Monitor circuits for battery charging and other applications

• US 5,036,284 A
• Filed: 01/16/1990
• Issued: 07/30/1991
• Est. Priority Date: 01/16/1990
• Status: Expired due to Fees

• Current Assignee: Frank J. Cichanski
• Original Assignee: Frank J. Cichanski
• Inventors: Cichanski, Frank J.
• Primary Examiner(s): Wieder, Kenneth A.
• Assistant Examiner(s): Mueller, Robert W.
• Application Number:
  US07/465,378
• Time in Patent Office: 560 Days
• Field of Search: 324/426, 324/427, 324/433, 324/434, 324/435, 320/48, 340/636
• US Class Current: 324/433
• CPC Class Codes: G01R 19/16542 for batteries charge condition monitoring in G01R31/36

Abstract

A monitoring circuit for a battery charger, with utility in other applications, includes a main input that receives an initial signal such as the terminal voltage of a battery being charged, and a two-stage comparator, each stage preferably an operational amplifier. The initial signal is applied to the inverting input of the first stage, which is a differencing amplifier that also serves as a gain block; the initial signal is also delayed a brief interval, typically more than a second, and then applied to the non-inverting input of the first stage of the comparator. The inverting input of the second stage of the comparator receives the same signal as the non-inverting input to the first stage, whereas the non-inverting input to the second stage is derived from the output of the first stage. The output of the second stage varies in amplitude and polarity to define trends in the initial signal direction and magnitude and, in a battery charger, allows accurate charging to a peak with virtually no overcharge or undercharge problems.

Claims

1. A charge monitor circuit for monitoring variations in the terminal voltage of an electrical energy storage device comprising one or more storage cells in order to control charging of the storage device from a charge circuit supplying a charging current thereto, at least by interrupting the charging current when the storage device reaches a predetermined state of charge, the monitor circuit comprising:

a main input, connectable to the storage device, for receiving an initial signal indicative of the present terminal voltage of the storage device;

comparator circuit means, having first and second inputs and an output, for comparing two input signals to develop an output signal representative of the relationship between the two input signals;

first connection means for connecting the main input to the first input of the comparator circuit means to apply the initial signal thereto;

delay means for delaying a signal for a predetermined brief time interval;

and second connection means for connecting the main input through the delay means to the second input of the comparator circuit means to apply a delayed initial signal thereto;

the comparator output being connectable to the charge circuit.

2. A charge monitor circuit for control of charging of an electrical energy storage device, according to claim 1, in which the comparator circuit means comprises:

an initial stage comprising a differencing amplifier which includes the first and second inputs for the comparator circuit means and an intermediate signal output;

and a secondary stage comprising a comparator amplifier having two inputs, one connected to the intermediate signal output and the other to a selected one of the first and second inputs of the comparator circuit means.

3. A charge monitor circuit for control of charging of an electrical energy storage device, according to claim 2, in which the selected one of the first and second inputs of the comparator circuit means is the second input thereof.

4. A charge monitor circuit for control of charging of an electrical energy storage device, according to claim 3, in which the initial stage of the comparator circuit means is a gain block having substantial gain.

5. A charge monitor circuit for control of charging of an electrical energy storage device, according to claim 3, in which each stage of the comparator circuit means is an operational amplifier, and in which:

the initial signal is applied to the one input of the operational amplifier in the initial stage;

the delay means is connected to the other input of the initial stage amplifier and to the one input of the operational amplifier in the secondary stage;

and the intermediate signal output is connected to the other input of the secondary amplifier.

6. A charge monitor circuit for control of charging of an electrical energy storage device, according to claim 5, in which:

the one input of the operational amplifier in each stage of the comparator circuit means is its inverting input.

7. A charge monitor circuit for control of charging of an electrical energy storage device, according to claim 5, and further comprising:

an input resistor R2 in series with the one input to the initial stage;

and a feedback resistor R3 connected from the intermediate signal output back to the one input of the initial stage;

and R3>

R2.

8. A charge monitor circuit for control of charging of an electrical energy storage device, according to claim 7, in which:

the one input of the operational amplifier in each stage of the comparator circuit means is its inverting input.

9. A charge monitor circuit for control of charging of an electrical energy storage device, according to claim 7, in which the one input to the initial stage is returned to a reference potential through a shunt resistor, and the shunt resistor is very much larger than the series input resistor.

10. A charge monitor circuit for control of charging of an electrical energy storage device, according to claim 9, in which:

the one input of the operational amplifier in each stage of the comparator circuit means is its inverting input.

11. A charge monitor circuit for control of charging of an electrical energy storage device, according to claim 10, and further comprising:

a filter circuit, interposed between the main input and the first and second connection means, for filtering out any pulsations in the initial signal prior to its application to the first input of the comparator circuit means or to the delay means;

an initial stage comprising a differencing amplifier which includes the first and second inputs for the comparator circuit means and intermediate signal output;

and a secondary stage comprising a comparator amplifier having two inputs, one connected to the intermediate signal output and the other to a selected one of the first and second inputs of the comparator circuit means;

a buffer amplifier interposed between the filter circuit and the first and second connection means;

and a diode connected in parallel with the delay means so that the preliminary delay, upon initiation of the initial signal, is foreshortened in time to provide for an accelerated response by the comparator circuit means.

12. A charge monitor circuit for control of charging of an electrical energy storage device, according to claim 2, in which the connection between the initial and secondary stages comprises a hysteresis network to preclude false triggering of the secondary stage.

