Dual voltage electrical system

• US 4,743,830 A
• Filed: 01/20/1987
• Issued: 05/10/1988
• Est. Priority Date: 01/20/1987
• Status: Expired due to Fees

• Current Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Original Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Inventors: Lakey, Leroy E.
• Primary Examiner(s): Hickey, R. J.
• Application Number:
  US07/004,486
• Time in Patent Office: 476 Days
• Field of Search: 320/3, 320/6, 320/15-18, 320/35, 320/36, 320/21, 322/90
• US Class Current: 320/104
• CPC Class Codes: H02J 7/1423 with multiple batteries
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

Abstract

A dual voltage motor vehicle electrical system. First and second batteries are series connected across the output terminals of a battery charging generator. A converter is provided that can charge the first battery from the second battery or charge the second battery from the first battery. The voltages across the batteries are sensed and the battery with the lower voltage is charged from the other battery. The system has current limit and temperature limit controls for protecting semiconductor switches that are utilized in the system.

Claims

1. A dual voltage electrical system comprising, a source of direct voltage comprising a generator having direct voltage output terminals, first and second batteries, means connecting said batteries in series across said direct voltage output terminals whereby said batteries can be charged in series from said generator, control means connecting said batteries operative in one mode of operation to charge said first battery from said second battery and operative in a second mode of operation to charge said second battery from said first battery, said control means comprising switching means connected between a respective battery and a battery current supply circuit means, said switching means when conductive connecting one battery to said circuit means, said circuit means operative to supply current to another battery when a switching means is operated nonconductive, and means responsive to the relative terminal voltages of said batteries for selecting one of said first and second modes of operation, said last-named means operative to select a mode of operation wherein the battery having the lower terminal voltage is charged from the other battery.

2. A dual voltage electrical system comprising, a source of battery charging voltage having direct voltage output terminals, first and second batteries connected in series across said direct voltage output terminals, the negative terminal of said first battery and the positive terminal of said second battery being connected together at a first junction, a second junction, an inductor connected between said junctions, a first semiconductor switch connected between the positive terminal of said first battery and said second junction, a first diode connected across said first semiconductor switch, a second semiconductor switch connected between the negative terminal of said second battery and said second junction, a second diode connected across said second semiconductor switch, said inductor being energized by one of said batteries when one of said semiconductor switches is biased conductive, said inductor supplying charging current to a battery through one of said diodes when a semiconductor switch is biased nonconductive, and control means responsive to the voltages across the batteries for causing said first semiconductor switch to switch on and off when the voltage across the second battery is lower than the voltage across the first battery and for causing said second semiconductor switch to switch on and off when the voltage across said first battery is lower than the voltage across the second battery.

3. The electrical system according to claim 2 wherein the means for causing the semiconductor switches to switch on and off comprises a square-wave voltage generator having a constant output frequency.

4. The electrical system according to claim 2 wherein a current sensing means senses the magnitude of current through said inductor and wherein means are provided to bias said semiconductor switches nonconductive when the current through the inductor exceeds a predetermined current limit value.

5. The electrical system according to claim 2 wherein a temperature sensing means senses the temperature of said semiconductor switches and wherein means are provided to bias said semiconductor switches nonconductive when the temperature of a semiconductor switch exceeds a predetermined temperature limit value.

6. A dual voltage electrical system comprising, a direct voltage generator having direct voltage output terminals, first and second batteries series connected across said output terminals, the negative terminal of said first battery and the positive terminal of said second battery being connected together at a first junction, a second junction, an inductor connected between said first and second junctions, a semiconductor switch connected between the positive terminal of said first battery and said second junction, a diode connected between said second junction and the negative terminal of said second battery, said semiconductor switch when conductive causing said first battery to supply current to said inductor, said inductor supplying current to said second battery through said diode when said semiconductor switch is nonconductive, control means responsive to the voltage across said batteries for maintaining said semiconductor switch nonconductive when the voltage across said first battery is lower than the voltage across said second battery and operative to cause said semiconductor switch to be switched conductive and nonconductive when the voltage across said second battery is less than the voltage across said first battery, current sensing means for sensing current flow through said inductor, and means for biasing said semiconductor switch nonconductive when the current through said inductor exceeds a predetermined current limit value.

7. The electrical system according to claim 6 where a temperature sensing means senses the temperature of said semiconductor switch and wherein means are provided for biasing said semiconductor switch nonconductive when the temperature of said semiconductor switch exceeds a predetermined temperature limit value.