DC to DC voltage converter

• US 20030173940A1
• Filed: 03/12/2002
• Published: 09/18/2003
• Est. Priority Date: 03/12/2002
• Status: Active Grant

• Current Assignee: Credo Technology Corporation (Robert Bosch GmbH)
• Original Assignee: S-B Power Tool Company (Robert Bosch GmbH)
• Inventors: Kovarik, Illya, Neumann, Peter W.
• Granted Patent: US 6,727,679 B2
• Time in Patent Office: Days
• US Class Current: 323/282
• CPC Class Codes: H02J 2207/20 Charging or discharging characterised by the power electronics converter
• CPC Class Codes: H02M 3/155 using semiconductor devices only

Abstract

A DC-DC voltage converter that is capable of increasing as well as decreasing the voltage of a battery pack for application to a power tool or other load. The converter thereby enables different voltage batteries to be used with power tools that have motors that operate at different voltages. The voltage conversion is accomplished by using a relatively high speed switching circuit wherein the duty cycle of the switching circuitry varies the output voltage. An alternative embodiment utilizes feedback control circuitry to automatically adjust the duty cycle so that the speed of the motor, which is a function of the voltage applied to it, would be held generally constant.

Claims

1. A DC to DC voltage converter circuit for use with power tools having a motor operable with DC voltage power and at least one battery having positive and ground terminals for supplying power to the converter circuit at a predetermined voltage, the converter circuit providing power at one or more desired operating voltages and comprising:

a ground line connecting the battery ground terminal to the motor;

a capacitor connected in parallel with the motor;

a switching transistor having a first terminal connected to the battery positive terminal via a diode and a second terminal connected to one end of an inductor that has its other end connected to ground, and a switching control third terminal that can switch the transistor into and out of conduction responsive to switching signals being applied thereto;

a controller for generating and applying said switching signals to said third terminal, said switching signals having an adjustable frequency and an adjustable duty cycle of conduction and non-conduction within a predetermined range;

wherein said controller can provide switching signals that cause said converter circuit to supply power at desired operating voltages that are selectively above and below said predetermined voltage.

2. A DC to DC voltage converter circuit as defined in claim 1 wherein said diode has an anode and a cathode, said anode being connected to the motor and the capacitor, and said cathode being connected to said one end of said inductor and to said second terminal of said switching transistor.

3. A DC to DC voltage converter circuit as defined in claim 1 wherein said switching transistor is a NPN transistor and said first terminal is the collector, the second terminal is the emitter and the third terminal is the base.

4. A DC to DC voltage converter circuit as defined in claim 1 wherein said controller can vary said duty cycle within the range of about 10 percent to about 90 percent.

5. A DC to DC voltage converter circuit as defined in claim 1 wherein said controller can generate switching signals at frequencies within the range of about 50 kHz to about 200 kHz.

6. A DC to DC voltage converter circuit as defined in claim 1 wherein each tool has coding means associated with it that indicates the desired DC operating voltage of the tool, said controller being operatively connected to the coding means when the tool is connected to the converter circuit and can determine the desired DC operating voltage of the tool and thereafter provide said switching signals to cause said converter circuit to supply power at the desired operating voltage.

7. A DC to DC voltage converter circuit as defined in claim 6 wherein said coding means comprises a coding resistor having a value that specifies a desired operating voltage.

8. A DC to DC voltage converter circuit for use with one or more power tools, each of which have a motor that can be driven by a particular DC drive voltage, the circuit being connectable to at least one battery having positive and ground terminals for supplying power to the converter circuit at a predetermined voltage, the converter circuit having an output for connection to the motor and being capable of providing power at its output at the particular drive voltage that is selectively above or below the predetermined voltage, said converter circuit comprising:

a switching transistor having a first terminal connected to the battery positive terminal via a diode, a second terminal connected to one end of an inductor and to the cathode of a diode, and a third terminal that can switch the transistor into and out of conduction responsive to switching signals being applied thereto;

a capacitor having one end connected to the anode of said diode and to a first terminal of the motor and its opposite end connected to a second terminal of the motor;

a ground line connecting the battery ground terminal to said second terminal of the motor;

a controller for generating switching signals having an adjustable frequency and an adjustable duty cycle of conduction and non-conduction and applying said switching signals to said third terminal, said within a predetermined range;

wherein said controller can provide switching signals that cause said converter circuit to selectively supply power at its output at drive voltages that are above and below said predetermined voltage as a function of the frequency and duty cycles generated.

9. A DC to DC voltage converter circuit as defined in claim 8 wherein said switching transistor is a NPN transistor and said first terminal is the collector, the second terminal is the emitter and the third terminal is the base.

10. A DC to DC voltage converter circuit as defined in claim 8 wherein said controller can vary said duty cycle within the range of about 10 percent to about 90 percent.

11. A DC to DC voltage converter circuit as defined in claim 8 wherein said controller can generate switching signals at frequencies within the range of about 50 kHz to about 200 kHz.

