AUTOMATIC BATTERY CHARGING CIRCUIT OPERABLE OVER A WIDE TEMPERATURE RANGE

• US 3,767,995 A
• Filed: 05/17/1972
• Issued: 10/23/1973
• Est. Priority Date: 05/17/1972
• Status: Expired due to Term

• Current Assignee: Brian H. Moisand, Bruce M. Stone, Philip G. Kaminski
• Original Assignee: Brian H. Moisand, Bruce M. Stone, Philip G. Kaminski
• Inventors: Kaminski, Philip G., Moisand, Brian H., Stone, Bruce M.
• Primary Examiner(s): Miller, J. D.
• Assistant Examiner(s): Hickey, Robert J.
• Application Number:
  US05/254,212
• Time in Patent Office: 524 Days
• Field of Search: 320/22,32,33,35,36,39,40,23,24
• US Class Current: 320/125
• CPC Class Codes: H02J 7/007194 of the battery

Abstract

An automatic battery charging and voltage regulating system for connection between a source of voltage and a battery to be charged which battery may have current consuming equipment connected thereto and may have a thermistor attached thereon whose resistance varies in accordance with battery temperature. The system includes a converter coupled to the source of voltage which develops a charging voltage for charging the battery, a current control circuit is coupled to the converter and to the battery and operates to limit the maximum charging current to the battery to a first level if there is no thermistor or if the thermistor resistance exceeds a predetermined amount, and to the second level, if the thermistor resistance is below the predetermined amount. A voltage sensing circuit is also provided which senses the battery voltage in excess of a predetermined level and reduces the charging voltage developed by the converter. A first circuit may also be provided which upon actuation of the current consuming equipment causes the current control circuit to limit the charging current to the first higher maximum charging current.

Claims

1. An automatic battery charging and voltage regulating system connected between a source of voltage and a battery to be charged which battery may have current consuming equipment connected thereto, and may have temperature responsive means attached thereon having a first state in response to a battery temperature below a first level and a second state in response to a battery temperature above said first level, said system including in combination, converter means coupled to said source of voltage for developing a charging voltage therefrom for charging said battery, current control means coupled to said converter means and said battery and operative in response to said charging voltage to supply a charging current to said battery, said current control means being operative to limit said charging current to a first maximum charging current in response to a first control signal coupled thereto, and to a second maximum charging current in response to a second control signal, control circuit means coupled to said current control means and said battery, said control circuit means being operative to develop said first control signal in response to said temperature responsive means having said first state, said control circuit means being further operative to develop said second control signal in response to the absence of said temperature responsive means and in response to said temperature responsive means having said second state, voltage sensing means coupled to said battery and said converter means and operative in response to a battery voltage in excess of a first level to provide a signal to said convertor means to reduce the charging voltage whereby said first or second maximum charging current to said battery is reduced.

2. The system of claim 1 wherein said current control means includes a transistor current limiter.

3. The system of claim 2 wherein said temperature responsive means is a temperature variable resistance means having a resistance less than a first resistance in response to a battery temperature below said first level and a resistance greater than said first resistance in response to a battery temperature above said first level.

4. The system of claim 3 wherein said temperature variable resistance means is a thermistor.

5. A system of claim 4 wherein said control circuit means includes comparison means coupled to said battery and operative to develop a first comparison signal in response to said thermistor having said first state, said comparison means being further operative to develop a second comparison signal in response to the absence of said thermistor and to said thermistor having said second state.

6. The system of claim 5 wherein said comparison means includes first circuit means coupled to said battery, said first circuit means operative to develop a voltage signal above a first voltage in the absence of said thermistor and in response to said thermistor having said second state, and a voltage signal below said first voltage in response to said thermistor having said first state, second circuit means for developing said first voltage, differential amplifier means coupled to said first and second circuit means and responsive to said voltage signal being below said first voltage to develop said first comparison signal and to said voltage signal being above said first voltage to develop said second comparison signal.

7. The system of claim 6 wherein said transistor current limiter includes a transistor having base, emitter and collector electrodes, said emitter electrode being coupled to said converter means, said collector electrode being coupled to said battery, said control circuit means further including third circuit means coupled between said current limiter base and emitter electrodes, said third circuit means operative in response to said first comparison signaL to develop said first control signal thereacross for limiting conduction of said transistor current limiter to said first maximum charging current, and operative in response to said second comparison signal to develop said second control signal thereacross for limiting conduction of said transistor current limiter to said second maximum charging current.

8. The system of claim 7 further including fourth circuit means coupled to said first circuit means and to said current consuming equipment and operative in response to operation of said equipment to maintain said voltage signal below said first voltage whereby said transistor current limiter is operative to supply said first maximum charging current.

9. The system of claim 8 wherein said fourth circuit includes diode means coupled to said first circuit means and said equipment.

