CHARGE REGULATOR AND MONITOR FOR SPACECRAFT SOLAR CELL/BATTERY SYSTEM CONTROL
First Claim
1. In combination with spacecraft electrical power system including a spacecraft, a battery aboard said spacecraft, charging source means for supplying charging current to said battery, and an electrical load for drawing discharge current from said battery, a first resistance means disposed internal to said spacecraft, a second resistance means disposed external to said spacecraft, each of said first and second resistance means being connected electrically to said charging source means in circuit multiple with said battery and being effective when supplied with energy in the form of current from said charging source means to dissipate said energy as heat, means for measuring the internal temperature of said spacecraft, and shunt control means responsive to said temperature measuring means for selectively energizing said first and second resistance means with current from said charging source means to maintain a substantially constant temperature internal to said spacecraft.
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Abstract
An electronic system for providing fully automatic control of a spacecraft solar cell/battery electrical power system, including the provision of continuous telemetry monitoring of the battery charge state. Circuitry accurately measures, on an ampere-minute basis, the charging and discharging of the battery and functions to maintain the battery in a fully charged condition, with a provision for automatic reduction of the charge current to a temperature-dependent trickle value when the proper amount of charge has been returned to the battery after a previous discharge. A bipolar charge quantizer circuit is utilized to monitor battery charge and discharge operations and includes a finite time integrator circuit capable of supplying an output signal pulse each time the battery is charged or discharged by a predetermined amount. The quantizer is designed with a predetermined offset factor to account for battery inefficiency. Temperature dependent maximum battery voltage limiting and maximum charge current limiting are also provided, along with means which operate to automatically shunt excess electrical power from the solar cell array into the spacecraft instrument package in order to provide temperature control therein.
118 Citations
9 Claims
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1. In combination with spacecraft electrical power system including a spacecraft, a battery aboard said spacecraft, charging source means for supplying charging current to said battery, and an electrical load for drawing discharge current from said battery, a first resistance means disposed internal to said spacecraft, a second resistance means disposed external to said spacecraft, each of said first and second resistance means being connected electrically to said charging source means in circuit multiple with said battery and being effective when supplied with energy in the form of current from said charging source means to dissipate said energy as heat, means for measuring the internal temperature of said spacecraft, and shunt control means responsive to said temperature measuring means for selectively energizing said first and second resistance means with current from said charging source means to maintain a substantially constant temperature internal to said spacecraft.
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2. The combination specified in claim 1 wherein, said battery is mounted internal to said spacecraft, said charging source means is a solar cell array, and said temperature measuring means is a thermistor disposed adjacent said battery.
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3. The combination specified in claim 2 further including, means responsive to the charging and discharging current to and from said battery for producing a first signal proportional to the magnitude of said charging and discharging current, means responsive to said first signal for producing an output signal pulse demarcating each time said battery has either been charged or discharged by a predetermined amount of electrical charge, a reversible digital counter operably connected to receive and register a count of the output signal pulses producEd by said pulse producing means, control means effective when said battery is being charged to cause said reversible digital counter to count in a first direction and effective when said battery is being discharged to cause said reversible digital counter to count in a second opposite direction, whereby the count registered by said digital counter is continuously indicative of the state of charge and discharge of said battery, means for monitoring the voltage existing across said battery relative to a predetermined desired battery voltage value, and means for monitoring the charging current being supplied to said battery relative to a predetermined desired maximum charging current value, said shunt control means being responsive to said battery voltage and charging current monitoring means for selectively energizing said first and second resistance means with current from said charging source means when said battery voltage exceeds said desired voltage value and when said charging current exceeds said desired maximum value.
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4. The combination specified in claim 18, wherein, said output signal pulse producing means includes a finite time integrator circuit means for integrating the charge and discharge current of said battery and producing an output signal pulse of one polarity each time said battery has been charged by said predetermined amount and an output signal pulse of opposite polarity each time said battery has been discharged by said predetermined amount, and said control means includes circuit means responsive to the polarity of the output signal pulse produced by said finite time integrator circuit means for supplying a control signal to said digital counter effective to control the counting direction of said digital counter means.
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5. The system specified in claim 4 further including trickle charge control means rendered effective when said battery is fully charged to supply an offset control signal to said integrator means effective to offset the operating state of said integrator means and cause the charging current supplied to said battery to be reduced to a selected trickle charge level.
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6. The system specified in claim 3 further including trickle charge control means rendered effective when said battery is in a fully charged condition for reducing the charging current being applied to said battery by said charging source means to a selected trickle charge current level.
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7. The system specified in claim 6 wherein said selected trickle charge current level is dependent upon the temperature measured by said thermistor.
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8. The system specified in claim 3 further including efficiency offset means operably connected to said output signal pulse producing means and render effective when said battery is being charged to adjust each output signal pulse then produced to account for inefficiency of the battery during charging.
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9. The system specified in claim 4 further including efficiency offset means rendered effective when said battery is being charged to offset said finite time integrator circuit means for adjusting each output signal pulse then produced by said integrator circuit means to account for battery inefficiency during charging.
Specification