Battery power circuit

• US 20050099155A1
• Filed: 11/18/2003
• Published: 05/12/2005
• Est. Priority Date: 01/24/2003
• Status: Active Grant

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Okuda, Tatsuya, Urakabe, Takahiro
• Granted Patent: US 7,023,107 B2
• Time in Patent Office: Days
• US Class Current: 320/107
• CPC Class Codes: F02N 11/0866 comprising several power sources, e.g. battery and capacitor or two batteries
• CPC Class Codes: F02N 2011/0885 Capacitors, e.g. for additional power supply
• CPC Class Codes: F02N 2011/0888 DC/DC converters
• CPC Class Codes: F02N 2200/063 Battery voltage
• CPC Class Codes: F02N 2250/02 Battery voltage drop at start, e.g. drops causing ECU reset
• CPC Class Codes: F02N 2300/106 Control of starter current
• CPC Class Codes: H02J 7/1438 in combination with power supplies for loads other than batteries
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

Abstract

A power circuit for a battery for, even when an idle-stop operation is continuously performed, preventing reduction of an electric power supplied to a motor at start-up to obtain a set engine rpm. The power circuit includes a series-connected power supply in which a battery having a load and a capacitor group are connected in series with each other, a DC/DC converter for shifting electric power between the battery and the capacitor group, and between the battery and the load, and a controller for controlling the DC/DC converter. The controller detects the voltage of the capacitor group, and when the voltage detected is lower than a first threshold voltage, controls the DC/DC converter so that the capacitor group is charged with electricity.

Claims

1. A power circuit for a battery comprising:

a first energy storage source;

a second energy storage source connected in series with the first energy storage source;

a DC/DC converter for converting electric power between the first energy storage source and the second energy storage source; and

control means for controlling the DC/DC converter, wherein

the control means detects voltage of the one of the first and second energy storage sources that is disposed on a high voltage side, as the high voltage side energy storage source, and

when the voltage detected is lower than a first threshold voltage, the control means charges the high voltage side energy storage source through the DC/DC converter.

2. The power circuit for a battery according to claim 1, wherein the control means detects the voltage of the high voltage side energy storage source, and when the voltage detected is lower than the first threshold voltage, keeps an engine running and does not perform an engine stopping operation.

3. A power circuit for a battery according to claim 1, wherein the control means detects the voltage of the high voltage side energy storage source, and when the voltage detected is lower than the first threshold voltage, charges the high voltage side energy storage source through the DC/DC converter while keeping an engine running, and when the voltage detected is higher than the first threshold voltage, stops the engine.

4. The power circuit for a battery according to claim 1, wherein the control means detects voltage of the first energy storage source and voltage of the second energy storage source, and adjusts the first threshold voltage in accordance with the voltage of the one of the first and second energy storage sources that is disposed on a low voltage side.

7. The power circuit for a battery according to claim 1, wherein the control means detects voltage of the one of the first and second energy storage sources disposed on a low voltage side, as the low voltage side energy storage source, and when the voltage detected at the low voltage side energy storage source is smaller than a second threshold voltage, increases the first threshold voltage.

5. A power circuit for a battery connected to an electric motor through an electric conversion circuit comprising:

a first energy storage source;

a second energy storage source connected in series with the first energy storage source;

a DC/DC converter for converting electric power between the first energy storage source and the second energy storage source; and

control means for controlling the DC/DC converter, wherein, when the electric motor in a stop state is started, the control means detects a voltage of the one of the first and second energy storage sources that is disposed on a high voltage side, as the high voltage side energy storage source, and adjusts electric power output by the DC/DC converter in accordance with the voltage detected.

6. The power circuit for a battery according to claim 5, wherein the control means detects voltage of the one of the first and second energy storage sources that is disposed on a low voltage side, as the low voltage side energy storage source, and when voltage detected at the low voltage side energy storage source is no larger than a second threshold voltage, controls output of the DC/DC converter so that current of the low voltage side energy storage source is minimized.