12. A DC to DC voltage converter circuit as defined in claim 8 wherein each tool has coding means associated with it that indicates the desired DC drive voltage of the tool, said controller being operatively connected to the coding means when the tool is connected to the converter circuit and can determine the desired DC drive voltage of the tool and thereafter provide said switching signals to cause said converter circuit to supply power at the desired drive voltage.

13. A DC to DC voltage converter circuit as defined in claim 12 wherein said coding means comprises a coding resistor having a value that specifies a desired drive voltage.

14. A DC to DC voltage converter circuit for use with power tools having a motor with first and second terminals, the motor being capable of being driven by DC power supplied at a desired operating voltage, the circuit being connectable to at least one battery having positive and ground terminals for supplying power thereto at a predetermined voltage, the converter circuit providing power at one or more desired operating voltages and comprising:

a first capacitor connected in parallel with the battery;

an inductor having a plurality of internal windings and two ends, one end of said inductor being connected to the positive terminal of the battery and to the first capacitor;

a second capacitor connected in parallel with the first and second terminals of the motor;

a diode having a first terminal connected to the other end of said inductor and a second terminal connected to the first terminal of the motor and to said second capacitor;

a switching transistor having a first terminal connected to either the other end of said inductor or an internal winding thereof and to the battery positive terminal via a diode and a second terminal connected to one end of an inductor that has its other end connected to ground, and a switching control third terminal that can switch the transistor into and out of conduction responsive to switching signals being applied thereto;

a ground line connecting the battery ground terminal to the second terminal of the motor, the second terminal of the switching transistor, and the first and second capacitors;

a controller for generating and applying said switching signals to said third terminal, said switching signals having a predetermined frequency and an adjustable duty cycle of conduction and non-conduction within a predetermined range;

wherein said controller can provide switching signals that cause said converter circuit to selectively supply power at desired operating voltages that are at or above said predetermined voltage.

15. A DC to DC voltage converter circuit as defined in claim 14 wherein said duty cycle can be varied within the range of about 10 percent to about 90 percent.

16. A DC to DC voltage converter circuit as defined in claim 14 wherein said switching signals have a frequency within the range of about 50 kHz to about 200 kHz.

17. A DC to DC voltage converter circuit as defined in claim 14 wherein said controller is operatively connected to monitor the voltage applied to the motor, said controller having an adjustable voltage setting control, said controller varying the duty cycle of said switching signal to thereby vary said operating voltage being applied to the motor for the purpose of maintaining said voltage setting at its set position.

18. A DC to DC voltage converter circuit as defined in claim 17 wherein said controller includes a line connected to said first terminal of the motor for monitoring the voltage applied thereto.

19. A DC to DC voltage converter circuit as defined in claim 14 wherein said first terminal of said diode is an anode and said second terminal is a cathode.

20. A DC to DC voltage converter circuit for use with one or more power tools each having a motor that can be driven by a desired operating DC voltage that may be different for different motors, the circuit being connectable to at least one battery having positive and ground terminals for supplying power to the converter circuit at a predetermined voltage, the converter circuit having an output for connection to the motor and being capable of providing power at a desired operating voltage that is selectively at or above the predetermined voltage, said converter circuit comprising:

a first capacitor connected in parallel with the battery;

inductor means having first and second ends and a plurality of windings, said first end being connected to the positive terminal of the battery and to the first capacitor;

a second capacitor connected in parallel with first and second terminals of the motor;

a diode having a cathode and an anode, said anode being connected to said second end of said inductor and said cathode being connected to the first terminal of the motor and to said second capacitor;

a switching transistor having a first terminal connected to one of said windings or said second end of said inductor and to the anode of said diode and a second terminal connected to ground, and a switching control third terminal that can switch the transistor into and out of conduction responsive to switching signals being applied thereto;

a ground line connecting the battery ground terminal to the second terminal of the motor, said second terminal of said switching transistor, and said first and second capacitors;

a controller for generating and applying said switching signals to said third terminal, said switching signals having an adjustable duty cycle of conduction and non-conduction within a predetermined range that causes said converter circuit to selectively supply power at voltages that are at or above said predetermined voltage;

said controller being operatively connected to monitor the voltage applied to the motor and having an adjustable voltage setting adjuster for establishing a set position, said controller varying the duty cycle of said switching signal to thereby vary said operating voltage being applied to the motor for the purpose of maintaining said voltage setting at its set position.

21. A DC to DC voltage converter circuit as defined in claim 20 wherein each tool has coding means associated with it that indicates the desired DC operating voltage of the tool, said controller being operatively connected to the coding means when the tool is connected to the converter circuit and can determine the desired DC operating voltage of the tool and thereafter provide said switching signals to cause said converter circuit to supply power at the desired operating voltage.

22. A DC to DC voltage converter circuit as defined in claim 21 wherein said coding means comprises a coding resistor having a value that specifies a desired operating voltage.