Microcomputer-equipped system and battery pack for electric power tool

• US 20100063757A1
• Filed: 08/27/2009
• Published: 03/11/2010
• Est. Priority Date: 09/05/2008
• Status: Active Grant

• Current Assignee: Makita Corporation
• Original Assignee: Makita Corporation
• Inventors: Suzuki, Hitoshi
• Granted Patent: US 8,265,890 B2
• Time in Patent Office: Days
• US Class Current: 702/63
• CPC Class Codes: H02J 7/00 Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries

Abstract

A microcomputer-equipped system for electric power tool includes a microcomputer, a reference voltage generator, a reference data storage unit, and a first determiner. The microcomputer includes an analog-to-digital (AD) converter and at least one AD port. The reference voltage generator generates and inputs to the AD port a reference voltage having a predetermined value. The reference data storage unit prestores reference data corresponding to the reference voltage. The first determiner compares diagnostic data obtained by AD conversion by the AD converter of the reference voltage inputted to the AD port with the reference data to determine, in case that difference between the diagnostic data and the reference data is out of a predefined allowable range, that an AD abnormal state has occurred in which a correct result of the AD conversion is unable to be obtained from the AD converter.

Claims

1. A microcomputer-equipped system for electric power tool, the system comprising:

a microcomputer that includes an AD (analog-to-digital) converter and at least one AD port to which an analog signal to be AD converted by the AD converter is inputted;

a reference voltage generator that is separately provided from an operation power source of the microcomputer and generates and inputs to the AD port a reference voltage having a predetermined value;

a reference data storage unit that prestores reference data which is digital data corresponding to the reference voltage;

a first determiner that is provided inside the microcomputer and compares diagnostic data obtained by AD conversion by the AD converter of the reference voltage inputted to the AD port with the reference data stored in the reference data storage unit to determine, in case that difference between the diagnostic data and the reference data is out of a predefined allowable range, that an AD abnormal state has occurred in which a correct result of the AD conversion is unable to be obtained from the AD converter.

2. The microcomputer-equipped system for electric power tool according to claim 1, wherein

the reference voltage generator receives a predefined voltage of the operation power source supplied to the microcomputer, and generates the reference voltage lower than the predefined voltage of the operation power source.

3. The microcomputer-equipped system for electric power tool according to claim 2, further comprising:

a resetting unit that outputs a reset signal to the microcomputer when the voltage of the operation power source of the microcomputer becomes a predefined lower limit or smaller, wherein

the microcomputer is configured such that its operation is initialized when the reset signal is inputted from the reset unit, and

the reference voltage generator generates as the reference voltage a voltage that is smaller than the lower limit and capable of being AD converted by the AD converter.

4. The microcomputer-equipped system for electric power tool according to claim 1, wherein

the reference voltage generator includes a diode, and is configured to generate as the reference voltage a forward voltage of the diode generated by applying a forward bias to the diode by a power inputted to the reference voltage generator.

5. The microcomputer-equipped system for electric power tool according to claim 1, further comprising:

a signal voltage divider that is provided on a signal path till where the analog signal to be AD converted is inputted to the AD converter, and generates a diagnostic analog signal by voltage division of the analog signal at a predefined voltage dividing ratio when an execution command is inputted;

a command output unit that is provided inside the microcomputer and outputs to the signal voltage divider the execution command for directing the signal voltage divider execute the voltage division or a stop command for keeping the signal voltage divider from executing the voltage division; and

a second determiner that is provided inside the microcomputer, obtains diagnostic data by directing the command output unit output the execution command to execute the voltage division by the signal voltage divider and directing the AD converter AD convert the diagnostic analog signal obtained by the voltage division, obtains comparative data by directing the command output unit output the stop command to stop the voltage division by the signal voltage divider and directing the AD converter AD convert the analog signal, compares the obtained diagnostic data and the comparative data, and determines that the AD abnormal state has occurred when the diagnostic data and the comparative data do not satisfy a relation corresponding to the voltage dividing ratio in the signal voltage divider.

6. The microcomputer-equipped system for electric power tool according to claim 5, wherein

a signal input circuit including at least one resistor connected in series is provided on the signal path till where the analog signal to be AD converted is inputted to the AD port, and

the signal voltage divider is provided on the signal path from the signal input circuit to the AD converter, and generates the diagnostic analog signal by the voltage division of the analog signal to be AD converted inputted to the signal input circuit at the voltage dividing ratio when the execution command is inputted.

7. The microcomputer-equipped system for electric power tool according to claim 6, wherein

the signal voltage divider includes:

a voltage dividing resistor, one end of which is electrically connected to the AD port; and

a voltage division controller that makes the other end of the voltage dividing resistor electrically open when the stop command is inputted, and electrically connect the other end of the voltage dividing resistor to a region having a lower potential than the one end when the execution command is inputted, so as to pass a current to the voltage dividing resistor for the voltage division.

8. The microcomputer-equipped system for electric power tool according to claim 7, wherein

the voltage division controller includes a switch that establishes/interrupts conduction between the other end side of the voltage dividing resistor and a ground potential, interrupts the conduction between the other end side of the voltage dividing resistor and the ground potential by turning off the switch when the stop command is inputted, and grounds the other end side of the voltage dividing resistor by turning on the switch when the execution command is inputted.

