Bidirectional current time integration device

• US 4,679,000 A
• Filed: 06/20/1985
• Issued: 07/07/1987
• Est. Priority Date: 06/20/1985
• Status: Expired due to Fees

• Current Assignee: Robert Clark
• Original Assignee: Robert Clark
• Inventors: Clark, Robert
• Primary Examiner(s): Fisenzopf, Reinhard J.
• Assistant Examiner(s): Solis, Jose M.
• Application Number:
  US06/746,751
• Time in Patent Office: 747 Days
• Field of Search: 320/43, 320/44, 340/636, 324/425-428, 324/435, 324/436
• US Class Current: 324/428
• CPC Class Codes: H02J 7/00714 in response to battery charging or discharging current

Abstract

A bidirectional current-time integrator device comprises a shunt for connection in a circuit and an integrating circuit having inputs connected to opposite ends of the shunt through a switching device. The integrating circuit integrates an input signal from the shunt with time to produce a stream of pulses at a frequency proportional to the current with each pulse representing a given unit of current time. A bidirectional counter assembly counts the pulses from the integrating circuit in one direction when the current is in one direction, and in the opposite direction when the current reverses. The integrator circuit includes means for storing any partial unit of current time accumulated whenever the current direction changes and adding that partial unit to the subsequent accumulation of the signal when the current changes back to the original direction. The device may be used as a battery discharge state monitor.

Claims

1. A bidirectional current-time integration device for use in a circuit in which current direction changes repeatedly, the device comprising:

current sensor means connected in series with a circuit in which the current direction changes repeatedly, for producing a source signal proportional to the current through the circuit which changes polarity when the current changes direction;

integrator means which includes an amplifier responsive to said source signal for producing a stream of output pulses at a rate dependent on the magnitude of current through the current sensor means, each pulse representing the accumulation of a given unit of integrated current-time;

bidirectional counter means including a first storage means for accumulating said source signal with time when said current is in one direction and a second storage means for accumulating said source signal when said current is in the opposite direction, said first and second storage means comprise a pair of integration capacitors, and integrator switch means for selectively switching from one storage means to the other storage means each time the current changes direction, said integrator switch means comprises a switch responsive to said current direction for selectively connecting one of said capacitors across said amplifier and disconnecting the other capacitor each time the current changes direction, such that any partial charge on the disconnected capacitor is stored, one of said capacitors being connected across said amplifier when the current is in one direction and the other capacitor being connected across the amplifier when the current is in the opposite direction, said amplifier having inputs from connection to said source signal, polarity reversing switch means being connected across said input and responsive to changes in current direction to reverse the polarity of said amplifier inputs, said first and second storage means storing any partial unit of integrated current-time present on said storage means when disconnected until the next current direction change.

2. The device of claim 1, wherein said integrator means further comprises means for producing output pulses at a rate dependent on the current direction through the sensor means.

3. The device of claim 1 for connection to a battery to monitor the discharge state of the battery, the current sensor means comprising a shunt for connection in circuit with the battery, the integrator means first storage means comprising means for integrating said source signal during battery charging and said second storage means comprising means for integrating said source signal during battery discharging.

4. The device of claim 1, wherein said first and second storage means comprise a pair of integrating circuits, and said integrator switch means comprises means for selectively connecting one of said integrating circuits across said sensor when the current is in one direction and the other of said integrating circuits across said sensor when the current is in the opposite direction, each circuit having a pair of inputs and said integrator switch means further comprising means for tying together the inputs of the disconnected circuit at each current direction change, whereby any partial unit of current time in said disconnected circuit is stored until the next current direction change and added to any further accumulated source signal.

5. The device of claim 4, wherein said bidirectional counter means comprises a first counter for counting pulses corresponding to one current direction and a second counter for counting pulses corresponding to the opposite current direction, one of said integrating circuits having an output connected to said first counter and the other integrating circuit having an output connected to said second counter, the outputs of said counters being connected to an up/down counter for counting up when the current is in one direction and counting down when the current is in the opposite direction.

7. The device of claim 3, wherein the said counter means comprises a first counter for counting said pulses during battery charging and a second counter for counting said pulses during battery discharging, said first counter producing an output pulse in response to a greater number of input pulses than the second counter by an amount equal to the charge retention value of the battery.

8. The device of claim 3, further including compensation means for producing fewer output pulses from said integrator means for the same input signal during charging than during discharging by an amount equivalent to the charge retention value of the battery.

6. A bidirectional current-time integration device for use in a circuit for connection to a battery to monitor the discharge state of the battery in which the current direction changes repeatedly, the device comprising:

current sensor means comprising a shunt for connection in the circuit with the battery connected in series with a circuit in which the current direction changes repeatedly, for producing a source signal proportional to the current through the circuit which changes polarity when the current changes direction;

integrator means comprising an amplifier and a pair of capacitors for selectively connecting across said amplifier during battery charging and discharging, respectfully, responsive to said source signal for producing a stream of output pulses at a rate dependent on the magnitude of the current through the current sensor means, each pulse representing the accumulation of a given unit of integrated current-time;

compensation means for producing fewer output pulses from said integrator means for the same input signal during charging than during discharging by an amount equivalent to the charge retention value of the battery, said compensation means comprising a pair of resistors connected in parallel to one of the inputs of said amplifier;

switch means comprising means for connecting said source signal through a first one of said resistors to said amplifier input during charging and through a second one of said resistors during discharging, said first resistor having a higher value than said second resistor;

bidirectional counter means for counting the output pulses from said integrator means, said counter means being responsive to the current direction to count in one direction while the sensor means current is in one direction and in the opposite direction while the sensor means current is in the opposite direction; and

said integrator means including a first storage means comprising means for integrating said source signal during battery charging and for accumulating said source signal with time when said current is in one direction and a second storage means comprising means for integrating said source signal during battery discharging for accumulating said source signal when said current is in the opposite direction, and integrator switch means for selectively switching from one storage means to the other storage means each time the current changes direction, said first and second storage means storing any partial unit of integrated current-time present on said storage means when disconnected until the next current direction change.

9. The device of claim 6, wherein said second resistor has a value of between 80% and 90% of said first resistor.