Electricity: power supply or regulation systems – In shunt with source or load – Using choke and switch across source
Reexamination Certificate
2000-12-20
2001-11-20
Sterrett, Jeffrey (Department: 2838)
Electricity: power supply or regulation systems
In shunt with source or load
Using choke and switch across source
C323S224000, C323S225000, C323S271000, C307S010100, C307S046000, C307S065000, C307S066000, C307S075000
Reexamination Certificate
active
06320358
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to energy management systems and particularly but not exclusively to such systems for motor vehicles employing dual voltage electrical schemes.
BACKGROUND OF THE INVENTION
Many motor vehicle electrical systems are now being designed with a dual voltage schemes requiring two batteries having nominal voltages of 14V and 42V (12V and 36V rated batteries respectively) as shown in FIG.
1
. The 12V battery
40
typically has a high amp-hour rating and is used to provide energy to 14V loads
50
such as lighting circuits and other circuits which are difficult to implement at higher voltages. The 36V battery
80
typically has a high cranking current capability and is coupled to a 42V generator and higher voltage loads
70
, which may include the engine starter motor.
In the event that one or other of these batteries becomes depleted of charge, there is a need to transfer power between them in a bidirectional manner. In order to do this, it is known to provide a conventional bidirectional DC-DC converter
60
, coupled between the 12V battery
50
and the 36V battery
80
. The bidirectional DC-DC converter
60
acts as a step-down converter (right to left in
FIG. 1
) or a step-up converter (left to right in
FIG. 1
) through switching charge through an inductor in a well known manner.
An external ‘start aid’ post
10
is also provided, to enable an external means of charging the batteries. A switch
30
switches between the start aid post
10
and the 12V battery
40
, and a fuse and diode arrangement
20
is coupled between the switch
30
and the start aid post
10
. When a positive DC voltage is applied to the start aid post
10
, the switch
30
isolates the 12V battery
40
and the DC voltage is coupled through the fuse and diode arrangement
20
to charge the 36V battery
80
via the bidirectional DC-DC converter
60
. When the DC voltage is removed from the start aid post
10
, the switch
30
isolates the start aid post
10
and re-couples the 12V battery
40
to the bidirectional DC-DC converter
60
, whereupon (if necessary) the 12V battery
40
is charged by the 36V battery
80
via the bidirectional DC-DC converter
60
.
FIG. 2
shows the internal architecture of the bi-directional DC-DC converter
60
, which has a first path
100
coupled to the 36V battery
80
(not shown), a second path
170
coupled to the 12V battery
40
(not shown), first and second switches
130
and
150
respectively and an inductor
140
. The first and second switches
130
and
150
respectively are coupled in series between the first path
100
and earth. The inductor
140
is coupled between the second path
170
and a node between the first and second switches
130
and
150
respectively. The switches are switched by control logic in one of two ways: to transfer energy from the first path
100
to the second path
170
(step-down); and to transfer energy from the second path
170
to the first path
100
(step-up). Both of these are achieved by switching charge through the inductor
140
.
A problem with this arrangement is that for it to function correctly as a step-up converter, the first path
100
(and hence the
36
battery
80
) must be at a higher potential than the second path
170
, otherwise the intrinsic body diode
135
of the first switch
130
will conduct. Therefore if the 36V battery
80
is faulty, greatly discharged or replaced by a new battery, and therefore has a voltage less than that of the 12V battery
40
(or the start aid post
10
, if appropriate), then the current flow will be uncontrolled, with potentially catastrophic results. It is possible to prevent this current flow by adding another switch in inverse series with the first switch
130
, but this would still not enable charging in this state. This problem is compounded by the emergence of vehicles with an exclusively 42V electrical system, because such vehicles cannot be used to provide a jump-start via the start aid post
10
.
A further problem is that by adding an additional switch the DC-DC converter
60
, the circuit of
FIG. 1
would require 7 MOSFETs (metal-oxide semiconductor field-effect transistors), as the changeover switch in the start aid post
10
requires 2 sets of inverse series MOSFETs, in addition to the three required in the DC-DC converter
60
.
There is therefore a need for a more flexible arrangement which enables a two-battery vehicle to re-charge either battery from the other, and which also provides improved flexibility for to charge and be charged via a start aid post.
This invention seeks to provide a DC-DC converter and energy management system which mitigate the above mentioned disadvantages.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention there is provided a DC-DC converter for use with an energy management system of a motor vehicle, comprising: first and second voltage supply terminals having first and second nominal voltages respectively, at least one of the first and second voltage supply terminals being arranged for coupling to a battery; and a third voltage supply terminal for exchanging energy with an external energy means; wherein the DC-DC converter is arranged to exchange energy between the first or second voltage supply terminals and the third voltage supply terminal independent of the voltage and polarity of the external energy means.
According to a second aspect of the present invention there is provided an energy management system for a motor vehicle, comprising: first and second voltage supply terminals having first and second nominal voltages respectively; at least one battery coupled to at least one of the first and second voltage supply terminals; a universal bi-directional DC-DC converter coupled between the first and second voltage supply terminals for exchanging energy therebetween; and a third voltage supply terminal for exchanging energy between the DC-DC converter and an external energy means; wherein the energy exchanged between the first or second voltage supply terminals and the third voltage supply terminal is independent of the voltage and polarity of the external energy means.
Preferably the universal bi-directional DC-DC converter comprises five switches, an inductor and control logic arranged such that energy is exchanged via step-up and step-down conversion from the first to the second voltage supply terminal and from the second to the first voltage supply terminal. The switches of the universal bidirectional DC-DC converter are preferably implemented using Metal Oxide Semiconductor Field Effect Transistors, and preferably at least two of the Metal Oxide Semiconductor Field Effect Transistors are implemented as a pair of inverse series transistors.
Preferably the external energy means is an electrical system of another vehicle, such that the energy management system is coupled to exchange energy with the electrical system of the other vehicle. The exchange of energy is preferably the charging of a battery of the electrical system of the other vehicle by the energy management system. Alternatively the exchange of energy is the charging of the at least one battery by the electrical system of the other vehicle.
Alternatively the external energy means is preferably a battery charger coupled to charge the energy management system. Preferably the nominal voltages of the first and second voltage supply terminals are 12 volts and 36 volts respectively.
In this way an energy management system is provided for a two-battery vehicle in which either battery may be re-charged from the other, and in which a start aid post may also be used to charge one or other battery and be charged by one or other battery, irrespective of voltage or polarity. The system is also simply implemented with a minimum number of switches.
REFERENCES:
patent: 3105910 (1963-10-01), Chambers
patent: 4161023 (1979-07-01), Goffeau
patent: 4736151 (1988-04-01), Dishner
patent: 4801859 (1989-01-01), Dishner
patent: 5194799 (1993-03-01), Tomantschger
patent: 5488283 (1996-01-01), Dougherty et al.
patent: 5633577 (199
Motorola Inc.
Sterrett Jeffrey
LandOfFree
Bidirectional energy management system independent of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Bidirectional energy management system independent of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Bidirectional energy management system independent of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2586999