Electricity: power supply or regulation systems – Output level responsive – Using a three or more terminal semiconductive device as the...
Reexamination Certificate
2002-12-16
2004-07-13
Sterrett, Jeffrey (Department: 2838)
Electricity: power supply or regulation systems
Output level responsive
Using a three or more terminal semiconductive device as the...
C323S267000, C363S065000, C363S072000
Reexamination Certificate
active
06762595
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a power distribution system which can be mounted in various vehicles including motor vehicles, and more particularly to a power distribution system for distributing and supplying electric power to various electric loads in a vehicle.
As an example of conventional vehicles, a motor vehicle in which a 14-V output power supply unit having an alternator and a rechargeable 12-V battery is mounted (i.e., a so-called 14-V vehicle) is known. A power distribution system which is applied to this 14-V vehicle is comprised of a junction box for receiving the power supply of a high voltage (e.g., 14 V) from the power supply unit, as well as a plurality of electronic control units electrically connected to this junction box through a plurality of power lines. Incorporated in each electronic control unit is a series regulator which receives the high-voltage power distributed from the junction box through a power line. In this power distribution system, the electric power of a high voltage in the junction box is converted to electric power of a low voltage (e.g., 5 V) by each series regulator which functions as a voltage converting unit, and the electric power of the low voltage thus converted is supplied to a plurality of electric loads which are electrically connected to each electronic control unit.
In recent years, development of high-voltage vehicles in which a power supply unit with a 42-V output having a motor/generator and a rechargeable 36-V battery is mounted and which is advantageous in fuel consumption (i.e., so-called 42-V vehicles) is underway. If the above-described power distribution system is applied to this 42-V vehicle, the conversion efficiency is extremely poor, and the generation of large heat entails. This is primarily because the difference between the input voltage value and the output voltage value of the series regulator is large. If the output voltage (i.e., the voltage for the electric load) of the series regulator is specifically assumed to be 5 V, for example, the conversion efficiency of the series regulator in the 14-V vehicle becomes approx. 35.7% from the arithmetic expression (100%−((14 V−5 V)/14 V×100%)), whereas the conversion efficiency of the series regulator in the 42-V vehicle becomes approx. 11.9% from the arithmetic expression (100%−((42 V−5 V)/42 V×100%)). Namely, if the output voltage at the series regulator is assumed to be fixed, the higher the input voltage at the series regulator, the more the conversion efficiency drops, which causes heat to be generated in various elements in the series regulator. For this reason, it is conceivable to incorporate a switching regulator in each electronic control unit instead of the series regulator as the voltage converting unit exhibiting higher conversion efficiency than the series regulator.
However, in the case of the switching regulator for supplying power to an electric load whose power consumption changes substantially between an active state and a standby state in such as an electronic control unit for a keyless entry system, if the design is made such that the conversion efficiency becomes high when the electric load is heavy (i.e., at the time of the active state when the load current is large), the conversion efficiency at the time when the electric load is light (i.e., at the time of the standby state when the load current is very small) is poor. With such a switching regulator, even in a case where a very small load current (i.e., standby current) is supplied to an electric load in the standby state, there is a large amount of unwanted dark current due to its poor conversion efficiency, which results in large power consumption of the battery and is therefore undesirable. To solve this problem, it is conceivable to provide a power distribution system in which all the electronic control units requiring standby current are provided with a standby-current supplying unit, and power is supplied by the switching regulator at the time when an ignition switch is on (i.e., in the active state), where as power is supplied by a standby-current supplying unit when the ignition switch is off (i.e., in the stand by state).
However, in such a power distribution system, the respective electronic control units need to be provided with expensive switching regulators, and all the electronic control units requiring standby current need to be further provided with the standby-current supplying unit. Therefore, there is a problem in that the power distribution system becomes very expensive.
FIG. 11
shows a power distribution system disclosed in JP-A-10-84626. As shown in
FIG. 11
, a voltage converting unit
52
is provided in a junction box
51
to which electric power of a high voltage is supplied from a power supply unit
50
, this voltage converting unit
52
converts the electric power of a high voltage to electric power of a low voltage (e.g., 5 V), and the electric power of the low voltage is collectively distributed to respective electronic control units
53
. According to this power distribution system, since it suffices to provide at least one voltage converting unit
52
, it is possible to structure a low-cost power distribution system.
However, in the conventional power distribution system shown in
FIG. 11
, if power is supplied from the voltage converting unit
52
to distantly located electric loads, a voltage drop is liable to occur, and if consideration is given to the arrangement of the voltage converting unit
52
so that power will not be distantly supplied to electric loads, the number of a voltage converting unit
52
increases and results in higher cost. Furthermore, the voltage converting unit
52
must be designed so that the accuracy of the output voltage, temperature characteristics, and the like of the voltage converting unit
52
conform to the electric load whose requirements are most stringent among the plurality of electric loads. To design the voltage converting unit so as to satisfy the stringent requirements leads to the higher cost of the power distribution system.
Since variations are likely to occur in the output from the voltage converting unit
52
owing to the increase and decrease of the load current, it is difficult to supply electric power of high accuracy to a plurality of electric loads. In a case where power is supplied from the voltage converting unit
52
to an electric load whose power consumption varies substantially between the active state and the standby state as in, for example, the electronic control unit for a keyless entry system or the like, if the design is made such that the conversion efficiency of the voltage converting unit
52
becomes high at the time of the active state when the load current is large, the conversion efficiency at the time of the standby state when the load current is very small is poor. In such a voltage converting unit
52
, even in the case where a very small standby current is supplied to the electric load in the standby state, there is a large amount of unwanted dark current due to its poor conversion efficiency, which results in large power consumption of the battery and is therefore undesirable.
SUMMARY OF THE INVENTION
The invention has been devised in view of the above-described problems, and its object, among others, is to provide a power distribution system which is capable reducing the unwanted dark current.
In order to solve the aforesaid object, the invention is characterized by having the following arrangement.
(1) A power distribution system comprising:
an upper power distribution unit connected to a power supply unit through a high-voltage power line for receiving power supply of a high voltage from the power supply unit;
a plurality of lower power distribution units connected to the upper power distribution unit through a plurality of intermediate-voltage power lines for receiving from the upper power distribution unit power supply of an intermediate voltage lower than the high voltage, converting the intermediate voltage
Hasegawa Tetsuya
Tamai Yasuhiro
Sterrett Jeffrey
Sughrue & Mion, PLLC
Yazaki -Corporation
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