Electric power conversion systems – Current conversion – Including d.c.-a.c.-d.c. converter
Patent
1983-02-01
1985-11-12
Wong, Peter S.
Electric power conversion systems
Current conversion
Including d.c.-a.c.-d.c. converter
363 61, H02M 3335
Patent
active
045531960
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
The present invention relates to a power source system for vehicles and, more particularly, to a power source system for a vehicular electronic device, which is equipped with memory-arithmetic units such as a microcomputer.
2. Background Art
Recent automobiles are being equipped with electronic devices, which are required to store and hold data, such as clocks or trip computers. In an electronic device having built therein a memory unit for storing data, if a voltage to be applied for operating an electronic device is blocked or dropped to a level lower than a predetermined value, the storage data held in the memory unit until that block or drop in voltage is lost so that the electronic device which relies for its operation on that data may possibly malfunction or be rendered inoperative. If a clock exemplifies that electronic device, it may indicate an improper time. If a trip meter is another example, it may improperly indicate a running distance, a runnable distance and/or an elapse time.
In the system thus far described, a serious problem for causing the storage data of the memory unit to be lost is a drop of the terminal voltage of a battery at the time of start of the engine. The voltage to be applied to a microcomputer is generally required to be held at about 5.+-.0.5 [V]. For this requirement, the applied voltage is held constant by the action of a constant voltage circuit. If the battery terminal voltage ranges from 6 to 20 [V], the required voltage is ensured in a normal manner so that the voltage to be applied to the microcomputer is held at about 5.+-.0.5 [V]. At the time of start of the engine, however, especially when the engine is started at the time when the ambient temperature is low, the battery terminal voltage is frequently dropped to a level lower than 5 [V] to invite a state in which the voltage to be applied to the microcomputer becomes too low so that the storage data cannot be held. In order to eliminate such problem, there has been adopted in the prior art a method by which the power source is backed up by means of a battery or by which a DC-DC converter is used at all times to boost the voltage. The former method has a defect in that it is required to retain a space for arranging the battery or to maintain the battery. The latter method has a defect that, since the DC-DC converter is operating even when the engine is stopped, the discharge of the battery is so increased that not only the engine cannot be started but also the storage data is lost if the automobile is left as it is for a long time.
DISCLOSURE OF INVENTION
One object of the present invention is to provide a power source system for a vehicular electronic device, which is free from the aforementioned defects while having its power consumption reduced.
Another object of the present invention is to provide a power source system which is able to reliably hold the storage data of a memory unit to be built in a vehicular electronic device.
Still another object of the present invention is to provide a power source system for a vehicular electronic device, which is small, light and inexpensive.
The present invention is characterized in that the power source system of a vehicular electronic device is equipped with control means for controlling a booster circuit. By the action of this control means, the terminal voltage of the battery is applied to the electronic device, without being boosted by the booster circuit, in case the load upon the battery is limited to the electronic device including a memory unit, i.e., in case an ignition switch is left open. As a result, the power to be consumed in the booster circuit can be reduced to reduce the discharge of the battery.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a block diagram showing an embodiment of the present invention;
FIG. 2 is a block diagram showing another embodiment of the present invention;
FIG. 3 is a block diagram showing still another embodiment of the present invention; and
FIG. 4 is a circuit diagram constituting a DC-DC conv
REFERENCES:
patent: 2920259 (1960-01-01), Light
patent: 4224659 (1980-09-01), Iguchi
patent: 4246635 (1981-01-01), Arima
patent: 4315208 (1982-02-01), McElroy et al.
Naito Shotaro
Tokuyama Keiichi
Watanabe Shizuhisa
Hitachi , Ltd.
Jones Judson H.
Wong Peter S.
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