplied even if one battery fails or there is another problem. The invention is especially advantageous when used in motor vehicles where numerous safety-critical load devices are to be supplied with power with maximum reliability (e.g., electronic motor controls, airbags, etc.).
The present invention is achieved by providing a power supply system. The system comprises a first battery connected to a first line at a first voltage relative to ground; a second battery connected to a second line at a second voltage relative to ground; a load device having a third line adapted to be connected to one of the first and second lines and having a fourth line adapted to be connected to ground; and a set of diodes associated with the load device. The set of diodes includes a first diode permitting current flow from the first line to the third line when the first voltage is greater than the second voltage; a second diode permitting current flow from the second line to the third line when the second voltage is greater than the first voltage; a third diode permitting current flow from the fourth line to the second line when i) the first voltage is greater than the second voltage and ii) the fourth line is disconnected from ground; and a fourth diode permitting current flow from the fourth line to the first line when i) the second voltage is greater than the first voltage and ii) the fourth line is disconnected from ground.
The present invention is also achieved by providing a power supply system for connecting a first battery and a second battery to a load device. Each of the batteries has a positive terminal and a negative terminal, and the load device has an inlet and an outlet. The system comprises a first diode having a first anode adapted to be connected to the positive terminal of the first battery and a first cathode adapted to be connected to the input of the load device; a second diode having a second anode adapted to be connected to the positive terminal of the second battery and a second cathode adapted to be connected to the input of the load device; a third diode having a third anode adapted to be connected to the output of the load device and a third cathode adapted to be connected to the positive terminal of the first battery; and a fourth diode having a fourth anode adapted to be connected to the output of the load device and a fourth cathode adapted to be connected to the positive terminal of the second battery.
The present invention is further achieved by providing a method of supplying power from first and second batteries to a load device. The first battery has a first voltage relative to ground, the second battery has a second voltage relative to ground, and the load device has an inlet
Nguyen Matthew
Siemens Aktiengesellschaft
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