9. The microcomputer-equipped system for electric power tool according to claim 5, wherein

a discharging circuit including a positive side resistor, a negative side resistor, and a switching unit is connected to at least one of the battery cells, one end of the positive side resistor being connected to a positive terminal of the battery cell, one end of the negative side resistor being connected to a negative terminal of the battery cell, the switch unit being connected to the other ends of the respective resistors, and establishing/interrupting conduction between the other ends of the resistors in accordance with the execution command and the execution command from the microcomputer,

the microcomputer is configured to monitor a voltage of the battery cell based on a result of AD conversion by the AD converter of a voltage outputted from the other end side of the positive side resistor to the AD port when the conduction between the other ends of the resistors is interrupted by the switching unit,

the discharging circuit functions as the signal voltage divider, and is configured to turn off the switching unit to directly output a voltage of the positive terminal of the battery cell to the AD port through the positive side resistor when the stop command is inputted, and to turn on the switching unit to divide the voltage of the positive terminal of the battery cell at the voltage dividing ratio by the respective resistors constituting the discharge circuit and generate the diagnostic analog signal when the execution command is inputted.

10. A battery pack for electric power tool comprising:

at least one battery cell, and

the microcomputer-equipped system for electric power tool according to claim 1, wherein

a battery voltage signal directly or indirectly indicating a voltage of at least one of the battery cells to the battery cell is configured to be inputted to the AD port as the analog signal to be AD converted, and

the microcomputer monitors a state of the battery cell based on a result of the AD conversion by the AD converter of the battery voltage signal.

11. A battery pack for electric power tool comprising:

at least one battery cell, and

the microcomputer-equipped system for electric power tool according to claim 5, wherein

a battery voltage signal directly or indirectly indicating a voltage of at least one of the battery cells to the battery cell is configured to be inputted to the AD port as the analog signal to be AD converted, and

the microcomputer monitors a state of the battery cell based on a result of the AD conversion by the AD converter of the battery voltage signal.

12. A battery pack for electric power tool comprising:

at least one battery cell, and

the microcomputer-equipped system for electric power tool according to claim 5, wherein

a discharging circuit including a positive side resistor, a negative side resistor, and a switching unit is connected to at least one of the battery cells, one end of the positive side resistor being connected to a positive terminal of the battery cell, one end of the negative side resistor being connected to a negative terminal of the battery cell, the switch unit being connected to the other ends of the respective resistors, and establishing/interrupting conduction between the other ends of the resistors in accordance with the execution command and the execution command from the microcomputer,

the microcomputer is configured to monitor a voltage of the battery cell based on a result of AD conversion by the AD converter of a voltage outputted from the other end side of the positive side resistor to the AD port when the conduction between the other ends of the resistors is interrupted by the switching unit,

the discharging circuit functions as the signal voltage divider, and is configured to turn off the switching unit to directly output a voltage of the positive terminal of the battery cell to the AD port through the positive side resistor when the stop command is inputted, and to turn on the switching unit to divide the voltage of the positive terminal of the battery cell at the voltage dividing ratio by the respective resistors constituting the discharge circuit and generate the diagnostic analog signal when the execution command is inputted.

13. A battery pack for electric power tool comprising:

at least one battery cell, and

the microcomputer-equipped system for electric power tool according to claim 5, wherein

a discharging circuit including a positive side resistor, a negative side resistor, a switching unit, and a voltage dividing resistor, and a voltage detector are connected to at least one of the battery cells, one end of the positive side resistor being connected to a positive terminal of the battery cell, one end of the negative side resistor being connected to a negative terminal of the battery cell, the switch unit being connected to the other end of the respective resistors, and establishing/interrupting conduction between the other ends of the resistors in accordance with the execution command and the execution command from the microcomputer, the voltage dividing resistor being provided in series with the switching unit between the other end of the respective resistors,

the microcomputer is configured to monitor a voltage of the battery cell based on a result of AD conversion by the AD converter of a voltage outputted from the voltage detector to the AD port when the conduction between the other ends of the resistors is interrupted by the switching unit,

the discharging circuit functions as the signal voltage divider, and is configured to turn off the switching unit so that the voltage of the battery cell is directly inputted to the voltage detector when the stop command is inputted, and to turn on the switching unit to divide the voltage of the battery cell at the voltage dividing ratio by the respective resistors constituting the discharge circuit so that an output from the voltage detector to the divided voltage is generated as the diagnostic analog signal when the execution command is inputted.

14. The battery pack for electric power tool according to claim 10, wherein

the at least one battery cell is a rechargeable battery.

15. The battery pack for electric power tool according to claim 14, further comprising:

a charging power input terminal through which a charging power for charging the rechargeable battery is inputted; and

an interrupter that is provided on a charging power supply path from the charging power input terminal to the rechargeable battery and is capable of interrupting the charging power supply path by an interruption command from the microcomputer, wherein

the microcomputer, when it is determined by the first determiner that the AD abnormal state has occurred, outputs the interruption command to direct the interrupter interrupt the charging power supply path.

16. The battery pack for electric power tool according to claim 11, wherein

the at least one battery cell is a rechargeable battery.

17. The battery pack for electric power tool according to claim 16, further comprising:

a charging power input terminal through which a charging power for charging the rechargeable battery is inputted; and

an interrupter that is provided on a charging power supply path from the charging power input terminal to the rechargeable battery and is capable of interrupting the charging power supply path by an interruption command from the microcomputer, wherein

the microcomputer, when it is determined by the second determiner that the AD abnormal state has occurred, outputs the interruption command to direct the interrupter interrupt the charging power supply path.