Solar array output regulator using variable light transmission

• US 5,289,998 A
• Filed: 10/15/1991
• Issued: 03/01/1994
• Est. Priority Date: 10/15/1991
• Status: Expired due to Fees

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: General Electric Company
• Inventors: Callen, Patrick J., Bingley, John D.
• Primary Examiner(s): Peters, Jr., Joseph F.
• Assistant Examiner(s): Ellis, Christopher P.
• Application Number:
  US07/776,028
• Time in Patent Office: 868 Days
• Field of Search: 323/906, 136/292, 136/293, 136/246, 244/169, 244/173, 244/158 R
• US Class Current: 244/172.7
• CPC Class Codes: B64G 1/428 Power distribution and management
• CPC Class Codes: B64G 1/443 Photovoltaic cell arrays
• CPC Class Codes: G02F 1/13318 Circuits comprising a photodetector
• CPC Class Codes: G05F 1/67 to the maximum power available from a generator, e.g. from solar cell
• CPC Class Codes: H02S 99/00 Subject matter not provided for in other groups of this subclass
• CPC Class Codes: Y02E 10/50 Photovoltaic [PV] energy
• CPC Class Codes: Y10S 136/292 Space - satellite
• CPC Class Codes: Y10S 136/293 Circuits
• CPC Class Codes: Y10S 323/906 Solar cell systems

Abstract

A solar cell voltage regulating arrangement which is particularly advantageous for use in spacecraft includes a light valve such as a liquid crystal cell disposed before the solar cell, to thereby controllably vary the light transmission to the solar cell. A control arrangement varies the transmission of the liquid crystal to control the output voltage.

Claims

1. A spacecraft comprising:

light activated voltage generating means including a light admitting aperture, and also including terminals at which a direct voltage is generated when light enters said aperture;

electrical utilization means coupled to said terminals;

a source of reference voltage;

amplifier means coupled to said terminals and to said source of reference voltage for generating an error signal representing the difference between said direct voltage and a desired voltage;

controllable light transmitting means located before said light admitting aperture, said controllable light transmitting means including electrical energization terminals, and being adapted, in a first electrical energization state, for allowing light to enter said light admitting aperture, and, in a second electrical energization state for preventing light from entering said light admitting aperture; and

feedback coupling means coupled to said amplifier means and to said electrical energization terminals of said controllable light transmitting means, for translating said error signal to said variable light transmitting means in a degenerative manner, to form a closed feedback loop which tends to maintain said direct voltage near said desired voltage.

2. A spacecraft according to claim 1, wherein said variable light transmitting means comprises a liquid crystal.

3. A spacecraft according to claim 2, wherein:

said amplifier means includes direct voltage differential amplifying means, whereby said error signal is a direct voltage; and

said feedback coupling means comprises switch means coupled to said amplifier means for chopping said direct voltage error signal to form an alternating voltage.

4. A light-to-electricity control system, comprising:

light activated voltage generating means including a light admitting aperture, and also including terminals at which a direct voltage is generated in response to light entering said aperture;

liquid crystal light transmission control means disposed before said light admitting aperture, said liquid crystal light transmission control means including electrical control terminals; and

feedback means coupled to said terminals of said voltage generating means and to said electrical control terminals of said light transmission control means for forming a degenerative feedback loop for control of said direct voltage.

5. A system according to claim 4, wherein said feedback means comprises a direct-voltage to variable-amplitude alternating voltage inverter.

6. A method for generating a controlled

direct voltage, comprising the steps of:

passing light through a variable-transmission liquid crystal control path to form controllably attenuated light;

applying said controllably attenuated light to a light-to-electric conversion device for generating a direct voltage which depends upon the amplitude of said controllably attenuated light;

generating a reference voltage;

comparing at least a portion of said direct voltage with said reference voltage to generate an error signal representative of the difference therebetween; and

applying said error signal to said variable-transmission liquid crystal for changing the transmissive properties of said control path in a degenerative feedback manner for control of said direct voltage.

7. A method according to claim 6, in which said step of applying said error signal includes the step of generating an alternating voltage, the amplitude of which varies in response to that of said error signal.

8. A method according to claim 7, wherein said step of generating an alternating voltage includes the step of generating said alternating voltage with a peak-to-peak amplitude which is proportional to said error signal.