Overcurrent protection device

• US 6,465,983 B1
• Filed: 07/30/1998
• Issued: 10/15/2002
• Est. Priority Date: 12/19/1994
• Status: Expired due to Fees

• Current Assignee: Yamaha Hatsudoki Kabushiki Kaisha (Yamaha Corporation)
• Original Assignee: Yamaha Hatsudoki Kabushiki Kaisha (Yamaha Corporation)
• Inventors: Suenari, Masaya, Saito, Mikio, Ogata, Hiroaki
• Primary Examiner(s): Nappi, Robert E.
• Assistant Examiner(s): Duda, Rina I.
• Application Number:
  US08/702,681
• Time in Patent Office: 1,538 Days
• Field of Search: 318/139, 318/599, 318/811, 318/798, 318/825
• US Class Current: 318/811
• CPC Class Codes: H02J 7/2434 with pulse modulation
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/92 Energy efficient charging or discharging systems for batteries, ultracapacitors, supercapacitors or double-layer capacitors specially adapted for vehicles

Abstract

At Step Sb3, a duty factor, which was calculated at Step Sb2 on the basis of a data for a feed-back control, is compared with a limit value of the duty factor. If the duty factor is less than the limit value, a pulse for the PWM control is modulated to have the calculated duty factor at Step Sb4. If the duty factor is greater than the limit value, the pulse for the PWM control is modulated to have the duty factor of the limit value at Step Sb5. Accordingly, the duty factor provided for a current value instruction is not in excess of the limit value, so that the secondary battery is prevented from discharging overcurrent in excess of the limit current which can be discharged from the secondary battery. Accordingly, although the capacitance of the secondary battery is not large, the lifetime of the secondary battery is prevented from being shortened.

Claims

1. A current controlling and overcurrent protection device for controlling a current flow from at least one secondary cell to a motor, said device including a switching means for allowing a current, corresponding to a duty factor of a pulse for a PWM control, to flow to the motor;

current detecting means for detecting the current flowing to the motor and for outputting this detection result;

duty factor calculating means for calculating a duty factor, corresponding to a current value instruction, for adjusting the current flowing to the motor, such that the detection result of the current detecting means is coincident with a target current value which should flow to the motor; and

a pulse generating means for generating a pulse for said PWM control having the duty factor calculated by the duty factor calculating means and for providing the pulse for said switching means, the overcurrent protection being provided by limit calculating means for dividing a limit current value, which can be discharged from the secondary cell, by a dividing value comprised of one of said target current value and the detection result of the current detecting means and means for outputting the division result as a limit value of the said duty factor; and

selection means for comparing the duty factor calculated by the duty factor calculating means with said limit value, said selection means providing the duty factor calculated by the duty factor calculating means for the pulse generating means if the duty factor is less than the limit value and providing said limit value for said pulse generating means if said duty factor is greater than said limit value.

2. An overcurrent protection device according to claim 1 wherein the dividing value comprises the detection result of the current detecting means.

3. An overcurrent protection device according to claim 2, wherein the duty factor calculating means calculates the duty factor at first intervals, and the limit calculating means calculates the limit value at second intervals, the second intervals being prescribed longer than the first intervals.

4. An overcurrent protection device according to claim 1 wherein the dividing value comprises the target current value.

5. An overcurrent protection device according to claim 4, wherein the duty factor calculating means calculates the duty factor at first intervals, and the limit calculating means calculates the limit value at second intervals, the second intervals being prescribed longer than the first intervals.

6. A method for current control and overcurrent protection device for controlling a current flow from at least one secondary cell to a motor, said method comprising switching a current flow corresponding to a duty factor of a pulse for a PWM control flowing to the motor, detecting the current flowing to the motor and for outputting this detection result, calculating a duty factor, corresponding to a current value instruction for adjusting the current flowing to the motor, so that the detection result of the current detection is coincident with a target current value which should flow to the motor, and generating a pulse for the PWM control having the duty factor calculated by the duty factor calculation and providing the pulse for the switching, performing a limit calculation by dividing a limit current value, which can be discharged from the secondary cell, by a dividing value comprised of one of the target current value and the detection result of the current detection, outputting the division result as a limit value of the duty factor, and comparing the duty factor calculated by the duty factor calculation with the limit value, and providing the duty factor calculated by the duty factor calculation for the pulse generation if the duty factor is less than the limit value and providing the limit value for the pulse generating if the duty factor is greater than the limit value.

7. The method according to claim 6 wherein the dividing value comprises the detection result of the current detection.

8. The method according to claim 7, wherein the duty factor calculation is made at first intervals, and the limit calculation is made at second intervals, the second intervals being longer than the first intervals.

9. The method according to claim 6 wherein the dividing value comprises the target current value.

10. The method according to claim 9, wherein the duty factor calculation is made at first intervals, and the limit calculation is made at second intervals, the second intervals being longer than the first intervals.