BILATERAL POWER CONDITIONER FOR SPACECRAFT

• US 3,816,804 A
• Filed: 05/29/1973
• Issued: 06/11/1974
• Est. Priority Date: 05/29/1973
• Status: Expired due to Term

• Current Assignee: Gilbert I. Cardwell Jr
• Original Assignee: Gilbert I. Cardwell Jr
• Inventors: Cardwell, Gilbert I. Jr.
• Primary Examiner(s): Pellinen, A. D.
• Application Number:
  US05/365,296
• Time in Patent Office: 378 Days
• Field of Search: 307/44,48,51,52,60,64,66 320/4,5,9,10,11,14,20,33,39,40,43,45,50 323/8,15,20,DIG.1
• US Class Current: 320/102
• CPC Class Codes: B64G 1/425 Power storage
• CPC Class Codes: B64G 1/428 Power distribution and management
• CPC Class Codes: B64G 1/443 Photovoltaic cell arrays
• CPC Class Codes: H02J 1/10 Parallel operation of dc sources
• CPC Class Codes: H02J 7/35 with light sensitive cells
• CPC Class Codes: Y10S 320/11 Prioritized supply of power or power supply compensation

Abstract

A system, especially useful in near earth orbiting spacecraft, that either allows the craft'"'"''"'"'s solar panel to charge the vehicle'"'"''"'"'s battery at a relatively high but controlled charge rate while supplying a minimum voltage to the satellite'"'"''"'"'s busconnected load, or that switches from the charge mode to a discharge mode so that the battery either shares the voltage supply function to the load or totally supplies at least a minimum bus voltage when the solar panel is in eclipse. The system includes separate charge and discharge power switches that are alternately operative in conjunction with a filter with switching periods determined by duty cycle modulator and depending for such alternate operation and switch periods on a control circuit which sense the bus voltage, the battery condition and the battery charge current.

Claims

1. In a system for charging a battery from a solar panel arrangement connected to a bus, and for discharging the battery into a bus-connected load when the power for the load is not being supplied by the solar panel arrangement, the improvement comprising:

filter means for filtering currents passing therethrough in opposite first and second directions;

charge power switch means operatively coupled to said battery and to said filter means for allowing charging current originating at said solar panel arrangement to controllably pass therethrough and through said filter means in said first direction to said battery only when said system is in a charge mode of operation;

discharge power switch means operatively coupled to said battery and to said filter means for allowing battery discharge current to controllably pass therethrough and through said filter means in said second direction to said bus only when said system is in a discharge mode of operation;

duty cycle modulator means operatively coupled to said charge power switch means and to said discharge power switch means for controlling the duty cycle of operation of said charge power switch means and said discharge power switch means in response to modulator control feedback signals; and

control means including a bus voltage sensor and a battery charge current sensor and operatively coupled to said duty cycle modulator means, to said charge power switch means and to said discharge power switch means for producing said modulator control feedback signals to control said duty cycle modulator means and for producing mode control gating signals actuating said charge mode of operation only when the bus voltage is above a predetermined value and actuating said discharge mode of operation only when said bus voltage is below said predetermined value.

2. In the system according to claim 1, wherein said bus voltage sensor provides a bus voltage signal and said battery current sensor provides a charge current signal, wherein said control means also includes a reference voltage source providing a reference voltage signal, and wherein said control means further includes voltage/current control means having voltage control amplifier means comparing at its input said bus voltage signal with said reference voltage signal to produce as part of said modulator control feedback signals a d.c. voltage control feedback signal, and also having summing circuit means comparing at its input said voltage control feedback signal with said chArge current signal to produce a composite feed-back signal, and further having current control amplifier means comparing at its input said reference voltage signal with said composite feedback signal to produce also as part of said modulator control feedback signals a d.c. current control feedback signal.

3. In the system according to claim 2, wherein said voltage control amplifier means and said current control amplifier means include respective voltage control and current control output circuitry wherein said voltage and current control feedback signals are joined at a junction but including isolation means for isolating said feedback signals from each other, said feedback signals being coupled to said duty cycle modulator means from said junction.

4. In the system according to claim 3, wherein said control means still further includes switching discriminator means comparing at its input said voltage control feedback signal with said reference voltage signal to produce said mode control gating signals, said mode control gating signals actuating said modes of operation in accordance with the magnitude of said voltage control feedback signal relative to said reference voltage signal.

5. In the system according to claim 4, wherein said switching discriminator means is operatively coupled to the outputs of said voltage control amplifier means and said current control amplifier means for allowing only said voltage control feedback signal to reach said duty cycle modulator means when said mode control gating signals actuate said discharge mode of operation and for allowing only said current control feedback signal to reach said duty cycle modulator means when said mode control gating signals actuate said charge mode of operation.

6. In the system according to claim 4, wherein said switching discriminator means includes a discriminator circuit responsive to said voltage control feedback signal and to said reference voltage signal to produce flip-flop control signals, and also includes a flip-flop type circuit with inputs coupled to said discriminator circuit and responsive to said flip-flop control signals, said flip-flop circuit producing at first and second output terminals said mode control gating signals in bi-level form, the level at said first of said output terminals relative to the opposite level at said second of said output terminals determining the mode of operation of said system.

7. In a system according to claim 6, wherein said switching discriminator includes an appropriately polarized diode arrangement coupled between said first of said output terminals and said voltage control output circuitry and between said second of said output terminals and said current control output circuitry to prevent said voltage control feedback signal from being coupled to said duty cycle modulator means only when the level of said mode control gating signal at said first output terminal is in a low state and to prevent said current control feedback signal from being coupled to said duty cycle modulator means only when the level of said mode control gating signal at said second output terminal is in a low state.

8. In the system according to claim 1, wherein said duty cycle modulator means includes a clock generator producing a clock signal, a ramp generator coupled to said clock generator and responsive to said clock signal to generate a clocked ramp signal, and a comparator circuit coupled to said ramp generator and to said control means and respectively responsive to said clocked ramp signal and to said modulator control feedback signal, said comparator circuit producing at its output terminal a duty cycle signal selectively coupled to said charge power switch means and said discharge power switch means in response to said mode control gating signals coupled to said respective switch means.

9. In the system according to claim 1, wherein said charge power switch means includes a current controlled chopper type switching regulator.

10. In the system according to claim 9, wherein said switching regulator includes an emitter-collector series connected transistor connected in series with a smoothing inductor and shunted to ground therebetween by an appropriately polarized diode, said duty cycle modulator means being operatively coupled to the base electrode of said transistor.

11. In the system according to claim 8, wherein said discharge power switch means includes an energy storage boost-add power conditioner means for boosting battery voltage to a regulated bus voltage.

12. In the system according to claim 1, wherein said control means also comprises battery condition sensor means having an input coupled to said battery and responsive to the voltage of said battery and having an output coupled to the output of said battery charge current sensor for causing said control means to linearly change said charging current inversely as the battery voltage approaches a predetermined fully charged level.