13. A charge monitor circuit for control of charging of an electrical energy storage device, according to claim 12, in which the selected one of the first and second inputs of the comparator circuit means is the second input thereof;

in which each stage of the comparator circuit means is an operational amplifier, and in which;

the initial signal is applied to the one input of the operational amplifier in the initial stage;

the delay means is connected to the other input of the initial stage amplifier and to the one input of the operational amplifier in the secondary stage;

the intermediate signal output is connected to the other input of the secondary stage amplifier;

and the one input of the operational amplifier in each stage of the comparator circuit means is its inverting input.

14. A charge monitor circuit for control of charging of an electrical energy storage device according to claim 1, and further comprising:

a filter circuit, interposed between the main input and the first and second connection means, for filtering out any pulsations in the initial signal prior to its application to the first input of the comparator circuit means or to the delay means.

15. A charge monitor circuit for control of charging of an electrical energy storage device, according to claim 14, in which the comparator circuit comprises:

an initial stage comprising a differencing amplifier which includes the first and second inputs for the comparator circuit means and an intermediate signal output;

and a secondary stage comprising a comparator amplifier having two inputs, one connected to the intermediate signal output and the other to a selected one of the first and second inputs of the comparator circuit means;

and further comprising a buffer amplifier interposed between the filter circuit and the first and second connection means.

16. A charge monitor circuit for control of charging of an electrical energy storage device, according to claim 15, in which the selected one of the first and second inputs of the comparator circuit means is the second input thereof,

in which each stage of the comparator circuit means is an operational amplifier, and in which:

the initial signal is applied to the one input of the operational amplifier in the initial stage;

the delay means is connected to the other input of the initial stage amplifier and to the one input of the operational amplifier in the secondary stage;

and the intermediate signal output is connected to the other input of the secondary stage amplifier;

the one input of the operational amplifier in each stage of the comparator circuit means being its inverting input.

17. A charge monitor circuit for control of charging of an electrical energy storage device, according to claim 1, and further comprising a diode connected in parallel with the delay means so that the preliminary delay, upon initiation of the initial signal, is foreshortened in time to provide for an accelerated repsonse by the comparator circuit means.

18. A charge monitor circuit for control of charging of an electrical energy storage device, according to claim 17, in which the comparator circuit means comprises:

an initial stage comprising a differencing amplifier which includes the first and second inputs for the comparator circuit means and an intermediate signal output;

and a secondary stage comprising a comparator amplifier having two inputs, one connected to the intermediate signal output and the other to a selected one of the first and second inputs of the comparator circuit means.

19. A charge monitor circuit for control of charging of an electrical energy storage device, according to claim 18, in which the selected one of the first and second inputs of the comparator circuit means is the second input thereof,

in which each stage of the comparator circuit means is an operational amplifier, and in which:

the initial signal is applied to the one input of the operational amplifier in the initial stage;

the delay means is connected to the other input of the initial stage amplifier and to the one input of the operational amplifier in the secondary stage;

and the intermediate signal output is connected to the other input of the secondary stage amplifier;

the one input of the operational amplifier in each stage of the comparator circuit means being its inverting input.

20. A monitor circuit for monitoring variations in an initial signal with respect to direction and amplitude, as a function of time comprising:

a main input for receiving an initial signal;

comparator circuit means, having first and second inputs and an output, for comparing two signals to develop an output signal representative of the relationship between the two input signals;

first connection means for connecting the main input to the first input of the comparator circuit means to apply the initial signal thereto;

delay means for delaying a signal for a predetermined brief time interval;

and second connection means for connecting the main input through the delay means to the second input of the comparator circuit means to apply a delayed initial signal thereto.

21. A monitor circuit according to claim 20, in which the comparator circuit means comprises:

an initial stage comprising a differencing amplifier which includes the first and second inputs for the comparator circuit means and an intermediate signal output;

and a secondary stage comprising a comparator amplifier having two inputs, one connected to the intermediate signal output and the other to a selected one of the first and second inputs of the comparator circuit means.

22. A monitor circuit according to claim 21, in which the selected one of the first and second inputs of the comparator circuit means is the second input thereof, and in which:

the initial signal is applied to the one input of the operational amplifier in the initial stage;

the delay means is connected to the other input of the initial stage amplifier and to the one input of the operational amplifier in the secondary stage;

and the intermediate signal output is connected to the other input of the secondary stage amplifier.

23. A charge monitor circuit for control of charging of an electrical energy storage device, according to claim 22, in which:

the one input of the operational amplifier in each stage of the comparator circuit means is its inverting input; and

the initial stage of the comparator circuit means is a gain block having substantial positive gain.

24. A monitor circuit according to claim 22, and further comprising:

an input resistor R2 in series with the one input to the initial stage;

and a feedback resistor R3 connected from the intermediate signal output back to the one input of the initial stage;

and R3>

R2.

25. A monitor circuit according to claim 24, in which the one input to the initial stage is returned to a reference potential through a shunt resistor, and the shunt resistor is very much larger than the series input resistor.

26. A monitor circuit according to claim 21, in which the connection between the initial and secondary stages comprises a hysteresis network to preclude false triggering of the secondary stage.

27. A monitor circuit according to claim 20, and further comprising:

a filter circuit, interposed between the main input and the first and second connection means, for filtering out any pulsations in the initial signal prior to its application to the first input of the comparator circuit means or to the delay means.

28. A monitor circuit according to claim 20 and further comprising a diode connected in parallel with the delay means so that the preliminary delay, upon initiation of the initial signal, is foreshortened in time to provide for an accelerated response by the comparator circuit means.