Temperature compensated voltage regulator for photovoltaic charging systems

• US 4,349,775 A
• Filed: 01/02/1981
• Issued: 09/14/1982
• Est. Priority Date: 01/02/1981
• Status: Expired due to Term

• Current Assignee: Amoco/Enron Solar Co.
• Original Assignee: Exxon Research and Engineering Company (Exxon Mobil Corporation)
• Inventors: Kwon, Yiduk, Lawson, Paul
• Primary Examiner(s): HICKEY, ROBERT
• Application Number:
  US06/222,053
• Time in Patent Office: 620 Days
• Field of Search: 320/35, 320/36, 320/39, 320/40, 323/906, 323/907, 323/281
• US Class Current: 320/101
• CPC Class Codes: G05F 1/468 characterised by reference voltage circuitry, e.g. soft start, remote shutdown
• CPC Class Codes: H02J 7/007194 of the battery
• CPC Class Codes: H02J 7/35 with light sensitive cells
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers
• CPC Class Codes: Y10S 136/293 Circuits
• CPC Class Codes: Y10S 323/906 Solar cell systems
• CPC Class Codes: Y10S 323/907 Temperature compensation of semiconductor

Abstract

A voltage regulator for use in photovoltaic charging of storage batteries includes a temperature compensated reference voltage. The circuitry of the invention permits fixed temperature coefficient and variable temperature coefficient temperature compensated regulation.

The voltage regulator comprises an operational amplifier including a linearly temperature dependent current source coupled to an input terminal of said operational amplifier and a voltage source having a selectable voltage which is connected to another input of said operational amplifier, said reference voltage circuit being operable to provide a reference voltage about equal to a maximum charging voltage for said batteries;

a comparator for comparing said reference voltage with an output voltage of said photovoltaic array; and

a switch responsive to said comparator to inhibit charging whenever said array output exceeds said reference voltage.

Claims

1. A regulator system for controlling photovoltaic charging of primary batteries, said system comprising:

storage batteries having a room temperature full charge voltage V_normal, said voltage being temperature dependent;

a photovoltaic array having an output voltage capable of exceeding V_normal, said array being coupled to provide charging power to said batteries;

regulator means interposed between said array and said batteries, said regulator means including comparator means for comparing battery voltage to a reference voltage;

reference voltage means capable of providing a reference voltage about equal to the temperature dependent charge voltage V_normal, said reference means including an operational amplifier, arranged to provide biased current to voltage conversion, having a temperature dependent current source coupled to one input of said amplifier and a second voltage source having a predetermined voltage level coupled to a second input to said operational amplifier whereby said reference means provides a linearly temperature dependent reference voltage to said comparator means.

2. The regulator system of claim 1 wherein said temperature dependent current source is a linearly temperature dependent current source.

3. The regulator system of claim 2 wherein said linearly proportional current is about one microamp per degree K.

4. The regulator system of claim 1 wherein said batteries comprise lead acid storage batteries having a room temperature full charge voltage of about 2.3 volts/cell.

5. The regulator system of claim 1 wherein said reference voltage means further includes means for preselecting a value for room temperature normal full charge voltage, V_normal, and means for preselecting a voltage to temperature dependency.

6. A temperature compensated regulator for controlling a photovoltaic array charging of primary storage batteries, said regulator comprising:

reference voltage means having an operational amplifier including a linearly temperature dependent current source coupled to an input terminal of said operational amplifier and a voltage source having a selectable voltage which is connected to another input of said operational amplifier, said reference voltage means being operable to provide a reference voltage about equal to a maximum charging voltage for said batteries;

comparator means for comprising said reference voltage with an output voltage of said photovoltaic array; and

switching means, responsive to said comparator means to inhibit charging whenever said array output exceeds said reference voltage.