Electrical transmission or interconnection systems – Plural supply circuits or sources – Connecting or disconnecting
Reexamination Certificate
2000-02-25
2003-04-15
Fleming, Fritz (Department: 2836)
Electrical transmission or interconnection systems
Plural supply circuits or sources
Connecting or disconnecting
C307S010100, C307S010700
Reexamination Certificate
active
06548916
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a power supply system and a power supply method, and particularly to a power supply system in which a semiconductor switch is provided for controlling supply of electrical power from a power supply to a load and driven in response to a drive signal, and a power supply method for controlling the supply of electrical power from a power supply to a load. More specifically, the invention relates to a power supply system and a power supply method for a vehicle.
2. Description of the Related Art
A semiconductor switch used in this type of power supply system is, for example, an n-channel MOSFET (metal oxide semiconductor field-effect transistor). Because of the extremely low on-resistance and low cost of this n-channel MOSFET, it has come to be used in automotive applications.
FIG. 7
shows such a type of power supply system in a vehicle, in which an output voltage from a 12-V power supply
101
is supplied to a load
103
via the drain D and the source S of an n-channel MOSFET
105
, which is a semiconductor switch to be driven for switching.
For use to the drive, an output voltage from the 12-V power supply
101
is supplied via an ON/OFF circuit
107
, where it is switched to be on and off, to a charge pump circuit
109
which is composed of a voltage stepup circuit
111
and an oscillator circuit
113
. The circuit
111
steps up the supplied voltage, and a stepped-up voltage is input to the circuit
113
, where it is based on to generate an oscillating raised voltage of a prescribed frequency, which is output as a control signal to the gate of the n-channel MOSFET
105
, which is thereby driven to switch on and off, supplying electrical power from the 12-V power supply
101
to the load
103
.
As such, in automotive applications, the n-channel MOSFET is often switched on and off at the high side (upstream of a load), where it thus has a gate-source voltage normally raised above an on-voltage, with the need for provision of a charge pump circuit.
Although the power supply system has the advantages of low cost and a low on-resistance, in applications such as use in a vehicle, it requires such extra elements as a charge pump circuit. One example of such application s in an intelligent power system (IPS) that has an n-channel MOSFET with a built-in charge pump circuit and protection circuit, and is expensive.
In addition, the charge pump circuit has an oscillator circuit, which is caused to oscillate at a high frequency (several hundreds of kilohertz) in order to achieve a reduction in size of the power supply system in vehicle. For this reason, there is an increased chance of the oscillator generating noises in the radio of vehicle. This necessitates a circuit to reduce such radio noises, thereby increasing the cost of the power supply system.
While a p-channel MOSFET can also be used on the high side, this p-channel MOSFET has a larger chip than the n-channel MOSFET, and has a higher cost than the n-channel MOSFET to achieve the same performance.
FIG. 8
shows a multiple-voltage power supply system that has not actually been used in a vehicle.
In this power supply system, a voltage (42 V) generated by an alternator
121
is charged to a 36-V battery B
1
via a diode D
1
, and electrical power of the 36-V battery B
1
is supplied to a load
123
, such as a drive motor. The voltage (42 V) generated by the alternator
121
is also converted to 14 V by a DC/DC converter
125
and supplied to a 12-V battery B
2
, and electrical power from the 12-V battery B
2
is supplied to another load
127
, such as a lamp.
By use of a DC/DC converter for conversion from 42 V to 14 V, there is achieved a multiple-voltage system encompassing a battery for 36-V system and a battery for 12-V system, enabling supply of electrical power to both a high-voltage load such as a drive motor and a low-voltage load such as a lamp. The voltage of the 36-V battery is a triple of that of the 12-V battery B
2
, and the supply current of the former is one-third of that of the latter for the same electrical power, enabling the cross-section of conductors in wiring harness associated with the 36-V battery to be made approximately one-third of that of conductors wiring harness associated with the 12-V battery, thereby not only reducing the weight of wire harness, but also improving the load efficiency.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a power supply system and a power supply method that use multiple voltages permitting a simple, low-cost circuit configuration to provide easy on/off control of a load.
The present invention adopts the following configuration in order to achieve the above-noted object.
Specifically, one aspect of the present invention is a power supply system comprising a first power supply having a first supply voltage, a second power supply having a second supply voltage larger than the first supply voltage, a semiconductor switch drivable with the second supply voltage and connected between the first power supply and a load, and a drive circuit using the second supply voltage as a drive signal to drive the semiconductor switch.
According to this aspect, a multi-voltage power supply system allows a semiconductor switch to be driven with a simple, low-cost configuration, for effective supply of power to a load.
Another aspect of the present invention is a power supply system for a vehicle including a load, the power supply system, comprising a first power supply having a first supply voltage, a second power supply having a second supply voltage larger than the first supply voltage, a semiconductor switch drivable with the second supply voltage and connected between the first power supply and the load, and a drive circuit using the second supply voltage as a first drive signal to drive the semiconductor switch.
According to this aspect, in a vehicle having a load, a multi-voltage power supply system allows a semiconductor switch to be driven with a simple, low-cost configuration, for effective supply of power to the load.
Another aspect of the present invention is a power supply system for a vehicle including a motor having first and second electrodes different of polarity, and grounding circuitry, the power supply system comprising a first power supply having a first supply voltage, a second power supply having a second supply voltage larger than the first supply voltage, a first semiconductor switch connected between the first power supply and the first electrode of the motor, a second semiconductor switch connected between the first power supply and the second electrode of the motor, a third semiconductor switch drivable with the second supply voltage and connected between the second electrode of the motor and the grounding circuitry, a fourth semiconductor switch drivable with the second supply voltage and connected between the first electrode of the motor and the grounding circuitry, a first drive circuit configured to drive the first semiconductor switch, a second drive circuit configured to drive the second semiconductor switch, a third drive circuit using the second supply voltage as a drive signal to drive the third semiconductor switch, a fourth drive circuit using the second supply voltage as a drive signal to drive the fourth semiconductor switch, and a controller configured to synchronously control the first, second, third and fourth drive circuits to control a rotating direction of the motor.
According to this aspect, in a vehicle including a motor and grounding circuitry, a multi-voltage power supply system allows a set of semiconductor switches to be synchronously driven with a simple, low-cost configuration, for effective supply of power to the motor.
Another aspect of the present invention is a power supply system which performs on/off control of a semiconductor switch so as to control the supply of electrical power from a first power supply to a load. This power supply system has a second power supply with a second voltage that is larger than
Kanazawa Akiyoshi
Uda Makoto
Fleming Fritz
Yazaki -Corporation
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