10. The system of claim 9 wherein said third circuit means includes first diode means coupled from said transistor current limiter base electrode to said emitter electrode, transistor switch means having first and second principle electrodes and a control electrode, diode means coupled in series with said switch means principle electrodes, said series combination being coupled in parallel with said first diode means, said control electrode being coupled to said differential amplifier means, said switch means being responsive to said first comparison signal to be maintained in a first state whereby said first control signal is developed across said third circuit and to said second comparison signal to be maintained in said second state whereby said second control signal is developed across said third circuit.

11. An automatic battery charging and voltage regulating system connectable between a source of voltage and a battery to be charged which battery may have current consuming equipment connected thereto and temperature variable resistance means attached thereon having a first state wherein said resistance is less than a first resistance in response to a battery temperature below a first level, and a second state wherein said resistance is greater than said first resistance in response to a battery temperature above said first level, said system including in combination, converter means coupled to said source of voltage for developing a charging voltage therefrom for charging said battery, current control means coupled to said converter means and said battery and operative in response to said charging voltage to supply a charging current to said battery, said current control means limiting said charging current to a first maximum charging current in response to a first control signal coupled thereto and to a second, lower maximum charging current in response to a second control signal, control circuit means coupled to said current control means and said battery, said control circuit means being operative to develop said first control signal in response to said temperature variable resistance means having said first state, said control circuit means being further operative to develop said second control signal in response to the absence of said temperature variable resistance means and to said temperature variable resistance means having said second state, first voltage sensing means coupled to said battery and said converter means and operative in response to a battery voltage in excess of a second level to reduce the charging voltage of said converter means whereby said charging current to said battery is reduced, and first circuit means coupled to said control circuit means and said equipment and operative in response to operation of said equipment to cause said control circuit means to develop said first control signal whereby said current control means is operative to supply said first maximum charging current.

12. The system of claim 11 further including second voltage sensing means coupled to said converter means and responsive to a charging voltage in excess of a third level to reduce the charging voltage developed theReby whereby said charging current to said battery is reduced.

13. The system of claim 12 wherein said first circuit means includes diode means coupled to said control circuit means and said equipment.

14. The system of claim 13 wherein said first voltage sensing means includes voltage reference means for developing a reference voltage, transistor means coupled to said voltage reference means said battery and said converter means, said transistor means operative in response to said battery voltage exceeding said voltage reference to reduce the charging voltage of said converter means.

15. The system of claim 14 wherein said second voltage sensing means includes second voltage reference means for developing a second reference voltage, second transistor means coupled to said second voltage reference means and to said converter means, said second transistor means operative in response to said charging voltage exceeding said second reference voltage to reduce the charging voltage of said converter means.

16. The system of claim 15 wherein said control circuit means includes comparison means coupled to said battery and operative to develop a first comparison signal in response to said temperature variable resistance means having said first state, said comparison means being further operative to develop a second comparison signal in response to the absence of said temperature variable resistance means and to said temperature variable resistance means having said second state.

17. The system of claim 16 wherein said comparison means includes second circuit means coupled to said battery, said second circuit means operative to develop a voltage signal above a first voltage in the absence of said temperature variable resistance means and in response to said temperature variable resistance means having said second state, and a voltage signal below said first voltage in response to said temperature variable resistance means having said first state, third circuit means for developing said first voltage, differential amplifier means coupled to said second and third circuit means and responsive to said voltage signal being below said first voltage to develop said first comparison signal and to said voltage signal being above said first voltage to develop said second comparison signal.

18. The system of claim 17 wherein said current control means includes a transistor current limiter having base, emitter and collector electrodes, said emitter electrode being coupled to said converter means, said collector electrode being coupled to said battery, said control circuit means further including fourth circuit means coupled between said current limiter base and emitter electrodes, said fourth circuit means operative in response to said first comparison signal to develop said first control signal thereacross for limiting conduction of said transistor current limiter to said first maximum charging current, and operative in response to said second comparison signal to develop said second control signal thereacross for limiting conduction of said transistor current limiter to said second lower maximum charging current.

19. The system of claim 18 wherein said fourth circuit means includes, first diode means coupled from said transistor current limiter base electrode to said emitter electrode, transistor switch means having first and second principle electrodes and a control electrode, diode means coupled in series with said principle electrodes, said series combination being coupled in parallel with said first diode means, said control electrode being coupled to said differential amplifier means, said transistor switch means being responsive to said first comparison signal to be maintained in a first state whereby said first control signal is developed across said fourth circuit means and responsive to said second comparison signal to be maintained in a second state whereby said second control signal is developed across said fourth circuit means.

20. The system of claim 19 wherEin said converter means includes astable multivibrator means coupled to said source of voltage and operative to switch between a first and second state, and inverter means coupled to said source of voltage to said astable multivibrator means and to said current control means, said inverter means operative in response to said astable multivibrator means changing from a first to a second state to develop said charging voltage.

21. The system of claim 20 further including indicator means coupled between said current control means collector electrode and said battery, said indicator means being operative to indicate when said charging current is above and below said second lower maximum charging current.