8. A power circuit for a battery, comprising:

a first energy storage source;

a second energy storage source connected in series with the first energy storage source, the second energy storage source having an allowable input current larger than a permissible input current of the first energy storage source;

an electric power conversion circuit for converting electric power between an electric motor which is connected to an axle of a vehicle and the first energy storage source and the second energy storage source;

a DC/DC converter for converting electric power between the first energy storage source and the second energy storage source; and

control means for controlling the DC/DC converter, wherein the control means includes DC/DC converter control means for, when regenerative electric power generated by the electric motor charges the first energy storage source and the second energy storage source through the electric power conversion circuit, controlling the DC/DC converter so that an input current to the first energy storage source does not exceed the permissible input current of the first energy storage source.

9. The power circuit for a battery according to claim 8 further comprising:

a vehicle speed sensor for detecting vehicle speed of a vehicle;

a braking command unit for issuing a braking command in accordance with which braking is applied to the vehicle with a braking force; and

a first voltmeter for detecting terminal voltage of the first energy storage source, wherein

the control means comprises;

input current calculation means for calculating the regenerative electric power generated based on the vehicle speed detected and the braking force, and for calculating an input current with which the regenerative electric power charges the first energy storage source and the second energy storage source without an electric power shift in the DC/DC converter; and

allowable input current calculation means for obtaining a state-of-charge (SOC) of the first energy storage sources based on the terminal voltage of the first energy storage source, to calculate an allowable input current to the first energy storage source, based on the SOC; and

when the regenerative electric power charges the first energy storage source and the second energy storage source through the electric power conversion circuit, the DC/DC converter control means controls, when the input current obtained from the input current calculation means is larger than the allowable input current obtained from the allowable input current calculation means, the DC/DC converter so that the regenerative electric power is shifted from the first energy storage source to the second energy storage source.

10. The power circuit for a battery according to claim 9, wherein, when the regenerative electric power charges the first energy storage source and the second energy storage source through the electric power conversion circuit, the DC/DC converter control means controls, when the input current obtained from the input current calculation means is not larger than the allowable input current obtained from the allowable input current calculation means, the DC/DC converter so that the regenerative electric power is shifted from the second energy storage source to the first energy storage source.

11. The power circuit for a battery according to claim 8 further comprising:

a vehicle speed sensor for detecting vehicle speed of a vehicle;

a braking command unit for issuing a braking command in accordance with which braking is applied to the vehicle with a braking force; and

a first voltmeter for detecting terminal voltage of the first energy storage source, wherein

the control means comprises input current calculation means for calculating a regenerative electric power generated based on the vehicle speed detected and the braking force, and for calculating an input current with which the regenerative electric power charges the first energy storage source and the second energy storage source without an electric power shift in the DC/DC converter; and

when the regenerative electric power charges the first energy storage source and the second energy storage source through the electric power conversion circuit, the DC/DC converter control means controls, when the input current obtained from the input current calculation means is larger than a value set in advance, the DC/DC converter so that the electric power is shifted from the first energy storage source to the second energy storage source, and controls, when the input current obtained from the input current calculation means does not exceed a value set in advance, the DC/DC converter so that the electric power is shifted from the second energy storage source to the first energy storage source.

12. The power circuit for a battery according to claim 9 further comprising:

a second voltmeter for detecting terminal voltage of the second energy storage source; and

a brake mechanism connected to an axle of the vehicle for mechanically braking rotation of the axle, wherein the control means comprises

regeneration-enabling electric power calculation means for, when the electric power is shifted from the first energy storage source to the second energy storage source through the DC/DC converter, calculating a regeneration-enabling electric power that can be regenerated in the first energy storage source and the second energy storage source based on the terminal voltage of the first energy storage source and the terminal voltage of the second energy storage source, and

mechanical brake control means for, when the regenerative electric power obtained from the input current calculation means is larger than the regeneration-enabling electric power, calculating a mechanical brake operation quantity based on difference between the regenerative electric power and the regeneration-enabling electric power, and for controlling the brake mechanism based on the mechanical brake operation quantity.

13. The power circuit for a battery according to claim 12, wherein the second energy storage source includes a capacitor, and when the regenerative electric power charges the first energy storage source and the capacitor through the electric power conversion circuit, the DC/DC converter control means controls the DC/DC converter so that an applied voltage become no larger than an allowable applied voltage of the capacitor.